This is automake.info, produced by makeinfo version 6.8 from automake.texi. This manual is for GNU Automake (version 1.16.5, 1 October 2021), a program that creates GNU standards-compliant Makefiles from template files. Copyright © 1995–2021 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License.” INFO-DIR-SECTION Software development START-INFO-DIR-ENTRY * Automake: (automake). Making GNU standards-compliant Makefiles. END-INFO-DIR-ENTRY INFO-DIR-SECTION Individual utilities START-INFO-DIR-ENTRY * aclocal-invocation: (automake)aclocal Invocation. Generating aclocal.m4. * automake-invocation: (automake)automake Invocation. Generating Makefile.in. END-INFO-DIR-ENTRY  File: automake.info, Node: Top, Next: Introduction, Up: (dir) GNU Automake ************ This manual is for GNU Automake (version 1.16.5, 1 October 2021), a program that creates GNU standards-compliant Makefiles from template files. Copyright © 1995–2021 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License.” * Menu: * Introduction:: Automake’s purpose * Autotools Introduction:: An Introduction to the Autotools * Generalities:: General ideas * Examples:: Some example packages * automake Invocation:: Creating a Makefile.in * configure:: Scanning configure.ac, using aclocal * Directories:: Declaring subdirectories * Programs:: Building programs and libraries * Other Objects:: Other derived objects * Other GNU Tools:: Other GNU Tools * Documentation:: Building documentation * Install:: What gets installed * Clean:: What gets cleaned * Dist:: What goes in a distribution * Tests:: Support for test suites * Rebuilding:: Automatic rebuilding of Makefile * Options:: Changing Automake’s behavior * Miscellaneous:: Miscellaneous rules * Include:: Including extra files in an Automake template * Conditionals:: Conditionals * Silencing Make:: Obtain less verbose output from ‘make’ * Not Enough:: When Automake is not Enough * Distributing:: Distributing the Makefile.in * API Versioning:: About compatibility between Automake versions * Upgrading:: Upgrading to a Newer Automake Version * FAQ:: Frequently Asked Questions * Copying This Manual:: How to make copies of this manual * Indices:: Indices of variables, macros, and concepts — The Detailed Node Listing — An Introduction to the Autotools * GNU Build System:: Introducing the GNU Build System * Use Cases:: Use Cases for the GNU Build System * Why Autotools:: How Autotools Help * Hello World:: A Small Hello World Package Use Cases for the GNU Build System * Basic Installation:: Common installation procedure * Standard Targets:: A list of standard Makefile targets * Standard Directory Variables:: A list of standard directory variables * Standard Configuration Variables:: Using configuration variables * config.site:: Using a config.site file * VPATH Builds:: Parallel build trees * Two-Part Install:: Installing data and programs separately * Cross-Compilation:: Building for other architectures * Renaming:: Renaming programs at install time * DESTDIR:: Building binary packages with DESTDIR * Preparing Distributions:: Rolling out tarballs * Dependency Tracking:: Automatic dependency tracking * Nested Packages:: The GNU Build Systems can be nested A Small Hello World * Creating amhello:: Create ‘amhello-1.0.tar.gz’ from scratch * amhello's configure.ac Setup Explained:: * amhello's Makefile.am Setup Explained:: General ideas * General Operation:: General operation of Automake * Strictness:: Standards conformance checking * Uniform:: The Uniform Naming Scheme * Length Limitations:: Staying below the command line length limit * Canonicalization:: How derived variables are named * User Variables:: Variables reserved for the user * Auxiliary Programs:: Programs automake might require Some example packages * Complete:: A simple example, start to finish * true:: Building true and false Scanning ‘configure.ac’, using ‘aclocal’ * Requirements:: Configuration requirements * Optional:: Other things Automake recognizes * aclocal Invocation:: Auto-generating aclocal.m4 * Macros:: Autoconf macros supplied with Automake Auto-generating aclocal.m4 * aclocal Options:: Options supported by aclocal * Macro Search Path:: How aclocal finds .m4 files * Extending aclocal:: Writing your own aclocal macros * Local Macros:: Organizing local macros * Serials:: Serial lines in Autoconf macros * Future of aclocal:: aclocal’s scheduled death Autoconf macros supplied with Automake * Public Macros:: Macros that you can use. * Obsolete Macros:: Macros that will soon be removed. * Private Macros:: Macros that you should not use. Directories * Subdirectories:: Building subdirectories recursively * Conditional Subdirectories:: Conditionally not building directories * Alternative:: Subdirectories without recursion * Subpackages:: Nesting packages Conditional Subdirectories * SUBDIRS vs DIST_SUBDIRS:: Two sets of directories * Subdirectories with AM_CONDITIONAL:: Specifying conditional subdirectories * Subdirectories with AC_SUBST:: Another way for conditional recursion * Unconfigured Subdirectories:: Not even creating a ‘Makefile’ Building Programs and Libraries * A Program:: Building a program * A Library:: Building a library * A Shared Library:: Building a Libtool library * Program and Library Variables:: Variables controlling program and library builds * Default _SOURCES:: Default source files * LIBOBJS:: Special handling for LIBOBJS and ALLOCA * Program Variables:: Variables used when building a program * Yacc and Lex:: Yacc and Lex support * C++ Support:: Compiling C++ sources * Objective C Support:: Compiling Objective C sources * Objective C++ Support:: Compiling Objective C++ sources * Unified Parallel C Support:: Compiling Unified Parallel C sources * Assembly Support:: Compiling assembly sources * Fortran 77 Support:: Compiling Fortran 77 sources * Fortran 9x Support:: Compiling Fortran 9x sources * Java Support with gcj:: Compiling Java sources using gcj * Vala Support:: Compiling Vala sources * Support for Other Languages:: Compiling other languages * Dependencies:: Automatic dependency tracking * EXEEXT:: Support for executable extensions Building a program * Program Sources:: Defining program sources * Linking:: Linking with libraries or extra objects * Conditional Sources:: Handling conditional sources * Conditional Programs:: Building a program conditionally Building a Shared Library * Libtool Concept:: Introducing Libtool * Libtool Libraries:: Declaring Libtool Libraries * Conditional Libtool Libraries:: Building Libtool Libraries Conditionally * Conditional Libtool Sources:: Choosing Library Sources Conditionally * Libtool Convenience Libraries:: Building Convenience Libtool Libraries * Libtool Modules:: Building Libtool Modules * Libtool Flags:: Using _LIBADD, _LDFLAGS, and _LIBTOOLFLAGS * LTLIBOBJS:: Using $(LTLIBOBJS) and $(LTALLOCA) * Libtool Issues:: Common Issues Related to Libtool’s Use Common Issues Related to Libtool’s Use * Error required file ltmain.sh not found:: The need to run libtoolize * Objects created both with libtool and without:: Avoid a specific build race Yacc and Lex support * Linking Multiple Yacc Parsers:: Fortran 77 Support * Preprocessing Fortran 77:: Preprocessing Fortran 77 sources * Compiling Fortran 77 Files:: Compiling Fortran 77 sources * Mixing Fortran 77 With C and C++:: Mixing Fortran 77 With C and C++ Mixing Fortran 77 With C and C++ * How the Linker is Chosen:: Automatic linker selection Fortran 9x Support * Compiling Fortran 9x Files:: Compiling Fortran 9x sources Other Derived Objects * Scripts:: Executable scripts * Headers:: Header files * Data:: Architecture-independent data files * Sources:: Derived sources Built Sources * Built Sources Example:: Several ways to handle built sources. Other GNU Tools * Emacs Lisp:: Emacs Lisp * gettext:: Gettext * Libtool:: Libtool * Java:: Java bytecode compilation (deprecated) * Python:: Python Building documentation * Texinfo:: Texinfo * Man Pages:: Man pages What Gets Installed * Basics of Installation:: What gets installed where * The Two Parts of Install:: Installing data and programs separately * Extending Installation:: Adding your own rules for installation * Staged Installs:: Installation in a temporary location * Install Rules for the User:: Useful additional rules What Goes in a Distribution * Basics of Distribution:: Files distributed by default * Fine-grained Distribution Control:: ‘dist_’ and ‘nodist_’ prefixes * The dist Hook:: A target for last-minute distribution changes * Checking the Distribution:: ‘make distcheck’ explained * The Types of Distributions:: A variety of formats and compression methods Support for test suites * Generalities about Testing:: Concepts and terminology about testing * Simple Tests:: Listing test scripts in ‘TESTS’ * Custom Test Drivers:: Writing and using custom test drivers * Using the TAP test protocol:: Integrating test scripts that use the TAP protocol * DejaGnu Tests:: Interfacing with the ‘dejagnu’ testing framework * Install Tests:: Running tests on installed packages Simple Tests * Scripts-based Testsuites:: Automake-specific concepts and terminology * Serial Test Harness:: Older (and discouraged) serial test harness * Parallel Test Harness:: Generic concurrent test harness Scripts-based Testsuites * Testsuite Environment Overrides:: Custom Test Drivers * Overview of Custom Test Drivers Support:: * Declaring Custom Test Drivers:: * API for Custom Test Drivers:: API for Custom Test Drivers * Command-line arguments for test drivers:: * Log files generation and test results recording:: * Testsuite progress output:: Using the TAP test protocol * Introduction to TAP:: * Use TAP with the Automake test harness:: * Incompatibilities with other TAP parsers and drivers:: * Links and external resources on TAP:: Changing Automake’s Behavior * Options generalities:: Semantics of Automake option * List of Automake options:: A comprehensive list of Automake options Miscellaneous Rules * Tags:: Interfacing to cscope, etags and mkid * Suffixes:: Handling new file extensions Conditionals * Usage of Conditionals:: Declaring conditional content * Limits of Conditionals:: Enclosing complete statements Silencing ‘make’ * Make verbosity:: Make is verbose by default * Tricks For Silencing Make:: Standard and generic ways to silence make * Automake Silent Rules:: How Automake can help in silencing make When Automake Isn’t Enough * Extending:: Adding new rules or overriding existing ones. * Third-Party Makefiles:: Integrating Non-Automake ‘Makefile’s. Frequently Asked Questions about Automake * CVS:: CVS and generated files * maintainer-mode:: missing and AM_MAINTAINER_MODE * Wildcards:: Why doesn’t Automake support wildcards? * Limitations on File Names:: Limitations on source and installed file names * Errors with distclean:: Files left in build directory after distclean * Flag Variables Ordering:: CFLAGS vs. AM_CFLAGS vs. mumble_CFLAGS * Renamed Objects:: Why are object files sometimes renamed? * Per-Object Flags:: How to simulate per-object flags? * Multiple Outputs:: Writing rules for tools with many output files * Hard-Coded Install Paths:: Installing to hard-coded locations * Debugging Make Rules:: Strategies when things don’t work as expected * Reporting Bugs:: Feedback on bugs and feature requests Copying This Manual * GNU Free Documentation License:: License for copying this manual Indices * Macro Index:: Index of Autoconf macros * Variable Index:: Index of Makefile variables * General Index:: General index  File: automake.info, Node: Introduction, Next: Autotools Introduction, Prev: Top, Up: Top 1 Introduction ************** Automake is a tool for automatically generating ‘Makefile.in’s from files called ‘Makefile.am’. Each ‘Makefile.am’ is basically a series of ‘make’ variable definitions(1), with rules being thrown in occasionally. The generated ‘Makefile.in’s are compliant with the GNU Makefile standards. The GNU Makefile Standards Document (*note (standards)Makefile Conventions::) is long, complicated, and subject to change. The goal of Automake is to remove the burden of Makefile maintenance from the back of the individual GNU maintainer (and put it on the back of the Automake maintainers). The typical Automake input file is simply a series of variable definitions. Each such file is processed to create a ‘Makefile.in’. Automake does constrain a project in certain ways; for instance, it assumes that the project uses Autoconf (*note Introduction: (autoconf)Top.), and enforces certain restrictions on the ‘configure.ac’ contents. Automake requires ‘perl’ in order to generate the ‘Makefile.in’s. However, the distributions created by Automake are fully GNU standards-compliant, and do not require ‘perl’ in order to be built. For more information on bug reports, *Note Reporting Bugs::. ---------- Footnotes ---------- (1) These variables are also called “make macros” in Make terminology, however in this manual we reserve the term “macro” for Autoconf’s macros.  File: automake.info, Node: Autotools Introduction, Next: Generalities, Prev: Introduction, Up: Top 2 An Introduction to the Autotools ********************************** If you are new to Automake, maybe you know that it is part of a set of tools called _The Autotools_. Maybe you’ve already delved into a package full of files named ‘configure’, ‘configure.ac’, ‘Makefile.in’, ‘Makefile.am’, ‘aclocal.m4’, ..., some of them claiming to be _generated by_ Autoconf or Automake. But the exact purpose of these files and their relations is probably fuzzy. The goal of this chapter is to introduce you to this machinery, to show you how it works and how powerful it is. If you’ve never installed or seen such a package, do not worry: this chapter will walk you through it. If you need some teaching material, more illustrations, or a less ‘automake’-centered continuation, some slides for this introduction are available in Alexandre Duret-Lutz’s Autotools Tutorial (https://www.lrde.epita.fr/~adl/autotools.html). This chapter is the written version of the first part of his tutorial. * Menu: * GNU Build System:: Introducing the GNU Build System * Use Cases:: Use Cases for the GNU Build System * Why Autotools:: How Autotools Help * Hello World:: A Small Hello World Package  File: automake.info, Node: GNU Build System, Next: Use Cases, Up: Autotools Introduction 2.1 Introducing the GNU Build System ==================================== It is a truth universally acknowledged, that as a developer in possession of a new package, you must be in want of a build system. In the Unix world, such a build system is traditionally achieved using the command ‘make’ (*note Overview: (make)Top.). You express the recipe to build your package in a ‘Makefile’. This file is a set of rules to build the files in the package. For instance the program ‘prog’ may be built by running the linker on the files ‘main.o’, ‘foo.o’, and ‘bar.o’; the file ‘main.o’ may be built by running the compiler on ‘main.c’; etc. Each time ‘make’ is run, it reads ‘Makefile’, checks the existence and modification time of the files mentioned, decides what files need to be built (or rebuilt), and runs the associated commands. When a package needs to be built on a different platform than the one it was developed on, its ‘Makefile’ usually needs to be adjusted. For instance the compiler may have another name or require more options. In 1991, David J. MacKenzie got tired of customizing ‘Makefile’ for the 20 platforms he had to deal with. Instead, he handcrafted a little shell script called ‘configure’ to automatically adjust the ‘Makefile’ (*note Genesis: (autoconf)Genesis.). Compiling his package was now as simple as running ‘./configure && make’. Today this process has been standardized in the GNU project. The GNU Coding Standards (*note The Release Process: (standards)Managing Releases.) explains how each package of the GNU project should have a ‘configure’ script, and the minimal interface it should have. The ‘Makefile’ too should follow some established conventions. The result? A unified build system that makes all packages almost indistinguishable by the installer. In its simplest scenario, all the installer has to do is to unpack the package, run ‘./configure && make && make install’, and repeat with the next package to install. We call this build system the “GNU Build System”, since it was grown out of the GNU project. However it is used by a vast number of other packages: following any existing convention has its advantages. The Autotools are tools that will create a GNU Build System for your package. Autoconf mostly focuses on ‘configure’ and Automake on ‘Makefile’s. It is entirely possible to create a GNU Build System without the help of these tools. However it is rather burdensome and error-prone. We will discuss this again after some illustration of the GNU Build System in action.  File: automake.info, Node: Use Cases, Next: Why Autotools, Prev: GNU Build System, Up: Autotools Introduction 2.2 Use Cases for the GNU Build System ====================================== In this section we explore several use cases for the GNU Build System. You can replay all of these examples on the ‘amhello-1.0.tar.gz’ package distributed with Automake. If Automake is installed on your system, you should find a copy of this file in ‘PREFIX/share/doc/automake/amhello-1.0.tar.gz’, where PREFIX is the installation prefix specified during configuration (PREFIX defaults to ‘/usr/local’, however if Automake was installed by some GNU/Linux distribution it most likely has been set to ‘/usr’). If you do not have a copy of Automake installed, you can find a copy of this file inside the ‘doc/’ directory of the Automake package. Some of the following use cases present features that are in fact extensions to the GNU Build System. Read: they are not specified by the GNU Coding Standards, but they are nonetheless part of the build system created by the Autotools. To keep things simple, we do not point out the difference. Our objective is to show you many of the features that the build system created by the Autotools will offer to you. * Menu: * Basic Installation:: Common installation procedure * Standard Targets:: A list of standard Makefile targets * Standard Directory Variables:: A list of standard directory variables * Standard Configuration Variables:: Using configuration variables * config.site:: Using a config.site file * VPATH Builds:: Parallel build trees * Two-Part Install:: Installing data and programs separately * Cross-Compilation:: Building for other architectures * Renaming:: Renaming programs at install time * DESTDIR:: Building binary packages with DESTDIR * Preparing Distributions:: Rolling out tarballs * Dependency Tracking:: Automatic dependency tracking * Nested Packages:: The GNU Build Systems can be nested  File: automake.info, Node: Basic Installation, Next: Standard Targets, Up: Use Cases 2.2.1 Basic Installation ------------------------ The most common installation procedure looks as follows. ~ % tar zxf amhello-1.0.tar.gz ~ % cd amhello-1.0 ~/amhello-1.0 % ./configure ... config.status: creating Makefile config.status: creating src/Makefile ... ~/amhello-1.0 % make ... ~/amhello-1.0 % make check ... ~/amhello-1.0 % su Password: /home/adl/amhello-1.0 # make install ... /home/adl/amhello-1.0 # exit ~/amhello-1.0 % make installcheck ... The user first unpacks the package. Here, and in the following examples, we will use the non-portable ‘tar zxf’ command for simplicity. On a system without GNU ‘tar’ installed, this command should read ‘gunzip -c amhello-1.0.tar.gz | tar xf -’. The user then enters the newly created directory to run the ‘configure’ script. This script probes the system for various features, and finally creates the ‘Makefile’s. In this toy example there are only two ‘Makefile’s, but in real-world projects, there may be many more, usually one ‘Makefile’ per directory. It is now possible to run ‘make’. This will construct all the programs, libraries, and scripts that need to be constructed for the package. In our example, this compiles the ‘hello’ program. All files are constructed in place, in the source tree; we will see later how this can be changed. ‘make check’ causes the package’s tests to be run. This step is not mandatory, but it is often good to make sure the programs that have been built behave as they should, before you decide to install them. Our example does not contain any tests, so running ‘make check’ is a no-op. After everything has been built, and maybe tested, it is time to install it on the system. That means copying the programs, libraries, header files, scripts, and other data files from the source directory to their final destination on the system. The command ‘make install’ will do that. However, by default everything will be installed in subdirectories of ‘/usr/local’: binaries will go into ‘/usr/local/bin’, libraries will end up in ‘/usr/local/lib’, etc. This destination is usually not writable by any user, so we assume that we have to become root before we can run ‘make install’. In our example, running ‘make install’ will copy the program ‘hello’ into ‘/usr/local/bin’ and ‘README’ into ‘/usr/local/share/doc/amhello’. A last and optional step is to run ‘make installcheck’. This command may run tests on the installed files. ‘make check’ tests the files in the source tree, while ‘make installcheck’ tests their installed copies. The tests run by the latter can be different from those run by the former. For instance, there are tests that cannot be run in the source tree. Conversely, some packages are set up so that ‘make installcheck’ will run the very same tests as ‘make check’, only on different files (non-installed vs. installed). It can make a difference, for instance when the source tree’s layout is different from that of the installation. Furthermore it may help to diagnose an incomplete installation. Presently most packages do not have any ‘installcheck’ tests because the existence of ‘installcheck’ is little known, and its usefulness is neglected. Our little toy package is no better: ‘make installcheck’ does nothing.  File: automake.info, Node: Standard Targets, Next: Standard Directory Variables, Prev: Basic Installation, Up: Use Cases 2.2.2 Standard ‘Makefile’ Targets --------------------------------- So far we have come across four ways to run ‘make’ in the GNU Build System: ‘make’, ‘make check’, ‘make install’, and ‘make installcheck’. The words ‘check’, ‘install’, and ‘installcheck’, passed as arguments to ‘make’, are called “targets”. ‘make’ is a shorthand for ‘make all’, ‘all’ being the default target in the GNU Build System. Here is a list of the most useful targets that the GNU Coding Standards specify. ‘make all’ Build programs, libraries, documentation, etc. (same as ‘make’). ‘make install’ Install what needs to be installed, copying the files from the package’s tree to system-wide directories. ‘make install-strip’ Same as ‘make install’, then strip debugging symbols. Some users like to trade space for useful bug reports... ‘make uninstall’ The opposite of ‘make install’: erase the installed files. (This needs to be run from the same build tree that was installed.) ‘make clean’ Erase from the build tree the files built by ‘make all’. ‘make distclean’ Additionally erase anything ‘./configure’ created. ‘make check’ Run the test suite, if any. ‘make installcheck’ Check the installed programs or libraries, if supported. ‘make dist’ Recreate ‘PACKAGE-VERSION.tar.gz’ from all the source files.  File: automake.info, Node: Standard Directory Variables, Next: Standard Configuration Variables, Prev: Standard Targets, Up: Use Cases 2.2.3 Standard Directory Variables ---------------------------------- The GNU Coding Standards also specify a hierarchy of variables to denote installation directories. Some of these are: Directory variable Default value ------------------------------------------------------- ‘prefix’ ‘/usr/local’ ‘exec_prefix’ ‘${prefix}’ ‘bindir’ ‘${exec_prefix}/bin’ ‘libdir’ ‘${exec_prefix}/lib’ ... ‘includedir’ ‘${prefix}/include’ ‘datarootdir’ ‘${prefix}/share’ ‘datadir’ ‘${datarootdir}’ ‘mandir’ ‘${datarootdir}/man’ ‘infodir’ ‘${datarootdir}/info’ ‘docdir’ ‘${datarootdir}/doc/${PACKAGE}’ ... Each of these directories has a role which is often obvious from its name. In a package, any installable file will be installed in one of these directories. For instance in ‘amhello-1.0’, the program ‘hello’ is to be installed in BINDIR, the directory for binaries. The default value for this directory is ‘/usr/local/bin’, but the user can supply a different value when calling ‘configure’. Also the file ‘README’ will be installed into DOCDIR, which defaults to ‘/usr/local/share/doc/amhello’. As a user, if you wish to install a package on your own account, you could proceed as follows: ~/amhello-1.0 % ./configure --prefix ~/usr ... ~/amhello-1.0 % make ... ~/amhello-1.0 % make install ... This would install ‘~/usr/bin/hello’ and ‘~/usr/share/doc/amhello/README’. The list of all such directory options is shown by ‘./configure --help’.  File: automake.info, Node: Standard Configuration Variables, Next: config.site, Prev: Standard Directory Variables, Up: Use Cases 2.2.4 Standard Configuration Variables -------------------------------------- The GNU Coding Standards also define a set of standard configuration variables used during the build. Here are some: ‘CC’ C compiler command ‘CFLAGS’ C compiler flags ‘CXX’ C++ compiler command ‘CXXFLAGS’ C++ compiler flags ‘LDFLAGS’ linker flags ‘CPPFLAGS’ C/C++ preprocessor flags ... ‘configure’ usually does a good job at setting appropriate values for these variables, but there are cases where you may want to override them. For instance you may have several versions of a compiler installed and would like to use another one, you may have header files installed outside the default search path of the compiler, or even libraries out of the way of the linker. Here is how one would call ‘configure’ to force it to use ‘gcc-3’ as C compiler, use header files from ‘~/usr/include’ when compiling, and libraries from ‘~/usr/lib’ when linking. ~/amhello-1.0 % ./configure --prefix ~/usr CC=gcc-3 \ CPPFLAGS=-I$HOME/usr/include LDFLAGS=-L$HOME/usr/lib Again, a full list of these variables appears in the output of ‘./configure --help’.  File: automake.info, Node: config.site, Next: VPATH Builds, Prev: Standard Configuration Variables, Up: Use Cases 2.2.5 Overriding Default Configuration Setting with ‘config.site’ ----------------------------------------------------------------- When installing several packages using the same setup, it can be convenient to create a file to capture common settings. If a file named ‘PREFIX/share/config.site’ exists, ‘configure’ will source it at the beginning of its execution. Recall the command from the previous section: ~/amhello-1.0 % ./configure --prefix ~/usr CC=gcc-3 \ CPPFLAGS=-I$HOME/usr/include LDFLAGS=-L$HOME/usr/lib Assuming we are installing many package in ‘~/usr’, and will always want to use these definitions of ‘CC’, ‘CPPFLAGS’, and ‘LDFLAGS’, we can automate this by creating the following ‘~/usr/share/config.site’ file: test -z "$CC" && CC=gcc-3 test -z "$CPPFLAGS" && CPPFLAGS=-I$HOME/usr/include test -z "$LDFLAGS" && LDFLAGS=-L$HOME/usr/lib Now, any time a ‘configure’ script is using the ‘~/usr’ prefix, it will execute the above ‘config.site’ and define these three variables. ~/amhello-1.0 % ./configure --prefix ~/usr configure: loading site script /home/adl/usr/share/config.site ... *Note Setting Site Defaults: (autoconf)Site Defaults, for more information about this feature.  File: automake.info, Node: VPATH Builds, Next: Two-Part Install, Prev: config.site, Up: Use Cases 2.2.6 Parallel Build Trees (a.k.a. VPATH Builds) ------------------------------------------------ The GNU Build System distinguishes two trees: the source tree, and the build tree. These are two directories that may be the same, or different. The source tree is rooted in the directory containing the ‘configure’ script. It contains all the source files (those that are distributed), and may be arranged using several subdirectories. The build tree is rooted in the current directory at the time ‘configure’ was run, and is populated with all object files, programs, libraries, and other derived files built from the sources (and hence not distributed). The build tree usually has the same subdirectory layout as the source tree; its subdirectories are created automatically by the build system. If ‘configure’ is executed in its own directory, the source and build trees are combined: derived files are constructed in the same directories as their sources. This was the case in our first installation example (*note Basic Installation::). A common request from users is that they want to confine all derived files to a single directory, to keep their source directories uncluttered. Here is how we could run ‘configure’ to create everything in a build tree (that is, subdirectory) called ‘build/’. ~ % tar zxf ~/amhello-1.0.tar.gz ~ % cd amhello-1.0 ~/amhello-1.0 % mkdir build && cd build ~/amhello-1.0/build % ../configure ... ~/amhello-1.0/build % make ... These setups, where source and build trees are different, are often called “parallel builds” or “VPATH builds”. The expression _parallel build_ is misleading: the word _parallel_ is a reference to the way the build tree shadows the source tree, it is not about some concurrency in the way build commands are run. For this reason we refer to such setups using the name _VPATH builds_ in the following. _VPATH_ is the name of the ‘make’ feature used by the ‘Makefile’s to allow these builds (*note ‘VPATH’ Search Path for All Prerequisites: (make)General Search.). VPATH builds have other interesting uses. One is to build the same sources with multiple configurations. For instance: ~ % tar zxf ~/amhello-1.0.tar.gz ~ % cd amhello-1.0 ~/amhello-1.0 % mkdir debug optim && cd debug ~/amhello-1.0/debug % ../configure CFLAGS='-g -O0' ... ~/amhello-1.0/debug % make ... ~/amhello-1.0/debug % cd ../optim ~/amhello-1.0/optim % ../configure CFLAGS='-O3 -fomit-frame-pointer' ... ~/amhello-1.0/optim % make ... With network file systems, a similar approach can be used to build the same sources on different machines. For instance, suppose that the sources are installed on a directory shared by two hosts: ‘HOST1’ and ‘HOST2’, which may be different platforms. ~ % cd /nfs/src /nfs/src % tar zxf ~/amhello-1.0.tar.gz On the first host, you could create a local build directory: [HOST1] ~ % mkdir /tmp/amh && cd /tmp/amh [HOST1] /tmp/amh % /nfs/src/amhello-1.0/configure ... [HOST1] /tmp/amh % make && sudo make install ... (Here we assume that the installer has configured ‘sudo’ so it can execute ‘make install’ with root privileges; it is more convenient than using ‘su’ like in *note Basic Installation::). On the second host, you would do exactly the same, possibly at the same time: [HOST2] ~ % mkdir /tmp/amh && cd /tmp/amh [HOST2] /tmp/amh % /nfs/src/amhello-1.0/configure ... [HOST2] /tmp/amh % make && sudo make install ... In this scenario, nothing forbids the ‘/nfs/src/amhello-1.0’ directory from being read-only. In fact VPATH builds are also a means of building packages from a read-only medium such as a CD-ROM. (The FSF used to sell CD-ROMs with unpacked source code, before the GNU project grew so big.)  File: automake.info, Node: Two-Part Install, Next: Cross-Compilation, Prev: VPATH Builds, Up: Use Cases 2.2.7 Two-Part Installation --------------------------- In our last example (*note VPATH Builds::), a source tree was shared by two hosts, but compilation and installation were done separately on each host. The GNU Build System also supports networked setups where part of the installed files should be shared amongst multiple hosts. It does so by distinguishing architecture-dependent files from architecture-independent files, and providing two ‘Makefile’ targets to install each of these classes of files. These targets are ‘install-exec’ for architecture-dependent files and ‘install-data’ for architecture-independent files. The command we used up to now, ‘make install’, can be thought of as a shorthand for ‘make install-exec install-data’. From the GNU Build System point of view, the distinction between architecture-dependent files and architecture-independent files is based exclusively on the directory variable used to specify their installation destination. In the list of directory variables we provided earlier (*note Standard Directory Variables::), all the variables based on EXEC-PREFIX designate architecture-dependent directories whose files will be installed by ‘make install-exec’. The others designate architecture-independent directories and will serve files installed by ‘make install-data’. *Note The Two Parts of Install::, for more details. Here is how we could revisit our two-host installation example, assuming that (1) we want to install the package directly in ‘/usr’, and (2) the directory ‘/usr/share’ is shared by the two hosts. On the first host we would run [HOST1] ~ % mkdir /tmp/amh && cd /tmp/amh [HOST1] /tmp/amh % /nfs/src/amhello-1.0/configure --prefix /usr ... [HOST1] /tmp/amh % make && sudo make install ... On the second host, however, we need only install the architecture-specific files. [HOST2] ~ % mkdir /tmp/amh && cd /tmp/amh [HOST2] /tmp/amh % /nfs/src/amhello-1.0/configure --prefix /usr ... [HOST2] /tmp/amh % make && sudo make install-exec ... In packages that have installation checks, it would make sense to run ‘make installcheck’ (*note Basic Installation::) to verify that the package works correctly despite the apparent partial installation.  File: automake.info, Node: Cross-Compilation, Next: Renaming, Prev: Two-Part Install, Up: Use Cases 2.2.8 Cross-Compilation ----------------------- To “cross-compile” is to build on one platform a binary that will run on another platform. When speaking of cross-compilation, it is important to distinguish between the “build platform” on which the compilation is performed, and the “host platform” on which the resulting executable is expected to run. The following ‘configure’ options are used to specify each of them: ‘--build=BUILD’ The system on which the package is built. ‘--host=HOST’ The system where built programs and libraries will run. When the ‘--host’ is used, ‘configure’ will search for the cross-compiling suite for this platform. Cross-compilation tools commonly have their target architecture as prefix of their name. For instance my cross-compiler for MinGW32 has its binaries called ‘i586-mingw32msvc-gcc’, ‘i586-mingw32msvc-ld’, ‘i586-mingw32msvc-as’, etc. Here is how we could build ‘amhello-1.0’ for ‘i586-mingw32msvc’ on a GNU/Linux PC. ~/amhello-1.0 % ./configure --build i686-pc-linux-gnu --host i586-mingw32msvc checking for a BSD-compatible install... /usr/bin/install -c checking whether build environment is sane... yes checking for gawk... gawk checking whether make sets $(MAKE)... yes checking for i586-mingw32msvc-strip... i586-mingw32msvc-strip checking for i586-mingw32msvc-gcc... i586-mingw32msvc-gcc checking for C compiler default output file name... a.exe checking whether the C compiler works... yes checking whether we are cross compiling... yes checking for suffix of executables... .exe checking for suffix of object files... o checking whether we are using the GNU C compiler... yes checking whether i586-mingw32msvc-gcc accepts -g... yes checking for i586-mingw32msvc-gcc option to accept ANSI C... ... ~/amhello-1.0 % make ... ~/amhello-1.0 % cd src; file hello.exe hello.exe: MS Windows PE 32-bit Intel 80386 console executable not relocatable The ‘--host’ and ‘--build’ options are usually all we need for cross-compiling. The only exception is if the package being built is itself a cross-compiler: we need a third option to specify its target architecture. ‘--target=TARGET’ When building compiler tools: the system for which the tools will create output. For instance when installing GCC, the GNU Compiler Collection, we can use ‘--target=TARGET’ to specify that we want to build GCC as a cross-compiler for TARGET. Mixing ‘--build’ and ‘--target’, we can cross-compile a cross-compiler; such a three-way cross-compilation is known as a “Canadian cross”. *Note Specifying the System Type: (autoconf)Specifying Names, for more information about these ‘configure’ options.  File: automake.info, Node: Renaming, Next: DESTDIR, Prev: Cross-Compilation, Up: Use Cases 2.2.9 Renaming Programs at Install Time --------------------------------------- The GNU Build System provides means to automatically rename executables and manpages before they are installed (*note Man Pages::). This is especially convenient when installing a GNU package on a system that already has a proprietary implementation you do not want to overwrite. For instance, you may want to install GNU ‘tar’ as ‘gtar’ so you can distinguish it from your vendor’s ‘tar’. This can be done using one of these three ‘configure’ options. ‘--program-prefix=PREFIX’ Prepend PREFIX to installed program names. ‘--program-suffix=SUFFIX’ Append SUFFIX to installed program names. ‘--program-transform-name=PROGRAM’ Run ‘sed PROGRAM’ on installed program names. The following commands would install ‘hello’ as ‘/usr/local/bin/test-hello’, for instance. ~/amhello-1.0 % ./configure --program-prefix test- ... ~/amhello-1.0 % make ... ~/amhello-1.0 % sudo make install ...  File: automake.info, Node: DESTDIR, Next: Preparing Distributions, Prev: Renaming, Up: Use Cases 2.2.10 Building Binary Packages Using DESTDIR --------------------------------------------- The GNU Build System’s ‘make install’ and ‘make uninstall’ interface does not exactly fit the needs of a system administrator who has to deploy and upgrade packages on lots of hosts. In other words, the GNU Build System does not replace a package manager. Such package managers usually need to know which files have been installed by a package, so a mere ‘make install’ is inappropriate. The ‘DESTDIR’ variable can be used to perform a staged installation. The package should be configured as if it was going to be installed in its final location (e.g., ‘--prefix /usr’), but when running ‘make install’, the ‘DESTDIR’ should be set to the absolute name of a directory into which the installation will be diverted. From this directory it is easy to review which files are being installed where, and finally copy them to their final location by some means. For instance here is how we could create a binary package containing a snapshot of all the files to be installed. ~/amhello-1.0 % ./configure --prefix /usr ... ~/amhello-1.0 % make ... ~/amhello-1.0 % make DESTDIR=$HOME/inst install ... ~/amhello-1.0 % cd ~/inst ~/inst % find . -type f -print > ../files.lst ~/inst % tar zcvf ~/amhello-1.0-i686.tar.gz `cat ../files.lst` ./usr/bin/hello ./usr/share/doc/amhello/README After this example, ‘amhello-1.0-i686.tar.gz’ is ready to be uncompressed in ‘/’ on many hosts. (Using ‘`cat ../files.lst`’ instead of ‘.’ as argument for ‘tar’ avoids entries for each subdirectory in the archive: we would not like ‘tar’ to restore the modification time of ‘/’, ‘/usr/’, etc.) Note that when building packages for several architectures, it might be convenient to use ‘make install-data’ and ‘make install-exec’ (*note Two-Part Install::) to gather architecture-independent files in a single package. *Note Install::, for more information.  File: automake.info, Node: Preparing Distributions, Next: Dependency Tracking, Prev: DESTDIR, Up: Use Cases 2.2.11 Preparing Distributions ------------------------------ We have already mentioned ‘make dist’. This target collects all your source files and the necessary parts of the build system to create a tarball named ‘PACKAGE-VERSION.tar.gz’. Another, more useful command is ‘make distcheck’. The ‘distcheck’ target constructs ‘PACKAGE-VERSION.tar.gz’ just as well as ‘dist’, but it additionally ensures most of the use cases presented so far work: • It attempts a full compilation of the package (*note Basic Installation::): unpacking the newly constructed tarball, running ‘make’, ‘make dvi’, ‘make check’, ‘make install’, as well as ‘make installcheck’, and even ‘make dist’, • it tests VPATH builds with read-only source tree (*note VPATH Builds::), • it makes sure ‘make clean’, ‘make distclean’, and ‘make uninstall’ do not omit any file (*note Standard Targets::), • and it checks that ‘DESTDIR’ installations work (*note DESTDIR::). All of these actions are performed in a temporary directory, so that no root privileges are required. The exact location and the exact structure of such a subdirectory (where the extracted sources are placed, how the temporary build and install directories are named and how deeply they are nested, etc.) is to be considered an implementation detail, which can change at any time; so do not rely on it. Releasing a package that fails ‘make distcheck’ means that one of the scenarios we presented will not work and some users will be disappointed. Therefore it is a good practice to release a package only after a successful ‘make distcheck’. This of course does not imply that the package will be flawless, but at least it will prevent some of the embarrassing errors you may find in packages released by people who have never heard about ‘distcheck’ (like ‘DESTDIR’ not working because of a typo, or a distributed file being erased by ‘make clean’, or even ‘VPATH’ builds not working). *Note Creating amhello::, to recreate ‘amhello-1.0.tar.gz’ using ‘make distcheck’. *Note Checking the Distribution::, for more information about ‘distcheck’.  File: automake.info, Node: Dependency Tracking, Next: Nested Packages, Prev: Preparing Distributions, Up: Use Cases 2.2.12 Automatic Dependency Tracking ------------------------------------ Dependency tracking is performed as a side-effect of compilation. Each time the build system compiles a source file, it computes its list of dependencies (in C these are the header files included by the source being compiled). Later, any time ‘make’ is run and a dependency appears to have changed, the dependent files will be rebuilt. Automake generates code for automatic dependency tracking by default, unless the developer chooses to override it; for more information, *note Dependencies::. When ‘configure’ is executed, you can see it probing each compiler for the dependency mechanism it supports (several mechanisms can be used): ~/amhello-1.0 % ./configure --prefix /usr ... checking dependency style of gcc... gcc3 ... Because dependencies are only computed as a side-effect of the compilation, no dependency information exists the first time a package is built. This is OK because all the files need to be built anyway: ‘make’ does not have to decide which files need to be rebuilt. In fact, dependency tracking is completely useless for one-time builds and there is a ‘configure’ option to disable this: ‘--disable-dependency-tracking’ Speed up one-time builds. Some compilers do not offer any practical way to derive the list of dependencies as a side-effect of the compilation, requiring a separate run (maybe of another tool) to compute these dependencies. The performance penalty implied by these methods is important enough to disable them by default. The option ‘--enable-dependency-tracking’ must be passed to ‘configure’ to activate them. ‘--enable-dependency-tracking’ Do not reject slow dependency extractors. *Note Dependency Tracking Evolution: (automake-history)Dependency Tracking Evolution, for some discussion about the different dependency tracking schemes used by Automake over the years.  File: automake.info, Node: Nested Packages, Prev: Dependency Tracking, Up: Use Cases 2.2.13 Nested Packages ---------------------- Although nesting packages isn’t something we would recommend to someone who is discovering the Autotools, it is a nice feature worthy of mention in this small advertising tour. Autoconfiscated packages (that means packages whose build system have been created by Autoconf and friends) can be nested to arbitrary depth. A typical setup is that package A will distribute one of the libraries it needs in a subdirectory. This library B is a complete package with its own GNU Build System. The ‘configure’ script of A will run the ‘configure’ script of B as part of its execution; building and installing A will also build and install B. Generating a distribution for A will also include B. It is possible to gather several packages like this. GCC is a heavy user of this feature. This gives installers a single package to configure, build and install, while it allows developers to work on subpackages independently. When configuring nested packages, the ‘configure’ options given to the top-level ‘configure’ are passed recursively to nested ‘configure’s. A package that does not understand an option will ignore it, assuming it is meaningful to some other package. The command ‘configure --help=recursive’ can be used to display the options supported by all the included packages. *Note Subpackages::, for an example setup.  File: automake.info, Node: Why Autotools, Next: Hello World, Prev: Use Cases, Up: Autotools Introduction 2.3 How Autotools Help ====================== There are several reasons why you may not want to implement the GNU Build System yourself (read: write a ‘configure’ script and ‘Makefile’s yourself). • As we have seen, the GNU Build System has a lot of features (*note Use Cases::). Some users may expect features you have not implemented because you did not need them. • Implementing these features portably is difficult and exhausting. Think of writing portable shell scripts, and portable ‘Makefile’s, for systems you may not have handy. *Note Portable Shell Programming: (autoconf)Portable Shell, to convince yourself. • You will have to upgrade your setup to follow changes to the GNU Coding Standards. The GNU Autotools take all this burden off your back and provide: • Tools to create a portable, complete, and self-contained GNU Build System, from simple instructions. _Self-contained_ meaning the resulting build system does not require the GNU Autotools. • A central place where fixes and improvements are made: a bug-fix for a portability issue will benefit every package. Yet there also exist reasons why you may want NOT to use the Autotools... For instance you may be already using (or used to) another incompatible build system. Autotools will only be useful if you do accept the concepts of the GNU Build System. People who have their own idea of how a build system should work will feel frustrated by the Autotools.  File: automake.info, Node: Hello World, Prev: Why Autotools, Up: Autotools Introduction 2.4 A Small Hello World ======================= In this section we recreate the ‘amhello-1.0’ package from scratch. The first subsection shows how to call the Autotools to instantiate the GNU Build System, while the second explains the meaning of the ‘configure.ac’ and ‘Makefile.am’ files read by the Autotools. * Menu: * Creating amhello:: Create ‘amhello-1.0.tar.gz’ from scratch * amhello's configure.ac Setup Explained:: * amhello's Makefile.am Setup Explained::  File: automake.info, Node: Creating amhello, Next: amhello's configure.ac Setup Explained, Up: Hello World 2.4.1 Creating ‘amhello-1.0.tar.gz’ ----------------------------------- Here is how we can recreate ‘amhello-1.0.tar.gz’ from scratch. The package is simple enough so that we will only need to write 5 files. (You may copy them from the final ‘amhello-1.0.tar.gz’ that is distributed with Automake if you do not want to write them.) Create the following files in an empty directory. • ‘src/main.c’ is the source file for the ‘hello’ program. We store it in the ‘src/’ subdirectory, because later, when the package evolves, it will ease the addition of a ‘man/’ directory for man pages, a ‘data/’ directory for data files, etc. ~/amhello % cat src/main.c #include #include int main (void) { puts ("Hello World!"); puts ("This is " PACKAGE_STRING "."); return 0; } • ‘README’ contains some very limited documentation for our little package. ~/amhello % cat README This is a demonstration package for GNU Automake. Type 'info Automake' to read the Automake manual. • ‘Makefile.am’ and ‘src/Makefile.am’ contain Automake instructions for these two directories. ~/amhello % cat src/Makefile.am bin_PROGRAMS = hello hello_SOURCES = main.c ~/amhello % cat Makefile.am SUBDIRS = src dist_doc_DATA = README • Finally, ‘configure.ac’ contains Autoconf instructions to create the ‘configure’ script. ~/amhello % cat configure.ac AC_INIT([amhello], [1.0], [bug-automake@gnu.org]) AM_INIT_AUTOMAKE([-Wall -Werror foreign]) AC_PROG_CC AC_CONFIG_HEADERS([config.h]) AC_CONFIG_FILES([ Makefile src/Makefile ]) AC_OUTPUT Once you have these five files, it is time to run the Autotools to instantiate the build system. Do this using the ‘autoreconf’ command as follows: ~/amhello % autoreconf --install configure.ac: installing './install-sh' configure.ac: installing './missing' configure.ac: installing './compile' src/Makefile.am: installing './depcomp' At this point the build system is complete. In addition to the three scripts mentioned in its output, you can see that ‘autoreconf’ created four other files: ‘configure’, ‘config.h.in’, ‘Makefile.in’, and ‘src/Makefile.in’. The latter three files are templates that will be adapted to the system by ‘configure’ under the names ‘config.h’, ‘Makefile’, and ‘src/Makefile’. Let’s do this: ~/amhello % ./configure checking for a BSD-compatible install... /usr/bin/install -c checking whether build environment is sane... yes checking for gawk... no checking for mawk... mawk checking whether make sets $(MAKE)... yes checking for gcc... gcc checking for C compiler default output file name... a.out checking whether the C compiler works... yes checking whether we are cross compiling... no checking for suffix of executables... checking for suffix of object files... o checking whether we are using the GNU C compiler... yes checking whether gcc accepts -g... yes checking for gcc option to accept ISO C89... none needed checking for style of include used by make... GNU checking dependency style of gcc... gcc3 configure: creating ./config.status config.status: creating Makefile config.status: creating src/Makefile config.status: creating config.h config.status: executing depfiles commands You can see ‘Makefile’, ‘src/Makefile’, and ‘config.h’ being created at the end after ‘configure’ has probed the system. It is now possible to run all the targets we wish (*note Standard Targets::). For instance: ~/amhello % make ... ~/amhello % src/hello Hello World! This is amhello 1.0. ~/amhello % make distcheck ... ============================================= amhello-1.0 archives ready for distribution: amhello-1.0.tar.gz ============================================= Note that running ‘autoreconf’ is only needed initially when the GNU Build System does not exist. When you later change some instructions in a ‘Makefile.am’ or ‘configure.ac’, the relevant part of the build system will be regenerated automatically when you execute ‘make’. ‘autoreconf’ is a script that calls ‘autoconf’, ‘automake’, and a bunch of other commands in the right order. If you are beginning with these tools, it is not important to figure out in which order all of these tools should be invoked and why. However, because Autoconf and Automake have separate manuals, the important point to understand is that ‘autoconf’ is in charge of creating ‘configure’ from ‘configure.ac’, while ‘automake’ is in charge of creating ‘Makefile.in’s from ‘Makefile.am’s and ‘configure.ac’. This should at least direct you to the right manual when seeking answers.  File: automake.info, Node: amhello's configure.ac Setup Explained, Next: amhello's Makefile.am Setup Explained, Prev: Creating amhello, Up: Hello World 2.4.2 ‘amhello’’s ‘configure.ac’ Setup Explained ------------------------------------------------ Let us begin with the contents of ‘configure.ac’. AC_INIT([amhello], [1.0], [bug-automake@gnu.org]) AM_INIT_AUTOMAKE([-Wall -Werror foreign]) AC_PROG_CC AC_CONFIG_HEADERS([config.h]) AC_CONFIG_FILES([ Makefile src/Makefile ]) AC_OUTPUT This file is read by both ‘autoconf’ (to create ‘configure’) and ‘automake’ (to create the various ‘Makefile.in’s). It contains a series of M4 macros that will be expanded as shell code to finally form the ‘configure’ script. We will not elaborate on the syntax of this file, because the Autoconf manual has a whole section about it (*note Writing ‘configure.ac’: (autoconf)Writing Autoconf Input.). The macros prefixed with ‘AC_’ are Autoconf macros, documented in the Autoconf manual (*note Autoconf Macro Index: (autoconf)Autoconf Macro Index.). The macros that start with ‘AM_’ are Automake macros, documented later in this manual (*note Macro Index::). The first two lines of ‘configure.ac’ initialize Autoconf and Automake. ‘AC_INIT’ takes in as parameters the name of the package, its version number, and a contact address for bug-reports about the package (this address is output at the end of ‘./configure --help’, for instance). When adapting this setup to your own package, by all means please do not blindly copy Automake’s address: use the mailing list of your package, or your own mail address. The argument to ‘AM_INIT_AUTOMAKE’ is a list of options for ‘automake’ (*note Options::). ‘-Wall’ and ‘-Werror’ ask ‘automake’ to turn on all warnings and report them as errors. We are speaking of *Automake* warnings here, such as dubious instructions in ‘Makefile.am’. This has absolutely nothing to do with how the compiler will be called, even though it may support options with similar names. Using ‘-Wall -Werror’ is a safe setting when starting to work on a package: you do not want to miss any issues. Later you may decide to relax things a bit. The ‘foreign’ option tells Automake that this package will not follow the GNU Standards. GNU packages should always distribute additional files such as ‘ChangeLog’, ‘AUTHORS’, etc. We do not want ‘automake’ to complain about these missing files in our small example. The ‘AC_PROG_CC’ line causes the ‘configure’ script to search for a C compiler and define the variable ‘CC’ with its name. The ‘src/Makefile.in’ file generated by Automake uses the variable ‘CC’ to build ‘hello’, so when ‘configure’ creates ‘src/Makefile’ from ‘src/Makefile.in’, it will define ‘CC’ with the value it has found. If Automake is asked to create a ‘Makefile.in’ that uses ‘CC’ but ‘configure.ac’ does not define it, it will suggest you add a call to ‘AC_PROG_CC’. The ‘AC_CONFIG_HEADERS([config.h])’ invocation causes the ‘configure’ script to create a ‘config.h’ file gathering ‘#define’s defined by other macros in ‘configure.ac’. In our case, the ‘AC_INIT’ macro already defined a few of them. Here is an excerpt of ‘config.h’ after ‘configure’ has run: ... /* Define to the address where bug reports for this package should be sent. */ #define PACKAGE_BUGREPORT "bug-automake@gnu.org" /* Define to the full name and version of this package. */ #define PACKAGE_STRING "amhello 1.0" ... As you probably noticed, ‘src/main.c’ includes ‘config.h’ so it can use ‘PACKAGE_STRING’. In a real-world project, ‘config.h’ can grow quite large, with one ‘#define’ per feature probed on the system. The ‘AC_CONFIG_FILES’ macro declares the list of files that ‘configure’ should create from their ‘*.in’ templates. Automake also scans this list to find the ‘Makefile.am’ files it must process. (This is important to remember: when adding a new directory to your project, you should add its ‘Makefile’ to this list, otherwise Automake will never process the new ‘Makefile.am’ you wrote in that directory.) Finally, the ‘AC_OUTPUT’ line is a closing command that actually produces the part of the script in charge of creating the files registered with ‘AC_CONFIG_HEADERS’ and ‘AC_CONFIG_FILES’. When starting a new project, we suggest you start with such a simple ‘configure.ac’, and gradually add the other tests it requires. The command ‘autoscan’ can also suggest a few of the tests your package may need (*note Using ‘autoscan’ to Create ‘configure.ac’: (autoconf)autoscan Invocation.).  File: automake.info, Node: amhello's Makefile.am Setup Explained, Prev: amhello's configure.ac Setup Explained, Up: Hello World 2.4.3 ‘amhello’’s ‘Makefile.am’ Setup Explained ----------------------------------------------- We now turn to ‘src/Makefile.am’. This file contains Automake instructions to build and install ‘hello’. bin_PROGRAMS = hello hello_SOURCES = main.c A ‘Makefile.am’ has the same syntax as an ordinary ‘Makefile’. When ‘automake’ processes a ‘Makefile.am’ it copies the entire file into the output ‘Makefile.in’ (that will be later turned into ‘Makefile’ by ‘configure’) but will react to certain variable definitions by generating some build rules and other variables. Often ‘Makefile.am’s contain only a list of variable definitions as above, but they can also contain other variable and rule definitions that ‘automake’ will pass along without interpretation. Variables that end with ‘_PROGRAMS’ are special variables that list programs that the resulting ‘Makefile’ should build. In Automake speak, this ‘_PROGRAMS’ suffix is called a “primary”; Automake recognizes other primaries such as ‘_SCRIPTS’, ‘_DATA’, ‘_LIBRARIES’, etc. corresponding to different types of files. The ‘bin’ part of the ‘bin_PROGRAMS’ tells ‘automake’ that the resulting programs should be installed in BINDIR. Recall that the GNU Build System uses a set of variables to denote destination directories and allow users to customize these locations (*note Standard Directory Variables::). Any such directory variable can be put in front of a primary (omitting the ‘dir’ suffix) to tell ‘automake’ where to install the listed files. Programs need to be built from source files, so for each program ‘PROG’ listed in a ‘_PROGRAMS’ variable, ‘automake’ will look for another variable named ‘PROG_SOURCES’ listing its source files. There may be more than one source file: they will all be compiled and linked together. Automake also knows that source files need to be distributed when creating a tarball (unlike built programs). So a side-effect of this ‘hello_SOURCES’ declaration is that ‘main.c’ will be part of the tarball created by ‘make dist’. Finally here are some explanations regarding the top-level ‘Makefile.am’. SUBDIRS = src dist_doc_DATA = README ‘SUBDIRS’ is a special variable listing all directories that ‘make’ should recurse into before processing the current directory. So this line is responsible for ‘make’ building ‘src/hello’ even though we run it from the top-level. This line also causes ‘make install’ to install ‘src/hello’ before installing ‘README’ (not that this order matters). The line ‘dist_doc_DATA = README’ causes ‘README’ to be distributed and installed in DOCDIR. Files listed with the ‘_DATA’ primary are not automatically part of the tarball built with ‘make dist’, so we add the ‘dist_’ prefix so they get distributed. However, for ‘README’ it would not have been necessary: ‘automake’ automatically distributes any ‘README’ file it encounters (the list of other files automatically distributed is presented by ‘automake --help’). The only important effect of this second line is therefore to install ‘README’ during ‘make install’. One thing not covered in this example is accessing the installation directory values (*note Standard Directory Variables::) from your program code, that is, converting them into defined macros. For this, *note (autoconf)Defining Directories::.  File: automake.info, Node: Generalities, Next: Examples, Prev: Autotools Introduction, Up: Top 3 General ideas *************** The following sections cover a few basic ideas that will help you understand how Automake works. * Menu: * General Operation:: General operation of Automake * Strictness:: Standards conformance checking * Uniform:: The Uniform Naming Scheme * Length Limitations:: Staying below the command line length limit * Canonicalization:: How derived variables are named * User Variables:: Variables reserved for the user * Auxiliary Programs:: Programs automake might require  File: automake.info, Node: General Operation, Next: Strictness, Up: Generalities 3.1 General Operation ===================== Automake works by reading a ‘Makefile.am’ and generating a ‘Makefile.in’. Certain variables and rules defined in the ‘Makefile.am’ instruct Automake to generate more specialized code; for instance, a ‘bin_PROGRAMS’ variable definition will cause rules for compiling and linking programs to be generated. The variable definitions and rules in the ‘Makefile.am’ are copied mostly verbatim into the generated file, with all variable definitions preceding all rules. This allows you to add almost arbitrary code into the generated ‘Makefile.in’. For instance, the Automake distribution includes a non-standard rule for the ‘git-dist’ target, which the Automake maintainer uses to make distributions from the source control system. Note that most GNU Make extensions are not recognized by Automake. Using such extensions in a ‘Makefile.am’ will lead to errors or confusing behavior. A special exception is that the GNU Make append operator, ‘+=’, is supported. This operator appends its right hand argument to the variable specified on the left. Automake will translate the operator into an ordinary ‘=’ operator; ‘+=’ will thus work with any make program. Automake tries to keep comments grouped with any adjoining rules or variable definitions. Generally, Automake is not particularly smart in the parsing of unusual Makefile constructs, so you’re advised to avoid fancy constructs or “creative” use of whitespace. For example, characters cannot be used between a target name and the following “‘:’” character, and variable assignments shouldn’t be indented with characters. Also, using more complex macros in target names can cause trouble: % cat Makefile.am $(FOO:=x): bar % automake Makefile.am:1: bad characters in variable name '$(FOO' Makefile.am:1: ':='-style assignments are not portable A rule defined in ‘Makefile.am’ generally overrides any such rule of a similar name that would be automatically generated by ‘automake’. Although this is a supported feature, it is generally best to avoid making use of it, as sometimes the generated rules are very particular. Similarly, a variable defined in ‘Makefile.am’ or ‘AC_SUBST’ed from ‘configure.ac’ will override any definition of the variable that ‘automake’ would ordinarily create. This feature is often more useful than the ability to override a rule. Be warned that many of the variables generated by ‘automake’ are considered to be for internal use only, and their names might change in future releases. When examining a variable definition, Automake will recursively examine variables referenced in the definition. For example, if Automake is looking at the content of ‘foo_SOURCES’ in this snippet xs = a.c b.c foo_SOURCES = c.c $(xs) it would use the files ‘a.c’, ‘b.c’, and ‘c.c’ as the contents of ‘foo_SOURCES’. Automake also allows a form of comment that is _not_ copied into the output; all lines beginning with ‘##’ (leading spaces allowed) are completely ignored by Automake. It is customary to make the first line of ‘Makefile.am’ read: ## Process this file with automake to produce Makefile.in  File: automake.info, Node: Strictness, Next: Uniform, Prev: General Operation, Up: Generalities 3.2 Strictness ============== While Automake is intended to be used by maintainers of GNU packages, it does make some effort to accommodate those who wish to use it, but do not want to use all the GNU conventions. To this end, Automake supports three levels of “strictness”—how stringently Automake should enforce conformance with GNU conventions. Each strictness level can be selected using an option of the same name; see *note Options::. The strictness levels are: ‘gnu’ This is the default level of strictness. Automake will check for basic compliance with the GNU standards for software packaging. *Note (standards)Top::, for full details of these standards. Currently the following checks are made: • The files ‘INSTALL’, ‘NEWS’, ‘README’, ‘AUTHORS’, and ‘ChangeLog’, plus one of ‘COPYING.LIB’, ‘COPYING.LESSER’ or ‘COPYING’, are required at the topmost directory of the package. If the ‘--add-missing’ option is given, ‘automake’ will add a generic version of the ‘INSTALL’ file as well as the ‘COPYING’ file containing the text of the current version of the GNU General Public License existing at the time of this Automake release (version 3 as this is written, ). However, an existing ‘COPYING’ file will never be overwritten by ‘automake’. • The options ‘no-installman’ and ‘no-installinfo’ are prohibited. Future versions of Automake will add more checks at this level of strictness; it is advisable to be familiar with the precise requirements of the GNU standards. Future versions of Automake may, at this level of strictness, require certain non-standard GNU tools to be available to maintainer-only Makefile rules. For instance, in the future ‘pathchk’ (*note (coreutils)pathchk invocation::) may be required to run ‘make dist’. ‘foreign’ Automake will check for only those things that are absolutely required for proper operation. For instance, whereas GNU standards dictate the existence of a ‘NEWS’ file, it will not be required in this mode. This strictness will also turn off some warnings by default (among them, portability warnings). ‘gnits’ Automake will check for compliance to the as-yet-unwritten “Gnits standards”. These are based on the GNU standards, but are even more detailed. Unless you are a Gnits standards contributor, it is recommended that you avoid this option until such time as the Gnits standard is published (which is unlikely to ever happen). Currently, ‘--gnits’ does all the checks that ‘--gnu’ does, and checks the following as well: • ‘make installcheck’ will check to make sure that the ‘--help’ and ‘--version’ print a usage message and a version string, respectively. This is the ‘std-options’ option (*note Options::). • ‘make dist’ will check to make sure the ‘NEWS’ file has been updated to the current version. • ‘VERSION’ is checked to make sure its format complies with Gnits standards. • If ‘VERSION’ indicates that this is an alpha release, and the file ‘README-alpha’ appears in the topmost directory of a package, then it is included in the distribution. This is done in ‘--gnits’ mode, and no other, because this mode is the only one where version number formats are constrained, and hence the only mode where Automake can automatically determine whether ‘README-alpha’ should be included. • The file ‘THANKS’ is required.  File: automake.info, Node: Uniform, Next: Length Limitations, Prev: Strictness, Up: Generalities 3.3 The Uniform Naming Scheme ============================= Automake variables generally follow a “uniform naming scheme” that makes it easy to decide how programs (and other derived objects) are built, and how they are installed. This scheme also supports ‘configure’ time determination of what should be built. At ‘make’ time, certain variables are used to determine which objects are to be built. The variable names are made of several pieces that are concatenated together. The piece that tells ‘automake’ what is being built is commonly called the “primary”. For instance, the primary ‘PROGRAMS’ holds a list of programs that are to be compiled and linked. A different set of names is used to decide where the built objects should be installed. These names are prefixes to the primary, and they indicate which standard directory should be used as the installation directory. The standard directory names are given in the GNU standards (*note (standards)Directory Variables::). Automake extends this list with ‘pkgdatadir’, ‘pkgincludedir’, ‘pkglibdir’, and ‘pkglibexecdir’; these are the same as the non-‘pkg’ versions, but with ‘$(PACKAGE)’ appended. For instance, ‘pkglibdir’ is defined as ‘$(libdir)/$(PACKAGE)’. For each primary, there is one additional variable named by prepending ‘EXTRA_’ to the primary name. This variable is used to list objects that may or may not be built, depending on what ‘configure’ decides. This variable is required because Automake must statically know the entire list of objects that may be built in order to generate a ‘Makefile.in’ that will work in all cases. For instance, ‘cpio’ decides at configure time which programs should be built. Some of the programs are installed in ‘bindir’, and some are installed in ‘sbindir’: EXTRA_PROGRAMS = mt rmt bin_PROGRAMS = cpio pax sbin_PROGRAMS = $(MORE_PROGRAMS) Defining a primary without a prefix as a variable, e.g., ‘PROGRAMS’, is an error. Note that the common ‘dir’ suffix is left off when constructing the variable names; thus one writes ‘bin_PROGRAMS’ and not ‘bindir_PROGRAMS’. Not every sort of object can be installed in every directory. Automake will flag those attempts it finds in error (but see below how to override the check if you need to). Automake will also diagnose obvious misspellings in directory names. Sometimes the standard directories—even as augmented by Automake—are not enough. In particular it is sometimes useful, for clarity, to install objects in a subdirectory of some predefined directory. To this end, Automake allows you to extend the list of possible installation directories. A given prefix (e.g., ‘zar’) is valid if a variable of the same name with ‘dir’ appended is defined (e.g., ‘zardir’). For instance, the following snippet will install ‘file.xml’ into ‘$(datadir)/xml’. xmldir = $(datadir)/xml xml_DATA = file.xml This feature can also be used to override the sanity checks Automake performs to diagnose suspicious directory/primary couples (in the unlikely case that you need to omit these checks). For example, Automake would error out on this input: # Forbidden directory combinations, automake will error out on this. pkglib_PROGRAMS = foo doc_LIBRARIES = libquux.a but it will succeed with this: # Work around forbidden directory combinations. Do not use this # without a very good reason! my_execbindir = $(pkglibdir) my_doclibdir = $(docdir) my_execbin_PROGRAMS = foo my_doclib_LIBRARIES = libquux.a The ‘exec’ substring of the ‘my_execbindir’ variable lets the files be installed at the right time (*note The Two Parts of Install::). The special prefix ‘noinst_’ indicates that the objects in question should be built but not installed at all. This is usually used for objects required to build the rest of your package, for instance static libraries (*note A Library::), or helper scripts. The special prefix ‘check_’ indicates that the objects in question should not be built until the ‘make check’ command is run. Those objects are not installed either. The current primary names are ‘PROGRAMS’, ‘LIBRARIES’, ‘LTLIBRARIES’, ‘LISP’, ‘PYTHON’, ‘JAVA’, ‘SCRIPTS’, ‘DATA’, ‘HEADERS’, ‘MANS’, and ‘TEXINFOS’. Some primaries also allow additional prefixes that control other aspects of ‘automake’’s behavior. The currently defined prefixes are ‘dist_’, ‘nodist_’, ‘nobase_’, and ‘notrans_’. These prefixes are explained later (*note Program and Library Variables::) (*note Man Pages::).  File: automake.info, Node: Length Limitations, Next: Canonicalization, Prev: Uniform, Up: Generalities 3.4 Staying below the command line length limit =============================================== Traditionally, most unix-like systems have a length limitation for the command line arguments and environment contents when creating new processes (see for example for an overview on this issue), which of course also applies to commands spawned by ‘make’. POSIX requires this limit to be at least 4096 bytes, and most modern systems have quite high limits (or are unlimited). In order to create portable Makefiles that do not trip over these limits, it is necessary to keep the length of file lists bounded. Unfortunately, it is not possible to do so fully transparently within Automake, so your help may be needed. Typically, you can split long file lists manually and use different installation directory names for each list. For example, data_DATA = file1 ... fileN fileN+1 ... file2N may also be written as data_DATA = file1 ... fileN data2dir = $(datadir) data2_DATA = fileN+1 ... file2N and will cause Automake to treat the two lists separately during ‘make install’. See *note The Two Parts of Install:: for choosing directory names that will keep the ordering of the two parts of installation Note that ‘make dist’ may still only work on a host with a higher length limit in this example. Automake itself employs a couple of strategies to avoid long command lines. For example, when ‘${srcdir}/’ is prepended to file names, as can happen with above ‘$(data_DATA)’ lists, it limits the amount of arguments passed to external commands. Unfortunately, some systems’ ‘make’ commands may prepend ‘VPATH’ prefixes like ‘${srcdir}/’ to file names from the source tree automatically (*note Automatic Rule Rewriting: (autoconf)Automatic Rule Rewriting.). In this case, the user may have to switch to use GNU Make, or refrain from using VPATH builds, in order to stay below the length limit. For libraries and programs built from many sources, convenience archives may be used as intermediates in order to limit the object list length (*note Libtool Convenience Libraries::).  File: automake.info, Node: Canonicalization, Next: User Variables, Prev: Length Limitations, Up: Generalities 3.5 How derived variables are named =================================== Sometimes a Makefile variable name is derived from some text the maintainer supplies. For instance, a program name listed in ‘_PROGRAMS’ is rewritten into the name of a ‘_SOURCES’ variable. In cases like this, Automake canonicalizes the text, so that program names and the like do not have to follow Makefile variable naming rules. All characters in the name except for letters, numbers, the strudel (@), and the underscore are turned into underscores when making variable references. For example, if your program is named ‘sniff-glue’, the derived variable name would be ‘sniff_glue_SOURCES’, not ‘sniff-glue_SOURCES’. Similarly the sources for a library named ‘libmumble++.a’ should be listed in the ‘libmumble___a_SOURCES’ variable. The strudel is an addition, to make the use of Autoconf substitutions in variable names less obfuscating.  File: automake.info, Node: User Variables, Next: Auxiliary Programs, Prev: Canonicalization, Up: Generalities 3.6 Variables reserved for the user =================================== Some ‘Makefile’ variables are reserved by the GNU Coding Standards for the use of the “user”—the person building the package. For instance, ‘CFLAGS’ is one such variable. Sometimes package developers are tempted to set user variables such as ‘CFLAGS’ because it appears to make their job easier. However, the package itself should never set a user variable, particularly not to include switches that are required for proper compilation of the package. Since these variables are documented as being for the package builder, that person rightfully expects to be able to override any of these variables at build time. To get around this problem, Automake introduces an automake-specific shadow variable for each user flag variable. (Shadow variables are not introduced for variables like ‘CC’, where they would make no sense.) The shadow variable is named by prepending ‘AM_’ to the user variable’s name. For instance, the shadow variable for ‘YFLAGS’ is ‘AM_YFLAGS’. The package maintainer—that is, the author(s) of the ‘Makefile.am’ and ‘configure.ac’ files—may adjust these shadow variables however necessary. *Note Flag Variables Ordering::, for more discussion about these variables and how they interact with per-target variables.  File: automake.info, Node: Auxiliary Programs, Prev: User Variables, Up: Generalities 3.7 Programs automake might require =================================== Automake sometimes requires helper programs so that the generated ‘Makefile’ can do its work properly. There are a fairly large number of them, and we list them here. Although all of these files are distributed and installed with Automake, a couple of them are maintained separately. The Automake copies are updated before each release, but we mention the original source in case you need more recent versions. ‘ar-lib’ This is a wrapper primarily for the Microsoft lib archiver, to make it more POSIX-like. ‘compile’ This is a wrapper for compilers that do not accept options ‘-c’ and ‘-o’ at the same time. It is only used when absolutely required. Such compilers are rare, with the Microsoft C/C++ Compiler as the most notable exception. This wrapper also makes the following common options available for that compiler, while performing file name translation where needed: ‘-I’, ‘-L’, ‘-l’, ‘-Wl,’ and ‘-Xlinker’. ‘config.guess’ ‘config.sub’ These two programs compute the canonical triplets for the given build, host, or target architecture. These programs are updated regularly to support new architectures and fix probes broken by changes in new kernel versions. Each new release of Automake comes with up-to-date copies of these programs. If your copy of Automake is getting old, you are encouraged to fetch the latest versions of these files from before making a release. ‘depcomp’ This program understands how to run a compiler so that it will generate not only the desired output but also dependency information that is then used by the automatic dependency tracking feature (*note Dependencies::). ‘install-sh’ This is a replacement for the ‘install’ program that works on platforms where ‘install’ is unavailable or unusable. ‘mdate-sh’ This script is used to generate a ‘version.texi’ file. It examines a file and prints some date information about it. ‘missing’ This wraps a number of programs that are typically only required by maintainers. If the program in question doesn’t exist, or seems too old, ‘missing’ will print an informative warning before failing out, to provide the user with more context and information. ‘mkinstalldirs’ This script used to be a wrapper around ‘mkdir -p’, which is not portable. Now we prefer to use ‘install-sh -d’ when ‘configure’ finds that ‘mkdir -p’ does not work, this makes one less script to distribute. For backward compatibility ‘mkinstalldirs’ is still used and distributed when ‘automake’ finds it in a package. But it is no longer installed automatically, and it should be safe to remove it. ‘py-compile’ This is used to byte-compile Python scripts. ‘test-driver’ This implements the default test driver offered by the parallel testsuite harness. ‘texinfo.tex’ When Texinfo sources are in the package, this file is required for ‘make dvi’, ‘make ps’ and ‘make pdf’. The latest version can be downloaded from . A working TeX distribution, or at least a ‘tex’ program, is also required. Furthermore, ‘make dist’ invokes ‘make dvi’, so these become requirements for making a distribution with Texinfo sources. ‘ylwrap’ This program wraps ‘lex’ and ‘yacc’ to rename their output files. It also ensures that, for instance, multiple ‘yacc’ instances can be invoked in a single directory in parallel.  File: automake.info, Node: Examples, Next: automake Invocation, Prev: Generalities, Up: Top 4 Some example packages *********************** This section contains two small examples. The first example (*note Complete::) assumes you have an existing project already using Autoconf, with handcrafted ‘Makefile’s, and that you want to convert it to using Automake. If you are discovering both tools, it is probably better that you look at the Hello World example presented earlier (*note Hello World::). The second example (*note true::) shows how two programs can be built from the same file, using different compilation parameters. It contains some technical digressions that are probably best skipped on first read. * Menu: * Complete:: A simple example, start to finish * true:: Building true and false  File: automake.info, Node: Complete, Next: true, Up: Examples 4.1 A simple example, start to finish ===================================== Let’s suppose you just finished writing ‘zardoz’, a program to make your head float from vortex to vortex. You’ve been using Autoconf to provide a portability framework, but your ‘Makefile.in’s have been ad-hoc. You want to make them bulletproof, so you turn to Automake. The first step is to update your ‘configure.ac’ to include the commands that ‘automake’ needs. The way to do this is to add an ‘AM_INIT_AUTOMAKE’ call just after ‘AC_INIT’: AC_INIT([zardoz], [1.0]) AM_INIT_AUTOMAKE ... Since your program doesn’t have any complicating factors (e.g., it doesn’t use ‘gettext’, it doesn’t want to build a shared library), you’re done with this part. That was easy! Now you must regenerate ‘configure’. But to do that, you’ll need to tell ‘autoconf’ how to find the new macro you’ve used. The easiest way to do this is to use the ‘aclocal’ program to generate your ‘aclocal.m4’ for you. But wait... maybe you already have an ‘aclocal.m4’, because you had to write some hairy macros for your program. The ‘aclocal’ program lets you put your own macros into ‘acinclude.m4’, so simply rename and then run: mv aclocal.m4 acinclude.m4 aclocal autoconf Now it is time to write your ‘Makefile.am’ for ‘zardoz’. Since ‘zardoz’ is a user program, you want to install it where the rest of the user programs go: ‘bindir’. Additionally, ‘zardoz’ has some Texinfo documentation. Your ‘configure.ac’ script uses ‘AC_REPLACE_FUNCS’, so you need to link against ‘$(LIBOBJS)’. So here’s what you’d write: bin_PROGRAMS = zardoz zardoz_SOURCES = main.c head.c float.c vortex9.c gun.c zardoz_LDADD = $(LIBOBJS) info_TEXINFOS = zardoz.texi Now you can run ‘automake --add-missing’ to generate your ‘Makefile.in’ and grab any auxiliary files you might need, and you’re done!  File: automake.info, Node: true, Prev: Complete, Up: Examples 4.2 Building true and false =========================== Here is another, trickier example. It shows how to generate two programs (‘true’ and ‘false’) from the same source file (‘true.c’). The difficult part is that each compilation of ‘true.c’ requires different ‘cpp’ flags. bin_PROGRAMS = true false false_SOURCES = false_LDADD = false.o true.o: true.c $(COMPILE) -DEXIT_CODE=0 -c true.c false.o: true.c $(COMPILE) -DEXIT_CODE=1 -o false.o -c true.c Note that there is no ‘true_SOURCES’ definition. Automake will implicitly assume that there is a source file named ‘true.c’ (*note Default _SOURCES::), and define rules to compile ‘true.o’ and link ‘true’. The ‘true.o: true.c’ rule supplied by the above ‘Makefile.am’, will override the Automake generated rule to build ‘true.o’. ‘false_SOURCES’ is defined to be empty—that way no implicit value is substituted. Because we have not listed the source of ‘false’, we have to tell Automake how to link the program. This is the purpose of the ‘false_LDADD’ line. A ‘false_DEPENDENCIES’ variable, holding the dependencies of the ‘false’ target will be automatically generated by Automake from the content of ‘false_LDADD’. The above rules won’t work if your compiler doesn’t accept both ‘-c’ and ‘-o’. The simplest fix for this is to introduce a bogus dependency (to avoid problems with a parallel ‘make’): true.o: true.c false.o $(COMPILE) -DEXIT_CODE=0 -c true.c false.o: true.c $(COMPILE) -DEXIT_CODE=1 -c true.c && mv true.o false.o As it turns out, there is also a much easier way to do this same task. Some of the above technique is useful enough that we’ve kept the example in the manual. However if you were to build ‘true’ and ‘false’ in real life, you would probably use per-program compilation flags, like so: bin_PROGRAMS = false true false_SOURCES = true.c false_CPPFLAGS = -DEXIT_CODE=1 true_SOURCES = true.c true_CPPFLAGS = -DEXIT_CODE=0 In this case Automake will cause ‘true.c’ to be compiled twice, with different flags. In this instance, the names of the object files would be chosen by automake; they would be ‘false-true.o’ and ‘true-true.o’. (The name of the object files rarely matters.)  File: automake.info, Node: automake Invocation, Next: configure, Prev: Examples, Up: Top 5 Creating a ‘Makefile.in’ ************************** To create all the ‘Makefile.in’s for a package, run the ‘automake’ program in the top level directory, with no arguments. ‘automake’ will automatically find each appropriate ‘Makefile.am’ (by scanning ‘configure.ac’; *note configure::) and generate the corresponding ‘Makefile.in’. Note that ‘automake’ has a rather simplistic view of what constitutes a package; it assumes that a package has only one ‘configure.ac’, at the top. If your package has multiple ‘configure.ac’s, then you must run ‘automake’ in each directory holding a ‘configure.ac’. (Alternatively, you may rely on Autoconf’s ‘autoreconf’, which is able to recurse your package tree and run ‘automake’ where appropriate.) You can optionally give ‘automake’ an argument; ‘.am’ is appended to the argument and the result is used as the name of the input file. This feature is generally only used to automatically rebuild an out-of-date ‘Makefile.in’. Note that ‘automake’ must always be run from the topmost directory of a project, even if being used to regenerate the ‘Makefile.in’ in some subdirectory. This is necessary because ‘automake’ must scan ‘configure.ac’, and because ‘automake’ uses the knowledge that a ‘Makefile.in’ is in a subdirectory to change its behavior in some cases. Automake will run ‘autoconf’ to scan ‘configure.ac’ and its dependencies (i.e., ‘aclocal.m4’ and any included file), therefore ‘autoconf’ must be in your ‘PATH’. If there is an ‘AUTOCONF’ variable in your environment it will be used instead of ‘autoconf’; this allows you to select a particular version of Autoconf. By the way, don’t misunderstand this paragraph: ‘automake’ runs ‘autoconf’ to *scan* your ‘configure.ac’; this won’t build ‘configure’ and you still have to run ‘autoconf’ yourself for this purpose. ‘automake’ accepts the following options: ‘-a’ ‘--add-missing’ Automake requires certain common files to exist in certain situations; for instance, ‘config.guess’ is required if ‘configure.ac’ invokes ‘AC_CANONICAL_HOST’. Automake is distributed with several of these files (*note Auxiliary Programs::); this option will cause the missing ones to be automatically added to the package, whenever possible. In general if Automake tells you a file is missing, try using this option. By default Automake tries to make a symbolic link pointing to its own copy of the missing file; this can be changed with ‘--copy’. Many of the potentially-missing files are common scripts whose location may be specified via the ‘AC_CONFIG_AUX_DIR’ macro. Therefore, ‘AC_CONFIG_AUX_DIR’’s setting affects whether a file is considered missing, and where the missing file is added (*note Optional::). In some strictness modes, additional files are installed, see *note Gnits:: for more information. ‘--libdir=DIR’ Look for Automake data files in directory DIR instead of in the installation directory. This is typically used for debugging. The environment variable ‘AUTOMAKE_LIBDIR’ provides another way to set the directory containing Automake data files. However ‘--libdir’ takes precedence over it. ‘--print-libdir’ Print the path of the installation directory containing Automake-provided scripts and data files (e.g., ‘texinfo.texi’ and ‘install-sh’). ‘-c’ ‘--copy’ When used with ‘--add-missing’, causes installed files to be copied. The default is to make a symbolic link. ‘-f’ ‘--force-missing’ When used with ‘--add-missing’, causes standard files to be reinstalled even if they already exist in the source tree. This involves removing the file from the source tree before creating the new symlink (or, with ‘--copy’, copying the new file). ‘--foreign’ Set the global strictness to ‘foreign’. For more information, see *note Strictness::. ‘--gnits’ Set the global strictness to ‘gnits’. For more information, see *note Strictness::. ‘--gnu’ Set the global strictness to ‘gnu’. For more information, see *note Strictness::. This is the default strictness. ‘--help’ Print a summary of the command line options and exit. ‘-i’ ‘--ignore-deps’ This disables the dependency tracking feature in generated ‘Makefile’s; see *note Dependencies::. ‘--include-deps’ This enables the dependency tracking feature. This feature is enabled by default. This option is provided for historical reasons only and probably should not be used. ‘--no-force’ Ordinarily ‘automake’ creates all ‘Makefile.in’s mentioned in ‘configure.ac’. This option causes it to only update those ‘Makefile.in’s that are out of date with respect to one of their dependents. ‘-o DIR’ ‘--output-dir=DIR’ Put the generated ‘Makefile.in’ in the directory DIR. Ordinarily each ‘Makefile.in’ is created in the directory of the corresponding ‘Makefile.am’. This option is deprecated and will be removed in a future release. ‘-v’ ‘--verbose’ Cause Automake to print information about which files are being read or created. ‘--version’ Print the version number of Automake and exit. ‘-W CATEGORY[,CATEGORY...]’ ‘--warnings=CATEGORY[,CATEGORY...]’ Output warnings about a CATEGORY of potential problems with the package. CATEGORY can be any of: ‘cross’ Constructs compromising the ability to cross-compile the package. ‘gnu’ Minor deviations from the GNU Coding Standards (*note (standards)Top::). ‘obsolete’ Obsolete features or constructions. ‘override’ Redefinitions of Automake rules or variables. ‘portability’ Portability issues (e.g., use of ‘make’ features that are known to be not portable). ‘portability-recursive’ Recursive, or nested, Make variable expansions (‘$(foo$(x))’). These are not universally supported, but are more portable than the other non-portable constructs diagnosed by ‘-Wportability’. These warnings are turned on by ‘-Wportability’ but can then be turned off specifically by ‘-Wno-portability-recursive’. ‘extra-portability’ Extra portability issues, related to rarely-used tools such as the Microsoft ‘lib’ archiver. ‘syntax’ Questionable syntax, unused variables, typos, etc. ‘unsupported’ Unsupported or incomplete features. ‘all’ Turn on all the above categories of warnings. ‘none’ Turn off all the above categories of warnings. ‘error’ Treat warnings as errors. A category can be turned off by prefixing its name with ‘no-’. For instance, ‘-Wno-syntax’ will hide the warnings about unused variables. Warnings in the ‘gnu’, ‘obsolete’, ‘portability’, ‘syntax’, and ‘unsupported’ categories are turned on by default. The ‘gnu’ and ‘portability’ categories are turned off in ‘--foreign’ strictness. Turning off ‘portability’ will also turn off ‘extra-portability’, and similarly turning on ‘extra-portability’ will also turn on ‘portability’. However, turning on ‘portability’ or turning off ‘extra-portability’ will not affect the other category. Unknown warning categories supplied as an argument to ‘-W’ will themselves produce a warning, in the ‘unsupported’ category. This warning is never treated as an error. The environment variable ‘WARNINGS’ can contain a comma separated list of categories to enable. ‘-W’ settings on the command line take precedence; for instance, ‘-Wnone’ also turns off any warning categories enabled by ‘WARNINGS’. Unknown warning categories named in ‘WARNINGS’ are silently ignored. If the environment variable ‘AUTOMAKE_JOBS’ contains a positive number, it is taken as the maximum number of Perl threads to use in ‘automake’ for generating multiple ‘Makefile.in’ files concurrently. This is an experimental feature.  File: automake.info, Node: configure, Next: Directories, Prev: automake Invocation, Up: Top 6 Scanning ‘configure.ac’, using ‘aclocal’ ****************************************** Automake scans the package’s ‘configure.ac’ to determine certain information about the package. Some ‘autoconf’ macros are required and some variables must be defined in ‘configure.ac’. Automake will also use information from ‘configure.ac’ to further tailor its output. Automake also supplies some Autoconf macros to make the maintenance easier. These macros can automatically be put into your ‘aclocal.m4’ using the ‘aclocal’ program. * Menu: * Requirements:: Configuration requirements * Optional:: Other things Automake recognizes * aclocal Invocation:: Auto-generating aclocal.m4 * Macros:: Autoconf macros supplied with Automake  File: automake.info, Node: Requirements, Next: Optional, Up: configure 6.1 Configuration requirements ============================== The one real requirement of Automake is that your ‘configure.ac’ call ‘AM_INIT_AUTOMAKE’. This macro does several things that are required for proper Automake operation (*note Macros::). Here are the other macros that Automake requires but which are not run by ‘AM_INIT_AUTOMAKE’: ‘AC_CONFIG_FILES’ ‘AC_OUTPUT’ These two macros are usually invoked as follows near the end of ‘configure.ac’. ... AC_CONFIG_FILES([ Makefile doc/Makefile src/Makefile src/lib/Makefile ... ]) AC_OUTPUT Automake uses these to determine which files to create (*note Creating Output Files: (autoconf)Output.). A listed file is considered to be an Automake generated ‘Makefile’ if there exists a file with the same name and the ‘.am’ extension appended. Typically, ‘AC_CONFIG_FILES([foo/Makefile])’ will cause Automake to generate ‘foo/Makefile.in’ if ‘foo/Makefile.am’ exists. When using ‘AC_CONFIG_FILES’ with multiple input files, as in AC_CONFIG_FILES([Makefile:top.in:Makefile.in:bot.in]) ‘automake’ will generate the first ‘.in’ input file for which a ‘.am’ file exists. If no such file exists the output file is not considered to be generated by Automake. Files created by ‘AC_CONFIG_FILES’, be they Automake ‘Makefile’s or not, are all removed by ‘make distclean’. Their inputs are automatically distributed, unless they are the output of prior ‘AC_CONFIG_FILES’ commands. Finally, rebuild rules are generated in the Automake ‘Makefile’ existing in the subdirectory of the output file, if there is one, or in the top-level ‘Makefile’ otherwise. The above machinery (cleaning, distributing, and rebuilding) works fine if the ‘AC_CONFIG_FILES’ specifications contain only literals. If part of the specification uses shell variables, ‘automake’ will not be able to fulfill this setup, and you will have to complete the missing bits by hand. For instance, on file=input ... AC_CONFIG_FILES([output:$file],, [file=$file]) ‘automake’ will output rules to clean ‘output’, and rebuild it. However the rebuild rule will not depend on ‘input’, and this file will not be distributed either. (You must add ‘EXTRA_DIST = input’ to your ‘Makefile.am’ if ‘input’ is a source file.) Similarly file=output file2=out:in ... AC_CONFIG_FILES([$file:input],, [file=$file]) AC_CONFIG_FILES([$file2],, [file2=$file2]) will only cause ‘input’ to be distributed. No file will be cleaned automatically (add ‘DISTCLEANFILES = output out’ yourself), and no rebuild rule will be output. Obviously ‘automake’ cannot guess what value ‘$file’ is going to hold later when ‘configure’ is run, and it cannot use the shell variable ‘$file’ in a ‘Makefile’. However, if you make reference to ‘$file’ as ‘${file}’ (i.e., in a way that is compatible with ‘make’’s syntax) and furthermore use ‘AC_SUBST’ to ensure that ‘${file}’ is meaningful in a ‘Makefile’, then ‘automake’ will be able to use ‘${file}’ to generate all of these rules. For instance, here is how the Automake package itself generates versioned scripts for its test suite: AC_SUBST([APIVERSION], ...) ... AC_CONFIG_FILES( [tests/aclocal-${APIVERSION}:tests/aclocal.in], [chmod +x tests/aclocal-${APIVERSION}], [APIVERSION=$APIVERSION]) AC_CONFIG_FILES( [tests/automake-${APIVERSION}:tests/automake.in], [chmod +x tests/automake-${APIVERSION}]) Here cleaning, distributing, and rebuilding are done automatically, because ‘${APIVERSION}’ is known at ‘make’-time. Note that you should not use shell variables to declare ‘Makefile’ files for which ‘automake’ must create ‘Makefile.in’. Even ‘AC_SUBST’ does not help here, because ‘automake’ needs to know the file name when it runs in order to check whether ‘Makefile.am’ exists. (In the very hairy case that your setup requires such use of variables, you will have to tell Automake which ‘Makefile.in’s to generate on the command-line.) It is possible to let ‘automake’ emit conditional rules for ‘AC_CONFIG_FILES’ with the help of ‘AM_COND_IF’ (*note Optional::). To summarize: • Use literals for ‘Makefile’s, and for other files whenever possible. • Use ‘$file’ (or ‘${file}’ without ‘AC_SUBST([file])’) for files that ‘automake’ should ignore. • Use ‘${file}’ and ‘AC_SUBST([file])’ for files that ‘automake’ should not ignore.  File: automake.info, Node: Optional, Next: aclocal Invocation, Prev: Requirements, Up: configure 6.2 Other things Automake recognizes ==================================== Every time Automake is run it calls Autoconf to trace ‘configure.ac’. This way it can recognize the use of certain macros and tailor the generated ‘Makefile.in’ appropriately. Currently recognized macros and their effects are: ‘AC_CANONICAL_BUILD’ ‘AC_CANONICAL_HOST’ ‘AC_CANONICAL_TARGET’ Automake will ensure that ‘config.guess’ and ‘config.sub’ exist. Also, the ‘Makefile’ variables ‘build_triplet’, ‘host_triplet’ and ‘target_triplet’ are introduced. See *note Getting the Canonical System Type: (autoconf)Canonicalizing. ‘AC_CONFIG_AUX_DIR’ Automake will look for various helper scripts, such as ‘install-sh’, in the directory named in this macro invocation. (The full list of scripts is: ‘ar-lib’, ‘config.guess’, ‘config.sub’, ‘depcomp’, ‘compile’, ‘install-sh’, ‘ltmain.sh’, ‘mdate-sh’, ‘missing’, ‘mkinstalldirs’, ‘py-compile’, ‘test-driver’, ‘texinfo.tex’, ‘ylwrap’.) Not all scripts are always searched for; some scripts will only be sought if the generated ‘Makefile.in’ requires them. If ‘AC_CONFIG_AUX_DIR’ is used, it must be given before the call to ‘AM_INIT_AUTOMAKE’; Automake will warn about this if it is not so. All other ‘AC_CONFIG_...’ macros are conventionally called after ‘AM_INIT_AUTOMAKE’, though they may or may not work in other locations, with or without warnings. If ‘AC_CONFIG_AUX_DIR’ is not given, the scripts are looked for in their standard locations. For ‘mdate-sh’, ‘texinfo.tex’, and ‘ylwrap’, the standard location is the source directory corresponding to the current ‘Makefile.am’. For the rest, the standard location is the first one of ‘.’, ‘..’, or ‘../..’ (relative to the top source directory) that provides any one of the helper scripts. *Note Finding ‘configure’ Input: (autoconf)Input. Required files from ‘AC_CONFIG_AUX_DIR’ are automatically distributed, even if there is no ‘Makefile.am’ in this directory. ‘AC_CONFIG_LIBOBJ_DIR’ Automake will require the sources file declared with ‘AC_LIBSOURCE’ (see below) in the directory specified by this macro. ‘AC_CONFIG_HEADERS’ Automake will generate rules to rebuild these headers from the corresponding templates (usually, the template for a ‘foo.h’ header being ‘foo.h.in’). As with ‘AC_CONFIG_FILES’ (*note Requirements::), parts of the specification using shell variables will be ignored as far as cleaning, distributing, and rebuilding is concerned. Older versions of Automake required the use of ‘AM_CONFIG_HEADER’; this is no longer the case, and that macro has indeed been removed. ‘AC_CONFIG_LINKS’ Automake will generate rules to remove ‘configure’ generated links on ‘make distclean’ and to distribute named source files as part of ‘make dist’. As with ‘AC_CONFIG_FILES’ (*note Requirements::), parts of the specification using shell variables will be ignored as far as cleaning and distributing is concerned. (There are no rebuild rules for links.) ‘AC_LIBOBJ’ ‘AC_LIBSOURCE’ ‘AC_LIBSOURCES’ Automake will automatically distribute any file listed in ‘AC_LIBSOURCE’ or ‘AC_LIBSOURCES’. Note that the ‘AC_LIBOBJ’ macro calls ‘AC_LIBSOURCE’. So if an Autoconf macro is documented to call ‘AC_LIBOBJ([file])’, then ‘file.c’ will be distributed automatically by Automake. This encompasses many macros like ‘AC_FUNC_ALLOCA’, ‘AC_FUNC_MEMCMP’, ‘AC_REPLACE_FUNCS’, and others. By the way, direct assignments to ‘LIBOBJS’ are no longer supported. You should always use ‘AC_LIBOBJ’ for this purpose. *Note ‘AC_LIBOBJ’ vs. ‘LIBOBJS’: (autoconf)AC_LIBOBJ vs LIBOBJS. ‘AC_PROG_RANLIB’ This is required if any libraries are built in the package. *Note Particular Program Checks: (autoconf)Particular Programs. ‘AC_PROG_CXX’ This is required if any C++ source is included. *Note Particular Program Checks: (autoconf)Particular Programs. ‘AC_PROG_OBJC’ This is required if any Objective C source is included. *Note Particular Program Checks: (autoconf)Particular Programs. ‘AC_PROG_OBJCXX’ This is required if any Objective C++ source is included. *Note Particular Program Checks: (autoconf)Particular Programs. ‘AC_PROG_F77’ This is required if any Fortran 77 source is included. *Note Particular Program Checks: (autoconf)Particular Programs. ‘AC_F77_LIBRARY_LDFLAGS’ This is required for programs and shared libraries that are a mixture of languages that include Fortran 77 (*note Mixing Fortran 77 With C and C++::). *Note Autoconf macros supplied with Automake: Macros. ‘AC_FC_SRCEXT’ Automake will add the flags computed by ‘AC_FC_SRCEXT’ to compilation of files with the respective source extension (*note Fortran Compiler Characteristics: (autoconf)Fortran Compiler.). ‘AC_PROG_FC’ This is required if any Fortran 90/95 source is included. This macro is distributed with Autoconf version 2.58 and later. *Note Particular Program Checks: (autoconf)Particular Programs. ‘AC_PROG_LIBTOOL’ Automake will turn on processing for ‘libtool’ (*note Introduction: (libtool)Top.). ‘AC_PROG_YACC’ If a Yacc source file is seen, then you must either use this macro or define the variable ‘YACC’ in ‘configure.ac’. The former is preferred (*note Particular Program Checks: (autoconf)Particular Programs.). ‘AC_PROG_LEX’ If a Lex source file is seen, then this macro must be used. *Note Particular Program Checks: (autoconf)Particular Programs. ‘AC_REQUIRE_AUX_FILE’ For each ‘AC_REQUIRE_AUX_FILE([FILE])’, ‘automake’ will ensure that ‘FILE’ exists in the aux directory, and will complain otherwise. It will also automatically distribute the file. This macro should be used by third-party Autoconf macros that require some supporting files in the aux directory specified with ‘AC_CONFIG_AUX_DIR’ above. *Note Finding ‘configure’ Input: (autoconf)Input. ‘AC_SUBST’ The first argument is automatically defined as a variable in each generated ‘Makefile.in’, unless ‘AM_SUBST_NOTMAKE’ is also used for this variable. *Note Setting Output Variables: (autoconf)Setting Output Variables. For every substituted variable VAR, ‘automake’ will add a line ‘VAR = VALUE’ to each ‘Makefile.in’ file. Many Autoconf macros invoke ‘AC_SUBST’ to set output variables this way, e.g., ‘AC_PATH_XTRA’ defines ‘X_CFLAGS’ and ‘X_LIBS’. Thus, you can access these variables as ‘$(X_CFLAGS)’ and ‘$(X_LIBS)’ in any ‘Makefile.am’ if ‘AC_PATH_XTRA’ is called. ‘AM_CONDITIONAL’ This introduces an Automake conditional (*note Conditionals::). ‘AM_COND_IF’ This macro allows ‘automake’ to detect subsequent access within ‘configure.ac’ to a conditional previously introduced with ‘AM_CONDITIONAL’, thus enabling conditional ‘AC_CONFIG_FILES’ (*note Usage of Conditionals::). ‘AM_GNU_GETTEXT’ This macro is required for packages that use GNU gettext (*note gettext::). It is distributed with gettext. If Automake sees this macro it ensures that the package meets some of gettext’s requirements. ‘AM_GNU_GETTEXT_INTL_SUBDIR’ This macro specifies that the ‘intl/’ subdirectory is to be built, even if the ‘AM_GNU_GETTEXT’ macro was invoked with a first argument of ‘external’. ‘AM_MAINTAINER_MODE([DEFAULT-MODE])’ This macro adds an ‘--enable-maintainer-mode’ option to ‘configure’. If this is used, ‘automake’ will cause “maintainer-only” rules to be turned off by default in the generated ‘Makefile.in’s, unless DEFAULT-MODE is ‘enable’. This macro defines the ‘MAINTAINER_MODE’ conditional, which you can use in your own ‘Makefile.am’. *Note maintainer-mode::. ‘AM_SUBST_NOTMAKE(VAR)’ Prevent Automake from defining a variable VAR, even if it is substituted by ‘config.status’. Normally, Automake defines a ‘make’ variable for each ‘configure’ substitution, i.e., for each ‘AC_SUBST([VAR])’. This macro prevents that definition from Automake. If ‘AC_SUBST’ has not been called for this variable, then ‘AM_SUBST_NOTMAKE’ has no effects. Preventing variable definitions may be useful for substitution of multi-line values, where ‘VAR = @VALUE@’ might yield unintended results. ‘m4_include’ Files included by ‘configure.ac’ using this macro will be detected by Automake and automatically distributed. They will also appear as dependencies in ‘Makefile’ rules. ‘m4_include’ is seldom used by ‘configure.ac’ authors, but can appear in ‘aclocal.m4’ when ‘aclocal’ detects that some required macros come from files local to your package (as opposed to macros installed in a system-wide directory; *note aclocal Invocation::).  File: automake.info, Node: aclocal Invocation, Next: Macros, Prev: Optional, Up: configure 6.3 Auto-generating aclocal.m4 ============================== Automake includes a number of Autoconf macros that can be used in your package (*note Macros::); some of them are required by Automake in certain situations. These macros must be defined in your ‘aclocal.m4’; otherwise they will not be seen by ‘autoconf’. The ‘aclocal’ program will automatically generate ‘aclocal.m4’ files based on the contents of ‘configure.ac’. This provides a convenient way to get Automake-provided macros, without having to search around. The ‘aclocal’ mechanism allows other packages to supply their own macros (*note Extending aclocal::). You can also use it to maintain your own set of custom macros (*note Local Macros::). At startup, ‘aclocal’ scans all the ‘.m4’ files it can find, looking for macro definitions (*note Macro Search Path::). Then it scans ‘configure.ac’. Any mention of one of the macros found in the first step causes that macro, and any macros it in turn requires, to be put into ‘aclocal.m4’. _Putting_ the file that contains the macro definition into ‘aclocal.m4’ is usually done by copying the entire text of this file, including unused macro definitions as well as both ‘#’ and ‘dnl’ comments. If you want to make a comment that will be completely ignored by ‘aclocal’, use ‘##’ as the comment leader. When a file selected by ‘aclocal’ is located in a subdirectory specified as a relative search path with ‘aclocal’’s ‘-I’ argument, ‘aclocal’ assumes the file belongs to the package and uses ‘m4_include’ instead of copying it into ‘aclocal.m4’. This makes the package smaller, eases dependency tracking, and cause the file to be distributed automatically. (*Note Local Macros::, for an example.) Any macro that is found in a system-wide directory or via an absolute search path will be copied. So use ‘-I `pwd`/reldir’ instead of ‘-I reldir’ whenever some relative directory should be considered outside the package. The contents of ‘acinclude.m4’, if this file exists, are also automatically included in ‘aclocal.m4’. We recommend against using ‘acinclude.m4’ in new packages (*note Local Macros::). While computing ‘aclocal.m4’, ‘aclocal’ runs ‘autom4te’ (*note Using ‘Autom4te’: (autoconf)Using autom4te.) in order to trace the macros that are used, and omit from ‘aclocal.m4’ all macros that are mentioned but otherwise unexpanded (this can happen when a macro is called conditionally). ‘autom4te’ is expected to be in the ‘PATH’, just as ‘autoconf’. Its location can be overridden using the ‘AUTOM4TE’ environment variable. * Menu: * aclocal Options:: Options supported by aclocal * Macro Search Path:: How aclocal finds .m4 files * Extending aclocal:: Writing your own aclocal macros * Local Macros:: Organizing local macros * Serials:: Serial lines in Autoconf macros * Future of aclocal:: aclocal’s scheduled death  File: automake.info, Node: aclocal Options, Next: Macro Search Path, Up: aclocal Invocation 6.3.1 aclocal Options --------------------- ‘aclocal’ accepts the following options: ‘--automake-acdir=DIR’ Look for the automake-provided macro files in DIR instead of in the installation directory. This is typically used for debugging. The environment variable ‘ACLOCAL_AUTOMAKE_DIR’ provides another way to set the directory containing automake-provided macro files. However ‘--automake-acdir’ takes precedence over it. ‘--system-acdir=DIR’ Look for the system-wide third-party macro files (and the special ‘dirlist’ file) in DIR instead of in the installation directory. This is typically used for debugging. ‘--diff[=COMMAND]’ Run COMMAND on the M4 file that would be installed or overwritten by ‘--install’. The default COMMAND is ‘diff -u’. This option implies ‘--install’ and ‘--dry-run’. ‘--dry-run’ Do not overwrite (or create) ‘aclocal.m4’ and M4 files installed by ‘--install’. ‘--help’ Print a summary of the command line options and exit. ‘-I DIR’ Add the directory DIR to the list of directories searched for ‘.m4’ files. ‘--install’ Install system-wide third-party macros into the first directory specified with ‘-I DIR’ instead of copying them in the output file. Note that this will happen also if DIR is an absolute path. When this option is used, and only when this option is used, ‘aclocal’ will also honor ‘#serial NUMBER’ lines that appear in macros: an M4 file is ignored if there exists another M4 file with the same basename and a greater serial number in the search path (*note Serials::). ‘--force’ Always overwrite the output file. The default is to overwrite the output file only when needed, i.e., when its contents change or if one of its dependencies is younger. This option forces the update of ‘aclocal.m4’ (or the file specified with ‘--output’ below) and only this file, it has absolutely no influence on files that may need to be installed by ‘--install’. ‘--output=FILE’ Cause the output to be put into FILE instead of ‘aclocal.m4’. ‘--print-ac-dir’ Prints the name of the directory that ‘aclocal’ will search to find third-party ‘.m4’ files. When this option is given, normal processing is suppressed. This option was used _in the past_ by third-party packages to determine where to install ‘.m4’ macro files, but _this usage is today discouraged_, since it causes ‘$(prefix)’ not to be thoroughly honored (which violates the GNU Coding Standards), and similar semantics can be better obtained with the ‘ACLOCAL_PATH’ environment variable; *note Extending aclocal::. ‘--verbose’ Print the names of the files it examines. ‘--version’ Print the version number of Automake and exit. ‘-W CATEGORY’ ‘--warnings=CATEGORY’ Output warnings falling in CATEGORY. CATEGORY can be one of: ‘syntax’ dubious syntactic constructs, underquoted macros, unused macros, etc. ‘unsupported’ unknown macros ‘all’ all the warnings, this is the default ‘none’ turn off all the warnings ‘error’ treat warnings as errors All warnings are output by default. The environment variable ‘WARNINGS’ is honored in the same way as it is for ‘automake’ (*note automake Invocation::).  File: automake.info, Node: Macro Search Path, Next: Extending aclocal, Prev: aclocal Options, Up: aclocal Invocation 6.3.2 Macro Search Path ----------------------- By default, ‘aclocal’ searches for ‘.m4’ files in the following directories, in this order: ‘ACDIR-APIVERSION’ This is where the ‘.m4’ macros distributed with Automake itself are stored. APIVERSION depends on the Automake release used; for example, for Automake 1.11.x, APIVERSION = ‘1.11’. ‘ACDIR’ This directory is intended for third party ‘.m4’ files, and is configured when ‘automake’ itself is built. This is ‘@datadir@/aclocal/’, which typically expands to ‘${prefix}/share/aclocal/’. To find the compiled-in value of ACDIR, use the ‘--print-ac-dir’ option (*note aclocal Options::). As an example, suppose that ‘automake-1.11.2’ was configured with ‘--prefix=/usr/local’. Then, the search path would be: 1. ‘/usr/local/share/aclocal-1.11.2/’ 2. ‘/usr/local/share/aclocal/’ The paths for the ACDIR and ACDIR-APIVERSION directories can be changed respectively through aclocal options ‘--system-acdir’ and ‘--automake-acdir’ (*note aclocal Options::). Note however that these options are only intended for use by the internal Automake test suite, or for debugging under highly unusual situations; they are not ordinarily needed by end-users. As explained in (*note aclocal Options::), there are several options that can be used to change or extend this search path. Modifying the Macro Search Path: ‘-I DIR’ ......................................... Any extra directories specified using ‘-I’ options (*note aclocal Options::) are _prepended_ to this search list. Thus, ‘aclocal -I /foo -I /bar’ results in the following search path: 1. ‘/foo’ 2. ‘/bar’ 3. ACDIR-APIVERSION 4. ACDIR Modifying the Macro Search Path: ‘dirlist’ .......................................... There is a third mechanism for customizing the search path. If a ‘dirlist’ file exists in ACDIR, then that file is assumed to contain a list of directory patterns, one per line. ‘aclocal’ expands these patterns to directory names, and adds them to the search list _after_ all other directories. ‘dirlist’ entries may use shell wildcards such as ‘*’, ‘?’, or ‘[...]’. For example, suppose ‘ACDIR/dirlist’ contains the following: /test1 /test2 /test3* and that ‘aclocal’ was called with the ‘-I /foo -I /bar’ options. Then, the search path would be 1. ‘/foo’ 2. ‘/bar’ 3. ACDIR-APIVERSION 4. ACDIR 5. ‘/test1’ 6. ‘/test2’ and all directories with path names starting with ‘/test3’. If the ‘--system-acdir=DIR’ option is used, then ‘aclocal’ will search for the ‘dirlist’ file in DIR; but remember the warnings above against the use of ‘--system-acdir’. ‘dirlist’ is useful in the following situation: suppose that ‘automake’ version ‘1.11.2’ is installed with ‘--prefix=/usr’ by the system vendor. Thus, the default search directories are 1. ‘/usr/share/aclocal-1.11/’ 2. ‘/usr/share/aclocal/’ However, suppose further that many packages have been manually installed on the system, with $prefix=/usr/local, as is typical. In that case, many of these “extra” ‘.m4’ files are in ‘/usr/local/share/aclocal’. The only way to force ‘/usr/bin/aclocal’ to find these “extra” ‘.m4’ files is to always call ‘aclocal -I /usr/local/share/aclocal’. This is inconvenient. With ‘dirlist’, one may create a file ‘/usr/share/aclocal/dirlist’ containing only the single line /usr/local/share/aclocal Now, the “default” search path on the affected system is 1. ‘/usr/share/aclocal-1.11/’ 2. ‘/usr/share/aclocal/’ 3. ‘/usr/local/share/aclocal/’ without the need for ‘-I’ options; ‘-I’ options can be reserved for project-specific needs (‘my-source-dir/m4/’), rather than using them to work around local system-dependent tool installation directories. Similarly, ‘dirlist’ can be handy if you have installed a local copy of Automake in your account and want ‘aclocal’ to look for macros installed at other places on the system. Modifying the Macro Search Path: ‘ACLOCAL_PATH’ ............................................... The fourth and last mechanism to customize the macro search path is also the simplest. Any directory included in the colon-separated environment variable ‘ACLOCAL_PATH’ is added to the search path and takes precedence over system directories (including those found via ‘dirlist’), with the exception of the versioned directory ACDIR-APIVERSION (*note Macro Search Path::). However, directories passed via ‘-I’ will take precedence over directories in ‘ACLOCAL_PATH’. Also note that, if the ‘--install’ option is used, any ‘.m4’ file containing a required macro that is found in a directory listed in ‘ACLOCAL_PATH’ will be installed locally. In this case, serial numbers in ‘.m4’ are honored too, *note Serials::. Conversely to ‘dirlist’, ‘ACLOCAL_PATH’ is useful if you are using a global copy of Automake and want ‘aclocal’ to look for macros somewhere under your home directory. Planned future incompatibilities ................................ The order in which the directories in the macro search path are currently looked up is confusing and/or suboptimal in various aspects, and is probably going to be changed in the future Automake release. In particular, directories in ‘ACLOCAL_PATH’ and ‘ACDIR’ might end up taking precedence over ‘ACDIR-APIVERSION’, and directories in ‘ACDIR/dirlist’ might end up taking precedence over ‘ACDIR’. _This is a possible future incompatibility!_  File: automake.info, Node: Extending aclocal, Next: Local Macros, Prev: Macro Search Path, Up: aclocal Invocation 6.3.3 Writing your own aclocal macros ------------------------------------- The ‘aclocal’ program doesn’t have any built-in knowledge of any macros, so it is easy to extend it with your own macros. This can be used by libraries that want to supply their own Autoconf macros for use by other programs. For instance, the ‘gettext’ library supplies a macro ‘AM_GNU_GETTEXT’ that should be used by any package using ‘gettext’. When the library is installed, it installs this macro so that ‘aclocal’ will find it. A macro file’s name should end in ‘.m4’. Such files should be installed in ‘$(datadir)/aclocal’. This is as simple as writing: aclocaldir = $(datadir)/aclocal aclocal_DATA = mymacro.m4 myothermacro.m4 Please do use ‘$(datadir)/aclocal’, and not something based on the result of ‘aclocal --print-ac-dir’ (*note Hard-Coded Install Paths::, for arguments). It might also be helpful to suggest to the user to add the ‘$(datadir)/aclocal’ directory to his ‘ACLOCAL_PATH’ variable (*note ACLOCAL_PATH::) so that ‘aclocal’ will find the ‘.m4’ files installed by your package automatically. A file of macros should be a series of properly quoted ‘AC_DEFUN’’s (*note (autoconf)Macro Definitions::). The ‘aclocal’ programs also understands ‘AC_REQUIRE’ (*note (autoconf)Prerequisite Macros::), so it is safe to put each macro in a separate file. Each file should have no side effects but macro definitions. Especially, any call to ‘AC_PREREQ’ should be done inside the defined macro, not at the beginning of the file. Starting with Automake 1.8, ‘aclocal’ warns about all underquoted calls to ‘AC_DEFUN’. We realize this annoys some people, because ‘aclocal’ was not so strict in the past and many third party macros are underquoted; and we have to apologize for this temporary inconvenience. The reason we have to be stricter is that a future implementation of ‘aclocal’ (*note Future of aclocal::) will have to temporarily include all of these third party ‘.m4’ files, maybe several times, even including files that end up not being needed. Doing so should alleviate many problems of the current implementation; however, it requires a stricter style from macro authors. Hopefully it is easy to revise the existing macros. For instance, # bad style AC_PREREQ(2.68) AC_DEFUN(AX_FOOBAR, [AC_REQUIRE([AX_SOMETHING])dnl AX_FOO AX_BAR ]) should be rewritten as AC_DEFUN([AX_FOOBAR], [AC_PREREQ([2.68])dnl AC_REQUIRE([AX_SOMETHING])dnl AX_FOO AX_BAR ]) Wrapping the ‘AC_PREREQ’ call inside the macro ensures that Autoconf 2.68 will not be required if ‘AX_FOOBAR’ is not used. Most importantly, quoting the first argument of ‘AC_DEFUN’ allows the macro to be redefined or included twice (otherwise this first argument would be expanded during the second definition). For consistency we like to quote even arguments such as ‘2.68’ that do not require it. If you have been directed here by the ‘aclocal’ diagnostic but are not the maintainer of the implicated macro, you will want to contact the maintainer of that macro. Please make sure you have the latest version of the macro and that the problem hasn’t already been reported before doing so: people tend to work faster when they aren’t flooded by mails. Another situation where ‘aclocal’ is commonly used is to manage macros that are used locally by the package; *note Local Macros::.  File: automake.info, Node: Local Macros, Next: Serials, Prev: Extending aclocal, Up: aclocal Invocation 6.3.4 Handling Local Macros --------------------------- Feature tests offered by Autoconf do not cover all needs. People often have to supplement existing tests with their own macros, or with third-party macros. There are two ways to organize custom macros in a package. The first possibility (the historical practice) is to list all your macros in ‘acinclude.m4’. This file will be included in ‘aclocal.m4’ when you run ‘aclocal’, and its macro(s) will henceforth be visible to ‘autoconf’. However if it contains numerous macros, it will rapidly become difficult to maintain, and it will be almost impossible to share macros between packages. The second possibility, which we do recommend, is to write each macro in its own file and gather all these files in a directory. This directory is usually called ‘m4/’. Then it’s enough to update ‘configure.ac’ by adding a proper call to ‘AC_CONFIG_MACRO_DIRS’: AC_CONFIG_MACRO_DIRS([m4]) ‘aclocal’ will then take care of automatically adding ‘m4/’ to its search path for m4 files. When ‘aclocal’ is run, it will build an ‘aclocal.m4’ that ‘m4_include’s any file from ‘m4/’ that defines a required macro. Macros not found locally will still be searched in system-wide directories, as explained in *note Macro Search Path::. Custom macros should be distributed for the same reason that ‘configure.ac’ is: so that other people have all the sources of your package if they want to work on it. In fact, this distribution happens automatically because all ‘m4_include’d files are distributed. However there is no consensus on the distribution of third-party macros that your package may use. Many libraries install their own macro in the system-wide ‘aclocal’ directory (*note Extending aclocal::). For instance, Guile ships with a file called ‘guile.m4’ that contains the macro ‘GUILE_FLAGS’ that can be used to define setup compiler and linker flags appropriate for using Guile. Using ‘GUILE_FLAGS’ in ‘configure.ac’ will cause ‘aclocal’ to copy ‘guile.m4’ into ‘aclocal.m4’, but as ‘guile.m4’ is not part of the project, it will not be distributed. Technically, that means a user who needs to rebuild ‘aclocal.m4’ will have to install Guile first. This is probably OK, if Guile already is a requirement to build the package. However, if Guile is only an optional feature, or if your package might run on architectures where Guile cannot be installed, this requirement will hinder development. An easy solution is to copy such third-party macros in your local ‘m4/’ directory so they get distributed. Since Automake 1.10, ‘aclocal’ offers the option ‘--install’ to copy these system-wide third-party macros in your local macro directory, helping to solve the above problem. With this setup, system-wide macros will be copied to ‘m4/’ the first time you run ‘aclocal’. Then the locally installed macros will have precedence over the system-wide installed macros each time ‘aclocal’ is run again. One reason why you should keep ‘--install’ in the flags even after the first run is that when you later edit ‘configure.ac’ and depend on a new macro, this macro will be installed in your ‘m4/’ automatically. Another one is that serial numbers (*note Serials::) can be used to update the macros in your source tree automatically when new system-wide versions are installed. A serial number should be a single line of the form #serial NNN where NNN contains only digits and dots. It should appear in the M4 file before any macro definition. It is a good practice to maintain a serial number for each macro you distribute, even if you do not use the ‘--install’ option of ‘aclocal’: this allows other people to use it.  File: automake.info, Node: Serials, Next: Future of aclocal, Prev: Local Macros, Up: aclocal Invocation 6.3.5 Serial Numbers -------------------- Because third-party macros defined in ‘*.m4’ files are naturally shared between multiple projects, some people like to version them. This makes it easier to tell which of two M4 files is newer. Since at least 1996, the tradition is to use a ‘#serial’ line for this. A serial number should be a single line of the form # serial VERSION where VERSION is a version number containing only digits and dots. Usually people use a single integer, and they increment it each time they change the macro (hence the name of “serial”). Such a line should appear in the M4 file before any macro definition. The ‘#’ must be the first character on the line, and it is OK to have extra words after the version, as in #serial VERSION GARBAGE Normally these serial numbers are completely ignored by ‘aclocal’ and ‘autoconf’, like any genuine comment. However when using ‘aclocal’’s ‘--install’ feature, these serial numbers will modify the way ‘aclocal’ selects the macros to install in the package: if two files with the same basename exist in your search path, and if at least one of them uses a ‘#serial’ line, ‘aclocal’ will ignore the file that has the older ‘#serial’ line (or the file that has none). Note that a serial number applies to a whole M4 file, not to any macro it contains. A file can contain multiple macros, but only one serial. Here is a use case that illustrates the use of ‘--install’ and its interaction with serial numbers. Let’s assume we maintain a package called MyPackage, the ‘configure.ac’ of which requires a third-party macro ‘AX_THIRD_PARTY’ defined in ‘/usr/share/aclocal/thirdparty.m4’ as follows: # serial 1 AC_DEFUN([AX_THIRD_PARTY], [...]) MyPackage uses an ‘m4/’ directory to store local macros as explained in *note Local Macros::, and has AC_CONFIG_MACRO_DIRS([m4]) in its ‘configure.ac’. Initially the ‘m4/’ directory is empty. The first time we run ‘aclocal --install’, it will notice that • ‘configure.ac’ uses ‘AX_THIRD_PARTY’ • No local macros define ‘AX_THIRD_PARTY’ • ‘/usr/share/aclocal/thirdparty.m4’ defines ‘AX_THIRD_PARTY’ with serial number 1. Because ‘/usr/share/aclocal/thirdparty.m4’ is a system-wide macro and ‘aclocal’ was given the ‘--install’ option, it will copy this file in ‘m4/thirdparty.m4’, and output an ‘aclocal.m4’ that contains ‘m4_include([m4/thirdparty.m4])’. The next time ‘aclocal --install’ is run, something different happens. ‘aclocal’ notices that • ‘configure.ac’ uses ‘AX_THIRD_PARTY’ • ‘m4/thirdparty.m4’ defines ‘AX_THIRD_PARTY’ with serial number 1. • ‘/usr/share/aclocal/thirdparty.m4’ defines ‘AX_THIRD_PARTY’ with serial number 1. Because both files have the same serial number, ‘aclocal’ uses the first it found in its search path order (*note Macro Search Path::). ‘aclocal’ therefore ignores ‘/usr/share/aclocal/thirdparty.m4’ and outputs an ‘aclocal.m4’ that contains ‘m4_include([m4/thirdparty.m4])’. Local directories specified with ‘-I’ are always searched before system-wide directories, so a local file will always be preferred to the system-wide file in case of equal serial numbers. Now suppose the system-wide third-party macro is changed. This can happen if the package installing this macro is updated. Let’s suppose the new macro has serial number 2. The next time ‘aclocal --install’ is run the situation is the following: • ‘configure.ac’ uses ‘AX_THIRD_PARTY’ • ‘m4/thirdparty.m4’ defines ‘AX_THIRD_PARTY’ with serial number 1. • ‘/usr/share/aclocal/thirdparty.m4’ defines ‘AX_THIRD_PARTY’ with serial 2. When ‘aclocal’ sees a greater serial number, it immediately forgets anything it knows from files that have the same basename and a smaller serial number. So after it has found ‘/usr/share/aclocal/thirdparty.m4’ with serial 2, ‘aclocal’ will proceed as if it had never seen ‘m4/thirdparty.m4’. This brings us back to a situation similar to that at the beginning of our example, where no local file defined the macro. ‘aclocal’ will install the new version of the macro in ‘m4/thirdparty.m4’, in this case overriding the old version. MyPackage just had its macro updated as a side effect of running ‘aclocal’. If you are leery of letting ‘aclocal’ update your local macro, you can run ‘aclocal --diff’ to review the changes ‘aclocal --install’ would perform on these macros. Finally, note that the ‘--force’ option of ‘aclocal’ has absolutely no effect on the files installed by ‘--install’. For instance, if you have modified your local macros, do not expect ‘--install --force’ to replace the local macros by their system-wide versions. If you want to do so, simply erase the local macros you want to revert, and run ‘aclocal --install’.  File: automake.info, Node: Future of aclocal, Prev: Serials, Up: aclocal Invocation 6.3.6 The Future of ‘aclocal’ ----------------------------- Ideally, ‘aclocal’ should not be part of Automake. Automake should focus on generating ‘Makefile’s; dealing with M4 macros is more Autoconf’s job. The fact that some people install Automake just to use ‘aclocal’, but do not use ‘automake’ otherwise is an indication of how that feature is misplaced. The new implementation will probably be done slightly differently. For instance, it could enforce the ‘m4/’-style layout discussed in *note Local Macros::. We have no idea when and how this will happen. This has been discussed several times in the past, but someone still has to commit to that non-trivial task. From the user point of view, ‘aclocal’’s removal might turn out to be painful. There is a simple precaution that you may take to make that switch more seamless: never call ‘aclocal’ yourself. Keep this guy under the exclusive control of ‘autoreconf’ and Automake’s rebuild rules. Hopefully you won’t need to worry about things breaking; when ‘aclocal’ disappears, because everything will have been taken care of. If otherwise you used to call ‘aclocal’ directly yourself or from some script, you will quickly notice the change. Many packages come with a script called ‘bootstrap’ or ‘autogen.sh’, that will just call ‘aclocal’, ‘libtoolize’, ‘gettextize’ or ‘autopoint’, ‘autoconf’, ‘autoheader’, and ‘automake’ in the right order. In fact, this is precisely what ‘autoreconf’ can do for you. If your package has such a ‘bootstrap’ or ‘autogen.sh’ script, consider using ‘autoreconf’. That should simplify its logic a lot (less things to maintain, all to the good), it’s even likely you will not need the script anymore, and more to the point you will not call ‘aclocal’ directly anymore. For the time being, third-party packages should continue to install public macros into ‘/usr/share/aclocal/’. If ‘aclocal’ is replaced by another tool it might make sense to rename the directory, but supporting ‘/usr/share/aclocal/’ for backward compatibility should be easy provided all macros are properly written (*note Extending aclocal::).  File: automake.info, Node: Macros, Prev: aclocal Invocation, Up: configure 6.4 Autoconf macros supplied with Automake ========================================== Automake ships with several Autoconf macros that you can use from your ‘configure.ac’. When you use one of them it will be included by ‘aclocal’ in ‘aclocal.m4’. * Menu: * Public Macros:: Macros that you can use. * Obsolete Macros:: Macros that will soon be removed. * Private Macros:: Macros that you should not use.  File: automake.info, Node: Public Macros, Next: Obsolete Macros, Up: Macros 6.4.1 Public Macros ------------------- ‘AM_INIT_AUTOMAKE([OPTIONS])’ Runs many macros required for proper operation of the generated Makefiles. Today, ‘AM_INIT_AUTOMAKE’ is called with a single argument: a space-separated list of Automake options that should be applied to every ‘Makefile.am’ in the tree. The effect is as if each option were listed in ‘AUTOMAKE_OPTIONS’ (*note Options::). This macro can also be called in another, _deprecated_ form: ‘AM_INIT_AUTOMAKE(PACKAGE, VERSION, [NO-DEFINE])’. In this form, there are two required arguments: the package and the version number. This usage is mostly obsolete because the PACKAGE and VERSION can be obtained from Autoconf’s ‘AC_INIT’ macro. However, differently from what happens for ‘AC_INIT’ invocations, this ‘AM_INIT_AUTOMAKE’ invocation supports shell variables’ expansions in the ‘PACKAGE’ and ‘VERSION’ arguments (which otherwise defaults, respectively, to the ‘PACKAGE_TARNAME’ and ‘PACKAGE_VERSION’ defined via the ‘AC_INIT’ invocation; *note The ‘AC_INIT’ macro: (autoconf)AC_INIT.); and this can still be useful in some selected situations. Our hope is that future Autoconf versions will improve their support for package versions defined dynamically at configure runtime; when (and if) this happens, support for the two-args ‘AM_INIT_AUTOMAKE’ invocation will likely be removed from Automake. If your ‘configure.ac’ has: AC_INIT([src/foo.c]) AM_INIT_AUTOMAKE([mumble], [1.5]) you should modernize it as follows: AC_INIT([mumble], [1.5]) AC_CONFIG_SRCDIR([src/foo.c]) AM_INIT_AUTOMAKE Note that if you’re upgrading your ‘configure.ac’ from an earlier version of Automake, it is not always correct to simply move the package and version arguments from ‘AM_INIT_AUTOMAKE’ directly to ‘AC_INIT’, as in the example above. The first argument to ‘AC_INIT’ should be the name of your package (e.g., ‘GNU Automake’), not the tarball name (e.g., ‘automake’) that you used to pass to ‘AM_INIT_AUTOMAKE’. Autoconf tries to derive a tarball name from the package name, which should work for most but not all package names. (If it doesn’t work for yours, you can use the four-argument form of ‘AC_INIT’ to provide the tarball name explicitly). By default this macro ‘AC_DEFINE’’s ‘PACKAGE’ and ‘VERSION’. This can be avoided by passing the ‘no-define’ option (*note List of Automake options::): AM_INIT_AUTOMAKE([no-define ...]) ‘AM_PATH_LISPDIR’ Searches for the program ‘emacs’, and, if found, sets the output variable ‘lispdir’ to the full path to Emacs’ site-lisp directory. Note that this test assumes the ‘emacs’ found to be a version that supports Emacs Lisp (such as GNU Emacs or XEmacs). Other emacsen can cause this test to hang (some, like old versions of MicroEmacs, start up in interactive mode, requiring ‘C-x C-c’ to exit, which is hardly obvious for a non-emacs user). In most cases, however, you should be able to use ‘C-c’ to kill the test. In order to avoid problems, you can set ‘EMACS’ to “no” in the environment, or use the ‘--with-lispdir’ option to ‘configure’ to explicitly set the correct path (if you’re sure you have an ‘emacs’ that supports Emacs Lisp). ‘AM_PROG_AR([ACT-IF-FAIL])’ You must use this macro when you use the archiver in your project, if you want support for unusual archivers such as Microsoft ‘lib’. The content of the optional argument is executed if the archiver interface is not recognized; the default action is to abort configure with an error message. ‘AM_PROG_AS’ Use this macro when you have assembly code in your project. This will choose the assembler for you (by default the C compiler) and set ‘CCAS’, and will also set ‘CCASFLAGS’ if required. ‘AM_PROG_CC_C_O’ This is an obsolescent macro that checks that the C compiler supports the ‘-c’ and ‘-o’ options together. Note that, since Automake 1.14, the ‘AC_PROG_CC’ is rewritten to implement such checks itself, and thus the explicit use of ‘AM_PROG_CC_C_O’ should no longer be required. ‘AM_PROG_LEX’ Like ‘AC_PROG_LEX’ (*note Particular Program Checks: (autoconf)Particular Programs.), but uses the ‘missing’ script on systems that do not have ‘lex’. HP-UX 10 is one such system. ‘AM_PROG_GCJ’ This macro finds the ‘gcj’ program or causes an error. It sets ‘GCJ’ and ‘GCJFLAGS’. ‘gcj’ is the Java front-end to the GNU Compiler Collection. ‘AM_PROG_UPC([COMPILER-SEARCH-LIST])’ Find a compiler for Unified Parallel C and define the ‘UPC’ variable. The default COMPILER-SEARCH-LIST is ‘upcc upc’. This macro will abort ‘configure’ if no Unified Parallel C compiler is found. ‘AM_MISSING_PROG(NAME, PROGRAM)’ Find a maintainer tool PROGRAM and define the NAME environment variable with its location. If PROGRAM is not detected, then NAME will instead invoke the ‘missing’ script, in order to give useful advice to the user about the missing maintainer tool. *Note maintainer-mode::, for more information on when the ‘missing’ script is appropriate. ‘AM_SILENT_RULES’ Control the machinery for less verbose build output (*note Automake Silent Rules::). ‘AM_WITH_DMALLOC’ Add support for the Dmalloc package (https://dmalloc.com/). If the user runs ‘configure’ with ‘--with-dmalloc’, then define ‘WITH_DMALLOC’ and add ‘-ldmalloc’ to ‘LIBS’.  File: automake.info, Node: Obsolete Macros, Next: Private Macros, Prev: Public Macros, Up: Macros 6.4.2 Obsolete Macros --------------------- Although using some of the following macros was required in past releases, you should not use any of them in new code. _All these macros will be removed in the next major Automake version_; if you are still using them, running ‘autoupdate’ should adjust your ‘configure.ac’ automatically (*note Using ‘autoupdate’ to Modernize ‘configure.ac’: (autoconf)autoupdate Invocation.). _Do it NOW!_ ‘AM_PROG_MKDIR_P’ From Automake 1.8 to 1.9.6 this macro used to define the output variable ‘mkdir_p’ to one of ‘mkdir -p’, ‘install-sh -d’, or ‘mkinstalldirs’. Nowadays Autoconf provides a similar functionality with ‘AC_PROG_MKDIR_P’ (*note Particular Program Checks: (autoconf)Particular Programs.), however this defines the output variable ‘MKDIR_P’ instead. In case you are still using the ‘AM_PROG_MKDIR_P’ macro in your ‘configure.ac’, or its provided variable ‘$(mkdir_p)’ in your ‘Makefile.am’, you are advised to switch ASAP to the more modern Autoconf-provided interface instead; both the macro and the variable might be removed in a future major Automake release.  File: automake.info, Node: Private Macros, Prev: Obsolete Macros, Up: Macros 6.4.3 Private Macros -------------------- The following macros are private macros you should not call directly. They are called by the other public macros when appropriate. Do not rely on them, as they might be changed in a future version. Consider them as implementation details; or better, do not consider them at all: skip this section! ‘_AM_DEPENDENCIES’ ‘AM_SET_DEPDIR’ ‘AM_DEP_TRACK’ ‘AM_OUTPUT_DEPENDENCY_COMMANDS’ These macros are used to implement Automake’s automatic dependency tracking scheme. They are called automatically by Automake when required, and there should be no need to invoke them manually. ‘AM_MAKE_INCLUDE’ This macro is used to discover how the user’s ‘make’ handles ‘include’ statements. This macro is automatically invoked when needed; there should be no need to invoke it manually. ‘AM_PROG_INSTALL_STRIP’ This is used to find a version of ‘install’ that can be used to strip a program at installation time. This macro is automatically included when required. ‘AM_SANITY_CHECK’ This checks to make sure that a file created in the build directory is newer than a file in the source directory. This can fail on systems where the clock is set incorrectly. This macro is automatically run from ‘AM_INIT_AUTOMAKE’.  File: automake.info, Node: Directories, Next: Programs, Prev: configure, Up: Top 7 Directories ************* For simple projects that distribute all files in the same directory it is enough to have a single ‘Makefile.am’ that builds everything in place. In larger projects, it is common to organize files in different directories, in a tree. For example, there could be a directory for the program’s source, one for the testsuite, and one for the documentation; or, for very large projects, there could be one directory per program, per library or per module. The traditional approach is to build these subdirectories recursively, employing _make recursion_: each directory contains its own ‘Makefile’, and when ‘make’ is run from the top-level directory, it enters each subdirectory in turn, and invokes there a new ‘make’ instance to build the directory’s contents. Because this approach is very widespread, Automake offers built-in support for it. However, it is worth noting that the use of make recursion has its own serious issues and drawbacks, and that it’s well possible to have packages with a multi directory layout that make little or no use of such recursion (examples of such packages are GNU Bison and GNU Automake itself); see also the *note Alternative:: section below. * Menu: * Subdirectories:: Building subdirectories recursively * Conditional Subdirectories:: Conditionally not building directories * Alternative:: Subdirectories without recursion * Subpackages:: Nesting packages  File: automake.info, Node: Subdirectories, Next: Conditional Subdirectories, Up: Directories 7.1 Recursing subdirectories ============================ In packages using make recursion, the top level ‘Makefile.am’ must tell Automake which subdirectories are to be built. This is done via the ‘SUBDIRS’ variable. The ‘SUBDIRS’ variable holds a list of subdirectories in which building of various sorts can occur. The rules for many targets (e.g., ‘all’) in the generated ‘Makefile’ will run commands both locally and in all specified subdirectories. Note that the directories listed in ‘SUBDIRS’ are not required to contain ‘Makefile.am’s; only ‘Makefile’s (after configuration). This allows inclusion of libraries from packages that do not use Automake (such as ‘gettext’; see also *note Third-Party Makefiles::). In packages that use subdirectories, the top-level ‘Makefile.am’ is often very short. For instance, here is the ‘Makefile.am’ from the GNU Hello distribution: EXTRA_DIST = BUGS ChangeLog.O README-alpha SUBDIRS = doc intl po src tests When Automake invokes ‘make’ in a subdirectory, it uses the value of the ‘MAKE’ variable. It passes the value of the variable ‘AM_MAKEFLAGS’ to the ‘make’ invocation; this can be set in ‘Makefile.am’ if there are flags you must always pass to ‘make’. The directories mentioned in ‘SUBDIRS’ are usually direct children of the current directory, each subdirectory containing its own ‘Makefile.am’ with a ‘SUBDIRS’ pointing to deeper subdirectories. Automake can be used to construct packages of arbitrary depth this way. By default, Automake generates ‘Makefiles’ that work depth-first in postfix order: the subdirectories are built before the current directory. However, it is possible to change this ordering. You can do this by putting ‘.’ into ‘SUBDIRS’. For instance, putting ‘.’ first will cause a prefix ordering of directories. Using SUBDIRS = lib src . test will cause ‘lib/’ to be built before ‘src/’, then the current directory will be built, finally the ‘test/’ directory will be built. It is customary to arrange test directories to be built after everything else since they are meant to test what has been constructed. In addition to the built-in recursive targets defined by Automake (‘all’, ‘check’, etc.), the developer can also define his own recursive targets. That is done by passing the names of such targets as arguments to the m4 macro ‘AM_EXTRA_RECURSIVE_TARGETS’ in ‘configure.ac’. Automake generates rules to handle the recursion for such targets; and the developer can define real actions for them by defining corresponding ‘-local’ targets. % cat configure.ac AC_INIT([pkg-name], [1.0]) AM_INIT_AUTOMAKE AM_EXTRA_RECURSIVE_TARGETS([foo]) AC_CONFIG_FILES([Makefile sub/Makefile sub/src/Makefile]) AC_OUTPUT % cat Makefile.am SUBDIRS = sub foo-local: @echo This will be run by "make foo". % cat sub/Makefile.am SUBDIRS = src % cat sub/src/Makefile.am foo-local: @echo This too will be run by a "make foo" issued either in @echo the 'sub/src/' directory, the 'sub/' directory, or the @echo top-level directory.  File: automake.info, Node: Conditional Subdirectories, Next: Alternative, Prev: Subdirectories, Up: Directories 7.2 Conditional Subdirectories ============================== It is possible to define the ‘SUBDIRS’ variable conditionally if, like in the case of GNU Inetutils, you want to only build a subset of the entire package. To illustrate how this works, let’s assume we have two directories, ‘src/’ and ‘opt/’. ‘src/’ should always be built, but we want to decide in ‘configure’ whether ‘opt/’ will be built or not. (For this example we will assume that ‘opt/’ should be built when the variable ‘$want_opt’ was set to ‘yes’.) Running ‘make’ should thus recurse into ‘src/’ always, and then maybe in ‘opt/’. However ‘make dist’ should always recurse into both ‘src/’ and ‘opt/’, because ‘opt/’ should be distributed even if it is not needed in the current configuration. This means ‘opt/Makefile’ should be created _unconditionally_. There are two ways to set up a project like this. You can use Automake conditionals (*note Conditionals::) or use Autoconf ‘AC_SUBST’ variables (*note Setting Output Variables: (autoconf)Setting Output Variables.). Using Automake conditionals is the preferred solution. Before we illustrate these two possibilities, let’s introduce ‘DIST_SUBDIRS’. * Menu: * SUBDIRS vs DIST_SUBDIRS:: Two sets of directories * Subdirectories with AM_CONDITIONAL:: Specifying conditional subdirectories * Subdirectories with AC_SUBST:: Another way for conditional recursion * Unconfigured Subdirectories:: Not even creating a ‘Makefile’  File: automake.info, Node: SUBDIRS vs DIST_SUBDIRS, Next: Subdirectories with AM_CONDITIONAL, Up: Conditional Subdirectories 7.2.1 ‘SUBDIRS’ vs. ‘DIST_SUBDIRS’ ---------------------------------- Automake considers two sets of directories, defined by the variables ‘SUBDIRS’ and ‘DIST_SUBDIRS’. ‘SUBDIRS’ contains the subdirectories of the current directory that must be built (*note Subdirectories::). It must be defined manually; Automake will never guess a directory is to be built. As we will see in the next two sections, it is possible to define it conditionally so that some directory will be omitted from the build. ‘DIST_SUBDIRS’ is used in rules that need to recurse in all directories, even those that have been conditionally left out of the build. Recall our example where we may not want to build subdirectory ‘opt/’, but yet we want to distribute it? This is where ‘DIST_SUBDIRS’ comes into play: ‘opt’ may not appear in ‘SUBDIRS’, but it must appear in ‘DIST_SUBDIRS’. Precisely, ‘DIST_SUBDIRS’ is used by ‘make maintainer-clean’, ‘make distclean’ and ‘make dist’. All other recursive rules use ‘SUBDIRS’. If ‘SUBDIRS’ is defined conditionally using Automake conditionals, Automake will define ‘DIST_SUBDIRS’ automatically from the possible values of ‘SUBDIRS’ in all conditions. If ‘SUBDIRS’ contains ‘AC_SUBST’ variables, ‘DIST_SUBDIRS’ will not be defined correctly because Automake does not know the possible values of these variables. In this case ‘DIST_SUBDIRS’ needs to be defined manually.  File: automake.info, Node: Subdirectories with AM_CONDITIONAL, Next: Subdirectories with AC_SUBST, Prev: SUBDIRS vs DIST_SUBDIRS, Up: Conditional Subdirectories 7.2.2 Subdirectories with ‘AM_CONDITIONAL’ ------------------------------------------ ‘configure’ should output the ‘Makefile’ for each directory and define a condition into which ‘opt/’ should be built. ... AM_CONDITIONAL([COND_OPT], [test "$want_opt" = yes]) AC_CONFIG_FILES([Makefile src/Makefile opt/Makefile]) ... Then ‘SUBDIRS’ can be defined in the top-level ‘Makefile.am’ as follows. if COND_OPT MAYBE_OPT = opt endif SUBDIRS = src $(MAYBE_OPT) As you can see, running ‘make’ will rightly recurse into ‘src/’ and maybe ‘opt/’. As you can’t see, running ‘make dist’ will recurse into both ‘src/’ and ‘opt/’ directories because ‘make dist’, unlike ‘make all’, doesn’t use the ‘SUBDIRS’ variable. It uses the ‘DIST_SUBDIRS’ variable. In this case Automake will define ‘DIST_SUBDIRS = src opt’ automatically because it knows that ‘MAYBE_OPT’ can contain ‘opt’ in some condition.  File: automake.info, Node: Subdirectories with AC_SUBST, Next: Unconfigured Subdirectories, Prev: Subdirectories with AM_CONDITIONAL, Up: Conditional Subdirectories 7.2.3 Subdirectories with ‘AC_SUBST’ ------------------------------------ Another possibility is to define ‘MAYBE_OPT’ from ‘./configure’ using ‘AC_SUBST’: ... if test "$want_opt" = yes; then MAYBE_OPT=opt else MAYBE_OPT= fi AC_SUBST([MAYBE_OPT]) AC_CONFIG_FILES([Makefile src/Makefile opt/Makefile]) ... In this case the top-level ‘Makefile.am’ should look as follows. SUBDIRS = src $(MAYBE_OPT) DIST_SUBDIRS = src opt The drawback is that since Automake cannot guess what the possible values of ‘MAYBE_OPT’ are, it is necessary to define ‘DIST_SUBDIRS’.  File: automake.info, Node: Unconfigured Subdirectories, Prev: Subdirectories with AC_SUBST, Up: Conditional Subdirectories 7.2.4 Unconfigured Subdirectories --------------------------------- The semantics of ‘DIST_SUBDIRS’ are often misunderstood by some users that try to _configure and build_ subdirectories conditionally. Here by configuring we mean creating the ‘Makefile’ (it might also involve running a nested ‘configure’ script: this is a costly operation that explains why people want to do it conditionally, but only the ‘Makefile’ is relevant to the discussion). The above examples all assume that every ‘Makefile’ is created, even in directories that are not going to be built. The simple reason is that we want ‘make dist’ to distribute even the directories that are not being built (e.g., platform-dependent code), hence ‘make dist’ must recurse into the subdirectory, hence this directory must be configured and appear in ‘DIST_SUBDIRS’. Building packages that do not configure every subdirectory is a tricky business, and we do not recommend it to the novice as it is easy to produce an incomplete tarball by mistake. We will not discuss this topic in depth here, yet for the adventurous here are a few rules to remember. • ‘SUBDIRS’ should always be a subset of ‘DIST_SUBDIRS’. It makes little sense to have a directory in ‘SUBDIRS’ that is not in ‘DIST_SUBDIRS’. Think of the former as a way to tell which directories listed in the latter should be built. • Any directory listed in ‘DIST_SUBDIRS’ and ‘SUBDIRS’ must be configured. That is, the ‘Makefile’ must exist or the recursive ‘make’ rules will not be able to process the directory. • Any configured directory must be listed in ‘DIST_SUBDIRS’. This is so the cleaning rules remove the generated ‘Makefile’s. It would be correct to see ‘DIST_SUBDIRS’ as a variable that lists all the directories that have been configured. In order to prevent recursion in some unconfigured directory you must therefore ensure that this directory does not appear in ‘DIST_SUBDIRS’ (and ‘SUBDIRS’). For instance, if you define ‘SUBDIRS’ conditionally using ‘AC_SUBST’ and do not define ‘DIST_SUBDIRS’ explicitly, it will be default to ‘$(SUBDIRS)’; another possibility is to force ‘DIST_SUBDIRS = $(SUBDIRS)’. Of course, directories that are omitted from ‘DIST_SUBDIRS’ will not be distributed unless you make other arrangements for this to happen (for instance, always running ‘make dist’ in a configuration where all directories are known to appear in ‘DIST_SUBDIRS’; or writing a ‘dist-hook’ target to distribute these directories). In a few packages, unconfigured directories are not even expected to be distributed. Although these packages do not require the aforementioned extra arrangements, there is another pitfall. If the name of a directory appears in ‘SUBDIRS’ or ‘DIST_SUBDIRS’, ‘automake’ will make sure the directory exists. Consequently ‘automake’ cannot be run on such a distribution when one directory has been omitted. One way to avoid this check is to use the ‘AC_SUBST’ method to declare conditional directories; since ‘automake’ does not know the values of ‘AC_SUBST’ variables it cannot ensure the corresponding directory exists.  File: automake.info, Node: Alternative, Next: Subpackages, Prev: Conditional Subdirectories, Up: Directories 7.3 An Alternative Approach to Subdirectories ============================================= If you’ve ever read Peter Miller’s excellent paper, ‘Recursive Make Considered Harmful’, the preceding sections on the use of make recursion will probably come as unwelcome advice. For those who haven’t read the paper, Miller’s main thesis is that recursive ‘make’ invocations are both slow and error-prone. Automake is intended to have sufficient cross-directory support to enable you to write a single ‘Makefile.am’ for a complex multi-directory package. (If it seems to be lacking, please report the issue as usual.) By default an installable file specified in a subdirectory will have its directory name stripped before installation. For instance, in this example, the header file will be installed as ‘$(includedir)/stdio.h’: include_HEADERS = inc/stdio.h However, the ‘nobase_’ prefix can be used to circumvent this path stripping. In this example, the header file will be installed as ‘$(includedir)/sys/types.h’: nobase_include_HEADERS = sys/types.h ‘nobase_’ should be specified first when used in conjunction with either ‘dist_’ or ‘nodist_’ (*note Fine-grained Distribution Control::). For instance: nobase_dist_pkgdata_DATA = images/vortex.pgm sounds/whirl.ogg Finally, note that a variable using the ‘nobase_’ prefix can often be replaced by several variables, one for each destination directory (*note Uniform::). For instance, the last example could be rewritten as follows: imagesdir = $(pkgdatadir)/images soundsdir = $(pkgdatadir)/sounds dist_images_DATA = images/vortex.pgm dist_sounds_DATA = sounds/whirl.ogg This latter syntax makes it possible to change one destination directory without changing the layout of the source tree. Currently, ‘nobase_*_LTLIBRARIES’ are the only exception to this rule, in that there is no particular installation order guarantee for an otherwise equivalent set of variables without ‘nobase_’ prefix.  File: automake.info, Node: Subpackages, Prev: Alternative, Up: Directories 7.4 Nesting Packages ==================== In the GNU Build System, packages can be nested to arbitrary depth. This means that a package can embed other packages with their own ‘configure’, ‘Makefile’s, etc. These other packages should just appear as subdirectories of their parent package. They must be listed in ‘SUBDIRS’ like other ordinary directories. However the subpackage’s ‘Makefile’s should be output by its own ‘configure’ script, not by the parent’s ‘configure’. This is achieved using the ‘AC_CONFIG_SUBDIRS’ Autoconf macro (*note AC_CONFIG_SUBDIRS: (autoconf)Subdirectories.). Here is an example package for an ‘arm’ program that links with a ‘hand’ library that is a nested package in subdirectory ‘hand/’. ‘arm’’s ‘configure.ac’: AC_INIT([arm], [1.0]) AC_CONFIG_AUX_DIR([.]) AM_INIT_AUTOMAKE AC_PROG_CC AC_CONFIG_FILES([Makefile]) # Call hand's ./configure script recursively. AC_CONFIG_SUBDIRS([hand]) AC_OUTPUT ‘arm’’s ‘Makefile.am’: # Build the library in the hand subdirectory first. SUBDIRS = hand # Include hand's header when compiling this directory. AM_CPPFLAGS = -I$(srcdir)/hand bin_PROGRAMS = arm arm_SOURCES = arm.c # link with the hand library. arm_LDADD = hand/libhand.a Now here is ‘hand’’s ‘hand/configure.ac’: AC_INIT([hand], [1.2]) AC_CONFIG_AUX_DIR([.]) AM_INIT_AUTOMAKE AC_PROG_CC AM_PROG_AR AC_PROG_RANLIB AC_CONFIG_FILES([Makefile]) AC_OUTPUT and its ‘hand/Makefile.am’: lib_LIBRARIES = libhand.a libhand_a_SOURCES = hand.c When ‘make dist’ is run from the top-level directory it will create an archive ‘arm-1.0.tar.gz’ that contains the ‘arm’ code as well as the ‘hand’ subdirectory. This package can be built and installed like any ordinary package, with the usual ‘./configure && make && make install’ sequence (the ‘hand’ subpackage will be built and installed by the process). When ‘make dist’ is run from the hand directory, it will create a self-contained ‘hand-1.2.tar.gz’ archive. So although it appears to be embedded in another package, it can still be used separately. The purpose of the ‘AC_CONFIG_AUX_DIR([.])’ instruction is to force Automake and Autoconf to search for auxiliary scripts in the current directory. For instance, this means that there will be two copies of ‘install-sh’: one in the top-level of the ‘arm’ package, and another one in the ‘hand/’ subdirectory for the ‘hand’ package. The historical default is to search for these auxiliary scripts in the parent directory and the grandparent directory. So if the ‘AC_CONFIG_AUX_DIR([.])’ line was removed from ‘hand/configure.ac’, that subpackage would share the auxiliary script of the ‘arm’ package. This may look like a gain in size (a few kilobytes), but more importantly, it is a loss of modularity as the ‘hand’ subpackage is no longer self-contained (‘make dist’ in the subdirectory will not work anymore). Packages that do not use Automake need more work to be integrated this way. *Note Third-Party Makefiles::.  File: automake.info, Node: Programs, Next: Other Objects, Prev: Directories, Up: Top 8 Building Programs and Libraries ********************************* A large part of Automake’s functionality is dedicated to making it easy to build programs and libraries. * Menu: * A Program:: Building a program * A Library:: Building a library * A Shared Library:: Building a Libtool library * Program and Library Variables:: Variables controlling program and library builds * Default _SOURCES:: Default source files * LIBOBJS:: Special handling for LIBOBJS and ALLOCA * Program Variables:: Variables used when building a program * Yacc and Lex:: Yacc and Lex support * C++ Support:: Compiling C++ sources * Objective C Support:: Compiling Objective C sources * Objective C++ Support:: Compiling Objective C++ sources * Unified Parallel C Support:: Compiling Unified Parallel C sources * Assembly Support:: Compiling assembly sources * Fortran 77 Support:: Compiling Fortran 77 sources * Fortran 9x Support:: Compiling Fortran 9x sources * Java Support with gcj:: Compiling Java sources using gcj * Vala Support:: Compiling Vala sources * Support for Other Languages:: Compiling other languages * Dependencies:: Automatic dependency tracking * EXEEXT:: Support for executable extensions  File: automake.info, Node: A Program, Next: A Library, Up: Programs 8.1 Building a program ====================== In order to build a program, you need to tell Automake which sources are part of it, and which libraries it should be linked with. This section also covers conditional compilation of sources or programs. Most of the comments about these also apply to libraries (*note A Library::) and libtool libraries (*note A Shared Library::). * Menu: * Program Sources:: Defining program sources * Linking:: Linking with libraries or extra objects * Conditional Sources:: Handling conditional sources * Conditional Programs:: Building a program conditionally  File: automake.info, Node: Program Sources, Next: Linking, Up: A Program 8.1.1 Defining program sources ------------------------------ In a directory containing source that gets built into a program (as opposed to a library or a script), the ‘PROGRAMS’ primary is used. Programs can be installed in ‘bindir’, ‘sbindir’, ‘libexecdir’, ‘pkglibexecdir’, or not at all (‘noinst_’). They can also be built only for ‘make check’, in which case the prefix is ‘check_’. For instance: bin_PROGRAMS = hello In this simple case, the resulting ‘Makefile.in’ will contain code to generate a program named ‘hello’. Associated with each program are several assisting variables that are named after the program. These variables are all optional, and have reasonable defaults. Each variable, its use, and default is spelled out below; we use the “hello” example throughout. The variable ‘hello_SOURCES’ is used to specify which source files get built into an executable: hello_SOURCES = hello.c version.c getopt.c getopt1.c getopt.h system.h This causes each mentioned ‘.c’ file to be compiled into the corresponding ‘.o’. Then all are linked to produce ‘hello’. If ‘hello_SOURCES’ is not specified, then it defaults to the single file ‘hello.c’ (*note Default _SOURCES::). Multiple programs can be built in a single directory. Multiple programs can share a single source file, which must be listed in each ‘_SOURCES’ definition. Header files listed in a ‘_SOURCES’ definition will be included in the distribution but otherwise ignored. In case it isn’t obvious, you should not include the header file generated by ‘configure’ in a ‘_SOURCES’ variable; this file should not be distributed. Lex (‘.l’) and Yacc (‘.y’) files can also be listed; see *note Yacc and Lex::.  File: automake.info, Node: Linking, Next: Conditional Sources, Prev: Program Sources, Up: A Program 8.1.2 Linking the program ------------------------- If you need to link against libraries that are not found by ‘configure’, you can use ‘LDADD’ to do so. This variable is used to specify additional objects or libraries to link with; it is inappropriate for specifying specific linker flags; you should use ‘AM_LDFLAGS’ for this purpose. Sometimes, multiple programs are built in one directory but do not share the same link-time requirements. In this case, you can use the ‘PROG_LDADD’ variable (where PROG is the name of the program as it appears in some ‘_PROGRAMS’ variable, and usually written in lowercase) to override ‘LDADD’. If this variable exists for a given program, then that program is not linked using ‘LDADD’. For instance, in GNU cpio, ‘pax’, ‘cpio’ and ‘mt’ are linked against the library ‘libcpio.a’. However, ‘rmt’ is built in the same directory, and has no such link requirement. Also, ‘mt’ and ‘rmt’ are only built on certain architectures. Here is what cpio’s ‘src/Makefile.am’ looks like (abridged): bin_PROGRAMS = cpio pax $(MT) libexec_PROGRAMS = $(RMT) EXTRA_PROGRAMS = mt rmt LDADD = ../lib/libcpio.a $(INTLLIBS) rmt_LDADD = cpio_SOURCES = ... pax_SOURCES = ... mt_SOURCES = ... rmt_SOURCES = ... ‘PROG_LDADD’ is inappropriate for passing program-specific linker flags (except for ‘-l’, ‘-L’, ‘-dlopen’ and ‘-dlpreopen’). So, use the ‘PROG_LDFLAGS’ variable for this purpose. It is also occasionally useful to have a program depend on some other target that is not in fact part of that program. This can be done using either the ‘PROG_DEPENDENCIES’ or the ‘EXTRA_PROG_DEPENDENCIES’ variable. Each program depends on the contents both variables, but no further interpretation is done. Since these dependencies are associated to the link rule used to create the programs they should normally list files used by the link command. That is ‘*.$(OBJEXT)’, ‘*.a’, or ‘*.la’ files. In rare cases you may need to add other kinds of files such as linker scripts, but _listing a source file in ‘_DEPENDENCIES’ is wrong_. If some source file needs to be built before all the components of a program are built, consider using the ‘BUILT_SOURCES’ variable instead (*note Sources::). If ‘PROG_DEPENDENCIES’ is not supplied, it is computed by Automake. The automatically-assigned value is the contents of ‘PROG_LDADD’, with most configure substitutions, ‘-l’, ‘-L’, ‘-dlopen’ and ‘-dlpreopen’ options removed. The configure substitutions that are left in are only ‘$(LIBOBJS)’ and ‘$(ALLOCA)’; these are left because it is known that they will not cause an invalid value for ‘PROG_DEPENDENCIES’ to be generated. *note Conditional Sources:: shows a situation where ‘_DEPENDENCIES’ may be used. The ‘EXTRA_PROG_DEPENDENCIES’ may be useful for cases where you merely want to augment the ‘automake’-generated ‘PROG_DEPENDENCIES’ rather than replacing it. We recommend that you avoid using ‘-l’ options in ‘LDADD’ or ‘PROG_LDADD’ when referring to libraries built by your package. Instead, write the file name of the library explicitly as in the above ‘cpio’ example. Use ‘-l’ only to list third-party libraries. If you follow this rule, the default value of ‘PROG_DEPENDENCIES’ will list all your local libraries and omit the other ones.  File: automake.info, Node: Conditional Sources, Next: Conditional Programs, Prev: Linking, Up: A Program 8.1.3 Conditional compilation of sources ---------------------------------------- You can’t put a configure substitution (e.g., ‘@FOO@’ or ‘$(FOO)’ where ‘FOO’ is defined via ‘AC_SUBST’) into a ‘_SOURCES’ variable. The reason for this is a bit hard to explain, but suffice to say that it simply won’t work. Automake will give an error if you try to do this. Fortunately there are two other ways to achieve the same result. One is to use configure substitutions in ‘_LDADD’ variables, the other is to use an Automake conditional. Conditional Compilation using ‘_LDADD’ Substitutions .................................................... Automake must know all the source files that could possibly go into a program, even if not all the files are built in every circumstance. Any files that are only conditionally built should be listed in the appropriate ‘EXTRA_’ variable. For instance, if ‘hello-linux.c’ or ‘hello-generic.c’ were conditionally included in ‘hello’, the ‘Makefile.am’ would contain: bin_PROGRAMS = hello hello_SOURCES = hello-common.c EXTRA_hello_SOURCES = hello-linux.c hello-generic.c hello_LDADD = $(HELLO_SYSTEM) hello_DEPENDENCIES = $(HELLO_SYSTEM) You can then set up the ‘$(HELLO_SYSTEM)’ substitution from ‘configure.ac’: ... case $host in *linux*) HELLO_SYSTEM='hello-linux.$(OBJEXT)' ;; *) HELLO_SYSTEM='hello-generic.$(OBJEXT)' ;; esac AC_SUBST([HELLO_SYSTEM]) ... In this case, the variable ‘HELLO_SYSTEM’ should be replaced by either ‘hello-linux.o’ or ‘hello-generic.o’, and added to both ‘hello_DEPENDENCIES’ and ‘hello_LDADD’ in order to be built and linked in. Conditional Compilation using Automake Conditionals ................................................... An often simpler way to compile source files conditionally is to use Automake conditionals. For instance, you could use this ‘Makefile.am’ construct to build the same ‘hello’ example: bin_PROGRAMS = hello if LINUX hello_SOURCES = hello-linux.c hello-common.c else hello_SOURCES = hello-generic.c hello-common.c endif In this case, ‘configure.ac’ should set up the ‘LINUX’ conditional using ‘AM_CONDITIONAL’ (*note Conditionals::). When using conditionals like this you don’t need to use the ‘EXTRA_’ variable, because Automake will examine the contents of each variable to construct the complete list of source files. If your program uses a lot of files, you will probably prefer a conditional ‘+=’. bin_PROGRAMS = hello hello_SOURCES = hello-common.c if LINUX hello_SOURCES += hello-linux.c else hello_SOURCES += hello-generic.c endif  File: automake.info, Node: Conditional Programs, Prev: Conditional Sources, Up: A Program 8.1.4 Conditional compilation of programs ----------------------------------------- Sometimes it is useful to determine the programs that are to be built at configure time. For instance, GNU ‘cpio’ only builds ‘mt’ and ‘rmt’ under special circumstances. The means to achieve conditional compilation of programs are the same you can use to compile source files conditionally: substitutions or conditionals. Conditional Programs using ‘configure’ Substitutions .................................................... In this case, you must notify Automake of all the programs that can possibly be built, but at the same time cause the generated ‘Makefile.in’ to use the programs specified by ‘configure’. This is done by having ‘configure’ substitute values into each ‘_PROGRAMS’ definition, while listing all optionally built programs in ‘EXTRA_PROGRAMS’. bin_PROGRAMS = cpio pax $(MT) libexec_PROGRAMS = $(RMT) EXTRA_PROGRAMS = mt rmt As explained in *note EXEEXT::, Automake will rewrite ‘bin_PROGRAMS’, ‘libexec_PROGRAMS’, and ‘EXTRA_PROGRAMS’, appending ‘$(EXEEXT)’ to each binary. Obviously it cannot rewrite values obtained at run-time through ‘configure’ substitutions, therefore you should take care of appending ‘$(EXEEXT)’ yourself, as in ‘AC_SUBST([MT], ['mt${EXEEXT}'])’. Conditional Programs using Automake Conditionals ................................................ You can also use Automake conditionals (*note Conditionals::) to select programs to be built. In this case you don’t have to worry about ‘$(EXEEXT)’ or ‘EXTRA_PROGRAMS’. bin_PROGRAMS = cpio pax if WANT_MT bin_PROGRAMS += mt endif if WANT_RMT libexec_PROGRAMS = rmt endif  File: automake.info, Node: A Library, Next: A Shared Library, Prev: A Program, Up: Programs 8.2 Building a library ====================== Building a library is much like building a program. In this case, the name of the primary is ‘LIBRARIES’. Libraries can be installed in ‘libdir’ or ‘pkglibdir’. *Note A Shared Library::, for information on how to build shared libraries using libtool and the ‘LTLIBRARIES’ primary. Each ‘_LIBRARIES’ variable is a list of the libraries to be built. For instance, to create a library named ‘libcpio.a’, but not install it, you would write: noinst_LIBRARIES = libcpio.a libcpio_a_SOURCES = ... The sources that go into a library are determined exactly as they are for programs, via the ‘_SOURCES’ variables. Note that the library name is canonicalized (*note Canonicalization::), so the ‘_SOURCES’ variable corresponding to ‘libcpio.a’ is ‘libcpio_a_SOURCES’, not ‘libcpio.a_SOURCES’. Extra objects can be added to a library using the ‘LIBRARY_LIBADD’ variable. This should be used for objects determined by ‘configure’. Again from ‘cpio’: libcpio_a_LIBADD = $(LIBOBJS) $(ALLOCA) In addition, sources for extra objects that will not exist until configure-time must be added to the ‘BUILT_SOURCES’ variable (*note Sources::). Building a static library is done by compiling all object files, then by invoking ‘$(AR) $(ARFLAGS)’ followed by the name of the library and the list of objects, and finally by calling ‘$(RANLIB)’ on that library. You should call ‘AC_PROG_RANLIB’ from your ‘configure.ac’ to define ‘RANLIB’ (Automake will complain otherwise). You should also call ‘AM_PROG_AR’ to define ‘AR’, in order to support unusual archivers such as Microsoft lib. ‘ARFLAGS’ will default to ‘cru’; you can override this variable by setting it in your ‘Makefile.am’ or by ‘AC_SUBST’ing it from your ‘configure.ac’. You can override the ‘AR’ variable by defining a per-library ‘maude_AR’ variable (*note Program and Library Variables::). Be careful when selecting library components conditionally. Because building an empty library is not portable, you should ensure that any library always contains at least one object. To use a static library when building a program, add it to ‘LDADD’ for this program. In the following example, the program ‘cpio’ is statically linked with the library ‘libcpio.a’. noinst_LIBRARIES = libcpio.a libcpio_a_SOURCES = ... bin_PROGRAMS = cpio cpio_SOURCES = cpio.c ... cpio_LDADD = libcpio.a  File: automake.info, Node: A Shared Library, Next: Program and Library Variables, Prev: A Library, Up: Programs 8.3 Building a Shared Library ============================= Building shared libraries portably is a relatively complex matter. For this reason, GNU Libtool (*note Introduction: (libtool)Top.) was created to help build shared libraries in a platform-independent way. * Menu: * Libtool Concept:: Introducing Libtool * Libtool Libraries:: Declaring Libtool Libraries * Conditional Libtool Libraries:: Building Libtool Libraries Conditionally * Conditional Libtool Sources:: Choosing Library Sources Conditionally * Libtool Convenience Libraries:: Building Convenience Libtool Libraries * Libtool Modules:: Building Libtool Modules * Libtool Flags:: Using _LIBADD, _LDFLAGS, and _LIBTOOLFLAGS * LTLIBOBJS:: Using $(LTLIBOBJS) and $(LTALLOCA) * Libtool Issues:: Common Issues Related to Libtool’s Use  File: automake.info, Node: Libtool Concept, Next: Libtool Libraries, Up: A Shared Library 8.3.1 The Libtool Concept ------------------------- Libtool abstracts shared and static libraries into a unified concept henceforth called “libtool libraries”. Libtool libraries are files using the ‘.la’ suffix, and can designate a static library, a shared library, or maybe both. Their exact nature cannot be determined until ‘./configure’ is run: not all platforms support all kinds of libraries, and users can explicitly select which libraries should be built. (However the package’s maintainers can tune the default; *note The ‘LT_INIT’ macro: (libtool)LT_INIT.) Because object files for shared and static libraries must be compiled differently, libtool is also used during compilation. Object files built by libtool are called “libtool objects”: these are files using the ‘.lo’ suffix. Libtool libraries are built from these libtool objects. You should not assume anything about the structure of ‘.la’ or ‘.lo’ files and how libtool constructs them: this is libtool’s concern, and the last thing one wants is to learn about libtool’s guts. However the existence of these files matters, because they are used as targets and dependencies in ‘Makefile’s’ rules when building libtool libraries. There are situations where you may have to refer to these, for instance when expressing dependencies for building source files conditionally (*note Conditional Libtool Sources::). People considering writing a plug-in system, with dynamically loaded modules, should look into ‘libltdl’: libtool’s dlopening library (*note Using libltdl: (libtool)Using libltdl.). This offers a portable dlopening facility to load libtool libraries dynamically, and can also achieve static linking where unavoidable. Before we discuss how to use libtool with Automake in detail, it should be noted that the libtool manual also has a section about how to use Automake with libtool (*note Using Automake with Libtool: (libtool)Using Automake.).  File: automake.info, Node: Libtool Libraries, Next: Conditional Libtool Libraries, Prev: Libtool Concept, Up: A Shared Library 8.3.2 Building Libtool Libraries -------------------------------- Automake uses libtool to build libraries declared with the ‘LTLIBRARIES’ primary. Each ‘_LTLIBRARIES’ variable is a list of libtool libraries to build. For instance, to create a libtool library named ‘libgettext.la’, and install it in ‘libdir’, write: lib_LTLIBRARIES = libgettext.la libgettext_la_SOURCES = gettext.c gettext.h ... Automake predefines the variable ‘pkglibdir’, so you can use ‘pkglib_LTLIBRARIES’ to install libraries in ‘$(libdir)/@PACKAGE@/’. If ‘gettext.h’ is a public header file that needs to be installed in order for people to use the library, it should be declared using a ‘_HEADERS’ variable, not in ‘libgettext_la_SOURCES’. Headers listed in the latter should be internal headers that are not part of the public interface. lib_LTLIBRARIES = libgettext.la libgettext_la_SOURCES = gettext.c ... include_HEADERS = gettext.h ... A package can build and install such a library along with other programs that use it. This dependency should be specified using ‘LDADD’. The following example builds a program named ‘hello’ that is linked with ‘libgettext.la’. lib_LTLIBRARIES = libgettext.la libgettext_la_SOURCES = gettext.c ... bin_PROGRAMS = hello hello_SOURCES = hello.c ... hello_LDADD = libgettext.la Whether ‘hello’ is statically or dynamically linked with ‘libgettext.la’ is not yet known: this will depend on the configuration of libtool and the capabilities of the host.  File: automake.info, Node: Conditional Libtool Libraries, Next: Conditional Libtool Sources, Prev: Libtool Libraries, Up: A Shared Library 8.3.3 Building Libtool Libraries Conditionally ---------------------------------------------- Like conditional programs (*note Conditional Programs::), there are two main ways to build conditional libraries: using Automake conditionals or using Autoconf ‘AC_SUBST’itutions. The important implementation detail you have to be aware of is that the place where a library will be installed matters to libtool: it needs to be indicated _at link-time_ using the ‘-rpath’ option. For libraries whose destination directory is known when Automake runs, Automake will automatically supply the appropriate ‘-rpath’ option to libtool. This is the case for libraries listed explicitly in some installable ‘_LTLIBRARIES’ variables such as ‘lib_LTLIBRARIES’. However, for libraries determined at configure time (and thus mentioned in ‘EXTRA_LTLIBRARIES’), Automake does not know the final installation directory. For such libraries you must add the ‘-rpath’ option to the appropriate ‘_LDFLAGS’ variable by hand. The examples below illustrate the differences between these two methods. Here is an example where ‘WANTEDLIBS’ is an ‘AC_SUBST’ed variable set at ‘./configure’-time to either ‘libfoo.la’, ‘libbar.la’, both, or none. Although ‘$(WANTEDLIBS)’ appears in the ‘lib_LTLIBRARIES’, Automake cannot guess it relates to ‘libfoo.la’ or ‘libbar.la’ at the time it creates the link rule for these two libraries. Therefore the ‘-rpath’ argument must be explicitly supplied. EXTRA_LTLIBRARIES = libfoo.la libbar.la lib_LTLIBRARIES = $(WANTEDLIBS) libfoo_la_SOURCES = foo.c ... libfoo_la_LDFLAGS = -rpath '$(libdir)' libbar_la_SOURCES = bar.c ... libbar_la_LDFLAGS = -rpath '$(libdir)' Here is how the same ‘Makefile.am’ would look using Automake conditionals named ‘WANT_LIBFOO’ and ‘WANT_LIBBAR’. Now Automake is able to compute the ‘-rpath’ setting itself, because it’s clear that both libraries will end up in ‘$(libdir)’ if they are installed. lib_LTLIBRARIES = if WANT_LIBFOO lib_LTLIBRARIES += libfoo.la endif if WANT_LIBBAR lib_LTLIBRARIES += libbar.la endif libfoo_la_SOURCES = foo.c ... libbar_la_SOURCES = bar.c ...  File: automake.info, Node: Conditional Libtool Sources, Next: Libtool Convenience Libraries, Prev: Conditional Libtool Libraries, Up: A Shared Library 8.3.4 Libtool Libraries with Conditional Sources ------------------------------------------------ Conditional compilation of sources in a library can be achieved in the same way as conditional compilation of sources in a program (*note Conditional Sources::). The only difference is that ‘_LIBADD’ should be used instead of ‘_LDADD’ and that it should mention libtool objects (‘.lo’ files). So, to mimic the ‘hello’ example from *note Conditional Sources::, we could build a ‘libhello.la’ library using either ‘hello-linux.c’ or ‘hello-generic.c’ with the following ‘Makefile.am’. lib_LTLIBRARIES = libhello.la libhello_la_SOURCES = hello-common.c EXTRA_libhello_la_SOURCES = hello-linux.c hello-generic.c libhello_la_LIBADD = $(HELLO_SYSTEM) libhello_la_DEPENDENCIES = $(HELLO_SYSTEM) And make sure ‘configure’ defines ‘HELLO_SYSTEM’ as either ‘hello-linux.lo’ or ‘hello-generic.lo’. Or we could simply use an Automake conditional as follows. lib_LTLIBRARIES = libhello.la libhello_la_SOURCES = hello-common.c if LINUX libhello_la_SOURCES += hello-linux.c else libhello_la_SOURCES += hello-generic.c endif  File: automake.info, Node: Libtool Convenience Libraries, Next: Libtool Modules, Prev: Conditional Libtool Sources, Up: A Shared Library 8.3.5 Libtool Convenience Libraries ----------------------------------- Sometimes you want to build libtool libraries that should not be installed. These are called “libtool convenience libraries” and are typically used to encapsulate many sublibraries, later gathered into one big installed library. Libtool convenience libraries are declared by directory-less variables such as ‘noinst_LTLIBRARIES’, ‘check_LTLIBRARIES’, or even ‘EXTRA_LTLIBRARIES’. Unlike installed libtool libraries they do not need an ‘-rpath’ flag at link time (this is in fact the only difference). Convenience libraries listed in ‘noinst_LTLIBRARIES’ are always built. Those listed in ‘check_LTLIBRARIES’ are built only upon ‘make check’. Finally, libraries listed in ‘EXTRA_LTLIBRARIES’ are never built explicitly: Automake outputs rules to build them, but if the library does not appear as a Makefile dependency anywhere it won’t be built (this is why ‘EXTRA_LTLIBRARIES’ is used for conditional compilation). Here is a sample setup merging libtool convenience libraries from subdirectories into one main ‘libtop.la’ library. # -- Top-level Makefile.am -- SUBDIRS = sub1 sub2 ... lib_LTLIBRARIES = libtop.la libtop_la_SOURCES = libtop_la_LIBADD = \ sub1/libsub1.la \ sub2/libsub2.la \ ... # -- sub1/Makefile.am -- noinst_LTLIBRARIES = libsub1.la libsub1_la_SOURCES = ... # -- sub2/Makefile.am -- # showing nested convenience libraries SUBDIRS = sub2.1 sub2.2 ... noinst_LTLIBRARIES = libsub2.la libsub2_la_SOURCES = libsub2_la_LIBADD = \ sub21/libsub21.la \ sub22/libsub22.la \ ... When using such a setup, beware that ‘automake’ will assume ‘libtop.la’ is to be linked with the C linker. This is because ‘libtop_la_SOURCES’ is empty, so ‘automake’ picks C as default language. If ‘libtop_la_SOURCES’ was not empty, ‘automake’ would select the linker as explained in *note How the Linker is Chosen::. If one of the sublibraries contains non-C source, it is important that the appropriate linker be chosen. One way to achieve this is to pretend that there is such a non-C file among the sources of the library, thus forcing ‘automake’ to select the appropriate linker. Here is the top-level ‘Makefile’ of our example updated to force C++ linking. SUBDIRS = sub1 sub2 ... lib_LTLIBRARIES = libtop.la libtop_la_SOURCES = # Dummy C++ source to cause C++ linking. nodist_EXTRA_libtop_la_SOURCES = dummy.cxx libtop_la_LIBADD = \ sub1/libsub1.la \ sub2/libsub2.la \ ... ‘EXTRA_*_SOURCES’ variables are used to keep track of source files that might be compiled (this is mostly useful when doing conditional compilation using ‘AC_SUBST’; *note Conditional Libtool Sources::), and the ‘nodist_’ prefix means the listed sources are not to be distributed (*note Program and Library Variables::). In effect the file ‘dummy.cxx’ does not need to exist in the source tree. Of course if you have some real source file to list in ‘libtop_la_SOURCES’ there is no point in cheating with ‘nodist_EXTRA_libtop_la_SOURCES’.  File: automake.info, Node: Libtool Modules, Next: Libtool Flags, Prev: Libtool Convenience Libraries, Up: A Shared Library 8.3.6 Libtool Modules --------------------- These are libtool libraries meant to be dlopened. They are indicated to libtool by passing ‘-module’ at link-time. pkglib_LTLIBRARIES = mymodule.la mymodule_la_SOURCES = doit.c mymodule_la_LDFLAGS = -module Ordinarily, Automake requires that a library’s name start with ‘lib’. However, when building a dynamically loadable module you might wish to use a "nonstandard" name. Automake will not complain about such nonstandard names if it knows the library being built is a libtool module, i.e., if ‘-module’ explicitly appears in the library’s ‘_LDFLAGS’ variable (or in the common ‘AM_LDFLAGS’ variable when no per-library ‘_LDFLAGS’ variable is defined). As always, ‘AC_SUBST’ variables are black boxes to Automake since their values are not yet known when ‘automake’ is run. Therefore if ‘-module’ is set via such a variable, Automake cannot notice it and will proceed as if the library was an ordinary libtool library, with strict naming. If ‘mymodule_la_SOURCES’ is not specified, then it defaults to the single file ‘mymodule.c’ (*note Default _SOURCES::).  File: automake.info, Node: Libtool Flags, Next: LTLIBOBJS, Prev: Libtool Modules, Up: A Shared Library 8.3.7 ‘_LIBADD’, ‘_LDFLAGS’, and ‘_LIBTOOLFLAGS’ ------------------------------------------------ As shown in previous sections, the ‘LIBRARY_LIBADD’ variable should be used to list extra libtool objects (‘.lo’ files) or libtool libraries (‘.la’) to add to LIBRARY. The ‘LIBRARY_LDFLAGS’ variable is the place to list additional libtool linking flags, such as ‘-version-info’, ‘-static’, and a lot more. *Note Link mode: (libtool)Link mode. The ‘libtool’ command has two kinds of options: mode-specific options and generic options. Mode-specific options such as the aforementioned linking flags should be lumped with the other flags passed to the tool invoked by ‘libtool’ (hence the use of ‘LIBRARY_LDFLAGS’ for libtool linking flags). Generic options include ‘--tag=TAG’ and ‘--silent’ (*note Invoking ‘libtool’: (libtool)Invoking libtool. for more options). They should appear before the mode selection on the command line; in ‘Makefile.am’s they should be listed in the ‘LIBRARY_LIBTOOLFLAGS’ variable. If ‘LIBRARY_LIBTOOLFLAGS’ is not defined, then the variable ‘AM_LIBTOOLFLAGS’ is used instead. These flags are passed to libtool after the ‘--tag=TAG’ option computed by Automake (if any), so ‘LIBRARY_LIBTOOLFLAGS’ (or ‘AM_LIBTOOLFLAGS’) is a good place to override or supplement the ‘--tag=TAG’ setting. The libtool rules also use a ‘LIBTOOLFLAGS’ variable that should not be set in ‘Makefile.am’: this is a user variable (*note Flag Variables Ordering::). It allows users to run ‘make LIBTOOLFLAGS=--silent’, for instance. Note that the verbosity of ‘libtool’ can also be influenced by the Automake support for silent rules (*note Automake Silent Rules::).  File: automake.info, Node: LTLIBOBJS, Next: Libtool Issues, Prev: Libtool Flags, Up: A Shared Library 8.3.8 ‘LTLIBOBJS’ and ‘LTALLOCA’ -------------------------------- Where an ordinary library might include ‘$(LIBOBJS)’ or ‘$(ALLOCA)’ (*note LIBOBJS::), a libtool library must use ‘$(LTLIBOBJS)’ or ‘$(LTALLOCA)’. This is required because the object files that libtool operates on do not necessarily end in ‘.o’. Nowadays, the computation of ‘LTLIBOBJS’ from ‘LIBOBJS’ is performed automatically by Autoconf (*note ‘AC_LIBOBJ’ vs. ‘LIBOBJS’: (autoconf)AC_LIBOBJ vs LIBOBJS.).  File: automake.info, Node: Libtool Issues, Prev: LTLIBOBJS, Up: A Shared Library 8.3.9 Common Issues Related to Libtool’s Use -------------------------------------------- * Menu: * Error required file ltmain.sh not found:: The need to run libtoolize * Objects created both with libtool and without:: Avoid a specific build race  File: automake.info, Node: Error required file ltmain.sh not found, Next: Objects created both with libtool and without, Up: Libtool Issues 8.3.9.1 Error: ‘required file `./ltmain.sh' not found’ ...................................................... Libtool comes with a tool called ‘libtoolize’ that will install libtool’s supporting files into a package. Running this command will install ‘ltmain.sh’. You should execute it before ‘aclocal’ and ‘automake’. People upgrading old packages to newer autotools are likely to face this issue because older Automake versions used to call ‘libtoolize’. Therefore old build scripts do not call ‘libtoolize’. Since Automake 1.6, it has been decided that running ‘libtoolize’ was none of Automake’s business. Instead, that functionality has been moved into the ‘autoreconf’ command (*note Using ‘autoreconf’: (autoconf)autoreconf Invocation.). If you do not want to remember what to run and when, just learn the ‘autoreconf’ command. Hopefully, replacing existing ‘bootstrap’ or ‘autogen.sh’ scripts by a call to ‘autoreconf’ should also free you from any similar incompatible change in the future.  File: automake.info, Node: Objects created both with libtool and without, Prev: Error required file ltmain.sh not found, Up: Libtool Issues 8.3.9.2 Objects ‘created with both libtool and without’ ....................................................... Sometimes, the same source file is used both to build a libtool library and to build another non-libtool target (be it a program or another library). Let’s consider the following ‘Makefile.am’. bin_PROGRAMS = prog prog_SOURCES = prog.c foo.c ... lib_LTLIBRARIES = libfoo.la libfoo_la_SOURCES = foo.c ... (In this trivial case the issue could be avoided by linking ‘libfoo.la’ with ‘prog’ instead of listing ‘foo.c’ in ‘prog_SOURCES’. But let’s assume we want to keep ‘prog’ and ‘libfoo.la’ separate.) Technically, it means that we should build ‘foo.$(OBJEXT)’ for ‘prog’, and ‘foo.lo’ for ‘libfoo.la’. The problem is that in the course of creating ‘foo.lo’, libtool may erase (or replace) ‘foo.$(OBJEXT)’, and this cannot be avoided. Therefore, when Automake detects this situation it will complain with a message such as object 'foo.$(OBJEXT)' created both with libtool and without A workaround for this issue is to ensure that these two objects get different basenames. As explained in *note Renamed Objects::, this happens automatically when per-target flags are used. bin_PROGRAMS = prog prog_SOURCES = prog.c foo.c ... prog_CFLAGS = $(AM_CFLAGS) lib_LTLIBRARIES = libfoo.la libfoo_la_SOURCES = foo.c ... Adding ‘prog_CFLAGS = $(AM_CFLAGS)’ is almost a no-op, because when the ‘prog_CFLAGS’ is defined, it is used instead of ‘AM_CFLAGS’. However as a side effect it will cause ‘prog.c’ and ‘foo.c’ to be compiled as ‘prog-prog.$(OBJEXT)’ and ‘prog-foo.$(OBJEXT)’, which solves the issue.  File: automake.info, Node: Program and Library Variables, Next: Default _SOURCES, Prev: A Shared Library, Up: Programs 8.4 Program and Library Variables ================================= Associated with each program is a collection of variables that can be used to modify how that program is built. There is a similar list of such variables for each library. The canonical name of the program (or library) is used as a base for naming these variables. In the list below, we use the name “maude” to refer to the program or library. In your ‘Makefile.am’ you would replace this with the canonical name of your program. This list also refers to “maude” as a program, but in general the same rules apply for both static and dynamic libraries; the documentation below notes situations where programs and libraries differ. ‘maude_SOURCES’ This variable, if it exists, lists all the source files that are compiled to build the program. These files are added to the distribution by default. When building the program, Automake will cause each source file to be compiled to a single ‘.o’ file (or ‘.lo’ when using libtool). Normally these object files are named after the source file, but other factors can change this. If a file in the ‘_SOURCES’ variable has an unrecognized extension, Automake will do one of two things with it. If a suffix rule exists for turning files with the unrecognized extension into ‘.o’ files, then ‘automake’ will treat this file as it will any other source file (*note Support for Other Languages::). Otherwise, the file will be ignored as though it were a header file. The prefixes ‘dist_’ and ‘nodist_’ can be used to control whether files listed in a ‘_SOURCES’ variable are distributed. ‘dist_’ is redundant, as sources are distributed by default, but it can be specified for clarity if desired. It is possible to have both ‘dist_’ and ‘nodist_’ variants of a given ‘_SOURCES’ variable at once; this lets you easily distribute some files and not others, for instance: nodist_maude_SOURCES = nodist.c dist_maude_SOURCES = dist-me.c By default the output file (on Unix systems, the ‘.o’ file) will be put into the current build directory. However, if the option ‘subdir-objects’ is in effect in the current directory then the ‘.o’ file will be put into the subdirectory named after the source file. For instance, with ‘subdir-objects’ enabled, ‘sub/dir/file.c’ will be compiled to ‘sub/dir/file.o’. Some projects prefer or require this mode of operation. You can specify ‘subdir-objects’ in ‘AUTOMAKE_OPTIONS’ (*note Options::). When ‘subdir-objects’ is specified, and source files which lie outside the current directory tree are nevertheless specified, as in ‘foo_SOURCES = ../lib/other.c’, Automake will still remove ‘../lib/other.o’, in fact, ‘../lib/*.o’ (e.g., at ‘make clean’, even though it is arguably wrong for one subdirectory to clean in a sibling. This may or may not be changed in the future. ‘EXTRA_maude_SOURCES’ Automake needs to know the list of files you intend to compile _statically_. For one thing, this is the only way Automake has of knowing what sort of language support a given ‘Makefile.in’ requires. (There are other, more obscure reasons for this limitation as well.) This means that, for example, you can’t put a configure substitution like ‘@my_sources@’ into a ‘_SOURCES’ variable. If you intend to conditionally compile source files and use ‘configure’ to substitute the appropriate object names into, e.g., ‘_LDADD’ (see below), then you should list the corresponding source files in the ‘EXTRA_’ variable. This variable also supports ‘dist_’ and ‘nodist_’ prefixes. For instance, ‘nodist_EXTRA_maude_SOURCES’ would list extra sources that may need to be built, but should not be distributed. ‘maude_AR’ A static library is created by default by invoking ‘$(AR) $(ARFLAGS)’ followed by the name of the library and then the objects being put into the library. You can override this by setting the ‘_AR’ variable. This is usually used with C++; some C++ compilers require a special invocation in order to instantiate all the templates that should go into a library. For instance, the SGI C++ compiler likes this variable set like so: libmaude_a_AR = $(CXX) -ar -o ‘maude_LIBADD’ Extra objects can be added to a _library_ using the ‘_LIBADD’ variable. For instance, this should be used for objects determined by ‘configure’ (*note A Library::). In the case of libtool libraries, ‘maude_LIBADD’ can also refer to other libtool libraries. ‘maude_LDADD’ Extra objects (‘*.$(OBJEXT)’) and libraries (‘*.a’, ‘*.la’) can be added to a _program_ by listing them in the ‘_LDADD’ variable. For instance, this should be used for objects determined by ‘configure’ (*note Linking::). ‘_LDADD’ and ‘_LIBADD’ are inappropriate for passing program-specific linker flags (except for ‘-l’, ‘-L’, ‘-dlopen’ and ‘-dlpreopen’). Use the ‘_LDFLAGS’ variable for this purpose. For instance, if your ‘configure.ac’ uses ‘AC_PATH_XTRA’, you could link your program against the X libraries like so: maude_LDADD = $(X_PRE_LIBS) $(X_LIBS) $(X_EXTRA_LIBS) We recommend that you use ‘-l’ and ‘-L’ only when referring to third-party libraries, and give the explicit file names of any library built by your package. Doing so will ensure that ‘maude_DEPENDENCIES’ (see below) is correctly defined by default. ‘maude_LDFLAGS’ This variable is used to pass extra flags to the link step of a program or a shared library. It overrides the ‘AM_LDFLAGS’ variable, even if it is defined only in a false branch of a conditional; in other words, if ‘PROG_LDFLAGS’ is defined at all, ‘AM_LDFLAGS’ will not be used. ‘maude_LIBTOOLFLAGS’ This variable is used to pass extra options to ‘libtool’. It overrides the ‘AM_LIBTOOLFLAGS’ variable. These options are output before ‘libtool’’s ‘--mode=MODE’ option, so they should not be mode-specific options (those belong to the compiler or linker flags). *Note Libtool Flags::. ‘maude_DEPENDENCIES’ ‘EXTRA_maude_DEPENDENCIES’ It is also occasionally useful to have a target (program or library) depend on some other file that is not in fact part of that target. This can be done using the ‘_DEPENDENCIES’ variable. Each target depends on the contents of such a variable, but no further interpretation is done. Since these dependencies are associated with the link rule used to create the programs they should normally list files used by the link command. That is ‘*.$(OBJEXT)’, ‘*.a’, or ‘*.la’ files for programs; ‘*.lo’ and ‘*.la’ files for Libtool libraries; and ‘*.$(OBJEXT)’ files for static libraries. In rare cases you may need to add other kinds of files such as linker scripts, but _listing a source file in ‘_DEPENDENCIES’ is wrong_. If some source file needs to be built before all the components of a program are built, consider using the ‘BUILT_SOURCES’ variable (*note Sources::). If ‘_DEPENDENCIES’ is not supplied, it is computed by Automake. The automatically-assigned value is the contents of ‘_LDADD’ or ‘_LIBADD’, with most configure substitutions, ‘-l’, ‘-L’, ‘-dlopen’ and ‘-dlpreopen’ options removed. The configure substitutions that are left in are only ‘$(LIBOBJS)’ and ‘$(ALLOCA)’; these are left because it is known that they will not cause an invalid value for ‘_DEPENDENCIES’ to be generated. ‘_DEPENDENCIES’ is more likely used to perform conditional compilation using an ‘AC_SUBST’ variable that contains a list of objects. *Note Conditional Sources::, and *note Conditional Libtool Sources::. The ‘EXTRA_*_DEPENDENCIES’ variable may be useful for cases where you merely want to augment the ‘automake’-generated ‘_DEPENDENCIES’ variable rather than replacing it. ‘maude_LINK’ You can override the linker on a per-program basis. By default the linker is chosen according to the languages used by the program. For instance, a program that includes C++ source code would use the C++ compiler to link. The ‘_LINK’ variable must hold the name of a command that can be passed all the ‘.o’ file names and libraries to link against as arguments. Note that the name of the underlying program is _not_ passed to ‘_LINK’; typically one uses ‘$@’: maude_LINK = $(CCLD) -magic -o $@ If a ‘_LINK’ variable is not supplied, it may still be generated and used by Automake due to the use of per-target link flags such as ‘_CFLAGS’, ‘_LDFLAGS’ or ‘_LIBTOOLFLAGS’, in cases where they apply. If the variable ‘AM_V_*_LINK’ exists, it is used to output a status line in silent mode; otherwise, ‘AM_V_GEN’ is used. ‘maude_CCASFLAGS’ ‘maude_CFLAGS’ ‘maude_CPPFLAGS’ ‘maude_CXXFLAGS’ ‘maude_FFLAGS’ ‘maude_GCJFLAGS’ ‘maude_LFLAGS’ ‘maude_OBJCFLAGS’ ‘maude_OBJCXXFLAGS’ ‘maude_RFLAGS’ ‘maude_UPCFLAGS’ ‘maude_YFLAGS’ Automake allows you to set compilation flags on a per-program (or per-library) basis. A single source file can be included in several programs, and it will potentially be compiled with different flags for each program. This works for any language directly supported by Automake. These “per-target compilation flags” are ‘_CCASFLAGS’, ‘_CFLAGS’, ‘_CPPFLAGS’, ‘_CXXFLAGS’, ‘_FFLAGS’, ‘_GCJFLAGS’, ‘_LFLAGS’, ‘_OBJCFLAGS’, ‘_OBJCXXFLAGS’, ‘_RFLAGS’, ‘_UPCFLAGS’, and ‘_YFLAGS’. When using a per-target compilation flag, Automake will choose a different name for the intermediate object files. Ordinarily a file like ‘sample.c’ will be compiled to produce ‘sample.o’. However, if the program’s ‘_CFLAGS’ variable is set, then the object file will be named, for instance, ‘maude-sample.o’. (See also *note Renamed Objects::.) In compilations with per-target flags, the ordinary ‘AM_’ form of the flags variable is _not_ automatically included in the compilation (however, the user form of the variable _is_ included). So for instance, if you want the hypothetical ‘maude’ compilations to also use the value of ‘AM_CFLAGS’, you would need to write: maude_CFLAGS = ... your flags ... $(AM_CFLAGS) *Note Flag Variables Ordering::, for more discussion about the interaction between user variables, ‘AM_’ shadow variables, and per-target variables. ‘maude_SHORTNAME’ On some platforms the allowable file names are very short. In order to support these systems and per-target compilation flags at the same time, Automake allows you to set a “short name” that will influence how intermediate object files are named. For instance, in the following example, bin_PROGRAMS = maude maude_CPPFLAGS = -DSOMEFLAG maude_SHORTNAME = m maude_SOURCES = sample.c ... the object file would be named ‘m-sample.o’ rather than ‘maude-sample.o’. This facility is rarely needed in practice, and we recommend avoiding it until you find it is required.  File: automake.info, Node: Default _SOURCES, Next: LIBOBJS, Prev: Program and Library Variables, Up: Programs 8.5 Default ‘_SOURCES’ ====================== ‘_SOURCES’ variables are used to specify source files of programs (*note A Program::), libraries (*note A Library::), and Libtool libraries (*note A Shared Library::). When no such variable is specified for a target, Automake will define one itself. The default is to compile a single C file whose base name is the name of the target itself, with any extension replaced by ‘AM_DEFAULT_SOURCE_EXT’, which defaults to ‘.c’. For example if you have the following somewhere in your ‘Makefile.am’ with no corresponding ‘libfoo_a_SOURCES’: lib_LIBRARIES = libfoo.a sub/libc++.a ‘libfoo.a’ will be built using a default source file named ‘libfoo.c’, and ‘sub/libc++.a’ will be built from ‘sub/libc++.c’. (In older versions ‘sub/libc++.a’ would be built from ‘sub_libc___a.c’, i.e., the default source was the canonicalized name of the target, with ‘.c’ appended. We believe the new behavior is more sensible, but for backward compatibility ‘automake’ will use the old name if a file or a rule with that name exists and ‘AM_DEFAULT_SOURCE_EXT’ is not used.) Default sources are mainly useful in test suites, when building many test programs each from a single source. For instance, in check_PROGRAMS = test1 test2 test3 AM_DEFAULT_SOURCE_EXT = .cpp ‘test1’, ‘test2’, and ‘test3’ will be built from ‘test1.cpp’, ‘test2.cpp’, and ‘test3.cpp’. Without the last line, they will be built from ‘test1.c’, ‘test2.c’, and ‘test3.c’. Another case where this is convenient is building many Libtool modules (‘moduleN.la’), each defined in its own file (‘moduleN.c’). AM_LDFLAGS = -module lib_LTLIBRARIES = module1.la module2.la module3.la Finally, there is one situation where this default source computation needs to be avoided: when a target should not be built from sources. We already saw such an example in *note true::; this happens when all the constituents of a target have already been compiled and just need to be combined using a ‘_LDADD’ variable. Then it is necessary to define an empty ‘_SOURCES’ variable, so that ‘automake’ does not compute a default. bin_PROGRAMS = target target_SOURCES = target_LDADD = libmain.a libmisc.a  File: automake.info, Node: LIBOBJS, Next: Program Variables, Prev: Default _SOURCES, Up: Programs 8.6 Special handling for ‘LIBOBJS’ and ‘ALLOCA’ =============================================== The ‘$(LIBOBJS)’ and ‘$(ALLOCA)’ variables list object files that should be compiled into the project to provide an implementation for functions that are missing or broken on the host system. They are substituted by ‘configure’. These variables are defined by Autoconf macros such as ‘AC_LIBOBJ’, ‘AC_REPLACE_FUNCS’ (*note Generic Function Checks: (autoconf)Generic Functions.), or ‘AC_FUNC_ALLOCA’ (*note Particular Function Checks: (autoconf)Particular Functions.). Many other Autoconf macros call ‘AC_LIBOBJ’ or ‘AC_REPLACE_FUNCS’ to populate ‘$(LIBOBJS)’. Using these variables is very similar to doing conditional compilation using ‘AC_SUBST’ variables, as described in *note Conditional Sources::. That is, when building a program, ‘$(LIBOBJS)’ and ‘$(ALLOCA)’ should be added to the associated ‘*_LDADD’ variable, or to the ‘*_LIBADD’ variable when building a library. However there is no need to list the corresponding sources in ‘EXTRA_*_SOURCES’ nor to define ‘*_DEPENDENCIES’. Automake automatically adds ‘$(LIBOBJS)’ and ‘$(ALLOCA)’ to the dependencies, and it will discover the list of corresponding source files automatically (by tracing the invocations of the ‘AC_LIBSOURCE’ Autoconf macros). If you have already defined ‘*_DEPENDENCIES’ explicitly for an unrelated reason, then you either need to add these variables manually, or use ‘EXTRA_*_DEPENDENCIES’ instead of ‘*_DEPENDENCIES’. These variables are usually used to build a portability library that is linked with all the programs of the project. We now review a sample setup. First, ‘configure.ac’ contains some checks that affect either ‘LIBOBJS’ or ‘ALLOCA’. # configure.ac ... AC_CONFIG_LIBOBJ_DIR([lib]) ... AC_FUNC_MALLOC dnl May add malloc.$(OBJEXT) to LIBOBJS AC_FUNC_MEMCMP dnl May add memcmp.$(OBJEXT) to LIBOBJS AC_REPLACE_FUNCS([strdup]) dnl May add strdup.$(OBJEXT) to LIBOBJS AC_FUNC_ALLOCA dnl May add alloca.$(OBJEXT) to ALLOCA ... AC_CONFIG_FILES([ lib/Makefile src/Makefile ]) AC_OUTPUT The ‘AC_CONFIG_LIBOBJ_DIR’ tells Autoconf that the source files of these object files are to be found in the ‘lib/’ directory. Automake can also use this information, otherwise it expects the source files are to be in the directory where the ‘$(LIBOBJS)’ and ‘$(ALLOCA)’ variables are used. The ‘lib/’ directory should therefore contain ‘malloc.c’, ‘memcmp.c’, ‘strdup.c’, ‘alloca.c’. Here is its ‘Makefile.am’: # lib/Makefile.am noinst_LIBRARIES = libcompat.a libcompat_a_SOURCES = libcompat_a_LIBADD = $(LIBOBJS) $(ALLOCA) The library can have any name, of course, and anyway it is not going to be installed: it just holds the replacement versions of the missing or broken functions so we can later link them in. Many projects also include extra functions, specific to the project, in that library: they are simply added on the ‘_SOURCES’ line. There is a small trap here, though: ‘$(LIBOBJS)’ and ‘$(ALLOCA)’ might be empty, and building an empty library is not portable. You should ensure that there is always something to put in ‘libcompat.a’. Most projects will also add some utility functions in that directory, and list them in ‘libcompat_a_SOURCES’, so in practice ‘libcompat.a’ cannot be empty. Finally here is how this library could be used from the ‘src/’ directory. # src/Makefile.am # Link all programs in this directory with libcompat.a LDADD = ../lib/libcompat.a bin_PROGRAMS = tool1 tool2 ... tool1_SOURCES = ... tool2_SOURCES = ... When option ‘subdir-objects’ is not used, as in the above example, the variables ‘$(LIBOBJS)’ or ‘$(ALLOCA)’ can only be used in the directory where their sources lie. E.g., here it would be wrong to use ‘$(LIBOBJS)’ or ‘$(ALLOCA)’ in ‘src/Makefile.am’. However if both ‘subdir-objects’ and ‘AC_CONFIG_LIBOBJ_DIR’ are used, it is OK to use these variables in other directories. For instance ‘src/Makefile.am’ could be changed as follows. # src/Makefile.am AUTOMAKE_OPTIONS = subdir-objects LDADD = $(LIBOBJS) $(ALLOCA) bin_PROGRAMS = tool1 tool2 ... tool1_SOURCES = ... tool2_SOURCES = ... Because ‘$(LIBOBJS)’ and ‘$(ALLOCA)’ contain object file names that end with ‘.$(OBJEXT)’, they are not suitable for Libtool libraries (where the expected object extension is ‘.lo’): ‘LTLIBOBJS’ and ‘LTALLOCA’ should be used instead. ‘LTLIBOBJS’ is defined automatically by Autoconf and should not be defined by hand (as in the past), however at the time of writing ‘LTALLOCA’ still needs to be defined from ‘ALLOCA’ manually. *Note ‘AC_LIBOBJ’ vs. ‘LIBOBJS’: (autoconf)AC_LIBOBJ vs LIBOBJS.  File: automake.info, Node: Program Variables, Next: Yacc and Lex, Prev: LIBOBJS, Up: Programs 8.7 Variables used when building a program ========================================== Occasionally it is useful to know which ‘Makefile’ variables Automake uses for compilations, and in which order (*note Flag Variables Ordering::); for instance, you might need to do your own compilation in some special cases. Some variables are inherited from Autoconf; these are ‘CC’, ‘CFLAGS’, ‘CPPFLAGS’, ‘DEFS’, ‘LDFLAGS’, and ‘LIBS’. There are some additional variables that Automake defines on its own: ‘AM_CPPFLAGS’ The contents of this variable are passed to every compilation that invokes the C preprocessor; it is a list of arguments to the preprocessor. For instance, ‘-I’ and ‘-D’ options should be listed here. Automake already provides some ‘-I’ options automatically, in a separate variable that is also passed to every compilation that invokes the C preprocessor. In particular it generates ‘-I.’, ‘-I$(srcdir)’, and a ‘-I’ pointing to the directory holding ‘config.h’ (if you’ve used ‘AC_CONFIG_HEADERS’). You can disable the default ‘-I’ options using the ‘nostdinc’ option. When a file to be included is generated during the build and not part of a distribution tarball, its location is under ‘$(builddir)’, not under ‘$(srcdir)’. This matters especially for packages that use header files placed in sub-directories and want to allow builds outside the source tree (*note VPATH Builds::). In that case we recommend using a pair of ‘-I’ options, such as, e.g., ‘-Isome/subdir -I$(srcdir)/some/subdir’ or ‘-I$(top_builddir)/some/subdir -I$(top_srcdir)/some/subdir’. Note that the reference to the build tree should come before the reference to the source tree, so that accidentally leftover generated files in the source directory are ignored. ‘AM_CPPFLAGS’ is ignored in preference to a per-executable (or per-library) ‘_CPPFLAGS’ variable if it is defined. ‘INCLUDES’ This does the same job as ‘AM_CPPFLAGS’ (or any per-target ‘_CPPFLAGS’ variable if it is used). It is an older name for the same functionality. This variable is deprecated; we suggest using ‘AM_CPPFLAGS’ and per-target ‘_CPPFLAGS’ instead. ‘AM_CFLAGS’ This is the variable the ‘Makefile.am’ author can use to pass in additional C compiler flags. In some situations, this is not used, in preference to the per-executable (or per-library) ‘_CFLAGS’. ‘COMPILE’ This is the command used to compile a C source file. The file name is appended to form the complete command line. ‘AM_LDFLAGS’ This is the variable the ‘Makefile.am’ author can use to pass in additional linker flags. In some situations, this is not used, in preference to the per-executable (or per-library) ‘_LDFLAGS’. ‘LINK’ This is the command used to link a C program. It already includes ‘-o $@’ and the usual variable references (for instance, ‘CFLAGS’); it takes as “arguments” the names of the object files and libraries to link in. This variable is not used when the linker is overridden with a per-target ‘_LINK’ variable or per-target flags cause Automake to define such a ‘_LINK’ variable.  File: automake.info, Node: Yacc and Lex, Next: C++ Support, Prev: Program Variables, Up: Programs 8.8 Yacc and Lex support ======================== Automake has somewhat idiosyncratic support for Yacc and Lex. Automake assumes that the ‘.c’ file generated by ‘yacc’ or ‘lex’ should be named using the basename of the input file. That is, for a Yacc source file ‘foo.y’, Automake will cause the intermediate file to be named ‘foo.c’ (as opposed to ‘y.tab.c’, which is more traditional). The extension of a Yacc source file is used to determine the extension of the resulting C or C++ source and header files. Be aware that header files are generated only when the option ‘-d’ is given to Yacc; see below for more information about this flag, and how to specify it. Files with the extension ‘.y’ will thus be turned into ‘.c’ sources and ‘.h’ headers; likewise, ‘.yy’ will become ‘.cc’ and ‘.hh’, ‘.y++’ will become ‘c++’ and ‘h++’, ‘.yxx’ will become ‘.cxx’ and ‘.hxx’, and ‘.ypp’ will become ‘.cpp’ and ‘.hpp’. Similarly, Lex source files can be used to generate C or C++; the extensions ‘.l’, ‘.ll’, ‘.l++’, ‘.lxx’, and ‘.lpp’ are recognized. You should never explicitly mention the intermediate (C or C++) file in any ‘SOURCES’ variable; only list the source file. The intermediate files generated by ‘yacc’ (or ‘lex’) will be included in any distribution that is made. That way the user doesn’t need to have ‘yacc’ or ‘lex’. If a Yacc source file is seen, then your ‘configure.ac’ must define the variable ‘YACC’. This is most easily done by invoking the macro ‘AC_PROG_YACC’ (*note Particular Program Checks: (autoconf)Particular Programs.). When ‘yacc’ is invoked, it is passed ‘AM_YFLAGS’ and ‘YFLAGS’. The latter is a user variable and the former is intended for the ‘Makefile.am’ author. ‘AM_YFLAGS’ is usually used to pass the ‘-d’ option to ‘yacc’. Automake knows what this means and will automatically adjust its rules to update and distribute the header file built by ‘yacc -d’. Caveat: ‘automake’ recognizes ‘-d’ in ‘AM_YFLAGS’ only if it is not clustered with other options; for example, it won’t be recognized if ‘AM_YFLAGS’ is ‘-dt’, but it will be if ‘AM_YFLAGS’ is ‘-d -t’ or ‘-t -d’. What Automake cannot guess, though, is where this header will be used: it is up to you to ensure the header gets built before it is first used. Typically this is necessary in order for dependency tracking to work when the header is included by another file. The common solution is listing the header file in ‘BUILT_SOURCES’ (*note Sources::) as follows. BUILT_SOURCES = parser.h AM_YFLAGS = -d bin_PROGRAMS = foo foo_SOURCES = ... parser.y ... If a Lex source file is seen, then your ‘configure.ac’ must define the variable ‘LEX’. You can use ‘AC_PROG_LEX’ to do this (*note Particular Program Checks: (autoconf)Particular Programs.), but using the ‘AM_PROG_LEX’ macro (*note Macros::) is recommended. When ‘lex’ is invoked, it is passed ‘AM_LFLAGS’ and ‘LFLAGS’. The latter is a user variable and the former is intended for the ‘Makefile.am’ author. When ‘AM_MAINTAINER_MODE’ (*note maintainer-mode::) is in effect, the rebuild rules for distributed Yacc and Lex sources are only used when ‘maintainer-mode’ is enabled, or when the files have been erased. When Yacc or Lex sources are used, ‘automake -a’ automatically installs an auxiliary program called ‘ylwrap’ in your package (*note Auxiliary Programs::). This program is used by the build rules to rename the output of these tools, and makes it possible to include multiple ‘yacc’ (or ‘lex’) source files in a single directory. This is necessary because Yacc’s output file name is fixed, and a parallel make could invoke more than one instance of ‘yacc’ simultaneously. * Menu: * Linking Multiple Yacc Parsers:: 8.8.1 Linking Multiple Yacc Parsers -----------------------------------  File: automake.info, Node: Linking Multiple Yacc Parsers, Up: Yacc and Lex For ‘yacc’, simply managing locking as with ‘ylwrap’ is insufficient. The output of ‘yacc’ always uses the same symbol names internally, so it isn’t possible to link two ‘yacc’ parsers into the same executable. We recommend using the following renaming hack used in ‘gdb’: #define yymaxdepth c_maxdepth #define yyparse c_parse #define yylex c_lex #define yyerror c_error #define yylval c_lval #define yychar c_char #define yydebug c_debug #define yypact c_pact #define yyr1 c_r1 #define yyr2 c_r2 #define yydef c_def #define yychk c_chk #define yypgo c_pgo #define yyact c_act #define yyexca c_exca #define yyerrflag c_errflag #define yynerrs c_nerrs #define yyps c_ps #define yypv c_pv #define yys c_s #define yy_yys c_yys #define yystate c_state #define yytmp c_tmp #define yyv c_v #define yy_yyv c_yyv #define yyval c_val #define yylloc c_lloc #define yyreds c_reds #define yytoks c_toks #define yylhs c_yylhs #define yylen c_yylen #define yydefred c_yydefred #define yydgoto c_yydgoto #define yysindex c_yysindex #define yyrindex c_yyrindex #define yygindex c_yygindex #define yytable c_yytable #define yycheck c_yycheck #define yyname c_yyname #define yyrule c_yyrule For each define, replace the ‘c_’ prefix with whatever you like. These defines work for ‘bison’, ‘byacc’, and traditional ‘yacc’s. If you find a parser generator that uses a symbol not covered here, please report the new name so it can be added to the list.  File: automake.info, Node: C++ Support, Next: Objective C Support, Prev: Yacc and Lex, Up: Programs 8.9 C++ Support =============== Automake includes full support for C++. Any package including C++ code must define the output variable ‘CXX’ in ‘configure.ac’; the simplest way to do this is to use the ‘AC_PROG_CXX’ macro (*note Particular Program Checks: (autoconf)Particular Programs.). A few additional variables are defined when a C++ source file is seen: ‘CXX’ The name of the C++ compiler. ‘CXXFLAGS’ Any flags to pass to the C++ compiler. ‘AM_CXXFLAGS’ The maintainer’s variant of ‘CXXFLAGS’. ‘CXXCOMPILE’ The command used to compile a C++ source file. The file name is appended to form the complete command line. ‘CXXLINK’ The command used to link a C++ program.  File: automake.info, Node: Objective C Support, Next: Objective C++ Support, Prev: C++ Support, Up: Programs 8.10 Objective C Support ======================== Automake includes some support for Objective C. Any package including Objective C code must define the output variable ‘OBJC’ in ‘configure.ac’; the simplest way to do this is to use the ‘AC_PROG_OBJC’ macro (*note Particular Program Checks: (autoconf)Particular Programs.). A few additional variables are defined when an Objective C source file is seen: ‘OBJC’ The name of the Objective C compiler. ‘OBJCFLAGS’ Any flags to pass to the Objective C compiler. ‘AM_OBJCFLAGS’ The maintainer’s variant of ‘OBJCFLAGS’. ‘OBJCCOMPILE’ The command used to compile an Objective C source file. The file name is appended to form the complete command line. ‘OBJCLINK’ The command used to link an Objective C program.  File: automake.info, Node: Objective C++ Support, Next: Unified Parallel C Support, Prev: Objective C Support, Up: Programs 8.11 Objective C++ Support ========================== Automake includes some support for Objective C++. Any package including Objective C++ code must define the output variable ‘OBJCXX’ in ‘configure.ac’; the simplest way to do this is to use the ‘AC_PROG_OBJCXX’ macro (*note Particular Program Checks: (autoconf)Particular Programs.). A few additional variables are defined when an Objective C++ source file is seen: ‘OBJCXX’ The name of the Objective C++ compiler. ‘OBJCXXFLAGS’ Any flags to pass to the Objective C++ compiler. ‘AM_OBJCXXFLAGS’ The maintainer’s variant of ‘OBJCXXFLAGS’. ‘OBJCXXCOMPILE’ The command used to compile an Objective C++ source file. The file name is appended to form the complete command line. ‘OBJCXXLINK’ The command used to link an Objective C++ program.  File: automake.info, Node: Unified Parallel C Support, Next: Assembly Support, Prev: Objective C++ Support, Up: Programs 8.12 Unified Parallel C Support =============================== Automake includes some support for Unified Parallel C. Any package including Unified Parallel C code must define the output variable ‘UPC’ in ‘configure.ac’; the simplest way to do this is to use the ‘AM_PROG_UPC’ macro (*note Public Macros::). A few additional variables are defined when a Unified Parallel C source file is seen: ‘UPC’ The name of the Unified Parallel C compiler. ‘UPCFLAGS’ Any flags to pass to the Unified Parallel C compiler. ‘AM_UPCFLAGS’ The maintainer’s variant of ‘UPCFLAGS’. ‘UPCCOMPILE’ The command used to compile a Unified Parallel C source file. The file name is appended to form the complete command line. ‘UPCLINK’ The command used to link a Unified Parallel C program.  File: automake.info, Node: Assembly Support, Next: Fortran 77 Support, Prev: Unified Parallel C Support, Up: Programs 8.13 Assembly Support ===================== Automake includes some support for assembly code. There are two forms of assembler files: normal (‘*.s’) and preprocessed by ‘CPP’ (‘*.S’ or ‘*.sx’). The variable ‘CCAS’ holds the name of the compiler used to build assembly code. This compiler must work a bit like a C compiler; in particular it must accept ‘-c’ and ‘-o’. The values of ‘CCASFLAGS’ and ‘AM_CCASFLAGS’ (or its per-target definition) is passed to the compilation. For preprocessed files, ‘DEFS’, ‘DEFAULT_INCLUDES’, ‘INCLUDES’, ‘CPPFLAGS’ and ‘AM_CPPFLAGS’ are also used. The autoconf macro ‘AM_PROG_AS’ will define ‘CCAS’ and ‘CCASFLAGS’ for you (unless they are already set, it simply sets ‘CCAS’ to the C compiler and ‘CCASFLAGS’ to the C compiler flags), but you are free to define these variables by other means. Only the suffixes ‘.s’, ‘.S’, and ‘.sx’ are recognized by ‘automake’ as being files containing assembly code.  File: automake.info, Node: Fortran 77 Support, Next: Fortran 9x Support, Prev: Assembly Support, Up: Programs 8.14 Fortran 77 Support ======================= Automake includes full support for Fortran 77. Any package including Fortran 77 code must define the output variable ‘F77’ in ‘configure.ac’; the simplest way to do this is to use the ‘AC_PROG_F77’ macro (*note Particular Program Checks: (autoconf)Particular Programs.). A few additional variables are defined when a Fortran 77 source file is seen: ‘F77’ The name of the Fortran 77 compiler. ‘FFLAGS’ Any flags to pass to the Fortran 77 compiler. ‘AM_FFLAGS’ The maintainer’s variant of ‘FFLAGS’. ‘RFLAGS’ Any flags to pass to the Ratfor compiler. ‘AM_RFLAGS’ The maintainer’s variant of ‘RFLAGS’. ‘F77COMPILE’ The command used to compile a Fortran 77 source file. The file name is appended to form the complete command line. ‘FLINK’ The command used to link a pure Fortran 77 program or shared library. Automake can handle preprocessing Fortran 77 and Ratfor source files in addition to compiling them(1). Automake also contains some support for creating programs and shared libraries that are a mixture of Fortran 77 and other languages (*note Mixing Fortran 77 With C and C++::). These issues are covered in the following sections. * Menu: * Preprocessing Fortran 77:: Preprocessing Fortran 77 sources * Compiling Fortran 77 Files:: Compiling Fortran 77 sources * Mixing Fortran 77 With C and C++:: Mixing Fortran 77 With C and C++ ---------- Footnotes ---------- (1) Much, if not most, of the information in the following sections pertaining to preprocessing Fortran 77 programs was taken almost verbatim from *note Catalogue of Rules: (make)Catalogue of Rules.  File: automake.info, Node: Preprocessing Fortran 77, Next: Compiling Fortran 77 Files, Up: Fortran 77 Support 8.14.1 Preprocessing Fortran 77 ------------------------------- ‘N.f’ is made automatically from ‘N.F’ or ‘N.r’. This rule runs just the preprocessor to convert a preprocessable Fortran 77 or Ratfor source file into a strict Fortran 77 source file. The precise command used is as follows: ‘.F’ ‘$(F77) -F $(DEFS) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_FFLAGS) $(FFLAGS)’ ‘.r’ ‘$(F77) -F $(AM_FFLAGS) $(FFLAGS) $(AM_RFLAGS) $(RFLAGS)’  File: automake.info, Node: Compiling Fortran 77 Files, Next: Mixing Fortran 77 With C and C++, Prev: Preprocessing Fortran 77, Up: Fortran 77 Support 8.14.2 Compiling Fortran 77 Files --------------------------------- ‘N.o’ is made automatically from ‘N.f’, ‘N.F’ or ‘N.r’ by running the Fortran 77 compiler. The precise command used is as follows: ‘.f’ ‘$(F77) -c $(AM_FFLAGS) $(FFLAGS)’ ‘.F’ ‘$(F77) -c $(DEFS) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_FFLAGS) $(FFLAGS)’ ‘.r’ ‘$(F77) -c $(AM_FFLAGS) $(FFLAGS) $(AM_RFLAGS) $(RFLAGS)’  File: automake.info, Node: Mixing Fortran 77 With C and C++, Prev: Compiling Fortran 77 Files, Up: Fortran 77 Support 8.14.3 Mixing Fortran 77 With C and C++ --------------------------------------- Automake currently provides _limited_ support for creating programs and shared libraries that are a mixture of Fortran 77 and C and/or C++. However, there are many other issues related to mixing Fortran 77 with other languages that are _not_ (currently) handled by Automake, but that are handled by other packages(1). Automake can help in two ways: 1. Automatic selection of the linker depending on which combinations of source code. 2. Automatic selection of the appropriate linker flags (e.g., ‘-L’ and ‘-l’) to pass to the automatically selected linker in order to link in the appropriate Fortran 77 intrinsic and run-time libraries. These extra Fortran 77 linker flags are supplied in the output variable ‘FLIBS’ by the ‘AC_F77_LIBRARY_LDFLAGS’ Autoconf macro. *Note Fortran Compiler Characteristics: (autoconf)Fortran Compiler. If Automake detects that a program or shared library (as mentioned in some ‘_PROGRAMS’ or ‘_LTLIBRARIES’ primary) contains source code that is a mixture of Fortran 77 and C and/or C++, then it requires that the macro ‘AC_F77_LIBRARY_LDFLAGS’ be called in ‘configure.ac’, and that either ‘$(FLIBS)’ appear in the appropriate ‘_LDADD’ (for programs) or ‘_LIBADD’ (for shared libraries) variables. It is the responsibility of the person writing the ‘Makefile.am’ to make sure that ‘$(FLIBS)’ appears in the appropriate ‘_LDADD’ or ‘_LIBADD’ variable. For example, consider the following ‘Makefile.am’: bin_PROGRAMS = foo foo_SOURCES = main.cc foo.f foo_LDADD = libfoo.la $(FLIBS) pkglib_LTLIBRARIES = libfoo.la libfoo_la_SOURCES = bar.f baz.c zardoz.cc libfoo_la_LIBADD = $(FLIBS) In this case, Automake will insist that ‘AC_F77_LIBRARY_LDFLAGS’ is mentioned in ‘configure.ac’. Also, if ‘$(FLIBS)’ hadn’t been mentioned in ‘foo_LDADD’ and ‘libfoo_la_LIBADD’, then Automake would have issued a warning. * Menu: * How the Linker is Chosen:: Automatic linker selection ---------- Footnotes ---------- (1) For example, the cfortran package (https://www-zeus.desy.de/~burow/cfortran/) addresses all of these inter-language issues, and runs under nearly all Fortran 77, C and C++ compilers on nearly all platforms. However, ‘cfortran’ is not yet Free Software, but it will be in the next major release.  File: automake.info, Node: How the Linker is Chosen, Up: Mixing Fortran 77 With C and C++ 8.14.3.1 How the Linker is Chosen ................................. When a program or library mixes several languages, Automake chooses the linker according to the following priorities. (The names in parentheses are the variables containing the link command.) 1. Native Java (‘GCJLINK’) 2. Objective C++ (‘OBJCXXLINK’) 3. C++ (‘CXXLINK’) 4. Fortran 77 (‘F77LINK’) 5. Fortran (‘FCLINK’) 6. Objective C (‘OBJCLINK’) 7. Unified Parallel C (‘UPCLINK’) 8. C (‘LINK’) For example, if Fortran 77, C and C++ source code is compiled into a program, then the C++ linker will be used. In this case, if the C or Fortran 77 linkers required any special libraries that weren’t included by the C++ linker, then they must be manually added to an ‘_LDADD’ or ‘_LIBADD’ variable by the user writing the ‘Makefile.am’. Automake only looks at the file names listed in ‘_SOURCES’ variables to choose the linker, and defaults to the C linker. Sometimes this is inconvenient because you are linking against a library written in another language and would like to set the linker more appropriately. *Note Libtool Convenience Libraries::, for a trick with ‘nodist_EXTRA_..._SOURCES’. A per-target ‘_LINK’ variable will override the above selection. Per-target link flags will cause Automake to write a per-target ‘_LINK’ variable according to the language chosen as above.  File: automake.info, Node: Fortran 9x Support, Next: Java Support with gcj, Prev: Fortran 77 Support, Up: Programs 8.15 Fortran 9x Support ======================= Automake includes support for Fortran 9x. Any package including Fortran 9x code must define the output variable ‘FC’ in ‘configure.ac’; the simplest way to do this is to use the ‘AC_PROG_FC’ macro (*note Particular Program Checks: (autoconf)Particular Programs.). A few additional variables are defined when a Fortran 9x source file is seen: ‘FC’ The name of the Fortran 9x compiler. ‘FCFLAGS’ Any flags to pass to the Fortran 9x compiler. ‘AM_FCFLAGS’ The maintainer’s variant of ‘FCFLAGS’. ‘FCCOMPILE’ The command used to compile a Fortran 9x source file. The file name is appended to form the complete command line. ‘FCLINK’ The command used to link a pure Fortran 9x program or shared library. * Menu: * Compiling Fortran 9x Files:: Compiling Fortran 9x sources  File: automake.info, Node: Compiling Fortran 9x Files, Up: Fortran 9x Support 8.15.1 Compiling Fortran 9x Files --------------------------------- ‘FILE.o’ is made automatically from ‘FILE.f90’, ‘FILE.f95’, ‘FILE.f03’, or ‘FILE.f08’ by running the Fortran 9x compiler. The precise command used is as follows: ‘.f90’ ‘$(FC) $(AM_FCFLAGS) $(FCFLAGS) -c $(FCFLAGS_f90) $<’ ‘.f95’ ‘$(FC) $(AM_FCFLAGS) $(FCFLAGS) -c $(FCFLAGS_f95) $<’ ‘.f03’ ‘$(FC) $(AM_FCFLAGS) $(FCFLAGS) -c $(FCFLAGS_f03) $<’ ‘.f08’ ‘$(FC) $(AM_FCFLAGS) $(FCFLAGS) -c $(FCFLAGS_f08) $<’  File: automake.info, Node: Java Support with gcj, Next: Vala Support, Prev: Fortran 9x Support, Up: Programs 8.16 Compiling Java sources using gcj ===================================== Automake includes support for natively compiled Java, using ‘gcj’, the Java front end to the GNU Compiler Collection (rudimentary support for compiling Java to bytecode using the ‘javac’ compiler is also present, _albeit deprecated_; *note Java::). Any package including Java code to be compiled must define the output variable ‘GCJ’ in ‘configure.ac’; the variable ‘GCJFLAGS’ must also be defined somehow (either in ‘configure.ac’ or ‘Makefile.am’). The simplest way to do this is to use the ‘AM_PROG_GCJ’ macro. By default, programs including Java source files are linked with ‘gcj’. As always, the contents of ‘AM_GCJFLAGS’ are passed to every compilation invoking ‘gcj’ (in its role as an ahead-of-time compiler, when invoking it to create ‘.class’ files, ‘AM_JAVACFLAGS’ is used instead). If it is necessary to pass options to ‘gcj’ from ‘Makefile.am’, this variable, and not the user variable ‘GCJFLAGS’, should be used. ‘gcj’ can be used to compile ‘.java’, ‘.class’, ‘.zip’, or ‘.jar’ files. When linking, ‘gcj’ requires that the main class be specified using the ‘--main=’ option. The easiest way to do this is to use the ‘_LDFLAGS’ variable for the program.  File: automake.info, Node: Vala Support, Next: Support for Other Languages, Prev: Java Support with gcj, Up: Programs 8.17 Vala Support ================= Automake provides initial support for Vala (). This requires valac version 0.7.0 or later, and currently requires the user to use GNU ‘make’. foo_SOURCES = foo.vala bar.vala zardoz.c Any ‘.vala’ file listed in a ‘_SOURCES’ variable will be compiled into C code by the Vala compiler. The generated ‘.c’ files are distributed. The end user does not need to have a Vala compiler installed. Automake ships with an Autoconf macro called ‘AM_PROG_VALAC’ that will locate the Vala compiler and optionally check its version number. -- Macro: AM_PROG_VALAC ([MINIMUM-VERSION], [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND]) Search for a Vala compiler in ‘PATH’. If it is found, the variable ‘VALAC’ is set to point to it (see below for more details). This macro takes three optional arguments. The first argument, if present, is the minimum version of the Vala API required to compile this package. For Vala releases, this is the same as the major and minor release number; e.g., when ‘valac --version’ reports ‘0.48.7’, ‘valac --api-version’ reports ‘0.48’. If a compiler is found and satisfies MINIMUM-VERSION, then ACTION-IF-FOUND is run (this defaults to do nothing). Otherwise, ACTION-IF-NOT-FOUND is run. If ACTION-IF-NOT-FOUND is not specified, the default value is to print a warning in case no compiler is found, or if a too-old version of the compiler is found. There are a few variables that are used when compiling Vala sources: ‘VALAC’ Absolute path to the Vala compiler, or simply ‘valac’ if no suitable Vala compiler could be found at configure runtime. ‘VALAFLAGS’ Additional arguments for the Vala compiler. ‘AM_VALAFLAGS’ The maintainer’s variant of ‘VALAFLAGS’. lib_LTLIBRARIES = libfoo.la libfoo_la_SOURCES = foo.vala Note that currently, you cannot use per-target ‘*_VALAFLAGS’ (*note Renamed Objects::) to produce different C files from one Vala source file.  File: automake.info, Node: Support for Other Languages, Next: Dependencies, Prev: Vala Support, Up: Programs 8.18 Support for Other Languages ================================ Automake currently only includes full support for C, C++ (*note C++ Support::), Objective C (*note Objective C Support::), Objective C++ (*note Objective C++ Support::), Fortran 77 (*note Fortran 77 Support::), Fortran 9x (*note Fortran 9x Support::), and Java (*note Java Support with gcj::). There is only rudimentary support for other languages, support for which will be improved based on user demand. Some limited support for adding your own languages is available via the suffix rule handling (*note Suffixes::).  File: automake.info, Node: Dependencies, Next: EXEEXT, Prev: Support for Other Languages, Up: Programs 8.19 Automatic dependency tracking ================================== As a developer it is often painful to continually update the ‘Makefile.am’ whenever the include-file dependencies change in a project. Automake supplies a way to automatically track dependency changes (*note Dependency Tracking::). Automake always uses complete dependencies for a compilation, including system headers. Automake’s model is that dependency computation should be a side effect of the build. To this end, dependencies are computed by running all compilations through a special wrapper program called ‘depcomp’. ‘depcomp’ understands how to coax many different C and C++ compilers into generating dependency information in the format it requires. ‘automake -a’ will install ‘depcomp’ into your source tree for you. If ‘depcomp’ can’t figure out how to properly invoke your compiler, dependency tracking will simply be disabled for your build. Experience with earlier versions of Automake (*note Dependency Tracking Evolution: (automake-history)Dependency Tracking Evolution.) taught us that it is not reliable to generate dependencies only on the maintainer’s system, as configurations vary too much. So instead Automake implements dependency tracking at build time. Automatic dependency tracking can be suppressed by putting ‘no-dependencies’ in the variable ‘AUTOMAKE_OPTIONS’, or passing ‘no-dependencies’ as an argument to ‘AM_INIT_AUTOMAKE’ (this should be the preferred way). Or, you can invoke ‘automake’ with the ‘-i’ option. Dependency tracking is enabled by default. The person building your package also can choose to disable dependency tracking by configuring with ‘--disable-dependency-tracking’.  File: automake.info, Node: EXEEXT, Prev: Dependencies, Up: Programs 8.20 Support for executable extensions ====================================== On some platforms, such as Windows, executables are expected to have an extension such as ‘.exe’. On these platforms, some compilers (GCC among them) will automatically generate ‘foo.exe’ when asked to generate ‘foo’. Automake provides mostly-transparent support for this. Unfortunately _mostly_ doesn’t yet mean _fully_. Until the English dictionary is revised, you will have to assist Automake if your package must support those platforms. One thing you must be aware of is that, internally, Automake rewrites something like this: bin_PROGRAMS = liver to this: bin_PROGRAMS = liver$(EXEEXT) The targets Automake generates are likewise given the ‘$(EXEEXT)’ extension. The variables ‘TESTS’ and ‘XFAIL_TESTS’ (*note Simple Tests::) are also rewritten if they contain filenames that have been declared as programs in the same ‘Makefile’. (This is mostly useful when some programs from ‘check_PROGRAMS’ are listed in ‘TESTS’.) However, Automake cannot apply this rewriting to ‘configure’ substitutions. This means that if you are conditionally building a program using such a substitution, then your ‘configure.ac’ must take care to add ‘$(EXEEXT)’ when constructing the output variable. Sometimes maintainers like to write an explicit link rule for their program. Without executable extension support, this is easy—you simply write a rule whose target is the name of the program. However, when executable extension support is enabled, you must instead add the ‘$(EXEEXT)’ suffix. This might be a nuisance for maintainers who know their package will never run on a platform that has executable extensions. For those maintainers, the ‘no-exeext’ option (*note Options::) will disable this feature. This works in a fairly ugly way; if ‘no-exeext’ is seen, then the presence of a rule for a target named ‘foo’ in ‘Makefile.am’ will override an ‘automake’-generated rule for ‘foo$(EXEEXT)’. Without the ‘no-exeext’ option, this use will give a diagnostic.  File: automake.info, Node: Other Objects, Next: Other GNU Tools, Prev: Programs, Up: Top 9 Other Derived Objects *********************** Automake can handle derived objects that are not C programs. Sometimes the support for building such objects must be explicitly supplied, but Automake can still automatically handle installation and distribution. * Menu: * Scripts:: Executable scripts * Headers:: Header files * Data:: Architecture-independent data files * Sources:: Derived sources  File: automake.info, Node: Scripts, Next: Headers, Up: Other Objects 9.1 Executable Scripts ====================== It is possible to define and install programs that are scripts. Such programs are listed using the ‘SCRIPTS’ primary name. When the script is distributed in its final, installable form, the ‘Makefile’ usually looks as follows: # Install my_script in $(bindir) and distribute it. dist_bin_SCRIPTS = my_script Scripts are not distributed by default; as we have just seen, those that should be distributed can be specified using a ‘dist_’ prefix as with other primaries. Scripts can be installed in ‘bindir’, ‘sbindir’, ‘libexecdir’, ‘pkglibexecdir’, or ‘pkgdatadir’. Scripts that need not be installed can be listed in ‘noinst_SCRIPTS’, and among them, those which are needed only by ‘make check’ should go in ‘check_SCRIPTS’. When a script needs to be built, the ‘Makefile.am’ should include the appropriate rules. For instance the ‘automake’ program itself is a Perl script that is generated from ‘automake.in’. Here is how this is handled: bin_SCRIPTS = automake CLEANFILES = $(bin_SCRIPTS) EXTRA_DIST = automake.in do_subst = sed -e 's,[@]datadir[@],$(datadir),g' \ -e 's,[@]PERL[@],$(PERL),g' \ -e 's,[@]PACKAGE[@],$(PACKAGE),g' \ -e 's,[@]VERSION[@],$(VERSION),g' \ ... automake: automake.in Makefile $(do_subst) < $(srcdir)/automake.in > automake chmod +x automake Such scripts for which a build rule has been supplied need to be deleted explicitly using ‘CLEANFILES’ (*note Clean::), and their sources have to be distributed, usually with ‘EXTRA_DIST’ (*note Basics of Distribution::). Another common way to build scripts is to process them from ‘configure’ with ‘AC_CONFIG_FILES’. In this situation Automake knows which files should be cleaned and distributed, and what the rebuild rules should look like. For instance if ‘configure.ac’ contains AC_CONFIG_FILES([src/my_script], [chmod +x src/my_script]) to build ‘src/my_script’ from ‘src/my_script.in’, then a ‘src/Makefile.am’ to install this script in ‘$(bindir)’ can be as simple as bin_SCRIPTS = my_script CLEANFILES = $(bin_SCRIPTS) There is no need for ‘EXTRA_DIST’ or any build rule: Automake infers them from ‘AC_CONFIG_FILES’ (*note Requirements::). ‘CLEANFILES’ is still useful, because by default Automake will clean targets of ‘AC_CONFIG_FILES’ in ‘distclean’, not ‘clean’. Although this looks simpler, building scripts this way has one drawback: directory variables such as ‘$(datadir)’ are not fully expanded and may refer to other directory variables.  File: automake.info, Node: Headers, Next: Data, Prev: Scripts, Up: Other Objects 9.2 Header files ================ Header files that must be installed are specified by the ‘HEADERS’ family of variables. Headers can be installed in ‘includedir’, ‘oldincludedir’, ‘pkgincludedir’ or any other directory you may have defined (*note Uniform::). For instance, include_HEADERS = foo.h bar/bar.h will install the two files as ‘$(includedir)/foo.h’ and ‘$(includedir)/bar.h’. The ‘nobase_’ prefix is also supported: nobase_include_HEADERS = foo.h bar/bar.h will install the two files as ‘$(includedir)/foo.h’ and ‘$(includedir)/bar/bar.h’ (*note Alternative::). Usually, only header files that accompany installed libraries need to be installed. Headers used by programs or convenience libraries are not installed. The ‘noinst_HEADERS’ variable can be used for such headers. However, when the header belongs to a single convenience library or program, we recommend listing it in the program’s or library’s ‘_SOURCES’ variable (*note Program Sources::) instead of in ‘noinst_HEADERS’. This is clearer for the ‘Makefile.am’ reader. ‘noinst_HEADERS’ would be the right variable to use in a directory containing only headers and no associated library or program. All header files must be listed somewhere; in a ‘_SOURCES’ variable or in a ‘_HEADERS’ variable. Missing ones will not appear in the distribution. For header files that are built and must not be distributed, use the ‘nodist_’ prefix as in ‘nodist_include_HEADERS’ or ‘nodist_prog_SOURCES’. If these generated headers are needed during the build, you must also ensure they exist before they are used (*note Sources::).  File: automake.info, Node: Data, Next: Sources, Prev: Headers, Up: Other Objects 9.3 Architecture-independent data files ======================================= Automake supports the installation of miscellaneous data files using the ‘DATA’ family of variables. Such data can be installed in the directories ‘datadir’, ‘sysconfdir’, ‘sharedstatedir’, ‘localstatedir’, or ‘pkgdatadir’. By default, data files are _not_ included in a distribution. Of course, you can use the ‘dist_’ prefix to change this on a per-variable basis. Here is how Automake declares its auxiliary data files: dist_pkgdata_DATA = clean-kr.am clean.am ...  File: automake.info, Node: Sources, Prev: Data, Up: Other Objects 9.4 Built Sources ================= Because Automake’s automatic dependency tracking works as a side-effect of compilation (*note Dependencies::) there is a bootstrap issue: a target should not be compiled before its dependencies are made, but these dependencies are unknown until the target is first compiled. Ordinarily this is not a problem, because dependencies are distributed sources: they preexist and do not need to be built. Suppose that ‘foo.c’ includes ‘foo.h’. When it first compiles ‘foo.o’, ‘make’ only knows that ‘foo.o’ depends on ‘foo.c’. As a side-effect of this compilation ‘depcomp’ records the ‘foo.h’ dependency so that following invocations of ‘make’ will honor it. In these conditions, it’s clear there is no problem: either ‘foo.o’ doesn’t exist and has to be built (regardless of the dependencies), or accurate dependencies exist and they can be used to decide whether ‘foo.o’ should be rebuilt. It’s a different story if ‘foo.h’ doesn’t exist by the first ‘make’ run. For instance, there might be a rule to build ‘foo.h’. This time ‘file.o’’s build will fail because the compiler can’t find ‘foo.h’. ‘make’ failed to trigger the rule to build ‘foo.h’ first by lack of dependency information. The ‘BUILT_SOURCES’ variable is a workaround for this problem. A source file listed in ‘BUILT_SOURCES’ is made when ‘make all’, ‘make check’, ‘make install’, ‘make install-exec’ (or ‘make dist’) is run, before other targets are processed. However, such a source file is not _compiled_ unless explicitly requested by mentioning it in some other ‘_SOURCES’ variable. So, to conclude our introductory example, we could use ‘BUILT_SOURCES = foo.h’ to ensure ‘foo.h’ gets built before any other target (including ‘foo.o’) during ‘make all’ or ‘make check’. ‘BUILT_SOURCES’ is a bit of a misnomer, as any file which must be created early in the build process can be listed in this variable. Moreover, all built sources do not necessarily have to be listed in ‘BUILT_SOURCES’. For instance, a generated ‘.c’ file doesn’t need to appear in ‘BUILT_SOURCES’ (unless it is included by another source), because it’s a known dependency of the associated object. To emphasize, ‘BUILT_SOURCES’ is honored only by ‘make all’, ‘make check’, ‘make install’, and ‘make install-exec’ (and ‘make dist’). This means you cannot build an arbitrary target (e.g., ‘make foo’) in a clean tree if it depends on a built source. However it will succeed if you have run ‘make all’ earlier, because accurate dependencies are already available. The next section illustrates and discusses the handling of built sources on a toy example. * Menu: * Built Sources Example:: Several ways to handle built sources.  File: automake.info, Node: Built Sources Example, Up: Sources 9.4.1 Built Sources Example --------------------------- Suppose that ‘foo.c’ includes ‘bindir.h’, which is installation-dependent and not distributed: it needs to be built. Here ‘bindir.h’ defines the preprocessor macro ‘bindir’ to the value of the ‘make’ variable ‘bindir’ (inherited from ‘configure’). We suggest several implementations below. It’s not meant to be an exhaustive listing of all ways to handle built sources, but it will give you a few ideas if you encounter this issue. First Try ......... This first implementation will illustrate the bootstrap issue mentioned in the previous section (*note Sources::). Here is a tentative ‘Makefile.am’. # This won't work. bin_PROGRAMS = foo foo_SOURCES = foo.c nodist_foo_SOURCES = bindir.h CLEANFILES = bindir.h bindir.h: Makefile echo '#define bindir "$(bindir)"' >$@ This setup doesn’t work, because Automake doesn’t know that ‘foo.c’ includes ‘bindir.h’. Remember, automatic dependency tracking works as a side-effect of compilation, so the dependencies of ‘foo.o’ will be known only after ‘foo.o’ has been compiled (*note Dependencies::). The symptom is as follows. % make source='foo.c' object='foo.o' libtool=no \ depfile='.deps/foo.Po' tmpdepfile='.deps/foo.TPo' \ depmode=gcc /bin/sh ./depcomp \ gcc -I. -I. -g -O2 -c `test -f 'foo.c' || echo './'`foo.c foo.c:2: bindir.h: No such file or directory make: *** [foo.o] Error 1 In this example ‘bindir.h’ is not distributed nor installed, and it is not even being built on-time. One may wonder if the ‘nodist_foo_SOURCES = bindir.h’ line has any use at all. This line simply states that ‘bindir.h’ is a source of ‘foo’, so for instance, it should be inspected while generating tags (*note Tags::). In other words, it does not help our present problem, and the build would fail identically without it. Using ‘BUILT_SOURCES’ ..................... A solution is to require ‘bindir.h’ to be built before anything else. This is what ‘BUILT_SOURCES’ is meant for (*note Sources::). bin_PROGRAMS = foo foo_SOURCES = foo.c nodist_foo_SOURCES = bindir.h BUILT_SOURCES = bindir.h CLEANFILES = bindir.h bindir.h: Makefile echo '#define bindir "$(bindir)"' >$@ See how ‘bindir.h’ gets built first: % make echo '#define bindir "/usr/local/bin"' >bindir.h make all-am make[1]: Entering directory `/home/adl/tmp' source='foo.c' object='foo.o' libtool=no \ depfile='.deps/foo.Po' tmpdepfile='.deps/foo.TPo' \ depmode=gcc /bin/sh ./depcomp \ gcc -I. -I. -g -O2 -c `test -f 'foo.c' || echo './'`foo.c gcc -g -O2 -o foo foo.o make[1]: Leaving directory `/home/adl/tmp' However, as said earlier, ‘BUILT_SOURCES’ applies only to the ‘all’, ‘check’, and ‘install’ targets. It still fails if you try to run ‘make foo’ explicitly: % make clean test -z "bindir.h" || rm -f bindir.h test -z "foo" || rm -f foo rm -f *.o % : > .deps/foo.Po # Suppress previously recorded dependencies % make foo source='foo.c' object='foo.o' libtool=no \ depfile='.deps/foo.Po' tmpdepfile='.deps/foo.TPo' \ depmode=gcc /bin/sh ./depcomp \ gcc -I. -I. -g -O2 -c `test -f 'foo.c' || echo './'`foo.c foo.c:2: bindir.h: No such file or directory make: *** [foo.o] Error 1 Recording Dependencies manually ............................... Usually people are happy enough with ‘BUILT_SOURCES’ because they never build targets such as ‘make foo’ before ‘make all’, as in the previous example. However if this matters to you, you can avoid ‘BUILT_SOURCES’ and record such dependencies explicitly in the ‘Makefile.am’. bin_PROGRAMS = foo foo_SOURCES = foo.c nodist_foo_SOURCES = bindir.h foo.$(OBJEXT): bindir.h CLEANFILES = bindir.h bindir.h: Makefile echo '#define bindir "$(bindir)"' >$@ You don’t have to list _all_ the dependencies of ‘foo.o’ explicitly, only those that might need to be built. If a dependency already exists, it will not hinder the first compilation and will be recorded by the normal dependency tracking code. (After this first compilation, the dependency tracking code will also have recorded the dependency between ‘foo.o’ and ‘bindir.h’, so our explicit dependency is only useful to the first build.) Adding explicit dependencies like this can be a bit dangerous if you are not careful enough. This is due to the way Automake tries not to overwrite your rules (it assumes you know better than it). ‘foo.$(OBJEXT): bindir.h’ supersedes any rule Automake may want to output to build ‘foo.$(OBJEXT)’. It happens to work in this case because Automake doesn’t have to output any ‘foo.$(OBJEXT):’ target: it relies on a suffix rule instead (i.e., ‘.c.$(OBJEXT):’). Always check the generated ‘Makefile.in’ if you do this. Build ‘bindir.h’ from ‘configure’ ................................. It’s possible to define this preprocessor macro from ‘configure’, either in ‘config.h’ (*note Defining Directories: (autoconf)Defining Directories.), or by processing a ‘bindir.h.in’ file using ‘AC_CONFIG_FILES’ (*note Configuration Actions: (autoconf)Configuration Actions.). At this point it should be clear that building ‘bindir.h’ from ‘configure’ works well for this example. ‘bindir.h’ will exist before you build any target, hence will not cause any dependency issue. The Makefile can be shrunk as follows. We do not even have to mention ‘bindir.h’. bin_PROGRAMS = foo foo_SOURCES = foo.c However, it’s not always possible to build sources from ‘configure’, especially when these sources are generated by a tool that needs to be built first. Build ‘bindir.c’, not ‘bindir.h’. ................................. Another attractive idea is to define ‘bindir’ as a variable or function exported from ‘bindir.o’, and build ‘bindir.c’ instead of ‘bindir.h’. noinst_PROGRAMS = foo foo_SOURCES = foo.c bindir.h nodist_foo_SOURCES = bindir.c CLEANFILES = bindir.c bindir.c: Makefile echo 'const char bindir[] = "$(bindir)";' >$@ ‘bindir.h’ contains just the variable’s declaration and doesn’t need to be built, so it won’t cause any trouble. ‘bindir.o’ is always dependent on ‘bindir.c’, so ‘bindir.c’ will get built first. Which is best? .............. There is no panacea, of course. Each solution has its merits and drawbacks. You cannot use ‘BUILT_SOURCES’ if the ability to run ‘make foo’ on a clean tree is important to you. You won’t add explicit dependencies if you are leery of overriding an Automake rule by mistake. Building files from ‘./configure’ is not always possible, neither is converting ‘.h’ files into ‘.c’ files.  File: automake.info, Node: Other GNU Tools, Next: Documentation, Prev: Other Objects, Up: Top 10 Other GNU Tools ****************** Since Automake is primarily intended to generate ‘Makefile.in’s for use in GNU programs, it tries hard to interoperate with other GNU tools. * Menu: * Emacs Lisp:: Emacs Lisp * gettext:: Gettext * Libtool:: Libtool * Java:: Java bytecode compilation (deprecated) * Python:: Python  File: automake.info, Node: Emacs Lisp, Next: gettext, Up: Other GNU Tools 10.1 Emacs Lisp =============== Automake provides some support for Emacs Lisp. The ‘LISP’ primary is used to hold a list of ‘.el’ files. Possible prefixes for this primary are ‘lisp_’ and ‘noinst_’. Note that if ‘lisp_LISP’ is defined, then ‘configure.ac’ must run ‘AM_PATH_LISPDIR’ (*note Macros::). Lisp sources are not distributed by default. You can prefix the ‘LISP’ primary with ‘dist_’, as in ‘dist_lisp_LISP’ or ‘dist_noinst_LISP’, to indicate that these files should be distributed. Automake will byte-compile all Emacs Lisp source files using the Emacs found by ‘AM_PATH_LISPDIR’, if any was found. When performing such byte-compilation, the flags specified in the (developer-reserved) ‘AM_ELCFLAGS’ and (user-reserved) ‘ELCFLAGS’ make variables will be passed to the Emacs invocation. Byte-compiled Emacs Lisp files are not portable among all versions of Emacs, so it makes sense to turn this off if you expect sites to have more than one version of Emacs installed. Furthermore, many packages do not actually benefit from byte-compilation. Still, we recommend that you byte-compile your Emacs Lisp sources. It is probably better for sites with strange setups to cope for themselves than to make the installation less nice for everybody else. There are two ways to avoid byte-compiling. Historically, we have recommended the following construct. lisp_LISP = file1.el file2.el ELCFILES = ‘ELCFILES’ is an internal Automake variable that normally lists all ‘.elc’ files that must be byte-compiled. Automake defines ‘ELCFILES’ automatically from ‘lisp_LISP’. Emptying this variable explicitly prevents byte-compilation. Since Automake 1.8, we now recommend using ‘lisp_DATA’ instead: lisp_DATA = file1.el file2.el Note that these two constructs are not equivalent. ‘_LISP’ will not install a file if Emacs is not installed, while ‘_DATA’ will always install its files.  File: automake.info, Node: gettext, Next: Libtool, Prev: Emacs Lisp, Up: Other GNU Tools 10.2 Gettext ============ If ‘AM_GNU_GETTEXT’ is seen in ‘configure.ac’, then Automake turns on support for GNU gettext, a message catalog system for internationalization (*note Introduction: (gettext)Top.). The ‘gettext’ support in Automake requires the addition of one or two subdirectories to the package: ‘po’ and possibly also ‘intl’. The latter is needed if ‘AM_GNU_GETTEXT’ is not invoked with the ‘external’ argument, or if ‘AM_GNU_GETTEXT_INTL_SUBDIR’ is used. Automake ensures that these directories exist and are mentioned in ‘SUBDIRS’.  File: automake.info, Node: Libtool, Next: Java, Prev: gettext, Up: Other GNU Tools 10.3 Libtool ============ Automake provides support for GNU Libtool (*note Introduction: (libtool)Top.) with the ‘LTLIBRARIES’ primary. *Note A Shared Library::.  File: automake.info, Node: Java, Next: Python, Prev: Libtool, Up: Other GNU Tools 10.4 Java bytecode compilation (deprecated) =========================================== Automake provides some minimal support for Java bytecode compilation with the ‘JAVA’ primary (in addition to the support for compiling Java to native machine code; *note Java Support with gcj::). Note however that _the interface and most features described here are deprecated_. Future Automake releases will strive to provide a better and cleaner interface, which however _won’t be backward-compatible_; the present interface will probably be removed altogether some time after the introduction of the new interface (if that ever materializes). In any case, the current ‘JAVA’ primary features are frozen and will no longer be developed, not even to take bug fixes. Any ‘.java’ files listed in a ‘_JAVA’ variable will be compiled with ‘JAVAC’ at build time. By default, ‘.java’ files are not included in the distribution; you should use the ‘dist_’ prefix to distribute them. Here is a typical setup for distributing ‘.java’ files and installing the ‘.class’ files resulting from their compilation. javadir = $(datadir)/java dist_java_JAVA = a.java b.java ... Currently Automake enforces the restriction that only one ‘_JAVA’ primary can be used in a given ‘Makefile.am’. The reason for this restriction is that, in general, it isn’t possible to know which ‘.class’ files were generated from which ‘.java’ files, so it would be impossible to know which files to install where. For instance, a ‘.java’ file can define multiple classes; the resulting ‘.class’ file names cannot be predicted without parsing the ‘.java’ file. There are a few variables that are used when compiling Java sources: ‘JAVAC’ The name of the Java compiler. This defaults to ‘javac’. ‘JAVACFLAGS’ The flags to pass to the compiler. This is considered to be a user variable (*note User Variables::). ‘AM_JAVACFLAGS’ More flags to pass to the Java compiler. This, and not ‘JAVACFLAGS’, should be used when it is necessary to put Java compiler flags into ‘Makefile.am’. ‘JAVAROOT’ The value of this variable is passed to the ‘-d’ option to ‘javac’. It defaults to ‘$(top_builddir)’. ‘CLASSPATH_ENV’ This variable is a shell expression that is used to set the ‘CLASSPATH’ environment variable on the ‘javac’ command line. (In the future we will probably handle class path setting differently.)  File: automake.info, Node: Python, Prev: Java, Up: Other GNU Tools 10.5 Python =========== Automake provides support for Python compilation with the ‘PYTHON’ primary. A typical setup is to call ‘AM_PATH_PYTHON’ in ‘configure.ac’ and use a line like this in ‘Makefile.am’: python_PYTHON = tree.py leave.py Python source files are included in the distribution by default; prepend ‘nodist_’ (as in ‘nodist_python_PYTHON’) to omit them. At install time, any files listed in a ‘_PYTHON’ variable will be byte-compiled with ‘py-compile’. ‘py-compile’ creates both standard (‘.pyc’) and optimized (‘.pyo’) byte-compiled versions of the source files. Because byte-compilation occurs at install time, files listed in ‘noinst_PYTHON’ will not be compiled. Automake ships with an Autoconf macro named ‘AM_PATH_PYTHON’ that determines some Python-related directory variables (see below). If you have called ‘AM_PATH_PYTHON’ from ‘configure.ac’, then you may use the variables ‘python_PYTHON’ and ‘pkgpython_PYTHON’ to list Python source files in your ‘Makefile.am’, depending on whether you want your files installed in ‘pythondir’ or ‘pkgpythondir’, respectively. -- Macro: AM_PATH_PYTHON ([VERSION], [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND]) Search for a Python interpreter on the system. This macro takes three optional arguments. The first argument, if present, is the minimum version of Python required for this package: ‘AM_PATH_PYTHON’ will skip any Python interpreter that is older than VERSION. If an interpreter is found and satisfies VERSION, then ACTION-IF-FOUND is run. Otherwise, ACTION-IF-NOT-FOUND is run. If ACTION-IF-NOT-FOUND is not specified, as in the following example, the default is to abort ‘configure’: AM_PATH_PYTHON([2.5]) This is fine when Python is an absolute requirement for the package. If Python ≥ 2.5 was only _optional_ for the package, ‘AM_PATH_PYTHON’ could be called as follows. AM_PATH_PYTHON([2.5],, [:]) If the ‘PYTHON’ variable is set when ‘AM_PATH_PYTHON’ is called, then that will be the only Python interpreter that is tried. ‘AM_PATH_PYTHON’ creates the following output variables based on the Python installation found during configuration: ‘PYTHON’ The name of the Python executable, or ‘:’ if no suitable interpreter could be found. Assuming ACTION-IF-NOT-FOUND is used (otherwise ‘./configure’ will abort if Python is absent), the value of ‘PYTHON’ can be used to set up a conditional in order to disable the relevant part of a build as follows. AM_PATH_PYTHON(,, [:]) AM_CONDITIONAL([HAVE_PYTHON], [test "$PYTHON" != :]) ‘PYTHON_VERSION’ The Python version number, in the form MAJOR.MINOR (e.g., ‘2.5’). This is set to be the value of ‘'%u.%u' % sys.version_info[:2]’. ‘PYTHON_PREFIX’ ‘PYTHON_EXEC_PREFIX’ With no special options given, these have values ‘${prefix}’ and ‘${exec_prefix}’, respectively (unexpanded; see below). The ‘configure’ options ‘--with-python_prefix’ and ‘--with-python_exec_prefix’ set them to an explicit value. The ‘configure’ option ‘--with-python-sys-prefix’ set them to the values of Python’s ‘sys.prefix’ and ‘sys.exec_prefix’ variables. These often differ from ‘${prefix}’ and ‘${exec_prefix}’, e.g., on platforms such as Mac OS x (where Python is usually installed as a Framework). ‘PYTHON_PLATFORM’ The canonical name used by Python to describe the operating system, as given by ‘sys.platform’. This value is sometimes needed when building Python extensions. ‘pythondir’ The directory name for the ‘site-packages’ subdirectory of the standard Python install tree. ‘pkgpythondir’ This is the directory under ‘pythondir’ that is named after the package. That is, it is ‘$(pythondir)/$(PACKAGE)’. It is provided as a convenience. ‘pyexecdir’ This is the directory where Python extension modules (shared libraries) should be installed. An extension module written in C could be declared as follows to Automake: pyexec_LTLIBRARIES = quaternion.la quaternion_la_SOURCES = quaternion.c support.c support.h quaternion_la_LDFLAGS = -avoid-version -module ‘pkgpyexecdir’ This is a convenience variable that is defined as ‘$(pyexecdir)/$(PACKAGE)’. All of these directory variables have values that can start with either ‘${prefix}’ or ‘${exec_prefix}’, unexpanded. This works fine in ‘Makefile’s, but it makes these variables hard to use in ‘configure’. This is mandated by the GNU coding standards, so that the user can run ‘make prefix=/foo install’. The Autoconf manual has a section with more details on this topic (*note Installation Directory Variables: (autoconf)Installation Directory Variables.). See also *note Hard-Coded Install Paths::.  File: automake.info, Node: Documentation, Next: Install, Prev: Other GNU Tools, Up: Top 11 Building documentation ************************* Currently Automake provides support for Texinfo and man pages. * Menu: * Texinfo:: Texinfo * Man Pages:: Man pages  File: automake.info, Node: Texinfo, Next: Man Pages, Up: Documentation 11.1 Texinfo ============ If the current directory contains Texinfo source, you must declare it with the ‘TEXINFOS’ primary. Generally Texinfo files are converted into info, and thus the ‘info_TEXINFOS’ variable is most commonly used here. Any Texinfo source file should have the ‘.texi’ extension. Automake also accepts ‘.txi’ or ‘.texinfo’ extensions, but their use is discouraged now, and will elicit runtime warnings. Automake generates rules to build ‘.info’, ‘.dvi’, ‘.ps’, ‘.pdf’ and ‘.html’ files from your Texinfo sources. Following the GNU Coding Standards, only the ‘.info’ files are built by ‘make all’ and installed by ‘make install’ (unless you use ‘no-installinfo’, see below). Furthermore, ‘.info’ files are automatically distributed so that Texinfo is not a prerequisite for installing your package. It is worth noting that, contrary to what happens with the other formats, the generated ‘.info’ files are by default placed in ‘srcdir’ rather than in the ‘builddir’. This can be changed with the ‘info-in-builddir’ option. Other documentation formats can be built on request by ‘make dvi’, ‘make ps’, ‘make pdf’ and ‘make html’, and they can be installed with ‘make install-dvi’, ‘make install-ps’, ‘make install-pdf’ and ‘make install-html’ explicitly. ‘make uninstall’ will remove everything: the Texinfo documentation installed by default as well as all the above optional formats. All of these targets can be extended using ‘-local’ rules (*note Extending::). If the ‘.texi’ file ‘@include’s ‘version.texi’, then that file will be automatically generated. The file ‘version.texi’ defines four Texinfo flags you can reference using ‘@value{EDITION}’, ‘@value{VERSION}’, ‘@value{UPDATED}’, and ‘@value{UPDATED-MONTH}’. ‘EDITION’ ‘VERSION’ Both of these flags hold the version number of your program. They are kept separate for clarity. ‘UPDATED’ This holds the date the primary ‘.texi’ file was last modified. ‘UPDATED-MONTH’ This holds the name of the month in which the primary ‘.texi’ file was last modified. The ‘version.texi’ support requires the ‘mdate-sh’ script; this script is supplied with Automake and automatically included when ‘automake’ is invoked with the ‘--add-missing’ option. If you have multiple Texinfo files, and you want to use the ‘version.texi’ feature, then you have to have a separate version file for each Texinfo file. Automake will treat any include in a Texinfo file that matches ‘vers*.texi’ just as an automatically generated version file. Often an Info file depends on more than one ‘.texi’ file. For instance, in GNU Hello, ‘hello.texi’ includes the file ‘fdl.texi’. You can tell Automake about these dependencies using the ‘TEXI_TEXINFOS’ variable. Here is how GNU Hello does it: info_TEXINFOS = hello.texi hello_TEXINFOS = fdl.texi By default, Automake requires the file ‘texinfo.tex’ to appear in the same directory as the ‘Makefile.am’ file that lists the ‘.texi’ files. If you used ‘AC_CONFIG_AUX_DIR’ in ‘configure.ac’ (*note Finding ‘configure’ Input: (autoconf)Input.), then ‘texinfo.tex’ is looked for there. In both cases, ‘automake’ then supplies ‘texinfo.tex’ if ‘--add-missing’ is given, and takes care of its distribution. However, if you set the ‘TEXINFO_TEX’ variable (see below), it overrides the location of the file and turns off its installation into the source as well as its distribution. The option ‘no-texinfo.tex’ can be used to eliminate the requirement for the file ‘texinfo.tex’. Use of the variable ‘TEXINFO_TEX’ is preferable, however, because that allows the ‘dvi’, ‘ps’, and ‘pdf’ targets to still work. Automake generates an ‘install-info’ rule; some people apparently use this. By default, info pages are installed by ‘make install’, so running ‘make install-info’ is pointless. This can be prevented via the ‘no-installinfo’ option. In this case, ‘.info’ files are not installed by default, and user must request this explicitly using ‘make install-info’. By default, ‘make install-info’ and ‘make uninstall-info’ will try to run the ‘install-info’ program (if available) to update (or create/remove) the ‘${infodir}/dir’ index. If this is undesired, it can be prevented by exporting the ‘AM_UPDATE_INFO_DIR’ variable to "‘no’". The following variables are used by the Texinfo build rules. ‘MAKEINFO’ The name of the program invoked to build ‘.info’ files. This variable is defined by Automake. If the ‘makeinfo’ program is found on the system then it will be used by default; otherwise ‘missing’ will be used instead. ‘MAKEINFOHTML’ The command invoked to build ‘.html’ files. Automake defines this to ‘$(MAKEINFO) --html’. ‘MAKEINFOFLAGS’ User flags passed to each invocation of ‘$(MAKEINFO)’ and ‘$(MAKEINFOHTML)’. This user variable (*note User Variables::) is not expected to be defined in any ‘Makefile’; it can be used by users to pass extra flags to suit their needs. ‘AM_MAKEINFOFLAGS’ ‘AM_MAKEINFOHTMLFLAGS’ Maintainer flags passed to each ‘makeinfo’ invocation. Unlike ‘MAKEINFOFLAGS’, these variables are meant to be defined by maintainers in ‘Makefile.am’. ‘$(AM_MAKEINFOFLAGS)’ is passed to ‘makeinfo’ when building ‘.info’ files; and ‘$(AM_MAKEINFOHTMLFLAGS)’ is used when building ‘.html’ files. For instance, the following setting can be used to obtain one single ‘.html’ file per manual, without node separators. AM_MAKEINFOHTMLFLAGS = --no-headers --no-split ‘AM_MAKEINFOHTMLFLAGS’ defaults to ‘$(AM_MAKEINFOFLAGS)’. This means that defining ‘AM_MAKEINFOFLAGS’ without defining ‘AM_MAKEINFOHTMLFLAGS’ will impact builds of both ‘.info’ and ‘.html’ files. ‘TEXI2DVI’ The name of the command that converts a ‘.texi’ file into a ‘.dvi’ file. This defaults to ‘texi2dvi’, a script that ships with the Texinfo package. ‘TEXI2PDF’ The name of the command that translates a ‘.texi’ file into a ‘.pdf’ file. This defaults to ‘$(TEXI2DVI) --pdf --batch’. ‘DVIPS’ The name of the command that builds a ‘.ps’ file out of a ‘.dvi’ file. This defaults to ‘dvips’. ‘TEXINFO_TEX’ If your package has Texinfo files in many directories, you can use the variable ‘TEXINFO_TEX’ to tell Automake where to find the canonical ‘texinfo.tex’ for your package. The value of this variable should be the relative path from the current ‘Makefile.am’ to ‘texinfo.tex’: TEXINFO_TEX = ../doc/texinfo.tex  File: automake.info, Node: Man Pages, Prev: Texinfo, Up: Documentation 11.2 Man Pages ============== A package can also include man pages (but see the GNU standards on this matter, *note (standards)Man Pages::.) Man pages are declared using the ‘MANS’ primary. Generally the ‘man_MANS’ variable is used. Man pages are automatically installed in the correct subdirectory of ‘mandir’, based on the file extension. File extensions such as ‘.1c’ are handled by looking for the valid part of the extension and using that to determine the correct subdirectory of ‘mandir’. Valid section names are the digits ‘0’ through ‘9’, and the letters ‘l’ and ‘n’. Sometimes developers prefer to name a man page something like ‘foo.man’ in the source, and then rename it to have the correct suffix, for example ‘foo.1’, when installing the file. Automake also supports this mode. For a valid section named SECTION, there is a corresponding directory named ‘manSECTIONdir’, and a corresponding ‘_MANS’ variable. Files listed in such a variable are installed in the indicated section. If the file already has a valid suffix, then it is installed as-is; otherwise the file suffix is changed to match the section. For instance, consider this example: man1_MANS = rename.man thesame.1 alsothesame.1c In this case, ‘rename.man’ will be renamed to ‘rename.1’ when installed, but the other files will keep their names. By default, man pages are installed by ‘make install’. However, since the GNU project does not require man pages, many maintainers do not expend effort to keep the man pages up to date. In these cases, the ‘no-installman’ option will prevent the man pages from being installed by default. The user can still explicitly install them via ‘make install-man’. For fast installation, with many files it is preferable to use ‘manSECTION_MANS’ over ‘man_MANS’ as well as files that do not need to be renamed. Man pages are not currently considered to be source, because it is not uncommon for man pages to be automatically generated. Therefore they are not automatically included in the distribution. However, this can be changed by use of the ‘dist_’ prefix. For instance here is how to distribute and install the two man pages of GNU ‘cpio’ (which includes both Texinfo documentation and man pages): dist_man_MANS = cpio.1 mt.1 The ‘nobase_’ prefix is meaningless for man pages and is disallowed. Executables and manpages may be renamed upon installation (*note Renaming::). For manpages this can be avoided by use of the ‘notrans_’ prefix. For instance, suppose an executable ‘foo’ allowing to access a library function ‘foo’ from the command line. The way to avoid renaming of the ‘foo.3’ manpage is: man_MANS = foo.1 notrans_man_MANS = foo.3 ‘notrans_’ must be specified first when used in conjunction with either ‘dist_’ or ‘nodist_’ (*note Fine-grained Distribution Control::). For instance: notrans_dist_man3_MANS = bar.3