commit c7b1e060d17023065c776757da406d728310cc38
Author: Bruno Haible <bruno@clisp.org>
Date:   Sun Jun 20 17:18:26 2021 +0200

    unistd: Avoid compilation error in C++ mode on Solaris, HP-UX, mingw.
    
    Reported by Eli Zaretskii <eliz@gnu.org> in
    <https://lists.gnu.org/archive/html/bug-gnulib/2021-03/msg00135.html>.
    
    * lib/unistd.in.h (swab): Consider different declarations on Solaris,
    HP-UX, and old mingw.

diff --git a/gnulib/import/unistd.in.h b/gnulib/import/unistd.in.h
index d4d4ba7743..73c882f97b 100644
--- a/gnulib/import/unistd.in.h
+++ b/gnulib/import/unistd.in.h
@@ -2034,9 +2034,17 @@ _GL_WARN_ON_USE (sleep, "sleep is unportable - "
 #   undef swab
 #   define swab _swab
 #  endif
-_GL_CXXALIAS_MDA (swab, void, (char *from, char *to, int n));
-# else
+/* Need to cast, because in old mingw the arguments are
+                             (const char *from, char *to, size_t n).  */
+_GL_CXXALIAS_MDA_CAST (swab, void, (char *from, char *to, int n));
+# else
+#  if defined __hpux /* HP-UX */
+_GL_CXXALIAS_SYS (swab, void, (const char *from, char *to, int n));
+#  elif defined __sun && !defined _XPG4 /* Solaris */
+_GL_CXXALIAS_SYS (swab, void, (const char *from, char *to, ssize_t n));
+#  else
 _GL_CXXALIAS_SYS (swab, void, (const void *from, void *to, ssize_t n));
+#  endif
 # endif
 _GL_CXXALIASWARN (swab);
 #endif