@node mbrtowc
@section @code{mbrtowc}
@findex mbrtowc

POSIX specification:@* @url{https://pubs.opengroup.org/onlinepubs/9699919799/functions/mbrtowc.html}

Gnulib module: mbrtowc

Portability problems fixed by Gnulib:
@itemize
@item
This function is missing on some platforms:
Minix 3.1.8, HP-UX 11.00, IRIX 6.5, mingw.
@item
In the C or POSIX locales, this function can return @code{(size_t) -1}
and set @code{errno} to @code{EILSEQ}:
@c https://sourceware.org/bugzilla/show_bug.cgi?id=19932
@c https://sourceware.org/bugzilla/show_bug.cgi?id=29511
glibc 2.35.
@item
This function returns 0 instead of @code{(size_t) -2} when the input
is empty:
@c https://sourceware.org/bugzilla/show_bug.cgi?id=16950
glibc 2.19,
MSVC 14, Android 11.
@item
This function returns @code{(size_t) -1} instead of @code{(size_t) -2}
when the input is empty:
AIX 7.2.
@item
This function does not put the state into non-initial state when parsing an
incomplete multibyte character on some platforms:
AIX 7.2.
@item
This function stores a wide character when parsing an incomplete multibyte
character on some platforms:
MSVC 14.
@item
This function returns the total number of bytes that make up the multibyte
character, not the number of bytes that were needed to complete the multibyte
character, on some platforms:
HP-UX 11.11, Solaris 11 2010-11, mingw, MSVC 14.
@item
This function may not return 0 when parsing the NUL character on some platforms:
Solaris 9.
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@item
In UTF-8 locales, this function may return wide characters up to 0x7FFFFFFF
(that is, beyond 0x0010FFFF) on some platforms:
@c https://sourceware.org/bugzilla/show_bug.cgi?id=2373
@c https://sourceware.org/bugzilla/show_bug.cgi?id=26034
glibc 2.34.
@item
On Windows and 32-bit AIX platforms, @code{wchar_t} is a 16-bit type and
therefore cannot accommodate all Unicode characters.
However, the ISO C11 function @code{mbrtoc32}, provided by Gnulib module
@code{mbrtoc32}, operates on 32-bit wide characters and therefore does not have
this limitation.
@end itemize