gnulib/doc/posix-functions/isalnum.texi

@node isalnum
@section @code{isalnum}
@findex isalnum

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

Gnulib module: ctype

Portability problems fixed by Gnulib:
@itemize
@item
This function cannot be called from plain inline or extern inline functions
on some platforms:
OS X 10.8.
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@end itemize

Note: This function's behaviour depends on the locale, but does not support
the multibyte characters that occur in strings in locales with
@code{MB_CUR_MAX > 1} (this includes all the common UTF-8 locales).
There are four alternative APIs:

@table @code
@item c_isalnum
This function operates in a locale independent way and returns true only for
ASCII characters.  It is provided by the Gnulib module @samp{c-ctype}.

@item iswalnum
This function operates in a locale dependent way, on wide characters.  In
order to use it, you first have to convert from multibyte to wide characters,
using the @code{mbrtowc} function.  It is provided by the Gnulib module
@samp{wctype}.

@item mb_isalnum
This function operates in a locale dependent way, on multibyte characters.
It is provided by the Gnulib module @samp{mbchar}.

@item uc_is_alnum
This function operates in a locale independent way, on Unicode characters.
It is provided by the Gnulib module @samp{unictype/ctype-alnum}.
@end table