stdioext: Add support for musl libc. * m4/fbufmode.m4 (gl_FUNC_FBUFMODE): Test whether __fbufsize exists. * lib/fbufmode.c (fbufmode): Add conditional code for musl. * m4/fseterr.m4: New file. * lib/fseterr.h (fseterr): Define as an alias of __fseterr if that function exists. * modules/fseterr (Files): Add m4/fseterr.m4. (configure.ac): Invoke gl_FUNC_FSETERR. Compile fseterr.c if __fseterr does not exist. (Makefile.am): Remove fseterr.c from lib_SOURCES. * lib/freadable.h: Update comment. * lib/fwritable.h: Update comment. * lib/freading.h: Update comment. * lib/fwriting.h: Update comment. * m4/freadahead.m4: New file. * lib/freadahead.h (freadahead): Define as an alias of __freadahead if that function exists. * modules/freadahead (Files): Add m4/freadahead.m4. (configure.ac): Invoke gl_FUNC_FREADAHEAD. Compile freadahead.c if __freadahead does not exist. (Makefile.am): Remove freadahead.c from lib_SOURCES. * m4/freadptr.m4: New file. * lib/freadptr.h (freadptr): Define as an alias of __freadptr if that function exists. * modules/freadptr (Files): Add m4/freadptr.m4. (configure.ac): Invoke gl_FUNC_FREADPTR. Compile freadptr.c if __freadptr does not exist. (Makefile.am): Remove freadptr.c from lib_SOURCES. * m4/freadseek.m4: New file. * lib/freadseek.c (freadptrinc): Use __freadptrinc if that function exists. * modules/freadseek (Files): Add m4/freadseek.m4. (configure.ac): Invoke gl_FUNC_FREADSEEK. * lib/fpurge.c (fpurge): Update comment. Reported by and with help from Rich Felker <dalias@aerifal.cx>.

/* Retrieve information about a FILE stream.
   Copyright (C) 2007, 2009-2012 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include <stdbool.h>
#include <stdio.h>

/* Return true if the stream STREAM supports writing, false if it supports
   only reading.
   STREAM must not be wide-character oriented.
   The result doesn't change until the stream is closed or re-opened.  */

#if HAVE___FWRITABLE /* glibc >= 2.2, Solaris >= 7, musl libc */

# include <stdio_ext.h>
# define fwritable(stream) (__fwritable (stream) != 0)

#else

# ifdef __cplusplus
extern "C" {
# endif

extern bool fwritable (FILE *stream);

# ifdef __cplusplus
}
# endif

#endif