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# ungetc.m4 serial 12
dnl Copyright (C) 2009-2024 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
AC_DEFUN_ONCE([gl_FUNC_UNGETC_WORKS],
[
AC_REQUIRE([AC_PROG_CC])
AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
AC_CACHE_CHECK([whether ungetc works on arbitrary bytes],
[gl_cv_func_ungetc_works],
[AC_RUN_IFELSE([AC_LANG_PROGRAM([[
#include <stdio.h>
]], [[FILE *f;
if (!(f = fopen ("conftest.tmp", "w+")))
return 1;
if (fputs ("abc", f) < 0)
{ fclose (f); return 2; }
rewind (f);
if (fgetc (f) != 'a')
{ fclose (f); return 3; }
if (fgetc (f) != 'b')
{ fclose (f); return 4; }
if (ungetc ('d', f) != 'd')
{ fclose (f); return 5; }
if (ftell (f) != 1)
{ fclose (f); return 6; }
if (fgetc (f) != 'd')
{ fclose (f); return 7; }
if (ftell (f) != 2)
{ fclose (f); return 8; }
if (fseek (f, 0, SEEK_CUR) != 0)
{ fclose (f); return 9; }
if (ftell (f) != 2)
{ fclose (f); return 10; }
if (fgetc (f) != 'c')
{ fclose (f); return 11; }
fclose (f);
remove ("conftest.tmp");
]])],
[gl_cv_func_ungetc_works=yes], [gl_cv_func_ungetc_works=no],
[case "$host_os" in
# Guess yes on glibc systems.
*-gnu* | gnu*) gl_cv_func_ungetc_works="guessing yes" ;;
# Guess yes on musl systems.
*-musl* | midipix*) gl_cv_func_ungetc_works="guessing yes" ;;
# Guess yes on bionic systems.
*-android*) gl_cv_func_ungetc_works="guessing yes" ;;
# Guess yes on native Windows.
mingw* | windows*) gl_cv_func_ungetc_works="guessing yes" ;;
# If we don't know, obey --enable-cross-guesses.
*) gl_cv_func_ungetc_works="$gl_cross_guess_normal" ;;
esac
])
])
gl_ftello_broken_after_ungetc=no
case "$gl_cv_func_ungetc_works" in
*yes) ;;
*)
dnl On macOS >= 10.15, where the above program fails with exit code 6,
dnl we fix it through an ftello override.
case "$host_os" in
darwin*) gl_ftello_broken_after_ungetc=yes ;;
*)
AC_DEFINE([FUNC_UNGETC_BROKEN], [1],
[Define to 1 if ungetc is broken when used on arbitrary bytes.])
;;
esac
;;
esac
])
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