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# fcntl.m4 serial 11
dnl Copyright (C) 2009-2023 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.
# For now, this module ensures that fcntl()
# - supports F_DUPFD correctly
# - supports or emulates F_DUPFD_CLOEXEC
# - supports F_GETFD
# Still to be ported to mingw:
# - F_SETFD
# - F_GETFL, F_SETFL
# - F_GETOWN, F_SETOWN
# - F_GETLK, F_SETLK, F_SETLKW
AC_DEFUN([gl_FUNC_FCNTL],
[
dnl Persuade glibc to expose F_DUPFD_CLOEXEC.
AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
AC_REQUIRE([AC_CANONICAL_HOST])
AC_CHECK_FUNCS_ONCE([fcntl])
if test $ac_cv_func_fcntl = no; then
gl_REPLACE_FCNTL
else
dnl cygwin 1.5.x F_DUPFD has wrong errno, and allows negative target
dnl haiku alpha 2 F_DUPFD has wrong errno
AC_CACHE_CHECK([whether fcntl handles F_DUPFD correctly],
[gl_cv_func_fcntl_f_dupfd_works],
[AC_RUN_IFELSE(
[AC_LANG_PROGRAM(
[[#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <sys/resource.h>
#include <unistd.h>
]GL_MDA_DEFINES[
#ifndef RLIM_SAVED_CUR
# define RLIM_SAVED_CUR RLIM_INFINITY
#endif
#ifndef RLIM_SAVED_MAX
# define RLIM_SAVED_MAX RLIM_INFINITY
#endif
]],
[[int result = 0;
int bad_fd = INT_MAX;
struct rlimit rlim;
if (getrlimit (RLIMIT_NOFILE, &rlim) == 0
&& 0 <= rlim.rlim_cur && rlim.rlim_cur <= INT_MAX
&& rlim.rlim_cur != RLIM_INFINITY
&& rlim.rlim_cur != RLIM_SAVED_MAX
&& rlim.rlim_cur != RLIM_SAVED_CUR)
bad_fd = rlim.rlim_cur;
if (fcntl (0, F_DUPFD, -1) != -1) result |= 1;
if (errno != EINVAL) result |= 2;
if (fcntl (0, F_DUPFD, bad_fd) != -1) result |= 4;
if (errno != EINVAL) result |= 8;
/* On OS/2 kLIBC, F_DUPFD does not work on a directory fd */
{
int fd;
fd = open (".", O_RDONLY);
if (fd == -1)
result |= 16;
else if (fcntl (fd, F_DUPFD, STDERR_FILENO + 1) == -1)
result |= 32;
close (fd);
}
return result;]])],
[gl_cv_func_fcntl_f_dupfd_works=yes],
[gl_cv_func_fcntl_f_dupfd_works=no],
[case $host_os in
aix* | cygwin* | haiku*)
gl_cv_func_fcntl_f_dupfd_works="guessing no" ;;
*) gl_cv_func_fcntl_f_dupfd_works="guessing yes" ;;
esac])])
case $gl_cv_func_fcntl_f_dupfd_works in
*yes) ;;
*) gl_REPLACE_FCNTL
AC_DEFINE([FCNTL_DUPFD_BUGGY], [1], [Define this to 1 if F_DUPFD
behavior does not match POSIX]) ;;
esac
dnl Many systems lack F_DUPFD_CLOEXEC.
dnl NetBSD 9.0 declares F_DUPFD_CLOEXEC but it works only like F_DUPFD.
AC_CACHE_CHECK([whether fcntl understands F_DUPFD_CLOEXEC],
[gl_cv_func_fcntl_f_dupfd_cloexec],
[AC_RUN_IFELSE(
[AC_LANG_SOURCE(
[[#include <fcntl.h>
#include <unistd.h>
int main (int argc, char *argv[])
{
if (argc == 1)
/* parent process */
{
if (fcntl (1, F_DUPFD_CLOEXEC, 10) < 0)
return 1;
return execl ("./conftest", "./conftest", "child", NULL);
}
else
/* child process */
return (fcntl (10, F_GETFL) < 0 ? 0 : 42);
}
]])
],
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
#ifdef __linux__
/* The Linux kernel only added F_DUPFD_CLOEXEC in 2.6.24, so we always replace
it to support the semantics on older kernels that failed with EINVAL. */
choke me
#endif
]])],
[gl_cv_func_fcntl_f_dupfd_cloexec=yes],
[gl_cv_func_fcntl_f_dupfd_cloexec="needs runtime check"])
],
[gl_cv_func_fcntl_f_dupfd_cloexec=no],
[case "$host_os" in
# Guess no on NetBSD.
netbsd*) gl_cv_func_fcntl_f_dupfd_cloexec="guessing no" ;;
*) gl_cv_func_fcntl_f_dupfd_cloexec="$gl_cross_guess_normal" ;;
esac
])
])
case "$gl_cv_func_fcntl_f_dupfd_cloexec" in
*yes) ;;
*) gl_REPLACE_FCNTL
dnl No witness macro needed for this bug.
;;
esac
fi
dnl Replace fcntl() for supporting the gnulib-defined fchdir() function,
dnl to keep fchdir's bookkeeping up-to-date.
m4_ifdef([gl_FUNC_FCHDIR], [
gl_TEST_FCHDIR
if test $HAVE_FCHDIR = 0; then
gl_REPLACE_FCNTL
fi
])
])
AC_DEFUN([gl_REPLACE_FCNTL],
[
AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
AC_CHECK_FUNCS_ONCE([fcntl])
if test $ac_cv_func_fcntl = no; then
HAVE_FCNTL=0
else
REPLACE_FCNTL=1
fi
])
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