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# dup2.m4
# serial 28
dnl Copyright (C) 2002, 2005, 2007, 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([gl_FUNC_DUP2],
[
AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
AC_REQUIRE([AC_CANONICAL_HOST])
AC_CACHE_CHECK([whether dup2 works], [gl_cv_func_dup2_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;
#ifdef FD_CLOEXEC
if (fcntl (1, F_SETFD, FD_CLOEXEC) == -1)
result |= 1;
#endif
if (dup2 (1, 1) != 1)
result |= 2;
#ifdef FD_CLOEXEC
if (fcntl (1, F_GETFD) != FD_CLOEXEC)
result |= 4;
#endif
close (0);
if (dup2 (0, 0) != -1)
result |= 8;
/* Many gnulib modules require POSIX conformance of EBADF. */
if (dup2 (2, bad_fd) == -1 && errno != EBADF)
result |= 16;
/* Flush out some cygwin core dumps. */
if (dup2 (2, -1) != -1 || errno != EBADF)
result |= 32;
dup2 (2, 255);
dup2 (2, 256);
/* On OS/2 kLIBC, dup2() does not work on a directory fd. */
{
int fd = open (".", O_RDONLY);
if (fd == -1)
result |= 64;
else if (dup2 (fd, fd + 1) == -1)
result |= 128;
close (fd);
}
return result;]])
],
[gl_cv_func_dup2_works=yes], [gl_cv_func_dup2_works=no],
[case "$host_os" in
mingw* | windows*) # on this platform, dup2 always returns 0 for success
gl_cv_func_dup2_works="guessing no" ;;
cygwin*) # on cygwin 1.5.x, dup2(1,1) returns 0
gl_cv_func_dup2_works="guessing no" ;;
aix* | freebsd*)
# on AIX 7.1 and FreeBSD 6.1, dup2 (1,toobig) gives EMFILE,
# not EBADF.
gl_cv_func_dup2_works="guessing no" ;;
haiku*) # on Haiku alpha 2, dup2(1, 1) resets FD_CLOEXEC.
gl_cv_func_dup2_works="guessing no" ;;
*-android*) # implemented using dup3(), which fails if oldfd == newfd
gl_cv_func_dup2_works="guessing no" ;;
os2*) # on OS/2 kLIBC, dup2() does not work on a directory fd.
gl_cv_func_dup2_works="guessing no" ;;
*) gl_cv_func_dup2_works="guessing yes" ;;
esac])
])
case "$gl_cv_func_dup2_works" in
*yes) ;;
*)
REPLACE_DUP2=1
AC_CHECK_FUNCS([setdtablesize])
;;
esac
dnl Replace dup2() 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
REPLACE_DUP2=1
fi
])
])
# Prerequisites of lib/dup2.c.
AC_DEFUN([gl_PREREQ_DUP2], [])
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