2 dnl Copyright (C) 2002, 2005, 2007, 2009-2020 Free Software Foundation, Inc.
3 dnl This file is free software; the Free Software Foundation
4 dnl gives unlimited permission to copy and/or distribute it,
5 dnl with or without modifications, as long as this notice is preserved.
7 AC_DEFUN([gl_FUNC_DUP2],
9 AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
10 AC_REQUIRE([AC_CANONICAL_HOST])
11 AC_CACHE_CHECK([whether dup2 works], [gl_cv_func_dup2_works],
17 #include <sys/resource.h>
19 #ifndef RLIM_SAVED_CUR
20 # define RLIM_SAVED_CUR RLIM_INFINITY
22 #ifndef RLIM_SAVED_MAX
23 # define RLIM_SAVED_MAX RLIM_INFINITY
29 if (getrlimit (RLIMIT_NOFILE, &rlim) == 0
30 && 0 <= rlim.rlim_cur && rlim.rlim_cur <= INT_MAX
31 && rlim.rlim_cur != RLIM_INFINITY
32 && rlim.rlim_cur != RLIM_SAVED_MAX
33 && rlim.rlim_cur != RLIM_SAVED_CUR)
34 bad_fd = rlim.rlim_cur;
36 if (fcntl (1, F_SETFD, FD_CLOEXEC) == -1)
42 if (fcntl (1, F_GETFD) != FD_CLOEXEC)
46 if (dup2 (0, 0) != -1)
48 /* Many gnulib modules require POSIX conformance of EBADF. */
49 if (dup2 (2, bad_fd) == -1 && errno != EBADF)
51 /* Flush out some cygwin core dumps. */
52 if (dup2 (2, -1) != -1 || errno != EBADF)
56 /* On OS/2 kLIBC, dup2() does not work on a directory fd. */
58 int fd = open (".", O_RDONLY);
61 else if (dup2 (fd, fd + 1) == -1)
67 [gl_cv_func_dup2_works=yes], [gl_cv_func_dup2_works=no],
69 mingw*) # on this platform, dup2 always returns 0 for success
70 gl_cv_func_dup2_works="guessing no" ;;
71 cygwin*) # on cygwin 1.5.x, dup2(1,1) returns 0
72 gl_cv_func_dup2_works="guessing no" ;;
74 # on AIX 7.1 and FreeBSD 6.1, dup2 (1,toobig) gives EMFILE,
76 gl_cv_func_dup2_works="guessing no" ;;
77 haiku*) # on Haiku alpha 2, dup2(1, 1) resets FD_CLOEXEC.
78 gl_cv_func_dup2_works="guessing no" ;;
79 *-android*) # implemented using dup3(), which fails if oldfd == newfd
80 gl_cv_func_dup2_works="guessing no" ;;
81 os2*) # on OS/2 kLIBC, dup2() does not work on a directory fd.
82 gl_cv_func_dup2_works="guessing no" ;;
83 *) gl_cv_func_dup2_works="guessing yes" ;;
86 case "$gl_cv_func_dup2_works" in
90 AC_CHECK_FUNCS([setdtablesize])
93 dnl Replace dup2() for supporting the gnulib-defined fchdir() function,
94 dnl to keep fchdir's bookkeeping up-to-date.
95 m4_ifdef([gl_FUNC_FCHDIR], [
97 if test $HAVE_FCHDIR = 0; then
103 # Prerequisites of lib/dup2.c.
104 AC_DEFUN([gl_PREREQ_DUP2], [])