| 1 | # fcntl.m4 serial 11
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| 2 | dnl Copyright (C) 2009-2021 Free Software Foundation, Inc.
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| 3 | dnl This file is free software; the Free Software Foundation
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| 4 | dnl gives unlimited permission to copy and/or distribute it,
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| 5 | dnl with or without modifications, as long as this notice is preserved.
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| 6 |
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| 7 | # For now, this module ensures that fcntl()
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| 8 | # - supports F_DUPFD correctly
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| 9 | # - supports or emulates F_DUPFD_CLOEXEC
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| 10 | # - supports F_GETFD
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| 11 | # Still to be ported to mingw:
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| 12 | # - F_SETFD
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| 13 | # - F_GETFL, F_SETFL
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| 14 | # - F_GETOWN, F_SETOWN
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| 15 | # - F_GETLK, F_SETLK, F_SETLKW
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| 16 | AC_DEFUN([gl_FUNC_FCNTL],
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| 17 | [
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| 18 | dnl Persuade glibc to expose F_DUPFD_CLOEXEC.
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| 19 | AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
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| 20 | AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
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| 21 | AC_REQUIRE([AC_CANONICAL_HOST])
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| 22 | AC_CHECK_FUNCS_ONCE([fcntl])
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| 23 | if test $ac_cv_func_fcntl = no; then
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| 24 | gl_REPLACE_FCNTL
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| 25 | else
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| 26 | dnl cygwin 1.5.x F_DUPFD has wrong errno, and allows negative target
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| 27 | dnl haiku alpha 2 F_DUPFD has wrong errno
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| 28 | AC_CACHE_CHECK([whether fcntl handles F_DUPFD correctly],
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| 29 | [gl_cv_func_fcntl_f_dupfd_works],
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| 30 | [AC_RUN_IFELSE(
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| 31 | [AC_LANG_PROGRAM(
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| 32 | [[#include <errno.h>
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| 33 | #include <fcntl.h>
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| 34 | #include <limits.h>
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| 35 | #include <sys/resource.h>
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| 36 | #include <unistd.h>
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| 37 | ]GL_MDA_DEFINES[
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| 38 | #ifndef RLIM_SAVED_CUR
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| 39 | # define RLIM_SAVED_CUR RLIM_INFINITY
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| 40 | #endif
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| 41 | #ifndef RLIM_SAVED_MAX
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| 42 | # define RLIM_SAVED_MAX RLIM_INFINITY
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| 43 | #endif
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| 44 | ]],
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| 45 | [[int result = 0;
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| 46 | int bad_fd = INT_MAX;
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| 47 | struct rlimit rlim;
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| 48 | if (getrlimit (RLIMIT_NOFILE, &rlim) == 0
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| 49 | && 0 <= rlim.rlim_cur && rlim.rlim_cur <= INT_MAX
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| 50 | && rlim.rlim_cur != RLIM_INFINITY
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| 51 | && rlim.rlim_cur != RLIM_SAVED_MAX
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| 52 | && rlim.rlim_cur != RLIM_SAVED_CUR)
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| 53 | bad_fd = rlim.rlim_cur;
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| 54 | if (fcntl (0, F_DUPFD, -1) != -1) result |= 1;
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| 55 | if (errno != EINVAL) result |= 2;
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| 56 | if (fcntl (0, F_DUPFD, bad_fd) != -1) result |= 4;
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| 57 | if (errno != EINVAL) result |= 8;
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| 58 | /* On OS/2 kLIBC, F_DUPFD does not work on a directory fd */
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| 59 | {
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| 60 | int fd;
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| 61 | fd = open (".", O_RDONLY);
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| 62 | if (fd == -1)
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| 63 | result |= 16;
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| 64 | else if (fcntl (fd, F_DUPFD, STDERR_FILENO + 1) == -1)
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| 65 | result |= 32;
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| 66 |
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| 67 | close (fd);
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| 68 | }
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| 69 | return result;]])],
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| 70 | [gl_cv_func_fcntl_f_dupfd_works=yes],
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| 71 | [gl_cv_func_fcntl_f_dupfd_works=no],
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| 72 | [case $host_os in
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| 73 | aix* | cygwin* | haiku*)
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| 74 | gl_cv_func_fcntl_f_dupfd_works="guessing no" ;;
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| 75 | *) gl_cv_func_fcntl_f_dupfd_works="guessing yes" ;;
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| 76 | esac])])
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| 77 | case $gl_cv_func_fcntl_f_dupfd_works in
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| 78 | *yes) ;;
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| 79 | *) gl_REPLACE_FCNTL
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| 80 | AC_DEFINE([FCNTL_DUPFD_BUGGY], [1], [Define this to 1 if F_DUPFD
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| 81 | behavior does not match POSIX]) ;;
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| 82 | esac
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| 83 |
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| 84 | dnl Many systems lack F_DUPFD_CLOEXEC.
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| 85 | dnl NetBSD 9.0 declares F_DUPFD_CLOEXEC but it works only like F_DUPFD.
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| 86 | AC_CACHE_CHECK([whether fcntl understands F_DUPFD_CLOEXEC],
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| 87 | [gl_cv_func_fcntl_f_dupfd_cloexec],
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| 88 | [AC_RUN_IFELSE(
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| 89 | [AC_LANG_SOURCE(
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| 90 | [[#include <fcntl.h>
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| 91 | #include <unistd.h>
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| 92 | int main (int argc, char *argv[])
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| 93 | {
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| 94 | if (argc == 1)
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| 95 | /* parent process */
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| 96 | {
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| 97 | if (fcntl (1, F_DUPFD_CLOEXEC, 10) < 0)
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| 98 | return 1;
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| 99 | return execl ("./conftest", "./conftest", "child", NULL);
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| 100 | }
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| 101 | else
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| 102 | /* child process */
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| 103 | return (fcntl (10, F_GETFL) < 0 ? 0 : 42);
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| 104 | }
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| 105 | ]])
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| 106 | ],
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| 107 | [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
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| 108 | #ifdef __linux__
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| 109 | /* The Linux kernel only added F_DUPFD_CLOEXEC in 2.6.24, so we always replace
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| 110 | it to support the semantics on older kernels that failed with EINVAL. */
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| 111 | choke me
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| 112 | #endif
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| 113 | ]])],
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| 114 | [gl_cv_func_fcntl_f_dupfd_cloexec=yes],
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| 115 | [gl_cv_func_fcntl_f_dupfd_cloexec="needs runtime check"])
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| 116 | ],
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| 117 | [gl_cv_func_fcntl_f_dupfd_cloexec=no],
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| 118 | [case "$host_os" in
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| 119 | # Guess no on NetBSD.
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| 120 | netbsd*) gl_cv_func_fcntl_f_dupfd_cloexec="guessing no" ;;
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| 121 | *) gl_cv_func_fcntl_f_dupfd_cloexec="$gl_cross_guess_normal" ;;
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| 122 | esac
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| 123 | ])
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| 124 | ])
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| 125 | case "$gl_cv_func_fcntl_f_dupfd_cloexec" in
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| 126 | *yes) ;;
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| 127 | *) gl_REPLACE_FCNTL
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| 128 | dnl No witness macro needed for this bug.
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| 129 | ;;
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| 130 | esac
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| 131 | fi
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| 132 | dnl Replace fcntl() for supporting the gnulib-defined fchdir() function,
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| 133 | dnl to keep fchdir's bookkeeping up-to-date.
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| 134 | m4_ifdef([gl_FUNC_FCHDIR], [
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| 135 | gl_TEST_FCHDIR
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| 136 | if test $HAVE_FCHDIR = 0; then
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| 137 | gl_REPLACE_FCNTL
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| 138 | fi
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| 139 | ])
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| 140 | ])
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| 141 |
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| 142 | AC_DEFUN([gl_REPLACE_FCNTL],
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| 143 | [
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| 144 | AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
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| 145 | AC_CHECK_FUNCS_ONCE([fcntl])
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| 146 | if test $ac_cv_func_fcntl = no; then
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| 147 | HAVE_FCNTL=0
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| 148 | else
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| 149 | REPLACE_FCNTL=1
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| 150 | fi
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| 151 | ])
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