1# fcntl.m4 serial 5
2dnl Copyright (C) 2009-2012 Free Software Foundation, Inc.
3dnl This file is free software; the Free Software Foundation
4dnl gives unlimited permission to copy and/or distribute it,
5dnl with or without modifications, as long as this notice is preserved.
6
7# For now, this module ensures that fcntl()
8# - supports F_DUPFD correctly
9# - supports or emulates F_DUPFD_CLOEXEC
10# - supports F_GETFD
11# Still to be ported to mingw:
12# - F_SETFD
13# - F_GETFL, F_SETFL
14# - F_GETOWN, F_SETOWN
15# - F_GETLK, F_SETLK, F_SETLKW
16AC_DEFUN([gl_FUNC_FCNTL],
17[
18  dnl Persuade glibc to expose F_DUPFD_CLOEXEC.
19  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
20  AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
21  AC_REQUIRE([AC_CANONICAL_HOST])
22  AC_CHECK_FUNCS_ONCE([fcntl])
23  if test $ac_cv_func_fcntl = no; then
24    gl_REPLACE_FCNTL
25  else
26    dnl cygwin 1.5.x F_DUPFD has wrong errno, and allows negative target
27    dnl haiku alpha 2 F_DUPFD has wrong errno
28    AC_CACHE_CHECK([whether fcntl handles F_DUPFD correctly],
29      [gl_cv_func_fcntl_f_dupfd_works],
30      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
31#include <fcntl.h>
32#include <errno.h>
33]], [[int result = 0;
34      if (fcntl (0, F_DUPFD, -1) != -1) result |= 1;
35      if (errno != EINVAL) result |= 2;
36      return result;
37         ]])],
38         [gl_cv_func_fcntl_f_dupfd_works=yes],
39         [gl_cv_func_fcntl_f_dupfd_works=no],
40         [# Guess that it works on glibc systems
41          case $host_os in #((
42            *-gnu*) gl_cv_func_fcntl_f_dupfd_works="guessing yes";;
43            *)      gl_cv_func_fcntl_f_dupfd_works="guessing no";;
44          esac])])
45    case $gl_cv_func_fcntl_f_dupfd_works in
46      *yes) ;;
47      *) gl_REPLACE_FCNTL
48        AC_DEFINE([FCNTL_DUPFD_BUGGY], [1], [Define this to 1 if F_DUPFD
49          behavior does not match POSIX]) ;;
50    esac
51
52    dnl Many systems lack F_DUPFD_CLOEXEC
53    AC_CACHE_CHECK([whether fcntl understands F_DUPFD_CLOEXEC],
54      [gl_cv_func_fcntl_f_dupfd_cloexec],
55      [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
56#include <fcntl.h>
57#ifndef F_DUPFD_CLOEXEC
58choke me
59#endif
60         ]])],
61         [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
62#ifdef __linux__
63/* The Linux kernel only added F_DUPFD_CLOEXEC in 2.6.24, so we always replace
64   it to support the semantics on older kernels that failed with EINVAL.  */
65choke me
66#endif
67           ]])],
68           [gl_cv_func_fcntl_f_dupfd_cloexec=yes],
69           [gl_cv_func_fcntl_f_dupfd_cloexec="needs runtime check"])],
70         [gl_cv_func_fcntl_f_dupfd_cloexec=no])])
71    if test "$gl_cv_func_fcntl_f_dupfd_cloexec" != yes; then
72      gl_REPLACE_FCNTL
73      dnl No witness macro needed for this bug.
74    fi
75  fi
76  dnl Replace fcntl() for supporting the gnulib-defined fchdir() function,
77  dnl to keep fchdir's bookkeeping up-to-date.
78  m4_ifdef([gl_FUNC_FCHDIR], [
79    gl_TEST_FCHDIR
80    if test $HAVE_FCHDIR = 0; then
81      gl_REPLACE_FCNTL
82    fi
83  ])
84])
85
86AC_DEFUN([gl_REPLACE_FCNTL],
87[
88  AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
89  AC_CHECK_FUNCS_ONCE([fcntl])
90  if test $ac_cv_func_fcntl = no; then
91    HAVE_FCNTL=0
92  else
93    REPLACE_FCNTL=1
94  fi
95])
96