1# fchdir.m4 serial 26
2dnl Copyright (C) 2006-2021 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
7AC_DEFUN([gl_FUNC_FCHDIR],
8[
9  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
10  AC_REQUIRE([gl_DIRENT_H_DEFAULTS])
11  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
12
13  AC_CHECK_DECLS_ONCE([fchdir])
14  if test $ac_cv_have_decl_fchdir = no; then
15    HAVE_DECL_FCHDIR=0
16  fi
17
18  AC_REQUIRE([gl_TEST_FCHDIR])
19  if test $HAVE_FCHDIR = 0; then
20    AC_LIBOBJ([fchdir])
21    gl_PREREQ_FCHDIR
22    AC_DEFINE([REPLACE_FCHDIR], [1],
23      [Define to 1 if gnulib's fchdir() replacement is used.])
24    dnl We must also replace anything that can manipulate a directory fd,
25    dnl to keep our bookkeeping up-to-date.  We don't have to replace
26    dnl fstatat, since no platform has fstatat but lacks fchdir.
27    AC_CACHE_CHECK([whether open can visit directories],
28      [gl_cv_func_open_directory_works],
29      [AC_RUN_IFELSE(
30         [AC_LANG_PROGRAM(
31            [[#include <fcntl.h>
32            ]GL_MDA_DEFINES],
33            [[return open(".", O_RDONLY) < 0;]])],
34         [gl_cv_func_open_directory_works=yes],
35         [gl_cv_func_open_directory_works=no],
36         [case "$host_os" in
37                             # Guess yes on Linux systems.
38            linux-* | linux) gl_cv_func_open_directory_works="guessing yes" ;;
39                             # Guess yes on glibc systems.
40            *-gnu* | gnu*)   gl_cv_func_open_directory_works="guessing yes" ;;
41                             # Guess no on native Windows.
42            mingw*)          gl_cv_func_open_directory_works="guessing no" ;;
43                             # If we don't know, obey --enable-cross-guesses.
44            *)               gl_cv_func_open_directory_works="$gl_cross_guess_normal" ;;
45          esac
46         ])])
47    case "$gl_cv_func_open_directory_works" in
48      *yes) ;;
49      *)
50        AC_DEFINE([REPLACE_OPEN_DIRECTORY], [1], [Define to 1 if open() should
51work around the inability to open a directory.])
52        ;;
53    esac
54  fi
55])
56
57# Determine whether to use the overrides in lib/fchdir.c.
58AC_DEFUN([gl_TEST_FCHDIR],
59[
60  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
61  AC_CHECK_FUNCS_ONCE([fchdir])
62  if test $ac_cv_func_fchdir = no; then
63    HAVE_FCHDIR=0
64  fi
65])
66
67# Prerequisites of lib/fchdir.c.
68AC_DEFUN([gl_PREREQ_FCHDIR], [:])
69