1# serial 26   -*- Autoconf -*-
2
3dnl Find out how to get the file descriptor associated with an open DIR*.
4
5# Copyright (C) 2001-2006, 2008-2020 Free Software Foundation, Inc.
6# This file is free software; the Free Software Foundation
7# gives unlimited permission to copy and/or distribute it,
8# with or without modifications, as long as this notice is preserved.
9
10dnl From Jim Meyering
11
12AC_DEFUN([gl_FUNC_DIRFD],
13[
14  AC_REQUIRE([gl_DIRENT_H_DEFAULTS])
15  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
16
17  dnl Persuade glibc <dirent.h> to declare dirfd().
18  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
19
20  AC_CHECK_FUNCS([dirfd])
21  AC_CHECK_DECLS([dirfd], , ,
22    [[#include <sys/types.h>
23      #include <dirent.h>]])
24  if test $ac_cv_have_decl_dirfd = no; then
25    HAVE_DECL_DIRFD=0
26  fi
27
28  AC_CACHE_CHECK([whether dirfd is a macro],
29    [gl_cv_func_dirfd_macro],
30    [AC_EGREP_CPP([dirent_header_defines_dirfd], [
31#include <sys/types.h>
32#include <dirent.h>
33#ifdef dirfd
34 dirent_header_defines_dirfd
35#endif],
36       [gl_cv_func_dirfd_macro=yes],
37       [gl_cv_func_dirfd_macro=no])])
38
39  # Use the replacement if we have no function or macro with that name,
40  # or if OS/2 kLIBC whose dirfd() does not work.
41  # Replace only if the system declares dirfd already.
42  case $ac_cv_func_dirfd,$gl_cv_func_dirfd_macro,$host_os,$ac_cv_have_decl_dirfd in
43    no,no,*,yes | *,*,os2*,yes)
44      REPLACE_DIRFD=1
45      AC_DEFINE([REPLACE_DIRFD], [1],
46        [Define to 1 if gnulib's dirfd() replacement is used.]);;
47  esac
48])
49
50dnl Prerequisites of lib/dirfd.c.
51AC_DEFUN([gl_PREREQ_DIRFD],
52[
53  AC_CACHE_CHECK([how to get the file descriptor associated with an open DIR*],
54                 [gl_cv_sys_dir_fd_member_name],
55    [
56      dirfd_save_CFLAGS=$CFLAGS
57      for ac_expr in d_fd dd_fd; do
58
59        CFLAGS="$CFLAGS -DDIR_FD_MEMBER_NAME=$ac_expr"
60        AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
61           #include <sys/types.h>
62           #include <dirent.h>]],
63          [[DIR *dir_p = opendir("."); (void) dir_p->DIR_FD_MEMBER_NAME;]])],
64          [dir_fd_found=yes]
65        )
66        CFLAGS=$dirfd_save_CFLAGS
67        test "$dir_fd_found" = yes && break
68      done
69      test "$dir_fd_found" = yes || ac_expr=no_such_member
70
71      gl_cv_sys_dir_fd_member_name=$ac_expr
72    ]
73  )
74  if test $gl_cv_sys_dir_fd_member_name != no_such_member; then
75    AC_DEFINE_UNQUOTED([DIR_FD_MEMBER_NAME],
76      [$gl_cv_sys_dir_fd_member_name],
77      [the name of the file descriptor member of DIR])
78  fi
79  AH_VERBATIM([DIR_TO_FD],
80              [#ifdef DIR_FD_MEMBER_NAME
81# define DIR_TO_FD(Dir_p) ((Dir_p)->DIR_FD_MEMBER_NAME)
82#else
83# define DIR_TO_FD(Dir_p) -1
84#endif
85])
86])
87