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      1 # serial 26   -*- Autoconf -*-
      2 
      3 dnl Find out how to get the file descriptor associated with an open DIR*.
      4 
      5 # Copyright (C) 2001-2006, 2008-2022 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 
     10 dnl From Jim Meyering
     11 
     12 AC_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 
     50 dnl Prerequisites of lib/dirfd.c.
     51 AC_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