1 files changed, 91 insertions, 0 deletions
diff --git a/gl/m4/dirfd.m4 b/gl/m4/dirfd.m4
new file mode 100644
index 0000000..7968b12
--- /dev/null
+++ b/gl/m4/dirfd.m4
@@ -0,0 +1,91 @@
+# serial 28   -*- Autoconf -*-
+
+dnl Find out how to get the file descriptor associated with an open DIR*.
+
+# Copyright (C) 2001-2006, 2008-2023 Free Software Foundation, Inc.
+# This file is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+dnl From Jim Meyering
+
+AC_DEFUN([gl_FUNC_DIRFD],
+[
+  AC_REQUIRE([gl_DIRENT_H_DEFAULTS])
+  AC_REQUIRE([AC_CANONICAL_HOST])
+
+  dnl Persuade glibc <dirent.h> to declare dirfd().
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+
+  AC_CHECK_FUNCS([dirfd])
+  AC_CHECK_DECLS([dirfd], , ,
+    [[#include <sys/types.h>
+      #include <dirent.h>]])
+  if test $ac_cv_have_decl_dirfd = no; then
+    HAVE_DECL_DIRFD=0
+  fi
+
+  AC_CACHE_CHECK([whether dirfd is a macro],
+    [gl_cv_func_dirfd_macro],
+    [AC_EGREP_CPP([dirent_header_defines_dirfd], [
+#include <sys/types.h>
+#include <dirent.h>
+#ifdef dirfd
+ dirent_header_defines_dirfd
+#endif],
+       [gl_cv_func_dirfd_macro=yes],
+       [gl_cv_func_dirfd_macro=no])])
+
+  if test $ac_cv_func_dirfd = no && test $gl_cv_func_dirfd_macro = no; then
+    HAVE_DIRFD=0
+  else
+    HAVE_DIRFD=1
+    dnl Replace dirfd() on native Windows, to support fdopendir().
+    AC_REQUIRE([gl_DIRENT_DIR])
+    if test $DIR_HAS_FD_MEMBER = 0; then
+      REPLACE_DIRFD=1
+    fi
+    dnl OS/2 kLIBC dirfd() does not work.
+    case "$host_os" in
+      os2*) REPLACE_DIRFD=1 ;;
+    esac
+  fi
+])
+
+dnl Prerequisites of lib/dirfd.c.
+AC_DEFUN([gl_PREREQ_DIRFD],
+[
+  AC_CACHE_CHECK([how to get the file descriptor associated with an open DIR*],
+                 [gl_cv_sys_dir_fd_member_name],
+    [
+      dirfd_save_CFLAGS=$CFLAGS
+      for ac_expr in d_fd dd_fd; do
+
+        CFLAGS="$CFLAGS -DDIR_FD_MEMBER_NAME=$ac_expr"
+        AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+           #include <sys/types.h>
+           #include <dirent.h>]],
+          [[DIR *dir_p = opendir("."); (void) dir_p->DIR_FD_MEMBER_NAME;]])],
+          [dir_fd_found=yes]
+        )
+        CFLAGS=$dirfd_save_CFLAGS
+        test "$dir_fd_found" = yes && break
+      done
+      test "$dir_fd_found" = yes || ac_expr=no_such_member
+
+      gl_cv_sys_dir_fd_member_name=$ac_expr
+    ]
+  )
+  if test $gl_cv_sys_dir_fd_member_name != no_such_member; then
+    AC_DEFINE_UNQUOTED([DIR_FD_MEMBER_NAME],
+      [$gl_cv_sys_dir_fd_member_name],
+      [the name of the file descriptor member of DIR])
+  fi
+  AH_VERBATIM([DIR_TO_FD],
+              [#ifdef DIR_FD_MEMBER_NAME
+# define DIR_TO_FD(Dir_p) ((Dir_p)->DIR_FD_MEMBER_NAME)
+#else
+# define DIR_TO_FD(Dir_p) -1
+#endif
+])
+])