glob: Don't compile replacements on recent glibc systems.

* lib/glob.in.h: Use the usual idiom for the double-inclusion guard. If
REPLACE_GLOB is 0, include the system's <glob.h> and use
_GL_CXXALIAS_SYS.
* m4/glob.m4 (gl_GLOB): Set REPLACE_GLOB instead of GLOB_H. Accept
_GNU_GLOB_INTERFACE_VERSION 2 as well. Delete the file conf$$-globtest
inside the AC_RUN_IFELSE block. Remove GL_GENERATE_GLOB_H conditional.
* modules/glob (Dependencies): Test REPLACE_GLOB instead of GLOB_H.
Remove snippet/warn-on-use.
(configure.ac): Test REPLACE_GLOB instead of GLOB_H.
(Makefile.am): Create glob.h always. Update list of substitutions in
glob.h. Don't depend on $(WARN_ON_USE_H).

1 files changed, 34 insertions, 30 deletions

diff --git a/m4/glob.m4 b/m4/glob.m4
index 9dedb41306..37cb91745c 100644
--- a/m4/glob.m4
+++ b/m4/glob.m4
@@ -1,4 +1,4 @@
-# glob.m4 serial 16
+# glob.m4 serial 18
 dnl Copyright (C) 2005-2007, 2009-2018 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -9,54 +9,58 @@ dnl with or without modifications, as long as this notice is preserved.
 # always include <glob.h> for the glob prototypes.
 
 AC_DEFUN([gl_GLOB],
-[ GLOB_H=
-  AC_CHECK_HEADERS([glob.h], [], [GLOB_H=glob.h])
+[
+  dnl <glob.h> is always overridden, because of the C++ GNULIB_NAMESPACE.
+  gl_CHECK_NEXT_HEADERS([glob.h])
+  if test $ac_cv_header_glob_h = yes; then
+    REPLACE_GLOB=0
+  else
+    REPLACE_GLOB=1
+  fi
 
-  if test -z "$GLOB_H"; then
-    AC_CACHE_CHECK([for GNU glob interface version 1],
-      [gl_cv_gnu_glob_interface_version_1],
+  if test $REPLACE_GLOB = 0; then
+    AC_CACHE_CHECK([for GNU glob interface version 1 or 2],
+      [gl_cv_gnu_glob_interface_version_1_2],
 [     AC_COMPILE_IFELSE([AC_LANG_SOURCE(
 [[#include <gnu-versions.h>
-char a[_GNU_GLOB_INTERFACE_VERSION == 1 ? 1 : -1];]])],
-        [gl_cv_gnu_glob_interface_version_1=yes],
-        [gl_cv_gnu_glob_interface_version_1=no])])
+char a[_GNU_GLOB_INTERFACE_VERSION == 1 || _GNU_GLOB_INTERFACE_VERSION == 2 ? 1 : -1];]])],
+        [gl_cv_gnu_glob_interface_version_1_2=yes],
+        [gl_cv_gnu_glob_interface_version_1_2=no])])
 
-    if test "$gl_cv_gnu_glob_interface_version_1" = "no"; then
-      GLOB_H=glob.h
+    if test "$gl_cv_gnu_glob_interface_version_1_2" = "no"; then
+      REPLACE_GLOB=1
     fi
   fi
 
-  if test -z "$GLOB_H"; then
+  if test $REPLACE_GLOB = 0; then
     AC_CACHE_CHECK([whether glob lists broken symlinks],
                    [gl_cv_glob_lists_symlinks],
-[     if ln -s conf-doesntexist conf$$-globtest 2>/dev/null; then
-        gl_cv_glob_lists_symlinks=maybe
-      else
-        # If we can't make a symlink, then we cannot test this issue.  Be
-        # pessimistic about this.
-        gl_cv_glob_lists_symlinks=no
-      fi
-
-      if test $gl_cv_glob_lists_symlinks = maybe; then
-        AC_RUN_IFELSE([
+      [if ln -s conf-doesntexist conf$$-globtest 2>/dev/null; then
+         gl_cv_glob_lists_symlinks=maybe
+       else
+         # If we can't make a symlink, then we cannot test this issue.  Be
+         # pessimistic about this.
+         gl_cv_glob_lists_symlinks=no
+       fi
+       if test $gl_cv_glob_lists_symlinks = maybe; then
+         AC_RUN_IFELSE([
 AC_LANG_PROGRAM(
 [[#include <stddef.h>
 #include <glob.h>]],
 [[glob_t found;
 if (glob ("conf*-globtest", 0, NULL, &found) == GLOB_NOMATCH) return 1;]])],
-          [gl_cv_glob_lists_symlinks=yes],
-          [gl_cv_glob_lists_symlinks=no], [gl_cv_glob_lists_symlinks=no])
-      fi])
+           [gl_cv_glob_lists_symlinks=yes],
+           [gl_cv_glob_lists_symlinks=no], [gl_cv_glob_lists_symlinks=no])
+       fi
+       rm -f conf$$-globtest
+      ])
 
     if test $gl_cv_glob_lists_symlinks = no; then
-      GLOB_H=glob.h
+      REPLACE_GLOB=1
     fi
   fi
 
-  rm -f conf$$-globtest
-
-  AC_SUBST([GLOB_H])
-  AM_CONDITIONAL([GL_GENERATE_GLOB_H], [test -n "$GLOB_H"])
+  AC_SUBST([REPLACE_GLOB])
 ])
 
 # Prerequisites of lib/glob.*.