Don't allow installation with stale devel version number.

[gnulib.git] / m4 / include_next.m4

diff --git a/m4/include_next.m4 b/m4/include_next.m4
index 4dc84c9..a842e2a 100644 (file)
--- a/m4/include_next.m4
+++ b/m4/include_next.m4
@@ -1,5 +1,5 @@
-# include_next.m4 serial 3
-dnl Copyright (C) 2006, 2007 Free Software Foundation, Inc.
+# include_next.m4 serial 6
+dnl Copyright (C) 2006-2008 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -11,9 +11,31 @@ AC_DEFUN([gl_INCLUDE_NEXT],
   AC_LANG_PREPROC_REQUIRE()
   AC_CACHE_CHECK([whether the preprocessor supports include_next],
     [gl_cv_have_include_next],
-    [AC_PREPROC_IFELSE([#include_next <stddef.h>],
+    [rm -rf conftestd1 conftestd2
+     mkdir conftestd1 conftestd2
+     cat <<EOF > conftestd1/conftest.h
+#define DEFINED_IN_CONFTESTD1
+#include_next <conftest.h>
+#ifdef DEFINED_IN_CONFTESTD2
+int foo;
+#else
+#error "include_next doesn't work"
+#endif
+EOF
+     cat <<EOF > conftestd2/conftest.h
+#ifndef DEFINED_IN_CONFTESTD1
+#error "include_next test doesn't work"
+#endif
+#define DEFINED_IN_CONFTESTD2
+EOF
+     save_CPPFLAGS="$CPPFLAGS"
+     CPPFLAGS="$CPPFLAGS -Iconftestd1 -Iconftestd2"
+     AC_COMPILE_IFELSE([#include <conftest.h>],
        [gl_cv_have_include_next=yes],
-       [gl_cv_have_include_next=no])])
+       [gl_cv_have_include_next=no])
+     CPPFLAGS="$save_CPPFLAGS"
+     rm -rf conftestd1 conftestd2
+    ])
   if test $gl_cv_have_include_next = yes; then
 
     dnl FIXME: Remove HAVE_INCLUDE_NEXT and update everything that uses it
@@ -41,12 +63,15 @@ AC_DEFUN([gl_INCLUDE_NEXT],
 # The three "///" are to pacify Sun C 5.8, which otherwise would say
 # "warning: #include of /usr/include/... may be non-portable".
 # Use `""', not `<>', so that the /// cannot be confused with a C99 comment.
+# Note: This macro assumes that the header file is not empty after
+# preprocessing, i.e. it does not only define preprocessor macros but also
+# provides some type/enum definitions or function/variable declarations.
 AC_DEFUN([gl_CHECK_NEXT_HEADERS],
 [
   AC_REQUIRE([gl_INCLUDE_NEXT])
   AC_CHECK_HEADERS_ONCE([$1])
 
-  AC_FOREACH([gl_HEADER_NAME], [$1],
+  m4_foreach_w([gl_HEADER_NAME], [$1],
     [AS_VAR_PUSHDEF([gl_next_header],
                    [gl_cv_next_]m4_quote(m4_defn([gl_HEADER_NAME])))
      if test $gl_cv_have_include_next = yes; then