warnings: port to clang

Problem reported by Daniel P. Berrange via Eric Blake in
<http://lists.gnu.org/archive/html/bug-gnulib/2013-05/msg00055.html>.
* m4/warnings.m4 (gl_UNKNOWN_WARNINGS_ARE_ERRORS): New macro.
(gl_WARN_ADD): Use it.

diff --git a/ChangeLog b/ChangeLog
index 08f2fe0..b7aceaa 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2013-05-15  Paul Eggert  <eggert@cs.ucla.edu>
+
+       warnings: port to clang
+       Problem reported by Daniel P. Berrange via Eric Blake in
+       <http://lists.gnu.org/archive/html/bug-gnulib/2013-05/msg00055.html>.
+       * m4/warnings.m4 (gl_UNKNOWN_WARNINGS_ARE_ERRORS): New macro.
+       (gl_WARN_ADD): Use it.
+
 2013-05-11  Jim Meyering  <meyering@fb.com>
 
        quotearg: do not read beyond end of buffer

diff --git a/m4/warnings.m4 b/m4/warnings.m4
index 4b2ac38..1848732 100644 (file)
--- a/m4/warnings.m4
+++ b/m4/warnings.m4
@@ -1,4 +1,4 @@
-# warnings.m4 serial 7
+# warnings.m4 serial 8
 dnl Copyright (C) 2008-2013 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -27,7 +27,7 @@ AC_DEFUN([gl_COMPILER_OPTION_IF],
 AS_VAR_PUSHDEF([gl_Flags], [_AC_LANG_PREFIX[]FLAGS])dnl
 AC_CACHE_CHECK([whether _AC_LANG compiler handles $1], m4_defn([gl_Warn]), [
   gl_save_compiler_FLAGS="$gl_Flags"
-  gl_AS_VAR_APPEND(m4_defn([gl_Flags]), [" $1"])
+  gl_AS_VAR_APPEND(m4_defn([gl_Flags]), [" $gl_unknown_warnings_are_errors $1"])
   AC_COMPILE_IFELSE([m4_default([$4], [AC_LANG_PROGRAM([])])],
                     [AS_VAR_SET(gl_Warn, [yes])],
                     [AS_VAR_SET(gl_Warn, [no])])
@@ -38,6 +38,14 @@ AS_VAR_POPDEF([gl_Flags])dnl
 AS_VAR_POPDEF([gl_Warn])dnl
 ])
 
+# gl_UNKNOWN_WARNINGS_ARE_ERRORS
+# ------------------------------
+# Clang doesn't complain about unknown warning options unless one also
+# specifies -Wunknown-warning-option -Werror.  Detect this.
+AC_DEFUN([gl_UNKNOWN_WARNINGS_ARE_ERRORS],
+[gl_COMPILER_OPTION_IF([-Werror -Wunknown-warning-option],
+   [gl_unknown_warnings_are_errors='-Wunknown-warning-option -Werror'],
+   [gl_unknown_warnings_are_errors=])])
 
 # gl_WARN_ADD(OPTION, [VARIABLE = WARN_CFLAGS],
 #             [PROGRAM = AC_LANG_PROGRAM()])
@@ -47,7 +55,8 @@ AS_VAR_POPDEF([gl_Warn])dnl
 #
 # If VARIABLE is a variable name, AC_SUBST it.
 AC_DEFUN([gl_WARN_ADD],
-[gl_COMPILER_OPTION_IF([$1],
+[AC_REQUIRE([gl_UNKNOWN_WARNINGS_ARE_ERRORS])
+gl_COMPILER_OPTION_IF([$1],
   [gl_AS_VAR_APPEND(m4_if([$2], [], [[WARN_CFLAGS]], [[$2]]), [" $1"])],
   [],
   [$3])