From: Lucas De Marchi <lucas.demarchi@profusion.mobi>
Date: Fri, 14 Sep 2012 14:18:41 +0000 (-0300)
Subject: build-sys: Append -Werror when testing flags
X-Git-Tag: v11~39
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7812d88c95e10e690c3d1c057ab2fa7ad1edaafa;p=thirdparty%2Fkmod.git

build-sys: Append -Werror when testing flags

Clang doesn't treat unknown warnings flags as an error, but rather as a
warning. The result is that the detection for whic CFLAGS are supported
by this compiler will not work, since the compilation will succeed.

With this patch we now successfully detect clang doesn't support
-Wlogical-op, as opposed to previous behavior:

	checking if clang supports flag -Wlogical-op in envvar CFLAGS... no

We use this macro only for LDFLAGS and CFLAGS, so it's safe to stash
-Werror there.
---

diff --git a/m4/attributes.m4 b/m4/attributes.m4
index c80ae62e..e8221970 100644
--- a/m4/attributes.m4
+++ b/m4/attributes.m4
@@ -40,7 +40,7 @@ AC_DEFUN([CC_CHECK_FLAG_APPEND], [
   AC_CACHE_CHECK([if $CC supports flag $3 in envvar $2],
                  AS_TR_SH([cc_cv_$2_$3]),
 		 [eval "AS_TR_SH([cc_save_$2])='${$2}'"
-		  eval "AS_TR_SH([$2])='$3'"
+		  eval "AS_TR_SH([$2])='-Werror $3'"
 		  AC_COMPILE_IFELSE([AC_LANG_SOURCE([int a = 0; int main(void) { return a; } ])],
                                     [eval "AS_TR_SH([cc_cv_$2_$3])='yes'"],
                                     [eval "AS_TR_SH([cc_cv_$2_$3])='no'"])