From: David Herrmann <dh.herrmann@gmail.com>
Date: Tue, 24 Feb 2015 16:49:48 +0000 (+0100)
Subject: build: make sure to test for -Wflag instead of -Wno-flag
X-Git-Tag: v219.0~588
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=commitdiff_plain;h=43bbf1acc8202de895e5449828a7b863c69fcc2f;ds=inline

build: make sure to test for -Wflag instead of -Wno-flag

gcc does not support testing for negated warnings. See here for details:
    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63499

This patch changes CC_CHECK_FLAG_APPEND to always test for the non-negated
warnings.
---

diff --git a/m4/attributes.m4 b/m4/attributes.m4
index ac3c6624c..97f094b07 100644
--- a/m4/attributes.m4
+++ b/m4/attributes.m4
@@ -34,14 +34,15 @@ dnl this special exception to the GPL to apply to your modified version as
 dnl well.
 
 dnl Check if FLAG in ENV-VAR is supported by compiler and append it
-dnl to WHERE-TO-APPEND variable
+dnl to WHERE-TO-APPEND variable. Note that we invert -Wno-* checks to
+dnl -W* as gcc cannot test for negated warnings.
 dnl CC_CHECK_FLAG_APPEND([WHERE-TO-APPEND], [ENV-VAR], [FLAG])
 
 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])='-Werror $3'"
+           eval "AS_TR_SH([$2])='-Werror `echo "$3" | sed 's/^-Wno-/-W/'`'"
            AC_LINK_IFELSE([AC_LANG_SOURCE([int main(void) { return 0; } ])],
                           [eval "AS_TR_SH([cc_cv_$2_$3])='yes'"],
                           [eval "AS_TR_SH([cc_cv_$2_$3])='no'"])