From 27b778ca743eca6f318de4aa21b1700dbaf3bb3511d58095735319e99781a59b Mon Sep 17 00:00:00 2001
From: Michael Matz <matz@suse.com>
Date: Fri, 9 Mar 2018 17:08:53 +0000
Subject: [PATCH] fix check for -Wno flag

OBS-URL: https://build.opensuse.org/package/show/devel:gcc/gdb?expand=0&rev=178
---
 gdb.spec | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/gdb.spec b/gdb.spec
index 511ebfa..a39c291 100644
--- a/gdb.spec
+++ b/gdb.spec
@@ -586,7 +586,13 @@ export CXX
 export CFLAGS="$RPM_OPT_FLAGS"
 
 # FIXME: gcc-7 compatibility.
-if echo "" | $CC  -x c -c - -o /dev/null -Wno-implicit-fallthrough >/dev/null 2>&1; then
+# checking for acceptance of -Wno-foo is a bit wieldy: GCC doesn't 
+# warn about unknown -Wno- flags, _except_ if there are other
+# diagnostics as well, so let's force an uninitialized use warning
+# and grep for the diagnostic about the -Wno flag:
+if echo "int foo(void) { int a; return a;} " | \
+   $CC  -x c -c - -o /dev/null -W -Wno-implicit-fallthrough 2>&1 | \
+   grep Wno-implici >/dev/null; then
   CFLAGS="$CFLAGS -Wno-implicit-fallthrough"
 fi
 %if %{have_libipt}