Turn off -Wmaybe-uninitialized when building with -Os

gcc-4.7 and higher add a lot of false positive warnings about
potential uses of uninitialized warnings, but only when optimizing
for size (-Os). This is the default when building allyesconfig,
which turns on CONFIG_CC_OPTIMIZE_FOR_SIZE.

In order to avoid getting a lot of patches that initialize such
variables and accidentally hide real errors along the way, let's
just turn off this warning on the respective gcc versions
when building with size optimizations. The -Wmaybe-uninitialized
option was introduced in the same gcc version (4.7) that is now
causing the false positives, so there is no effect on older compilers.

A side effect is that when building with CONFIG_CC_OPTIMIZE_FOR_SIZE,
we might now see /fewer/ warnings about possibly uninitialized
warnings than with -O2, but that is still much better than seeing
warnings known to be bogus.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

diff --git a/Makefile b/Makefile
index 58a165b02af1e27acb6d2635f3c9ab0d58c5cb00..8004421a93d134ac85b5512ae190f44c370ceb9a 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -570,7 +570,7 @@ endif # $(dot-config)
 all: vmlinux
 
 ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
-KBUILD_CFLAGS  += -Os
+KBUILD_CFLAGS  += -Os $(call cc-disable-warning,maybe-uninitialized,)
 else
 KBUILD_CFLAGS  += -O2
 endif