| Message ID | 7534695.eTHcH0enMV@wuerfel (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Mar 14, 2013 at 11:01:35PM +0100, Arnd Bergmann wrote: > 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. What about truely uninitialized uses of variables? Will this hide their warning too?
diff --git a/Makefile b/Makefile index 10fb6c7..caea2d1 100644 --- 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
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> Cc: stable@vger.kernel.org -- I'd like to merge this for 3.9 and also for the stable kernels, if people agree this is a good idea.