[PATCH 1/5] Kbuild: change CC_OPTIMIZE_FOR_SIZE definition

From: Arnd Bergmann
Date: Fri Feb 12 2016 - 11:07:33 EST


CC_OPTIMIZE_FOR_SIZE disables the often useful -Wmaybe-unused warning,
because that causes a ridiculous amount of false positives when combined
with -Os.

This means a lot of warnings don't show up in testing by the developers
that should see them with an 'allmodconfig' kernel that has
CC_OPTIMIZE_FOR_SIZE enabled, but only later in randconfig builds
that don't.

This changes the Kconfig logic around CC_OPTIMIZE_FOR_SIZE to make
it a 'choice' statement defaulting to CC_OPTIMIZE_FOR_PERFORMANCE
that gets added for this purpose. The allmodconfig and allyesconfig
kernels now default to -O2 with the maybe-unused warning enabled.

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
init/Kconfig | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/init/Kconfig b/init/Kconfig
index 651ec15ecddb..159a542ef3fc 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1305,6 +1305,17 @@ source "usr/Kconfig"

endif

+choice
+ prompt "Compiler optimization level"
+ default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
+
+config CC_OPTIMIZE_FOR_PERFORMANCE
+ bool "Optimize for performance"
+ help
+ This is the default optimization level for the kernel, building
+ with the "-O2" compiler flag for best performance and most
+ helpful compile-time warnings.
+
config CC_OPTIMIZE_FOR_SIZE
bool "Optimize for size"
help
@@ -1313,6 +1324,8 @@ config CC_OPTIMIZE_FOR_SIZE

If unsure, say N.

+endchoice
+
config SYSCTL
bool

--
2.7.0