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From: Borislav Petkov <>
To: Sam Ravnborg <>, Michal Marek <>
Cc:,,, Ingo Molnar <>,,
Subject: [PATCH -v4] kbuild: Add extra gcc checks
Date: Mon, 21 Feb 2011 12:03:22 +0100
Message-ID: <20110221110322.GA9819@liondog.tnic> (raw)

Add a 'W=1' Makefile switch which adds additional checking per build

The idea behind this option is targeted at developers who, in the
process of writing their code, want to do the occasional

make W=1 [target.o]

and let gcc do more extensive code checking for them. Then, they
could eyeball the output for valid gcc warnings about various
bugs/discrepancies which are not reported during the normal build

For more background information and a use case, read through this

-v4: Enable this for gcc only. Also, check for options which are not
supported by every gcc version we use to build the kernel. Adding those
checks for _every_ option slows down the build noticeably so be sensible
here and add it only when your gcc version chokes on a particular

-v[2..3]: move to

Cc: Michal Marek <>
Cc: Sam Ravnborg <>
Acked-by: Ingo Molnar <>
Signed-off-by: Borislav Petkov <>
 Makefile               |    6 ++++++
 scripts/ |   37 ++++++++++++++++++++++++++++++++++++-
 2 files changed, 42 insertions(+), 1 deletions(-)

diff --git a/Makefile b/Makefile
index c9c8c8f..c3bca9c 100644
--- a/Makefile
+++ b/Makefile
@@ -102,6 +102,11 @@ ifeq ("$(origin O)", "command line")
+ifeq ("$(origin W)", "command line")
 # That's our default target when none is given on the command line
 PHONY := _all
@@ -1262,6 +1267,7 @@ help:
 	@echo  '  make O=dir [targets] Locate all output files in "dir", including .config'
 	@echo  '  make C=1   [targets] Check all c source with $$CHECK (sparse by default)'
 	@echo  '  make C=2   [targets] Force check of all c source with $$CHECK'
+	@echo  '  make W=1   [targets] Enable extra gcc checks'
 	@echo  ''
 	@echo  'Execute "make" or "make all" to build all targets marked with [*] '
 	@echo  'For further info see the ./README file'
diff --git a/scripts/ b/scripts/
index 4eb99ab..fa4b40d 100644
--- a/scripts/
+++ b/scripts/
@@ -49,6 +49,42 @@ ifeq ($(KBUILD_NOPEDANTIC),)
                 $(error CFLAGS was changed in "$(kbuild-file)". Fix it to use EXTRA_CFLAGS)
+# make W=1 settings
+# $(call cc-option... ) handles gcc -W.. options which
+# are not supported by all versions of the compiler
+ifneq ($(call cc-version),)
+KBUILD_EXTRA_WARNINGS += -Wunused -Wno-unused-parameter
+KBUILD_EXTRA_WARNINGS += -Waggregate-return
+KBUILD_EXTRA_WARNINGS += -Wbad-function-cast
+KBUILD_EXTRA_WARNINGS += -Wdisabled-optimization
+KBUILD_EXTRA_WARNINGS += -Wmissing-declarations
+KBUILD_EXTRA_WARNINGS += -Wmissing-format-attribute
+KBUILD_EXTRA_WARNINGS += $(call cc-option, -Wmissing-include-dirs,)
+KBUILD_EXTRA_WARNINGS += -Wmissing-prototypes
+KBUILD_EXTRA_WARNINGS += -Wnested-externs
+KBUILD_EXTRA_WARNINGS += -Wold-style-definition
+KBUILD_EXTRA_WARNINGS += $(call cc-option, -Woverlength-strings,)
+KBUILD_EXTRA_WARNINGS += -Wpacked-bitfield-compat
+KBUILD_EXTRA_WARNINGS += -Wpointer-arith
+KBUILD_EXTRA_WARNINGS += -Wredundant-decls
+KBUILD_EXTRA_WARNINGS += -Wswitch-default
+KBUILD_EXTRA_WARNINGS += $(call cc-option, -Wvla,)
 include scripts/Makefile.lib
 ifdef host-progs
@@ -403,7 +439,6 @@ ifneq ($(cmd_files),)
   include $(cmd_files)
 # Declare the contents of the .PHONY variable as phony.  We keep that
 # information in a variable se we can use it in if_changed and friends.


             reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-02-21 11:03 Borislav Petkov [this message]
2011-02-28 18:24 ` Borislav Petkov
2011-02-28 18:38 ` Sam Ravnborg
2011-02-28 21:07 ` Arnd Bergmann
2011-02-28 21:31   ` Borislav Petkov
2011-03-01 11:35     ` Arnd Bergmann
2011-03-01 13:20       ` Américo Wang
2011-03-01 14:56         ` Borislav Petkov

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