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Subject[PATCH v3.2] kbuild: implement several W= levels
Date
From: Sam Ravnborg <sam@ravnborg.org>

Building a kernel with "make W=1" produces far too much noise to be
useful.

Divide the warning options in three groups:

W=1 - warnings that may be relevant and does not occur too often
W=2 - warnings that occur quite often but may still be relevant
W=3 - the more obscure warnings, can most likely be ignored

When building the whole kernel, those levels produce:

W=1 - 4859 warnings
W=2 - 1394 warnings
W=3 - 86666 warnings
respectively. Warnings have been counted with Geert's script at

http://www.kernel.org/pub/linux/kernel/people/geert/linux-log/linux-log-summary.pl

Many warnings occur from .h files so fixing one file may have a nice
effect on the total number of warnings.

With these changes I am actually tempted to try W=1 now and then.
Previously there was just too much noise.

Borislav:

- make the W= levels exclusive
- move very noisy and making little sense for the kernel warnings to W=3
- drop -Woverlength-strings due to useless warning message
- copy explanatory text for the different warning levels to 'make help'
- recount warnings per level

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Borislav Petkov <bp@alien8.de>
Cc: Dave Jones <davej@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
---
Makefile | 8 ++++-
scripts/Makefile.build | 65 ++++++++++++++++++++++++++++--------------------
2 files changed, 44 insertions(+), 29 deletions(-)
diff --git a/Makefile b/Makefile
index 5a7a2e4..b2a6808 100644
--- a/Makefile
+++ b/Makefile
@@ -103,7 +103,7 @@ ifeq ("$(origin O)", "command line")
endif

ifeq ("$(origin W)", "command line")
- export KBUILD_ENABLE_EXTRA_GCC_CHECKS := 1
+ export KBUILD_ENABLE_EXTRA_GCC_CHECKS := $(W)
endif

# That's our default target when none is given on the command line
@@ -1267,7 +1267,11 @@ 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 ' make W=n [targets] Enable extra gcc checks, n=1,2,3 where'
+ @echo ' 1: warnings which may be relevant and do not occur too often'
+ @echo ' 2: warnings which occur quite often but may still be relevant'
+ @echo ' 3: more obscure warnings, can most likely be ignored'
+
@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/Makefile.build b/scripts/Makefile.build
index d5f925a..ffb383c 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -51,36 +51,47 @@ ifeq ($(KBUILD_NOPEDANTIC),)
endif

#
-# make W=1 settings
+# make W=... settings
#
-# $(call cc-option... ) handles gcc -W.. options which
+# W=1 - warnings that may be relevant and does not occur too often
+# W=2 - warnings that occur quite often but may still be relevant
+# W=3 - the more obscure warnings, can most likely be ignored
+#
+# $(call cc-option, -W...) handles gcc -W.. options which
# are not supported by all versions of the compiler
ifdef KBUILD_ENABLE_EXTRA_GCC_CHECKS
-KBUILD_EXTRA_WARNINGS := -Wextra
-KBUILD_EXTRA_WARNINGS += -Wunused -Wno-unused-parameter
-KBUILD_EXTRA_WARNINGS += -Waggregate-return
-KBUILD_EXTRA_WARNINGS += -Wbad-function-cast
-KBUILD_EXTRA_WARNINGS += -Wcast-qual
-KBUILD_EXTRA_WARNINGS += -Wcast-align
-KBUILD_EXTRA_WARNINGS += -Wconversion
-KBUILD_EXTRA_WARNINGS += -Wdisabled-optimization
-KBUILD_EXTRA_WARNINGS += -Wlogical-op
-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
-KBUILD_EXTRA_WARNINGS += -Wpacked-bitfield-compat
-KBUILD_EXTRA_WARNINGS += -Wpadded
-KBUILD_EXTRA_WARNINGS += -Wpointer-arith
-KBUILD_EXTRA_WARNINGS += -Wredundant-decls
-KBUILD_EXTRA_WARNINGS += -Wshadow
-KBUILD_EXTRA_WARNINGS += -Wswitch-default
-KBUILD_EXTRA_WARNINGS += $(call cc-option, -Wvla,)
-KBUILD_CFLAGS += $(KBUILD_EXTRA_WARNINGS)
+warning-1 := -Wextra -Wunused -Wno-unused-parameter
+warning-1 += -Wmissing-declarations
+warning-1 += -Wmissing-format-attribute
+warning-1 += -Wmissing-prototypes
+warning-1 += -Wold-style-definition
+warning-1 += $(call cc-option, -Wmissing-include-dirs)
+
+warning-2 := -Waggregate-return
+warning-2 += -Wcast-align
+warning-2 += -Wdisabled-optimization
+warning-2 += -Wnested-externs
+warning-2 += -Wshadow
+warning-2 += $(call cc-option, -Wlogical-op)
+
+warning-3 := -Wbad-function-cast
+warning-3 += -Wcast-qual
+warning-3 += -Wconversion
+warning-3 += -Wpacked
+warning-3 += -Wpadded
+warning-3 += -Wpointer-arith
+warning-3 += -Wredundant-decls
+warning-3 += -Wswitch-default
+warning-3 += $(call cc-option, -Wpacked-bitfield-compat)
+warning-3 += $(call cc-option, -Wvla)
+
+warning := $(warning-$(KBUILD_ENABLE_EXTRA_GCC_CHECKS))
+
+ifeq ("$(warning)","")
+ $(error W=$(KBUILD_ENABLE_EXTRA_GCC_CHECKS) is unknown)
+endif
+
+KBUILD_CFLAGS += $(warning)
endif

include scripts/Makefile.lib
--
1.7.5.rc1.16.g9db1


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