Starting with 4.4, gcc will happily accept -Wno-<anything> in the cc-option test and complain later when compiling a file that has some other warning. This rather unexpected behavior is intentional as per http://gcc.gnu.org/PR28322, so work around it by testing for support of the opposite option (without the no-). Introduce a new Makefile function cc-disable-warning that does this and update two uses of cc-option in the toplevel Makefile. Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> Signed-off-by: Michal Marek <mmarek@xxxxxxx> --- Documentation/kbuild/makefiles.txt | 12 ++++++++++++ Makefile | 4 ++-- scripts/Kbuild.include | 5 +++++ 3 files changed, 19 insertions(+), 2 deletions(-) diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index 835b64a..47435e5 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt @@ -501,6 +501,18 @@ more details, with real examples. gcc >= 3.00. For gcc < 3.00, -malign-functions=4 is used. Note: cc-option-align uses KBUILD_CFLAGS for $(CC) options + cc-disable-warning + cc-disable-warning checks if gcc supports a given warning and returns + the commandline switch to disable it. This special function is needed, + because gcc 4.4 and later accept any unknown -Wno-* option and only + warn about it if there is another warning in the source file. + + Example: + KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) + + In the above example, -Wno-unused-but-set-variable will be added to + KBUILD_CFLAGS only if gcc really accepts it. + cc-version cc-version returns a numerical version of the $(CC) compiler version. The format is <major><minor> where both are two digits. So for example diff --git a/Makefile b/Makefile index 4527dc2..f919209 100644 --- a/Makefile +++ b/Makefile @@ -569,7 +569,7 @@ endif # This warning generated too much noise in a regular build. # Use make W=1 to enable this warning (see scripts/Makefile.build) -KBUILD_CFLAGS += $(call cc-option, -Wno-unused-but-set-variable) +KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) ifdef CONFIG_FRAME_POINTER KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls @@ -616,7 +616,7 @@ CHECKFLAGS += $(NOSTDINC_FLAGS) KBUILD_CFLAGS += $(call cc-option,-Wdeclaration-after-statement,) # disable pointer signed / unsigned warnings in gcc 4.0 -KBUILD_CFLAGS += $(call cc-option,-Wno-pointer-sign,) +KBUILD_CFLAGS += $(call cc-disable-warning, pointer-sign) # disable invalid "can't wrap" optimizations for signed / pointers KBUILD_CFLAGS += $(call cc-option,-fno-strict-overflow) diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index fae2d8d..c034dd7 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -118,6 +118,11 @@ cc-option-yn = $(call try-run,\ cc-option-align = $(subst -functions=0,,\ $(call cc-option,-falign-functions=0,-malign-functions=0)) +# cc-disable-warning +# Usage: cflags-y += $(call cc-disable-warning,unused-but-set-variable) +cc-disable-warning = $(call try-run,\ + $(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -W$(strip $(1)) -c -xc /dev/null -o "$$TMP",-Wno-$(strip $(1))) + # cc-version # Usage gcc-ver := $(call cc-version) cc-version = $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-version.sh $(CC)) -- 1.7.4.1 -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
