On Mon, May 02, 2011 at 02:53:38PM +1000, Stephen Rothwell wrote: > Hi Dave, > > hmmm, > > On my build machine: > $ /opt/cross/gcc-4.4.5-nolibc/x86_64-linux/bin/x86_64-linux-gcc -Wno-unused-but-set-variable -c -xc /dev/null -o /tmp/xx.o; echo $? > 0 > $ /opt/cross/gcc-4.4.5-nolibc/x86_64-linux/bin/x86_64-linux-gcc -Wunused-but-set-variable -c -xc /dev/null -o /tmp/xx.o; echo $? > cc1: error: unrecognized command line option "-Wunused-but-set-variable" > 1 > $ gcc -Wno-unused-but-set-variable -c -xc /dev/null -o /tmp/xx.o; echo $? > 0 > $ gcc -Wunused-but-set-variable -c -xc /dev/null -o /tmp/xx.o; echo $? > cc1: error: unrecognized command line option "-Wunused-but-set-variable" > 1 I reproduced this myself with 4.5.1 and 4.6.0 and was about to file a bug at gcc.gnu.org, but I learned that this is a feature :-(, see here: http://gcc.gnu.org/PR28322 . It treats invalid -Wno-* options as warnings and it only issues them when there is another warning or error in the source. I have a patch below, but after learning the above, I'm going to rewrite it to some more generic cc-disable-warning fuction, because it can hit us anytime again. Michal Subject: [PATCH] kbuild: Fix passing -Wno-unused-but-set-variable to some gcc versions Some versions of gcc will happily accept -Wno-<anything> in the cc-option test and complain later when compiling some random file that -Wno-unused-but-set-variable is not recognized. Work around this by testing if gcc supports the -Wunused-but-set-variable option insteaed. Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> Signed-off-by: Michal Marek <mmarek@xxxxxxx> diff --git a/Makefile b/Makefile index 4527dc2..db6b6df 100644 --- a/Makefile +++ b/Makefile @@ -569,7 +569,12 @@ 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 += $(call cc-option, -Wno-unused-but-set-variable) +# We test for support of the -Wunused-but-set-variable option, because +# some version of gcc will happily accept any -Wno-* switch and complain +# later during build. +ifeq ($(call cc-option-yn, -Wunused-but-set-variable), y) +KBUILD_CFLAGS += -Wno-unused-but-set-variable +endif ifdef CONFIG_FRAME_POINTER KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls -- 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
