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authorMichal Marek <mmarek@suse.cz>2011-05-02 12:51:15 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2011-11-26 09:10:36 -0800
commitf4cf7f671c87c93233386fab0d70db807dc1b5ac (patch)
parent85c269fa465918e1ba4668cf8c04de68e7b2298d (diff)
kbuild: Fix passing -Wno-* options to gcc 4.4+
commit 8417da6f2128008c431c7d130af6cd3d9079922e upstream. 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-and-tested-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Michal Marek <mmarek@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
3 files changed, 19 insertions, 2 deletions
diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index 71c602d61680..ab8689b94d65 100644
--- a/Documentation/kbuild/makefiles.txt
+++ b/Documentation/kbuild/makefiles.txt
@@ -502,6 +502,18 @@ 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 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 3cc6d4f68608..1357fe91313e 100644
--- a/Makefile
+++ b/Makefile
@@ -538,7 +538,7 @@ KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
# This warning generated too much noise in a regular build.
-KBUILD_CFLAGS += $(call cc-option, -Wno-unused-but-set-variable)
+KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls
@@ -568,7 +568,7 @@ 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 c67e73ecd5be..92b62a8db0f8 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))