path: root/Documentation/kbuild/makefiles.txt
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authorMichal Marek <mmarek@suse.cz>2011-05-02 12:51:15 +0200
committerMichal Marek <mmarek@suse.cz>2011-05-03 10:50:54 +0200
commit8417da6f2128008c431c7d130af6cd3d9079922e (patch)
tree79bfdaadfc1548826651b9b0378e70e60cdc7720 /Documentation/kbuild/makefiles.txt
parentkbuild: move scripts/basic/docproc.c to scripts/docproc.c (diff)
kbuild: Fix passing -Wno-* options to gcc 4.4+
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>
Diffstat (limited to 'Documentation/kbuild/makefiles.txt')
1 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index 835b64acf0b4..47435e56c5da 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 returns a numerical version of the $(CC) compiler version.
The format is <major><minor> where both are two digits. So for example