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    Subject[PATCH 88/91] kbuild: Fix passing -Wno-* options to gcc 4.4+
    2.6.27-longterm review patch.  If anyone has any objections, please let us know.

    ------------------

    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>
    ---
    Documentation/kbuild/makefiles.txt | 12 ++++++++++++
    Makefile | 4 ++--
    scripts/Kbuild.include | 5 +++++
    3 files changed, 19 insertions(+), 2 deletions(-)

    Index: longterm-2.6.27/Documentation/kbuild/makefiles.txt
    ===================================================================
    --- longterm-2.6.27.orig/Documentation/kbuild/makefiles.txt 2012-02-05 22:34:32.253915069 +0100
    +++ longterm-2.6.27/Documentation/kbuild/makefiles.txt 2012-02-05 22:34:47.409917106 +0100
    @@ -471,6 +471,18 @@
    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
    Index: longterm-2.6.27/Makefile
    ===================================================================
    --- longterm-2.6.27.orig/Makefile 2012-02-05 22:34:47.271916824 +0100
    +++ longterm-2.6.27/Makefile 2012-02-05 22:34:47.412915249 +0100
    @@ -531,7 +531,7 @@
    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)

    ifdef CONFIG_FRAME_POINTER
    KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls
    @@ -561,7 +561,7 @@
    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" optimzations for signed / pointers
    KBUILD_CFLAGS += $(call cc-option,-fno-strict-overflow)
    Index: longterm-2.6.27/scripts/Kbuild.include
    ===================================================================
    --- longterm-2.6.27.orig/scripts/Kbuild.include 2012-02-05 22:34:32.256915061 +0100
    +++ longterm-2.6.27/scripts/Kbuild.include 2012-02-05 22:34:47.418914568 +0100
    @@ -117,6 +117,11 @@
    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))



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