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    SubjectRe: v3.18.86 build: 0 failures 1 warnings (v3.18.86)
    On Wed, Jan 3, 2018 at 10:57 AM, Greg KH <gregkh@linuxfoundation.org> wrote:
    > On Wed, Jan 03, 2018 at 10:54:16AM +0100, Greg KH wrote:
    >> On Wed, Jan 03, 2018 at 12:24:12AM +0100, Arnd Bergmann wrote:
    >> > On Wed, Dec 6, 2017 at 1:18 AM, Build bot for Mark Brown
    >> > <broonie@kernel.org> wrote:
    >> >
    >> > > -------------------------------------------------------------------------------
    >> > > x86_64-defconfig : PASS, 0 errors, 2 warnings, 0 section mismatches
    >> > >
    >> > > Warnings:
    >> > > ../include/linux/ftrace.h:632:36: warning: calling '__builtin_return_address' with a nonzero argument is unsafe [-Wframe-address]
    >> > > ../include/linux/ftrace.h:632:36: warning: calling '__builtin_return_address' with a nonzero argument is unsafe [-Wframe-address]
    >> > > -------------------------------------------------------------------------------
    >> >
    >> > This warning keeps coming up in 3.18 and 4.1 builds, which lack a backport of
    >> >
    >> > ef6000b4c670 ("Disable the __builtin_return_address() warning globally
    >> > after all")
    >> >
    >> > The other build bots use different gcc versions that don't report the
    >> > warning here,
    >> > so only Mark's bot triggers it. The warning in this file is harmless,
    >> > and the patch
    >> > only turns off the warning flag.
    >>
    >> Ah, I tried to figure this one out in the past, thanks for this, I'll
    >> queue it up soon. Hm, this isn't in 4.4.y, why is it not showing up
    >> there? Due to a different backport of this type of thing?
    >
    > Nope, doesn't apply to 3.18 at all, as the main part of this patch is
    > already in there. I don't really understand it, it seems that the
    > cc-disable-warning option isn't working for me for 3.18 at all in my
    > local builds. I spent a few hours on it last week, but gave up in the
    > end :(

    Right, this is more mysterious than I thought. I see now that the original
    patch 124a3d88fa20 ("Disable "frame-address" warning") was backported
    into 3.18, just not the revert 377ccbb48373 ("Makefile: Mute warning for
    __builtin_return_address(>0) for tracing only") and the subsequent
    revert^2 ef6000b4c670 ("Disable the __builtin_return_address() warning
    globally after all").

    I have checked that on my build box, the warning is successfully
    disabled with gcc-6 and higher (tried 6.1.1, 6.3.1, 7.0.0, 7.1.1)
    and older compilers have neither the warning nor the option
    to disable it.
    I also tried reproducing the warning on arm and aarch64 with some
    other modifications but I get a different warning there:

    kernel/sched/core.c: In function 'preempt_count_sub':
    include/linux/ftrace.h:632:36: warning: unsupported argument to
    '__builtin_return_address'

    Greg and Mark, which x86-64 compiler versions do you use?

    Arnd

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