Problems building ppc images in v4.14.y and v4.16.y using gcc 7.3.0 / 8.1.0 from kernel.org

[Arnd Bergmann]

On Tue, Jun 5, 2018 at 6:06 PM, Guenter Roeck <linux at roeck-us.net> wrote:
> On Tue, Jun 05, 2018 at 04:31:00PM +0200, Arnd Bergmann wrote:
>> On Tue, Jun 5, 2018 at 3:52 PM, Guenter Roeck <linux at roeck-us.net> wrote:
>> > Hi Arnd,
>> >
>> > when using the ppc64 compiler from kernel.org, I see the following problems
>> > when trying to compile ppc:allnoconfig in v4.14.y or v4.16.y.
>> >
>> > gcc 7.3.0: Compilation of kernel.cpu.o hangs
>> >
>> > The problem goes away if I apply the following two patches (tested with
>> > 4.16.y)
>> >
>> > 17a2f1ced028 cpu/hotplug: Merge cpuhp_bp_states and cpuhp_ap_states
>> > fcb3029a8d89 cpu/hotplug: Fix unused function warning
>>
>> This is probably the same as
>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84038
>>
>> I thought I had included the fix in my builds.
>>
> Guess not.

I probably had it in one build and then forgot about it when I did a
rebuild of 7.3 :(

I'm still planning to do a new set of gcc-7.3 binaries (or maybe 7.4
if that gets
released soon) and should try to remember doing that.

>>
> I think it may have cached the flags from the other compiler version.
> "make mrproper" prior to "make defconfig" took care of the issue.
>
> However, that doesn't really help - I get lots of
>         error: 'sys_spu_create' alias between functions of incompatible types
>         error: 'strncpy' output truncated before terminating nul
> if I try to use gcc 8.1.0.
>
> Oh well. I'll try gcc 6.4.0 next.

On the upside, those two errors are just a result of arch/power/*/*.c getting
built with -Werror, they are warnings that gcc-8 introduced that we should
either shut up or fix.

        Arnd