linux-kernel - Re: Conflict between sparse and commit cafa0010cd51f ("Raise the minimum required gcc version to 4.6")

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Date:   Mon, 10 Sep 2018 08:49:07 +0200
From:   Christophe LEROY <christophe.leroy@....fr>
To:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>
Cc:     joe@...ches.com, Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-sparse@...r.kernel.org, sparse@...isli.org
Subject: Re: Conflict between sparse and commit cafa0010cd51f ("Raise the
 minimum required gcc version to 4.6")



Le 07/09/2018 à 20:19, Nick Desaulniers a écrit :
> On Fri, Sep 7, 2018 at 11:13 AM Luc Van Oostenryck
> <luc.vanoostenryck@...il.com> wrote:
>>
>> On Fri, Sep 07, 2018 at 10:22:56AM -0700, Nick Desaulniers wrote:
>>> On Fri, Sep 7, 2018 at 7:34 AM Christophe LEROY <christophe.leroy@....fr> wrote:
>>>>
>>>> Cc linux-sparse@...r.kernel.org
>>>>
>>>> Le 07/09/2018 à 14:22, Christophe Leroy a écrit :
>>>>> Since commit cafa0010cd51f ("Raise the minimum required gcc version to
>>>>> 4.6"), sparse check fails as follows:
>>>>>
>>>>> [root@...6082vm linux-powerpc]# make C=2 arch/powerpc/kernel/process.o
>>>>>     CALL    scripts/checksyscalls.sh
>>>>>     CHECK   scripts/mod/empty.c
>>>>> ./include/linux/compiler-gcc.h:14:3: error: Sorry, your compiler is too
>>>>> old - please upgrade it.
>>>>>     CHECK   arch/powerpc/kernel/process.c
>>>>> ./include/linux/compiler-gcc.h:14:3: error: Sorry, your compiler is too
>>>>> old - please upgrade it.
>>>>>
>>>>>
>>>>> I have sparse version 0.5.2
>>>>>
>>>>> What can be done to fix that ?
>>>>>
>>>>> Christophe
>>>
>>> Oof, sorry Christophe.  Looks like that's the latest version of sparse:
>>> https://sparse.wiki.kernel.org/index.php/Main_Page#News
>>>
>>> I'm curious what sparse expands __GNUC__, __GNUC_MINOR__, and
>>> __GNUC_PATCHLEVEL__ to?  Pre commit cafa0010cd51f, it MUST be
>>> expanding them to something, otherwise you'd have seen the error then,
>>> too.  The previous check was GCC < 3.3, now it's GCC < 4.6.
>>
>> Sparse expand these macros to the same version than the compiler used
>> to compile GCC. I find a bit strange though to have sparse v0.5.2 but
>> using an old compiler.
> 
> So Christophe must have a version of gcc < 4.6 installed somewhere?
> Does sparse use `cc`? If so, Christophe, does your `ls -l $(which cc)`
> point to an old version of gcc maybe?

Indeed it looks like sparse expand these macros to the version of the 
compiler it was compiled with.

I'm building kernels for a powerpc platforms, with CROSS_COMPILE set to 
ppc-linux- and ppc-linux-gcc being version 5.4

However my build machine is a CentOS6 and the native gcc has version 
4.4.7, so sparse expands that version.

Is there a way to get sparse in line with my cross compiler version and 
not with the local native version ?

Christophe

> 
>>
>> Also, it's worth to look at what is said in this email:
>>    https://lore.kernel.org/lkml/CA+55aFzYEnZR2GZLR-DwpONjMNYGYoDy+6AWLCVNayWiaZuqoA@mail.gmail.com/
>>
>>
>> -- Luc
> 
> 
>