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

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Message-ID: <20180910092835.v5nex5nzfgtl475m@ltop.local>
Date:   Mon, 10 Sep 2018 11:28:36 +0200
From:   Luc Van Oostenryck <luc.vanoostenryck@...il.com>
To:     Christophe LEROY <christophe.leroy@....fr>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>, 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")

On Mon, Sep 10, 2018 at 08:49:07AM +0200, Christophe LEROY wrote:
> Le 07/09/2018 à 20:19, Nick Desaulniers a écrit :
> > On Fri, Sep 7, 2018 at 11:13 AM Luc Van Oostenryck wrote:
> > > 
> > > 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.

OK, I see.
 
> Is there a way to get sparse in line with my cross compiler version
> and not with the local native version ?

When cross-compiling, there is also things like the machine word-size
and the endianness to take in account (they also default to the
native compiler used to compile sparse itself) as well as a few
defines (like __PPC64__). To be in line with your cross-compiler
you can use to the wrapper 'cgcc' (installed with sparse) and call
it, for example, like this:
	$ export REAL_CC=ppc-linux-gcc
	$ cgcc -target=ppcc64 -D_CALL_ELF=2 -D__GCC__=5 -D__GCC_MINOR__=4 ...
or, since this is for the kernel:
	$ export REAL_CC=ppc-linux-gcc
	$ make CHECK='cgcc -target=ppcc64 ...


I think this should solve it. Do not hesitate to report any
difficulties you may encounter.

-- Luc