linux-kernel - Re: [PATCH] Raise the minimum required gcc version to 4.6

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Message-ID: <CAMuHMdXPFgp5sLR5-UExEvxNbKSR5H--dk7KMit_XFSFN+1uHw@mail.gmail.com>
Date:   Thu, 23 Aug 2018 23:52:40 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Joe Perches <joe@...ches.com>
Cc:     "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Mike Galbraith <efault@....de>,
        Guenter Roeck <linux@...ck-us.net>, riel@...riel.com,
        Kees Cook <keescook@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] Raise the minimum required gcc version to 4.6

Hi Joe,

On Mon, Aug 20, 2018 at 10:15 PM Joe Perches <joe@...ches.com> wrote:
> Various architectures fail to build properly with older versions
> of the gcc compiler.
>
> An example from Guenter Roeck via this thread:
> https://lore.kernel.org/lkml/20180814170904.GA12768@roeck-us.net/
>
> ----------------------
> In file included from ./include/linux/mm.h:17:0,
>                  from ./include/linux/pid_namespace.h:7,
>                  from ./include/linux/ptrace.h:10,
>                  from arch/openrisc/kernel/asm-offsets.c:32:
> ./include/linux/mm_types.h:497:16: error: flexible array member in otherwise empty struct
>
> This is just an example with gcc 4.5.1 for or32. I have seen the problem
> with gcc 4.4 (for unicore32) as well.
> ----------------------
>
> So update the minimum required version of gcc to 4.6.
>
> Miscellanea:
>
> o Update Documentation/process/changes.rst
> o Remove and consolidate version test blocks in compiler-gcc.h
>   for versions lower than 4.6
>
> Signed-off-by: Joe Perches <joe@...ches.com>
> Reviewed-by: Kees Cook <keescook@...omium.org>
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

Thanks for your patch!

I'm willing to upgrade. But there's one thing that's holding me back.

Does gcc 8.x gives again the same warnings as my venerable old gcc 4.1.2,
that no one else seems to see? Or will the real bugs I detect this way stay
unfixed? Polyculture is a good thing, also in compilers.

Reverted locally (incl. the follow-up), applied Andrew's fix, detected new
warnings in v4.18+, and sent patches where it makes sense...

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds