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

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Message-ID: <CAMuHMdV9W4hDeVW2=jP0YN1vF1mjbr0-4nrcLWi=H1mR214EtQ@mail.gmail.com>
Date:   Tue, 8 Jan 2019 15:09:42 +0100
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>,
        Rik van Riel <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>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>
Subject: Re: [PATCH] Raise the minimum required gcc version to 4.6

On Sat, Dec 29, 2018 at 3:25 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> On Fri, Aug 24, 2018 at 12:00 AM Joe Perches <joe@...ches.com> wrote:
> > On Thu, 2018-08-23 at 23:52 +0200, Geert Uytterhoeven wrote:
> > > Reverted locally (incl. the follow-up), applied Andrew's fix, detected new
> > > warnings in v4.18+, and sent patches where it makes sense...
> >
> > Thanks for that.
>
> Given the rise of anonymous unions all over the place, I gave up, and
> have upgraded from gcc 4.1.2 to 7.3.0 for cross-compiling m68k kernels.
> One good things is that the kernel size for an atari_defconfig kernel dropped
> by 3.7% or 163 KiB.
>
> For the record, below is a list of differences in generated warnings.
> Note that the source trees are not identical, as the tree used with
> gcc-7.3.0 did not include any workarounds I needed for gcc-4.1.2.
> All warnings flagged by gcc 4.1.2 should be false positives (iff I did a
> good job during the last few years ;-)
>
> I plan to repeat the exercise with gcc-8.2.0 (after v4.21-rc1 or so).

As promised, gcc-7.3.0 => gcc-8.2.0:

    *** ERRORS ***

    4 error regressions:
      + error: devfreq.c: undefined reference to `strcmp':  => .text+0x9c6)
      + error: ldm.c: undefined reference to `strcmp':  =>
.text+0x1900), .text+0x1964), .text+0x19a0), .text+0x193c)
      + error: proc.c: undefined reference to `strcmp':  =>
.text+0x18c), .text+0x178)
      + error: xattr.c: undefined reference to `strcmp':  =>
.text+0xbaa), .text+0xbf0), .text+0x2e8), .text+0x268), .text+0x97a),
.text+0x9be), .text+0x3d4)

Hmm, time to fix the auto-strncmp-to-strcmp-conversion for good...

    *** WARNINGS ***

    1 warning regressions:
      + drivers/dio/dio.c: warning: ‘strcpy’ writing 69 or more bytes
into a region of size 64 overflows the destination
[-Wstringop-overflow=]:  => 240:17

That's a nice one, it found a 15 year old bug. Patch sent ;-)

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