linux-kernel - RE: [PATCH -rc v1] gcov: Disable gcov build with GCC 10

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Date:   Thu, 10 Sep 2020 21:49:20 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Linus Torvalds' <torvalds@...ux-foundation.org>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>
CC:     Leon Romanovsky <leon@...nel.org>,
        Leon Romanovsky <leonro@...dia.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Colin Ian King <colin.king@...onical.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: RE: [PATCH -rc v1] gcov: Disable gcov build with GCC 10

From: Linus Torvalds
> Sent: 10 September 2020 20:19
> 
> On Thu, Sep 10, 2020 at 5:52 AM Peter Oberparleiter
> <oberpar@...ux.ibm.com> wrote:
> >
> > Fix this by updating the in-kernel GCOV_COUNTERS value. Also re-enable
> > config GCOV_KERNEL for use with GCC 10.
> 
> Lovely.
> 
> Is there some way we could see this value automatically, or at least
> have a check for it? Right now it's that _very_ magical number that
> depends on a gcc version in odd and undocumented ways..
> 
> IOW - I'm assuming user space gcov infrastructure finds this number
> some way, and wondering if we couldn't do the same?
> 
> Or is the gcov tool itself just doing the same kind of thing, and
> having magic numbers?
> 
> I get the feeling that somebody who knows gcov would go "You are just
> doing this all completely incorrectly, you should do XYZ" when they
> see that GCOV_COUNTERS thing.
> 
> Maybe just a script that finds the right header file in the gcc
> installation and extracts it from there, if only to verify the magic
> number that we have?

I was wondering what happens if files compiled with different
versions of gcc get linked together?

Not too far-fetched for someone to release a .a file containing
'gconv' objects.

	David

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