linux-kernel - Re: [PATCH] gcov: support GCC 7.1

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Date:   Wed, 9 Nov 2016 10:21:29 +0100
From:   Peter Oberparleiter <oberpar@...ux.vnet.ibm.com>
To:     Martin Liška <mliska@...e.cz>
Cc:     lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gcov: support GCC 7.1

On 31.10.2016 10:35, Martin Liška wrote:
> Starting from GCC 7.1, __gcov_exit is a new symbol expected
> to be implemented in a profiling runtime.

I tested your patch with kernel 4.9-rc4 compiled with GCC 7.0.0 20161107
(experimental) and validated that it fixes the build error due to a
missing __gcov_exit symbol.

An attempt to read from one of the .gcda files generated by a kernel
compiled this way resulted in a crash though. It appears that the number
of GCOV_COUNTERS has changed again for GCC 7.x and must be adjusted in
the kernel as well. Could you add that to your patch as well?

Given that GCC 7.1 has not yet been released, I'm wondering if it is
safe to program against interfaces that have not yet been fully
finalized. Can you provide an indication on whether these gcov-related
aspects of GCC might still be changed until release?

As a side note, please post your patches inline instead of as attachment
as that helps quoting them in replies. See also
linux/Documentation/SubmittingPatches.

-- 
Peter Oberparleiter
Linux on z Systems Development - IBM Germany