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From: Daniel Axtens <dja@axtens.net>
To: Andrew Morton <akpm@linux-foundation.org>,
	kbuild test robot <lkp@intel.com>
Cc: kbuild-all@lists.01.org, Johannes Weiner <hannes@cmpxchg.org>,
	Dmitry Vyukov <dvyukov@google.com>,
	Linux Memory Management List <linux-mm@kvack.org>
Subject: Re: [hnaz-linux-mm:master 169/698] include/linux/string.h:307:9: note: in expansion of macro '__underlying_strncpy'
Date: Tue, 02 Jun 2020 13:53:22 +1000	[thread overview]
Message-ID: <87tuzuyvgt.fsf@dja-thinkpad.axtens.net> (raw)
In-Reply-To: <87wo4qywp4.fsf@dja-thinkpad.axtens.net>

Daniel Axtens <dja@axtens.net> writes:

> Hi Andrew,
>
>>> include/linux/string.h:297:30: warning: '__builtin_strncpy' specified bound 8 equals destination size [-Wstringop-truncation]
>>> 297 | #define __underlying_strncpy __builtin_strncpy
>>> |                              ^
>>> >> include/linux/string.h:307:9: note: in expansion of macro '__underlying_strncpy'
>>> 307 |  return __underlying_strncpy(p, q, size);
>>> |         ^~~~~~~~~~~~~~~~~~~~
>>
>> Looks like another false positive.
>>
>> Daniel, is there a practical way of suppressing these?
>
> I think we probably want '-Wno-stringop-truncation'. That will stop
> warnings where the bound equals the destination size (so there won't be
> any null-truncation). But it won't stop the overflow warnings about
> full-on overflows (-Wstringop-overflow).

Ah, so both stringop-truncate and stringop-overflow are disabled in
Makefile:
 - commit 5a76021c2eff ("gcc-10: disable 'stringop-overflow' warning for now")
 - commit 217c3e019675 ("disable stringop truncation warnings for now")

However, at W=1, stringop-truncate is re-enabled - last touched commit
64a91907c896 ("kbuild: refactor scripts/Makefile.extrawarn"). That would
explain why we see this on test builds with W=1 only.

I'll bump it to W=2.

> I'll send a patch.
>
> Regards,
> Daniel


  reply	other threads:[~2020-06-02  3:53 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-30 10:07 [hnaz-linux-mm:master 169/698] include/linux/string.h:307:9: note: in expansion of macro '__underlying_strncpy' kbuild test robot
2020-06-02  1:04 ` Andrew Morton
2020-06-02  3:26   ` Daniel Axtens
2020-06-02  3:53     ` Daniel Axtens [this message]
2020-06-02  5:55       ` Daniel Axtens
2020-06-02 19:16         ` Andrew Morton
2020-06-05 10:35           ` Daniel Axtens

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