From: Florian Weimer <fweimer@redhat.com>
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>,
Paul Eggert <eggert@cs.ucla.edu>,
libc-alpha@sourceware.org
Subject: Re: [PATCH] libio: Add small optimization on fmemopen
Date: Wed, 21 Sep 2016 18:23:00 -0000 [thread overview]
Message-ID: <708fc89d-fbb9-cb20-9ee6-079013baf63b@redhat.com> (raw)
In-Reply-To: <03eb21f7-6979-62eb-0fe8-34ea35b0c7d6@linaro.org>
On 09/21/2016 08:17 PM, Adhemerval Zanella wrote:
>
>
> On 21/09/2016 14:22, Paul Eggert wrote:
>> On 09/21/2016 07:05 AM, Adhemerval Zanella wrote:
>>> + clen += len;
>>
>> That might cause problems , as the C standard says you can't access a flexible array member past the last byte that is properly aligned for the containing structure, and GCC relies on this when generating code (see GCC bug 66661). One way to work around the problem is to change the earlier:
>>
>> + size_t clen = sizeof (fmemopen_cookie_t);
>>
>> to:
>>
>> + size_t clen = sizeof (fmemopen_cookie_t) + _Alignof (fmemopen_cookie_t) - 1;
>>
>> This may overallocate a bit, but that's OK here.
>>
>
> Thanks for pointing this out, I think this is the safe approach regarding
> Florian comment #10 and #11. I will change it.
Please don't, it's a defect in the standard (and GCC"s Address Sanitizer
has a bug as well).
Florian
next prev parent reply other threads:[~2016-09-21 18:23 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-21 14:06 Adhemerval Zanella
2016-09-21 14:57 ` Florian Weimer
2016-09-21 18:18 ` Adhemerval Zanella
2016-09-21 17:22 ` Paul Eggert
2016-09-21 18:17 ` Adhemerval Zanella
2016-09-21 18:23 ` Florian Weimer [this message]
2016-09-21 18:26 ` Adhemerval Zanella
2016-09-21 18:43 ` Paul Eggert
2016-09-21 18:47 ` Florian Weimer
2016-09-21 18:57 ` Paul Eggert
2016-09-21 19:27 ` Florian Weimer
2016-09-21 20:16 ` Adhemerval Zanella
2016-09-21 20:42 ` Paul Eggert
2016-09-23 5:17 ` Ondřej Bílka
2016-09-23 5:34 ` Florian Weimer
2016-09-23 18:14 ` Ondřej Bílka
2016-09-23 20:38 ` Florian Weimer
2016-09-23 18:29 ` Paul Eggert
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