From: Ian Lance Taylor <iant@google.com>
To: Nathan Boley <npboley@gmail.com>
Cc: gcc@gcc.gnu.org
Subject: Re: Possible Bug
Date: Sun, 27 Mar 2011 07:38:00 -0000 [thread overview]
Message-ID: <mcrd3ldi3wf.fsf@google.com> (raw)
In-Reply-To: <AANLkTinhFkPH4+0wzV+gGGf-CJNTnOi5MQ1-bQgJJkPK@mail.gmail.com> (Nathan Boley's message of "Sat, 26 Mar 2011 13:03:57 -0700")
Nathan Boley <npboley@gmail.com> writes:
> In a much larger application, I was getting a weird segfault that an
> assignment to a temporary variable fixed. I distilled the example into
> the attached "test_case.c". When I run test_case.c under valgrind I
> get a memory read error, and it segfaults with electric fence, but I'm
> not actually able to get a true segfault. However, I am pretty sure
> that the same issue was causing the segfault in my application.
There is nothing wrong if gcc is reading an 8-byte value at an 8-byte
aligned address. That can not cause a memory read error. To a program
like valgrind it may look like a read of an uninitialized memory
location, but because the location is aligned and the values loaded from
the uninitialized memory is ignored, everything will work fine.
That said, I could not recreate the problem with your test case. I only
see 4-byte loads.
Ian
next prev parent reply other threads:[~2011-03-27 4:28 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-26 20:28 Nathan Boley
2011-03-27 7:38 ` Ian Lance Taylor [this message]
2011-03-28 11:06 ` Paolo Bonzini
2011-03-28 11:28 ` Richard Guenther
2011-03-28 11:47 ` Paolo Bonzini
2011-03-28 12:14 ` Richard Guenther
2011-03-28 13:37 ` Michael Matz
2011-03-28 13:54 ` Paolo Bonzini
2011-03-28 14:37 ` Richard Guenther
2011-03-29 16:03 ` Nathan Boley
-- strict thread matches above, loose matches on Subject: below --
2003-01-31 0:33 possible bug Andrew Morton
2003-01-31 0:36 ` Jan Hubicka
2003-01-31 0:56 ` Andrew Morton
2003-01-31 8:08 ` Alexandre Oliva
2003-01-31 10:48 ` Fergus Henderson
1999-07-25 17:52 Manush Dodunekov
1999-07-26 10:57 ` Alexandre Oliva
1999-07-27 3:27 ` Manush Dodunekov
1999-07-27 3:37 ` Alexandre Oliva
1999-07-31 23:33 ` Alexandre Oliva
1999-07-31 23:33 ` Manush Dodunekov
1999-07-31 23:33 ` Alexandre Oliva
1999-07-31 23:33 ` Manush Dodunekov
1997-12-12 15:46 Possible Bug Mike Sullivan
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