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From: "leis at in dot tum.de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/63233] Missing Warray-bounds warning for array within struct
Date: Thu, 11 Sep 2014 22:26:00 -0000	[thread overview]
Message-ID: <bug-63233-4-GzQJI8Qx4z@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-63233-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63233

--- Comment #5 from leis at in dot tum.de ---
Thanks. I did notice that I get warning with optimization but not without,
which is strange indeed.

However, obviously my real problem is more complicated, and I'm trying to
understand if I violate the standard. If I pick apart the offending
line (foo.a[1] = 99;):

int* p1 = foo.a;  //1
int* p2 = p1 + 1; //2
*p2 = 99;         //3

Which of these lines causes the undefined behavior? Why should pointer p2 be
invalid?

Fundamentally, what I'm really trying to do, is to have two arrays (of
different types) in a fixed-sized struct. One array grows from the front, and
one from the end. Dynamically I make sure that they do not overlap, but the
sizes of the two arrays are not known statically. Is it really violating the
standard?


  parent reply	other threads:[~2014-09-11 22:26 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-11 21:15 [Bug c/63233] New: Valid out of bounds access leads to undefined behavior leis at in dot tum.de
2014-09-11 21:29 ` [Bug c/63233] " pinskia at gcc dot gnu.org
2014-09-11 22:02 ` [Bug c/63233] Missing Warray-bounds warning for array within struct manu at gcc dot gnu.org
2014-09-11 22:14 ` pinskia at gcc dot gnu.org
2014-09-11 22:26 ` leis at in dot tum.de [this message]
2014-09-13  9:36 ` mikpelinux at gmail dot com

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