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Re: Issue 4212: fix out-of-bounds index in division_maior() (issue 18942
From: |
dak |
Subject: |
Re: Issue 4212: fix out-of-bounds index in division_maior() (issue 189420043 by address@hidden) |
Date: |
Fri, 02 Jan 2015 14:36:34 +0000 |
On 2015/01/02 14:16:54, Dan Eble wrote:
On 2015/01/02 08:56:03, dak wrote:
> In particular, the compiler is allowed to make
> line_pos.begin () < whatever the same as line_pos.begin () !=
whatever.
* std::vector elements must be contiguous after C++03
(http://en.cppreference.com/w/cpp/container/vector)
* it[n] is convertible to a reference and is equivalent to *(i + n)
(http://en.cppreference.com/w/cpp/concept/RandomAccessIterator)
Therefore there should be no problem with "x.begin() < it" as long as
the vector
is not empty and "it != x.end()". I'm not sure if anything constrains
the
implementation of x.end() to refer to the place this code assumes it
does, so
that might still be a problem.
Still, I'm going to resist doing anything other than fixing the
immediate
problem. I do not want to risk spending a bunch of time debugging if
I rewrite
it wrong.
The case I was worried about was (line_pos.begin () < it - 1)
This expression is undefined if it == line_pos.begin () since
line_pos.begin () - 1 is undefined, being before the start of the array.
https://codereview.appspot.com/189420043/
- Issue 4212: fix out-of-bounds index in division_maior() (issue 189420043 by address@hidden), nine . fierce . ballads, 2015/01/01
- Re: Issue 4212: fix out-of-bounds index in division_maior() (issue 189420043 by address@hidden), benko . pal, 2015/01/01
- Re: Issue 4212: fix out-of-bounds index in division_maior() (issue 189420043 by address@hidden), nine . fierce . ballads, 2015/01/01
- Re: Issue 4212: fix out-of-bounds index in division_maior() (issue 189420043 by address@hidden), benko . pal, 2015/01/02
- Re: Issue 4212: fix out-of-bounds index in division_maior() (issue 189420043 by address@hidden), dak, 2015/01/02
- Re: Issue 4212: fix out-of-bounds index in division_maior() (issue 189420043 by address@hidden), benko . pal, 2015/01/02
- Re: Issue 4212: fix out-of-bounds index in division_maior() (issue 189420043 by address@hidden), nine . fierce . ballads, 2015/01/02
- Re: Issue 4212: fix out-of-bounds index in division_maior() (issue 189420043 by address@hidden),
dak <=
- Re: Issue 4212: fix out-of-bounds index in division_maior() (issue 189420043 by address@hidden), nine . fierce . ballads, 2015/01/02