Details
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Bug
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Status: Resolved
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Major
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Resolution: Fixed
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4.1.2, 4.1.3
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None
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all
Description
-------- Original Message --------
Subject: Re: Re: test for lib.alg.partitions
Date: Fri, 27 Jan 2006 19:01:52 +0300
From: Anton Pevtsov <antonp@moscow.vdiweb.com>
Reply-To: stdcxx-dev@incubator.apache.org
To: stdcxx-dev@incubator.apache.org
...
Martin Sebor wrote:
> It's certainly possible that there is a bug in the algorithm, but I
> would be more inclined to suspect the test before the algorithm just
> because you just made making non-trivial changes to it.
[...]
> A simple test case would be helpful.
The old test version didn't exercise all possible cases. I updated the
test according to your notes and got the same results. So I still
suspect the bug in the algorithm.
The attached file stable_partition_test.cpp illustrates the problem:
the algorithm fails when the predicate returns true for any element.
I debug the algorithm and found the following code in algorithm.cc, line
760:
...
_Dist __fill = 0;
const _BidirIter __res =
_stable_partition_adaptive (_first, __last, __pred, __dist,
__pair.first, __pair.second,
__fill, (_TypeT*)0);
for (TypeT *ptr = __pair.first + __fill; !(_pair.first ==
--__ptr); )
(*__ptr).~_TypeT ();
...
If the __fill remains equal to 0 after the __stable_partition_adaptive
call the "for" will never end and will try to call destructors of
non-existing elements moving from the left bound of the given sequence
to left. Also if __fill is equal to 1 no destructors will be called, but
one should be, shouldn't it?
May be, something like this
...
for (TypeT *ptr = __pair.first + __fill; !(_pair.first ==
__ptr--); )
(*__ptr).~_TypeT ();
...
will fix the issue?
And I have another question: what will happen with the temporary buffer
in stable_partition if the X copy ctor throws an exception? It looks
like the buffer will leak.
With best wishes,
Anton Pevtsov