[Boost-bugs] [Boost C++ Libraries] #1127: multi_array views do not handle negative strides correctly

Subject: [Boost-bugs] [Boost C++ Libraries] #1127: multi_array views do not handle negative strides correctly
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2007-07-28 20:24:26

#1127: multi_array views do not handle negative strides correctly
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 Reporter:  news_at_[hidden]  |       Owner:  garcia     
     Type:  Bugs                          |      Status:  new        
Milestone:  To Be Determined              |   Component:  multi_array
  Version:                                |    Severity:  Problem    
 Keywords:                                |  
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 Discovered in 1.33.1, but the code appears to be unchanged in 1.34.1.

 The attached test case fails.  Compiling with FUDGED_RANGE causes the test
 case to work, but it shouldn't.  The problem appears to be due to
 generate_array_view in boost/multi_array/base.hpp; it does not correctly
 handle negative strides.

 "len" is incorrectly calculated in the following code, when stride (and
 hence index_factor) is negative:
       index index_factor = current_range.stride();
       index len = (finish - start + (index_factor - 1)) / index_factor;

 I was initially unsure as to whether negative strides were supported, but
 it is clear from other code in base.hpp that stride sign is carefully
 handled, so I it should be in the view.

 Phil Richards

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Ticket URL: <http://svn.boost.org/trac/boost/ticket/1127>
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