[Boost-bugs] [Boost C++ Libraries] #7106: multi_array::resize switches to default-constructed allocator

Subject: [Boost-bugs] [Boost C++ Libraries] #7106: multi_array::resize switches to default-constructed allocator
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2012-07-09 14:00:57

#7106: multi_array::resize switches to default-constructed allocator
-------------------------------------+--------------------------------------
 Reporter:  bmerry@…                 |       Owner:  garcia     
     Type:  Bugs                     |      Status:  new        
Milestone:  To Be Determined         |   Component:  multi_array
  Version:  Boost Development Trunk  |    Severity:  Problem    
 Keywords:  allocator                |  
-------------------------------------+--------------------------------------
 I've run into this with 1.46 but eyeballing the code on trunk it doesn't
 seem to have changed.

 The implementation of `resize` starts like this:
 {{{
     // build a multi_array with the specs given
     multi_array new_array(ranges,this->storage_order());
 }}}
 However, no allocator is passed to this constructor. If `*this` has a non-
 default allocator, then it will not get used to allocate the resized
 storage, and furthermore, the default allocator in new_array will get
 swapped in to `*this`, wiping out the custom allocator.

 This can be fixed by changing this line to
 {{{
     multi_array new_array(ranges,this->storage_order(),allocator_);
 }}}

 so that the new array uses the same allocator as the current one.

 I'll attach a test case that demonstrates the issue by using an allocator
 class where instances are named and report the allocations they make (I'm
 using a more complex version of this to track memory usage, which is where
 I hit the bug). It currently reports
 {{{
 Allocated 17 bytes [name = vector]
 Allocated 0 bytes [name = multi_array]
 Allocated 15 bytes [name = default]
 }}}
 but with the fix applied it reports
 {{{
 Allocated 17 bytes [name = vector]
 Allocated 0 bytes [name = multi_array]
 Allocated 15 bytes [name = multi_array]
 }}}

 It is the final line where the resize is taking place.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/7106>
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