[Boost-bugs] [Boost C++ Libraries] #11609: circular_buffer erroneously invalidates reverse_iterator at pop_back in debug mode

Subject: [Boost-bugs] [Boost C++ Libraries] #11609: circular_buffer erroneously invalidates reverse_iterator at pop_back in debug mode
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-09-01 15:50:34

#11609: circular_buffer erroneously invalidates reverse_iterator at pop_back in
debug mode
----------------------------------+------------------------------
 Reporter:  christian.stimming@…  |       Type:  Bugs
   Status:  new                   |  Milestone:  To Be Determined
Component:  None                  |    Version:  Boost 1.57.0
 Severity:  Problem               |   Keywords:
----------------------------------+------------------------------
 The circular_buffer container offers reverse iterators. Using one so that
 it points to the second-to-last element would in theory allow to
 pop_back() the last element without causing problems with that iterator.
 However, apparently pop_back() invalidates those reverse iterators even
 though they wouldn't cause problems, as if the debug_iterator_registry in
 boost/circular_buffer/debug.hpp is working correctly only for forward
 iterators but not for backward iterators.

 Example code that works fine without debug mode, but will run into a
 failed assertion in debug mode:

 #define BOOST_CB_ENABLE_DEBUG
 #include <boost/circular_buffer.hpp>
 #include <iostream>
 int main(int /*argc*/, char** /*argv*/) {
         typedef boost::circular_buffer<int> CircBuffer;
         CircBuffer testBuffer(2);
         testBuffer.push_back(4);
         testBuffer.push_back(8);

         CircBuffer::const_reverse_iterator bufIter = testBuffer.rbegin();
         std::cout << "element at rbegin=" << *bufIter << std::endl; //
 prints "=8" correctly
         ++bufIter;
         std::cout << "element after ++=" << *bufIter << std::endl; //
 prints "=4" correctly
         testBuffer.pop_back();
         std::cout << "elem=" << *bufIter << std::endl; // ERROR: Causes
 "Assertion `is_valid(m_buff)' failed."
 }

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11609>
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