Re: [Boost-bugs] [Boost C++ Libraries] #13639: monotonic_buffer_resource current_buffer() possibly broken and documentation wrong (was: Documentation of monotonic_buffer_resource looks wrong)

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #13639: monotonic_buffer_resource current_buffer() possibly broken and documentation wrong (was: Documentation of monotonic_buffer_resource looks wrong)
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2018-07-21 15:19:18

#13639: monotonic_buffer_resource current_buffer() possibly broken and
documentation wrong
-------------------------------+---------------------------
  Reporter:  Markus Dreseler   |      Owner:  Ion Gaztañaga
      Type:  Bugs              |     Status:  new
 Milestone:  To Be Determined  |  Component:  container
   Version:  Boost 1.67.0      |   Severity:  Problem
Resolution:                    |   Keywords:
-------------------------------+---------------------------
Changes (by Markus Dreseler):

 * severity:  Cosmetic => Problem

Comment:

 Looking at this again, it looks like current_buffer itself is also broken.
 Instead of returning a pointer to the start of the current buffer, it
 returns a pointer to where the next allocation should go:

 {{{
 // clang++ -std=c++1z -lboost_container mbr.cpp

 #include <boost/container/pmr/monotonic_buffer_resource.hpp>
 #include <boost/container/pmr/polymorphic_allocator.hpp>
 #include <iostream>

 int main() {
         auto buffer =
 boost::container::pmr::monotonic_buffer_resource(size_t{100});
         auto allocator =
 boost::container::pmr::polymorphic_allocator<char>{&buffer};
         allocator.allocate(1);
         auto start_ptr = buffer.current_buffer();
         allocator.allocate(50);
         auto end_ptr = buffer.current_buffer();

         std::cout << (reinterpret_cast<uintptr_t>(end_ptr) -
 reinterpret_cast<uintptr_t>(start_ptr)) << std::endl;
         // prints 50, but should be 0
 }
 }}}

 Using clang 6.0 on OSX with boost 1.67.0_1.

-- 
Ticket URL: <https://svn.boost.org/trac10/ticket/13639#comment:1>
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