Re: [Boost-bugs] [Boost C++ Libraries] #11830: small_vector move is broken

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #11830: small_vector move is broken
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-12-06 08:05:25

#11830: small_vector move is broken
------------------------------------------+-------------------------------
  Reporter:  mrmiller <michael_miller@…>  |      Owner:  igaztanaga
      Type:  Bugs                         |     Status:  new
 Milestone:  To Be Determined             |  Component:  container
   Version:  Boost 1.59.0                 |   Severity:  Showstopper
Resolution:                               |   Keywords:  small_vector move
------------------------------------------+-------------------------------

Comment (by mrmiller <michael_miller@…>):

 I located a couple different problem spots that seem to fix the issue in
 the cases I've tested. On my end, I refactored steal_resources and broke
 out the resetting into clear_resources:


 {{{
    void steal_resources(vector_alloc_holder &x) BOOST_NOEXCEPT_OR_NOTHROW
    {
       this->m_start     = x.m_start;
       this->m_size      = x.m_size;
       this->m_capacity  = x.m_capacity;
       x.clear_resources();
    }

    void clear_resources() BOOST_NOEXCEPT_OR_NOTHROW
    {
       this->m_start = pointer();
       this->m_size = this->m_capacity = 0;
    }
 }}}

 Every time we use a move_iterator to do the copy because the allocator
 isn't propagable, we need to clear out the previous allocator. That means
 simply adding x.clear_resources() after the call to assign in
 vector::priv_move_assign and small_vector::move_construct_impl.

 Lastly, small_vector's move constructor seems rather suspect to me:
 {{{
    small_vector(BOOST_RV_REF(small_vector) other)
       : base_type(initial_capacity_t(), internal_capacity(),
 ::boost::move(other.get_stored_allocator()))
    {  this->move_construct_impl(other, other.get_stored_allocator());   }
 }}}

 That call to other.get_stored_allocator() looks really suspicious after
 we've moved the allocator in the initializer...

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11830#comment:1>
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