[Boost-bugs] [Boost C++ Libraries] #11312: smart_ptr::detail::as_allocator::allocate() adds alignment padding when it's not needed

Subject: [Boost-bugs] [Boost C++ Libraries] #11312: smart_ptr::detail::as_allocator::allocate() adds alignment padding when it's not needed
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-05-15 22:50:38

#11312: smart_ptr::detail::as_allocator::allocate() adds alignment padding when
it's not needed
---------------------------------+-----------------------
 Reporter:  David Aue <david@…>  |      Owner:  pdimov
     Type:  Bugs                 |     Status:  new
Milestone:  To Be Determined     |  Component:  smart_ptr
  Version:  Boost 1.57.0         |   Severity:  Problem
 Keywords:                       |
---------------------------------+-----------------------
 smart_ptr::detail::as_allocator::allocate()
 {
   enum {
      M = boost::alignment_of<type>::value
   };
   std::size_t n1 = count * sizeof(value_type);
   std::size_t n2 = data.size * sizeof(type);
   std::size_t n3 = n2 + M;
   CA ca(allocator());
   void* p1 = ca.allocate(n1 + n3);


 Allocation is for two items of size n1 and n2. Alignment size is added to
 n2 to create n3 to there is room to align n2 properly.

 if n1 % M == 0 then alignment is already fine and the extra M bytes is
 wasted.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11312>
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