[Boost-bugs] [Boost C++ Libraries] #3731: array without padding

Subject: [Boost-bugs] [Boost C++ Libraries] #3731: array without padding
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2009-12-08 14:13:41

#3731: array without padding
------------------------------+---------------------------------------------
 Reporter:  anonymous         |       Owner:         
     Type:  Feature Requests  |      Status:  new    
Milestone:  Boost 1.42.0      |   Component:  None   
  Version:  Boost 1.41.0      |    Severity:  Problem
 Keywords:                    |  
------------------------------+---------------------------------------------
 Sometimes you have a struct with array in it:

 {{{
 #!cpp
 #pragma pack(push, 1)
 struct X
 {
  int i[10];
 };
 #pragma pack(pop)
 }}}

 And you want to use boost::array :

 {{{
 #!cpp
 #pragma pack(push, 1)
 struct X
 {
  boost::array<int, 10> i;
 };
 #pragma pack(pop)
 }}}

 The problem that boost::array is not surrounded with #pragma pack.

 It would be nice to add a new class boost::array_no_padding with #pragma
 pack surrounded and with static assert for size checking.

 {{{
 #!cpp
 #if !BOOST_SUPPORTS_PRAGMA_PACK &&
     !BOOST_SUPPORTS_ALIGNMENT_PREFIX &&
     !BOOST_SUPPORTS_ALIGNMENT_SUFFIX
 #error Cannot specify alighnemnt
 #endif

 namespace boost {


 #if BOOST_SUPPORTS_PRAGMA_PACK
 #define ALIGNMENT_SET
 #pramga pack(push, 1)
 #endif

 template<class T, std::size_t N>
 class
    #if !defined(ALIGNMENT) && BOOST_SUPPORTS_ALIGNMENT_PREFIX
    // Could be __declspec(align(1))
    BOOST_ALIGNMENT_PREFIX
    #define ALIGNMENT_SET
    #endif
    array_no_padding

    #if !defined(ALIGNMENT) && BOOST_SUPPORTS_ALIGNMENT_SUFFIX
    // Could be __attribute__((aligned(1)))
    BOOST_ALIGNMENT_SUFFIX
    #define ALIGNMENT_SET
    #endif

    // Can derive from boost::array or copy-paste all the content
     :  boost::array
    {
       // ...


      // Check class size with the array size
      BOOST_STATIC_ASSERT( sizeof(*this) == sizeof(T[N]) );
    }


 #if BOOST_SUPPORTS_PRAGMA_PACK
 #pragma pack(pop)
 #endif

 }}}


 Thanx !

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/3731>
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