[boost] [type traits] type_with_alignment/alignment_of on GCC

From: Douglas Gregor (gregod_at_[hidden])
Date: 2003-09-02 18:15:23

I see that there is some special code in type_with_alignment for Borland C++, 
partly because it is broken and partly because we can do a better job using 
compiler-specific features.

Why not do the same for other compilers? For instance, on GCC:

template<typename T>
  struct alignment_of
  { BOOST_STATIC_CONSTANT(std::size_t, value = __alignof__(T)); };

and

template<std::size_t Align>
  struct type_with_alignment
  {  struct __attribute__((__aligned__)) type {}; };

template<> struct type_with_alignment<1>
  {  struct __attribute__((__aligned__(1))) type {}; };
template<> struct type_with_alignment<2>
  {  struct __attribute__((__aligned__(2))) type {}; };
template<> struct type_with_alignment<4>
  {  struct __attribute__((__aligned__(4))) type {}; };
template<> struct type_with_alignment<8>
  {  struct __attribute__((__aligned__(8))) type {}; };
template<> struct type_with_alignment<16>
  {  struct __attribute__((__aligned__(16))) type {}; };
template<> struct type_with_alignment<32>
  {  struct __attribute__((__aligned__(32))) type {}; };

It'll reduce the compile time for this platform and give us exact answers. The 
only concern I can see is that we might miss some important alignment number 
(say, 17); we could avert this problem by creating everything from 1 to 32, 
and it would still be much simpler than the current code.

Would anyone object to me making this change for GCC?

        Doug