Re: [boost] type_with_alignment size fix

From: Joel de Guzman (djowel_at_[hidden])
Date: 2003-04-16 18:22:07

Douglas Gregor wrote:
> type_with_alignment was generating huge types on most platforms,
> because it would take every type with the right alignment into a
> union. On x86, for instance, double and int have the same alignment
> (4), so sizeof(type_with_alignment<4>::type)=12! type_with_alignment
> now takes the first type whose alignment matches, and the types are
> roughly ordered by size, so the resulting type size should be smaller.

Doug, this is GOOD! You da man!

I've just switched Spirit's match class to use boost::optional. Before
your patch, I get:

    sizeof(match<int>) == 20
    sizeof(match<double>) == 32

Now, I have:

    sizeof(match<int>) == 12
    sizeof(match<double>) == 24

Still 4 to 8 bytes more than the pre-optional code:

    sizeof(match<int>) == 8
    sizeof(match<double>) == 16

But it will do... Heh... can I ask for more :-)? 

-- 
Joel de Guzman
joel at boost-consulting.com
http://www.boost-consulting.com
http://spirit.sf.net