Re: [boost] Silent change in boost 1.36 alignment_of<> template with gcc 4.3

Subject: Re: [boost] Silent change in boost 1.36 alignment_of<> template with gcc 4.3
From: Jon Biggar (jon_at_[hidden])
Date: 2008-11-09 01:42:11

David Abrahams wrote:
> on Sat Nov 08 2008, Mathias Gaunard <mathias.gaunard-AT-ens-lyon.org> wrote:
> 
>> Jon Biggar wrote:
>>
>>> Unfortunately, this broke some code I had written that did structure introspection,
>>> because gcc's __alignof__() returns 8 for double on the x86 architecture, but
>>> actually only aligns doubles on 4 byte boundaries inside structures.
>> I personally never understood why gcc's alignof returns that.
>> It doesn't even make sense, since the size of double is not a multiple of 8, so
>> multiple doubles right after each other can't possibly be 8-byte aligned.
> 
> We could easily either specialize our way around it or limit the result
> of alignment_of<T> to sizeof(T).  The latter seems like a smart thing to
> do anyway.
> 
> Thoughts?

I'm becoming convinced that we just shouldn't us the __alignof__() 
builtin from gcc because it lies.

-- 
Jon Biggar
jon_at_[hidden]
jon_at_[hidden]
jonbiggar_at_[hidden]