Re: [boost] [forward_declare] Interest Inquiry toward Faster Compile Times

Subject: Re: [boost] [forward_declare] Interest Inquiry toward Faster Compile Times
From: Larry Evans (cppljevans_at_[hidden])
Date: 2012-08-01 23:37:24

On 08/01/12 20:18, Daniel Larimer wrote:
> Julien,
> An extra 'byte' was just left over from me testing.  It works with 8
> bytes (2 ints) and it asserts on 7 bytes.  I was trying to find a
> way to 'warn' if you reserved too much.  It looks like
> BOOST_STATIC_WARN() has been removed.
>
> I thought about alignment issues (I am no expert here), but my
> understanding is that structs/classes are always 'aligned' in the
> same manner regardless of what is stored.  Therefore, if my fwd<>
> class only has one data member (an array) it should be aligned
> appropriately for any type.
>

I'm pretty sure that you're array, char fwd<T,S>::_store[S], has an
alignment of 1; thus, If T is double, it would not be aligned properly.
You need to use an aligned buffer, which boost provides and is also in
the standard someplace.  boost::variant uses the boost aligned buffer
for its storage buffer.

HTH.

-regards,
Larry