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To: Gabriel Dos Reis <gdr@integrable-solutions.net>
Cc: Jason Merrill <jason@redhat.com>, Jamie Lokier <jamie@shareable.org>,
        Andrew Haley <aph@redhat.com>, gcc@gcc.gnu.org
Subject: Re: On alignment
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From: Tom Tromey <tromey@redhat.com>
Reply-To: tromey@redhat.com
X-Attribution:  Tom
X-Zippy:  Where do your SOCKS go when you lose them in th' WASHER?
Date: Wed, 23 Apr 2003 20:23:00 -0000
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>>>>> "Gabriel" == Gabriel Dos Reis <gdr@integrable-solutions.net> writes:

Gabriel> #define FIELD_ALIGNOF(TYPE) __alignof (((struct { TYPE t; } *)0)->t)

Gabriel>     j.C: In function `int main()':
Gabriel>     j.C:7: error: types may not be defined in casts

I got that too, but I worked around it like so:

template<typename T>
struct aligner
{
  T field;
};

#define ALIGNOF(TYPE) (__alignof__ (((aligner<TYPE> *) 0)->field))


Gabriel> I think the template-based solution I posted in another
Gabriel> message solves the problem...

In that message you said that you got "8" as the answer for a double
field on x86.  That's not the answer I'm looking for :-(.  On x86, a
double field has alignment 4, while a non-field double has alignment
8.  In the libgcj context, we're only ever laying out structures, so
we need to get "4" as the answer.  The above does do that.

Tom