Message-ID: <3702984D.34D44A88@scordon.com.br>
Date: Wed, 31 Mar 1999 18:49:02 -0300
From: producao <producao AT scordon DOT com DOT br>
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To: djgpp AT delorie DOT com
Subject: Re: How does DJGPP store its structs?
References: <199903310411 DOT XAA09206 AT delorie DOT com>
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Reply-To: djgpp AT delorie DOT com



George Foot wrote:

> On 31 Mar 99 at 4:00, Andrew Davidson wrote:
>
> > I've tested the structs and all stuff done from within C code works fine.
> > Is this 12 byte thing the result of the way I'm trying to use the scratch
> > struct (from within another struct) or just a limitation of djgpp? I have a
> > feeling that djgpp might be trying to optimise the struct  so is there any
> > way I can dissable this optimisation while keeping all the other forms of
> > optimisation available?
>
> gcc is padding the structs with dead space to align the fields
> for speed.  To tell it not to do this, put `__attribute__
> ((__packed__))' after the struct definition, or if the code is
> C++, put it after every field in the struct.  In both cases, it
> goes before the semicolon.
>
> C example:
>
>     struct foo {
>         char a;
>         int b;
>     } __attribute__ ((__packed__));
>
> C++ example:
>
>     struct bar {
>         char a __attribute__ ((__packed__));
>         int b __attribute__ ((__packed__));
>     };
>

    Or use -fpack-struct.

> The C++ way works in C too, but it's more hassle.
>
> --
> George