Date:	Thu, 25 Mar 1999 14:22:06 +0100
From:	Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de>
Message-Id:	<199903251322.OAA16292@acp3bf.physik.rwth-aachen.de>
To:	djgpp AT delorie DOT com
Subject:	Re: Preprocessor hates sizeof
Newsgroups:	comp.os.msdos.djgpp
Organization:	RWTH Aachen, III. physikalisches Institut B
X-Newsreader:	TIN [version 1.2 PL2]
Reply-To:	djgpp AT delorie DOT com

In article <Pine DOT GSO DOT 3 DOT 96 DOT 990325095712 DOT 28097B-100000 AT delta DOT ds2 DOT pg DOT gda DOT pl> you wrote:
> > >#if sizeof(long int)==sizeof(int)

> I need something like that in a portable program to check if the structure
> is not larger than a single allocation unit. The exact code is this:

> #if (sizeof(Box) > BOXGRAIN)
> #error Size of Box header cannot exceed size of grain.
> #endif

> Now I know that GCC does and will not support this, so how can I replace
> it?

Strictly spoken, you can't. Actually, you shouldn't even _want_ to do that.

If your program really is meant to be 'portable', it shouldn't rely on
anything as shaky as this. For a portable program, you'ld have to get
rid of all fixed-size limits like that 'BOXGRAIN', above, e.g. by
making a size-independant data structure by use of unions.

Or you might isolate all such inescapable unportabilities in a small,
separate portion of the source code, which will have to be ported from
one architecture to the other, *manually*.

--
Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
Even if all the snow were burnt, ashes would remain.

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