MESSAGE
| DATE | 2011-06-11 |
| FROM | Ruben Safir
|
| SUBJECT | Subject: [NYLXS - HANGOUT] (fwd) Re: Using sizeof in the preprocessor
|
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From: Huibert Bol
Newsgroups: comp.lang.c++
Subject: Re: Using sizeof in the preprocessor
Date: Sat, 21 May 2011 16:08:58 +0200
Organization: A noiseless patient Spider
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Xref: panix comp.lang.c++:1085097
Johannes Schaub wrote:
> I have this code in my pet project
>
> #if sizeof -1 > 4
> #error "This doesn't work on 64bit"
> #endif
>
> My friend was telling me that this shouldn't work because "sizeof is not
> evaluated in the preprocessor". Yet the compiler accepts it and my program
> works.
Identifiers in #if expressions are evaluated as zero, so the expression
is equivalent to
#if 0 -1 > 4
which is never true.
--
Huibert
"Okay... really not something I needed to see." --Raven
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