MESSAGE
| DATE | 2011-06-11 |
| FROM | Ruben Safir
|
| SUBJECT | Subject: [NYLXS - HANGOUT] (fwd) Re: Using sizeof in the preprocessor
|
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From: Johannes Schaub
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Date: Sat, 21 May 2011 21:54:20 +0200
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Subject: Re: Using sizeof in the preprocessor
Newsgroups: comp.lang.c++
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Xref: panix comp.lang.c++:1085128
Juha Nieminen wrote:
> Huibert Bol wrote:
>> Identifiers in #if expressions are evaluated as zero
>
> It seems that at least with gcc "#if true" and "#if false" work as one
> would expect. Is this standard?
There are explicit exceptions for true and false. The spec says
After all replacements due to macro expansion and the defined unary operator
have been performed, all remaining identiï¬ers and keywords, except for true
and false, are replaced with the pp-number 0, and then each preprocessing
token is converted into a token. The resulting tokens comprise the
controlling constant expression which is evaluated according to the rules of
5.19 ...
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