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Date:      Thu, 10 Oct 2002 14:24:34 +0300
From:      Giorgos Keramidas <keramida@ceid.upatras.gr>
To:        Terry Lambert <tlambert2@mindspring.com>
Cc:        Garrett Wollman <wollman@lcs.mit.edu>, Craig Rodrigues <rodrigc@attbi.com>, freebsd-standards@freebsd.org, freebsd-hackers@freebsd.org
Subject:   Re: Problem detecting POSIX symbolic constants
Message-ID:  <20021010112434.GS21391@hades.hell.gr>
In-Reply-To: <3DA5354F.9BB3E54B@mindspring.com>
References:  <20021009222307.A9894@attbi.com> <200210100549.g9A5nFLn060516@khavrinen.lcs.mit.edu> <3DA5354F.9BB3E54B@mindspring.com>

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On 2002-10-10 01:07, Terry Lambert <tlambert2@mindspring.com> wrote:
>
> So the test is:
>
> #ifdef _POSIX_REALTIME_SIGNALS
> #if _POSIX_REALTIME_SIGNALS > 0
>
> ...or, if you want to assume all preprocessors support "#if":
>
> #if defined(_POSIX_REALTIME_SIGNALS) && (_POSIX_REALTIME_SIGNALS > 0)
>
> I think the first is safer, in that if "#if" is not supported, it
> being an undefined preprocessor directive would be non-fatal,
> being in an uncompiled "#ifdef" block...

Well, almost.  There is one exception.  A compiler that doesn't support
#if but happens to run in an environment that has _POSIX_REALTIME_SIGNALS
defined and equal to -1.

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