From:	Erik Max Francis <max AT alcyone DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Question about #pragma
Date:	Tue, 12 Aug 1997 09:03:37 -0700
Organization:	Alcyone Systems
Lines:	35
Message-ID:	<33F08959.6BFCE741@alcyone.com>
References:	<ww01-BHLJZN2260 AT netaddress DOT usa DOT net>
NNTP-Posting-Host:	newton.alcyone.com
Mime-Version:	1.0
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Guan Foo Wah wrote:

> I have seem many source code with the word #pragma. I do not know what
> this means. My C book (Teach Yourself C in 21 Days) did not give me any
> info about this. The only thing I know is it is a preprocessor command.
> 
> Can anyone care to explain to me what is #pragma. Is it ANSI
> compatible ??

#pragma is ANSI, but it is one of those strange standard features that is
included for the sole purposes of allowing implementation-defined
behavior.  From ANSI C, 6.8.6:

    A preprocessing directive of the form

        # pragma pp-tokens_opt new-line

    causes the implmentation to behave in an implementation-defined 
    manner.  Any pragma that is not recognized by the implementation is
    ignored.

The #pragmas that are used from one compiler to another change
drastically, and there's no way to know whether one #pragma will work in
another compiler (because usually it won't).  And, since #pragmas that
aren't recognized are completely ignored, you need to check what the
#pragma did in the last compiler you were using and see if it's important
enough that you'll need to take steps to ensure that you do it with DJGPP.

-- 
       Erik Max Francis, &tSftDotIotE / email / mailto:max AT alcyone DOT com
                     Alcyone Systems /   web / http://www.alcyone.com/max/
San Jose, California, United States /  icbm / 37 20 07 N  121 53 38 W
                                   \
   "Love is not love which alters / when it alteration finds."
                                 / William Shakespeare, _Sonnets_, 116

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