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From: Terry Lambert <terry@lambert.org>
Newsgroups: comp.unix.bsd.netbsd.misc
Subject: Re: What is __P() for?
Date: 1 Dec 1995 01:03:58 GMT
Organization: Utah Valley State College, Orem, Utah
Lines: 48
Message-ID: <49lk9u$knc@park.uvsc.edu>
References: <498eac$2gm@taco.cc.ncsu.edu> <DIs1rJ.GMz@deshaw.com>
NNTP-Posting-Host: hecate.artisoft.com
christos@deshaw.com (Christos Zoulas) wrote:
] In article <498eac$2gm@taco.cc.ncsu.edu> kpneal@eos.ncsu.edu (Kevin P. Neal) writes:
] >What is the purpose of this:
] >
] >int __P(functname(int arg));
] >
] >(Did I do that right?) What is the point? Doesn't it just
] >get converted by the preprocessor into (funct...) anyway?
] >
] >I think this has something to do with ANSI C, but what is the
] >story behind it?
]
] I'll answer this one, but please in the future poke a bit around before
] you ask... You should look for it's #define definition in /usr/include:
[ ... not quite an answer 8-) ... ]
It's so you can declare extern functions, usually in header files,
and have them be prototypes for ANSI C compilers (which define
__STDC__) and K&R externs for non-ANSI C compilers.
Some programs, even on GCC using systems, require you to use
traditional compilation instead of ANSI for them to work right.
So if __STDC__ is defined:
int foo __P((int arg1, char * arg2));
Becomes:
int foo (int arg1, char *arg2);
And without __STDC__ defined, becomes:
int foo ();
So the same header files work on both K&R and ANSI compilers.
Makes sense, really, since you might port to an old system
and not want to have to drag all of GCC with you.
Terry Lambert
terry@cs.weber.edu
---
Any opinions in this posting are my own and not those of my present
or previous employers.