From owner-freebsd-hackers  Fri Jun  1 18:26:10 2001
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Date: Fri, 01 Jun 2001 20:25:39 -0500
To: Farooq Mela <fmela0@sm.socccd.cc.ca.us>,
	freebsd-hackers@FreeBSD.ORG
From: "G. Adam Stanislav" <adam@whizkidtech.net>
Subject: Re: _ANSI_SOURCE vs. _ANSI_C_SOURCE
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At 20:00 31-05-2001 -0700, Farooq Mela wrote:
>I am wondering why some operating systems use the macro _ANSI_SOURCE
>while others (ie Linux) use _ANSI_C_SOURCE to indicate that the source
>compiled is ANSI-compliant (and similarly with _POSIX_SOURCE and
>_POSIX_C_SOURCE).

My copy of POSIX Programmer's Guide says, in Chapter 9:

"The chances of stumbling over a reserved C or POSIX name can be
minimized by following a few simple rules:

1. Start each source file with the line:

	#define _POSIX_SOURCE 1

   All symbols not defined by Standard C or the POSIX standard
   will be hidden, except those with leading underscores.

2. Following the definition of _POSIX_SOURCE, place the #include
   statements for any standard header files."

There's more, but that should answer one of your questions. :)
I don't know about the _POSIX_C_SOURCE though. I suppose you
could always define:

	#define _POSIX_SOURCE 1
	#define _POSIX_C_SOURCE _POSIX_SOURCE

Cheers,
Adam

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