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From: Peter Dufault <dufault@hda.hda.com>
Message-Id: <200103041912.f24JCYq46536@hda.hda.com>
Subject: Posix feature tests update
To: current@freebsd.org
Date: Sun, 4 Mar 2001 14:11:58 -0500 (EST)
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Critique, please.

I'm building a large body of code with the following cc options:

> -D_POSIX_VERSION=199506L -D_POSIX_SOURCE -D_POSIX_C_SOURCE=199506L

and one of my own:  > -D_P1003_1G_VISIBLE

together with locally hacked up headers.

Here's how I'm hacking.  This could go into current if no one
objects.

1. In "sys/_posix.h" the test macro _BSD_TRADITIONAL is defined if
neither _POSIX_SOURCE nor _POSIX_C_SOURCE are defined.  In most
system headers, those items currently bracketed by

> #ifndef _POSIX_SOURCE

instead are bracketed by

> #ifdef _BSD_TRADITIONAL

2. What I'd previously put in sys/_posix.h as

> #define _P1003_1B_VISIBLE

is replaced by

> #define _P1003_1_199309

The notion is that prior to a draft being finalized it is fine to
select it with _P1003_1B_VISIBLE (or _P1003_1G_VISIBLE) since you
don't know the final _POSIX_VERSION and it should be viewed with
suspicion, but once it is finalized it should be replaced by the
_POSIX_VERSION numeric id.

3. I'd get rid of the verbose and unclear:

#define _P1003_1B_VISIBLE_HISTORICALLY

and replace it with the inline (that is, repeated in the headers)
test

> #if defined(_BSD_TRADITIONAL) || defined(_P1003_1_199309)

4. Everything added in the 1995 P1003.1 is bracketed by

> #ifdef _P1003_1_199506

or

> #if defined(_BSD_TRADITIONAL) || defined(_P1003_1_199506)

as appropriate, i.e. if brand new it gets the first test, if
pre-existing it gets the second.

5. Those items from the draft Posix 1003.1-G are bracketed by
_P1003_1G_VISIBLE optionally or'd with _BSD_TRADITIONAL, as needed.

--

It is useful to specify the Posix version, but right now the
lack of networking support makes it only marginally useful.

Peter

--
Peter Dufault (dufault@hda.com)   Realtime development, Machine control,
HD Associates, Inc.               Fail-Safe systems, Agency approval

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