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From: ast@cs.vu.nl (Andy Tanenbaum)
Newsgroups: comp.unix.questions
Subject: Some questions about POSIX headers
Message-ID: <4508@ast.cs.vu.nl>
Date: 10 Nov 89 23:45:34 GMT
Sender: ast@cs.vu.nl
Reply-To: ast@cs.vu.nl (Andy Tanenbaum)
Organization: VU Informatica, Amsterdam
Lines: 22

I have several questions about POSIX P1003.1.  Consider the following
excerpt from <sys/wait.h>:

#define _LOW(__v)               ( (__v) & 0377)
#define _HIGH(__v)              ( ((__v) >> 8) & 0377)

#define WIFEXITED(__s)		(_LOW(__s) == 0)	      /* normal exit */
#define WEXITSTATUS(__s)	(_HIGH(__s))	 	      /* exit status */
#define WTERMSIG(__s)		(_LOW(__s) & 0177)	      /* sig value */
#define WIFSIGNALED(__s)	(_HIGH(__s) == 0 && __s != 0) /* signaled */

1. Is it legal to have _LOW and _HIGH here (name space pollution rules)?
2. Are the parameters __s and __v required to begin with __ (again, name
   space pollution rules)?
3. WIFSIGNALED evaluates __s twice.  Is this legal?  In an ANSI C header
   it is specifically forbidden.  What about POSIX?
4. Is the extra set of parenthesis around __v in _HIGH() really required?
5. What is the best newsgroup for asking this sort of question?

Thanks.

Andy Tanenbaum (ast@cs.vu.nl)