Path: utzoo!attcan!utgpu!utstat!jarvis.csri.toronto.edu!rutgers!usc!cs.utexas.edu!uunet!munnari.oz.au!bruce!cechew
From: cechew@bruce.OZ (Earl Chew)
Newsgroups: comp.os.minix
Subject: Re: New wait.h
Message-ID: <1684@bruce.OZ>
Date: 10 Nov 89 13:33:25 GMT
References: <4463@ast.cs.vu.nl>
Organization: Monash Uni. Computer Science, Australia
Lines: 26

From article <4463@ast.cs.vu.nl>, by ast@cs.vu.nl (Andy Tanenbaum):
>   Does this one look better?  I think I have the case of both bytes 0

Umm... well, everything except for:

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

Would be safer to protect __v in parentheses:
#define _HIGH(__v)              ( ((__v) >> 8) & 0377)

> #define WIFSIGNALED(__s)	(_HIGH(__s) == 0 && __s != 0) /* signaled */

You can get by without evaluating __s _twice_ (macros with side-effects and all
that) (and again, you didn't protect (__s) != 0 in parentheses):

#define WIFSIGNALED(__s)	((unsigned int) ((__s) - 1 & 0xffff) < 0xff)

__s is evaluated only once. I don't know if Posix allows these macros to be
`unsafe' (ie evaluate arguments more than once). In any event, it's safer this
way (probably more efficient also --- only one test required instead of two).

Earl
-- 
Earl Chew, Dept of Computer Science, Monash University, Australia 3168
ARPA: cechew%bruce.cs.monash.oz.au@uunet.uu.net  ACS : cechew@bruce.oz
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