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From: johnz@grapevine.uucp (John Zolnowsky ext. 33230)
Newsgroups: comp.os.minix
Subject: Re: POSIX
Summary: POSIX-compliant crashes
Message-ID: <34633@grapevine.uucp>
Date: 27 Oct 89 23:27:08 GMT
References: <3819@ast.cs.vu.nl> <1989Oct26.143100.4916@world.std.com> <2091@prune.bbn.com>
Sender: johnz@grapevine.EBay (John Zolnowsky ext. 33230)
Organization: Sun Microsystems, Inc. - Mtn View, CA
Lines: 33

In article <2091@prune.bbn.com>, rsalz@bbn.com (Rich Salz) writes:
> In <3842@math.cs.vu.nl> ast@cs.vu.nl (Andy Tanenbaum) writes:
> >Perhaps it wasn't a bug previously, but has to be regarded as a bug now
> >because POSIX explicitly requires a call to closedir() with a rotten
> >argument to return EBADF, not to crash, trap or do anything else. (See
> >Sec. 5.1.2.4 of P1003.1).
> 
> If closedir() is not implemented as a syscall, then the only portable
> way to handle this is to keep a list of everything you ever opendir'd,
> and a flag as to whether it's still valid or not.
> 
> Posix blew it on this one; they should have defined it to be undefined
> action.

POSIX is full of "legalese" for these cases.  The EBADF case mentioned
above, for instance, is prefaced by the conditional:
	"For each of the following conditions, *when* [emphasis added -JZ]
	the condition is detected, the closedir() function shall return
	-1 and set errno ..."

Section 2.5 Error Numbers further clarifies this in the fourth paragraph:
	"Implementations may support additional errors not included in
	this list, may generate errors in this list under circumstances
	other than those described here, or may contain extensions or
	*limitations* [emphasis added -JZ] that prevent some errors
	from occurring."

POSIX defines the behavior of a conforming program.  A program which
closedirs a DIR pointer twice is non-conforming, and the behavior of
the implementation need not be meaningful, useful, or even helpful.
						-JZ
----------------------------------------------------------------------
John Zolnowsky		johnz@EBay.Sun.COM or ...!sun!johnz