Subject: Re: NetBSD master CVS tree commits
To: Bruce Albrecht <Bruce.Albrecht@seag.fingerhut.com>
From: Greg A. Woods <email@example.com>
Date: 06/05/1996 16:02:31
[ On Tue, June 4, 1996 at 16:40:36 (-0500), Bruce Albrecht wrote: ]
> Subject: Re: NetBSD master CVS tree commits
> Greg A. Woods writes:
> > > Modified Files:
> > > eval.c
> > > Log Message:
> > > Fix PR/2504: return with no args returns 0 instead of the return value of
> > > the previous command in functions
> > I think this PR was in error.
I recant. It seems the Log Message above describes the problem, and not
> I wrote this PR, and maybe the fix, I submitted one with my PR. I was
> seeing an exit value of zero when a function returned with a return
> statement with no parameters, but all of my references (except for the
> O'Reilly ksh book) indicated that this was wrong. I don't have a copy
> of P1003.2, but if you can tell me where it's online, I'll check it
I don't think the P1003.2 drafts are online anywhere any more. They've
all been withdrawn pending approval of the final standard, so nobody can
legally give you any possibly archived copy. ;-)
> Does the following excerpt really talk about the return command, or
> just function exit status?
> > From P1003.2/D11.2 section 3.9.5, p. 276:
> > Exit_Status
> > The exit status of a function definition shall be zero if the function
> > was declared successfully; otherwise, it shall be greater than zero. The
> > exit status of a function invocation shall be the exit status of the last
> > command executed by the function.
Good question. No, it doesn't talk about the 'return' command itself.
Return is really a rather trivial little guy though, and he doesn't
really do anything but potentially fiddle with the value of ? (and of
course cause the function to return, be it the last statement or not.
Here's the description from P1003.2/D11.2 p. 305-306:
3.14.10 return - Return from a function
The return utility shall cause the shell to stop executing the current
function or dot script (see 3.14.4). If the shell is not currently
executing a function or dot script, the results are unspecified.
The value of the special parameter ? shall be set to n, an unsigned
decimal integer, or to the exit status of the last command executed if n
is not specified. If the value of n is greater than 255, the results are
undefined. When return is executed in a trap action (see 3.14.13), the
``last command'' is considered to be the command that executed
immediately preceding the trap action.
126.96.36.199 return Rationale. (This subclause is not a part of P1003.2)
The behavior of return when not in a function or dot script differs
between the System V shell and the KornShell. In the System V shell this
is an error, whereas in the KornShell, the effect is the same as exit.
The results of returning a number greater than 255 are undefined because
of differing practices in the various historical implementations. Some
shells AND out all but the low order 8 bits; others allow larger values,
but not of unlimited size.
See the discussion of appropriate exit status values in 188.8.131.52. 1
In other words, what a 'return' statement does is set the ? parameter to
'n', and not specifying 'n' is the same as giving "$?". From there the
clause in 3.9.5 simply can be interpreted to say that the exit status of
the function is the value of the ? parameter at exit.
> Are you saying that without the patched eval.c, /bin/sh on NetBSD is
> returning a non-zero value for the above or for your example below?
> If it is, then I'd like to figure out why my versions of NetBSD
> (Amiga, 1.1 and 1.2_ALPHA) are not functioning as expected.
Nope. I haven't yet tested any of this with *any* *BSD shell. ;-)
Greg A. Woods
+1 416 443-1734 VE3TCP robohack!woods
Planix, Inc. <firstname.lastname@example.org>; Secrets Of The Weird <email@example.com>