System V and SIGCLD

[Guy Harris]

> I guess I'll rephrase the question since it hasn't generated quite the
> response I had hoped for.

The response you had hoped for was an explanation of why SIGCLD disappeared.
Since it *didn't* disappear, there is no chance of getting quite that
response.

> 1) I could not find any mention of SIGCLD in the System V Interface 
>    Definition. Is this because I missed it, or is it because it just
>    ain't there? (It certainly is not mentioned with the other signals
>    in the section dealing with the 'signal' service routine)

It is not there.  It is in the S5 documentation (and, as pointed out, the
"this may disappear evenutally" note disappeared in S5R3), but it's not in
the SVID.  The SVID != the System V documentation.

> 2) Assuming the latter, does this not mean that there is no requirement
>    for a SVID adhering UNIX to include SIGCLD?

Yes.

> 3) If so, what gives? As has been pointed out, at least a couple of
>    important programs are going to break?

So?  Just don't run those programs on a SVID-compliant system unless you've
verified that that system also supports SIGCLD.  There is also no
requirement that a SVID-compliant system implement the routines in the
"-lPW" library, either, and this may break some programs.

A SVID-COMPLIANT SYSTEM IS NOT REQUIRED TO BE ABLE TO RUN EVERY PROGRAM EVER
WRITTEN FOR SYSTEM V.  It is not even required to be able to run every
program whose source is shipped with System V.  That's why it's called an
"interface definition"; a SVID-compliant system is required to be able to
run every valid program written using the SVID.  The SVID defines an
interface, and people write programs to use that interface.

Some programs that come with System V are not written strictly for that
interface.  As such, they may not run on all SVID-compatible systems.

Consider SIGCLD to be an extension to UNIX, provided by certain systems,
rather than as part of the core of UNIX.  There's nothing wrong with that
system also providing an "init", or "shl", or whatever, that uses that
extension.  If another system doesn't have that extension, it'll have to do
things differently.
-- 
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy at sun.com (or guy at sun.arpa)