System V and SIGCLD

[Brett Galloway]

In article <453 at rtech.UUCP> jas at rtech.UUCP (Jim Shankland) writes:
>Guy Harris writes:
>
>    Just don't run programs [needing the SIGCLD signal] on a SVID-compliant
>    system unless you've verified that that system also supports SIGCLD.
>
>    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.
>
>    Consider SIGCLD to be an extension to UNIX, provided by certain systems,
>    rather than as part of the core of UNIX.
>
>All true, but SIGCLD is an awfully useful piece of UNIX to be leaving out
>of SVID, especially when there is no persuasive reason to leave it out
>(unlike shared memory, for example, which is hard to implement on
>a loosely coupled multiprocessor such as the CT Megaframe).  If the
>interface definition is unnecessarily restrictive, it loses some of
>its usefulness, since it is likely to be extended in non-standard ways
>(Pascal comes to mind).

Here here!  Standards definitions can fail in one of two ways.  The first is
making the standard unnecessarily generous in features (e.g. ada).  This makes
applications difficult to port because the intended environment to port to may
not have implemented a feature needed by the application.  The second failure
is making the standard unnecessarily miserly in features (e.g. the SVID with
respect to SIGCLD).  This makes applications difficult to port because each
implementation of the standard is likely to extend it in its own way to
provide useful functionality.  To be useful and portable, the standard must
strike the golden mean.  I have not read the SVID, but the omission of
SIGCLD leads me to believe that the authors of SVID inclined to the latter
error.
-- 
-------------
Brett Galloway
{pesnta,twg,ios,qubix,turtlevax,tymix,vecpyr,certes,isi}!wjvax!brett