John asks,
> Do you know why this would now be "undocumented"?  UNLOADPROC was
> documented - it seems to me that it was once important to be able
> to unload a procedure; is it now not important to be able to do
> so?

I suspect that it's more that the MPE/XL design didn't consider (or have
time to include) the need to "unload" things, so that unloading NM libraries
is rather difficult since lots of things are probably coded to assume that
if something was there a minute ago then it will still be there now, and
having things unexpectedly disappear could cause various kinds of breakage.

NM libraries include features like module local data, and there's the
question of what to do with the memory allocated for this data when you
unload the module, since the code that's using it probably isn't expecting
to go away, and there might be things holding pointers to it, etc.

Since there is no standard unload mechanism, there's probably no code hook
that would allow a module to get control at the time it is requested to be
unloaded that would give it a chance to clean up, etc., so any use of the
undocumented unload functionality is probably going to be extremely
unsupported, and perhaps highly dangerous if applied to arbitrary code
written by third parties.

G.

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