Pexec :)

["James Cox" <jamesco@cogs.susx.ac.uk>]

I have been fiddling around over the past couple of days, trying to do two
ultimately simple things.

Firstly, I thought I'd try and get around the fact that MiNT doesn't have a
non-blocking fork by using Pexec's mode 104 (I think) that just runs a
basepage concurrently where the child shares the parents memory. The basepage
I passed was the parents... (I have this little bit of code that checks a flag
that tells the process if it's the child or parent :) Everything worked really
well, except that if the child terminates before the parent, the child enters
EXIT state until the parent terminates...

Secondly, I was trying to get around the really annoying aspect of GEMDOS that
hath plagued my life since the dawn of time - the fact that when a program is
first executed, it is given ALL of the availalbe memory. This causes no end of
problems for me, so I thought I'd use Pexec's mode 3 (I think) to just load
the program I want to execute and shrink its memory block before the thing is
run. All this is done in supervisor state so as to halt multi-tasking until
the memory is freed.

Then I use Pexec's mode 106 (this one I know :) to execute the program such
that is doesn't share memory with the parent. This way, I figured, I could
build a little routine called MyPexec or something which laugned an
application as if you'd done it with mode 100 of Pexec.

However, I found the same problem as with my little fork program - if the
child terminates before the parent, then the child sit in an eternal EXIT
state until the parent terminates.

The only thing I can't quite understand is that whilst in the EXIT state, the
process is not, according to TOP, using any memory (or processor time :) but
still registers. If I try to kill it from TCSH, then it says that it couldn't
find the process... Why doesn't MiNT dump the thing and be done with it? Is
there a way of doing what I am attempting that I am unaware of?

As as result of these pass few days, I would like to propose a new flag for
Pexec that indicates that the program should be loaded into a memory block
just big enough for the program. I understand that this would cause some
difficulty, since the program being launched in this way would have to be able
to detect whether or not it needs to perform a memory shrink call or not,
otherwise it won't run very nicely without MiNT.

Apologies for waffling on a bit :)

Cheers,

James Cox
<jamesco@cogs.susx.ac.uk>
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