sim/common: pipe syscall support

[Hans-Peter Nilsson]

> Date: Tue, 11 Jan 2005 10:07:52 -0500
> From: Andrew Cagney <cagney@gnu.org>

> Ok (this does feel very low level).

Thanks.

> However, can you also look over the remote file i/o code.  For reasons 
> of stupidity we've ended up with two slabs of code (remote hosted i/o 
> and simulator hosted i/o) doing essentially the same thing.

I am at a loss here: I cannot perform any useful audit here
compared to the simulator I/O.  I looked for a while and grepped
through the manual, but couldn't understand how the bits are
connected, so I have to leave that to a real gdb maintainer.  At
least it seems as if calls to remote-fileio doesn't end up in
the simulator and so doesn't interfere with pipe support there;
it connects to a the remote packet handler.  The remote-fileio
(whatever it's used for?) seems very simple, only the most basic
operations are there and it doesn't immediately seem a candidate
for adding pipe functionality.

> Also, think about how this will work when (yes you can laugh) GDB 
> becomes properly event driven (or failing that multi-threaded).

The simulator vs. gdb interface would have to get thread
support.  It doesn't seem like there are framework bits at the
moment.

brgds, H-P