a -1 dummy frame

[Andrew Cagney]

[I'm definitly thinking out loud here.  This follows on from previous 
attempts at cleaning up the same area  Turns out my other theory about 
the shape of dinosaurs wasn't original.]

At present GDB creates its inner most frame using the call:

	create_frame (read_fp(), read_pc())

where read_fp() and read_pc() refer to the register cache.  After that, 
frames are created using something like:

	frame->frame = frame_chain (next)
	frame->pc = frame_prev_pc (next)

I think, instead, things would work better if GDB first created an 
initial frame:-1 dummy frame.  This frame would map register requests 
directly onto the register cache.  That way, the inner most frame, 
created with:

	frame->frame = frame_chain (frame:-1)
	frame->pc = frame_prev_pc (frame:-1)

could (in theory) use the same methods as every other frame.

It would also, I think, address the problem of connecting to a target 
that has a totally corrupted inner most frame.  The -1 frame would still 
exist so things could still stumble along - info registers would still 
work as it could be called with frame:-1.

There is of course a very very long gap between this theory and current 
reality.  The above would only work if the frame_chain() and prev_pc() 
code only accessed registers from the next frame via a very right 
interface (and not use all sorts of other internal knowledge as it 
currently does).

Any way, food for thought,

enjoy,
Andrew