[OpenBIOS] [patch 6/6] Prevent dereferencing page zero and complain about invalid handles

Mark Cave-Ayland mark.cave-ayland at siriusit.co.uk
Sat Aug 22 12:51:58 CEST 2009

Blue Swirl wrote:

>> In fact for me it takes so much extra time that I'm inclined to reimplement
>> some forth code as C equivalents to keep debugging manageable.

I totally feel your pain, having worked on various parts of the FCode 
interpreter. However, I don't think re-engineering in C is the right 
solution for lack of OpenBIOS debugging - you're just pushing the 
problem elsewhere :(

> Right, I wish there were equivalents of gdb breakpoints and commands
> 'where', 'up', 'down'. Doesn't rstack contain the return addresses?
> Some code pushes other stuff to rstack, though.

Yeah - please see my previous post to the list about this. Storing 
additional debug information in the current rstack frame isn't possible, 
since any Forth word that pops/re-pushes onto the rstack loses this 

My current implementation attempts to maintain a separate colstack and 
use that instead - however this doesn't work as the number DOCOL and 
SEMIS never match. I suspect this is to do with the trampoline, although 
since it is so badly documented, I'm not exactly sure how this works 
with, say nested execute words for example :(



Mark Cave-Ayland - Senior Technical Architect
PostgreSQL - PostGIS
Sirius Corporation plc - control through freedom
t: +44 870 608 0063

Sirius Labs: http://www.siriusit.co.uk/labs

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