Re: reverse debugging implementation + commands

David McQuillan
2010-08-25T20:43:19Z

Just a bit on testing for conditions when going backwards.

Just had a look at reverse.c and it is very different from anything I
ever did. To find the last time a location was changed for instance it
looks like it would go back one instruction at a time until the
condition is satisfied. I can see a middle way that encompasses both
approaches in that if the registers are saved on every single
instruction my approach ends up being the same as what reverse.c does so
I've written it up here that way:

set found counter to unset
set check counter to here
while found counter is null and we can go backwards
roll back from check counter to previous save point
go forward till check counter reached
if condition set then
set found counter to instruction counter
endif
if found counter not set
roll back to last save point
set check counter to this point
endif
endwhile

At the end of this found counter if set gives the instruction counter
when the condition was last satisfied.

With this there is no special work needed to check conditions when going
backwards compared to going forwards.

David