#345 Custom trace handling: something like CALL ON EACHCLAUSE

[Miles Willmek]

It would be very useful for debugging to support custom tracing. At its simplest something like...

/ Future ooRexx release /

call on EACHCLAUSE

-- code here

exit

/ Custom watch handler /
EACHCLAUSE:
-- condition delayed until return
if x > 0 | y < 0 then do
say '*** Watch triggered, Line=' sigl
say sourceline(sigl)
say 'Watch: X=' || x ', Y=' y
trace '?I'
-- ?? EACHCLAUSE remains delayed during
-- interactive trace
end
return

/ I have no idea how much overhead would be
involved. Maybe it should require an invocation
of a new option of TRACE to enable. To take it further...
/

/ Multiple Watch Handlers /

trace 'W' -- enable custom watch handling

-- WATCH condition raised if expr = .true
call on WATCH 'WATCH1' (x > 0 | y < 0)
call on WATCH 'WATCH2' (s \== '')

-- WATCH condition raised if X or Y changes value
call on WATCH 'WATCH1' VAR X Y

-- code

exit

WATCH1:
-- handler: display name, expr, etc.

WATCH2:
-- handler

/ Maybe it could be used from the trace prompt
to enter one-off watches:

trace> call on watch NONAME (x = 0) TRACE ?I
trace> trace 999

back to trace prompt after (x = 0) or 999 clauses/

/ eventually it would be nice if signal and call
handlers could be defined for CLASSes or PACKAGEs.
/