I'm fighting a now-you-see-it now-you-don't kind of bug and I was wondering
if there's a way to completely turn off garbage collection and memory
re-use for debugging?
My problems vanish when seemingly insignificant things happen, and
re-appear again later. For example, I'll take a line of text (simplified):
save S0 # "20 GOTO 10"
bsr TOKENIZER
restore I5
save VARWIDTH # (10)
save " "
bsr PAD
restore S1
dec I5
concat S22, S1 # S22 is now "20 "
concat S22, S0
concat S22, TERMINATOR # S22 now reads "20 20 GOTO 10#"
bsr CLEAR # Clean stack
Much later on, I'll look in S22 and find that the part that once read as it
did above, now reads:
"20 #"
With the in-between text...vanished. Sometimes adding a diagnostic "print"
statement makes it go away. Sometimes adding two makes it come back
again. Having the interpreter handle some programs makes everything fine
but just jumping in and loading WUMPUS right away makes it die.
I'm completely positive I'm not clearing that piece of real
estate...something else is doing it. But what, I dunno. Why, I know even less.
[This causes the occasional "wrong type on stack" errors in BASIC. I get
the error because I pull the line from S22 (which is now nothing but
spaces) and attempt to extract the line number from it... and fail. This
is really a Should Not Happen error because the line number was verified
(in the real code) as it was stuck into S22. This can happen during a LOAD
or RUN on typed-in programs where S22 gets populated. To see for yourself,
start parrot basic and immediately type (and nothing else, no typos):
10 PRINT "HELLO WORLD"
20 GOTO 10
LIST
And the listing will have a blank line 20 under Win32, recent builds of
parrot. If you type an empty line anywhere in this process (just a return)
or any other keywords after the Ready prompt the problem goes away magically.]
