Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!rice!uw-beaver!uw-june!smann
From: smann@cs.washington.edu (Stephen Mann)
Newsgroups: comp.lang.postscript
Subject: pscal memory leaks
Keywords: drawgrid, drawfill
Message-ID: <10339@june.cs.washington.edu>
Date: 11 Jan 90 04:33:58 GMT
Distribution: na
Organization: U of Washington, Computer Science, Seattle
Lines: 50


After posting my latest version of pscal, I discovered that it failed to
work as advertised: if you tried to print an entire year, it would only
print the last 3 months of that year.

It turns out there are a couple of memory leaks, or rather, procedures that
leave things on the stack.  These leaks aren't in the oldest version I have:
they appear to have been introduced when the calendar format was changed
to the current format (the original format drew about 10 horizontal lines 
for each day instead of a box).  The leaks aren't bad enough to affect 
the printing of a single calendar page, but when multiple pages are
printed you get a stackoverflow error.

Anyway, one leak is in drawgrid, the other in drawfill.  Both are in for
loops that don't use their loop control variables; the loop control variable 
is left on the stack.  In both cases you merely need to add a 'pop' on entering
the loop.  More precisely, the following changes will eliminate the leaks:

In drawgrid change

		0 1 5 {
			gsave
			100 0 rlineto

to
		0 1 5 {
			pop
			gsave
			100 0 rlineto

and in drawfill change

	0 1 start 1 sub {
		gsave
		.9 setgray

to

	0 1 start 1 sub {
		pop
		gsave
		.9 setgray


I emailed a few people a "patched" version that put a mark on the stack and
cleared to the mark everytime it printed a page.  Those versions will work
just fine; however, go ahead and make the above changes if you like.


Steve