Crashing Squeak

Maloney johnm at
Tue Sep 22 15:27:17 UTC 1998


While it is likely that you've been tickling a VM bug of some
sort, there are several other possibilities to keep in mind. The
first is that your computer has a sporadic hardware glitch,
something like a bad memory chip. The second is that some other
application has a wild pointer that is sometimes smashing
Squeak's ObjectMemory. The latter may be less likely under
Win32 than it is on the Mac, which has no memory protection
between applications.

Squeak presents a large but fragile memory target. Other
applications have a lower density of pointers and are less
likely to periodically trace all of their pointers the way
the Squeak garbage collect and become: primitives do. Thus,
Squeak is the "canary in a coal mine" that is likely to
detect system problems earlier than other applications.

>From your description, it sounds as though (a) this problem
is intermittant, (b) it doesn't seem reproducible (your current
image is already damaged, but we don't know a sequence of steps
that causes it to become damaged), (c) it has persisted across
a large number of Squeak versions (it didn't just appear), and
(d) the VM has been reliable for a great many other folks, even on
the same platform. These facts fit the "non-Squeak system problem"
hypothesis. They also fit the hypothesis that your usage of
Squeak is unusual in some way that tickles a long-standing
VM bug. Are there any more bits of evidence that might tip the
scales in one or the other direction? For example, have you seen
similar crashes on several different machines? Have you had
problems with other apps crashing mysteriously? Is there any
corrolation between Squeak crashing and having some other
application running? On the Mac, for example, an older version
of Netscape often caused Squeak to crash. Have you been
using Squeak in unusual ways, or using primitives that
might not be too heavily exercised?

I believe Dan is planning to dissect your image with bit
tweezers, and that may shed some light on the problem.

	-- John

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