lclint-interest message 119

From Tue Nov  5 16:17:53 1996
Date: Fri, 1 Nov 1996 19:18:50 -0600 (CST)
From: Peter Seebach 
Subject: a kind of memory leak...

I'm wondering if anyone can suggest a good way to track the following
special case of "memory leak".

I have a library implementing objects.  The objects act vaguely like
"strings" in C, and are intended to have semantics similar to pointer-to-char,
but can contain null bytes safely.  The end result is that the analogue
to strchr() returns an *allocated* object.  The object is tracked; a
reference to it is kept by the string into which it "points", so changes
can be correctly propagated.  So...

When the "parent" string is freed, all of the children produced by the
strchr() analogue are freed.  Thus, At The End Of Time, I can determine
that no memory has been leaked...

But at runtime I can easily have many megabytes of unused objects to
which I have no user-visible references.

I did track this down and eliminate it, but I'm wondering if anyone can
suggest a method to track it.  What did was run a program using the
library on two data files, one much larger than the other.  I track
memory allocation, and if the bug is manifesting, the processing of
the larger file has larger peak memory usage.

However, this is far from optimal, of course.  The bug survived for nearly
two days, because intutively, I don't expect to need to free the results
of strchr() or any similar function.  (And technically, I don't, but I
don't want to leave them around if they're allocated, even if they will
be freed eventually.)


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University of Virginia, Computer Science