[Python-Dev] update on memory leaks in 2.2 (original) (raw)

Guido van Rossum guido@python.org
Fri, 07 Dec 2001 12:44:04 -0500

Insure labels them as (paraphrasing) "memory still allocated at exit", distinct from memory leaked. I think this is equivalent to Purify's "potentially leaked" and "leaked" memory respectively.

I don't think so. Insure (uselessly) lists all memory that's still allocated and reachable at exit. Purify only reports certain blocks (in this case they were a bunch of weak refs) as potentially leaked. I'm not sure what makes them potentially leaked, but it must be a stronger condition than "still exists at exit". As Fred mentioned, this may have to do with the weaklist free list implementation.

Note that at least stringobject.c has a hook for clearing out all those interned strings at program shutdown time, which I added to clean up Insure's output. When INTERNSTRINGS is defined, the extra function PyReleaseInternedStrings() is defined. Then, in Modules/main.c, in PyMain(), if INSURE is defined that function is called, so this memory doesn't show up in the report.

It may be worthwhile generalizing this approach, and adding it to other static long-lived data structures, simply as an aid to memory debugging. As long as it isn't enabled by default, that should be fine.

Most types that have a custom free list already have a cleanup routine that's always called by Py_Finalize(); the weakref free list is lacking one. The interned list is special because it's generally unsafe to clear it out when Py_Finalize() might be followed by Py_Initialize() again -- that's why it's only done when running Insure++.

--Guido van Rossum (home page: http://www.python.org/~guido/)