Bug 973552 - valgrind gives false positive 'definitely lost' reports
valgrind gives false positive 'definitely lost' reports
Product: Fedora
Classification: Fedora
Component: valgrind (Show other bugs)
Unspecified Unspecified
unspecified Severity unspecified
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Assigned To: Mark Wielaard
Fedora Extras Quality Assurance
Depends On:
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Reported: 2013-06-12 04:27 EDT by David Woodhouse
Modified: 2015-02-17 10:32 EST (History)
7 users (show)

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Last Closed: 2015-02-17 10:32:45 EST
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Description David Woodhouse 2013-06-12 04:27:20 EDT
Once upon a time, I could run Evolution and its helper processes in valgrind, as long as I set G_SLICE=always-malloc, and any report of memory being 'definitely lost' was fairly certain to be true. I don't remember any false positives.

I last did this in late 2010; see https://bugzilla.gnome.org/showdependencytree.cgi?id=627707&hide_resolved=0

I had another go yesterday, and filed a few 'definitely lost' reports in GNOME bugzilla after doing very basic triage on them. And some of them look very much like they were false positives. There are some examples of basic structures like GString being used, which are clearly freed a few lines after they are created. Unless GLib has developed some egregious brokenness in its core data structures, valgrind seems to have got broken.

These appear to be false positives:

Valgrind also fails to track thread-local storage:
https://bugzilla.gnome.org/show_bug.cgi?id=702021 and probably also

It would be really useful to get back to the point where valgrind can sanely be used to track memory leaks in programs like Evolution again. It's bad enough that there's an unmanageable number of 'possibly lost' reports which are mostly false positives; for 'definitely lost' to start being untrustworthy too is really a PITA.

Deliberately filing this in distro bugzilla so it can be assigned to other components if appropriate. I think we have "real" maintainers here for all relevant parts.
Comment 1 Mark Wielaard 2013-06-12 05:38:10 EDT
> These appear to be false positives:

If you could provide the exact fedora package versions involved and the steps you did you trigger the leak that would help to reproduce the issues.

> Valgrind also fails to track thread-local storage

If you could provide a minimal example just using the pthread constructs without glibs own memory handling intertwined that would be really helpful.
Comment 2 David Woodhouse 2013-06-12 06:01:01 EDT

There is an unanswered question from 2005 about valgrind's handling of pthread_key_create(): http://valgrind.10908.n7.nabble.com/pthread-key-create-question-td33955.html
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