Messages in this thread | | | Date | Mon, 2 Aug 2010 19:59:47 +1000 | From | Nick Piggin <> | Subject | Re: [PATCH 11/19] perf record: Release resources at exit |
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On Mon, Aug 02, 2010 at 11:17:14AM +0200, Ingo Molnar wrote: > > * Nick Piggin <npiggin@suse.de> wrote: > > > On Mon, Aug 02, 2010 at 09:54:22AM +0200, Ingo Molnar wrote: > > > > > > * Nick Piggin <npiggin@suse.de> wrote: > > > > > > That's certainly true but there's no valgrind crappiness here: valgrind simply > > > can do a better job of finding leaks if there's a well defined "all resources > > > the app still knows about are freed now" point. > > > > "noise" sounds like false positives though. [...] > > Every predictive bug detection scheme is open to the potential of false > positives. I've yet to see a complex one that is 100% false positive free.
So long as false positive noise can be easily avoided in running of the automated testing -- ie. not worked around in the software -- then this is totally fine of course.
> > [...] Certainly if this is instead allows valgrind to run in a particular > > mode that assumes no application resources consumed at exit(2) time, I > > wouldn't call it crappy :) > > Most apps free their stuff before they exit - i do it in all my own C apps. > > That is generally useful: for example it makes it easier to thread a program > later on - when exit() becomes pthread_exit() and a silent leak turns into a > real leak. > > Hence Valgrind checking for exit() by default looks useful to me.
Sure, most of the time I would too (in fact, all the time seeing as I don't write non-trivial user programs). But when you're doing last pass optimisations, it would be very reasonable to avoid things like teardown of complex data structures.
> > But you could equally sprinkle in other valgrind specific annotations or > > semantics at various points in the code to improve its coverage, no? > > Yeah, and exit() sounds like a pretty convenient point, right? That's the > point where all resources are inactive hence a scan for leaks is expected to > be the most efficient in finding real leaks.
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