[cfe-dev] Brainstorming: ASAN snapshots

[Kostya Serebryany via cfe-dev]

On Mon, Oct 10, 2016 at 6:45 AM, Kim Gräsman via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> Hi all,
>
> I'm debugging a memory leak in a large code base, and it's not going
> very well. Let's say I have plenty of time to think about other
> things.
>
> I was wondering if it would be possible to use the sanitizer
> infrastructure to generate memory usage snapshots, something like a
> report mapping allocation backtrace to number of outstanding
> allocations.
>
> With something like that in place, it should be easy to catch leaks
> where memory is still reachable but kept alive indefinitely. Take two
> snapshots and diff -- the backtraces growing in outstanding
> allocations are prime suspects. I think gperftools/tcmalloc has a mode
> like this, but I haven't used it myself.
>
> Is this at all feasible?


Yes. Take a look at lib/asan/asan_memory_profile.cc and
test/asan/TestCases/Linux/print_memory_profile_test.cc
It's a toy memory profiler which prints the current allocated memory
chunks.
Very close to what you are describing (if not exactly that)

I used this functionality myself in a situation similar to yours and it
helped.



> Are patches welcome?


It depends. I am currently  not ready to review large refactoring in this
code because
I hope to make one myself (maybe...)
Small incremental improvements -- yes.

--kcc


> I can't say I understand
> ASAN very well, but it feels like there is basic infrastructure
> already in place for this.
>
> Thanks,
> - Kim
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