[llvm-dev] Docs for leak checker (and other sanitizers)?

[Kostya Serebryany via llvm-dev]

On Sat, Nov 7, 2015 at 11:55 AM, Greg Stark via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> I'm having trouble finding any documentation of the sanitizers,
> especially the leak checker -- apparently because of the move from
> code.google.com to github.

Yea. We hope to clean these up in Dec.
Help is welcome!


> Every doc has a link for "more information"
> which goes to code.google.com which just redirects to github and
> points to a placeholder doc that says lots of links are broken. I
> haven't found the docs using any google-fu or greps over the source
> tree so I'm hoping I'm just missing something.
>

Most likely, you need
https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer


>
> In particular I'm looking for a few specific pieces of API:
>
> 1) I have a server that runs in a loop but I want to use the leak
> checker to check that each trip through the loop (or more likely every
> 1,000 trips or so) hasn't leaked memory. There are obviously
> allocations prior to the main loop that are "leaked" and for that
> matter I want to skip the first few thousand trips or else various
> data structures that grow gradually will show up as leaks. So I need
> to be able to control when the leak checker actually starts looking at
> allocations and which it checks. Ideally I would want to print the
> reports and only abort if its growing consistently or by more than
> some amount but that may not be necessary if I can track down where
> the growth is currently.
>

I don't think lsan supports this mode directly,
but why do you think that the init-time allocations are going to be
"leaked"?
If there is some object still pointing to those allocations lsan will not
complain.


>
> 2) I want to use the poison/unpoison macros and function calls for
> asan and msan. However I haven't been able to find any documentation
> on this api. In particular msan and asan seem to have different
> thoughts on whether these functions should be called directly or
> through macros so I'm not sure which is the stable api.


The best documentation you can find is the the headers, [am]san_interface.h
Macros are given for convenience, you don't have to use them.
api is pretty stable


> Also I have no
> idea when to call __msan_allocated_memory() and company but I suspect
> it's relevant for giving msan enough information about a pool
> allocator to find leaks...
>

msan and lsan do not work together yet, so there is not reason to call msan
api if you want to increase lsan sensitivity.
asan does work with lsan, and marking some stale memory as poisoned in asan
mode gives some advantages:
E.g. see
https://github.com/google/sanitizers/wiki/AddressSanitizerContainerOverflow
(at the bottom)


hth,

--kcc


> --
> greg
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