llvm dev - Nov 2015 - Docs for leak checker (and other sanitizers)?

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. 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.

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.

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. 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...

-- 
greg

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
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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On Mon, Nov 9, 2015 at 7:20 PM, Kostya Serebryany <kcc at google.com>
wrote:
> Most likely, you need
> https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer
Thanks!

> 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.
Hm. That's a good point. I'm not exactly sure how the ripcord
allocator being used in Postgres combined with the asan
poison/unpoison calls would actually appear to lsan. But even aside
from that I believe there are allocations that are made early in
server initialization that are never freed and it's considered not
worth the book-keeping to free them due to the on-off nature of the
initialization.

-- 
greg