Expose __sanitizer_symbolize_pc()

[ramosian-glider]

Originally reported on Google Code with ID 322

I had to add this interface function today when hacking on NSS crypto code, which uses
function pointers heavily. I needed to know which function was being called by pointer
and this was the best solution I could come up with. Looks like it would require almost
zero effort to add this to our interface. Opinions?

Reported by earthdok@google.com on 2014-06-26 18:57:38

[ramosian-glider]

I'm not sure we want something like this in the public interface, where would have to
support it in the future.
If you only need it as a debugging aid (I assume you could not use gdb for some reason?),
you could just declare it at the call site.

Reported by eugenis@google.com on 2014-06-27 08:13:33

[ramosian-glider]

We could just say that we provide no guarantees about it being supported in the future,
since it's only intended for debugging anyway. We already do this with __sanitizer_print_stack_trace().

> I assume you could not use gdb for some reason?
The code was called several times with different function pointers, and I there was
no way to know in advance which call was the interesting one.

> you could just declare it at the call site.
It still has to be defined and declared with SANITIZER_INTERFACE_ATTRIBUTE in the runtime.

Reported by earthdok@google.com on 2014-06-27 09:00:06

[ramosian-glider]

Just curious, why do Asan users need these functions in public interface?

Reported by tetra2005 on 2014-06-27 09:18:49

[ramosian-glider]

Sometimes it's useful to have this for debugging (other code). Since we already have
code that does this, it might make sense to expose it.

Reported by earthdok@google.com on 2014-06-27 09:31:26

[kcc]

We also need __sanitizer_print_stack_trace in all the sanitizers.

[kcc]

__sanitizer_symbolize_pc is added
__sanitizer_print_stack_trace also seems to be in every sanitizer now.