Expose __sanitizer_symbolize_pc()

[GoogleCodeExporter]

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?

Original issue reported on code.google.com by earth...@google.com on 26 Jun 2014 at 6:57

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Original comment by earth...@google.com on 26 Jun 2014 at 6:57

• Added labels: Type-Enhancement
• Removed labels: Type-Defect

[GoogleCodeExporter]

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.

Original comment by euge...@google.com on 27 Jun 2014 at 8:13

[GoogleCodeExporter]

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.

Original comment by earth...@google.com on 27 Jun 2014 at 9:00

[GoogleCodeExporter]

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

Original comment by tetra2...@gmail.com on 27 Jun 2014 at 9:18

[GoogleCodeExporter]

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.

Original comment by earth...@google.com on 27 Jun 2014 at 9:31