[LLVMdev] -f[no-]omit-frame-pointer

Joerg Sonnenberger joerg at britannica.bec.de
Tue Dec 27 16:00:45 PST 2011

On Tue, Dec 27, 2011 at 12:35:52PM -0800, Kostya Serebryany wrote:
> On Tue, Dec 27, 2011 at 12:22 PM, Joerg Sonnenberger <
> joerg at britannica.bec.de> wrote:
> > On Tue, Dec 27, 2011 at 12:10:54PM -0800, Kostya Serebryany wrote:
> > > What would be the best fix for asan?
> >
> > Can you be explicit what you need to asan? Just the equivalent of
> > __builtin_return_address(0) or do you really need a full stack trace?
> >
> asan-rt uses __builtin_return_address(0) to get the full stack trace.
> See compiler-rt/lib/asan/asan_stack.cc (AsanStackTrace::FastUnwindStack)
> It checks the current thread's stack bounds to avoid a wild dereference.
> Asan does not use unsafe __builtin_return_address(N, N>0), although it
> would be nice if __builtin_return_address(N, N>0) had safer semantics.

That's inconsistent :) __builtin_return_address(0) works with or without
frame pointer. What doesn't work is depending on the frame pointer on
the stack to "speed up" the unwinding further. So what is it?


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