[compiler-rt] Fix missing frame with stackwalking on windows 64-bits

[etienneb]

Summary

Fix missing frame with stackwalking on windows 64-bits

[rnk]

This passes the 32-bit tests? I would at least expect all the stack frames to be off by one now...

[etienneb]

In D22358#484147, @rnk wrote:

This passes the 32-bit tests? I would at least expect all the stack frames to be off by one now...

It should pass all tests:

// Skip the RTL frames by searching for the PC in the stacktrace.
 uptr pc_location = LocatePcInTrace(pc);
 PopStackFrames(pc_location);

This is removing stackframes above the pc_location. So, as I get it, this should always be valid.
The drawback, when there is more than 32 stackframe, we may miss the last one.

[rnk]

lgtm

lib/sanitizer_common/sanitizer_win.cc

 }
 
 #if !SANITIZER_GO
 void BufferedStackTrace::SlowUnwindStack(uptr pc, u32 max_depth) {
   CHECK_GE(max_depth, 2);
   // FIXME: CaptureStackBackTrace might be too slow for us.
   // FIXME: Compare with StackWalk64.
   // FIXME: Look at LLVMUnhandledExceptionFilter in Signals.inc
-  size = CaptureStackBackTrace(2, Min(max_depth, kStackTraceMax),
+  size = CaptureStackBackTrace(1, Min(max_depth, kStackTraceMax),
                                (void**)trace, 0);
   if (size == 0)
     return;
 
   // Skip the RTL frames by searching for the PC in the stacktrace.
   uptr pc_location = LocatePcInTrace(pc);
   PopStackFrames(pc_location);
 }