Re: [Libunwind-devel] Backtrace performance on x86-64 based on Dwarf info

[Arun Sharma]

On Mon, Jun 2, 2014 at 9:40 AM, Milian Wolff <address@hidden> wrote:

> So... what now?
>

>_ULx86_64_tdep_trace: frame va 400d28 type 0 last 0 cfa rsp+0 rbp @ cfa-1 rsp 
>@ cfa-1

>_ULx86_64_tdep_trace: new cfa 0x7fffb98a3820 rip 0x400d28 rsp 0x7fffb98a3820 
>rbp 0x0

It looks like the fast unwind path found RBP=0, but f->last_frame is
computed based on the return value of unw_step().
Does this improve the situation?

--- a/src/x86_64/Gtrace.c
+++ b/src/x86_64/Gtrace.c
@@ -254,7 +254,7 @@ trace_init_addr (unw_tdep_frame_t *f,
      common for the outermost frame (CRT stuff) on many systems.
      This avoids failing trace in very common circumstances; failing
      to unw_step() loop wouldn't produce any better result. */
-  if (ret == 0)
+  if ((ret == 0) || !rbp)
     f->last_frame = -1;