Your change of Apr 24 2010 introduced the second argument to common_init, and 
used it to pass 1 (use_prev_instr set) from unw_init_local and 0 
(use_prev_instr clear) from unw_init_remote.  I don’t know how those choices 
were made, but for my purposes, the choice for unw_init_local was wrong, and I 
have to change that decision in the copy of libunwind that we’ll use here.  I’d 
welcome an explanation of that decision.

Doug


> On Mar 24, 2017, at 11:37 AM, Lassi Tuura <[email protected]> wrote:
> 
> What platform are you on? fetch_proc_info() should auto-detect signal frame 
> and set use_prev_instr accordingly using the (kernel-provided) frame 
> annotations detected in parse_cie(). I don't know if that works for anything 
> but linux (and possibly x86_64 only at that). Looks like there may be some 
> support for freebsd.
> 
> On Thu, Mar 23, 2017 at 8:45 PM, Doug Moore <[email protected] 
> <mailto:[email protected]>> wrote:
> When unw_init_local uses common_init to set use_prev_instr, and then 
> fetch_proc_info decrements ip, based on use_prev_instr, unw_step fails for me.
> 
> I’m putting a temp break point at the start of _dl_runtime_resolve, and when 
> gdb gets there, I’m sending a signal to trigger a signal handler that invokes 
> unw_step.  What happens, sadly, is that the instruction pointer is 
> decremented, so the eh_frames search doesn’t find the right frame, so the 
> step fails.
> 
> If only I could clear that use_prev_instr field.  So far, I don’t have any 
> better choices than to hack the libunwind source and maintain my own local 
> branch.  Are there any better ideas?
> 
> Doug
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