[RFA 5/6] Remove unused variables

[Paul_Koning@Dell.com]

> On Jul 20, 2016, at 2:36 PM, Maciej W. Rozycki <macro@imgtec.com> wrote:
> 
> ...
> Overall with recent and less so improvements to GCC's and other 
> compilers' optimizers I think these heuristic unwinders have hardly any 
> value nowadays, they seem unable to get through function prologues 
> containing arbitrary instructions thrown there by the scheduler.  This is 
> very annoying in a common case where you interrupt a debuggee in the 
> middle of a sleeping syscall, with no way to backtrace through stripped 
> system shared libraries.

My experience is that the heuristic unwinders can be made to handle a lot of what's thrown at them now, but it takes quite a lot of extra heuristics to do so.  I have much of this on an internal version.  Should I look into making them available?

One thing I've done that may not be generally interesting: make the unwinders work in the kernel (NetBSD) and able to unwind across exception frames so you can use kernel debugging and see the stack all the way into the calling process.  I haven't found this all that interesting in online debugging, but it has sometimes been useful in analyzing kernel crash dumps.

	paul