Function, file and line information out of '_Unwind_Context' ptr

[Arnaud Charlet]

> 'addr2line' is not available on OSF-Alpha and invoking system call takes a lot

addr2line is part of binutils, and is supported under Tru64.

> of time. Say it would be also possible to call system on gdb (and my pid) to 
> retreive a backtrace with file an d line information but this is too slow for 
> memory leak detection tools.

The way all such tools work is as follows:
- record the non symbolic traceback (i.e. list of PC) at run time, which is
  not too costly
- compute the corresponding symbolic traceback off line, which is the costly
  part

The second part can be achieved using bfd directly, or indirectly via
gdb, addr2line or similar tools.

Arno