why does exception.cc have "unwinding" code for sjlj?

Adam Megacz gcj@lists.megacz.com
Fri Feb 1 00:20:00 GMT 2002


I don't get it -- I thought the whole point of SJLJ was that you
couldn't meaningfully "unwind" the stack to get a stack trace. Isn't
that [part of] what makes DWARF2 better than SJLJ?

#ifdef SJLJ_EXCEPTIONS
  // The given "IP" is an index into the call-site table, with two
  // exceptions -- -1 means no-action, and 0 means terminate.  But
  // since we're using uleb128 values, we've not got random access
  // to the array.
  if ((int) ip <= 0)
    return _URC_CONTINUE_UNWIND;
  else
    {
      _Unwind_Word cs_lp, cs_action;
      do
        {
          p = read_uleb128 (p, &cs_lp);
....

The main problem I'm running into is that some of the unwind code
requires libstdc++ (specifically, #include <cstdlib>), but libstdc++
has a lot of problems crosscompiling, and I'd rather just not build it
than try to get my (ugly) patches to its configure.in accepted; I'd
probably break more stuff than I would fix, anyways...

Win32 never calls the _Unwind functions anyways; it just throws an
exception out of the signal handler.

Suggestions on how to deal with this?

  - a



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