Re: DWARF-2 EH for MinGW gcj?

[Ranjit Mathew <rmathew at gmail dot com>]

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Mohan Embar wrote:
> I know this isn't your topic of preference, but
> can you give me quick brain dump of what you know
> about or some pointers to issues of DWARF-2 EH for
> MinGW gcj?

The best person to answer these queries would
be Danny Smith and I see that he has already provided
a detailed reply (Thanks Danny!).


> - Is the only issue you know about the foreign stack
> frame issue? Or are there other caveats you know about?

IIRC, there was another problem with -fomit-frame-pointer
and "stdcall" functions:

  http://gcc.gnu.org/ml/gcc/2002-11/msg00149.html

but perhaps this issue has been resolved by now.


> - Any ideas or hunches on how to solve this problem?
> Anyone else? Unless I'm missing something, it would seem
> to me that the only way of having any hope of worming
> our way back through foreign stack frames is to save
> some state information before each call as we do with
> SJLJ exceptions (if I understand this mechanism correctly,
> which I don't claim to), which would defeat any performance
> gains we'd hope to achieve by doing away with SJLJ exceptions....

One of the approaches could be to see if the Win32 GUI
callback code has frame pointers and then walk the chain
of FPs back up the stack till we find a call frame that
has associated DW2 unwind info. This could involve ugly
code like what you can see in the implementation of
backtrace for SJLJ i386 targets in libgcj.

Another approach could be to simply declare that MinGW
GCC would not support exception propagation across
foreign function calls and move on to better things in
life. :-/

Thanks,
Ranjit.

- --
Ranjit Mathew       Email: rmathew AT gmail DOT com

Bangalore, INDIA.     Web: http://rmathew.com/




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