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Re: stdcall lib functions with exception throwing callbacks vs Dwarf2 EH
- From: Danny Smith <dannysmith at clear dot net dot nz>
- To: Richard Henderson <rth at redhat dot com>
- Cc: gcc at gcc dot gnu dot org, Cygwin <cygwin at cygwin dot com>, mingw-dvlpr <mingw-dvlpr at lists dot sourceforge dot net>
- Date: Wed, 24 Nov 2004 20:50:17 +1300
- Subject: Re: stdcall lib functions with exception throwing callbacks vs Dwarf2 EH
- References: <001701c4d1ab$949322e0$0a6d65da@DANNY> <20041124003240.GA6028@redhat.com>
- Reply-to: Danny Smith <dannysmith at users dot sourceforge dot net>
Richard Henderson wrote:
> On Wed, Nov 24, 2004 at 11:27:11AM +1300, Danny Smith wrote:
>> Before I pull any more hair out trying, does any one have any hints
>> on how to use an MD_FALLBACK_FRAME_STATE_FOR to workaround ...
> That would be wrong.
> I think the most likely explanation is that there's a bug in the
> dwarf2 generator for stdcall functions with -fomit-frame-pointer,
> and the problem should be attacked there.
> If you've got a call that takes 12 bytes of arguments on the stack
> and pop them on return, then the unwind info should look like
> # DW_CFA_GNU_args_size 12
> call foo
> # DW_CFA_def_cfa_offset <previous value - 12>
Umm, actually I don't think it is stdcall thing at all.
When I reran the testcase after doing other things both the cdecl and
stdcall functions resulted in uncaught exceptions, I can't explain the
success with cdecl in my earlier report,
Sorry for the noise.
If I compile the callback-using library code with -fexceptions using a
DW2 enabled compiler, then both calling conventions work, as expected.
So is it a general requirements of DW2 EH that functions that are passed
callbacks as args be compiled with -fexceptions, if the callbacks may
throw? I don't see how else they could work
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