Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm
List-Subscribe: <mailto:cygwin-subscribe@cygwin.com>
List-Archive: <http://sourceware.org/ml/cygwin/>
List-Post: <mailto:cygwin@cygwin.com>
List-Help: <mailto:cygwin-help@cygwin.com>, <http://sourceware.org/ml/#faqs>
Sender: cygwin-owner@cygwin.com
Mail-Followup-To: cygwin@cygwin.com
Delivered-To: mailing list cygwin@cygwin.com
Date: Wed, 24 Nov 2004 20:50:17 +1300
From: Danny Smith <dannysmith@clear.net.nz>
Subject: Re: stdcall lib functions with exception throwing callbacks vs Dwarf2 EH
To: Richard Henderson <rth@redhat.com>
Cc: gcc@gcc.gnu.org, Cygwin <cygwin@cygwin.com>,
   mingw-dvlpr <mingw-dvlpr@lists.sourceforge.net>
Reply-to: Danny Smith <dannysmith@users.sourceforge.net>
Message-id: <000c01c4d1fa$3f297fd0$e56d65da@DANNY>
MIME-version: 1.0
Content-type: text/plain; charset=iso-8859-1
Content-transfer-encoding: 7bit
References: <001701c4d1ab$949322e0$0a6d65da@DANNY> <20041124003240.GA6028@redhat.com>

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

Danny

> r~


--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Problem reports:       http://cygwin.com/problems.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/