On Aug 17 13:36, Ken Brown via Cygwin wrote:
> On 8/16/2020 6:38 PM, Ken Brown via Cygwin wrote:
> > One further comment, and then I'll shut up
>
> I lied.
...which is ok.
> > and leave it to people who know what they're talking about: In the
> > 64-bit case, the function _Unwind_RaiseException in libgcc/unwind-seh.c
> > gets called, and it calls the Win32 function RaiseException as follows:
> >
> > RaiseException (STATUS_GCC_THROW, 0, 1, (ULONG_PTR *)&exc);
> >
> > Then the following comment appears:
> >
> > /* The exception handler installed in crt0 will continue any GCC
> > exception that reaches there (and isn't marked non-continuable).
> > Returning allows the C++ runtime to call std::terminate. */
> >
> > Apparently this doesn't actually happen.
>
> I'm beginning to think this is a bug in the Cygwin build of gcc. The file
> unwind-seh.c is compiled on 64-bit Cygwin because __SEH__ is defined. But
> it makes assumptions, such as those in the comment quoted above, that are
> not valid on Cygwin.
>
> In fact, if you look at the main exception handler on Cygwin
> (exceptions.cc:626), it is clear that the exception code STATUS_GCC_THROW
> does not lead to continuation. It falls under the default case:
>
> default:
> /* If we don't recognize the exception, we have to assume that
> we are doing structured exception handling, and we let
> something else handle it. */
> return ExceptionContinueSearch;
>
> [STATUS_GCC_THROW is 0x20474343, which shows up in the gdb output above as
> an unknown target exception.]
>
> So it seems to me that either Cygwin's exception handler has to learn to
> handle the exception codes defined in unwind-seh.c, or else gcc should be
> built with __SEH__ undefined.
>
> JonY, Achim, Corinna, am I missing something?
This stuff isn't really my strong point. IIUC the above comment correctly,
we might get away with adding another case to the exception handler switch:
#define STATUS_GCC_THROW 0x20474343
case STATUS_GCC_THROW:
return ExceptionContinueExecution;
Did you try that, by any chance?
Thanks,
Corinna
--
Corinna Vinschen
Cygwin Maintainer
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