Re: C++ exceptions

Pedro Alves wrote:
> Kevin O'Connor wrote:
> > On Sun, Jul 01, 2007 at 08:12:33PM +0100, Pedro Alves wrote:
> > > Danny Backx wrote:
> > > > void Handle(struct _EXCEPTION_RECORD *ExceptionRecord,
> > > >                 void *EstablisherFrame,
> > > >                 struct _CONTEXT *ContextRecord,
> > > >                 struct _DISPATCHER_CONTEXT *DispatcherContext)
> > > > {
> > > >         throw WindowsException(ExceptionRecord, EstablisherFrame, 
> > > > ContextRecord, DispatcherContext);
> > > > }
> > > I'm not sure that is safe.  You are throwing away from a callback started
> > > from the kernel.  I think the safest is to tweak the current threads
> > > context with GetThreaContext/SetThreadContext to point the pc at a different
> > > address like your registered handler, and return
> > > EXCEPTION_CONTINUE_EXECUTION.  Then, in that handler, you're got the stack
> > > setup as if the exception called directly into your handler, and it should be
> > > safe to throw a c++ exception.  Take another look at cegcc's startup.c for
> > > inspiration - It already does something similar.
> > Is it safe to enter an exception handler using the calling program's
> > stack?  That is, if you set the pc to a handler and call
> > EXCEPTION_CONTINUE_EXECUTION that handler will alter the stack and
> > registers of the function that raised the exception.  Are we
> > guarenteed that this is okay?
>
> Of course, just changing the pc is not enough.  We have to setup a
> new stack frame.  Really, you should look at newlib/libc/sys/wince/startup.c:
>
> Let me see if I can come up with something in the following days.

OK, here is my take.  See/try attached.

- It shows that it is possible to have SEH/ARM with a few
  macros (to hide the __asm__).
- It shows that is is possible to wrap SEH in c++ exceptions.
- It shows that is can be pretty much cleaned up. :)
- It shows that there is no need to change the entry point.

Cheers,
Pedro Alves

test_eh.tar.gz
Description: application/gzip

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