Re: [patch] Update catch(...) handlers to deal with __forced_unwind

[Jonathan Wakely <jwakely at redhat dot com>]

On 06/06/14 12:40 +0200, Uros Bizjak wrote:
> On Fri, Jun 6, 2014 at 11:19 AM, Jonathan Wakely <jwakely@redhat.com> wrote:
> > On 06/06/14 10:27 +0200, Uros Bizjak wrote:
> > > These two tests timeout on alpha-linux-gnu:
> > >
> > > FAIL: 30_threads/async/forced_unwind.cc execution test
> > > WARNING: program timed out.
> > > FAIL: 30_threads/packaged_task/forced_unwind.cc execution test
> > > WARNING: program timed out.
> >
> >
> > Sorry about that, I don't know why.
> >
> > Does pthread_exit(0) use a __forced_unwind exception on
> > alpha-linux-gnu? This should tell you ...
> >
> >
> > #include <bits/cxxabi_forced.h>
> > #include <pthread.h>
> >
> > void* f(void*) {
> >  try
> >  {
> >    pthread_exit(0);
> >  }
> >  catch (__cxxabiv1::__forced_unwind const&)
> >  {
> >    __builtin_puts("unwind");
> >    throw;
> >  }
> >  catch (...)
> >  {
> >    __builtin_puts("something else");
> >    throw;
> >  }
> > }
> >
> > int main()
> > {
> >  pthread_t t;
> >  pthread_create(&t, 0, f, 0);
> >  pthread_join(t, 0);
> >
> > }
>
> Strange, I don't get anything ...
>
> $ g++ -lpthread pt.C
> $ ./a.out

That explains it then: the thread just goes away, and the waiting
function hangs forever expecting the future to be made ready.

The test assumes pthread_exit is implemented by throwing
__forced_unwind, which apparently isn't true for all glibc targets.

If the thread just goes away there's no way to make the future ready.
I guess we should just XFAIL it for alpha, and maybe other targets.