[Bug libstdc++/64535] Emergency buffer for exception allocation too small

["rguenther at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64535

--- Comment #18 from rguenther at suse dot de <rguenther at suse dot de> ---
On Tue, 27 Jan 2015, redi at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64535
> 
> --- Comment #17 from Jonathan Wakely <redi at gcc dot gnu.org> --- Ah, I 
> assumed the lack of destructor was intentional, so we can still deal 
> with exceptions while destroying globals. Otherwise an exception could 
> try to allocate from the pool after the destructor has run.

Well - technically accessing emergency_pool after its default destructor
ran is undefined (though we don't seem to run any destructor on it...
I wonder if we do for __scoped_lock and if that works).

I hope that initialization/destruction order imposed by some means
allows EH to be thrown during initialization or destruction (though
what would catch that?)

We can make the patch safer by using

  pool::~pool ()
    {
      __gnu_cxx::__scoped_lock sentry(emergency_mutex);
      free (arena);
      arena = NULL;
    }

and/or by attaching a init_priority to the class.

But again - where can you catch exceptions thrown from global
initializers / destructors?  If I throw from a __thread global
constructor will the parent process be able to catch that exception
somehow?