[LLVMdev] RFC: Exception Handling Proposal II

[Duncan Sands]

Hi Renato,

> On 25 November 2010 13:31, Duncan Sands<baldrick at free.fr>  wrote:
>> In short, all destructors are run, and if any
>> throw
>> exceptions then that fact is noted somewhere (and the exception is not
>> allowed
>> to propagate) and once all destructors have had a chance to run then one
>> instance of Program_Error is thrown at the point of scope exit.
>
> I see, like keeping the exceptions in a queue as they happen and deal
> with each one in order, until the queue is empty.

not really, there is no queue and no need to keep track of the exceptions
destructors are throwing [*].  The following pseudo-code may explain:

   bool saw_exception = false;
   for each destructor:
     try { run(destructor); }
       catch (...) { saw_exception = true; }
   if (saw_exception) throw Program_Error;

> It's harder to print stack-traces to the user, but this discussion is
> becoming off-topic. ;)
>
> Anyway, thanks for the explanation!

Yeah, probably highly off-topic (unless someone tries to bake C++ cleanup
behaviour into the new LLVM exception handling model...), so let's stop here.

Ciao,

Duncan.

[*] In Ada you can't throw general objects so there is no problem finalizing
any exceptions: finalizing an exception never throws an exception.