druntime function to query whether any exception is "in flight"

[Andrei Alexandrescu]

On 10/20/20 11:23 AM, Adam D. Ruppe wrote:
> On Tuesday, 20 October 2020 at 15:16:33 UTC, Andrei Alexandrescu wrote:
>> One change please - can you have it return the current exception as a 
>> Throwable (and null if no exception in flight)?
> 
> 
> and prolly at least document that it shouldn't let the reference escape 
> cuz otherwise it complicates memory freeing of the exception.
> 
> basically it would be a borrowed reference. again at least just 
> documented, not necessarily enforced, but people should be aware 
> escaping it is UB.

Nice.

extern(C) scope(Throwable) _d_eh_getExceptionInFlight();