Plan for Exceptions and @nogc?

[Matthias Bentrup via Digitalmars-d]

On Tuesday, 17 February 2015 at 17:38:20 UTC, Jonathan Marler 
wrote:
> The reason you can't keep the "thrower's" stack memory around 
> for the exception handler is because the exception handler may 
> need that memory.  Once the exception is thrown the stack is 
> unwound to the function that has the exception handler so all 
> the memory gets released. In most cases the exception handler 
> probably won't mess up the memory the exception is using, but 
> that can't be guaranteed.
>

The problem I see, is that if I program a @nogc function for 
performance reasons, I'll likely have some data in scoped memory 
that is useful for handling the exception. If the stack is 
unwound before the exception handler, the thrower has to copy it 
to non-scoped memory and the catcher has to deal with it whether 
it needs the data or not.

If the unwinding is done after the exception handler is left, the 
thrower can safely reference the data directly on the stack and 
the catcher can ignore any data it doesn't need. (It may copy the 
data to safety if it is needed later, but the catcher knows what 
it needs, whereas the thrower has to always assume the worst 
case.)