On Saturday, 1 April 2017 at 13:34:58 UTC, Andrei Alexandrescu
wrote:
Walter and I discussed the following promising setup:
Use "throw new scope Exception" from @nogc code. That will
cause the exception to be allocated in a special stack-like
region.
If the catching code uses "catch (scope Exception obj)", then a
reference to the exception thus created will be passed to
catch. At the end of the catch block there's no outstanding
reference to "obj" so it will be freed. All @nogc code must use
this form of catch.
If the catching code uses "catch (Exception obj)", the
exception is cloned on the gc heap and then freed.
Finally, if an exception is thrown with "throw new Exception"
it can be caught with "catch (scope Exception obj)" by copying
the exception from the heap into the special region, and then
freeing the exception on the heap.
Such a scheme preserves backward compatibility and leverages
the work done on "scope".
Andrei
(currently using @nogc exceptions with malloc+emplace and
destroy+free)
OK. The important bit imho is that exception don't become special
class objects.
ie. "scope new" is not specific to exceptions.
The other @nogc blocker is .destroy
