Rethrow after access to the exnref parameters

[Horcrux7]

Is there a simple solution to rethrow an exception after access to the parameters of the exnref?

Currently the only solution seems to be:

• save the exception in a local variable
• push the exception on the stack
• pushes the exception's argument values on top of the stack with br_on_exn
• inspect the arguments
• rethrow depending the inspection result

Sounds not very efficient. I am also not clear if a rethrow is possible after a br_on_exn.

Background: I am working on a compiler for Java (JWebAssembly). The exception there are hierarchical. That I can not use the plain exception type of this spec. I use only one event type. In the parameters of exnref there are the hierarchical exception details.

[aheejin]

rethrow is possible after br_on_exn. And I think you're right that you need to save exnref (pushed onto the stack by catch) to a local to rethrow it again. This is not a problem specific to exnref; wasm is a stack machine, and if you want to use a value on top of the stack (pushed by any instruction) twice, you need to save it to a local, for any instruction.

[Horcrux7]

Thanks.