br comparison type mismatch?

[johannesvollmer]

https://github.com/WebAssembly/testsuite/blob/596a817f96bc6fb74a90794473604a0587acc585/br.wast#L272-L280

The comparison operation is called with one operand and operands of different types. Is this allowed? Shouldn't this fail validation? Doesn't validate in my local node engine.

[dschuff]

The br instruction (and other unconditional control transfers) is stack-polymorphic, meaning that for validation purposes it leaves the stack in an "unconstrained" state, such that any type can be consumed from it. So these tests are basically checking that property, that the instruction validates when various different types are required by the comparison instructions.
So yes, this should pass validation (and both this test and node's implementation have done so since wasm's MVP); if your local system is failing this, there must be some sort of bigger problem.

[johannesvollmer]

Hi, thanks for your answer :) I think I understand.

This was there from the start, so the node version should not matter, right?

Wait, I think I made a mistake, it might not be node but it's wabt js which is failing to validate that in my setup

[dschuff]

Yeah, any engine that has ever had complete support for any version of wasm should get this right. There of course can be bugs, those should be filed in the usual way (wabt bugs go to https://github.com/WebAssembly/wabt/issues).

[sunfishcode]

The question here is answered.