stack pointer undeflow when tracing host call

[ecioppettini]

This wasm program:

(module
  (import "host" "call" (func $f (param i32)))
  (memory 1)
  (func $test
    (i32.const 42)
    call $f
  )
  (export "test" (func $test))
)

Causes this panic

index out of bounds: the len is 8320 but the index is 18446744073709551615

At zkEngine_dev/src/wasm_snark/mcc/multiset_ops.rs:407:26

With a host call that does nothing:

        linker
            .func_wrap("host", "call", |caller: Caller<()>, i: u32| {})
            .unwrap();

The overflow seems to originate in the tracer here: https://github.com/ICME-Lab/zkEngine_dev/blob/6e8d49cb74df4356f36704d54dfe053db1397810/third-party/wasmi/crates/wasmi/src/engine/stack/mod.rs#L326C1-L332C1

I think most likely the problem is that the range in the loop should be instead: 1..=len_outputs

For example, in this case the host call doesn't have any outputs, so the post_sp is just 0. But because it has an input, max_inout is 1, introducing the underflow.

There is also however another one in the following if block:

zkEngine_dev/third-party/wasmi/crates/wasmi/src/engine/stack/mod.rs

Line 336 in 6e8d49c

vm.pre_sp = post_sp - 1;

And I'm not sure what that one is for, or what should be the correct value in there.