wasm-tools smith generates infinite loops

[yamt]

i'm using the following to generate a wasm module.

    dd if=/dev/urandom bs=10240 count=100 2> /dev/null | wasm-tools smith \
    --max-imports=0 \
    --ensure-termination \
    --fuel=100 \
    --maybe-invalid \
    --reference-types-enabled=true \
    --simd-enabled=true \
    -o test.wasm

my expectation was that with --ensure-termination, it doesn't generate infinite loops.
however, it sometimes does.
i will attach a sample of a generated file, which loops infinitely.

test.zip

it's with wasm-tools 1.0.55.

[fitzgen]

Can you attach the input bytes that were given to wasm-smith such that it created a Wasm module that has infinite loops? Thanks!

[alexcrichton]

Oh I believe this is the combination of --ensure-termination and --maybe-invalid as you can see in the smith subcommand. With --maybe-invalid the --ensure-termination option doesn't work because it only works if wasm-smith is generating all the bytecode itself.

Definitely something we should improve by erroring out if both options are passed.

[alexcrichton]

I've changed how things are organized in #1411 and an example error looks like:

$ head -c 1000 /dev/urandom | tee input.bin | cargo run smith --allow-invalid-funcs true -t --ensure-termination
    Finished dev [unoptimized + debuginfo] target(s) in 0.05s
     Running `target/debug/wasm-tools smith --allow-invalid-funcs true -t --ensure-termination`
error: failed to ensure module always terminates, `--ensure-termination` is incompatible with `--allow-invalid-funcs`

Caused by:
    0: failed to ensure that a function generated due to it containing arbitrary instructions

with input.bin.gz as the input