Unlike the exit code of other runtime tools, the result shows that "Pointer not aligned to 4"

[gaaraw]

Phenomenon description

Hello, when I use multiple runtime tools in the terminal, I notice different behavior for the same wasm program. The specific performance is as follows:

wasmtime:
Output：

Error: failed to run main module `work.wasm`

Caused by:
    0: failed to invoke command default
    1: error while executing at wasm backtrace:
           0:     0xd8 - <unknown>!<wasm function 4>
           1:     0xb6 - <unknown>!<wasm function 3>
    2: Pointer not aligned to 4: Region { start: 1, len: 4 }

exit code: 1

wasmer / wasmedge / wamr:
No output
exit code: 0

Test Case

test_case.zip

Steps to Reproduce

# run wasm file
/path/to/wasmtime test_case.wasm
/path/to/wasmer run test_case.wasm
/path/to/wasmedge --enable-jit test_case.wasm
/path/to/iwasm test_case.wasm

Versions and Environment

The runtime tools are all built on release and use JIT mode.

• wasmtime: 35.0.0 (9c2e6f1 2025-06-17)
• wasmer: 6.0.1
• wasmedge: 0.14.1
• WAMR: iwasm 2.4.0
• Host OS: Ubuntu 22.04.5 LTS x64
• CPU: 11th Gen Intel® Core™ i7-11700 @ 2.50GHz × 16

Extra Info

If you need any other relevant information, please let me know and I will do my best to provide it. Looking forward to your reply! Thank you!

[bjorn3]

Wasmer, wasmedge and wamr are probably just more lenient around unaligned pointers. Wasmtime does check that pointers passed to wasi that should be aligned are actually aligned.

[gaaraw]

So the reason is that other runtime tools don't strictly do alignment checks. Is this kind of leniency of them allowed?

[bjorn3]

wasip1 doesn't have a good specification, so whether or not it is allowed to not check for alignment is kind of undefined I think.

[alexcrichton]

Yes as @bjorn3 mentioned this is expected behavior. If you're fuzzing WASIp1 we recommend not doing so