Incorrect start function signature validation

[Q1IQ]

Subject of the issue

iwasm incorrectly reports '_start function signature is wrong' error when loading WebAssembly modules that should execute normally. The module contains a valid _start function but the engine fails to recognize the correct signature, preventing proper execution.

Test case

positive_1.wasm.txt

Your environment

• OS: Ubuntu 20.04
• CPU: amd64
• WAMR version: iwasm 2.2.0
• Commands:

iwasm --interp -f main ./program.wasm

Actual behavior

WASM module load failed: the signature of builtin _start function is wrong

Expected State

The module should load and execute successfully, outputting the expected result:

42

[lum1n0us]

It actually is not an issue, and here are the reasons:

• The signature verification of _start is specifically targeting wasm32-wasi. They are built using wasi-sdk toolchains (such as /opt/wasi-sdk-25.0-x86_64-linux/bin/clang -o hello.wasm ./main.c). For any wasm32-wasi, there will be an (export "_start" (func $_start)) serving as the entry point for execution. The signature of this _start should be void _start(void). Reference

• Considering wasi-sdk is the most popular toolchain in the wasm community, the iwasm release binary supports wasm32-wasi by default. This means the iwasm binary always assumes .wasm files are wasm32-wasi. However, you can change this behavior by recompiling from source code with different compilation options.

• The uploaded positive_1.wasm is not wasm32-wasi. You might want to run it with an iwasm build configured with -DWAMR_BUILD_LIBC_BUILTIN=1 -DWAMR_BUILD_LIBC_WASI=0.

[yamt]

You might want to run it with an iwasm build configured with -DWAMR_BUILD_LIBC_BUILTIN=1 -DWAMR_BUILD_LIBC_WASI=0.

while i agree it isn't a bug, i tend to think it would be more user-friendly if we don't require flipping build-time options to run non wasi modules.