Function signature mismatch with pdfium.wasm i32 vs. i64

[mrboxtobox]

Hi,

I'm running into the following error when I try running pdfium.wasm with wasmtime. I'm running on MacOS M3. Any ideas what could be wrong?

    raise WasmtimeError._from_ptr(error)
wasmtime._error.WasmtimeError: incompatible import type for `wasi_snapshot_preview1::fd_seek`

Caused by:
    types incompatible: expected type `(func (param i32 i32 i32 i32 i32) (result i32))`, found type `(func (param i32 i64 i32 i32) (result i32))`

Steps to Reproduce

1. Install Deps

pip install wasmtime

2. Download and install pdfium-wasm

curl -L -O https://github.com/bblanchon/pdfium-binaries/releases/latest/download/pdfium-wasm.tgz
tar -xzvf pdfium-wasm.tgz

3. Run python test_wasm.py in the same directory

# test_wasm.py
from wasmtime import Engine, Store, Module, Linker, WasiConfig, FuncType, ValType
import ctypes
import os
import logging

# Set up logging
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

def define_unknown_imports_as_default_values(linker: Linker, module: Module) -> None:
    for imp in module.imports:
        if imp.module != "env":
            continue
        if isinstance(imp.type, FuncType):
            func_ty = imp.type
            result_tys = func_ty.results

            def default_func(*args):
                # XXX: For some reason _emscripten_throw_longjmp is called with different numbers of
                # arguments, and sometimes expects a return value and sometimes not. This feels like
                # a bug, but I don't know if it's in emscripten or wasmtime.
                if imp.name == "_emscripten_throw_longjmp":
                    if len(args) in (3, 5):
                        return 0
                    return None
                results = []
                for ty in result_tys:
                    match ty:
                        case ValType.i32():
                            results.append(0)
                        case ValType.i64():
                            results.append(0)
                        case ValType.f32():
                            results.append(0.0)
                        case ValType.f64():
                            results.append(0.0)
                return results

            linker.define_func(imp.module, imp.name, func_ty, default_func)


def main():
    # Path to your PDFium WASM file
    wasm_file = "lib/pdfium.wasm"

    import sys
    # Check if files exist
    if not os.path.exists(wasm_file):
        logger.error(f"WASM file not found: {wasm_file}")
        return


    # Create a store and engine
    engine = Engine()
    module = Module.from_file(engine, wasm_file)
    store = Store(engine)
    linker = Linker(engine)
    linker.define_wasi()
    wasi_config = WasiConfig()
    wasi_config.inherit_stdout()

    store.set_wasi(wasi_config)

    # Compile and instantiate the WASM module
    logger.info("Loading WASM module...")
    define_unknown_imports_as_default_values(linker, module)

    instance = linker.instantiate(store, module)

if __name__ == "__main__":
    main()