WASMFS OPFS not working with ASYNCIFY=1

[irfan2502]

Please include the following in your bug report:

Version of emscripten/emsdk:
clang version 19.0.0git (https:/github.com/llvm/llvm-project 7cfffe74eeb68fbb3fb9706ac7071f8caeeb6520)
Target: wasm32-unknown-emscripten
Thread model: posix

Failing command line in full:
NA

Full link command and output with -v appended:
emcc fs.cpp -o fs.html -sWASMFS -g -sASYNCIFY=1 -O3

I am trying to compile below code with ASYNCIFY=1. But, I am getting the error shown below. With JSPI (ASYNCIFY=2), the same code works perfectly. The same code works perfectly with -pthread -sPROXY_TO_PTHREAD option as well. It doesn't work only with ASYNCIFY=1

fs.js:50 Uncaught RuntimeError: unreachable
    at fs.wasm.(anonymous namespace)::OPFSDirectory::getChild(std::__2::basic_string<char, std::__2::char_traits<char>, std::__2::allocator<char>> const&) (http://localhost:2502/fs.wasm:wasm-function[1878]:0x51b36)
    at fs.wasm.wasmfs::Directory::Handle::getChild(std::__2::basic_string<char, std::__2::char_traits<char>, std::__2::allocator<char>> const&) (http://localhost:2502/fs.wasm:wasm-function[1986]:0x57a06)
    at fs.wasm.doOpen(wasmfs::path::ParsedParent, int, unsigned int, wasmfs::Backend*, OpenReturnMode) (http://localhost:2502/fs.wasm:wasm-function[2032]:0x60f8b)
    at fs.wasm.__syscall_openat (http://localhost:2502/fs.wasm:wasm-function[2038]:0x626f8)
    at fs.wasm.fopen (http://localhost:2502/fs.wasm:wasm-function[93]:0x622d)
    at fs.wasm.std::__2::basic_filebuf<char, std::__2::char_traits<char>>::open(char const*, unsigned int) (http://localhost:2502/fs.wasm:wasm-function[281]:0xbe26)
    at fs.wasm.__original_main (http://localhost:2502/fs.wasm:wasm-function[43]:0x1a33)
    at fs.wasm.main (http://localhost:2502/fs.wasm:wasm-function[49]:0x2a00)
    at ret.<computed> (http://localhost:2502/fs.js:1994:24)
    at Module._main (http://localhost:2502/fs.js:2275:90)

#include <iostream>
#include <fstream>

#include <emscripten/wasmfs.h>

int main() {
    try {
        backend_t opfs = wasmfs_create_opfs_backend();
        std::cout << "created OPFS backend\n";

        auto err = wasmfs_create_directory("/opfs", 0777, opfs);
        std::cout << "mounted OPFS root directory with error code " << err << "\n";

        // File path to write in OPFS
        std::string path = "/opfs/example.txt";

        std::ofstream outfile(path);
        outfile << "Sample content" << std::endl;
        outfile.close();

        // Read the file
        std::ifstream infile(path);
        std::string content((std::istreambuf_iterator<char>(infile)),
                            std::istreambuf_iterator<char>());
        std::cout << "File content: " << content << std::endl;
        
    } catch (const std::exception& e) {
        std::cerr << "Error: " << e.what() << std::endl;
    }

    return 0;
}

[irfan2502]

@sbc100 Can you help on this?

[sbc100]

@tlively ?

[tlively]

IIRC, we support JSPI but not plain ASYNCIFY in WasmFS. Maybe we can either fix that or have a more useful error message? cc @brendandahl