Andre-LA commented 1 year ago

Hello, I'm trying to run Cyber on the web using emscripten (because of the SDL2 port), however, I getting an runtime error on the process.

Environment

Tested on Fedora Linux 37.
Zig version: 0.11.0-dev.1797+d3c9bfada (as described on build documentation).
Cyber version: 9930caa
Emscripten version: at commit a2ccccba58918706f815d806460d09310fe236d9.

Steps to reproduce

Download the zig 0.11-dev compiler and clone cyber repository as described on build documentation.
Build the wasm library as described on building documentation.
Download and setup emscripten as described on emscripten documentation.
Archive the cyber.wasm.o file using the command emar -rcs libcyber.a zig-out/lib/cyber.wasm.o.
Create the C file with the code below, it's adapted from examples/c-embedded/main.c.
Create the build directory, just for organization.
Compile main.c with emcc with the command emcc main.c ./libcyber.a -I./src/ -L. -o build/main.html
Run it with cd build/ && emrun main.html.

Expected behaviour

The expected behaviour would be seeing this message on the page's console:

creating Cyber VM
Cyber VM created
2
Success!

Observed behaviour

An exception it's thrown, with a stack trace available on the browser's console, on the page's console only creating Cyber VM it's shown, which means that the problem happens on cyVmCreate function call.

Testing code

main.c:

#include <stdio.h>
#include "cyber.h"

// host functions
void hostFetchUrl(const char *url, size_t urlLen) {}
void hostEvalJS(const char *ptr, size_t len) {}
void hostSleep(uint64_t secs, uint64_t nsecs) {}
void hostLogDebug(const char *ptr, size_t len) {}
void hostLogInfo(const char *ptr, size_t len) {}
void hostLogWarn(const char *ptr, size_t len) {}
void hostLogError(const char *ptr, size_t len) {}
double hostMilliTimestamp() {
    return 0.016;
}
void hostFileWrite(uint32_t fid, const char* str, size_t strLen) {
    printf("%s", str);
}

int main(void) {
    printf("creating Cyber VM\n");
    CyVM* vm = cyVmCreate();
    printf("Cyber VM created\n");
    CStr src = cstr(
        "a = 2\n"
        "print a"
    );
    CyValue val;
    int res = cyVmEval(vm, src, &val);
    if (res == CY_Success) {
        printf("Success!\n");
        cyVmRelease(vm, val);
    } else {
        CStr err = cyVmGetLastErrorReport(vm);
        printf("%s\n", err.charz);
    }
    cyVmDestroy(vm);
    return 0;
}

Extra note

The code above works with wasmtime, when using the wasi-sdk with the same cyber build, with (almost) same building steps.

fubark commented 1 year ago

As discussed on Discord, the issue is that Emscripten manages it's own memory while the library is compiled with it's own allocator. If this https://github.com/fubark/cyber/blob/15df569aaeb54d33590854c56fa44826769191b3/src/lib.zig#L32 is changed to alloc = std.heap.c_allocator; it should work. I guess we can also add a build option for this too.