MEMORY64 and internal JS functions not working with BigInt

[cwoffenden]

This is with the latest Emscripten 4.0.1.

Is there a plan for JS functions like stackAlloc and UTF8ToString that expect or return Numbers and not a BigInt.

As an example, passing a 64-bit pointer to UTF8ToString fails the assert:

emscripten/src/lib/libstrings.js

Line 118 in 2bc4461

$UTF8ToString: (ptr, maxBytesToRead) => {

It can be fudged for 4GB address with something like:

ptr = Number(BigInt.asUintN(32, url));

I came across this and others adding MEMORY64 support to audio worklets (currently a bunch of workarounds but it's running and playing audio with a 4GB heap). Is there a plan for these internal functions?

[cwoffenden]

A small repro case is:

#include <emscripten/em_js.h>

EM_JS(void, stringTest, (const char* str), {
    console.log(UTF8ToString(str));
});

int main() {
    stringTest("Test");
}

Compile with:

emcc -sASSERTIONS=2 -sMEMORY64 -sEXPORTED_RUNTIME_METHODS=UTF8ToString string_test.c

The error given is:

Uncaught RuntimeError: Aborted(Assertion failed: UTF8ToString expects a number (got bigint))

[brendandahl]

EM_JS does not currently automatically convert BigInts to numbers (like library js functions). There's a similar issue filed about this for the return values #16975.

[brendandahl]

The better issue to link to is #23325. Which has been marked as a duplicate of the above.