Memory views in strict mode

[peterhirn]

Hi,

why are memory views not exposed in strict mode? (see https://github.com/emscripten-core/emscripten/blob/main/src/runtime_shared.js#L12)

Is it considered bad practice to access the memory views directly?

It would be great if this behavior could be documented here https://emscripten.org/docs/tools_reference/settings_reference.html#strict.

[sbc100]

In strict mode, for code size reasons, we only export what you ask for. You can export a given heap by adding it to -sEXPORTED_RUNTIME_METHODS.

See #21439

I debug builds I believe you should see an informative error if you try to access a heap that you didn't export. e.g.:

$ cat test.c 
#include <emscripten/emscripten.h>

int main() {
  EM_ASM(Module["HEAPF32"][100] = 0.1);
}
$ emcc test.c -sSTRICT
$ node ./a.out.js 
Aborted('HEAPF32' was not exported. add it to EXPORTED_RUNTIME_METHODS (see the Emscripten FAQ))
/usr/local/google/home/sbc/dev/wasm/emscripten/a.out.js:547
  var e = new WebAssembly.RuntimeError(what);
          ^

RuntimeError: Aborted('HEAPF32' was not exported. add it to EXPORTED_RUNTIME_METHODS (see the Emscripten FAQ))
    at abort (/usr/local/google/home/sbc/dev/wasm/emscripten/a.out.js:547:11)
    at Object.get (/usr/local/google/home/sbc/dev/wasm/emscripten/a.out.js:844:9)
    at 65536 (/usr/local/google/home/sbc/dev/wasm/emscripten/a.out.js:860:24)
    at runEmAsmFunction (/usr/local/google/home/sbc/dev/wasm/emscripten/a.out.js:976:30)
    at _emscripten_asm_const_int (/usr/local/google/home/sbc/dev/wasm/emscripten/a.out.js:979:14)
    at wasm://wasm/de9e8a5e:wasm-function[2]:0x223
    at wasm://wasm/de9e8a5e:wasm-function[3]:0x241
    at /usr/local/google/home/sbc/dev/wasm/emscripten/a.out.js:599:12
    at callMain (/usr/local/google/home/sbc/dev/wasm/emscripten/a.out.js:1367:15)
    at doRun (/usr/local/google/home/sbc/dev/wasm/emscripten/a.out.js:1415:23)

Node.js v18.20.3

Did this messsage not show up for you?

[peterhirn]

Nice, thank you! I didn't realize that the memory views could be configured using EXPORTED_RUNTIME_METHODS.

-sEXPORTED_RUNTIME_METHODS=UTF8ToString,HEAPU8