_free function sometimes throws memory access errors

[svenoaks]

Depending on what happens before, freeing memory can cause

wasm-001654a2-26:1 Uncaught (in promise) RuntimeError: memory access out of bounds
    at wasm-function[26]:0xb03
    at Object.Module._free (http://localhost:63343/MusicSpeedChangerWeb/superpowered-no-module.js:8:557177)
    at start (http://localhost:63343/MusicSpeedChangerWeb/file-saving-worker.js:163:22)
    at Object.onReady (http://localhost:63343/MusicSpeedChangerWeb/file-saving-worker.js:7:24)
    at Object.Module.onRuntimeInitialized (http://localhost:63343/MusicSpeedChangerWeb/superpowered-no-module.js:8:2531)
    at doRun (http://localhost:63343/MusicSpeedChangerWeb/superpowered-no-module.js:8:563492)
    at run (http://localhost:63343/MusicSpeedChangerWeb/superpowered-no-module.js:8:563652)
    at runCaller (http://localhost:63343/MusicSpeedChangerWeb/superpowered-no-module.js:8:563176)
    at removeRunDependency (http://localhost:63343/MusicSpeedChangerWeb/superpowered-no-module.js:8:19887)
    at receiveInstance (http://localhost:63343/MusicSpeedChangerWeb/superpowered-no-module.js:8:508939)

This is from memory allocated with:

let timeStretching = Superpowered.new('TimeStretching', samplerate, 0.25, 1);
let pcm = Superpowered.createFloatArray(blockSizeFrames * 8);
        let outputBuffer = Superpowered.createFloatArray(blockSizeFrames * 2);

        let pointerL = Superpowered._malloc(blockSizeFrames * 2);
        let pointerR = Superpowered._malloc(blockSizeFrames * 2);

        let leftInts = new Int16Array(
            Superpowered.HEAP16.buffer,
            pointerL,
            blockSizeFrames
        );

        let rightInts = new Int16Array(
            Superpowered.HEAP16.buffer,
            pointerR,
            blockSizeFrames
        );

        let floatL = Superpowered.createFloatArray(blockSizeFrames);
        let floatR = Superpowered.createFloatArray(blockSizeFrames);

and then freed after use:

Superpowered.destroyFloatArray(pcm);
        Superpowered.destroyFloatArray(outputBuffer);
        Superpowered._free(pointerL);
        Superpowered._free(pointerR);
        Superpowered.destroyFloatArray(floatL);
        Superpowered.destroyFloatArray(floatR);
        timeStretching.destruct();

When I introduced a library (https://github.com/egoroof/browser-id3-writer) for writing mp3 tags is when the errors starting happening with some files on Superpowered._free(pointerR);.

[gaborszanto]

Maybe that library calls a "grow" on the linear memory, making all pointers invalid.