TextDecoderWrapper doesn't always work

[Dan C]

Hi everyone,

In TextDecoderWrapper.decode, we currently have a checking whether the input buffer is an SharedArrayBuffer. After heap size is increased from INITIAL_MEMORY, "data.buffer instanceof SharedArrayBuffer" can evaluate to false when data is a view of the SharedArrayBuffer of the heap. I suspect this is because the new SharedArrayBuffer was created in a different thread.

Thanks,

Dan

[Alon Zakai]

Very strange. In that case, what is the type of data.buffer?

The main SharedArrayBuffer is always created in the main thread during startup. Later growth does not create a new SAB in another thread, it just grows it, and it updates the views in each thread using updateGlobalBufferAndViews. Regardless, the buffer of those views must always be an SAB - if somehow it is just an AB, that would be a serious browser bug (which is possible, of course).

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[Dan C]

The type of data.buffer is still SharedArrayBuffer, but "data.buffer instanceof SharedArrayBuffer" is false. Browser is Chrome 91.

P.S. I can't reproduce the issue today after update Chrome to 91.0.4472.124 in Windows.