SharedArrayBuffer changes in Chrome 91+

[Richienb]

In Chrome 91+, a SharedArrayBuffer can only be created if cross-origin isolation is enabled.

Affected part:

node-util/support/types.js

Line 243 in 4b1c0c7

isSharedArrayBufferToString(new SharedArrayBuffer())

A possible fix could be falling back to ArrayBuffer if window.crossOriginIsolated !== true.

Related to Richienb/node-polyfill-webpack-plugin#4

[ljharb]

If it's not enabled, then isn't typeof SharedArrayBuffer going to be undefined, which would mean the preceding line would cause it to return false?

[Richienb]

Oh right. In that case, the script is already prepared to work in an environment where SharedArrayBuffer is unavailable.

[daewigma]

@ljharb Out of curiosity, is there documentation somewhere that says the cross origin isolation restriction will be implemented by making the constructor undefined as opposed to throwing an error when attempting to use it?

Making it undefined would make sense to do if assuming people have their apps built with backwards/cross-platform compatibility in mind, but I could also see providing the constructor and having it throw an error, as it would make it much more clear what happened to it when code suddenly starts failing.

A lot of places detailing fixing this issue recommend either stopping use of SharedArrayBuffer altogether, or checking window.crossOriginIsolated before using it. I'm not sure if this is because the constructor will just throw an error, they didn't know that SharedArrayBuffer will be undefined, they are wanting to get rid of the deprecation warnings in the meantime, or some other reason I'm not thinking of.

[ljharb]

@daewigma yep: tc39/ecma262#1435