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authorwolfbeast <mcwerewolf@gmail.com>2018-03-17 10:47:56 +0100
committerwolfbeast <mcwerewolf@gmail.com>2018-03-17 10:47:56 +0100
commit56bcb6b5af91696e2700b6477db2473b5921bce1 (patch)
treef3d1714b551641951b34d0126ec65164171a5612 /browser/modules
parente4c64e1a3dd007880ccd12a4273baae9b4380519 (diff)
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Handle same-compartment wrappers in TypedArray methods.
CallTypedArrayMethodIfWrapped (and the CallNonGeneric machinery throughout the engine) unwraps the `this` argument, but the other arguments are only rewrapped for the target compartment. The pattern being used before this patch to get the length of a TypedArray or possible TypedArray wrapper is: `callFunction(CallTypedArrayMethodIfWrapped, O, O, "TypedArrayLength")` The first `O` is the `this` value and the second is an argument. If `O` is a cross-compartment wrapper, this works fine. The first `O` is unwrapped, revealing the actual TypedArray object; the second `O` is rewrapped for that TypedArray's compartment, producing the same TypedArray. However, if `O` is a same-compartment wrapper, this doesn't work. The first `O` is unwrapped, revealing the actual TypedArray object in the same compartment; rewrapping the other `O` does nothing to it, since it is already an object in the target compartment. Thus TypedArrayLength receives a `this` value that's an unwrapped TypedArray, but an argument that is still a wrapper. The fix is to have CallTypedArrayMethodIfWrapped targets only expect `this` to be an unwrapped TypedArray.
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