Memory resizing race

[jfbastien]

WebAssembly supports growing the memory's size, and obtaining its current size:
https://github.com/WebAssembly/design/blob/56e617e8144a8b750a1198871eb6d43fad182c21/AstSemantics.md#resizing

• Many of the spec's algorithms check that accesses are in-range. What happens if one of the algorithms is executing while a resize operation occurs?
• What happens if memory is resized during an access?

I assume all threads need to be suspended for a resize operation.

[lars-t-hansen]

Resizing memory is definitely outside of scope for current work, though these are interesting points (also see #59 for other wasm discussion).

[lars-t-hansen]

The wasm threads spec is now addressing this. I don't think thread suspension during resizing is required there (because a maximum size is always needed and memory will generally be preallocated, or pre-reserved); rather, it seems that a new SAB object is allocated with a larger length field, so operations on the memory will see the old or new SAB. In either case, we'll move the discussion over there.