[17.0.0] Backport fix fd_read and fd_write for wasm32-wasi-threads (#7750)#7755
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…ds` (bytecodealliance#7750) Previously, `first_non_empty_{c}io_vec` always returned `Ok(None)` for buffers residing in shared memories since they cannot, in general, safely be represented as slices. That caused e.g. `wasi-libc` to spin forever when trying to write to stdout using `fd_write` since it always got `Ok(0)` and never made progress. This commit changes the return type of both functions to use `GuestPtr` instead of `GuestSlice{Mut}`, allowing safe access to shared guest memory. Big thanks to Alex Crichton for narrowing this down and suggesting the fix. Signed-off-by: Joel Dice <joel.dice@fermyon.com>
alexcrichton
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Jan 5, 2024
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Previously,
first_non_empty_{c}io_vecalways returnedOk(None)for buffers residing in shared memories since they cannot, in general, safely be represented as slices. That caused e.g.wasi-libcto spin forever when trying to write to stdout usingfd_writesince it always gotOk(0)and never made progress.This commit changes the return type of both functions to use
GuestPtrinstead ofGuestSlice{Mut}, allowing safe access to shared guest memory.Big thanks to Alex Crichton for narrowing this down and suggesting the fix.