[Updated] D12627: worker: adapt _blockingreader to work around a python3.8.[0-1] bug (issue6444)

[mjacob (Manuel Jacob)]

This revision now requires changes to proceed.
mjacob added inline comments.
mjacob requested changes to this revision.

INLINE COMMENTS

> worker.py:86
> +                data = self._wrapped.readall()
> +                b[:] = data
> +                return len(data)

This could change the size of `b`, which shouldn’t be done.

If pickle calls `readinto()` (e.g. on my machine, this happens when the pickled data contains a bytestring >= 2**16 bytes long), it passes a memoryview which doesn’t allow changing its size. Because the size of `b` is the size of the pickled object and `readall()` returns all bytes in the stream, containing the bytes for the pickled object + at least one trailing byte, this line would always raise a “ValueError: memoryview assignment: lvalue and rvalue have different structures” exception.

What I suggest instead is to mostly copy-paste the implementation of `read()` and modify it such that it reads into the provided buffer instead of creating one.

REPOSITORY
  rHG Mercurial

CHANGES SINCE LAST ACTION
  https://phab.mercurial-scm.org/D12627/new/

REVISION DETAIL
  https://phab.mercurial-scm.org/D12627

To: mharbison72, #hg-reviewers, mjacob
Cc: mjacob, mercurial-patches
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