PyBytesWriter_GetData should mention that PyBytesWriter_Resize can also invalidate the returned pointer

[cdhowie]

Documentation

See relevant discussion on PyO3/pyo3#5906 and the discussion linked from that.

PyBytesWriter_Resize may need to reallocate the buffer to grow it. If this happens, any pointer previously returned by PyBytesWriter_GetData will be invalidated, but this is not documented -- only PyBytesWriter_Finish and PyBytesWriter_Discard are documented to invalidate previous data pointers.

I am happy to submit a PR for this issue if that would be helpful. (I assume I only need to modify Doc/c-api/bytes.rst?)

[sergey-miryanov]

cc @vstinner

[vstinner]

I am happy to submit a PR for this issue if that would be helpful. (I assume I only need to modify Doc/c-api/bytes.rst?)

Go ahead. In fact, many PyBytesWriter functions can invalidate the data pointer. Any function calling PyBytesWriter_Resize():

• PyBytesWriter_Grow()
• PyBytesWriter_GrowAndUpdatePointer()
• PyBytesWriter_WriteBytes()
• PyBytesWriter_Format()

You may just say:

   The pointer is valid until a :c:type:`PyBytesWriter` function is called on
   *writer*.

[vstinner]

(I assume I only need to modify Doc/c-api/bytes.rst?)

Correct.