GeezerVison

…pythonGH-160398)

A raw read can reinitialize a TextIOWrapper as write-only, and codec callbacks or finalizers can release an encoder, decoder, or decoded chunk while a read or write still needs it. This can crash the interpreter. Check that a decoder is still available after reading, keep codecs alive across calls, and read the chunk length before transferring ownership. Also recheck StringIO after converting the truncate size because __index__() can close the stream.
(cherry picked from commit 665bda9)

Co-authored-by: Jelle Zijlstra <[email protected]>