[New-bugs-announce] [issue34481] Different behavior of C and Python impls of datetime.strftime with non-UTF-8-encodable strings

[Alexey Izbyshev]

New submission from Alexey Izbyshev <izbyshev at ispras.ru>:

The C datetime implementation uses PyUnicode_AsUTF8AndSize() in wrap_strftime() and rejects strings containing surrogate code points (0xD800 - 0xDFFF) since they can't be encoded in UTF-8. On the other hand, the pure-Python datetime implementation doesn't have this restriction:

>>> import sys
>>> sys.modules['_datetime'] = None # block C implementation
>>> from datetime import time
>>> time().strftime('\ud800')
'\ud800'
>>> del sys.modules['datetime']
>>> del sys.modules['_datetime']
>>> from datetime import time
>>> time().strftime('\ud800')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeEncodeError: 'utf-8' codec can't encode character '\ud800' in position 0: surrogates not allowed

----------
components: Extension Modules
messages: 323963
nosy: belopolsky, izbyshev, pitrou, serhiy.storchaka, taleinat
priority: normal
severity: normal
status: open
title: Different behavior of C and Python impls of datetime.strftime with non-UTF-8-encodable strings
type: behavior
versions: Python 3.6, Python 3.7, Python 3.8

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue34481>
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