[issue25862] TextIOWrapper assertion failure after read() and SEEK_CUR

[Martin Panter]

New submission from Martin Panter:

Python 3.5.1+ (3.5:014e6f7d7c1a, Dec 14 2015, 11:20:58) 
[GCC 5.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from io import *
>>> text = TextIOWrapper(BytesIO(b"x"), "ascii")
>>> text.read(1)
'x'
>>> text.read()
''
>>> text.seek(0, SEEK_CUR)
python: ./Modules/_io/textio.c:2293: _io_TextIOWrapper_tell_impl: Assertion `self->decoded_chars == ((void *)0) || PyUnicode_GetLength(self->decoded_chars) == 0' failed.
Aborted (core dumped)
[Exit 134]

May affect other versions; I haven’t looked.

----------
components: IO
messages: 256430
nosy: martin.panter
priority: normal
severity: normal
status: open
title: TextIOWrapper assertion failure after read() and SEEK_CUR
type: crash
versions: Python 3.5

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue25862>
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