[Python-Dev] Changing string constants to byte arrays ([Python-checkins] r55119 - in python/branches/py3k-struni/Lib: codecs.py test/test_codecs.py)

Walter Dörwald walter at livinglogic.de
Fri May 4 16:29:15 CEST 2007

M.-A. Lemburg wrote:

> Hi Walter,
> if the bytes type does turn out to be a mutable type as suggested
> in PEP 358,

it is.

> then please make sure that no code (C code in
> particular), relies on the constantness of these byte objects.
> This is especially important when it comes to codecs, since
> the error callback logic would allow the callback to manipulate
> the byte object contents and length without the codec taking
> note of this change.

Encoding is not a problem because the error callback never sees or
returns a byte object.

However decoding is a problem. After the callback returns the codec has
to recalculate it's variables.

> I expect there to be other places in the interpreter which would
> break as well.
> Otherwise, you end up opening the door for segfaults and
> easy DOS attacks on Python3.

True, registering an even callback could crash the interpreter.

Seems we have to update all decoding functions.


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