Greg Ewing, 29.11.2009 01:27:
> Robert Bradshaw wrote:
>
>> I'm not sure. It depends on if it's just the idea of a "system default
>> encoding" that's deprecated, or if the slot containing a encoded
>> reference is going away.
>
> My reading of it is that the slot is still there and still
> supported, but that it always contains utf8, and the right
> way to access it is via PyString_AsUTF8String().
Ok, there is no PyString_AsUTF8String, so I assume you meant
PyUnicode_AsUTF8String, but that doesn't use defenc at all. There is an
internal function _PyUnicode_AsDefaultEncodedString(), about which the
header file clearly says "Exported for internal use by the interpreter only".
Reading the PyUnicodeObject header:
----------
PyObject *defenc; /* (Default) Encoded version as Python
string, or NULL; this is used for
implementing the buffer protocol */
----------
So my reading of the docs is that defenc is purely an implementation
detail. Assuming that we can happily depend on its value to keep the char*
around, or that it will do no harm to just keep a dangling reference during
the lifetime of a function (or module) sounds fragile to me. Think of this
code:
cdef unicode u = "abcdefg"
cdef char* s = u
u = None
print s
Now, where's the reference to the string buffer now? Would this work
because Cython keeps the reference alive for all eternity, or would this
fail because Cython deletes the reference immediately after taking the
char* from it? Or would Cython see the "u = None" and discard the encoded
string at the same time? Or would we use the buffer interface on the
unicode string internally, although the syntax doesn't resemble the buffer
syntax at all? And why should this only work in Py3, what would you do in Py2?
In any case, it's totally non-obvious how the above would behave, so I'm
-100 on letting char* refer to an encoded version of the unicode string it
was taken from.
Stefan
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