On Sat, May 8, 2010 at 10:16 AM, Marc-Andre Lemburg
<report@bugs.python.org> wrote:
> Are you sure this doesn't get optimized away in practice ?

I'm sure it doesn't get optimized away by gcc 4.3, where I tested it. :)

> Sure, though, I don't see how this relates to C code relying
> on these details, e.g. a C extension will probably use different
> conversion code depending on whether UCS2 or UCS4 is compatible
> with some external library, etc.

Can you give an example?

All of the examples I can think of either:
- poke into PyUnicodeObject's internals,
- call a Python function that exposes Py_UNICODE or PyUnicodeObject

I'm explicitly trying to protect those two cases.  It's quite possible
that I'm missing something, but I can't think of any other unsafe way
for a C extension to convert a Python Unicode object to a byte string.