[Python-3000] uuid creation not thread-safe?

[Guido van Rossum]

I discovered what appears to be a thread-unsafety in uuid.py. This is
in the trunk as well as in 3.x; I'm using the trunk here for easy
reference. There's some code around like 395:

    import ctypes, ctypes.util
    _buffer = ctypes.create_string_buffer(16)

This creates a *global* buffer which is used as the output parameter
to later calls to _uuid_generate_random() and _uuid_generate_time().
For example, around line 481, in uuid1():

        _uuid_generate_time(_buffer)
        return UUID(bytes=_buffer.raw)

Clearly if two threads do this simultaneously they are overwriting
_buffer in unpredictable order. There are a few other occurrences of
this too.

I find it somewhat disturbing that what seems a fairly innocent
function that doesn't *appear* to have global state is nevertheless
not thread-safe. Would it be wise to fix this, e.g. by allocating a
fresh output buffer inside uuid1() and other callers?

-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)