Erik Bray writes:
> Abstract
> ========
>
> The proposal is to add a new Thread Local Storage (TLS) API to CPython
> which would supersede use of the existing TLS API within the CPython
> interpreter, while deprecating the existing API.
Thank you for the analysis!
Question:
> Further, the old PyThread_*_key* functions will be marked as
> deprecated.
Of course, but:
> Additionally, the pthread implementations of the old
> PyThread_*_key* functions will either fail or be no-ops on
> platforms where sizeof(pythead_t) != sizeof(int).
Typo "pythead_t" in last line.
I don't understand this. I assume that there are no such platforms
supported at present. I would think that when such a platform becomes
supported, code supporting "key" functions becomes unsupportable
without #ifdefs on that platform, at least directly. So you should
either (1) raise UnimplementedError, or (2) provide the API as a
wrapper over the new API by making the integer keys indexes into a
table of TSS'es, or some such device. I don't understand how (3)
"make it a no-op" can be implemented for PyThread_create_key -- return
0 or -1? That would only work if there's a failure return status like
0 or -1, and it seems really dangerous to me since in general a lot of
code doesn't check status even though it should. Even for code
checking the status, the error message will be suboptimal ("creation
failed" vs. "unimplemented").
I gather from references to casting pthread_key_t to unsigned int and
back that there's probably code that does this in ways making (2) too
dangerous to support. If true, perhaps that should be mentioned here.
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