[issue29640] _PyThreadState_Init and fork race leads to inconsistent key list

[STINNER Victor]

STINNER Victor <vstinner at redhat.com> added the comment:

> the old TLS API is only available if PTHREAD_KEY_T_IS_COMPATIBLE_WITH_INT.

PTHREAD_KEY_T_IS_COMPATIBLE_WITH_INT is defined on most (pthread) platforms, no? I understood that the PEP 539 is mostly designed for Cygwin, a platform which is not officially supported by Python. At least, PTHREAD_KEY_T_IS_COMPATIBLE_WITH_INT is set to 1 on my Fedora 27 (Linux).

I propose to cast pthread_key_create() result to int, but only define PyThread_create_key() in Python/thread_pthread.h if PTHREAD_KEY_T_IS_COMPATIBLE_WITH_INT is defined.

It means that the pthread implementation of Python would still have this bug (race condition) if PTHREAD_KEY_T_IS_COMPATIBLE_WITH_INT is not defined. But backporting the PEP 539 to Python 2.7 doesn't seem worth it.

What do you think?

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