In Python 3.3, PyThread_set_key_value() did nothing if the key already exists
(if the current value is a non-NULL pointer).
When _PyGILState_NoteThreadState() is called twice on the same thread with a
different Python thread state, it still keeps the old Python thread state to
keep the old behaviour. Replacing the Python thread state with the new state
introduces new bugs: see issues #10915 and #15751.
the function did nothing if the key already exists (if the current value is a
non-NULL pointer).
_testcapi.run_in_subinterp() now correctly sets the new Python thread state of
the current thread when a subinterpreter is created.
between tracemalloc_remove_trace() and tracemalloc_add_trace() to reduce the
risk of race condition.
tracemalloc_add_trace() cannot fail anymore in tracemalloc_realloc() when
tracemalloc_realloc() resizes a memory block.
PyGILState_Ensure()/PyGILState_Release() calls to the raw wrappers to simplify
the code.
Rename also tracemalloc_log_alloc/log_free() to
tracemalloc_add_trace/remove_trace().
The limit is now 178,956,969 on 64 bit (it is greater on 32 bit because
structures are smaller).
Use int instead of Py_ssize_t to store the number of frames to have smaller
traceback_t objects.
Victor Stinner