Fix Test_Pep523AllowSpecialization tests of test_capi.test_misc.
On Cygwin, _PyEval_EvalFrameDefault in _testinternalcapi is not the
same as _PyEval_EvalFrameDefault in python.exe. So pass NULL
explicitly to use the default function (_PyEval_EvalFrameDefault).
Use exact remote reads for interpreter state, thread state, and
interpreter frame structs instead of pulling full remote pages into the
profiler page cache. This matches the core change from
python/cpython#149585.
The profiler clears the page cache between samples, so live entries are
always packed at the front. Track the live count and only clear/search
that prefix instead of scanning all 1024 slots on the hot path.
Use the frame cache to predict the next thread state and top frame
address, then batch interpreter/thread/frame reads with process_vm_readv
when profiling a Linux target. Reuse prefetched frame buffers in the
frame walker when the prediction is valid.
Cache the last FrameInfo tuple per code object/instruction offset, reuse
cached thread id objects, and append cached parent frames directly on
full frame-cache hits. This cuts Python allocation churn in the
steady-state profiler path.
If queue.SimpleQueue.put can't handoff the item to a
waiting thread, and fails to allocate memory when adding
the item to a ringbuf, it would leak a reference. Fixed.
Remove assertion that could fail in rare race condition.
Replace the coarse critical section wrapping the entire function with
fine-grained sections covering only PyDict_Next + Py_INCREF.
Also handle PyDict_Next returning 0 in the single-item fast path.
`faulthandler_traverse` visits Python objects owned by `_PyRuntime`, not
by the module instance. With multi-phase init allowing multiple module
instances, each instance's GC traversal decrements `gc_refs` on the same
runtime-owned objects, driving it negative when two instances are
collected simultaneously.
Change my_strchr() return type to "const char*" (add "const").
Fix the compiler warning:
Modules/_ctypes/_ctypes_test.c: In function 'my_strchr':
Modules/_ctypes/_ctypes_test.c:451:12: warning: return discards
'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
451 | return strchr(s, c);
| ^~~~~~
When using C23, strchr(text, ch) return type is "const char*" if text
type is "const char*".
In free-threaded builds, concurrent calls to PyDict_AddWatcher, PyDict_ClearWatcher, PyDict_Watch, and PyDict_Unwatch can race on the shared callback array and the per-dict watcher tags. This change adds a mutex to serialize watcher registration and removal, atomic operations for tag updates, and atomic acquire/release synchronization for callback dispatch in _PyDict_SendEvent.
