address review comments.

Author: gpshead

Doc/c-api/init.rst

@@ -988,7 +988,7 @@ attempts to acquire a lock owned by the blocked thread, or otherwise waits on
 the blocked thread.
 
 Gross? Yes. This prevents random crashes and/or unexpectedly skipped C++
-finalizations further up the call stack when such threads were forcably exited
+finalizations further up the call stack when such threads were forcibly exited
 here in CPython 3.13 and earlier. The CPython runtime GIL acquiring C APIs
 have never had any error reporting or handling expectations at GIL acquisition
 time that would've allowed for graceful exit from this situation. Changing that

Include/pythread.h

@@ -17,17 +17,17 @@ typedef enum PyLockStatus {
 
 PyAPI_FUNC(void) PyThread_init_thread(void);
 PyAPI_FUNC(unsigned long) PyThread_start_new_thread(void (*)(void *), void *);
-/* Terminates the current thread.
+/* Terminates the current thread. Considered unsafe.
  *
  * WARNING: This function is only safe to call if all functions in the full call
  * stack are written to safely allow it.  Additionally, the behavior is
  * platform-dependent.  This function should be avoided, and is no longer called
  * by Python itself.  It is retained only for compatibility with existing C
  * extension code.
  *
- * With pthreads, calls `pthread_exit` which attempts to unwind the stack and
- * call C++ destructors.  If a `noexcept` function is reached, the program is
- * terminated.
+ * With pthreads, calls `pthread_exit` causes some libcs (glibc?) to attempt to
+ * unwind the stack and call C++ destructors; if a `noexcept` function is
+ * reached, they may terminate the process. Others (macOS) do unwinding.
  *
  * On Windows, calls `_endthreadex` which kills the thread without calling C++
  * destructors.

Modules/_testcapimodule.c

@@ -3333,7 +3333,7 @@ test_critical_sections(PyObject *module, PyObject *Py_UNUSED(args))
 #ifdef _POSIX_THREADS
 static void finalize_thread_hang_cleanup_callback(void *Py_UNUSED(arg)) {
     // Should not reach here.
-    assert(0 && "pthread thread termination was triggered unexpectedly");
+    Py_FatalError("pthread thread termination was triggered unexpectedly");
 }
 #endif
 
@@ -3342,12 +3342,12 @@ static void finalize_thread_hang_cleanup_callback(void *Py_UNUSED(arg)) {
 // Must be called with a single nullary callable function that should block
 // (with GIL released) until finalization is in progress.
 static PyObject *
-finalize_thread_hang(PyObject *self, PyObject *arg)
+finalize_thread_hang(PyObject *self, PyObject *callback)
 {
 #ifdef _POSIX_THREADS
     pthread_cleanup_push(finalize_thread_hang_cleanup_callback, NULL);
 #endif
-    PyObject_CallNoArgs(arg);
+    PyObject_CallNoArgs(callback);
     // Should not reach here.
     Py_FatalError("thread unexpectedly did not hang");
 #ifdef _POSIX_THREADS