gh-104690: thread_run() checks for tstate dangling pointer (#109056)

thread_run() of _threadmodule.c now calls
_PyThreadState_CheckConsistency() to check if tstate is a dangling
pointer when Python is built in debug mode.

Rename ceval_gil.c is_tstate_valid() to
_PyThreadState_CheckConsistency() to reuse it in _threadmodule.c.

1 files changed, 18 insertions, 0 deletions

diff --git a/Python/pystate.c b/Python/pystate.c
index 89275fd..09c3538 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -2890,6 +2890,24 @@ _PyThreadState_PopFrame(PyThreadState *tstate, _PyInterpreterFrame * frame)
 }
 
 
+#ifndef NDEBUG
+// Check that a Python thread state valid. In practice, this function is used
+// on a Python debug build to check if 'tstate' is a dangling pointer, if the
+// PyThreadState memory has been freed.
+//
+// Usage:
+//
+//     assert(_PyThreadState_CheckConsistency(tstate));
+int
+_PyThreadState_CheckConsistency(PyThreadState *tstate)
+{
+    assert(!_PyMem_IsPtrFreed(tstate));
+    assert(!_PyMem_IsPtrFreed(tstate->interp));
+    return 1;
+}
+#endif
+
+
 #ifdef __cplusplus
 }
 #endif