gh-143123: Protect against recursive tracer calls/finalization

Include/internal/pycore_tstate.h

@@ -54,6 +54,7 @@ typedef struct _PyJitTracerTranslatorState {
 } _PyJitTracerTranslatorState;
 
 typedef struct _PyJitTracerState {
+    bool is_tracing;
     _PyJitTracerInitialState initial_state;
     _PyJitTracerPreviousState prev_state;
     _PyJitTracerTranslatorState translator_state;

Lib/test/test_capi/test_opt.py

@@ -3606,6 +3606,51 @@ async def async_for_driver():
         """), PYTHON_JIT="1")
         self.assertEqual(result[0].rc, 0, result)
 
+    def test_143358(self):
+        # https://github.com/python/cpython/issues/143358
+
+        result = script_helper.run_python_until_end('-c', textwrap.dedent(f"""
+        def f1():
+
+            class EvilIterator:
+
+                def __init__(self):
+                    self._items = [1, 2]
+                    self._index = 1
+
+                def __iter__(self):
+                    return self
+
+                def __next__(self):
+                    if not len(self._items) % 13:
+                        self._items.clear()
+
+                    for i_loop_9279 in range(10):
+                        self._items.extend([1, "", None])
+
+                    if not len(self._items) % 11:
+                        return 'unexpected_type_from_iterator'
+
+                    if self._index >= len(self._items):
+                        raise StopIteration
+
+                    item = self._items[self._index]
+                    self._index += 1
+                    return item
+
+            evil_iter = EvilIterator()
+
+            large_num = 2**31
+            for _ in range(400):
+                try:
+                    _ = [x + y for x in evil_iter for y in evil_iter if evil_iter._items.append(x) or large_num]
+                except TypeError:
+                    pass
+
+        f1()
+        """), PYTHON_JIT="1", PYTHON_JIT_JUMP_BACKWARD_INITIAL_VALUE="64")
+        self.assertEqual(result[0].rc, 0, result)
+
 def global_identity(x):
     return x
 

Misc/NEWS.d/next/Core_and_Builtins/2025-12-23-23-36-41.gh-issue-143123.-51gt_.rst

@@ -0,0 +1 @@
+Protect the JIT against recursive tracing.

Python/bytecodes.c

@@ -5607,6 +5607,16 @@ dummy_func(
 #else
             assert(_PyErr_Occurred(tstate));
 #endif
+#if _Py_TIER2
+            if (IS_JIT_TRACING()) {
+                LEAVE_TRACING();
+                int res = stop_tracing_and_jit(tstate, frame);
+                (void)res;
+                // We shouldn't ven have compiled in the first place.
+                assert(res == 0);
+            }
+#endif
+
 
             /* Log traceback info. */
             assert(frame->owner != FRAME_OWNED_BY_INTERPRETER);

Python/optimizer.c

@@ -1030,11 +1030,11 @@ _PyJit_TryInitializeTracing(
             // Don't error, just go to next instruction.
             return 0;
         }
+        _tstate->jit_tracer_state->is_tracing = false;
     }
     _PyJitTracerState *tracer = _tstate->jit_tracer_state;
     // A recursive trace.
-    // Don't trace into the inner call because it will stomp on the previous trace, causing endless retraces.
-    if (tracer->prev_state.code_curr_size > CODE_SIZE_EMPTY) {
+    if (tracer->is_tracing) {
         return 0;
     }
     if (oparg > 0xFFFF) {
@@ -1086,6 +1086,7 @@ _PyJit_TryInitializeTracing(
         close_loop_instr[1].counter = trigger_backoff_counter();
     }
     _Py_BloomFilter_Init(&tracer->prev_state.dependencies);
+    tracer->is_tracing = true;
     return 1;
 }
 
@@ -1100,6 +1101,7 @@ _PyJit_FinalizeTracing(PyThreadState *tstate)
     Py_CLEAR(tracer->prev_state.instr_code);
     tracer->prev_state.code_curr_size = CODE_SIZE_EMPTY;
     tracer->prev_state.code_max_size = UOP_MAX_TRACE_LENGTH/2 - 1;
+    tracer->is_tracing = false;
 }
 
 void