Backport

Author: efimov-mikhail

Lib/test/test_capi/test_opt.py

@@ -1972,6 +1972,27 @@ def testfunc(n):
         assert ex is not None
         """))
 
+    def test_next_instr_for_exception_handler_set(self):
+        # gh-140104: We just want the exception to be caught properly.
+        def f():
+            for i in range(TIER2_THRESHOLD + 3):
+                try:
+                    undefined_variable(i)
+                except Exception:
+                    pass
+
+        f()
+
+    def test_next_instr_for_exception_handler_set_lasts_instr(self):
+        # gh-140104: We just want the exception to be caught properly.
+        def f():
+            a_list = []
+            for _ in range(TIER2_THRESHOLD + 3):
+                try:
+                    a_list[""] = 0
+                except Exception:
+                    pass
+
 
 def global_identity(x):
     return x

Misc/NEWS.d/next/Core_and_Builtins/2025-10-16-21-47-00.gh-issue-140104.A8SQIm.rst

@@ -0,0 +1,2 @@
+Fix a bug with exception handling in the JIT. Patch by Ken Jin. Bug reported
+by Daniel Diniz.

Python/ceval_macros.h

@@ -376,7 +376,9 @@ do {                                                   \
     frame = tstate->current_frame;                     \
     stack_pointer = _PyFrame_GetStackPointer(frame);   \
     if (next_instr == NULL) {                          \
-        next_instr = frame->instr_ptr;                 \
+        /* gh-140104: The exception handler expects frame->instr_ptr
+            to after this_instr, not this_instr! */    \
+        next_instr = frame->instr_ptr + 1;             \
         JUMP_TO_LABEL(error);                          \
     }                                                  \
     DISPATCH();                                        \
@@ -393,6 +395,7 @@ do { \
 } while (0)
 #endif
 
+#ifdef _Py_JIT
 #define GOTO_TIER_ONE(TARGET)                                         \
     do                                                                \
     {                                                                 \
@@ -409,6 +412,26 @@ do { \
         }                                                             \
         DISPATCH();                                                   \
     } while (0)
+#else
+#define GOTO_TIER_ONE(TARGET)                                         \
+    do                                                                \
+    {                                                                 \
+        tstate->current_executor = NULL;                              \
+        next_instr = (TARGET);                                        \
+        assert(tstate->current_executor == NULL);                     \
+        OPT_HIST(trace_uop_execution_counter, trace_run_length_hist); \
+        _PyFrame_SetStackPointer(frame, stack_pointer);               \
+        stack_pointer = _PyFrame_GetStackPointer(frame);              \
+        if (next_instr == NULL)                                       \
+        {                                                             \
+            /* gh-140104: The exception handler expects frame->instr_ptr
+                to after this_instr, not this_instr! */               \
+            next_instr = frame->instr_ptr + 1;                        \
+            goto error;                                               \
+        }                                                             \
+        DISPATCH();                                                   \
+    } while (0)
+#endif
 
 #define CURRENT_OPARG()    (next_uop[-1].oparg)
 #define CURRENT_OPERAND0() (next_uop[-1].operand0)