gh-140104: Set next_instr properly in the JIT during exceptions

Lib/test/test_capi/test_opt.py

@@ -2637,6 +2637,17 @@ def f2():
 
         f2()
 
+    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:
+                    g(i)
+                except Exception:
+                    pass
+
+        f()
+
 
 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/bytecodes.c

@@ -5384,7 +5384,6 @@ dummy_func(
 
         tier2 op(_ERROR_POP_N, (target/2 --)) {
             assert(oparg == 0);
-            frame->instr_ptr = _PyFrame_GetBytecode(frame) + target;
             SYNC_SP();
             GOTO_TIER_ONE(NULL);
         }

Python/ceval_macros.h

@@ -358,7 +358,9 @@ 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 be pointing to next_instr, not this_instr! */ \
+        next_instr = frame->instr_ptr + 1 + _PyOpcode_Caches[_PyOpcode_Deopt[frame->instr_ptr->op.code]];                 \
         JUMP_TO_LABEL(error);                          \
     }                                                  \
     DISPATCH();                                        \