Fix wrong instruction pointer for exceptions

Author: Fidget-Spinner

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

Python/bytecodes.c

@@ -5384,7 +5384,10 @@ dummy_func(
 
         tier2 op(_ERROR_POP_N, (target/2 --)) {
             assert(oparg == 0);
-            frame->instr_ptr = _PyFrame_GetBytecode(frame) + target;
+            _Py_CODEUNIT *current_instr = _PyFrame_GetBytecode(frame) + target;
+            _Py_CODEUNIT *next_instr = current_instr + 1 + _PyOpcode_Caches[_PyOpcode_Deopt[current_instr->op.code]];
+            // gh-140104: The exception handler expects frame->instr_ptr to be pointing to next_instr, not this_instr!
+            frame->instr_ptr = next_instr;
             SYNC_SP();
             GOTO_TIER_ONE(NULL);
         }