GH-96793: Implement PEP 479 in bytecode.

Doc/library/dis.rst

@@ -607,6 +607,15 @@ the original TOS1.
  .. versionadded:: 3.12
 
 
+.. opcode:: STOPITERATION_ERROR
+
+ Handles a StopIteration raised in a generator or coroutine.
+ If TOS is an instance of :exc:`StopIteration`, or :exc:`StopAsyncIteration`
+ replace it with a :exc:`RuntimeError`.
+
+ .. versionadded:: 3.12
+
+
 .. opcode:: BEFORE_ASYNC_WITH
 
  Resolves ``__aenter__`` and ``__aexit__`` from the object on top of the

Lib/importlib/_bootstrap_external.py

@@ -424,6 +424,7 @@ def _write_atomic(path, data, mode=0o666):
 # Python 3.12a1 3508 (Add CLEANUP_THROW)
 # Python 3.12a1 3509 (Conditional jumps only jump forward)
 # Python 3.12a1 3510 (FOR_ITER leaves iterator on the stack)
+# Python 3.12a1 3511 (Add STOPITERATION_ERROR instruction)
 
 # Python 3.13 will start with 3550
 
@@ -436,7 +437,7 @@ def _write_atomic(path, data, mode=0o666):
 # Whenever MAGIC_NUMBER is changed, the ranges in the magic_values array
 # in PC/launcher.c must also be updated.
 
-MAGIC_NUMBER = (3510).to_bytes(2, 'little') + b'\r\n'
+MAGIC_NUMBER = (3511).to_bytes(2, 'little') + b'\r\n'
 
 _RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little') # For import.c
 

Lib/opcode.py

@@ -111,6 +111,8 @@ def pseudo_op(name, op, real_ops):
 def_op('STORE_SUBSCR', 60)
 def_op('DELETE_SUBSCR', 61)
 
+def_op('STOPITERATION_ERROR', 63)
+
 def_op('GET_ITER', 68)
 def_op('GET_YIELD_FROM_ITER', 69)
 def_op('PRINT_EXPR', 70)

Lib/test/test_dis.py

@@ -543,8 +543,10 @@ async def _asyncwith(c):
  >> COPY 3
  POP_EXCEPT
  RERAISE 1
+ >> STOPITERATION_ERROR
+ RERAISE 1
 ExceptionTable:
-6 rows
+12 rows
 """ % (_asyncwith.__code__.co_firstlineno,
  _asyncwith.__code__.co_firstlineno + 1,
  _asyncwith.__code__.co_firstlineno + 2,

Lib/test/test_sys.py

@@ -1439,7 +1439,7 @@ def bar(cls):
  check(bar, size('PP'))
  # generator
  def get_gen(): yield 1
- check(get_gen(), size('P2P4P4c7P2ic??P'))
+ check(get_gen(), size('P2P4P4c7P2ic??2P'))
  # iterator
  check(iter('abc'), size('lP'))
  # callable-iterator

Lib/test/test_sys_settrace.py

@@ -346,7 +346,7 @@ def make_tracer():
  return Tracer()
 
  def compare_events(self, line_offset, events, expected_events):
- events = [(l - line_offset, e) for (l, e) in events]
+ events = [(l - line_offset if l is not None else None, e) for (l, e) in events]
  if events != expected_events:
  self.fail(
  "events did not match expectation:\n" +

Misc/NEWS.d/next/Core and Builtins/2022-11-02-14-42-35.gh-issue-96793.q0Oi74.rst

@@ -0,0 +1,2 @@
+Handle StopIteration and StopAsyncIteration raised in generator or
+coroutines in the bytecode, rather than in wrapping C code.

Objects/genobject.c

@@ -246,25 +246,9 @@ gen_send_ex2(PyGenObject *gen, PyObject *arg, PyObject **presult,
  }
  }
  else{
- if (PyErr_ExceptionMatches(PyExc_StopIteration)){
- const char *msg = "generator raised StopIteration"
- if (PyCoro_CheckExact(gen)){
- msg = "coroutine raised StopIteration"
- }
- else if (PyAsyncGen_CheckExact(gen)){
- msg = "async generator raised StopIteration"
- }
- _PyErr_FormatFromCause(PyExc_RuntimeError, "%s", msg);
- }
- else if (PyAsyncGen_CheckExact(gen) &&
- PyErr_ExceptionMatches(PyExc_StopAsyncIteration))
-{
- /* code in `gen` raised a StopAsyncIteration error:
- raise a RuntimeError.
- */
- const char *msg = "async generator raised StopAsyncIteration"
- _PyErr_FormatFromCause(PyExc_RuntimeError, "%s", msg);
- }
+ assert(!PyErr_ExceptionMatches(PyExc_StopIteration));
+ assert(!PyAsyncGen_CheckExact(gen) ||
+ !PyErr_ExceptionMatches(PyExc_StopAsyncIteration));
  }
 
  /* generator can't be rerun, so release the frame */

Python/bytecodes.c

@@ -1085,6 +1085,49 @@ dummy_func(
  goto exception_unwind;
  }
 
+ inst(STOPITERATION_ERROR){
+ assert(frame->owner == FRAME_OWNED_BY_GENERATOR);
+ PyObject *exc = TOP();
+ assert(PyExceptionInstance_Check(exc));
+ const char *msg = NULL;
+ if (PyErr_GivenExceptionMatches(exc, PyExc_StopIteration)){
+ msg = "generator raised StopIteration"
+ if (frame->f_code->co_flags & CO_ASYNC_GENERATOR){
+ msg = "async generator raised StopIteration"
+ }
+ else if (frame->f_code->co_flags & CO_COROUTINE){
+ msg = "coroutine raised StopIteration"
+ }
+ }
+ else if ((frame->f_code->co_flags & CO_ASYNC_GENERATOR) &&
+ PyErr_GivenExceptionMatches(exc, PyExc_StopAsyncIteration))
+{
+ /* code in `gen` raised a StopAsyncIteration error:
+ raise a RuntimeError.
+ */
+ msg = "async generator raised StopAsyncIteration"
+ }
+ if (msg != NULL){
+ PyObject *message = _PyUnicode_FromASCII(msg, strlen(msg));
+ if (message == NULL){
+ goto error;
+ }
+ PyObject *error = PyObject_CallOneArg(PyExc_RuntimeError, message);
+ if (error == NULL){
+ Py_DECREF(message);
+ goto error;
+ }
+ assert(PyExceptionInstance_Check(error));
+ SET_TOP(error);
+ PyException_SetCause(error, exc);
+ Py_INCREF(exc);
+ PyException_SetContext(error, exc);
+ Py_DECREF(message);
+ }
+ DISPATCH();
+ }
+
+
  // stack effect: ( -- __0)
  inst(LOAD_ASSERTION_ERROR){
  PyObject *value = PyExc_AssertionError;