bpo-45711: Remove type and traceback from exc_info (GH-30122)

* Do not PUSH/POP traceback or type to the stack as part of exc_info

* Remove exc_traceback and exc_type from _PyErr_StackItem

* Add to what's new, because this change breaks things like Cython

4 files changed, 119 insertions, 269 deletions

diff --git a/Python/ceval.c b/Python/ceval.c
index 87d6a2288e..bac57ccb7c 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -1094,29 +1094,11 @@ fail:
 static int do_raise(PyThreadState *tstate, PyObject *exc, PyObject *cause);
 static PyObject *do_reraise_star(PyObject *excs, PyObject *orig);
 static int exception_group_match(
-    PyObject *exc_type, PyObject* exc_value, PyObject *match_type,
+    PyObject* exc_value, PyObject *match_type,
     PyObject **match, PyObject **rest);
 
 static int unpack_iterable(PyThreadState *, PyObject *, int, int, PyObject **);
 
-#ifdef Py_DEBUG
-static void
-_assert_exception_type_is_redundant(PyObject* type, PyObject* val)
-{
-    if (type == NULL || type == Py_None) {
-        assert(val == type);
-    }
-    else {
-        assert(PyExceptionInstance_Check(val));
-        assert(PyExceptionInstance_Class(val) == type);
-    }
-}
-
-#define ASSERT_EXC_TYPE_IS_REDUNDANT(t, v) _assert_exception_type_is_redundant(t, v)
-#else
-#define ASSERT_EXC_TYPE_IS_REDUNDANT(t, v)
-#endif
-
 PyObject *
 PyEval_EvalCode(PyObject *co, PyObject *globals, PyObject *locals)
 {
@@ -2737,25 +2719,15 @@ check_eval_breaker:
         }
 
         TARGET(POP_EXCEPT) {
-            PyObject *type, *value, *traceback;
-            _PyErr_StackItem *exc_info;
-            exc_info = tstate->exc_info;
-            type = exc_info->exc_type;
-            value = exc_info->exc_value;
-            traceback = exc_info->exc_traceback;
-
-            exc_info->exc_type = POP();
+            _PyErr_StackItem *exc_info = tstate->exc_info;
+            PyObject *value = exc_info->exc_value;
             exc_info->exc_value = POP();
-            exc_info->exc_traceback = POP();
-            ASSERT_EXC_TYPE_IS_REDUNDANT(exc_info->exc_type, exc_info->exc_value);
-            Py_XDECREF(type);
             Py_XDECREF(value);
-            Py_XDECREF(traceback);
             DISPATCH();
         }
 
         TARGET(POP_EXCEPT_AND_RERAISE) {
-            PyObject *lasti = PEEK(4);
+            PyObject *lasti = PEEK(2);
             if (PyLong_Check(lasti)) {
                 frame->f_lasti = PyLong_AsLong(lasti);
                 assert(!_PyErr_Occurred(tstate));
@@ -2764,31 +2736,24 @@ check_eval_breaker:
                 _PyErr_SetString(tstate, PyExc_SystemError, "lasti is not an int");
                 goto error;
             }
-            PyObject *type, *value, *traceback;
-            _PyErr_StackItem *exc_info;
-            type = POP();
-            value = POP();
-            traceback = POP();
-            ASSERT_EXC_TYPE_IS_REDUNDANT(type, value);
+            PyObject *value = POP();
+            assert(value);
+            assert(PyExceptionInstance_Check(value));
+            PyObject *type = Py_NewRef(PyExceptionInstance_Class(value));
+            PyObject *traceback = PyException_GetTraceback(value);
             Py_DECREF(POP()); /* lasti */
             _PyErr_Restore(tstate, type, value, traceback);
-            exc_info = tstate->exc_info;
-            type = exc_info->exc_type;
+
+            _PyErr_StackItem *exc_info = tstate->exc_info;
             value = exc_info->exc_value;
-            traceback = exc_info->exc_traceback;
-            exc_info->exc_type = POP();
             exc_info->exc_value = POP();
-            exc_info->exc_traceback = POP();
-            ASSERT_EXC_TYPE_IS_REDUNDANT(exc_info->exc_type, exc_info->exc_value);
-            Py_XDECREF(type);
             Py_XDECREF(value);
-            Py_XDECREF(traceback);
             goto exception_unwind;
         }
 
         TARGET(RERAISE) {
             if (oparg) {
-                PyObject *lasti = PEEK(oparg+3);
+                PyObject *lasti = PEEK(oparg + 1);
                 if (PyLong_Check(lasti)) {
                     frame->f_lasti = PyLong_AsLong(lasti);
                     assert(!_PyErr_Occurred(tstate));
@@ -2799,11 +2764,10 @@ check_eval_breaker:
                     goto error;
                 }
             }
-            PyObject *exc = POP();
             PyObject *val = POP();
-            PyObject *tb = POP();
-            ASSERT_EXC_TYPE_IS_REDUNDANT(exc, val);
-            assert(PyExceptionClass_Check(exc));
+            assert(val && PyExceptionInstance_Check(val));
+            PyObject *exc = Py_NewRef(PyExceptionInstance_Class(val));
+            PyObject *tb = PyException_GetTraceback(val);
             _PyErr_Restore(tstate, exc, val, tb);
             goto exception_unwind;
         }
@@ -2823,35 +2787,21 @@ check_eval_breaker:
 
             PyObject *lasti_unused = Py_NewRef(_PyLong_GetZero());
             PUSH(lasti_unused);
-            if (!Py_IsNone(val)) {
-                PyObject *tb = PyException_GetTraceback(val);
-                PUSH(tb ? tb : Py_NewRef(Py_None));
-                PUSH(val);
-                PUSH(Py_NewRef(Py_TYPE(val)));
-            }
-            else {
-                // nothing to reraise
-                PUSH(Py_NewRef(Py_None));
-                PUSH(val);
-                PUSH(Py_NewRef(Py_None));
-            }
+            PUSH(val);
             DISPATCH();
         }
 
         TARGET(END_ASYNC_FOR) {
-            PyObject *exc = POP();
             PyObject *val = POP();
-            PyObject *tb = POP();
-            ASSERT_EXC_TYPE_IS_REDUNDANT(exc, val);
-            assert(PyExceptionClass_Check(exc));
-            if (PyErr_GivenExceptionMatches(exc, PyExc_StopAsyncIteration)) {
-                Py_DECREF(exc);
+            assert(val && PyExceptionInstance_Check(val));
+            if (PyErr_GivenExceptionMatches(val, PyExc_StopAsyncIteration)) {
                 Py_DECREF(val);
-                Py_DECREF(tb);
                 Py_DECREF(POP());
                 DISPATCH();
             }
             else {
+                PyObject *exc = Py_NewRef(PyExceptionInstance_Class(val));
+                PyObject *tb = PyException_GetTraceback(val);
                 _PyErr_Restore(tstate, exc, val, tb);
                 goto exception_unwind;
             }
@@ -3971,16 +3921,15 @@ check_eval_breaker:
 
         TARGET(JUMP_IF_NOT_EG_MATCH) {
             PyObject *match_type = POP();
-            PyObject *exc_type = TOP();
-            PyObject *exc_value = SECOND();
             if (check_except_star_type_valid(tstate, match_type) < 0) {
                 Py_DECREF(match_type);
                 goto error;
             }
 
+            PyObject *exc_value = TOP();
             PyObject *match = NULL, *rest = NULL;
-            int res = exception_group_match(exc_type, exc_value,
-                                            match_type, &match, &rest);
+            int res = exception_group_match(exc_value, match_type,
+                                            &match, &rest);
             Py_DECREF(match_type);
             if (res < 0) {
                 goto error;
@@ -4001,46 +3950,21 @@ check_eval_breaker:
             else {
 
                 /* Total or partial match - update the stack from
-                 * [tb, val, exc]
+                 * [val]
                  * to
-                 * [tb, rest, exc, tb, match, exc]
+                 * [rest, match]
                  * (rest can be Py_None)
                  */
 
+                PyObject *exc = TOP();
 
-                PyObject *type = TOP();
-                PyObject *val = SECOND();
-                PyObject *tb = THIRD();
-
-                if (!Py_IsNone(rest)) {
-                    /* tb remains the same */
-                    SET_TOP(Py_NewRef(Py_TYPE(rest)));
-                    SET_SECOND(Py_NewRef(rest));
-                    SET_THIRD(Py_NewRef(tb));
-                }
-                else {
-                    SET_TOP(Py_NewRef(Py_None));
-                    SET_SECOND(Py_NewRef(Py_None));
-                    SET_THIRD(Py_NewRef(Py_None));
-                }
-                /* Push match */
+                SET_TOP(rest);
+                PUSH(match);
 
-                PUSH(Py_NewRef(tb));
-                PUSH(Py_NewRef(match));
-                PUSH(Py_NewRef(Py_TYPE(match)));
+                PyErr_SetExcInfo(NULL, Py_NewRef(match), NULL);
 
-                // set exc_info to the current match
-                PyErr_SetExcInfo(
-                    Py_NewRef(Py_TYPE(match)),
-                    Py_NewRef(match),
-                    Py_NewRef(tb));
-
-                Py_DECREF(tb);
-                Py_DECREF(val);
-                Py_DECREF(type);
+                Py_DECREF(exc);
 
-                Py_DECREF(match);
-                Py_DECREF(rest);
             }
 
             DISPATCH();
@@ -4048,8 +3972,7 @@ check_eval_breaker:
 
         TARGET(JUMP_IF_NOT_EXC_MATCH) {
             PyObject *right = POP();
-            ASSERT_EXC_TYPE_IS_REDUNDANT(TOP(), SECOND());
-            PyObject *left = SECOND();
+            PyObject *left = TOP();
             assert(PyExceptionInstance_Check(left));
             if (check_except_type_valid(tstate, right) < 0) {
                  Py_DECREF(right);
@@ -4465,26 +4388,24 @@ check_eval_breaker:
         }
 
         TARGET(WITH_EXCEPT_START) {
-            /* At the top of the stack are 8 values:
-               - (TOP, SECOND, THIRD) = exc_info()
-               - (FOURTH, FIFTH, SIXTH) = previous exception
-               - SEVENTH: lasti of exception in exc_info()
-               - EIGHTH: the context.__exit__ bound method
-               We call EIGHTH(TOP, SECOND, THIRD).
-               Then we push again the TOP exception and the __exit__
-               return value.
+            /* At the top of the stack are 4 values:
+               - TOP = exc_info()
+               - SECOND = previous exception
+               - THIRD: lasti of exception in exc_info()
+               - FOURTH: the context.__exit__ bound method
+               We call FOURTH(type(TOP), TOP, GetTraceback(TOP)).
+               Then we push the __exit__ return value.
             */
             PyObject *exit_func;
             PyObject *exc, *val, *tb, *res;
 
-            exc = TOP();
-            val = SECOND();
-            tb = THIRD();
-            ASSERT_EXC_TYPE_IS_REDUNDANT(exc, val);
-            assert(!Py_IsNone(exc));
-            assert(!PyLong_Check(exc));
-            assert(PyLong_Check(PEEK(7)));
-            exit_func = PEEK(8);
+            val = TOP();
+            assert(val && PyExceptionInstance_Check(val));
+            exc = PyExceptionInstance_Class(val);
+            tb = PyException_GetTraceback(val);
+            Py_XDECREF(tb);
+            assert(PyLong_Check(PEEK(3)));
+            exit_func = PEEK(4);
             PyObject *stack[4] = {NULL, exc, val, tb};
             res = PyObject_Vectorcall(exit_func, stack + 1,
                     3 | PY_VECTORCALL_ARGUMENTS_OFFSET, NULL);
@@ -4496,40 +4417,22 @@ check_eval_breaker:
         }
 
         TARGET(PUSH_EXC_INFO) {
-            PyObject *type = TOP();
-            PyObject *value = SECOND();
-            PyObject *tb = THIRD();
-            ASSERT_EXC_TYPE_IS_REDUNDANT(type, value);
+            PyObject *value = TOP();
+
             _PyErr_StackItem *exc_info = tstate->exc_info;
-            SET_THIRD(exc_info->exc_traceback);
             if (exc_info->exc_value != NULL) {
-                SET_SECOND(exc_info->exc_value);
-            }
-            else {
-                Py_INCREF(Py_None);
-                SET_SECOND(Py_None);
-            }
-            if (exc_info->exc_type != NULL) {
-                SET_TOP(exc_info->exc_type);
+                SET_TOP(exc_info->exc_value);
             }
             else {
                 Py_INCREF(Py_None);
                 SET_TOP(Py_None);
             }
-            Py_INCREF(tb);
-            PUSH(tb);
-            exc_info->exc_traceback = tb;
 
             Py_INCREF(value);
             PUSH(value);
             assert(PyExceptionInstance_Check(value));
             exc_info->exc_value = value;
 
-            Py_INCREF(type);
-            PUSH(type);
-            assert(PyExceptionClass_Check(type));
-            exc_info->exc_type = type;
-
             DISPATCH();
         }
 
@@ -5518,14 +5421,9 @@ exception_unwind:
             PyException_SetTraceback(val, tb);
         else
             PyException_SetTraceback(val, Py_None);
-        if (tb == NULL) {
-            tb = Py_None;
-            Py_INCREF(Py_None);
-        }
-        PUSH(tb);
+        Py_XDECREF(tb);
+        Py_XDECREF(exc);
         PUSH(val);
-        PUSH(exc);
-        ASSERT_EXC_TYPE_IS_REDUNDANT(exc, val);
         JUMPTO(handler);
         /* Resume normal execution */
         frame->f_state = FRAME_EXECUTING;
@@ -6375,19 +6273,17 @@ raise_error:
 */
 
 static int
-exception_group_match(PyObject *exc_type, PyObject* exc_value,
-                      PyObject *match_type, PyObject **match, PyObject **rest)
+exception_group_match(PyObject* exc_value, PyObject *match_type,
+                      PyObject **match, PyObject **rest)
 {
-    if (Py_IsNone(exc_type)) {
-        assert(Py_IsNone(exc_value));
+    if (Py_IsNone(exc_value)) {
         *match = Py_NewRef(Py_None);
         *rest = Py_NewRef(Py_None);
         return 0;
     }
-    assert(PyExceptionClass_Check(exc_type));
     assert(PyExceptionInstance_Check(exc_value));
 
-    if (PyErr_GivenExceptionMatches(exc_type, match_type)) {
+    if (PyErr_GivenExceptionMatches(exc_value, match_type)) {
         /* Full match of exc itself */
         bool is_eg = _PyBaseExceptionGroup_Check(exc_value);
         if (is_eg) {
diff --git a/Python/compile.c b/Python/compile.c
index 6179ad980a..8e90b1ab37 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -1048,9 +1048,9 @@ stack_effect(int opcode, int oparg, int jump)
         case POP_BLOCK:
             return 0;
         case POP_EXCEPT:
-            return -3;
+            return -1;
         case POP_EXCEPT_AND_RERAISE:
-            return -7;
+            return -3;
 
         case STORE_NAME:
             return -1;
@@ -1095,7 +1095,7 @@ stack_effect(int opcode, int oparg, int jump)
         case JUMP_IF_NOT_EXC_MATCH:
             return -1;
         case JUMP_IF_NOT_EG_MATCH:
-            return jump > 0 ? -1 : 2;
+            return jump > 0 ? -1 : 0;
         case IMPORT_NAME:
             return -1;
         case IMPORT_FROM:
@@ -1120,25 +1120,25 @@ stack_effect(int opcode, int oparg, int jump)
         /* Exception handling pseudo-instructions */
         case SETUP_FINALLY:
             /* 0 in the normal flow.
-             * Restore the stack position and push 3 values before jumping to
+             * Restore the stack position and push 1 value before jumping to
              * the handler if an exception be raised. */
-            return jump ? 3 : 0;
+            return jump ? 1 : 0;
         case SETUP_CLEANUP:
             /* As SETUP_FINALLY, but pushes lasti as well */
-            return jump ? 4 : 0;
+            return jump ? 2 : 0;
         case SETUP_WITH:
             /* 0 in the normal flow.
              * Restore the stack position to the position before the result
-             * of __(a)enter__ and push 4 values before jumping to the handler
+             * of __(a)enter__ and push 2 values before jumping to the handler
              * if an exception be raised. */
-            return jump ? -1 + 4 : 0;
+            return jump ? 1 : 0;
 
         case PREP_RERAISE_STAR:
-             return 2;
+             return 0;
         case RERAISE:
-            return -3;
+            return -1;
         case PUSH_EXC_INFO:
-            return 3;
+            return 1;
 
         case WITH_EXCEPT_START:
             return 1;
@@ -1199,7 +1199,7 @@ stack_effect(int opcode, int oparg, int jump)
         case GET_YIELD_FROM_ITER:
             return 0;
         case END_ASYNC_FOR:
-            return -4;
+            return -2;
         case FORMAT_VALUE:
             /* If there's a fmt_spec on the stack, we go from 2->1,
                else 1->1. */
@@ -1888,13 +1888,11 @@ compiler_unwind_fblock(struct compiler *c, struct fblockinfo *info,
 
         case FINALLY_END:
             if (preserve_tos) {
-                ADDOP(c, ROT_FOUR);
+                ADDOP(c, ROT_TWO);
             }
-            ADDOP(c, POP_TOP);
-            ADDOP(c, POP_TOP);
-            ADDOP(c, POP_TOP);
+            ADDOP(c, POP_TOP); /* exc_value */
             if (preserve_tos) {
-                ADDOP(c, ROT_FOUR);
+                ADDOP(c, ROT_TWO);
             }
             ADDOP(c, POP_BLOCK);
             ADDOP(c, POP_EXCEPT);
@@ -1927,7 +1925,7 @@ compiler_unwind_fblock(struct compiler *c, struct fblockinfo *info,
                 ADDOP(c, POP_BLOCK);
             }
             if (preserve_tos) {
-                ADDOP(c, ROT_FOUR);
+                ADDOP(c, ROT_TWO);
             }
             ADDOP(c, POP_BLOCK);
             ADDOP(c, POP_EXCEPT);
@@ -3310,18 +3308,16 @@ compiler_try_star_finally(struct compiler *c, stmt_ty s)
    []                           POP_BLOCK
    []                           JUMP_FORWARD    L0
 
-   [tb, val, exc]       L1:     <evaluate E1>                   )
-   [tb, val, exc, E1]           JUMP_IF_NOT_EXC_MATCH L2        ) only if E1
-   [tb, val, exc]               POP
-   [tb, val]                    <assign to V1>  (or POP if no V1)
-   [tb]                         POP
+   [exc]                L1:     <evaluate E1>           )
+   [exc, E1]                    JUMP_IF_NOT_EXC_MATCH L2        ) only if E1
+   [exc]                        <assign to V1>  (or POP if no V1)
    []                           <code for S1>
                                 JUMP_FORWARD    L0
 
-   [tb, val, exc]       L2:     <evaluate E2>
+   [exc]                L2:     <evaluate E2>
    .............................etc.......................
 
-   [tb, val, exc]       Ln+1:   RERAISE     # re-raise exception
+   [exc]                Ln+1:   RERAISE     # re-raise exception
 
    []                   L0:     <next statement>
 
@@ -3372,7 +3368,6 @@ compiler_try_except(struct compiler *c, stmt_ty s)
             ADDOP_JUMP(c, JUMP_IF_NOT_EXC_MATCH, except);
             NEXT_BLOCK(c);
         }
-        ADDOP(c, POP_TOP);
         if (handler->v.ExceptHandler.name) {
             basicblock *cleanup_end, *cleanup_body;
 
@@ -3383,7 +3378,6 @@ compiler_try_except(struct compiler *c, stmt_ty s)
             }
 
             compiler_nameop(c, handler->v.ExceptHandler.name, Store);
-            ADDOP(c, POP_TOP);
 
             /*
               try:
@@ -3434,8 +3428,7 @@ compiler_try_except(struct compiler *c, stmt_ty s)
             if (!cleanup_body)
                 return 0;
 
-            ADDOP(c, POP_TOP);
-            ADDOP(c, POP_TOP);
+            ADDOP(c, POP_TOP); /* exc_value */
             compiler_use_next_block(c, cleanup_body);
             if (!compiler_push_fblock(c, HANDLER_CLEANUP, cleanup_body, NULL, NULL))
                 return 0;
@@ -3467,52 +3460,42 @@ compiler_try_except(struct compiler *c, stmt_ty s)
    at the right; 'tb' is trace-back info, 'val' the exception instance,
    and 'typ' the exception's type.)
 
-   Value stack                             Label         Instruction     Argument
-   []                                                   SETUP_FINALLY         L1
-   []                                                   <code for S>
-   []                                                   POP_BLOCK
-   []                                                   JUMP_FORWARD          L0
+   Value stack                   Label         Instruction     Argument
+   []                                         SETUP_FINALLY         L1
+   []                                         <code for S>
+   []                                         POP_BLOCK
+   []                                         JUMP_FORWARD          L0
 
-   [tb, val, typ]                            L1:        DUP_TOP_TWO               )  save a copy of the
-   [tb, val, typ, orig, typ]                            POP_TOP                   )  original raised exception
-   [tb, val, typ, orig]                                 ROT_FOUR                  )
-   [orig, tb, val, typ]                                 BUILD_LIST                )  list for raised/reraised
-   [orig, tb, val, typ, res]                            ROT_FOUR                  )  exceptions ("result")
+   [exc]                            L1:       DUP_TOP      )  save copy of the original exception
+   [orig, exc]                                BUILD_LIST   )  list for raised/reraised excs ("result")
+   [orig, exc, res]                           ROT_TWO
 
-   [orig, res, tb, val, typ]                            <evaluate E1>             )
-   [orig, res, tb, val, typ, E1]                        JUMP_IF_NOT_EXC_MATCH L2  ) only if E1
+   [orig, res, exc]                           <evaluate E1>
+   [orig, res, exc, E1]                       JUMP_IF_NOT_EG_MATCH L2
 
-   [orig, res, tb, rest, typ, tb, match, typ]           POP
-   [orig, res, tb, rest, typ, tb, match]                <assign to V1>  (or POP if no V1)
-   [orig, res, tb, rest, typ, tb]                       POP
+   [orig, res, rest, match]                   <assign to V1>  (or POP if no V1)
 
-   [orig, res, tb, rest, typ]                           SETUP_FINALLY         R1
-   [orig, res, tb, rest, typ]                           <code for S1>
-   [orig, res, tb, rest, typ]                           JUMP_FORWARD          L2
+   [orig, res, rest]                          SETUP_FINALLY         R1
+   [orig, res, rest]                          <code for S1>
+   [orig, res, rest]                          JUMP_FORWARD          L2
 
-   [orig, res, tb, rest, typ, i, tb, v, t]   R1:        POP           ) exception raised in except* body
-   [orig, res, tb, rest, typ, i, tb, v]                 LIST_APPEND 6 ) add it to res
-   [orig, res, tb, rest, typ, i, tb]                    POP
-   [orig, res, tb, rest, typ, i]                        POP
+   [orig, res, rest, i, v]          R1:       LIST_APPEND   3 ) exc raised in except* body - add to res
+   [orig, res, rest, i]                       POP
 
-   [orig, res, tb, rest, typ]                L2:        <evaluate E2>
+   [orig, res, rest]                L2:       <evaluate E2>
    .............................etc.......................
 
-   [orig, res, tb, rest, typ]                Ln+1:       POP           ) add unhandled exception
-   [orig, res, tb, rest]                                 LIST_APPEND 2 ) to res (could be None)
-   [orig, res, tb]                                       POP
+   [orig, res, rest]                Ln+1:     LIST_APPEND 1  ) add unhandled exc to res (could be None)
 
-   [orig, res]                                           PREP_RERAISE_STAR
-   [i, tb, val, typ]                                     POP_JUMP_IF_TRUE      RER
-   [i, tb, val, typ]                                     POP
-   [i, tb, val]                                          POP
-   [i, tb]                                               POP
-   [i]                                                   POP
-   []                                                    JUMP_FORWARD          L0
+   [orig, res]                                PREP_RERAISE_STAR
+   [i, exc]                                   POP_JUMP_IF_TRUE      RER
+   [i, exc]                                   POP
+   [i]                                        POP
+   []                                         JUMP_FORWARD          L0
 
-   [i, tb, val, typ]                        RER:         POP_EXCEPT_AND_RERAISE
+   [i, exc]                         RER:      POP_EXCEPT_AND_RERAISE
 
-   []                                       L0:     <next statement>
+   []                               L0:       <next statement>
 */
 static int
 compiler_try_star_except(struct compiler *c, stmt_ty s)
@@ -3573,30 +3556,25 @@ compiler_try_star_except(struct compiler *c, stmt_ty s)
         if (i == 0) {
             /* Push the original EG into the stack */
             /*
-               [tb, val, exc]            DUP_TOP_TWO
-               [tb, val, exc, val, exc]  POP_TOP
-               [tb, val, exc, val]       ROT_FOUR
-               [val, tb, val, exc]
+               [exc]            DUP_TOP
+               [orig, exc]
             */
-            ADDOP(c, DUP_TOP_TWO);
-            ADDOP(c, POP_TOP);
-            ADDOP(c, ROT_FOUR);
+            ADDOP(c, DUP_TOP);
 
             /* create empty list for exceptions raised/reraise in the except* blocks */
             /*
-               [val, tb, val, exc]       BUILD_LIST
-               [val, tb, val, exc, []]   ROT_FOUR
-               [val, [], tb, val, exc]
+               [orig, exc]       BUILD_LIST
+               [orig, exc, []]   ROT_TWO
+               [orig, [], exc]
             */
             ADDOP_I(c, BUILD_LIST, 0);
-            ADDOP(c, ROT_FOUR);
+            ADDOP(c, ROT_TWO);
         }
         if (handler->v.ExceptHandler.type) {
             VISIT(c, expr, handler->v.ExceptHandler.type);
             ADDOP_JUMP(c, JUMP_IF_NOT_EG_MATCH, except);
             NEXT_BLOCK(c);
         }
-        ADDOP(c, POP_TOP);  // exc_type
 
         basicblock *cleanup_end = compiler_new_block(c);
         if (cleanup_end == NULL) {
@@ -3611,9 +3589,8 @@ compiler_try_star_except(struct compiler *c, stmt_ty s)
             compiler_nameop(c, handler->v.ExceptHandler.name, Store);
         }
         else {
-            ADDOP(c, POP_TOP);  // val
+            ADDOP(c, POP_TOP);  // exc
         }
-        ADDOP(c, POP_TOP);  // tb
 
         /*
           try:
@@ -3657,9 +3634,7 @@ compiler_try_star_except(struct compiler *c, stmt_ty s)
         }
 
         /* add exception raised to the res list */
-        ADDOP(c, POP_TOP); // type
-        ADDOP_I(c, LIST_APPEND, 6); // exc
-        ADDOP(c, POP_TOP); // tb
+        ADDOP_I(c, LIST_APPEND, 3); // exc
         ADDOP(c, POP_TOP); // lasti
 
         ADDOP_JUMP(c, JUMP_ABSOLUTE, except);
@@ -3667,9 +3642,7 @@ compiler_try_star_except(struct compiler *c, stmt_ty s)
 
         if (i == n - 1) {
             /* Add exc to the list (if not None it's the unhandled part of the EG) */
-            ADDOP(c, POP_TOP);
-            ADDOP_I(c, LIST_APPEND, 2);
-            ADDOP(c, POP_TOP);
+            ADDOP_I(c, LIST_APPEND, 1);
             ADDOP_JUMP(c, JUMP_FORWARD, reraise_star);
         }
     }
@@ -3690,8 +3663,6 @@ compiler_try_star_except(struct compiler *c, stmt_ty s)
     /* Nothing to reraise - pop it */
     ADDOP(c, POP_TOP);
     ADDOP(c, POP_TOP);
-    ADDOP(c, POP_TOP);
-    ADDOP(c, POP_TOP);
     ADDOP(c, POP_BLOCK);
     ADDOP(c, POP_EXCEPT);
     ADDOP_JUMP(c, JUMP_FORWARD, end);
@@ -5449,13 +5420,11 @@ compiler_with_except_finish(struct compiler *c, basicblock * cleanup) {
         return 0;
     ADDOP_JUMP(c, POP_JUMP_IF_TRUE, exit);
     NEXT_BLOCK(c);
-    ADDOP_I(c, RERAISE, 4);
+    ADDOP_I(c, RERAISE, 2);
     compiler_use_next_block(c, cleanup);
     ADDOP(c, POP_EXCEPT_AND_RERAISE);
     compiler_use_next_block(c, exit);
-    ADDOP(c, POP_TOP);
-    ADDOP(c, POP_TOP);
-    ADDOP(c, POP_TOP);
+    ADDOP(c, POP_TOP); /* exc_value */
     ADDOP(c, POP_BLOCK);
     ADDOP(c, POP_EXCEPT);
     ADDOP(c, POP_TOP);
@@ -5587,7 +5556,7 @@ compiler_async_with(struct compiler *c, stmt_ty s, int pos)
     E:  WITH_EXCEPT_START (calls EXPR.__exit__)
         POP_JUMP_IF_TRUE T:
         RERAISE
-    T:  POP_TOP * 3 (remove exception from stack)
+    T:  POP_TOP (remove exception from stack)
         POP_EXCEPT
         POP_TOP
     EXIT:
@@ -7368,7 +7337,10 @@ assemble_emit_exception_table_entry(struct assembler *a, int start, int end, bas
     int size = end-start;
     assert(end > start);
     int target = handler->b_offset;
-    int depth = handler->b_preserve_lasti ? handler->b_startdepth-4 : handler->b_startdepth-3;
+    int depth = handler->b_startdepth - 1;
+    if (handler->b_preserve_lasti) {
+        depth -= 1;
+    }
     assert(depth >= 0);
     int depth_lasti = (depth<<1) | handler->b_preserve_lasti;
     assemble_emit_exception_table_item(a, start, (1<<7));
diff --git a/Python/errors.c b/Python/errors.c
index 5be15e54db..6c5fe41142 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -84,11 +84,8 @@ _PyErr_GetTopmostException(PyThreadState *tstate)
     while ((exc_info->exc_value == NULL || exc_info->exc_value == Py_None) &&
            exc_info->previous_item != NULL)
     {
-        assert(exc_info->exc_type == NULL || exc_info->exc_type == Py_None);
         exc_info = exc_info->previous_item;
     }
-    assert(exc_info->previous_item == NULL ||
-           (exc_info->exc_type != NULL && exc_info->exc_type != Py_None));
     return exc_info;
 }
 
@@ -524,27 +521,17 @@ PyErr_GetExcInfo(PyObject **p_type, PyObject **p_value, PyObject **p_traceback)
 void
 PyErr_SetExcInfo(PyObject *type, PyObject *value, PyObject *traceback)
 {
-    PyObject *oldtype, *oldvalue, *oldtraceback;
     PyThreadState *tstate = _PyThreadState_GET();
 
-    oldtype = tstate->exc_info->exc_type;
-    oldvalue = tstate->exc_info->exc_value;
-    oldtraceback = tstate->exc_info->exc_traceback;
-
+    PyObject *oldvalue = tstate->exc_info->exc_value;
 
-    tstate->exc_info->exc_type = get_exc_type(value);
-    Py_XINCREF(tstate->exc_info->exc_type);
     tstate->exc_info->exc_value = value;
-    tstate->exc_info->exc_traceback = get_exc_traceback(value);
-    Py_XINCREF(tstate->exc_info->exc_traceback);
 
     /* These args are no longer used, but we still need to steal a ref */
     Py_XDECREF(type);
     Py_XDECREF(traceback);
 
-    Py_XDECREF(oldtype);
     Py_XDECREF(oldvalue);
-    Py_XDECREF(oldtraceback);
 }
 
 
@@ -629,9 +616,6 @@ _PyErr_ChainStackItem(_PyErr_StackItem *exc_info)
         exc_info_given = 1;
     }
 
-    assert( (exc_info->exc_type == NULL || exc_info->exc_type == Py_None) ==
-            (exc_info->exc_value == NULL || exc_info->exc_value == Py_None) );
-
     if (exc_info->exc_value == NULL || exc_info->exc_value == Py_None) {
         return;
     }
diff --git a/Python/pystate.c b/Python/pystate.c
index 463b248f22..0301ce6769 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -1028,9 +1028,7 @@ PyThreadState_Clear(PyThreadState *tstate)
     Py_CLEAR(tstate->curexc_value);
     Py_CLEAR(tstate->curexc_traceback);
 
-    Py_CLEAR(tstate->exc_state.exc_type);
     Py_CLEAR(tstate->exc_state.exc_value);
-    Py_CLEAR(tstate->exc_state.exc_traceback);
 
     /* The stack of exception states should contain just this thread. */
     if (verbose && tstate->exc_info != &tstate->exc_state) {