gh-75646: allow _PyType_Lookup() to raise exceptions

Include/object.h

@@ -501,8 +501,8 @@ PyAPI_FUNC(PyObject *) PyType_GenericAlloc(PyTypeObject *, Py_ssize_t);
 PyAPI_FUNC(PyObject *) PyType_GenericNew(PyTypeObject *,
                                                PyObject *, PyObject *);
 #ifndef Py_LIMITED_API
-PyAPI_FUNC(PyObject *) _PyType_Lookup(PyTypeObject *, PyObject *);
-PyAPI_FUNC(PyObject *) _PyType_LookupId(PyTypeObject *, _Py_Identifier *);
+PyAPI_FUNC(PyObject *) _PyType_Lookup(PyTypeObject *, PyObject *, int *);
+PyAPI_FUNC(PyObject *) _PyType_LookupId(PyTypeObject *, _Py_Identifier *, int *);
 PyAPI_FUNC(PyObject *) _PyObject_LookupSpecial(PyObject *, _Py_Identifier *);
 PyAPI_FUNC(PyTypeObject *) _PyType_CalculateMetaclass(PyTypeObject *, PyObject *);
 #endif

Misc/NEWS.d/next/Core and Builtins/2017-09-13-12-04-23.bpo-31336.gi2ahY.rst

@@ -0,0 +1,2 @@
+Speed up class creation by 10-20% by reducing the overhead in the
+necessary special method lookups.  Patch by Stefan Behnel.

Modules/_collectionsmodule.c

@@ -2257,6 +2257,7 @@ _count_elements(PyObject *self, PyObject *args)
     PyObject *dict_get;
     PyObject *mapping_setitem;
     PyObject *dict_setitem;
+    int error;
 
     if (!PyArg_UnpackTuple(args, "_count_elements", 2, 2, &mapping, &iterable))
         return NULL;
@@ -2268,10 +2269,22 @@ _count_elements(PyObject *self, PyObject *args)
     /* Only take the fast path when get() and __setitem__()
      * have not been overridden.
      */
-    mapping_get = _PyType_LookupId(Py_TYPE(mapping), &PyId_get);
-    dict_get = _PyType_LookupId(&PyDict_Type, &PyId_get);
-    mapping_setitem = _PyType_LookupId(Py_TYPE(mapping), &PyId___setitem__);
-    dict_setitem = _PyType_LookupId(&PyDict_Type, &PyId___setitem__);
+    mapping_get = _PyType_LookupId(Py_TYPE(mapping), &PyId_get, &error);
+    if (error == -1) {
+        goto done;
+    }
+    dict_get = _PyType_LookupId(&PyDict_Type, &PyId_get, &error);
+    if (error == -1) {
+        goto done;
+    }
+    mapping_setitem = _PyType_LookupId(Py_TYPE(mapping), &PyId___setitem__, &error);
+    if (error == -1) {
+        goto done;
+    }
+    dict_setitem = _PyType_LookupId(&PyDict_Type, &PyId___setitem__, &error);
+    if (error == -1) {
+        goto done;
+    }
 
     if (mapping_get != NULL && mapping_get == dict_get &&
         mapping_setitem != NULL && mapping_setitem == dict_setitem) {

Modules/_lsprof.c

@@ -199,9 +199,10 @@ normalizeUserObj(PyObject *obj)
         PyObject *self = fn->m_self;
         PyObject *name = PyUnicode_FromString(fn->m_ml->ml_name);
         PyObject *modname = fn->m_module;
+        int ignore;
 
         if (name != NULL) {
-            PyObject *mo = _PyType_Lookup(Py_TYPE(self), name);
+            PyObject *mo = _PyType_Lookup(Py_TYPE(self), name, &ignore);
             Py_XINCREF(mo);
             Py_DECREF(name);
             if (mo != NULL) {

Objects/bytesobject.c

@@ -567,6 +567,8 @@ format_obj(PyObject *v, const char **pbuf, Py_ssize_t *plen)
         *pbuf = PyBytes_AS_STRING(result);
         *plen = PyBytes_GET_SIZE(result);
         return result;
+    } else if (PyErr_Occurred()) {
+        return NULL;
     }
     /* does it support buffer protocol? */
     if (PyObject_CheckBuffer(v)) {

Objects/classobject.c

@@ -138,13 +138,14 @@ method_getattro(PyObject *obj, PyObject *name)
     PyMethodObject *im = (PyMethodObject *)obj;
     PyTypeObject *tp = obj->ob_type;
     PyObject *descr = NULL;
+    int error;
 
     {
         if (tp->tp_dict == NULL) {
             if (PyType_Ready(tp) < 0)
                 return NULL;
         }
-        descr = _PyType_Lookup(tp, name);
+        descr = _PyType_Lookup(tp, name, &error);
     }
 
     if (descr != NULL) {
@@ -155,6 +156,8 @@ method_getattro(PyObject *obj, PyObject *name)
             Py_INCREF(descr);
             return descr;
         }
+    } else if (error == -1) {
+        return NULL;
     }
 
     return PyObject_GetAttr(im->im_func, name);
@@ -462,12 +465,13 @@ instancemethod_getattro(PyObject *self, PyObject *name)
 {
     PyTypeObject *tp = self->ob_type;
     PyObject *descr = NULL;
+    int error;
 
     if (tp->tp_dict == NULL) {
         if (PyType_Ready(tp) < 0)
             return NULL;
     }
-    descr = _PyType_Lookup(tp, name);
+    descr = _PyType_Lookup(tp, name, &error);
 
     if (descr != NULL) {
         descrgetfunc f = TP_DESCR_GET(descr->ob_type);
@@ -477,6 +481,8 @@ instancemethod_getattro(PyObject *self, PyObject *name)
             Py_INCREF(descr);
             return descr;
         }
+    } else if (error == -1) {
+        return NULL;
     }
 
     return PyObject_GetAttr(PyInstanceMethod_GET_FUNCTION(self), name);

Objects/object.c

@@ -1043,6 +1043,7 @@ _PyObject_GetMethod(PyObject *obj, PyObject *name, PyObject **method)
     PyObject **dictptr, *dict;
     PyObject *attr;
     int meth_found = 0;
+    int error;
 
     assert(*method == NULL);
 
@@ -1055,7 +1056,7 @@ _PyObject_GetMethod(PyObject *obj, PyObject *name, PyObject **method)
     if (tp->tp_dict == NULL && PyType_Ready(tp) < 0)
         return 0;
 
-    descr = _PyType_Lookup(tp, name);
+    descr = _PyType_Lookup(tp, name, &error);
     if (descr != NULL) {
         Py_INCREF(descr);
         if (PyFunction_Check(descr) ||
@@ -1069,6 +1070,8 @@ _PyObject_GetMethod(PyObject *obj, PyObject *name, PyObject **method)
                 return 0;
             }
         }
+    } else if (error == -1) {
+        return 0;
     }
 
     dictptr = _PyObject_GetDictPtr(obj);
@@ -1122,6 +1125,7 @@ _PyObject_GenericGetAttrWithDict(PyObject *obj, PyObject *name, PyObject *dict)
     descrgetfunc f;
     Py_ssize_t dictoffset;
     PyObject **dictptr;
+    int error;
 
     if (!PyUnicode_Check(name)){
         PyErr_Format(PyExc_TypeError,
@@ -1136,7 +1140,7 @@ _PyObject_GenericGetAttrWithDict(PyObject *obj, PyObject *name, PyObject *dict)
             goto done;
     }
 
-    descr = _PyType_Lookup(tp, name);
+    descr = _PyType_Lookup(tp, name, &error);
 
     f = NULL;
     if (descr != NULL) {
@@ -1146,6 +1150,8 @@ _PyObject_GenericGetAttrWithDict(PyObject *obj, PyObject *name, PyObject *dict)
             res = f(descr, obj, (PyObject *)obj->ob_type);
             goto done;
         }
+    } else if (error == -1) {
+        goto done;
     }
 
     if (dict == NULL) {
@@ -1216,6 +1222,7 @@ _PyObject_GenericSetAttrWithDict(PyObject *obj, PyObject *name,
     descrsetfunc f;
     PyObject **dictptr;
     int res = -1;
+    int error;
 
     if (!PyUnicode_Check(name)){
         PyErr_Format(PyExc_TypeError,
@@ -1229,7 +1236,7 @@ _PyObject_GenericSetAttrWithDict(PyObject *obj, PyObject *name,
 
     Py_INCREF(name);
 
-    descr = _PyType_Lookup(tp, name);
+    descr = _PyType_Lookup(tp, name, &error);
 
     if (descr != NULL) {
         Py_INCREF(descr);
@@ -1238,6 +1245,8 @@ _PyObject_GenericSetAttrWithDict(PyObject *obj, PyObject *name,
             res = f(descr, obj, value);
             goto done;
         }
+    } else if (error == -1) {
+        goto done;
     }
 
     if (dict == NULL) {