bpo-37994: Fix silencing all errors if an attribute lookup fails. (GH-15630)

Only AttributeError should be silenced.

Misc/NEWS.d/next/Core and Builtins/2019-08-31-11-13-25.bpo-37994.Rj6S4j.rst

+Fixed silencing arbitrary errors if an attribute lookup fails in several
+sites. Only AttributeError should be silenced.

Modules/_csv.c

@@ -1382,7 +1382,10 @@ csv_writer(PyObject *module, PyObject *args, PyObject *keyword_args)
         Py_DECREF(self);
         return NULL;
     }
-    self->write = _PyObject_GetAttrId(output_file, &PyId_write);
+    if (_PyObject_LookupAttrId(output_file, &PyId_write, &self->write) < 0) {
+        Py_DECREF(self);
+        return NULL;
+    }
     if (self->write == NULL || !PyCallable_Check(self->write)) {
         PyErr_SetString(PyExc_TypeError,
                         "argument 1 must have a \"write\" method");

Modules/_datetimemodule.c

@@ -3607,24 +3607,24 @@ tzinfo_reduce(PyObject *self, PyObject *Py_UNUSED(ignored))
     _Py_IDENTIFIER(__getinitargs__);
     _Py_IDENTIFIER(__getstate__);
 
-    getinitargs = _PyObject_GetAttrId(self, &PyId___getinitargs__);
+    if (_PyObject_LookupAttrId(self, &PyId___getinitargs__, &getinitargs) < 0) {
+        return NULL;
+    }
     if (getinitargs != NULL) {
         args = PyObject_CallNoArgs(getinitargs);
         Py_DECREF(getinitargs);
-        if (args == NULL) {
-            return NULL;
-        }
     }
     else {
-        PyErr_Clear();
-
         args = PyTuple_New(0);
-        if (args == NULL) {
-            return NULL;
-        }
+    }
+    if (args == NULL) {
+        return NULL;
     }
 
-    getstate = _PyObject_GetAttrId(self, &PyId___getstate__);
+    if (_PyObject_LookupAttrId(self, &PyId___getstate__, &getstate) < 0) {
+        Py_DECREF(args);
+        return NULL;
+    }
     if (getstate != NULL) {
         state = PyObject_CallNoArgs(getstate);
         Py_DECREF(getstate);
@@ -3635,7 +3635,6 @@ tzinfo_reduce(PyObject *self, PyObject *Py_UNUSED(ignored))
     }
     else {
         PyObject **dictptr;
-        PyErr_Clear();
         state = Py_None;
         dictptr = _PyObject_GetDictPtr(self);
         if (dictptr && *dictptr && PyDict_GET_SIZE(*dictptr)) {

Modules/_pickle.c

@@ -4383,7 +4383,6 @@ save(PicklerObject *self, PyObject *obj, int pers_save)
         _Py_IDENTIFIER(__reduce__);
         _Py_IDENTIFIER(__reduce_ex__);
 
-
         /* XXX: If the __reduce__ method is defined, __reduce_ex__ is
            automatically defined as __reduce__. While this is convenient, this
            make it impossible to know which method was actually called. Of
@@ -4404,14 +4403,15 @@ save(PicklerObject *self, PyObject *obj, int pers_save)
             }
         }
         else {
-            PickleState *st = _Pickle_GetGlobalState();
-
             /* Check for a __reduce__ method. */
-            reduce_func = _PyObject_GetAttrId(obj, &PyId___reduce__);
+            if (_PyObject_LookupAttrId(obj, &PyId___reduce__, &reduce_func) < 0) {
+                goto error;
+            }
             if (reduce_func != NULL) {
                 reduce_value = PyObject_CallNoArgs(reduce_func);
             }
             else {
+                PickleState *st = _Pickle_GetGlobalState();
                 PyErr_Format(st->PicklingError,
                              "can't pickle '%.200s' object: %R",
                              type->tp_name, obj);
@@ -6446,7 +6446,9 @@ do_append(UnpicklerObject *self, Py_ssize_t x)
         PyObject *extend_func;
         _Py_IDENTIFIER(extend);
 
-        extend_func = _PyObject_GetAttrId(list, &PyId_extend);
+        if (_PyObject_LookupAttrId(list, &PyId_extend, &extend_func) < 0) {
+            return -1;
+        }
         if (extend_func != NULL) {
             slice = Pdata_poplist(self->stack, x);
             if (!slice) {
@@ -6466,7 +6468,6 @@ do_append(UnpicklerObject *self, Py_ssize_t x)
             /* Even if the PEP 307 requires extend() and append() methods,
                fall back on append() if the object has no extend() method
                for backward compatibility. */
-            PyErr_Clear();
             append_func = _PyObject_GetAttrId(list, &PyId_append);
             if (append_func == NULL)
                 return -1;

Modules/_threadmodule.c

@@ -1313,6 +1313,7 @@ static int
 thread_excepthook_file(PyObject *file, PyObject *exc_type, PyObject *exc_value,
                        PyObject *exc_traceback, PyObject *thread)
 {
+    _Py_IDENTIFIER(name);
     /* print(f"Exception in thread {thread.name}:", file=file) */
     if (PyFile_WriteString("Exception in thread ", file) < 0) {
         return -1;
@@ -1320,7 +1321,9 @@ thread_excepthook_file(PyObject *file, PyObject *exc_type, PyObject *exc_value,
 
     PyObject *name = NULL;
     if (thread != Py_None) {
-        name = PyObject_GetAttrString(thread, "name");
+        if (_PyObject_LookupAttrId(thread, &PyId_name, &name) < 0) {
+            return -1;
+        }
     }
     if (name != NULL) {
         if (PyFile_WriteObject(name, file, Py_PRINT_RAW) < 0) {
@@ -1330,8 +1333,6 @@ thread_excepthook_file(PyObject *file, PyObject *exc_type, PyObject *exc_value,
         Py_DECREF(name);
     }
     else {
-        PyErr_Clear();
-
         unsigned long ident = PyThread_get_thread_ident();
         PyObject *str = PyUnicode_FromFormat("%lu", ident);
         if (str != NULL) {

Modules/pyexpat.c

@@ -810,7 +810,9 @@ pyexpat_xmlparser_ParseFile(xmlparseobject *self, PyObject *file)
     PyObject *readmethod = NULL;
     _Py_IDENTIFIER(read);
 
-    readmethod = _PyObject_GetAttrId(file, &PyId_read);
+    if (_PyObject_LookupAttrId(file, &PyId_read, &readmethod) < 0) {
+        return NULL;
+    }
     if (readmethod == NULL) {
         PyErr_SetString(PyExc_TypeError,
                         "argument must have 'read' attribute");

Objects/bytearrayobject.c

@@ -2061,9 +2061,10 @@ _common_reduce(PyByteArrayObject *self, int proto)
     _Py_IDENTIFIER(__dict__);
     char *buf;
 
-    dict = _PyObject_GetAttrId((PyObject *)self, &PyId___dict__);
+    if (_PyObject_LookupAttrId((PyObject *)self, &PyId___dict__, &dict) < 0) {
+        return NULL;
+    }
     if (dict == NULL) {
-        PyErr_Clear();
         dict = Py_None;
         Py_INCREF(dict);
     }

Objects/descrobject.c

@@ -1616,29 +1616,25 @@ property_init_impl(propertyobject *self, PyObject *fget, PyObject *fset,
     /* if no docstring given and the getter has one, use that one */
     if ((doc == NULL || doc == Py_None) && fget != NULL) {
         _Py_IDENTIFIER(__doc__);
-        PyObject *get_doc = _PyObject_GetAttrId(fget, &PyId___doc__);
-        if (get_doc) {
-            if (Py_TYPE(self) == &PyProperty_Type) {
-                Py_XSETREF(self->prop_doc, get_doc);
-            }
-            else {
-                /* If this is a property subclass, put __doc__
-                in dict of the subclass instance instead,
-                otherwise it gets shadowed by __doc__ in the
-                class's dict. */
-                int err = _PyObject_SetAttrId((PyObject *)self, &PyId___doc__, get_doc);
-                Py_DECREF(get_doc);
-                if (err < 0)
-                    return -1;
-            }
-            self->getter_doc = 1;
+        PyObject *get_doc;
+        int rc = _PyObject_LookupAttrId(fget, &PyId___doc__, &get_doc);
+        if (rc <= 0) {
+            return rc;
         }
-        else if (PyErr_ExceptionMatches(PyExc_Exception)) {
-            PyErr_Clear();
+        if (Py_TYPE(self) == &PyProperty_Type) {
+            Py_XSETREF(self->prop_doc, get_doc);
         }
         else {
-            return -1;
+            /* If this is a property subclass, put __doc__
+               in dict of the subclass instance instead,
+               otherwise it gets shadowed by __doc__ in the
+               class's dict. */
+            int err = _PyObject_SetAttrId((PyObject *)self, &PyId___doc__, get_doc);
+            Py_DECREF(get_doc);
+            if (err < 0)
+                return -1;
         }
+        self->getter_doc = 1;
     }
 
     return 0;

Objects/fileobject.c

@@ -185,8 +185,10 @@ PyObject_AsFileDescriptor(PyObject *o)
     if (PyLong_Check(o)) {
         fd = _PyLong_AsInt(o);
     }
-    else if ((meth = _PyObject_GetAttrId(o, &PyId_fileno)) != NULL)
-    {
+    else if (_PyObject_LookupAttrId(o, &PyId_fileno, &meth) < 0) {
+        return -1;
+    }
+    else if (meth != NULL) {
         PyObject *fno = _PyObject_CallNoArg(meth);
         Py_DECREF(meth);
         if (fno == NULL)

Objects/setobject.c

@@ -1970,9 +1970,10 @@ set_reduce(PySetObject *so, PyObject *Py_UNUSED(ignored))
     args = PyTuple_Pack(1, keys);
     if (args == NULL)
         goto done;
-    dict = _PyObject_GetAttrId((PyObject *)so, &PyId___dict__);
+    if (_PyObject_LookupAttrId((PyObject *)so, &PyId___dict__, &dict) < 0) {
+        goto done;
+    }
     if (dict == NULL) {
-        PyErr_Clear();
         dict = Py_None;
         Py_INCREF(dict);
     }

Objects/typeobject.c

@@ -1551,17 +1551,10 @@ tail_contains(PyObject *tuple, int whence, PyObject *o)
 static PyObject *
 class_name(PyObject *cls)
 {
-    PyObject *name = _PyObject_GetAttrId(cls, &PyId___name__);
-    if (name == NULL) {
-        PyErr_Clear();
+    PyObject *name;
+    if (_PyObject_LookupAttrId(cls, &PyId___name__, &name) == 0) {
         name = PyObject_Repr(cls);
     }
-    if (name == NULL)
-        return NULL;
-    if (!PyUnicode_Check(name)) {
-        Py_DECREF(name);
-        return NULL;
-    }
     return name;
 }
 
@@ -1579,13 +1572,15 @@ check_duplicates(PyObject *tuple)
             if (PyTuple_GET_ITEM(tuple, j) == o) {
                 o = class_name(o);
                 if (o != NULL) {
-                    PyErr_Format(PyExc_TypeError,
-                                 "duplicate base class %U",
-                                 o);
+                    if (PyUnicode_Check(o)) {
+                        PyErr_Format(PyExc_TypeError,
+                                     "duplicate base class %U", o);
+                    }
+                    else {
+                        PyErr_SetString(PyExc_TypeError,
+                                        "duplicate base class");
+                    }
                     Py_DECREF(o);
-                } else {
-                    PyErr_SetString(PyExc_TypeError,
-                                 "duplicate base class");
                 }
                 return -1;
             }
@@ -1629,13 +1624,20 @@ consistent method resolution\norder (MRO) for bases");
     i = 0;
     while (PyDict_Next(set, &i, &k, &v) && (size_t)off < sizeof(buf)) {
         PyObject *name = class_name(k);
-        const char *name_str;
+        const char *name_str = NULL;
         if (name != NULL) {
-            name_str = PyUnicode_AsUTF8(name);
-            if (name_str == NULL)
+            if (PyUnicode_Check(name)) {
+                name_str = PyUnicode_AsUTF8(name);
+            }
+            else {
                 name_str = "?";
-        } else
-            name_str = "?";
+            }
+        }
+        if (name_str == NULL) {
+            Py_XDECREF(name);
+            Py_DECREF(set);
+            return;
+        }
         off += PyOS_snprintf(buf + off, sizeof(buf) - off, " %s", name_str);
         Py_XDECREF(name);
         if (--n && (size_t)(off+1) < sizeof(buf)) {
@@ -3422,10 +3424,10 @@ merge_class_dict(PyObject *dict, PyObject *aclass)
     assert(aclass);
 
     /* Merge in the type's dict (if any). */
-    classdict = _PyObject_GetAttrId(aclass, &PyId___dict__);
-    if (classdict == NULL)
-        PyErr_Clear();
-    else {
+    if (_PyObject_LookupAttrId(aclass, &PyId___dict__, &classdict) < 0) {
+        return -1;
+    }
+    if (classdict != NULL) {
         int status = PyDict_Update(dict, classdict);
         Py_DECREF(classdict);
         if (status < 0)
@@ -3433,15 +3435,17 @@ merge_class_dict(PyObject *dict, PyObject *aclass)
     }
 
     /* Recursively merge in the base types' (if any) dicts. */
-    bases = _PyObject_GetAttrId(aclass, &PyId___bases__);
-    if (bases == NULL)
-        PyErr_Clear();
-    else {
+    if (_PyObject_LookupAttrId(aclass, &PyId___bases__, &bases) < 0) {
+        return -1;
+    }
+    if (bases != NULL) {
         /* We have no guarantee that bases is a real tuple */
         Py_ssize_t i, n;
         n = PySequence_Size(bases); /* This better be right */
-        if (n < 0)
-            PyErr_Clear();
+        if (n < 0) {
+            Py_DECREF(bases);
+            return -1;
+        }
         else {
             for (i = 0; i < n; i++) {
                 int status;
@@ -4730,9 +4734,10 @@ object___dir___impl(PyObject *self)
     PyObject *itsclass = NULL;
 
     /* Get __dict__ (which may or may not be a real dict...) */
-    dict = _PyObject_GetAttrId(self, &PyId___dict__);
+    if (_PyObject_LookupAttrId(self, &PyId___dict__, &dict) < 0) {
+        return NULL;
+    }
     if (dict == NULL) {
-        PyErr_Clear();
         dict = PyDict_New();
     }
     else if (!PyDict_Check(dict)) {
@@ -4750,12 +4755,12 @@ object___dir___impl(PyObject *self)
         goto error;
 
     /* Merge in attrs reachable from its class. */
-    itsclass = _PyObject_GetAttrId(self, &PyId___class__);
-    if (itsclass == NULL)
-        /* XXX(tomer): Perhaps fall back to obj->ob_type if no
-                       __class__ exists? */
-        PyErr_Clear();
-    else if (merge_class_dict(dict, itsclass) != 0)
+    if (_PyObject_LookupAttrId(self, &PyId___class__, &itsclass) < 0) {
+        goto error;
+    }
+    /* XXX(tomer): Perhaps fall back to obj->ob_type if no
+                   __class__ exists? */
+    if (itsclass != NULL && merge_class_dict(dict, itsclass) < 0)
         goto error;
 
     result = PyDict_Keys(dict);
@@ -6111,16 +6116,19 @@ method_is_overloaded(PyObject *left, PyObject *right, struct _Py_Identifier *nam
     PyObject *a, *b;
     int ok;
 
-    b = _PyObject_GetAttrId((PyObject *)(Py_TYPE(right)), name);
+    if (_PyObject_LookupAttrId((PyObject *)(Py_TYPE(right)), name, &b) < 0) {
+        return -1;
+    }
     if (b == NULL) {
-        PyErr_Clear();
         /* If right doesn't have it, it's not overloaded */
         return 0;
     }
 
-    a = _PyObject_GetAttrId((PyObject *)(Py_TYPE(left)), name);
+    if (_PyObject_LookupAttrId((PyObject *)(Py_TYPE(left)), name, &a) < 0) {
+        Py_DECREF(b);
+        return -1;
+    }
     if (a == NULL) {
-        PyErr_Clear();
         Py_DECREF(b);
         /* If right has it but left doesn't, it's overloaded */
         return 1;
@@ -6129,11 +6137,6 @@ method_is_overloaded(PyObject *left, PyObject *right, struct _Py_Identifier *nam
     ok = PyObject_RichCompareBool(a, b, Py_NE);
     Py_DECREF(a);
     Py_DECREF(b);
-    if (ok < 0) {
-        PyErr_Clear();
-        return 0;
-    }
-
     return ok;
 }
 
@@ -6151,16 +6154,20 @@ FUNCNAME(PyObject *self, PyObject *other) \
     if (Py_TYPE(self)->tp_as_number != NULL && \
         Py_TYPE(self)->tp_as_number->SLOTNAME == TESTFUNC) { \
         PyObject *r; \
-        if (do_other && \
-            PyType_IsSubtype(Py_TYPE(other), Py_TYPE(self)) && \
-            method_is_overloaded(self, other, &rop_id)) { \
-            stack[0] = other; \
-            stack[1] = self; \
-            r = vectorcall_maybe(&rop_id, stack, 2); \
-            if (r != Py_NotImplemented) \
-                return r; \
-            Py_DECREF(r); \
-            do_other = 0; \
+        if (do_other && PyType_IsSubtype(Py_TYPE(other), Py_TYPE(self))) { \
+            int ok = method_is_overloaded(self, other, &rop_id); \
+            if (ok < 0) { \
+                return NULL; \
+            } \
+            if (ok) { \
+                stack[0] = other; \
+                stack[1] = self; \
+                r = vectorcall_maybe(&rop_id, stack, 2); \
+                if (r != Py_NotImplemented) \
+                    return r; \
+                Py_DECREF(r); \
+                do_other = 0; \
+            } \
         } \
         stack[0] = self; \
         stack[1] = other; \
@@ -7753,7 +7760,9 @@ supercheck(PyTypeObject *type, PyObject *obj)
         /* Try the slow way */
         PyObject *class_attr;
 
-        class_attr = _PyObject_GetAttrId(obj, &PyId___class__);
+        if (_PyObject_LookupAttrId(obj, &PyId___class__, &class_attr) < 0) {
+            return NULL;
+        }
         if (class_attr != NULL &&
             PyType_Check(class_attr) &&
             (PyTypeObject *)class_attr != Py_TYPE(obj))
@@ -7763,11 +7772,7 @@ supercheck(PyTypeObject *type, PyObject *obj)
             if (ok)
                 return (PyTypeObject *)class_attr;
         }
-
-        if (class_attr == NULL)
-            PyErr_Clear();
-        else
-            Py_DECREF(class_attr);
+        Py_XDECREF(class_attr);
     }
 
     PyErr_SetString(PyExc_TypeError,

Objects/weakrefobject.c

@@ -163,10 +163,10 @@ weakref_repr(PyWeakReference *self)
     if (PyWeakref_GET_OBJECT(self) == Py_None)
         return PyUnicode_FromFormat("<weakref at %p; dead>", self);
 
-    name = _PyObject_GetAttrId(PyWeakref_GET_OBJECT(self), &PyId___name__);
+    if (_PyObject_LookupAttrId(PyWeakref_GET_OBJECT(self), &PyId___name__, &name) < 0) {
+        return NULL;
+    }
     if (name == NULL || !PyUnicode_Check(name)) {
-        if (name == NULL)
-            PyErr_Clear();
         repr = PyUnicode_FromFormat(
             "<weakref at %p; to '%s' at %p>",
             self,

Python/bltinmodule.c

@@ -2255,16 +2255,12 @@ builtin_vars(PyObject *self, PyObject *args)
         return NULL;
     if (v == NULL) {
         d = PyEval_GetLocals();
-        if (d == NULL)
-            return NULL;
-        Py_INCREF(d);
+        Py_XINCREF(d);
     }
     else {
-        d = _PyObject_GetAttrId(v, &PyId___dict__);
-        if (d == NULL) {
+        if (_PyObject_LookupAttrId(v, &PyId___dict__, &d) == 0) {
             PyErr_SetString(PyExc_TypeError,
                 "vars() argument must have __dict__ attribute");
-            return NULL;
         }
     }
     return d;

Python/sysmodule.c

@@ -224,16 +224,12 @@ PySys_Audit(const char *event, const char *argFormat, ...)
         ts->tracing++;
         ts->use_tracing = 0;
         while ((hook = PyIter_Next(hooks)) != NULL) {
+            _Py_IDENTIFIER(__cantrace__);
             PyObject *o;
-            int canTrace = -1;
-            o = PyObject_GetAttrString(hook, "__cantrace__");
+            int canTrace = _PyObject_LookupAttrId(hook, &PyId___cantrace__, &o);
             if (o) {
                 canTrace = PyObject_IsTrue(o);
                 Py_DECREF(o);
-            } else if (_PyErr_Occurred(ts) &&
-                       _PyErr_ExceptionMatches(ts, PyExc_AttributeError)) {
-                _PyErr_Clear(ts);
-                canTrace = 0;
             }
             if (canTrace < 0) {
                 break;
@@ -579,7 +575,10 @@ sys_displayhook_unencodable(PyThreadState *tstate, PyObject *outf, PyObject *o)
     if (encoded == NULL)
         goto error;
 
-    buffer = _PyObject_GetAttrId(outf, &PyId_buffer);
+    if (_PyObject_LookupAttrId(outf, &PyId_buffer, &buffer) < 0) {
+        Py_DECREF(encoded);
+        goto error;
+    }
     if (buffer) {
         result = _PyObject_CallMethodIdOneArg(buffer, &PyId_write, encoded);
         Py_DECREF(buffer);
@@ -589,7 +588,6 @@ sys_displayhook_unencodable(PyThreadState *tstate, PyObject *outf, PyObject *o)
         Py_DECREF(result);
     }
     else {
-        _PyErr_Clear(tstate);
         escaped_str = PyUnicode_FromEncodedObject(encoded,
                                                   stdout_encoding_str,
                                                   "strict");