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

Only AttributeError should be silenced.

Author: serhiy-storchaka

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

@@ -0,0 +1,2 @@
+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

@@ -1313,14 +1313,17 @@ 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;
     }
 
     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);
     }