disallow __class__ assignment for objects with different slots

Author: timfel

graalpython/com.oracle.graal.python.test/src/tests/test_mro.py

@@ -184,3 +184,25 @@ def __init__(self):
     assert x._local__impl == 1
 
     assert X.__dict__["_local__impl"].__get__(x, type(x)) == 1
+
+
+def test_class_with_slots_assignment():
+    class X():
+        __slots__ = "a", "b"
+
+    class Y():
+        __slots__ = "a", "b"
+
+    class Z():
+        __slots__ = "b", "c"
+
+
+    x = X()
+    x.__class__ = Y
+    assert type(x) == Y
+    try:
+        x.__class__ = Z
+    except TypeError as e:
+        assert True
+    else:
+        assert False

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/object/ObjectBuiltins.java

@@ -30,6 +30,7 @@
 import static com.oracle.graal.python.nodes.SpecialAttributeNames.__DICT__;
 import static com.oracle.graal.python.nodes.SpecialAttributeNames.__MODULE__;
 import static com.oracle.graal.python.nodes.SpecialAttributeNames.__QUALNAME__;
+import static com.oracle.graal.python.nodes.SpecialAttributeNames.__SLOTS__;
 import static com.oracle.graal.python.nodes.SpecialMethodNames.RICHCMP;
 import static com.oracle.graal.python.nodes.SpecialMethodNames.__BOOL__;
 import static com.oracle.graal.python.nodes.SpecialMethodNames.__DELATTR__;
@@ -108,6 +109,10 @@ protected List<? extends NodeFactory<? extends PythonBuiltinBaseNode>> getNodeFa
     @Builtin(name = __CLASS__, minNumOfPositionalArgs = 1, maxNumOfPositionalArgs = 2, isGetter = true, isSetter = true)
     @GenerateNodeFactory
     abstract static class ClassNode extends PythonBinaryBuiltinNode {
+        @Child LookupAttributeInMRONode lookupSlotsInSelf;
+        @Child LookupAttributeInMRONode lookupSlotsInOther;
+        @Child BinaryComparisonNode slotsAreEqual;
+
         private static final String ERROR_MESSAGE = "__class__ assignment only supported for heap types or ModuleType subclasses";
 
         @Specialization(guards = "isNoValue(value)")
@@ -130,6 +135,7 @@ PythonClass setClass(@SuppressWarnings("unused") Object self, @SuppressWarnings(
         PNone setClass(PythonObject self, PythonClass value,
                         @Cached("create()") BranchProfile errorValueBranch,
                         @Cached("create()") BranchProfile errorSelfBranch,
+                        @Cached("create()") BranchProfile errorSlotsBranch,
                         @Cached("create()") GetLazyClassNode getLazyClass) {
             if (value instanceof PythonBuiltinClass || value instanceof PythonNativeClass) {
                 errorValueBranch.enter();
@@ -140,10 +146,42 @@ PNone setClass(PythonObject self, PythonClass value,
                 errorSelfBranch.enter();
                 throw raise(TypeError, ERROR_MESSAGE);
             }
+            Object selfSlots = getLookupSlotsInSelf().execute(lazyClass);
+            if (selfSlots != PNone.NO_VALUE) {
+                Object otherSlots = getLookupSlotsInOther().execute(value);
+                if (otherSlots == PNone.NO_VALUE || !getSlotsAreEqual().executeBool(selfSlots, otherSlots)) {
+                    errorSlotsBranch.enter();
+                    throw raise(TypeError, "__class__ assignment: '%s' object layout differs from '%s'", value.getName(), lazyClass.getName());
+                }
+            }
             self.setLazyPythonClass(value);
             return PNone.NONE;
         }
 
+        private BinaryComparisonNode getSlotsAreEqual() {
+            if (slotsAreEqual == null) {
+                CompilerDirectives.transferToInterpreterAndInvalidate();
+                slotsAreEqual = insert(BinaryComparisonNode.create(__EQ__, null, "=="));
+            }
+            return slotsAreEqual;
+        }
+
+        private LookupAttributeInMRONode getLookupSlotsInSelf() {
+            if (lookupSlotsInSelf == null) {
+                CompilerDirectives.transferToInterpreterAndInvalidate();
+                lookupSlotsInSelf = insert(LookupAttributeInMRONode.create(__SLOTS__));
+            }
+            return lookupSlotsInSelf;
+        }
+
+        private LookupAttributeInMRONode getLookupSlotsInOther() {
+            if (lookupSlotsInOther == null) {
+                CompilerDirectives.transferToInterpreterAndInvalidate();
+                lookupSlotsInOther = insert(LookupAttributeInMRONode.create(__SLOTS__));
+            }
+            return lookupSlotsInOther;
+        }
+
         @Specialization(guards = "!isPythonObject(self)")
         PythonClass getClass(@SuppressWarnings("unused") Object self, @SuppressWarnings("unused") PythonClass value) {
             throw raise(TypeError, ERROR_MESSAGE);

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/SpecialAttributeNames.java

@@ -68,7 +68,7 @@ public abstract class SpecialAttributeNames {
     public static final String __CONTEXT__ = "__context__";
     public static final String __BASICSIZE__ = "__basicsize__";
     public static final String __NEW__ = "__new__";
-    public static final Object __SLOTS__ = "__slots__";
+    public static final String __SLOTS__ = "__slots__";
     public static final String __DICTOFFSET__ = "__dictoffset__";
     public static final String __ITEMSIZE__ = "__itemsize__";
 }