add delattrGeneric

like we had to do for getattrGeneric and setattrGeneric

I guess all the other slots will eventually follow as well.

src/capi/object.cpp

@@ -145,6 +145,9 @@ extern "C" PyObject* PyObject_SelfIter(PyObject* obj) noexcept {
 
 extern "C" int PyObject_GenericSetAttr(PyObject* obj, PyObject* name, PyObject* value) noexcept {
     try {
+        if (value == NULL)
+            delattrGeneric(obj, static_cast<BoxedString*>(name)->s, NULL);
+        else
             setattrGeneric(obj, static_cast<BoxedString*>(name)->s.c_str(), value, NULL);
     } catch (ExcInfo e) {
         setCAPIException(e);

src/runtime/objmodel.cpp

@@ -1682,6 +1682,7 @@ bool dataDescriptorSetSpecialCases(Box* obj, Box* val, Box* descr, SetattrRewrit
 }
 
 void setattrGeneric(Box* obj, const std::string& attr, Box* val, SetattrRewriteArgs* rewrite_args) {
+    assert(val);
     assert(gc::isValidGCObject(val));
 
     // TODO this should be in type_setattro
@@ -3652,18 +3653,7 @@ void Box::delattr(const std::string& attr, DelattrRewriteArgs* rewrite_args) {
     abort();
 }
 
-extern "C" void delattrInternal(Box* obj, const std::string& attr, bool allow_custom,
-                                DelattrRewriteArgs* rewrite_args) {
-    // custom __delattr__
-    if (allow_custom) {
-        Box* delAttr = typeLookup(obj->cls, delattr_str, NULL);
-        if (delAttr != NULL) {
-            Box* boxstr = boxString(attr);
-            Box* rtn = runtimeCall2(delAttr, ArgPassSpec(2), obj, boxstr);
-            return;
-        }
-    }
-
+extern "C" void delattrGeneric(Box* obj, const std::string& attr, DelattrRewriteArgs* rewrite_args) {
     // first check whether the deleting attribute is a descriptor
     Box* clsAttr = typeLookup(obj->cls, attr, NULL);
     if (clsAttr != NULL) {
@@ -3715,6 +3705,17 @@ extern "C" void delattrInternal(Box* obj, const std::string& attr, bool allow_cu
     }
 }
 
+extern "C" void delattrInternal(Box* obj, const std::string& attr, DelattrRewriteArgs* rewrite_args) {
+    Box* delAttr = typeLookup(obj->cls, delattr_str, NULL);
+    if (delAttr != NULL) {
+        Box* boxstr = boxString(attr);
+        Box* rtn = runtimeCall2(delAttr, ArgPassSpec(2), obj, boxstr);
+        return;
+    }
+
+    delattrGeneric(obj, attr, rewrite_args);
+}
+
 // del target.attr
 extern "C" void delattr(Box* obj, const char* attr) {
     static StatCounter slowpath_delattr("slowpath_delattr");
@@ -3728,7 +3729,7 @@ extern "C" void delattr(Box* obj, const char* attr) {
     }
 
 
-    delattrInternal(obj, attr, true, NULL);
+    delattrInternal(obj, attr, NULL);
 }
 
 extern "C" Box* createBoxedIterWrapper(Box* o) {

src/runtime/objmodel.h

@@ -51,6 +51,7 @@ extern "C" void my_assert(bool b);
 extern "C" Box* getattr(Box* obj, const char* attr);
 extern "C" void setattr(Box* obj, const char* attr, Box* attr_val);
 extern "C" void delattr(Box* obj, const char* attr);
+extern "C" void delattrGeneric(Box* obj, const std::string& attr, DelattrRewriteArgs* rewrite_args);
 extern "C" bool nonzero(Box* obj);
 extern "C" Box* runtimeCall(Box*, ArgPassSpec, Box*, Box*, Box*, Box**, const std::vector<const std::string*>*);
 extern "C" Box* callattr(Box*, const std::string*, CallattrFlags, ArgPassSpec, Box*, Box*, Box*, Box**,

test/tests/object_default_behavior.py

 class C(object):
+    def __delattr__(self, attr):
+        print "delattr", attr
+        if attr.startswith("c"):
+            print "yum"
+        else:
+            object.__delattr__(self, attr)
+
     def __setattr__(self, attr, value):
         print attr, value
         if attr.startswith("c"):
@@ -18,3 +25,8 @@ c.b = 2
 c.c = 3
 print sorted(c.__dict__.items())
 print c.a, c.b, c.c
+
+del c.a
+del c.b
+del c.c
+print sorted(c.__dict__.items())