small fixes

src/capi/typeobject.cpp

@@ -3276,8 +3276,10 @@ void commonClassSetup(BoxedClass* cls) {
     }
 
     /* Calculate method resolution order */
-    if (mro_internal(cls) < 0)
-        throwCAPIException();
+    if (!cls->tp_mro) {
+        if (mro_internal(cls) < 0)
+            throwCAPIException();
+    }
 
     if (cls->tp_base)
         inherit_special(cls, cls->tp_base);

src/runtime/list.cpp

@@ -748,8 +748,10 @@ Box* listIAdd(BoxedList* self, Box* _rhs) {
         int s1 = self->size;
         int s2 = rhs->size;
 
-        if (s2 == 0)
+        if (s2 == 0) {
+            Py_INCREF(self);
             return self;
+        }
 
         self->ensure(s1 + s2);
 
@@ -769,8 +771,10 @@ Box* listIAdd(BoxedList* self, Box* _rhs) {
         int s1 = self->size;
         int s2 = rhs->ob_size;
 
-        if (s2 == 0)
+        if (s2 == 0) {
+            Py_INCREF(self);
             return self;
+        }
 
         self->ensure(s1 + s2);
 

src/runtime/util.cpp

@@ -133,7 +133,10 @@ extern "C" void dumpEx(void* p, int levels) {
     printf("\n");
     printf("Raw address: %p\n", p);
 
-    if ((((intptr_t)p) & 0x7) == 0) {
+    if ((intptr_t)p < 0x1000){
+        if (p != NULL)
+            printf("Not a real pointer?\n");
+    } else if ((((intptr_t)p) & 0x7) == 0) {
         uint8_t lowbyte = *reinterpret_cast<uint8_t*>(p);
         if (lowbyte == 0xcb) {
             printf("Uninitialized memory\n");