Add instance.tp_setattro

src/runtime/classobj.cpp

@@ -250,6 +250,8 @@ Box* instanceSetattr(Box* _inst, Box* _attr, Box* value) {
     RELEASE_ASSERT(_attr->cls == str_cls, "");
     BoxedString* attr = static_cast<BoxedString*>(_attr);
 
+    assert(value);
+
     // These are special cases in CPython as well:
     if (attr->s[0] == '_' && attr->s[1] == '_') {
         if (attr->s == "__dict__")
@@ -276,6 +278,20 @@ Box* instanceSetattr(Box* _inst, Box* _attr, Box* value) {
     return None;
 }
 
+static int instance_setattro(Box* cls, Box* attr, Box* value) noexcept {
+    try {
+        if (value) {
+            instanceSetattr(cls, attr, value);
+            return 0;
+        } else {
+            RELEASE_ASSERT(0, "");
+        }
+    } catch (ExcInfo e) {
+        setCAPIException(e);
+        return -1;
+    }
+}
+
 Box* instanceRepr(Box* _inst) {
     RELEASE_ASSERT(_inst->cls == instance_cls, "");
     BoxedInstance* inst = static_cast<BoxedInstance*>(_inst);
@@ -454,5 +470,6 @@ void setupClassobj() {
 
     instance_cls->freeze();
     instance_cls->tp_getattro = instance_getattro;
+    instance_cls->tp_setattro = instance_setattro;
 }
 }

src/runtime/objmodel.cpp

@@ -549,15 +549,18 @@ Box* Box::getattr(const std::string& attr, GetattrRewriteArgs* rewrite_args) {
     if (rewrite_args)
         rewrite_args->obj->addAttrGuard(BOX_CLS_OFFSET, (intptr_t)cls);
 
-// if (attr == "__setattr__" && !rewrite_args)
-// printf("");
-
 #if 0
     if (attr[0] == '_' && attr[1] == '_') {
+        // Only do this logging for potentially-avoidable cases:
+        if (!rewrite_args && cls != classobj_cls) {
+            if (attr == "__setattr__")
+                printf("");
+
             std::string per_name_stat_name = "slowpath_box_getattr." + std::string(attr);
             int id = Stats::getStatId(per_name_stat_name);
             Stats::log(id);
         }
+    }
 #endif
     box_getattr_slowpath.log();