The properties of the builtins are only enumerable after their first usage

[renatahodovan]

Jerry version:

Checked revision: 9d423d9
Build: debug.linux

OS:

Ubuntu 14.04, x86_64

Description:

Asking for the properties of any builtin objects results in a list, that only contains the previously used property names.
E.g:

var propertyNames = Object.getOwnPropertyNames(Math);
print(propertyNames.join(", "));

results an empty list. However:

var propertyNames = Object.getOwnPropertyNames(Object);
print(propertyNames.join(", "));

gives a list with only the "getOwnPropertyNames" property, since it was used already.

[galpeter]

@ruben-ayrapetyan, @egavrin I've created a proof-of-concept patch to see how could we initialize the properties, please see commit on the https://github.com/galpeter/jerryscript/commits/builtin_init branch. What do you think about it?

One thing I currently see that if we initialize all properties for a given built-in then we can remove the _try_to_instantiate_property method. which is currently not removed in the branch.

[ruben-ayrapetyan]

@galpeter, could you, please, clarify would properties of built-ins that are not accessed during execution of a script, be initialized if the changes are applied?

[galpeter]

@ruben-ayrapetyan, this would initialize all builtins as once you access the global object (with ecma_builtin_get) all builtins which are there are initialized, and also the properties of those builtins.

The code works that it would only initialize the given (ecma_instantiate_builtin function argument) builtin's properties and the builtin prototype's properties (and it's prototype's properties, etc..). For example if I do a print(Math) it would initialize it's funcion/value properties but also the Function Prototype builtin as it is required to create properties which have a function value (this is done by the function call ecma_builtin_make_function_object_for_routine)

[ruben-ayrapetyan]

@galpeter, currently used version initializes a built-in's property only upon access to the property.

Could we implement enumeration without removing the lazy instantiation? Maybe, we could add special ecma_op_object_get_own_property_names for enumerating the names, without instantiating a built-in's properties until they are not not actually accessed.

What do you think about this?

[galpeter]

@ruben-ayrapetyan currently the in the property list, which is returned by the ecma_get_property_list call, not all properties are there for built-ins. If we introduce a special function I'm afraid it could give us headache later on. If we introduce a special call we would need to have a list of all builtin property names somewhere, but then if we instantiate all properties for a builtin there is no need for such list as the property linked list will have all the names, thus we end up with the same information twice in the memory.

In short the approach could help, but it could also be that it just gives more code/memory usage in the end.

[ruben-ayrapetyan]

@galpeter, names of properties for each built-in are already stored in memory (ecma_builtin_property_names static arrays).
Also, maybe, there is very limited number of points, were we really need the whole list of properties' names (not necessary instantiation of the properties).

Contrariwise, disabling lazy instantiation of built-in's properties increases memory usage.

[egavrin]

var propertyNames = Object.getOwnPropertyNames(Math);
print(propertyNames.join(", "));

tan, sqrt, sin, round, random, pow, min, max, log, floor, exp, cos, ceil, atan2, atan, asin, acos, abs, SQRT2, SQRT1_2, PI, LOG10E, LOG2E, LN2, LN10, E

Works on master, closing.