More work on decoupling the general runtime from Interpreter. The goal
is becoming clearer. Interpreter should be one possible way to execute
code inside a VM. In the future we might have other ways :^)
This patch moves the exception state, call stack and scope stack from
Interpreter to VM. I'm doing this to help myself discover what the
split between Interpreter and VM should be, by shuffling things around
and seeing what falls where.
With these changes, we no longer have a persistent lexical environment
for the current global object on the Interpreter's call stack. Instead,
we push/pop that environment on Interpreter::run() enter/exit.
Since it should only be used to find the global "this", and not for
variable storage (that goes directly into the global object instead!),
I had to insert some short-circuiting when walking the environment
parent chain during variable lookup.
Note that this is a "stepping stone" commit, not a final design.
Decorated Interpreter::call() with [[nodiscard]] to provoke thinking
about the returned value at each call site. This is definitely not
perfect and we should really start thinking about slimming down the
public-facing LibJS interpreter API.
Fixes#3136.
More steps towards multiple global object support. Primitive cells
like strings, bigints, etc, don't actually have any connection to
the global object. Use the explicit API to clarify this.
literal methods; add EnvrionmentRecord fields and methods to
LexicalEnvironment
Adding EnvrionmentRecord's fields and methods lets us throw an exception
when |this| is not initialized, which occurs when the super constructor
in a derived class has not yet been called, or when |this| has already
been initialized (the super constructor was already called).
This is a helper function based on the getter/setter definition logic from
ObjectExpression::execute() to look up an Accessor property if it already
exists, define a new Accessor property if it doesn't exist, and set the getter or
setter function on the Accessor.
Divide the Object constructor into three variants:
- The regular one (takes an Object& prototype)
- One for use by GlobalObject
- One for use by objects without a prototype (e.g ObjectPrototype)
To make sure that everything is set up correctly in objects before we
start adding properties to them, we split cell allocation into 3 steps:
1. Allocate a cell of appropriate size from the Heap
2. Call the C++ constructor on the cell
3. Call initialize() on the constructed object
The job of initialize() is to define all the initial properties.
Doing it in a second pass guarantees that the Object has a valid Shape
and can find its own GlobalObject.
More work towards supporting multiple global objects. Native C++ code
now get a GlobalObject& and don't have to ask the Interpreter for it.
I've added macros for declaring and defining native callbacks since
this was pretty tedious and this makes it easier next time we want to
change any of these signatures.
Get rid of the weird old signature:
- int StringType::to_int(bool& ok) const
And replace it with sensible new signature:
- Optional<int> StringType::to_int() const
Objects should get the GlobalObject from themselves instead. However,
it's not yet available during construction so this only switches code
that happens after construction.
To support multiple global objects, Interpreter needs to stop holding
on to "the" global object and let each object graph own their global.
We need to move towards supporting multiple global objects, which will
be a large refactoring. To keep it manageable, let's do it in steps,
starting with giving Object a way to find the GlobalObject it lives
inside by asking its Shape for it.
Includes all traps except the following: [[Call]], [[Construct]],
[[OwnPropertyKeys]].
An important implication of this commit is that any call to any virtual
Object method has the potential to throw an exception. These methods
were not checked in this commit -- a future commit will have to protect
these various method calls throughout the codebase.
This new struct is now returned from get_own_property_descriptor. To
preserve the old functionality of returning an object, there is now a
get_own_property_descriptor_object method, for use in
{Object,Reflect}.getOwnPropertyDescriptor().
This change will be useful for the implementation of Proxies, which do a
lot of descriptor checks. We want to avoid as many object gets and puts
as possible.
When calling Object.defineProperty, there is now a difference between
omitting a descriptor attribute and specifying that it is false. For
example, "{}" and "{ configurable: false }" will have different
attribute values.
Object::set_prototype() now returns a boolean indicating success.
Setting the prototype to an identical object is always considered
successful, even if the object is non-extensible.
Previously, the relational operators where casting any value to double
and comparing the results according to C++ semantics.
This patch makes the relational operators in JS behave according to the
standard specification.
Since we don't have BigInt yet, the implementation doesn't take it into
account.
Moved PreferredType from Object to Value. Value::to_primitive now
passes preferred_type to Object::to_primitive.
This patch adds an IndexedProperties object for storing indexed
properties within an Object. This accomplishes two goals: indexed
properties now have an associated descriptor, and objects now gracefully
handle sparse properties.
The IndexedProperties class is a wrapper around two other classes, one
for simple indexed properties storage, and one for general indexed
property storage. Simple indexed property storage is the common-case,
and is simply a vector of properties which all have attributes of
default_attributes (writable, enumerable, and configurable).
General indexed property storage is for a collection of indexed
properties where EITHER one or more properties have attributes other
than default_attributes OR there is a property with a large index (in
particular, large is '200' or higher).
Indexed properties are now treated relatively the same as storage within
the various Object methods. Additionally, there is a custom iterator
class for IndexedProperties which makes iteration easy. The iterator
skips empty values by default, but can be configured otherwise.
Likewise, it evaluates getters by default, but can be set not to.
Previously, the Object class had many different types of functions for
each action. For example: get_by_index, get(PropertyName),
get(FlyString). This is a bit verbose, so these methods have been
shortened to simply use the PropertyName structure. The methods then
internally call _by_index if necessary. Note that the _by_index
have been made private to enforce this change.
Secondly, a clear distinction has been made between "putting" and
"defining" an object property. "Putting" should mean modifying a
(potentially) already existing property. This is akin to doing "a.b =
'foo'".
This implies two things about put operations:
- They will search the prototype chain for setters and call them, if
necessary.
- If no property exists with a particular key, the put operation
should create a new property with the default attributes
(configurable, writable, and enumerable).
In contrast, "defining" a property should completely overwrite any
existing value without calling setters (if that property is
configurable, of course).
Thus, all of the many JS objects have had any "put" calls changed to
"define_property" calls. Additionally, "put_native_function" and
"put_native_property" have had their "put" replaced with "define".
Finally, "put_own_property" has been made private, as all necessary
functionality should be exposed with the put and define_property
methods.
This changes Accessor's m_{getter,setter} from Value to Function* which
seems like a better API to me - a getter/setter must either be a
function or missing, and the creation of an accessor with other values
must be prevented by the parser and Object.defineProperty() anyway.
Also add Accessor::set_{getter,setter}() so we can reuse an already
created accessor when evaluating an ObjectExpression with getter/setter
shorthand syntax.
This patch adds a GetterSetterPair object. Values can now store pointers
to objects of this type. These objects are created when using
Object.defineProperty and providing an accessor descriptor.
