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/*
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* Copyright ( c ) 2020 - 2021 , Andreas Kling < kling @ serenityos . org >
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* Copyright ( c ) 2020 - 2021 , Linus Groh < linusg @ serenityos . org >
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* Copyright ( c ) 2021 , David Tuin < davidot @ serenityos . org >
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*
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* SPDX - License - Identifier : BSD - 2 - Clause
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*/
LibJS: Add initial support for Promises
Almost a year after first working on this, it's finally done: an
implementation of Promises for LibJS! :^)
The core functionality is working and closely following the spec [1].
I mostly took the pseudo code and transformed it into C++ - if you read
and understand it, you will know how the spec implements Promises; and
if you read the spec first, the code will look very familiar.
Implemented functions are:
- Promise() constructor
- Promise.prototype.then()
- Promise.prototype.catch()
- Promise.prototype.finally()
- Promise.resolve()
- Promise.reject()
For the tests I added a new function to test-js's global object,
runQueuedPromiseJobs(), which calls vm.run_queued_promise_jobs().
By design, queued jobs normally only run after the script was fully
executed, making it improssible to test handlers in individual test()
calls by default [2].
Subsequent commits include integrations into LibWeb and js(1) -
pretty-printing, running queued promise jobs when necessary.
This has an unusual amount of dbgln() statements, all hidden behind the
PROMISE_DEBUG flag - I'm leaving them in for now as they've been very
useful while debugging this, things can get quite complex with so many
asynchronously executed functions.
I've not extensively explored use of these APIs for promise-based
functionality in LibWeb (fetch(), Notification.requestPermission()
etc.), but we'll get there in due time.
[1]: https://tc39.es/ecma262/#sec-promise-objects
[2]: https://tc39.es/ecma262/#sec-jobs-and-job-queues
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# include <AK/Debug.h>
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# include <AK/ScopeGuard.h>
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# include <AK/StringBuilder.h>
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# include <LibJS/Interpreter.h>
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# include <LibJS/Runtime/AbstractOperations.h>
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# include <LibJS/Runtime/Array.h>
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# include <LibJS/Runtime/BoundFunction.h>
LibJS: Implement [[Call]] and [[Construct]] internal slots properly
This patch implements:
- Spec compliant [[Call]] and [[Construct]] internal slots, as virtual
FunctionObject::internal_{call,construct}(). These effectively replace
the old virtual FunctionObject::{call,construct}(), but with several
advantages:
- Clear and consistent naming, following the object internal methods
- Use of completions
- internal_construct() returns an Object, and not Value! This has been
a source of confusion for a long time, since in the spec there's
always an Object returned but the Value return type in LibJS meant
that this could not be fully trusted and something could screw you
over.
- Arguments are passed explicitly in form of a MarkedValueList,
allowing manipulation (BoundFunction). We still put them on the
execution context as a lot of code depends on it (VM::arguments()),
but not from the Call() / Construct() AOs anymore, which now allows
for bypassing them and invoking [[Call]] / [[Construct]] directly.
Nothing but Call() / Construct() themselves do that at the moment,
but future additions to ECMA262 or already existing web specs might.
- Spec compliant, standalone Call() and Construct() AOs: currently the
closest we have is VM::{call,construct}(), but those try to cater to
all the different function object subclasses at once, resulting in a
horrible mess and calling AOs with functions they should never be
called with; most prominently PrepareForOrdinaryCall and
OrdinaryCallBindThis, which are only for ECMAScriptFunctionObject.
As a result this also contains an implicit optimization: we no longer
need to create a new function environment for NativeFunctions - which,
worth mentioning, is what started this whole crusade in the first place
:^)
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# include <LibJS/Runtime/Completion.h>
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# include <LibJS/Runtime/ECMAScriptFunctionObject.h>
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# include <LibJS/Runtime/Error.h>
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# include <LibJS/Runtime/FinalizationRegistry.h>
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# include <LibJS/Runtime/FunctionEnvironment.h>
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# include <LibJS/Runtime/GlobalObject.h>
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# include <LibJS/Runtime/IteratorOperations.h>
LibJS: Add initial support for Promises
Almost a year after first working on this, it's finally done: an
implementation of Promises for LibJS! :^)
The core functionality is working and closely following the spec [1].
I mostly took the pseudo code and transformed it into C++ - if you read
and understand it, you will know how the spec implements Promises; and
if you read the spec first, the code will look very familiar.
Implemented functions are:
- Promise() constructor
- Promise.prototype.then()
- Promise.prototype.catch()
- Promise.prototype.finally()
- Promise.resolve()
- Promise.reject()
For the tests I added a new function to test-js's global object,
runQueuedPromiseJobs(), which calls vm.run_queued_promise_jobs().
By design, queued jobs normally only run after the script was fully
executed, making it improssible to test handlers in individual test()
calls by default [2].
Subsequent commits include integrations into LibWeb and js(1) -
pretty-printing, running queued promise jobs when necessary.
This has an unusual amount of dbgln() statements, all hidden behind the
PROMISE_DEBUG flag - I'm leaving them in for now as they've been very
useful while debugging this, things can get quite complex with so many
asynchronously executed functions.
I've not extensively explored use of these APIs for promise-based
functionality in LibWeb (fetch(), Notification.requestPermission()
etc.), but we'll get there in due time.
[1]: https://tc39.es/ecma262/#sec-promise-objects
[2]: https://tc39.es/ecma262/#sec-jobs-and-job-queues
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# include <LibJS/Runtime/NativeFunction.h>
# include <LibJS/Runtime/PromiseReaction.h>
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# include <LibJS/Runtime/Reference.h>
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# include <LibJS/Runtime/Symbol.h>
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# include <LibJS/Runtime/TemporaryClearException.h>
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# include <LibJS/Runtime/VM.h>
namespace JS {
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NonnullRefPtr < VM > VM : : create ( OwnPtr < CustomData > custom_data )
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{
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return adopt_ref ( * new VM ( move ( custom_data ) ) ) ;
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}
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VM : : VM ( OwnPtr < CustomData > custom_data )
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: m_heap ( * this )
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, m_custom_data ( move ( custom_data ) )
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{
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m_empty_string = m_heap . allocate_without_global_object < PrimitiveString > ( String : : empty ( ) ) ;
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for ( size_t i = 0 ; i < 128 ; + + i ) {
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m_single_ascii_character_strings [ i ] = m_heap . allocate_without_global_object < PrimitiveString > ( String : : formatted ( " {:c} " , i ) ) ;
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}
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# define __JS_ENUMERATE(SymbolName, snake_name) \
m_well_known_symbol_ # # snake_name = js_symbol ( * this , " Symbol. " # SymbolName , false ) ;
JS_ENUMERATE_WELL_KNOWN_SYMBOLS
# undef __JS_ENUMERATE
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}
VM : : ~ VM ( )
{
}
Interpreter & VM : : interpreter ( )
{
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VERIFY ( ! m_interpreters . is_empty ( ) ) ;
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return * m_interpreters . last ( ) ;
}
Interpreter * VM : : interpreter_if_exists ( )
{
if ( m_interpreters . is_empty ( ) )
return nullptr ;
return m_interpreters . last ( ) ;
}
void VM : : push_interpreter ( Interpreter & interpreter )
{
m_interpreters . append ( & interpreter ) ;
}
void VM : : pop_interpreter ( Interpreter & interpreter )
{
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VERIFY ( ! m_interpreters . is_empty ( ) ) ;
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auto * popped_interpreter = m_interpreters . take_last ( ) ;
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VERIFY ( popped_interpreter = = & interpreter ) ;
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}
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VM : : InterpreterExecutionScope : : InterpreterExecutionScope ( Interpreter & interpreter )
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: m_interpreter ( interpreter )
{
m_interpreter . vm ( ) . push_interpreter ( m_interpreter ) ;
}
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VM : : InterpreterExecutionScope : : ~ InterpreterExecutionScope ( )
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{
m_interpreter . vm ( ) . pop_interpreter ( m_interpreter ) ;
}
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void VM : : gather_roots ( HashTable < Cell * > & roots )
{
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roots . set ( m_empty_string ) ;
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for ( auto * string : m_single_ascii_character_strings )
roots . set ( string ) ;
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roots . set ( m_exception ) ;
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if ( m_last_value . is_cell ( ) )
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roots . set ( & m_last_value . as_cell ( ) ) ;
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auto gather_roots_from_execution_context_stack = [ & roots ] ( Vector < ExecutionContext * > const & stack ) {
for ( auto & execution_context : stack ) {
if ( execution_context - > this_value . is_cell ( ) )
roots . set ( & execution_context - > this_value . as_cell ( ) ) ;
for ( auto & argument : execution_context - > arguments ) {
if ( argument . is_cell ( ) )
roots . set ( & argument . as_cell ( ) ) ;
}
roots . set ( execution_context - > lexical_environment ) ;
roots . set ( execution_context - > variable_environment ) ;
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roots . set ( execution_context - > private_environment ) ;
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}
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} ;
gather_roots_from_execution_context_stack ( m_execution_context_stack ) ;
for ( auto & saved_stack : m_saved_execution_context_stacks )
gather_roots_from_execution_context_stack ( saved_stack ) ;
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# define __JS_ENUMERATE(SymbolName, snake_name) \
roots . set ( well_known_symbol_ # # snake_name ( ) ) ;
JS_ENUMERATE_WELL_KNOWN_SYMBOLS
# undef __JS_ENUMERATE
for ( auto & symbol : m_global_symbol_map )
roots . set ( symbol . value ) ;
LibJS: Add initial support for Promises
Almost a year after first working on this, it's finally done: an
implementation of Promises for LibJS! :^)
The core functionality is working and closely following the spec [1].
I mostly took the pseudo code and transformed it into C++ - if you read
and understand it, you will know how the spec implements Promises; and
if you read the spec first, the code will look very familiar.
Implemented functions are:
- Promise() constructor
- Promise.prototype.then()
- Promise.prototype.catch()
- Promise.prototype.finally()
- Promise.resolve()
- Promise.reject()
For the tests I added a new function to test-js's global object,
runQueuedPromiseJobs(), which calls vm.run_queued_promise_jobs().
By design, queued jobs normally only run after the script was fully
executed, making it improssible to test handlers in individual test()
calls by default [2].
Subsequent commits include integrations into LibWeb and js(1) -
pretty-printing, running queued promise jobs when necessary.
This has an unusual amount of dbgln() statements, all hidden behind the
PROMISE_DEBUG flag - I'm leaving them in for now as they've been very
useful while debugging this, things can get quite complex with so many
asynchronously executed functions.
I've not extensively explored use of these APIs for promise-based
functionality in LibWeb (fetch(), Notification.requestPermission()
etc.), but we'll get there in due time.
[1]: https://tc39.es/ecma262/#sec-promise-objects
[2]: https://tc39.es/ecma262/#sec-jobs-and-job-queues
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for ( auto * job : m_promise_jobs )
roots . set ( job ) ;
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for ( auto * finalization_registry : m_finalization_registry_cleanup_jobs )
roots . set ( finalization_registry ) ;
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}
Symbol * VM : : get_global_symbol ( const String & description )
{
auto result = m_global_symbol_map . get ( description ) ;
if ( result . has_value ( ) )
return result . value ( ) ;
auto new_global_symbol = js_symbol ( * this , description , true ) ;
m_global_symbol_map . set ( description , new_global_symbol ) ;
return new_global_symbol ;
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}
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ThrowCompletionOr < Value > VM : : named_evaluation_if_anonymous_function ( GlobalObject & global_object , ASTNode const & expression , FlyString const & name )
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{
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// 8.3.3 Static Semantics: IsAnonymousFunctionDefinition ( expr ), https://tc39.es/ecma262/#sec-isanonymousfunctiondefinition
// And 8.3.5 Runtime Semantics: NamedEvaluation, https://tc39.es/ecma262/#sec-runtime-semantics-namedevaluation
if ( is < FunctionExpression > ( expression ) ) {
auto & function = static_cast < FunctionExpression const & > ( expression ) ;
if ( ! function . has_name ( ) ) {
return function . instantiate_ordinary_function_expression ( interpreter ( ) , global_object , name ) ;
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}
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} else if ( is < ClassExpression > ( expression ) ) {
auto & class_expression = static_cast < ClassExpression const & > ( expression ) ;
if ( ! class_expression . has_name ( ) ) {
return TRY ( class_expression . class_definition_evaluation ( interpreter ( ) , global_object , { } , name ) ) ;
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}
}
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auto value = expression . execute ( interpreter ( ) , global_object ) ;
if ( auto * thrown_exception = exception ( ) )
return JS : : throw_completion ( thrown_exception - > value ( ) ) ;
return value ;
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}
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// 13.15.5.2 Runtime Semantics: DestructuringAssignmentEvaluation, https://tc39.es/ecma262/#sec-runtime-semantics-destructuringassignmentevaluation
ThrowCompletionOr < void > VM : : destructuring_assignment_evaluation ( NonnullRefPtr < BindingPattern > const & target , Value value , GlobalObject & global_object )
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{
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// Note: DestructuringAssignmentEvaluation is just like BindingInitialization without an environment
// And it allows member expressions. We thus trust the parser to disallow member expressions
// in any non assignment binding and just call BindingInitialization with a nullptr environment
return binding_initialization ( target , value , nullptr , global_object ) ;
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}
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// 8.5.2 Runtime Semantics: BindingInitialization, https://tc39.es/ecma262/#sec-runtime-semantics-bindinginitialization
ThrowCompletionOr < void > VM : : binding_initialization ( FlyString const & target , Value value , Environment * environment , GlobalObject & global_object )
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{
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if ( environment ) {
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MUST ( environment - > initialize_binding ( global_object , target , value ) ) ;
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return { } ;
}
auto reference = resolve_binding ( target ) ;
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return reference . put_value ( global_object , value ) ;
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}
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// 8.5.2 Runtime Semantics: BindingInitialization, https://tc39.es/ecma262/#sec-runtime-semantics-bindinginitialization
ThrowCompletionOr < void > VM : : binding_initialization ( NonnullRefPtr < BindingPattern > const & target , Value value , Environment * environment , GlobalObject & global_object )
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{
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if ( target - > kind = = BindingPattern : : Kind : : Object ) {
TRY ( require_object_coercible ( global_object , value ) ) ;
TRY ( property_binding_initialization ( * target , value , environment , global_object ) ) ;
return { } ;
} else {
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auto * iterator = TRY ( get_iterator ( global_object , value ) ) ;
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auto iterator_done = false ;
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auto result = iterator_binding_initialization ( * target , iterator , iterator_done , environment , global_object ) ;
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if ( ! iterator_done ) {
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// iterator_close() always returns a Completion, which ThrowCompletionOr will interpret as a throw
// completion. So only return the result of iterator_close() if it is indeed a throw completion.
auto completion = result . is_throw_completion ( ) ? result . release_error ( ) : normal_completion ( { } ) ;
if ( completion = iterator_close ( * iterator , move ( completion ) ) ; completion . is_error ( ) )
return completion . release_error ( ) ;
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}
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return result ;
}
}
// 13.15.5.3 Runtime Semantics: PropertyDestructuringAssignmentEvaluation, https://tc39.es/ecma262/#sec-runtime-semantics-propertydestructuringassignmentevaluation
// 14.3.3.1 Runtime Semantics: PropertyBindingInitialization, https://tc39.es/ecma262/#sec-destructuring-binding-patterns-runtime-semantics-propertybindinginitialization
ThrowCompletionOr < void > VM : : property_binding_initialization ( BindingPattern const & binding , Value value , Environment * environment , GlobalObject & global_object )
{
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auto * object = TRY ( value . to_object ( global_object ) ) ;
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HashTable < PropertyKey > seen_names ;
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for ( auto & property : binding . entries ) {
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VERIFY ( ! property . is_elision ( ) ) ;
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if ( property . is_rest ) {
Reference assignment_target ;
if ( auto identifier_ptr = property . name . get_pointer < NonnullRefPtr < Identifier > > ( ) ) {
assignment_target = resolve_binding ( ( * identifier_ptr ) - > string ( ) , environment ) ;
} else if ( auto member_ptr = property . alias . get_pointer < NonnullRefPtr < MemberExpression > > ( ) ) {
assignment_target = ( * member_ptr ) - > to_reference ( interpreter ( ) , global_object ) ;
} else {
VERIFY_NOT_REACHED ( ) ;
}
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if ( auto * thrown_exception = exception ( ) )
return JS : : throw_completion ( thrown_exception - > value ( ) ) ;
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auto * rest_object = Object : : create ( global_object , global_object . object_prototype ( ) ) ;
VERIFY ( rest_object ) ;
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TRY ( rest_object - > copy_data_properties ( object , seen_names , global_object ) ) ;
if ( ! environment )
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return assignment_target . put_value ( global_object , rest_object ) ;
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else
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return assignment_target . initialize_referenced_binding ( global_object , rest_object ) ;
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}
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PropertyKey name ;
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property . name . visit (
[ & ] ( Empty ) { VERIFY_NOT_REACHED ( ) ; } ,
[ & ] ( NonnullRefPtr < Identifier > const & identifier ) {
name = identifier - > string ( ) ;
} ,
[ & ] ( NonnullRefPtr < Expression > const & expression ) {
auto result = expression - > execute ( interpreter ( ) , global_object ) ;
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if ( exception ( ) )
return ;
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auto name_or_error = result . to_property_key ( global_object ) ;
if ( name_or_error . is_error ( ) )
return ;
name = name_or_error . release_value ( ) ;
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} ) ;
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if ( auto * thrown_exception = exception ( ) )
return JS : : throw_completion ( thrown_exception - > value ( ) ) ;
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seen_names . set ( name ) ;
if ( property . name . has < NonnullRefPtr < Identifier > > ( ) & & property . alias . has < Empty > ( ) ) {
// FIXME: this branch and not taking this have a lot in common we might want to unify it more (like it was before).
auto & identifier = * property . name . get < NonnullRefPtr < Identifier > > ( ) ;
auto reference = resolve_binding ( identifier . string ( ) , environment ) ;
if ( auto * thrown_exception = exception ( ) )
return JS : : throw_completion ( thrown_exception - > value ( ) ) ;
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auto value_to_assign = TRY ( object - > get ( name ) ) ;
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if ( property . initializer & & value_to_assign . is_undefined ( ) ) {
value_to_assign = TRY ( named_evaluation_if_anonymous_function ( global_object , * property . initializer , identifier . string ( ) ) ) ;
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}
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if ( ! environment )
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TRY ( reference . put_value ( global_object , value_to_assign ) ) ;
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else
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TRY ( reference . initialize_referenced_binding ( global_object , value_to_assign ) ) ;
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continue ;
}
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Optional < Reference > reference_to_assign_to ;
property . alias . visit (
[ & ] ( Empty ) { } ,
[ & ] ( NonnullRefPtr < Identifier > const & identifier ) {
reference_to_assign_to = resolve_binding ( identifier - > string ( ) , environment ) ;
} ,
[ & ] ( NonnullRefPtr < BindingPattern > const & ) { } ,
[ & ] ( NonnullRefPtr < MemberExpression > const & member_expression ) {
reference_to_assign_to = member_expression - > to_reference ( interpreter ( ) , global_object ) ;
} ) ;
if ( auto * thrown_exception = exception ( ) )
return JS : : throw_completion ( thrown_exception - > value ( ) ) ;
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auto value_to_assign = TRY ( object - > get ( name ) ) ;
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if ( property . initializer & & value_to_assign . is_undefined ( ) ) {
if ( auto * identifier_ptr = property . alias . get_pointer < NonnullRefPtr < Identifier > > ( ) )
value_to_assign = TRY ( named_evaluation_if_anonymous_function ( global_object , * property . initializer , ( * identifier_ptr ) - > string ( ) ) ) ;
else
value_to_assign = property . initializer - > execute ( interpreter ( ) , global_object ) ;
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if ( auto * thrown_exception = exception ( ) )
return JS : : throw_completion ( thrown_exception - > value ( ) ) ;
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}
2021-06-12 18:04:28 -07:00
2021-09-22 12:44:56 +02:00
if ( auto * binding_ptr = property . alias . get_pointer < NonnullRefPtr < BindingPattern > > ( ) ) {
TRY ( binding_initialization ( * binding_ptr , value_to_assign , environment , global_object ) ) ;
} else {
VERIFY ( reference_to_assign_to . has_value ( ) ) ;
if ( ! environment )
2021-11-02 19:20:21 +02:00
TRY ( reference_to_assign_to - > put_value ( global_object , value_to_assign ) ) ;
2021-09-22 12:44:56 +02:00
else
2021-11-02 19:27:29 +02:00
TRY ( reference_to_assign_to - > initialize_referenced_binding ( global_object , value_to_assign ) ) ;
2021-09-22 12:44:56 +02:00
}
2020-09-27 15:18:55 +02:00
}
2021-06-12 18:04:28 -07:00
2021-09-22 12:44:56 +02:00
return { } ;
}
2020-09-27 15:18:55 +02:00
2021-09-22 12:44:56 +02:00
// 13.15.5.5 Runtime Semantics: IteratorDestructuringAssignmentEvaluation, https://tc39.es/ecma262/#sec-runtime-semantics-iteratordestructuringassignmentevaluation
// 8.5.3 Runtime Semantics: IteratorBindingInitialization, https://tc39.es/ecma262/#sec-runtime-semantics-iteratorbindinginitialization
ThrowCompletionOr < void > VM : : iterator_binding_initialization ( BindingPattern const & binding , Object * iterator , bool & iterator_done , Environment * environment , GlobalObject & global_object )
{
// FIXME: this method is nearly identical to destructuring assignment!
for ( size_t i = 0 ; i < binding . entries . size ( ) ; i + + ) {
auto & entry = binding . entries [ i ] ;
Value value ;
2021-06-12 18:04:28 -07:00
2021-09-22 12:44:56 +02:00
Optional < Reference > assignment_target ;
entry . alias . visit (
[ & ] ( Empty ) { } ,
[ & ] ( NonnullRefPtr < Identifier > const & identifier ) {
assignment_target = resolve_binding ( identifier - > string ( ) , environment ) ;
} ,
[ & ] ( NonnullRefPtr < BindingPattern > const & ) { } ,
[ & ] ( NonnullRefPtr < MemberExpression > const & member_expression ) {
assignment_target = member_expression - > to_reference ( interpreter ( ) , global_object ) ;
} ) ;
2021-05-29 16:03:19 +04:30
2021-09-22 12:44:56 +02:00
if ( auto * thrown_exception = exception ( ) )
return JS : : throw_completion ( thrown_exception - > value ( ) ) ;
2021-05-29 16:03:19 +04:30
2021-09-22 12:44:56 +02:00
if ( entry . is_rest ) {
VERIFY ( i = = binding . entries . size ( ) - 1 ) ;
2021-05-29 16:03:19 +04:30
2021-10-22 01:34:06 +03:00
auto * array = MUST ( Array : : create ( global_object , 0 ) ) ;
2021-09-22 12:44:56 +02:00
while ( ! iterator_done ) {
2021-10-20 08:44:30 -04:00
auto next_object_or_error = iterator_next ( * iterator ) ;
if ( next_object_or_error . is_throw_completion ( ) ) {
2021-09-22 12:44:56 +02:00
iterator_done = true ;
2021-10-20 08:44:30 -04:00
return JS : : throw_completion ( next_object_or_error . release_error ( ) . value ( ) ) ;
2021-09-22 12:44:56 +02:00
}
2021-10-20 08:44:30 -04:00
auto * next_object = next_object_or_error . release_value ( ) ;
2021-05-29 16:03:19 +04:30
2021-10-02 23:52:27 +01:00
auto done_property = TRY ( next_object - > get ( names . done ) ) ;
2021-09-22 12:44:56 +02:00
if ( done_property . to_boolean ( ) ) {
iterator_done = true ;
break ;
}
2021-09-18 01:11:32 +02:00
2021-10-02 23:52:27 +01:00
auto next_value = TRY ( next_object - > get ( names . value ) ) ;
2021-09-22 12:44:56 +02:00
array - > indexed_properties ( ) . append ( next_value ) ;
}
value = array ;
} else if ( ! iterator_done ) {
2021-10-20 08:44:30 -04:00
auto next_object_or_error = iterator_next ( * iterator ) ;
if ( next_object_or_error . is_throw_completion ( ) ) {
2021-09-22 12:44:56 +02:00
iterator_done = true ;
2021-10-20 08:44:30 -04:00
return JS : : throw_completion ( next_object_or_error . release_error ( ) . value ( ) ) ;
2021-09-22 12:44:56 +02:00
}
2021-10-20 08:44:30 -04:00
auto * next_object = next_object_or_error . release_value ( ) ;
2021-09-22 12:44:56 +02:00
2021-10-02 23:52:27 +01:00
auto done_property = TRY ( next_object - > get ( names . done ) ) ;
2021-09-22 12:44:56 +02:00
if ( done_property . to_boolean ( ) ) {
iterator_done = true ;
value = js_undefined ( ) ;
} else {
2021-10-02 23:52:27 +01:00
auto value_or_error = next_object - > get ( names . value ) ;
if ( value_or_error . is_throw_completion ( ) ) {
2021-09-22 12:44:56 +02:00
iterator_done = true ;
2021-10-02 23:52:27 +01:00
return JS : : throw_completion ( value_or_error . release_error ( ) . value ( ) ) ;
2020-12-05 16:38:29 +01:00
}
2021-10-02 23:52:27 +01:00
value = value_or_error . release_value ( ) ;
2020-12-05 16:38:29 +01:00
}
2021-09-22 12:44:56 +02:00
} else {
value = js_undefined ( ) ;
2020-12-05 16:38:29 +01:00
}
2021-09-22 12:44:56 +02:00
if ( value . is_undefined ( ) & & entry . initializer ) {
VERIFY ( ! entry . is_rest ) ;
if ( auto * identifier_ptr = entry . alias . get_pointer < NonnullRefPtr < Identifier > > ( ) )
value = TRY ( named_evaluation_if_anonymous_function ( global_object , * entry . initializer , ( * identifier_ptr ) - > string ( ) ) ) ;
else
value = entry . initializer - > execute ( interpreter ( ) , global_object ) ;
if ( auto * thrown_exception = exception ( ) )
return JS : : throw_completion ( thrown_exception - > value ( ) ) ;
2020-09-27 15:18:55 +02:00
}
LibJS: Rewrite most of Object for spec compliance :^)
This is a huge patch, I know. In hindsight this perhaps could've been
done slightly more incremental, but I started and then fixed everything
until it worked, and here we are. I tried splitting of some completely
unrelated changes into separate commits, however. Anyway.
This is a rewrite of most of Object, and by extension large parts of
Array, Proxy, Reflect, String, TypedArray, and some other things.
What we already had worked fine for about 90% of things, but getting the
last 10% right proved to be increasingly difficult with the current code
that sort of grew organically and is only very loosely based on the
spec - this became especially obvious when we started fixing a large
number of test262 failures.
Key changes include:
- 1:1 matching function names and parameters of all object-related
functions, to avoid ambiguity. Previously we had things like put(),
which the spec doesn't have - as a result it wasn't always clear which
need to be used.
- Better separation between object abstract operations and internal
methods - the former are always the same, the latter can be overridden
(and are therefore virtual). The internal methods (i.e. [[Foo]] in the
spec) are now prefixed with 'internal_' for clarity - again, it was
previously not always clear which AO a certain method represents,
get() could've been both Get and [[Get]] (I don't know which one it
was closer to right now).
Note that some of the old names have been kept until all code relying
on them is updated, but they are now simple wrappers around the
closest matching standard abstract operation.
- Simplifications of the storage layer: functions that write values to
storage are now prefixed with 'storage_' to make their purpose clear,
and as they are not part of the spec they should not contain any steps
specified by it. Much functionality is now covered by the layers above
it and was removed (e.g. handling of accessors, attribute checks).
- PropertyAttributes has been greatly simplified, and is being replaced
by PropertyDescriptor - a concept similar to the current
implementation, but more aligned with the actual spec. See the commit
message of the previous commit where it was introduced for details.
- As a bonus, and since I had to look at the spec a whole lot anyway, I
introduced more inline comments with the exact steps from the spec -
this makes it super easy to verify correctness.
- East-const all the things.
As a result of all of this, things are much more correct but a bit
slower now. Retaining speed wasn't a consideration at all, I have done
no profiling of the new code - there might be low hanging fruits, which
we can then harvest separately.
Special thanks to Idan for helping me with this by tracking down bugs,
updating everything outside of LibJS to work with these changes (LibWeb,
Spreadsheet, HackStudio), as well as providing countless patches to fix
regressions I introduced - there still are very few (we got it down to
5), but we also get many new passing test262 tests in return. :^)
Co-authored-by: Idan Horowitz <idan.horowitz@gmail.com>
2021-07-04 18:14:16 +01:00
2021-09-22 12:44:56 +02:00
if ( auto * binding_ptr = entry . alias . get_pointer < NonnullRefPtr < BindingPattern > > ( ) ) {
TRY ( binding_initialization ( * binding_ptr , value , environment , global_object ) ) ;
} else if ( ! entry . alias . has < Empty > ( ) ) {
VERIFY ( assignment_target . has_value ( ) ) ;
if ( ! environment )
2021-11-02 19:20:21 +02:00
TRY ( assignment_target - > put_value ( global_object , value ) ) ;
2021-09-22 12:44:56 +02:00
else
2021-11-02 19:27:29 +02:00
TRY ( assignment_target - > initialize_referenced_binding ( global_object , value ) ) ;
2021-09-22 12:44:56 +02:00
}
LibJS: Rewrite most of Object for spec compliance :^)
This is a huge patch, I know. In hindsight this perhaps could've been
done slightly more incremental, but I started and then fixed everything
until it worked, and here we are. I tried splitting of some completely
unrelated changes into separate commits, however. Anyway.
This is a rewrite of most of Object, and by extension large parts of
Array, Proxy, Reflect, String, TypedArray, and some other things.
What we already had worked fine for about 90% of things, but getting the
last 10% right proved to be increasingly difficult with the current code
that sort of grew organically and is only very loosely based on the
spec - this became especially obvious when we started fixing a large
number of test262 failures.
Key changes include:
- 1:1 matching function names and parameters of all object-related
functions, to avoid ambiguity. Previously we had things like put(),
which the spec doesn't have - as a result it wasn't always clear which
need to be used.
- Better separation between object abstract operations and internal
methods - the former are always the same, the latter can be overridden
(and are therefore virtual). The internal methods (i.e. [[Foo]] in the
spec) are now prefixed with 'internal_' for clarity - again, it was
previously not always clear which AO a certain method represents,
get() could've been both Get and [[Get]] (I don't know which one it
was closer to right now).
Note that some of the old names have been kept until all code relying
on them is updated, but they are now simple wrappers around the
closest matching standard abstract operation.
- Simplifications of the storage layer: functions that write values to
storage are now prefixed with 'storage_' to make their purpose clear,
and as they are not part of the spec they should not contain any steps
specified by it. Much functionality is now covered by the layers above
it and was removed (e.g. handling of accessors, attribute checks).
- PropertyAttributes has been greatly simplified, and is being replaced
by PropertyDescriptor - a concept similar to the current
implementation, but more aligned with the actual spec. See the commit
message of the previous commit where it was introduced for details.
- As a bonus, and since I had to look at the spec a whole lot anyway, I
introduced more inline comments with the exact steps from the spec -
this makes it super easy to verify correctness.
- East-const all the things.
As a result of all of this, things are much more correct but a bit
slower now. Retaining speed wasn't a consideration at all, I have done
no profiling of the new code - there might be low hanging fruits, which
we can then harvest separately.
Special thanks to Idan for helping me with this by tracking down bugs,
updating everything outside of LibJS to work with these changes (LibWeb,
Spreadsheet, HackStudio), as well as providing countless patches to fix
regressions I introduced - there still are very few (we got it down to
5), but we also get many new passing test262 tests in return. :^)
Co-authored-by: Idan Horowitz <idan.horowitz@gmail.com>
2021-07-04 18:14:16 +01:00
}
2021-09-22 12:44:56 +02:00
return { } ;
2020-09-27 15:18:55 +02:00
}
2021-07-02 21:54:56 +02:00
// 9.1.2.1 GetIdentifierReference ( env, name, strict ), https://tc39.es/ecma262/#sec-getidentifierreference
2021-10-07 01:06:21 +02:00
Reference VM : : get_identifier_reference ( Environment * environment , FlyString name , bool strict , size_t hops )
2020-09-27 15:18:55 +02:00
{
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// 1. If env is the value null, then
if ( ! environment ) {
// a. Return the Reference Record { [[Base]]: unresolvable, [[ReferencedName]]: name, [[Strict]]: strict, [[ThisValue]]: empty }.
2021-09-11 19:03:38 +02:00
return Reference { Reference : : BaseType : : Unresolvable , move ( name ) , strict } ;
2021-07-02 21:54:56 +02:00
}
2021-10-07 00:16:37 +02:00
Optional < size_t > index ;
2021-10-09 17:07:32 +01:00
auto exists = TRY_OR_DISCARD ( environment - > has_binding ( name , & index ) ) ;
2021-07-02 21:54:56 +02:00
2021-10-07 01:06:21 +02:00
Optional < EnvironmentCoordinate > environment_coordinate ;
if ( index . has_value ( ) )
environment_coordinate = EnvironmentCoordinate { . hops = hops , . index = index . value ( ) } ;
2021-09-22 12:44:56 +02:00
if ( exists )
2021-10-07 01:06:21 +02:00
return Reference { * environment , move ( name ) , strict , environment_coordinate } ;
2021-09-22 12:44:56 +02:00
else
2021-10-07 01:06:21 +02:00
return get_identifier_reference ( environment - > outer_environment ( ) , move ( name ) , strict , hops + 1 ) ;
2021-07-02 21:54:56 +02:00
}
// 9.4.2 ResolveBinding ( name [ , env ] ), https://tc39.es/ecma262/#sec-resolvebinding
Reference VM : : resolve_binding ( FlyString const & name , Environment * environment )
{
// 1. If env is not present or if env is undefined, then
if ( ! environment ) {
// a. Set env to the running execution context's LexicalEnvironment.
environment = running_execution_context ( ) . lexical_environment ;
}
// 2. Assert: env is an Environment Record.
VERIFY ( environment ) ;
// 3. If the code matching the syntactic production that is being evaluated is contained in strict mode code, let strict be true; else let strict be false.
bool strict = in_strict_mode ( ) ;
// 4. Return ? GetIdentifierReference(env, name, strict).
return get_identifier_reference ( environment , name , strict ) ;
2020-09-27 15:18:55 +02:00
}
2021-12-21 08:27:04 -05:00
// 7.3.33 InitializeInstanceElements ( O, constructor ), https://tc39.es/ecma262/#sec-initializeinstanceelements
LibJS: Implement [[Call]] and [[Construct]] internal slots properly
This patch implements:
- Spec compliant [[Call]] and [[Construct]] internal slots, as virtual
FunctionObject::internal_{call,construct}(). These effectively replace
the old virtual FunctionObject::{call,construct}(), but with several
advantages:
- Clear and consistent naming, following the object internal methods
- Use of completions
- internal_construct() returns an Object, and not Value! This has been
a source of confusion for a long time, since in the spec there's
always an Object returned but the Value return type in LibJS meant
that this could not be fully trusted and something could screw you
over.
- Arguments are passed explicitly in form of a MarkedValueList,
allowing manipulation (BoundFunction). We still put them on the
execution context as a lot of code depends on it (VM::arguments()),
but not from the Call() / Construct() AOs anymore, which now allows
for bypassing them and invoking [[Call]] / [[Construct]] directly.
Nothing but Call() / Construct() themselves do that at the moment,
but future additions to ECMA262 or already existing web specs might.
- Spec compliant, standalone Call() and Construct() AOs: currently the
closest we have is VM::{call,construct}(), but those try to cater to
all the different function object subclasses at once, resulting in a
horrible mess and calling AOs with functions they should never be
called with; most prominently PrepareForOrdinaryCall and
OrdinaryCallBindThis, which are only for ECMAScriptFunctionObject.
As a result this also contains an implicit optimization: we no longer
need to create a new function environment for NativeFunctions - which,
worth mentioning, is what started this whole crusade in the first place
:^)
2021-10-08 20:37:21 +01:00
ThrowCompletionOr < void > VM : : initialize_instance_elements ( Object & object , ECMAScriptFunctionObject & constructor )
2021-08-28 17:11:05 +02:00
{
2021-10-12 22:45:52 +02:00
for ( auto & method : constructor . private_methods ( ) )
TRY ( object . private_method_or_accessor_add ( method ) ) ;
for ( auto & field : constructor . fields ( ) )
TRY ( object . define_field ( field . name , field . initializer ) ) ;
LibJS: Implement [[Call]] and [[Construct]] internal slots properly
This patch implements:
- Spec compliant [[Call]] and [[Construct]] internal slots, as virtual
FunctionObject::internal_{call,construct}(). These effectively replace
the old virtual FunctionObject::{call,construct}(), but with several
advantages:
- Clear and consistent naming, following the object internal methods
- Use of completions
- internal_construct() returns an Object, and not Value! This has been
a source of confusion for a long time, since in the spec there's
always an Object returned but the Value return type in LibJS meant
that this could not be fully trusted and something could screw you
over.
- Arguments are passed explicitly in form of a MarkedValueList,
allowing manipulation (BoundFunction). We still put them on the
execution context as a lot of code depends on it (VM::arguments()),
but not from the Call() / Construct() AOs anymore, which now allows
for bypassing them and invoking [[Call]] / [[Construct]] directly.
Nothing but Call() / Construct() themselves do that at the moment,
but future additions to ECMA262 or already existing web specs might.
- Spec compliant, standalone Call() and Construct() AOs: currently the
closest we have is VM::{call,construct}(), but those try to cater to
all the different function object subclasses at once, resulting in a
horrible mess and calling AOs with functions they should never be
called with; most prominently PrepareForOrdinaryCall and
OrdinaryCallBindThis, which are only for ECMAScriptFunctionObject.
As a result this also contains an implicit optimization: we no longer
need to create a new function environment for NativeFunctions - which,
worth mentioning, is what started this whole crusade in the first place
:^)
2021-10-08 20:37:21 +01:00
return { } ;
2021-08-28 17:11:05 +02:00
}
2020-09-27 15:18:55 +02:00
2021-04-13 01:02:38 +02:00
void VM : : throw_exception ( Exception & exception )
2020-09-27 15:18:55 +02:00
{
2021-04-13 01:02:38 +02:00
set_exception ( exception ) ;
2020-09-27 15:18:55 +02:00
unwind ( ScopeType : : Try ) ;
}
2021-06-25 11:40:03 +02:00
// 9.4.4 ResolveThisBinding ( ), https://tc39.es/ecma262/#sec-resolvethisbinding
Value VM : : resolve_this_binding ( GlobalObject & global_object )
{
auto & environment = get_this_environment ( * this ) ;
2021-10-09 16:52:34 +01:00
return TRY_OR_DISCARD ( environment . get_this_binding ( global_object ) ) ;
2021-06-25 11:40:03 +02:00
}
2021-04-18 17:08:14 +02:00
String VM : : join_arguments ( size_t start_index ) const
2020-09-27 15:18:55 +02:00
{
StringBuilder joined_arguments ;
2021-04-18 17:08:14 +02:00
for ( size_t i = start_index ; i < argument_count ( ) ; + + i ) {
2020-09-27 15:18:55 +02:00
joined_arguments . append ( argument ( i ) . to_string_without_side_effects ( ) . characters ( ) ) ;
if ( i ! = argument_count ( ) - 1 )
joined_arguments . append ( ' ' ) ;
}
return joined_arguments . build ( ) ;
}
2021-12-28 23:50:23 +01:00
// 9.4.5 GetNewTarget ( ), https://tc39.es/ecma262/#sec-getnewtarget
2021-06-22 13:30:48 +02:00
Value VM : : get_new_target ( )
2020-09-27 15:18:55 +02:00
{
2021-12-28 23:50:23 +01:00
// 1. Let envRec be GetThisEnvironment().
2021-06-22 13:30:48 +02:00
auto & env = get_this_environment ( * this ) ;
2021-12-28 23:50:23 +01:00
// 2. Assert: envRec has a [[NewTarget]] field.
// 3. Return envRec.[[NewTarget]].
2021-07-01 12:24:46 +02:00
return verify_cast < FunctionEnvironment > ( env ) . new_target ( ) ;
2020-09-27 15:18:55 +02:00
}
LibJS: Implement [[Call]] and [[Construct]] internal slots properly
This patch implements:
- Spec compliant [[Call]] and [[Construct]] internal slots, as virtual
FunctionObject::internal_{call,construct}(). These effectively replace
the old virtual FunctionObject::{call,construct}(), but with several
advantages:
- Clear and consistent naming, following the object internal methods
- Use of completions
- internal_construct() returns an Object, and not Value! This has been
a source of confusion for a long time, since in the spec there's
always an Object returned but the Value return type in LibJS meant
that this could not be fully trusted and something could screw you
over.
- Arguments are passed explicitly in form of a MarkedValueList,
allowing manipulation (BoundFunction). We still put them on the
execution context as a lot of code depends on it (VM::arguments()),
but not from the Call() / Construct() AOs anymore, which now allows
for bypassing them and invoking [[Call]] / [[Construct]] directly.
Nothing but Call() / Construct() themselves do that at the moment,
but future additions to ECMA262 or already existing web specs might.
- Spec compliant, standalone Call() and Construct() AOs: currently the
closest we have is VM::{call,construct}(), but those try to cater to
all the different function object subclasses at once, resulting in a
horrible mess and calling AOs with functions they should never be
called with; most prominently PrepareForOrdinaryCall and
OrdinaryCallBindThis, which are only for ECMAScriptFunctionObject.
As a result this also contains an implicit optimization: we no longer
need to create a new function environment for NativeFunctions - which,
worth mentioning, is what started this whole crusade in the first place
:^)
2021-10-08 20:37:21 +01:00
// NOTE: This is only here because there's a million invocations of vm.call() - it used to be tied to the VM in weird ways.
// We should update all of those and then remove this, along with the call() template functions in VM.h, and use the standalone call() AO.
2021-09-23 20:56:28 +03:00
ThrowCompletionOr < Value > VM : : call_internal ( FunctionObject & function , Value this_value , Optional < MarkedValueList > arguments )
2020-09-27 17:24:14 +02:00
{
2021-02-23 20:42:32 +01:00
VERIFY ( ! exception ( ) ) ;
2021-03-26 19:40:55 +01:00
VERIFY ( ! this_value . is_empty ( ) ) ;
2020-09-27 17:24:14 +02:00
LibJS: Implement [[Call]] and [[Construct]] internal slots properly
This patch implements:
- Spec compliant [[Call]] and [[Construct]] internal slots, as virtual
FunctionObject::internal_{call,construct}(). These effectively replace
the old virtual FunctionObject::{call,construct}(), but with several
advantages:
- Clear and consistent naming, following the object internal methods
- Use of completions
- internal_construct() returns an Object, and not Value! This has been
a source of confusion for a long time, since in the spec there's
always an Object returned but the Value return type in LibJS meant
that this could not be fully trusted and something could screw you
over.
- Arguments are passed explicitly in form of a MarkedValueList,
allowing manipulation (BoundFunction). We still put them on the
execution context as a lot of code depends on it (VM::arguments()),
but not from the Call() / Construct() AOs anymore, which now allows
for bypassing them and invoking [[Call]] / [[Construct]] directly.
Nothing but Call() / Construct() themselves do that at the moment,
but future additions to ECMA262 or already existing web specs might.
- Spec compliant, standalone Call() and Construct() AOs: currently the
closest we have is VM::{call,construct}(), but those try to cater to
all the different function object subclasses at once, resulting in a
horrible mess and calling AOs with functions they should never be
called with; most prominently PrepareForOrdinaryCall and
OrdinaryCallBindThis, which are only for ECMAScriptFunctionObject.
As a result this also contains an implicit optimization: we no longer
need to create a new function environment for NativeFunctions - which,
worth mentioning, is what started this whole crusade in the first place
:^)
2021-10-08 20:37:21 +01:00
return JS : : call_impl ( function . global_object ( ) , & function , this_value , move ( arguments ) ) ;
2020-09-27 17:24:14 +02:00
}
2020-10-04 13:54:44 +02:00
bool VM : : in_strict_mode ( ) const
{
2021-06-24 19:17:45 +02:00
if ( execution_context_stack ( ) . is_empty ( ) )
2020-10-04 13:54:44 +02:00
return false ;
2021-06-24 19:17:45 +02:00
return running_execution_context ( ) . is_strict_mode ;
2020-10-04 13:54:44 +02:00
}
LibJS: Add initial support for Promises
Almost a year after first working on this, it's finally done: an
implementation of Promises for LibJS! :^)
The core functionality is working and closely following the spec [1].
I mostly took the pseudo code and transformed it into C++ - if you read
and understand it, you will know how the spec implements Promises; and
if you read the spec first, the code will look very familiar.
Implemented functions are:
- Promise() constructor
- Promise.prototype.then()
- Promise.prototype.catch()
- Promise.prototype.finally()
- Promise.resolve()
- Promise.reject()
For the tests I added a new function to test-js's global object,
runQueuedPromiseJobs(), which calls vm.run_queued_promise_jobs().
By design, queued jobs normally only run after the script was fully
executed, making it improssible to test handlers in individual test()
calls by default [2].
Subsequent commits include integrations into LibWeb and js(1) -
pretty-printing, running queued promise jobs when necessary.
This has an unusual amount of dbgln() statements, all hidden behind the
PROMISE_DEBUG flag - I'm leaving them in for now as they've been very
useful while debugging this, things can get quite complex with so many
asynchronously executed functions.
I've not extensively explored use of these APIs for promise-based
functionality in LibWeb (fetch(), Notification.requestPermission()
etc.), but we'll get there in due time.
[1]: https://tc39.es/ecma262/#sec-promise-objects
[2]: https://tc39.es/ecma262/#sec-jobs-and-job-queues
2021-04-01 22:13:29 +02:00
void VM : : run_queued_promise_jobs ( )
{
dbgln_if ( PROMISE_DEBUG , " Running queued promise jobs " ) ;
// Temporarily get rid of the exception, if any - job functions must be called
// either way, and that can't happen if we already have an exception stored.
LibJS: Clear exception after running each queued Promise job
It's not what the spec tells us to do. In fact, the spec tells us the
exact opposite:
9.5 Jobs and Host Operations to Enqueue Jobs
https://tc39.es/ecma262/#sec-jobs
A Job is an Abstract Closure with no parameters that initiates an
ECMAScript computation when no other ECMAScript computation is
currently in progress.
...
Their implementations must conform to the following requirements:
- ...
- The Abstract Closure must return a normal completion, implementing
its own handling of errors.
However, this turned out to not be true in all cases. More specifically,
the NewPromiseReactionJob AO returns the completion result of calling a
user-provided function (PromiseCapability's [[Resolve]] / [[Reject]]),
which may be an abrupt completion:
27.2.2.1 NewPromiseReactionJob ( reaction, argument )
https://tc39.es/ecma262/#sec-newpromisereactionjob
1. Let job be a new Job Abstract Closure with no parameters that
captures reaction and argument and performs the following steps
when called:
...
h. If handlerResult is an abrupt completion, then
i. Let status be Call(promiseCapability.[[Reject]],
undefined, « handlerResult.[[Value]] »).
i. Else,
i. Let status be Call(promiseCapability.[[Resolve]],
undefined, « handlerResult.[[Value]] »).
j. Return Completion(status).
Interestingly, this case is explicitly handled in the HTML spec's
implementation of jobs as microtasks:
8.1.5.3.3 HostEnqueuePromiseJob(job, realm)
https://html.spec.whatwg.org/webappapis.html#hostenqueuepromisejob
2. Queue a microtask on the surrounding agent's event loop to
perform the following steps:
...
5. If result is an abrupt completion, then report the exception
given by result.[[Value]].
This is precisely what all the major engines do - but not only in
browsers; the provided code snippet in the test added in this commit
works just fine in Node.js, for example.
SpiderMonkey:
https://searchfox.org/mozilla-central/rev/25997ce8267ec9e3ea4b727e0973bd9ef02bba79/js/src/builtin/Promise.cpp#6292
https://searchfox.org/mozilla-central/rev/25997ce8267ec9e3ea4b727e0973bd9ef02bba79/js/src/builtin/Promise.cpp#1277
https://searchfox.org/mozilla-central/rev/25997ce8267ec9e3ea4b727e0973bd9ef02bba79/js/src/vm/JSContext.cpp#845
JavaScriptCore:
https://trac.webkit.org/browser/webkit/trunk/Source/JavaScriptCore/builtins/PromiseOperations.js?rev=273718#L562
https://trac.webkit.org/browser/webkit/trunk/Source/JavaScriptCore/runtime/JSMicrotask.cpp?rev=273718#L94
V8:
https://source.chromium.org/chromium/chromium/src/+/main:v8/src/builtins/promise-abstract-operations.tq;l=481;drc=a760f03a6e99bf4863d8d21c5f7896a74a0a39ea
https://source.chromium.org/chromium/chromium/src/+/main:v8/src/builtins/builtins-microtask-queue-gen.cc;l=331;drc=65c9257f1777731d6d0669598f6fe6fe65fa61d3
This should probably be fixed in the ECMAScript spec to relax the rule
that Jobs may not return an abrupt completion, just like in the HTML
spec. The important bit is that those are not surfaced to user code in
any way.
2021-11-11 23:13:58 +00:00
TemporaryClearException temporary_clear_exception ( * this ) ;
LibJS: Add initial support for Promises
Almost a year after first working on this, it's finally done: an
implementation of Promises for LibJS! :^)
The core functionality is working and closely following the spec [1].
I mostly took the pseudo code and transformed it into C++ - if you read
and understand it, you will know how the spec implements Promises; and
if you read the spec first, the code will look very familiar.
Implemented functions are:
- Promise() constructor
- Promise.prototype.then()
- Promise.prototype.catch()
- Promise.prototype.finally()
- Promise.resolve()
- Promise.reject()
For the tests I added a new function to test-js's global object,
runQueuedPromiseJobs(), which calls vm.run_queued_promise_jobs().
By design, queued jobs normally only run after the script was fully
executed, making it improssible to test handlers in individual test()
calls by default [2].
Subsequent commits include integrations into LibWeb and js(1) -
pretty-printing, running queued promise jobs when necessary.
This has an unusual amount of dbgln() statements, all hidden behind the
PROMISE_DEBUG flag - I'm leaving them in for now as they've been very
useful while debugging this, things can get quite complex with so many
asynchronously executed functions.
I've not extensively explored use of these APIs for promise-based
functionality in LibWeb (fetch(), Notification.requestPermission()
etc.), but we'll get there in due time.
[1]: https://tc39.es/ecma262/#sec-promise-objects
[2]: https://tc39.es/ecma262/#sec-jobs-and-job-queues
2021-04-01 22:13:29 +02:00
while ( ! m_promise_jobs . is_empty ( ) ) {
auto * job = m_promise_jobs . take_first ( ) ;
dbgln_if ( PROMISE_DEBUG , " Calling promise job function @ {} " , job ) ;
2021-10-11 22:19:46 +02:00
// NOTE: If the execution context stack is empty, we make and push a temporary context.
ExecutionContext execution_context ( heap ( ) ) ;
bool pushed_execution_context = false ;
if ( m_execution_context_stack . is_empty ( ) ) {
static FlyString promise_execution_context_name = " (promise execution context) " ;
execution_context . function_name = promise_execution_context_name ;
2021-11-14 12:20:49 +00:00
// FIXME: Propagate potential failure
MUST ( push_execution_context ( execution_context , job - > global_object ( ) ) ) ;
2021-10-11 22:19:46 +02:00
pushed_execution_context = true ;
}
LibJS: Add initial support for Promises
Almost a year after first working on this, it's finally done: an
implementation of Promises for LibJS! :^)
The core functionality is working and closely following the spec [1].
I mostly took the pseudo code and transformed it into C++ - if you read
and understand it, you will know how the spec implements Promises; and
if you read the spec first, the code will look very familiar.
Implemented functions are:
- Promise() constructor
- Promise.prototype.then()
- Promise.prototype.catch()
- Promise.prototype.finally()
- Promise.resolve()
- Promise.reject()
For the tests I added a new function to test-js's global object,
runQueuedPromiseJobs(), which calls vm.run_queued_promise_jobs().
By design, queued jobs normally only run after the script was fully
executed, making it improssible to test handlers in individual test()
calls by default [2].
Subsequent commits include integrations into LibWeb and js(1) -
pretty-printing, running queued promise jobs when necessary.
This has an unusual amount of dbgln() statements, all hidden behind the
PROMISE_DEBUG flag - I'm leaving them in for now as they've been very
useful while debugging this, things can get quite complex with so many
asynchronously executed functions.
I've not extensively explored use of these APIs for promise-based
functionality in LibWeb (fetch(), Notification.requestPermission()
etc.), but we'll get there in due time.
[1]: https://tc39.es/ecma262/#sec-promise-objects
[2]: https://tc39.es/ecma262/#sec-jobs-and-job-queues
2021-04-01 22:13:29 +02:00
[[maybe_unused]] auto result = call ( * job , js_undefined ( ) ) ;
2021-10-11 22:19:46 +02:00
LibJS: Clear exception after running each queued Promise job
It's not what the spec tells us to do. In fact, the spec tells us the
exact opposite:
9.5 Jobs and Host Operations to Enqueue Jobs
https://tc39.es/ecma262/#sec-jobs
A Job is an Abstract Closure with no parameters that initiates an
ECMAScript computation when no other ECMAScript computation is
currently in progress.
...
Their implementations must conform to the following requirements:
- ...
- The Abstract Closure must return a normal completion, implementing
its own handling of errors.
However, this turned out to not be true in all cases. More specifically,
the NewPromiseReactionJob AO returns the completion result of calling a
user-provided function (PromiseCapability's [[Resolve]] / [[Reject]]),
which may be an abrupt completion:
27.2.2.1 NewPromiseReactionJob ( reaction, argument )
https://tc39.es/ecma262/#sec-newpromisereactionjob
1. Let job be a new Job Abstract Closure with no parameters that
captures reaction and argument and performs the following steps
when called:
...
h. If handlerResult is an abrupt completion, then
i. Let status be Call(promiseCapability.[[Reject]],
undefined, « handlerResult.[[Value]] »).
i. Else,
i. Let status be Call(promiseCapability.[[Resolve]],
undefined, « handlerResult.[[Value]] »).
j. Return Completion(status).
Interestingly, this case is explicitly handled in the HTML spec's
implementation of jobs as microtasks:
8.1.5.3.3 HostEnqueuePromiseJob(job, realm)
https://html.spec.whatwg.org/webappapis.html#hostenqueuepromisejob
2. Queue a microtask on the surrounding agent's event loop to
perform the following steps:
...
5. If result is an abrupt completion, then report the exception
given by result.[[Value]].
This is precisely what all the major engines do - but not only in
browsers; the provided code snippet in the test added in this commit
works just fine in Node.js, for example.
SpiderMonkey:
https://searchfox.org/mozilla-central/rev/25997ce8267ec9e3ea4b727e0973bd9ef02bba79/js/src/builtin/Promise.cpp#6292
https://searchfox.org/mozilla-central/rev/25997ce8267ec9e3ea4b727e0973bd9ef02bba79/js/src/builtin/Promise.cpp#1277
https://searchfox.org/mozilla-central/rev/25997ce8267ec9e3ea4b727e0973bd9ef02bba79/js/src/vm/JSContext.cpp#845
JavaScriptCore:
https://trac.webkit.org/browser/webkit/trunk/Source/JavaScriptCore/builtins/PromiseOperations.js?rev=273718#L562
https://trac.webkit.org/browser/webkit/trunk/Source/JavaScriptCore/runtime/JSMicrotask.cpp?rev=273718#L94
V8:
https://source.chromium.org/chromium/chromium/src/+/main:v8/src/builtins/promise-abstract-operations.tq;l=481;drc=a760f03a6e99bf4863d8d21c5f7896a74a0a39ea
https://source.chromium.org/chromium/chromium/src/+/main:v8/src/builtins/builtins-microtask-queue-gen.cc;l=331;drc=65c9257f1777731d6d0669598f6fe6fe65fa61d3
This should probably be fixed in the ECMAScript spec to relax the rule
that Jobs may not return an abrupt completion, just like in the HTML
spec. The important bit is that those are not surfaced to user code in
any way.
2021-11-11 23:13:58 +00:00
// This doesn't match the spec, it actually defines that Job Abstract Closures must return
// a normal completion. In reality that's not the case however, and all major engines clear
// exceptions when running Promise jobs. See the commit where these two lines were initially
// added for a much more detailed explanation.
clear_exception ( ) ;
stop_unwind ( ) ;
2021-10-11 22:19:46 +02:00
if ( pushed_execution_context )
pop_execution_context ( ) ;
LibJS: Add initial support for Promises
Almost a year after first working on this, it's finally done: an
implementation of Promises for LibJS! :^)
The core functionality is working and closely following the spec [1].
I mostly took the pseudo code and transformed it into C++ - if you read
and understand it, you will know how the spec implements Promises; and
if you read the spec first, the code will look very familiar.
Implemented functions are:
- Promise() constructor
- Promise.prototype.then()
- Promise.prototype.catch()
- Promise.prototype.finally()
- Promise.resolve()
- Promise.reject()
For the tests I added a new function to test-js's global object,
runQueuedPromiseJobs(), which calls vm.run_queued_promise_jobs().
By design, queued jobs normally only run after the script was fully
executed, making it improssible to test handlers in individual test()
calls by default [2].
Subsequent commits include integrations into LibWeb and js(1) -
pretty-printing, running queued promise jobs when necessary.
This has an unusual amount of dbgln() statements, all hidden behind the
PROMISE_DEBUG flag - I'm leaving them in for now as they've been very
useful while debugging this, things can get quite complex with so many
asynchronously executed functions.
I've not extensively explored use of these APIs for promise-based
functionality in LibWeb (fetch(), Notification.requestPermission()
etc.), but we'll get there in due time.
[1]: https://tc39.es/ecma262/#sec-promise-objects
[2]: https://tc39.es/ecma262/#sec-jobs-and-job-queues
2021-04-01 22:13:29 +02:00
}
// Ensure no job has created a new exception, they must clean up after themselves.
LibJS: Clear exception after running each queued Promise job
It's not what the spec tells us to do. In fact, the spec tells us the
exact opposite:
9.5 Jobs and Host Operations to Enqueue Jobs
https://tc39.es/ecma262/#sec-jobs
A Job is an Abstract Closure with no parameters that initiates an
ECMAScript computation when no other ECMAScript computation is
currently in progress.
...
Their implementations must conform to the following requirements:
- ...
- The Abstract Closure must return a normal completion, implementing
its own handling of errors.
However, this turned out to not be true in all cases. More specifically,
the NewPromiseReactionJob AO returns the completion result of calling a
user-provided function (PromiseCapability's [[Resolve]] / [[Reject]]),
which may be an abrupt completion:
27.2.2.1 NewPromiseReactionJob ( reaction, argument )
https://tc39.es/ecma262/#sec-newpromisereactionjob
1. Let job be a new Job Abstract Closure with no parameters that
captures reaction and argument and performs the following steps
when called:
...
h. If handlerResult is an abrupt completion, then
i. Let status be Call(promiseCapability.[[Reject]],
undefined, « handlerResult.[[Value]] »).
i. Else,
i. Let status be Call(promiseCapability.[[Resolve]],
undefined, « handlerResult.[[Value]] »).
j. Return Completion(status).
Interestingly, this case is explicitly handled in the HTML spec's
implementation of jobs as microtasks:
8.1.5.3.3 HostEnqueuePromiseJob(job, realm)
https://html.spec.whatwg.org/webappapis.html#hostenqueuepromisejob
2. Queue a microtask on the surrounding agent's event loop to
perform the following steps:
...
5. If result is an abrupt completion, then report the exception
given by result.[[Value]].
This is precisely what all the major engines do - but not only in
browsers; the provided code snippet in the test added in this commit
works just fine in Node.js, for example.
SpiderMonkey:
https://searchfox.org/mozilla-central/rev/25997ce8267ec9e3ea4b727e0973bd9ef02bba79/js/src/builtin/Promise.cpp#6292
https://searchfox.org/mozilla-central/rev/25997ce8267ec9e3ea4b727e0973bd9ef02bba79/js/src/builtin/Promise.cpp#1277
https://searchfox.org/mozilla-central/rev/25997ce8267ec9e3ea4b727e0973bd9ef02bba79/js/src/vm/JSContext.cpp#845
JavaScriptCore:
https://trac.webkit.org/browser/webkit/trunk/Source/JavaScriptCore/builtins/PromiseOperations.js?rev=273718#L562
https://trac.webkit.org/browser/webkit/trunk/Source/JavaScriptCore/runtime/JSMicrotask.cpp?rev=273718#L94
V8:
https://source.chromium.org/chromium/chromium/src/+/main:v8/src/builtins/promise-abstract-operations.tq;l=481;drc=a760f03a6e99bf4863d8d21c5f7896a74a0a39ea
https://source.chromium.org/chromium/chromium/src/+/main:v8/src/builtins/builtins-microtask-queue-gen.cc;l=331;drc=65c9257f1777731d6d0669598f6fe6fe65fa61d3
This should probably be fixed in the ECMAScript spec to relax the rule
that Jobs may not return an abrupt completion, just like in the HTML
spec. The important bit is that those are not surfaced to user code in
any way.
2021-11-11 23:13:58 +00:00
// If they don't, we help a little (see above) so that this assumption remains valid.
LibJS: Add initial support for Promises
Almost a year after first working on this, it's finally done: an
implementation of Promises for LibJS! :^)
The core functionality is working and closely following the spec [1].
I mostly took the pseudo code and transformed it into C++ - if you read
and understand it, you will know how the spec implements Promises; and
if you read the spec first, the code will look very familiar.
Implemented functions are:
- Promise() constructor
- Promise.prototype.then()
- Promise.prototype.catch()
- Promise.prototype.finally()
- Promise.resolve()
- Promise.reject()
For the tests I added a new function to test-js's global object,
runQueuedPromiseJobs(), which calls vm.run_queued_promise_jobs().
By design, queued jobs normally only run after the script was fully
executed, making it improssible to test handlers in individual test()
calls by default [2].
Subsequent commits include integrations into LibWeb and js(1) -
pretty-printing, running queued promise jobs when necessary.
This has an unusual amount of dbgln() statements, all hidden behind the
PROMISE_DEBUG flag - I'm leaving them in for now as they've been very
useful while debugging this, things can get quite complex with so many
asynchronously executed functions.
I've not extensively explored use of these APIs for promise-based
functionality in LibWeb (fetch(), Notification.requestPermission()
etc.), but we'll get there in due time.
[1]: https://tc39.es/ecma262/#sec-promise-objects
[2]: https://tc39.es/ecma262/#sec-jobs-and-job-queues
2021-04-01 22:13:29 +02:00
VERIFY ( ! m_exception ) ;
}
2021-06-13 00:22:35 +01:00
// 9.5.4 HostEnqueuePromiseJob ( job, realm ), https://tc39.es/ecma262/#sec-hostenqueuepromisejob
LibJS: Add initial support for Promises
Almost a year after first working on this, it's finally done: an
implementation of Promises for LibJS! :^)
The core functionality is working and closely following the spec [1].
I mostly took the pseudo code and transformed it into C++ - if you read
and understand it, you will know how the spec implements Promises; and
if you read the spec first, the code will look very familiar.
Implemented functions are:
- Promise() constructor
- Promise.prototype.then()
- Promise.prototype.catch()
- Promise.prototype.finally()
- Promise.resolve()
- Promise.reject()
For the tests I added a new function to test-js's global object,
runQueuedPromiseJobs(), which calls vm.run_queued_promise_jobs().
By design, queued jobs normally only run after the script was fully
executed, making it improssible to test handlers in individual test()
calls by default [2].
Subsequent commits include integrations into LibWeb and js(1) -
pretty-printing, running queued promise jobs when necessary.
This has an unusual amount of dbgln() statements, all hidden behind the
PROMISE_DEBUG flag - I'm leaving them in for now as they've been very
useful while debugging this, things can get quite complex with so many
asynchronously executed functions.
I've not extensively explored use of these APIs for promise-based
functionality in LibWeb (fetch(), Notification.requestPermission()
etc.), but we'll get there in due time.
[1]: https://tc39.es/ecma262/#sec-promise-objects
[2]: https://tc39.es/ecma262/#sec-jobs-and-job-queues
2021-04-01 22:13:29 +02:00
void VM : : enqueue_promise_job ( NativeFunction & job )
{
m_promise_jobs . append ( & job ) ;
}
2021-06-15 22:16:17 +03:00
void VM : : run_queued_finalization_registry_cleanup_jobs ( )
{
while ( ! m_finalization_registry_cleanup_jobs . is_empty ( ) ) {
auto * registry = m_finalization_registry_cleanup_jobs . take_first ( ) ;
registry - > cleanup ( ) ;
}
}
// 9.10.4.1 HostEnqueueFinalizationRegistryCleanupJob ( finalizationRegistry ), https://tc39.es/ecma262/#sec-host-cleanup-finalization-registry
void VM : : enqueue_finalization_registry_cleanup_job ( FinalizationRegistry & registry )
{
m_finalization_registry_cleanup_jobs . append ( & registry ) ;
}
2021-06-13 00:22:35 +01:00
// 27.2.1.9 HostPromiseRejectionTracker ( promise, operation ), https://tc39.es/ecma262/#sec-host-promise-rejection-tracker
LibJS: Add initial support for Promises
Almost a year after first working on this, it's finally done: an
implementation of Promises for LibJS! :^)
The core functionality is working and closely following the spec [1].
I mostly took the pseudo code and transformed it into C++ - if you read
and understand it, you will know how the spec implements Promises; and
if you read the spec first, the code will look very familiar.
Implemented functions are:
- Promise() constructor
- Promise.prototype.then()
- Promise.prototype.catch()
- Promise.prototype.finally()
- Promise.resolve()
- Promise.reject()
For the tests I added a new function to test-js's global object,
runQueuedPromiseJobs(), which calls vm.run_queued_promise_jobs().
By design, queued jobs normally only run after the script was fully
executed, making it improssible to test handlers in individual test()
calls by default [2].
Subsequent commits include integrations into LibWeb and js(1) -
pretty-printing, running queued promise jobs when necessary.
This has an unusual amount of dbgln() statements, all hidden behind the
PROMISE_DEBUG flag - I'm leaving them in for now as they've been very
useful while debugging this, things can get quite complex with so many
asynchronously executed functions.
I've not extensively explored use of these APIs for promise-based
functionality in LibWeb (fetch(), Notification.requestPermission()
etc.), but we'll get there in due time.
[1]: https://tc39.es/ecma262/#sec-promise-objects
[2]: https://tc39.es/ecma262/#sec-jobs-and-job-queues
2021-04-01 22:13:29 +02:00
void VM : : promise_rejection_tracker ( const Promise & promise , Promise : : RejectionOperation operation ) const
{
switch ( operation ) {
case Promise : : RejectionOperation : : Reject :
// A promise was rejected without any handlers
if ( on_promise_unhandled_rejection )
on_promise_unhandled_rejection ( promise ) ;
break ;
case Promise : : RejectionOperation : : Handle :
// A handler was added to an already rejected promise
if ( on_promise_rejection_handled )
on_promise_rejection_handled ( promise ) ;
break ;
default :
VERIFY_NOT_REACHED ( ) ;
}
}
2021-06-06 22:53:44 +02:00
void VM : : dump_backtrace ( ) const
{
2021-09-11 17:01:19 +02:00
for ( ssize_t i = m_execution_context_stack . size ( ) - 1 ; i > = 0 ; - - i ) {
auto & frame = m_execution_context_stack [ i ] ;
if ( frame - > current_node ) {
auto & source_range = frame - > current_node - > source_range ( ) ;
dbgln ( " -> {} @ {}:{},{} " , frame - > function_name , source_range . filename , source_range . start . line , source_range . start . column ) ;
} else {
dbgln ( " -> {} " , frame - > function_name ) ;
}
}
2021-06-06 22:53:44 +02:00
}
2021-09-08 22:58:36 +02:00
VM : : CustomData : : ~ CustomData ( )
{
}
2021-10-03 14:52:53 +02:00
void VM : : save_execution_context_stack ( )
{
m_saved_execution_context_stacks . append ( move ( m_execution_context_stack ) ) ;
}
void VM : : restore_execution_context_stack ( )
{
m_execution_context_stack = m_saved_execution_context_stacks . take_last ( ) ;
}
2020-09-20 19:24:44 +02:00
}