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LibJS/Bytecode: Create global variables before setting them

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This allows them to be accessed before assignment, and also prevents
throwing in strict mode as we are trying to set a non-existent
variable.
This commit is contained in:
Luke Wilde 2022-07-17 19:06:44 +01:00 • committed by Linus Groh
parent 12e3abc9e7
commit c55a4c7f30
3 changed files with 25 additions and 13 deletions
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13
Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
View file

@ -181,9 +181,7 @@ Bytecode::CodeGenerationErrorOr<void> ScopeNode::generate_bytecode(Bytecode::Gen
// ii. If declaredFunctionOrVarNames does not contain F, then
if (!declared_function_names.contains(function_name) && !declared_var_names.contains(function_name)) {
// i. Perform ? env.CreateGlobalVarBinding(F, false).
generator.emit<Bytecode::Op::CreateVariable>(index, Bytecode::Op::EnvironmentMode::Var, false);
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
generator.emit<Bytecode::Op::SetVariable>(index, Bytecode::Op::SetVariable::InitializationMode::Initialize, Bytecode::Op::EnvironmentMode::Var);
generator.emit<Bytecode::Op::CreateVariable>(index, Bytecode::Op::EnvironmentMode::Var, false, true);
// ii. Append F to declaredFunctionOrVarNames.
declared_function_names.set(function_name);
@ -238,9 +236,12 @@ Bytecode::CodeGenerationErrorOr<void> ScopeNode::generate_bytecode(Bytecode::Gen
}
// 17. For each String vn of declaredVarNames, do
// a. Perform ? env.CreateGlobalVarBinding(vn, false).
for (auto& var_name : declared_var_names)
generator.register_binding(generator.intern_identifier(var_name), Bytecode::Generator::BindingMode::Var);
for (auto& var_name : declared_var_names) {
// a. Perform ? env.CreateGlobalVarBinding(vn, false).
auto index = generator.intern_identifier(var_name);
generator.register_binding(index, Bytecode::Generator::BindingMode::Var);
generator.emit<Bytecode::Op::CreateVariable>(index, Bytecode::Op::EnvironmentMode::Var, false, true);
}
} else {
// Perform the steps of FunctionDeclarationInstantiation.
generator.begin_variable_scope(Bytecode::Generator::BindingMode::Var, Bytecode::Generator::SurroundingScopeKind::Function);

19
Userland/Libraries/LibJS/Bytecode/Op.cpp
View file

@ -15,6 +15,7 @@
#include <LibJS/Runtime/DeclarativeEnvironment.h>
#include <LibJS/Runtime/ECMAScriptFunctionObject.h>
#include <LibJS/Runtime/Environment.h>
#include <LibJS/Runtime/GlobalEnvironment.h>
#include <LibJS/Runtime/GlobalObject.h>
#include <LibJS/Runtime/Iterator.h>
#include <LibJS/Runtime/IteratorOperations.h>
@ -339,6 +340,8 @@ ThrowCompletionOr<void> CreateVariable::execute_impl(Bytecode::Interpreter& inte
auto const& name = interpreter.current_executable().get_identifier(m_identifier);
if (m_mode == EnvironmentMode::Lexical) {
VERIFY(!m_is_global);
// Note: This is papering over an issue where "FunctionDeclarationInstantiation" creates these bindings for us.
// Instead of crashing in there, we'll just raise an exception here.
if (TRY(vm.lexical_environment()->has_binding(name)))
@ -349,10 +352,16 @@ ThrowCompletionOr<void> CreateVariable::execute_impl(Bytecode::Interpreter& inte
else
vm.lexical_environment()->create_mutable_binding(interpreter.global_object(), name, vm.in_strict_mode());
} else {
if (m_is_immutable)
vm.variable_environment()->create_immutable_binding(interpreter.global_object(), name, vm.in_strict_mode());
else
vm.variable_environment()->create_mutable_binding(interpreter.global_object(), name, vm.in_strict_mode());
if (!m_is_global) {
if (m_is_immutable)
vm.variable_environment()->create_immutable_binding(interpreter.global_object(), name, vm.in_strict_mode());
else
vm.variable_environment()->create_mutable_binding(interpreter.global_object(), name, vm.in_strict_mode());
} else {
// NOTE: CreateVariable with m_is_global set to true is expected to only be used in GlobalDeclarationInstantiation currently, which only uses "false" for "can_be_deleted".
// The only area that sets "can_be_deleted" to true is EvalDeclarationInstantiation, which is currently fully implemented in C++ and not in Bytecode.
verify_cast<GlobalEnvironment>(vm.variable_environment())->create_global_var_binding(name, false);
}
}
return {};
}
@ -882,7 +891,7 @@ String CreateEnvironment::to_string_impl(Bytecode::Executable const&) const
String CreateVariable::to_string_impl(Bytecode::Executable const& executable) const
{
auto mode_string = m_mode == EnvironmentMode::Lexical ? "Lexical" : "Variable";
return String::formatted("CreateVariable env:{} immutable:{} {} ({})", mode_string, m_is_immutable, m_identifier, executable.identifier_table->get(m_identifier));
return String::formatted("CreateVariable env:{} immutable:{} global:{} {} ({})", mode_string, m_is_immutable, m_is_global, m_identifier, executable.identifier_table->get(m_identifier));
}
String EnterObjectEnvironment::to_string_impl(Executable const&) const

6
Userland/Libraries/LibJS/Bytecode/Op.h
View file

@ -317,11 +317,12 @@ public:
class CreateVariable final : public Instruction {
public:
explicit CreateVariable(IdentifierTableIndex identifier, EnvironmentMode mode, bool is_immutable)
explicit CreateVariable(IdentifierTableIndex identifier, EnvironmentMode mode, bool is_immutable, bool is_global = false)
: Instruction(Type::CreateVariable)
, m_identifier(identifier)
, m_mode(mode)
, m_is_immutable(is_immutable)
, m_is_global(is_global)
{
}
@ -332,7 +333,8 @@ public:
private:
IdentifierTableIndex m_identifier;
EnvironmentMode m_mode;
bool m_is_immutable { false };
bool m_is_immutable : 4 { false };
bool m_is_global : 4 { false };
};
class SetVariable final : public Instruction {