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LibJS: Protect function call "this" and arguments from GC

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This patch adds a CallFrame stack to Interpreter, which keeps track of
the "this" value and all argument values passed in function calls.

Interpreter::gather_roots() scans the call stack, making sure that all
argument values get marked. :^)
This commit is contained in:
Andreas Kling 2020-03-17 11:00:09 +01:00
parent 666f84b933
commit bf9912cc59
3 changed files with 22 additions and 19 deletions
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16
Libraries/LibJS/AST.cpp
View file

@ -59,21 +59,15 @@ Value CallExpression::execute(Interpreter& interpreter) const
ASSERT(callee.as_object()->is_function());
auto* function = static_cast<Function*>(callee.as_object());
Vector<Value> argument_values;
auto& call_frame = interpreter.push_call_frame();
for (size_t i = 0; i < m_arguments.size(); ++i)
argument_values.append(m_arguments[i].execute(interpreter));
call_frame.arguments.append(m_arguments[i].execute(interpreter));
Value this_value = js_undefined();
if (m_callee->is_member_expression())
this_value = static_cast<const MemberExpression&>(*m_callee).object().execute(interpreter).to_object(interpreter.heap());
call_frame.this_value = static_cast<const MemberExpression&>(*m_callee).object().execute(interpreter).to_object(interpreter.heap());
if (!this_value.is_undefined())
interpreter.push_this_value(this_value);
auto result = function->call(interpreter, move(argument_values));
if (!this_value.is_undefined())
interpreter.pop_this_value();
auto result = function->call(interpreter, call_frame.arguments);
interpreter.pop_call_frame();
return result;
}

10
Libraries/LibJS/Interpreter.cpp
View file

@ -151,9 +151,13 @@ void Interpreter::gather_roots(Badge<Heap>, HashTable<Cell*>& roots)
}
}
for (auto& this_value : m_this_stack) {
if (this_value.is_cell())
roots.set(this_value.as_cell());
for (auto& call_frame : m_call_stack) {
if (call_frame.this_value.is_cell())
roots.set(call_frame.this_value.as_cell());
for (auto& argument : call_frame.arguments) {
if (argument.is_cell())
roots.set(argument.as_cell());
}
}
}

15
Libraries/LibJS/Interpreter.h
View file

@ -51,6 +51,11 @@ struct ScopeFrame {
HashMap<String, Variable> variables;
};
struct CallFrame {
Value this_value;
Vector<Value> arguments;
};
struct Argument {
String name;
Value value;
@ -79,13 +84,13 @@ public:
void enter_scope(const ScopeNode&, Vector<Argument>, ScopeType);
void exit_scope(const ScopeNode&);
void push_this_value(Value value) { m_this_stack.append(move(value)); }
void pop_this_value() { m_this_stack.take_last(); }
CallFrame& push_call_frame() { m_call_stack.append({ js_undefined(), {} }); return m_call_stack.last(); }
void pop_call_frame() { m_call_stack.take_last(); }
Value this_value() const
{
if (m_this_stack.is_empty())
if (m_call_stack.is_empty())
return m_global_object;
return m_this_stack.last();
return m_call_stack.last().this_value;
}
Object* string_prototype() { return m_string_prototype; }
@ -95,7 +100,7 @@ private:
Heap m_heap;
Vector<ScopeFrame> m_scope_stack;
Vector<Value> m_this_stack;
Vector<CallFrame> m_call_stack;
Object* m_global_object { nullptr };
Object* m_string_prototype { nullptr };