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07a36c8f80
Doing things in the destructor of a GC-allocated object isn't always safe, in case it involves accessing other GC-allocated objects. If they were already swept by GC, we'd be poking into freed memory. This patch adds a separate finalization pass where GC calls finalize() on every unmarked cell that's about to be deleted. It's safe to access other GC objects in finalize(), even if they're also unmarked.
104 lines
2.5 KiB
C++
104 lines
2.5 KiB
C++
/*
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* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Format.h>
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#include <AK/Forward.h>
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#include <AK/Noncopyable.h>
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#include <AK/StringView.h>
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#include <LibJS/Forward.h>
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#include <LibJS/Heap/GCPtr.h>
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namespace JS {
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#define JS_CELL(class_, base_class) \
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public: \
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using Base = base_class; \
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virtual StringView class_name() const override \
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{ \
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return #class_##sv; \
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} \
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friend class JS::Heap;
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class Cell {
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AK_MAKE_NONCOPYABLE(Cell);
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AK_MAKE_NONMOVABLE(Cell);
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public:
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virtual void initialize(Realm&) { }
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virtual ~Cell() = default;
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bool is_marked() const { return m_mark; }
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void set_marked(bool b) { m_mark = b; }
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enum class State {
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Live,
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Dead,
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};
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State state() const { return m_state; }
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void set_state(State state) { m_state = state; }
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virtual StringView class_name() const = 0;
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class Visitor {
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public:
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void visit(Cell* cell)
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{
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if (cell)
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visit_impl(*cell);
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}
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void visit(Cell& cell)
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{
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visit_impl(cell);
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}
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template<typename T>
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void visit(GCPtr<T> cell)
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{
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if (cell)
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visit_impl(*cell.ptr());
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}
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template<typename T>
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void visit(NonnullGCPtr<T> cell)
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{
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visit_impl(*cell.ptr());
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}
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void visit(Value);
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protected:
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virtual void visit_impl(Cell&) = 0;
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virtual ~Visitor() = default;
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};
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virtual bool is_environment() const { return false; }
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virtual void visit_edges(Visitor&) { }
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// This will be called on unmarked objects by the garbage collector in a separate pass before destruction.
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virtual void finalize() { }
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Heap& heap() const;
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VM& vm() const;
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protected:
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Cell() = default;
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private:
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bool m_mark : 1 { false };
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State m_state : 7 { State::Live };
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};
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}
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template<>
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struct AK::Formatter<JS::Cell> : AK::Formatter<FormatString> {
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ErrorOr<void> format(FormatBuilder& builder, JS::Cell const* cell)
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{
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if (!cell)
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return builder.put_string("Cell{nullptr}"sv);
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return Formatter<FormatString>::format(builder, "{}({})"sv, cell->class_name(), cell);
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}
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};
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