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LibJS: Do not allocate in Set's constructor

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We are currently allocating in Set's constructor to create the set's
underlying Map. This can cause GC to occur before the member is actually
initialized, thus we will crash in Set::visit_edges trying to visit a
member that does not exist.

Instead, create the Map in Set::initialize, where we can allocate. Also
change Map to be stored as a normal JS heap-allocated object, rather
than as a stack variable.
This commit is contained in:
Timothy Flynn 2022-11-30 09:18:27 -05:00 committed by Tim Flynn
parent 715e56a74c
commit c0952e3670
Notes: sideshowbarker 2024-07-17 03:49:40 +09:00 
Author: https://github.com/trflynn89
Commit: https://github.com/SerenityOS/serenity/commit/c0952e3670
Pull-request: https://github.com/SerenityOS/serenity/pull/16266
Reviewed-by: https://github.com/awesomekling ✅
3 changed files with 16 additions and 14 deletions
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3
Userland/Libraries/LibJS/Runtime/Map.h
View file

@ -19,9 +19,6 @@ namespace JS {
class Map : public Object {
JS_OBJECT(Map, Object);
// NOTE: This awkwardness is due to Set using a Map internally.
friend class Set;
public:
static Map* create(Realm&);

8
Userland/Libraries/LibJS/Runtime/Set.cpp
View file

@ -15,14 +15,18 @@ Set* Set::create(Realm& realm)
Set::Set(Object& prototype)
: Object(prototype)
, m_values(*prototype.shape().realm().intrinsics().map_prototype())
{
}
void Set::initialize(Realm& realm)
{
m_values = Map::create(realm);
}
void Set::visit_edges(Cell::Visitor& visitor)
{
Base::visit_edges(visitor);
static_cast<Object&>(m_values).visit_edges(visitor);
visitor.visit(m_values);
}
}

19
Userland/Libraries/LibJS/Runtime/Set.h
View file

@ -19,28 +19,29 @@ class Set : public Object {
public:
static Set* create(Realm&);
virtual void initialize(Realm&) override;
virtual ~Set() override = default;
// NOTE: Unlike what the spec says, we implement Sets using an underlying map,
// so all the functions below do not directly implement the operations as
// defined by the specification.
void set_clear() { m_values.map_clear(); }
bool set_remove(Value const& value) { return m_values.map_remove(value); }
bool set_has(Value const& key) const { return m_values.map_has(key); }
void set_add(Value const& key) { m_values.map_set(key, js_undefined()); }
size_t set_size() const { return m_values.map_size(); }
void set_clear() { m_values->map_clear(); }
bool set_remove(Value const& value) { return m_values->map_remove(value); }
bool set_has(Value const& key) const { return m_values->map_has(key); }
void set_add(Value const& key) { m_values->map_set(key, js_undefined()); }
size_t set_size() const { return m_values->map_size(); }
auto begin() const { return m_values.begin(); }
auto begin() { return m_values.begin(); }
auto end() const { return m_values.end(); }
auto begin() const { return const_cast<Map const&>(*m_values).begin(); }
auto begin() { return m_values->begin(); }
auto end() const { return m_values->end(); }
private:
explicit Set(Object& prototype);
virtual void visit_edges(Visitor& visitor) override;
Map m_values;
GCPtr<Map> m_values;
};
}