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/*
* Copyright (C) 2025 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <JavaScriptCore/Structure.h>
#include <JavaScriptCore/WasmTypeDefinition.h>
#include <wtf/ReferenceWrapperVector.h>
#if ENABLE(WEBASSEMBLY)
namespace WTF {
class UniquedStringImpl;
} // namespace WTF
namespace JSC {
// A set of all TypeDefinitions a WebAssemblyGCStructure needs to keep alive.
// The TypeDefinition retained by a structure as `m_type` may reference other
// TypeDefinitions. Such references are stored as raw pointers in Wasm::FieldTypes. To
// prevent these unmanaged pointers from dangling if a GC object and its structure outlive
// the originating Wasm instance, we collect a transitive closure of all TypeDefinitions
// reachable from the declared type of the GC object. The structure holds onto this set
// to ensure all relevant type definitions live for at least as long as itself.
class WebAssemblyGCStructureTypeDependencies {
public:
WebAssemblyGCStructureTypeDependencies(Ref<const Wasm::TypeDefinition>&& unexpandedType);
private:
using WorkList = ReferenceWrapperVector<const Wasm::TypeDefinition>;
void process(const Wasm::TypeDefinition&, WorkList&);
void process(Wasm::FieldType, WorkList&);
UncheckedKeyHashSet<Wasm::TypeHash> m_typeDefinitions;
};
// FIXME: It seems like almost all the fields of a Structure are useless to a wasm GC "object" since they can't have dynamic fields
// e.g. PropertyTables, Transitions, SeenProperties, Prototype, etc.
class WebAssemblyGCStructure final : public Structure {
using Base = Structure;
public:
friend class Structure;
static constexpr unsigned inlinedTypeDisplaySize = 6;
template<typename CellType, SubspaceAccess>
static GCClient::IsoSubspace* subspaceFor(VM& vm)
{
return &vm.webAssemblyGCStructureSpace();
}
const Wasm::RTT& rtt() const LIFETIME_BOUND { return m_rtt; }
const Wasm::TypeDefinition& typeDefinition() const LIFETIME_BOUND { return m_type; }
static WebAssemblyGCStructure* create(VM&, JSGlobalObject*, const TypeInfo&, const ClassInfo*, Ref<const Wasm::TypeDefinition>&& unexpandedType, Ref<const Wasm::TypeDefinition>&& expandedType, Ref<const Wasm::RTT>&&);
static constexpr ptrdiff_t offsetOfRTT() { return OBJECT_OFFSETOF(WebAssemblyGCStructure, m_rtt); }
static constexpr ptrdiff_t offsetOfInlinedTypeDisplay() { return OBJECT_OFFSETOF(WebAssemblyGCStructure, m_inlinedTypeDisplay); }
private:
WebAssemblyGCStructure(VM&, JSGlobalObject*, const TypeInfo&, const ClassInfo*, Ref<const Wasm::TypeDefinition>&& unexpandedType, Ref<const Wasm::TypeDefinition>&& expandedType, Ref<const Wasm::RTT>&&);
WebAssemblyGCStructure(VM&, WebAssemblyGCStructure* previous);
Ref<const Wasm::RTT> m_rtt;
Ref<const Wasm::TypeDefinition> m_type;
std::array<RefPtr<const Wasm::RTT>, inlinedTypeDisplaySize> m_inlinedTypeDisplay { };
WebAssemblyGCStructureTypeDependencies m_typeDependencies;
};
} // namespace JSC
SPECIALIZE_TYPE_TRAITS_BEGIN(JSC::WebAssemblyGCStructure)
static bool isType(const JSC::Structure& from)
{
return from.variant() == JSC::Structure::StructureVariant::WebAssemblyGC;
}
SPECIALIZE_TYPE_TRAITS_END()
#endif // ENABLE(WEBASSEMBLY)
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