flutter_flutter/engine/platform/heap/Handle.h

/*
 * Copyright (C) 2014 Google 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:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * 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.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "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 THE COPYRIGHT
 * OWNER 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.
 */

#ifndef Handle_h
#define Handle_h

#include "wtf/HashFunctions.h"
#include "wtf/PassOwnPtr.h"
#include "wtf/RawPtr.h"
#include "wtf/RefCounted.h"
#include "wtf/TypeTraits.h"
#include "wtf/text/AtomicString.h"

// Classes that contain heap references but aren't themselves heap
// allocated, have some extra macros available which allows their use
// to be restricted to cases where the garbage collector is able
// to discover their heap references.
//
// STACK_ALLOCATED(): Use if the object is only stack allocated. Heap objects
// should be in Members but you do not need the trace method as they are on
// the stack. (Down the line these might turn in to raw pointers, but for
// now Members indicates that we have thought about them and explicitly
// taken care of them.)
//
// DISALLOW_ALLOCATION(): Cannot be allocated with new operators but can
// be a part object. If it has Members you need a trace method and the
// containing object needs to call that trace method.
//
// ALLOW_ONLY_INLINE_ALLOCATION(): Allows only placement new operator.
// This disallows general allocation of this object but allows to put
// the object as a value object in collections. If these have Members you
// need to have a trace method. That trace method will be called
// automatically by the Heap collections.
//
#define DISALLOW_ALLOCATION()                                   \
    private:                                                    \
        void* operator new(size_t) = delete;                    \
        void* operator new(size_t, NotNullTag, void*) = delete; \
        void* operator new(size_t, void*) = delete;

#define ALLOW_ONLY_INLINE_ALLOCATION()                                              \
    public:                                                                         \
        void* operator new(size_t, NotNullTag, void* location) { return location; } \
        void* operator new(size_t, void* location) { return location; }             \
    private:                                                                        \
        void* operator new(size_t) = delete;

#define STATIC_ONLY(Type) \
    private:              \
        Type() = delete;

// These macros insert annotations that the Blink GC plugin for clang uses for
// verification. STACK_ALLOCATED is used to declare that objects of this type
// are always stack allocated. GC_PLUGIN_IGNORE is used to make the plugin
// ignore a particular class or field when checking for proper usage. When using
// GC_PLUGIN_IGNORE a bug-number should be provided as an argument where the
// bug describes what needs to happen to remove the GC_PLUGIN_IGNORE again.
#if COMPILER(CLANG)
#define STACK_ALLOCATED()                                       \
    private:                                                    \
        __attribute__((annotate("blink_stack_allocated")))      \
        void* operator new(size_t) = delete;                    \
        void* operator new(size_t, NotNullTag, void*) = delete; \
        void* operator new(size_t, void*) = delete;

#else
#define STACK_ALLOCATED() DISALLOW_ALLOCATION()
#endif

namespace blink {

class Visitor {
public:
    template<typename T>
    void mark(T* t)
    {
    }
    template<typename T>
    void trace(const T* t)
    {
    }
    template<typename T>
    void trace(T* t)
    {
    }
    template<typename T>
    void trace(const T& t)
    {
    }
};

#define WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(TYPE)

template<typename T>
class DummyBase {
public:
    DummyBase() { }
    ~DummyBase() { }
};

#define WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED WTF_MAKE_FAST_ALLOCATED
#define DECLARE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(type) \
    public:                                            \
        ~type();                                       \
    private:
#define DECLARE_EMPTY_VIRTUAL_DESTRUCTOR_WILL_BE_REMOVED(type) \
    public:                                                    \
        virtual ~type();                                       \
    private:

#define DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(type) \
    type::~type() { }

#define DEFINE_STATIC_REF_WILL_BE_PERSISTENT(type, name, arguments) \
    DEFINE_STATIC_REF(type, name, arguments)

} // namespace blink

#endif