garbage-collected.h File Reference

#include <type_traits>
#include "cppgc/internal/api-constants.h"
#include "cppgc/macros.h"
#include "cppgc/platform.h"
#include "cppgc/trace-trait.h"
#include "cppgc/type-traits.h"

Include dependency graph for garbage-collected.h:

This graph shows which files directly or indirectly include this file:

Go to the source code of this file.

Data Structures
class	GarbageCollectedBase
class	GarbageCollected< typename >
class	GarbageCollectedMixin

Namespaces
	cppgc
	cppgc::internal

Macros
#define	USING_GARBAGE_COLLECTED_MIXIN()
#define	MERGE_GARBAGE_COLLECTED_MIXINS()

Macro Definition Documentation

MERGE_GARBAGE_COLLECTED_MIXINS

#define MERGE_GARBAGE_COLLECTED_MIXINS

(

)

Value:

 public:                                                \
  /* When using multiple mixins the methods become  */  \
  /* ambigous. Providing additional implementations */  \
  /* disambiguate them again.                       */  \
  TraceDescriptor GetTraceDescriptor() const override { \
    return {kNotFullyConstructedObject, nullptr};       \
  }                                                     \
                                                        \
 private:                                               \
  friend class internal::__thisIsHereToForceASemicolonAfterThisMacro

Merge two or more Mixins into one.

class A : public GarbageCollectedMixin {};
class B : public GarbageCollectedMixin {};
class C : public A, public B {
  MERGE_GARBAGE_COLLECTED_MIXINS();
 public:
};

Definition at line 178 of file garbage-collected.h.

USING_GARBAGE_COLLECTED_MIXIN

#define USING_GARBAGE_COLLECTED_MIXIN

(

)

Value:

 public:                                                                     \
  /* Marker is used by clang to check for proper usages of the macro. */     \
  typedef int HasUsingGarbageCollectedMixinMacro;                            \
                                                                             \
  TraceDescriptor GetTraceDescriptor() const override {                      \
    static_assert(                                                           \
        internal::IsSubclassOfTemplate<                                      \
            std::remove_const_t<std::remove_pointer_t<decltype(this)>>,      \
            cppgc::GarbageCollected>::value,                                 \
        "Only garbage collected objects can have garbage collected mixins"); \
    return {this, TraceTrait<std::remove_const_t<                            \
                      std::remove_pointer_t<decltype(this)>>>::Trace};       \
  }                                                                          \
                                                                             \
 private:                                                                    \
  friend class internal::__thisIsHereToForceASemicolonAfterThisMacro

Macro defines all methods and markers needed for handling mixins. Must be used on the type that is inheriting from GarbageCollected and GarbageCollectedMixin.

class Mixin : public GarbageCollectedMixin {
 public:
  void Trace(cppgc::Visitor* visitor) const override {
    // Dispatch using visitor->Trace(...);
  }
};
 
class Foo : public GarbageCollected<Foo>, public Mixin {
  USING_GARBAGE_COLLECTED_MIXIN();
 public:
  void Trace(cppgc::Visitor* visitor) const override {
    // Dispatch using visitor->Trace(...);
    Mixin::Trace(visitor);
  }
};

Definition at line 148 of file garbage-collected.h.