diff options
Diffstat (limited to 'src/core/lib/gprpp/ref_counted.h')
-rw-r--r-- | src/core/lib/gprpp/ref_counted.h | 58 |
1 files changed, 52 insertions, 6 deletions
diff --git a/src/core/lib/gprpp/ref_counted.h b/src/core/lib/gprpp/ref_counted.h index 03c293f6ed..81772f3403 100644 --- a/src/core/lib/gprpp/ref_counted.h +++ b/src/core/lib/gprpp/ref_counted.h @@ -34,14 +34,58 @@ namespace grpc_core { +// PolymorphicRefCount enforces polymorphic destruction of RefCounted. +class PolymorphicRefCount { + public: + GRPC_ABSTRACT_BASE_CLASS + + protected: + GPRC_ALLOW_CLASS_TO_USE_NON_PUBLIC_DELETE + + virtual ~PolymorphicRefCount() {} +}; + +// NonPolymorphicRefCount does not enforce polymorphic destruction of +// RefCounted. Please refer to grpc_core::RefCounted for more details, and +// when in doubt use PolymorphicRefCount. +class NonPolymorphicRefCount { + public: + GRPC_ABSTRACT_BASE_CLASS + + protected: + GPRC_ALLOW_CLASS_TO_USE_NON_PUBLIC_DELETE + + ~NonPolymorphicRefCount() {} +}; + // A base class for reference-counted objects. // New objects should be created via New() and start with a refcount of 1. // When the refcount reaches 0, the object will be deleted via Delete(). // // This will commonly be used by CRTP (curiously-recurring template pattern) // e.g., class MyClass : public RefCounted<MyClass> -template <typename Child> -class RefCounted { +// +// Use PolymorphicRefCount and NonPolymorphicRefCount to select between +// different implementations of RefCounted. +// +// Note that NonPolymorphicRefCount does not support polymorphic destruction. +// So, use NonPolymorphicRefCount only when both of the following conditions +// are guaranteed to hold: +// (a) Child is a concrete leaf class in RefCounted<Child>, and +// (b) you are gauranteed to call Unref only on concrete leaf classes and not +// their parents. +// +// The following example is illegal, because calling Unref() will not call +// the dtor of Child. +// +// class Parent : public RefCounted<Parent, NonPolymorphicRefCount> {} +// class Child : public Parent {} +// +// Child* ch; +// ch->Unref(); +// +template <typename Child, typename Impl = PolymorphicRefCount> +class RefCounted : public Impl { public: RefCountedPtr<Child> Ref() GRPC_MUST_USE_RESULT { IncrementRefCount(); @@ -69,7 +113,8 @@ class RefCounted { RefCounted() { gpr_ref_init(&refs_, 1); } - virtual ~RefCounted() {} + // Note: Depending on the Impl used, this dtor can be implicitly virtual. + ~RefCounted() {} private: // Allow RefCountedPtr<> to access IncrementRefCount(). @@ -87,8 +132,8 @@ class RefCounted { // pointers and legacy code that is manually calling Ref() and Unref(). // Once all of our code is converted to idiomatic C++, we may be able to // eliminate this class. -template <typename Child> -class RefCountedWithTracing { +template <typename Child, typename Impl = PolymorphicRefCount> +class RefCountedWithTracing : public Impl { public: RefCountedPtr<Child> Ref() GRPC_MUST_USE_RESULT { IncrementRefCount(); @@ -149,7 +194,8 @@ class RefCountedWithTracing { : RefCountedWithTracing() {} #endif - virtual ~RefCountedWithTracing() {} + // Note: Depending on the Impl used, this dtor can be implicitly virtual. + ~RefCountedWithTracing() {} private: // Allow RefCountedPtr<> to access IncrementRefCount(). |