Add rcp::use_count()

include/rcp.h

@@ -119,6 +119,11 @@ public:
         other.ptr = nullptr;
     }
 
+    int use_count() const
+    {
+        return ptr ? ptr->rcp_count() : 0;
+    }
+
     void swap(rcp & other) noexcept
     {
         T * tmp = ptr;
@@ -232,6 +237,10 @@ rcp<T> rcp_dynamic_cast(rcp<U> && other)
                 delete this; \
             } \
         } \
+        int rcp_count() const \
+        { \
+            return ref_count.load(std::memory_order_relaxed); \
+        } \
     private: \
         mutable std::atomic<int> ref_count{0}; \
     rcp_managed(classname)

tests.cpp

@@ -314,6 +314,20 @@ protected:
     ~Counter() { external_destruct++; }
 };
 
+void test_use_count()
+{
+    MyB a = MyB::create(1, 2);
+    assert(a.use_count() == 1);
+    {
+        MyB b = a;
+        assert(a.use_count() == 2);
+        assert(b.use_count() == 2);
+    }
+    assert(a.use_count() == 1);
+    MyB empty;
+    assert(empty.use_count() == 0);
+}
+
 void test_swap()
 {
     MyB a = MyB::create(1, 2);
@@ -368,6 +382,7 @@ int main(int argc, char * argv[])
     test_dynamic_cast_failure();
     test_dynamic_cast_move_success();
     test_dynamic_cast_move_failure();
+    test_use_count();
     test_swap();
     test_hash();
     test_external_class();