fixup after review

2 files changed, 23 insertions, 11 deletions

diff --git a/vespalib/src/tests/ref_counted/ref_counted_test.cpp b/vespalib/src/tests/ref_counted/ref_counted_test.cpp
index 751d5b7c506..046823a9ebc 100644
--- a/vespalib/src/tests/ref_counted/ref_counted_test.cpp
+++ b/vespalib/src/tests/ref_counted/ref_counted_test.cpp
@@ -183,12 +183,24 @@ TEST(RefCountedTest, copy_ref_counted) {
     }
 }
 
+struct Other : enable_ref_counted {};
+
 TEST(RefCountedTest, compile_errors_when_uncommented) {
     struct Foo {};
     [[maybe_unused]] Foo foo;
+    [[maybe_unused]] ref_counted<Other> other = make_ref_counted<Other>();
     // ref_counted<Foo> empty;
     // auto ref1 = make_ref_counted<Foo>();
     // auto ref2 = ref_counted_from(foo);
+    // ref_counted<Base> base = other;
+}
+
+TEST(RefCountedTest, self_assign) {
+    ref_counted<Leaf> ref = make_ref_counted<Leaf>(10);
+    ref = ref;
+    ref = std::move(ref);
+    EXPECT_EQ(ref->count_refs(), 1);
+    EXPECT_EQ(ref->val, 10);
 }
 
 TEST(RefCountedTest, with_threads) {
diff --git a/vespalib/src/vespa/vespalib/util/ref_counted.h b/vespalib/src/vespa/vespalib/util/ref_counted.h
index 6465a564891..ab0e1c82044 100644
--- a/vespalib/src/vespa/vespalib/util/ref_counted.h
+++ b/vespalib/src/vespa/vespalib/util/ref_counted.h
@@ -52,40 +52,40 @@ private:
     T *_ptr;
     ref_counted(T *ptr) noexcept : _ptr(ptr) {}
     void maybe_subref() noexcept {
-        if (_ptr) {
+        if (_ptr) [[likely]] {
             _ptr->internal_subref();
         }
     }
     static T *maybe_addref(T *ptr) noexcept {
-        if (ptr) {
+        if (ptr) [[likely]] {
             ptr->internal_addref();
         }
         return ptr;
     }
+    void replace_with(T *ptr) noexcept {
+        maybe_subref();
+        _ptr = ptr;
+    }
 public:
     ref_counted() noexcept : _ptr(nullptr) {}
     ref_counted(ref_counted &&rhs) noexcept : _ptr(std::exchange(rhs._ptr, nullptr)) {}
     ref_counted(const ref_counted &rhs) noexcept : _ptr(maybe_addref(rhs._ptr)) {}
     ref_counted &operator=(ref_counted &&rhs) noexcept {
-        maybe_subref();
-        _ptr = std::exchange(rhs._ptr, nullptr);
+        replace_with(std::exchange(rhs._ptr, nullptr));
         return *this;
     }
     ref_counted &operator=(const ref_counted &rhs) noexcept {
-        maybe_subref();
-        _ptr = maybe_addref(rhs._ptr);
+        replace_with(maybe_addref(rhs._ptr));
         return *this;
     }
     template <typename X> ref_counted(ref_counted<X> &&rhs) noexcept : _ptr(std::exchange(rhs._ptr, nullptr)) {}
     template <typename X> ref_counted(const ref_counted<X> &rhs) noexcept : _ptr(maybe_addref(rhs._ptr)) {}
     template <typename X> ref_counted &operator=(ref_counted<X> &&rhs) noexcept {
-        maybe_subref();
-        _ptr = std::exchange(rhs._ptr, nullptr);
+        replace_with(std::exchange(rhs._ptr, nullptr));
         return *this;
     }
     template <typename X> ref_counted &operator=(const ref_counted<X> &rhs) noexcept {
-        maybe_subref();
-        _ptr = maybe_addref(rhs._ptr);
+        replace_with(maybe_addref(rhs._ptr));
         return *this;
     }
     T *operator->() const noexcept { return _ptr; }
@@ -109,7 +109,7 @@ ref_counted<T> make_ref_counted(Args && ... args) {
 // create a new handle to a reference counted object
 // (NB: object must still be valid)
 template <typename T>
-ref_counted<T> ref_counted_from(T &t) {
+ref_counted<T> ref_counted_from(T &t) noexcept {
     t.internal_addref();
     return ref_counted<T>::internal_attach(std::addressof(t));
 }