Bug 953296 - Implement mozilla::MakeUnique. r=jcranmer

--HG--
extra : rebase_source : 6e25d80e697f1b00e1525f6b11221f4ed9cf965e

mfbt/UniquePtr.h

@@ -569,6 +569,99 @@ operator!=(NullptrT n, const UniquePtr<T, D>& x)
 
 // No operator<, operator>, operator<=, operator>= for now because simplicity.
 
+namespace detail {
+
+template<typename T>
+struct UniqueSelector
+{
+    typedef UniquePtr<T> SingleObject;
+};
+
+template<typename T>
+struct UniqueSelector<T[]>
+{
+    typedef UniquePtr<T[]> UnknownBound;
+};
+
+template<typename T, decltype(sizeof(int)) N>
+struct UniqueSelector<T[N]>
+{
+    typedef UniquePtr<T[N]> KnownBound;
+};
+
+} // namespace detail
+
+// We don't have variadic template support everywhere, so just hard-code arities
+// 0-4 for now.  If you need more arguments, feel free to add the extra
+// overloads.
+//
+// Beware!  Due to lack of true nullptr support in gcc 4.4 and 4.5, passing
+// literal nullptr to MakeUnique will not work on some platforms.  See Move.h
+// for more details.
+
+template<typename T>
+typename detail::UniqueSelector<T>::SingleObject
+MakeUnique()
+{
+  return UniquePtr<T>(new T());
+}
+
+template<typename T, typename A1>
+typename detail::UniqueSelector<T>::SingleObject
+MakeUnique(A1&& a1)
+{
+  return UniquePtr<T>(new T(Forward<A1>(a1)));
+}
+
+template<typename T, typename A1, typename A2>
+typename detail::UniqueSelector<T>::SingleObject
+MakeUnique(A1&& a1, A2&& a2)
+{
+  return UniquePtr<T>(new T(Forward<A1>(a1), Forward<A2>(a2)));
+}
+
+template<typename T, typename A1, typename A2, typename A3>
+typename detail::UniqueSelector<T>::SingleObject
+MakeUnique(A1&& a1, A2&& a2, A3&& a3)
+{
+  return UniquePtr<T>(new T(Forward<A1>(a1), Forward<A2>(a2), Forward<A3>(a3)));
+}
+
+template<typename T, typename A1, typename A2, typename A3, typename A4>
+typename detail::UniqueSelector<T>::SingleObject
+MakeUnique(A1&& a1, A2&& a2, A3&& a3, A4&& a4)
+{
+  return UniquePtr<T>(new T(Forward<A1>(a1), Forward<A2>(a2), Forward<A3>(a3), Forward<A4>(a4)));
+}
+
+template<typename T>
+typename detail::UniqueSelector<T>::UnknownBound
+MakeUnique(decltype(sizeof(int)) n)
+{
+  typedef typename RemoveExtent<T>::Type ArrayType;
+  return UniquePtr<T>(new ArrayType[n]());
+}
+
+template<typename T>
+typename detail::UniqueSelector<T>::KnownBound
+MakeUnique() MOZ_DELETE;
+
+template<typename T, typename A1>
+typename detail::UniqueSelector<T>::KnownBound
+MakeUnique(A1&& a1) MOZ_DELETE;
+
+template<typename T, typename A1, typename A2>
+typename detail::UniqueSelector<T>::KnownBound
+MakeUnique(A1&& a1, A2&& a2) MOZ_DELETE;
+
+template<typename T, typename A1, typename A2, typename A3>
+typename detail::UniqueSelector<T>::KnownBound
+MakeUnique(A1&& a1, A2&& a2, A3&& a3) MOZ_DELETE;
+
+template<typename T, typename A1, typename A2, typename A3, typename A4>
+typename detail::UniqueSelector<T>::KnownBound
+MakeUnique(A1&& a1, A2&& a2, A3&& a3, A4&& a4) MOZ_DELETE;
+
 } // namespace mozilla
 
 #endif /* mozilla_UniquePtr_h */

mfbt/tests/TestUniquePtr.cpp

@@ -16,6 +16,7 @@
 using mozilla::DefaultDelete;
 using mozilla::IsNullPointer;
 using mozilla::IsSame;
+using mozilla::MakeUnique;
 using mozilla::Swap;
 using mozilla::UniquePtr;
 using mozilla::Vector;
@@ -543,6 +544,48 @@ TestArray()
   return true;
 }
 
+struct Q
+{
+    Q() {}
+    Q(const Q& q) {}
+
+    Q(Q& q, char c) {}
+
+    template<typename T>
+    Q(Q q, T&& t, int i)
+    {}
+
+    Q(int i, long j, double k, void* l) {}
+};
+
+static int randomInt() { return 4; }
+
+static bool
+TestMakeUnique()
+{
+  UniquePtr<int> a1(MakeUnique<int>());
+  UniquePtr<long> a2(MakeUnique<long>(4));
+
+  // no args, easy
+  UniquePtr<Q> q0(MakeUnique<Q>());
+
+  // temporary bound to const lval ref
+  UniquePtr<Q> q1(MakeUnique<Q>(Q()));
+
+  // passing through a non-const lval ref
+  UniquePtr<Q> q2(MakeUnique<Q>(*q1, 'c'));
+
+  // pass by copying, forward a temporary, pass by value
+  UniquePtr<Q> q3(MakeUnique<Q>(Q(), UniquePtr<int>(), randomInt()));
+
+  // various type mismatching to test "fuzzy" forwarding
+  UniquePtr<Q> q4(MakeUnique<Q>('s', 66LL, 3.141592654, &q3));
+
+  UniquePtr<char[]> c1(MakeUnique<char[]>(5));
+
+  return true;
+}
+
 int
 main()
 {
@@ -558,4 +601,6 @@ main()
     return 1;
   if (!TestArray())
     return 1;
+  if (!TestMakeUnique())
+    return 1;
 }