CPP: Add a test of placement new for AV Rule 79.ql.

Author: geoffw0

cpp/ql/test/query-tests/jsf/4.10 Classes/AV Rule 79/AV Rule 79.expected

@@ -11,5 +11,8 @@
 | ExternalOwners.cpp:49:3:49:20 | ... = ... | Resource a is acquired by class MyScreen but not released anywhere in this class. |
 | ListDelete.cpp:21:3:21:21 | ... = ... | Resource first is acquired by class MyThingColection but not released anywhere in this class. |
 | NoDestructor.cpp:23:3:23:20 | ... = ... | Resource n is acquired by class MyClass5 but not released anywhere in this class. |
+| PlacementNew.cpp:36:3:36:36 | ... = ... | Resource p1 is acquired by class MyTestForPlacementNew but not released anywhere in this class. |
+| PlacementNew.cpp:37:3:37:51 | ... = ... | Resource p2 is acquired by class MyTestForPlacementNew but not released anywhere in this class. |
+| PlacementNew.cpp:38:3:38:49 | ... = ... | Resource p3 is acquired by class MyTestForPlacementNew but not released anywhere in this class. |
 | SelfRegistering.cpp:25:3:25:24 | ... = ... | Resource side is acquired by class MyOwner but not released anywhere in this class. |
 | Variants.cpp:23:3:23:13 | ... = ... | Resource f is acquired by class MyClass4 but not released anywhere in this class. |

cpp/ql/test/query-tests/jsf/4.10 Classes/AV Rule 79/PlacementNew.cpp

@@ -0,0 +1,47 @@
+
+typedef unsigned long size_t;
+
+namespace std
+{
+	using ::size_t;
+	struct nothrow_t {};
+	extern const nothrow_t nothrow;
+}
+
+// nothrow new
+void* operator new(std::size_t size, const std::nothrow_t&) throw();
+
+// placement new
+void* operator new (std::size_t size, void* ptr) throw();
+
+// ---
+
+class MyClassForPlacementNew
+{
+public:
+	MyClassForPlacementNew(int _v) : v(_v) {}
+	~MyClassForPlacementNew() {}
+
+private:
+	int v;
+};
+
+class MyTestForPlacementNew
+{
+public:
+	MyTestForPlacementNew()
+	{
+		void *buffer_ptr = buffer;
+
+		p1 = new MyClassForPlacementNew(1); // BAD: not released
+		p2 = new (std::nothrow) MyClassForPlacementNew(2); // BAD: not released
+		p3 = new (buffer_ptr) MyClassForPlacementNew(3); // GOOD: placement new, not an allocation [FALSE POSITIVE]
+	}
+
+	~MyTestForPlacementNew()
+	{
+	}
+
+	MyClassForPlacementNew *p1, *p2, *p3;
+	char buffer[sizeof(MyClassForPlacementNew)];
+};