CPP: Add a test similar to the false positive in arvidn/libtorrent.

Author: geoffw0

cpp/ql/test/query-tests/Critical/NewFree/NewFreeMismatch.expected

@@ -12,3 +12,4 @@
 | test.cpp:235:2:235:5 | call to free | There is a new/free mismatch between this free and the corresponding $@. | test.cpp:227:7:227:13 | new | new |
 | test.cpp:239:2:239:5 | call to free | There is a new/free mismatch between this free and the corresponding $@. | test.cpp:228:7:228:17 | new[] | new[] |
 | test.cpp:272:3:272:6 | call to free | There is a new/free mismatch between this free and the corresponding $@. | test.cpp:265:7:265:13 | new | new |
+| test.cpp:425:2:425:31 | delete | There is a malloc/delete mismatch between this delete and the corresponding $@. | test.cpp:425:20:425:29 | call to getPointer | malloc |

cpp/ql/test/query-tests/Critical/NewFree/test.cpp

@@ -371,3 +371,56 @@ void test12(bool cond)
 		free(z); // GOOD
 	}
 }
+
+// ---
+
+class MyBuffer13
+{
+public:
+	MyBuffer13(int size)
+	{
+		buffer = (char *)malloc(size * sizeof(char));
+	}
+
+	~MyBuffer13()
+	{
+		free(buffer); // GOOD
+	}
+
+	char *getBuffer() // note: this should not be considered an allocation function
+	{
+		return buffer;
+	}
+
+private:
+	char *buffer;
+};
+
+class MyPointer13
+{
+public:
+	MyPointer13(char *_pointer) : pointer(_pointer)
+	{
+	}
+
+	MyPointer13(MyBuffer13 &buffer) : pointer(buffer.getBuffer())
+	{
+	}
+
+	char *getPointer() // note: this should not be considered an allocation function
+	{
+		return pointer;
+	}
+
+private:
+	char *pointer;
+};
+
+void test13()
+{
+	MyBuffer13 myBuffer(100);
+	MyPointer13 myPointer2(myBuffer);
+	MyPointer13 myPointer3(new char[100]);
+
+	delete myPointer2.getPointer(); // GOOD [FALSE POSITIVE]
+}