C++: Add tests.

Author: geoffw0

cpp/ql/test/query-tests/Likely Bugs/Memory Management/ImproperNullTermination/ImproperNullTermination.expected

@@ -27,3 +27,4 @@
 | test.cpp:454:18:454:23 | buffer | Variable $@ may not be null terminated. | test.cpp:452:8:452:13 | buffer | buffer |
 | test.cpp:513:10:513:15 | buffer | Variable $@ may not be null terminated. | test.cpp:511:8:511:13 | buffer | buffer |
 | test.cpp:519:16:519:21 | buffer | Variable $@ may not be null terminated. | test.cpp:517:8:517:13 | buffer | buffer |
+| test.cpp:558:10:558:16 | buffer2 | Variable $@ may not be null terminated. | test.cpp:553:8:553:14 | buffer2 | buffer2 |

cpp/ql/test/query-tests/Likely Bugs/Memory Management/ImproperNullTermination/test.cpp

@@ -536,3 +536,51 @@ void test_printf(char *str)
 	}
 }
 
+void test_reassignment()
+{
+	{
+		char buffer1[1024];
+		char buffer2[1024];
+		char *buffer_ptr = buffer1;
+
+		buffer_ptr = buffer2;
+		strcpy(buffer_ptr, "content"); // null terminates buffer2
+		strdup(buffer2); // GOOD
+	}
+
+	{
+		char buffer1[1024];
+		char buffer2[1024];
+		char *buffer_ptr = buffer1;
+
+		strcpy(buffer_ptr, "content"); // null terminates buffer1
+		buffer_ptr = buffer2;
+		strdup(buffer2); // BAD
+	}
+
+	{
+		char buffer1[1024];
+		char buffer2[1024];
+		char *buffer_ptr = buffer1;
+
+		while (cond())
+		{
+			buffer_ptr = buffer2;
+			strcpy(buffer_ptr, "content"); // null terminates buffer2
+			strdup(buffer2); // GOOD
+		}
+	}
+
+	{
+		char buffer1[1024];
+		char buffer2[1024];
+		char *buffer_ptr = buffer1;
+
+		while (cond())
+		{
+			strcpy(buffer_ptr, "content"); // null terminates buffer1 or buffer2
+			buffer_ptr = buffer2;
+			strdup(buffer2); // BAD [NOT DETECTED]
+		}
+	}
+}