C++: Use interpolation to avoid a bad join order.

Author: MathiasVP

cpp/ql/src/Critical/GlobalUseBeforeInit.ql

@@ -110,6 +110,5 @@ from GlobalVariable v, Function f
 where
   uninitialisedBefore(v, f) and
   useFunc(v, f)
-select f,
-  "The variable '" + v.getName() + "'" +
-    " is used in this function but may not be initialized when it is called."
+select f, "The variable $@ is used in this function but may not be initialized when it is called.",
+  v, v.getName()

cpp/ql/test/query-tests/Critical/GlobalUseBeforeInit/GlobalUseBeforeInit.expected

@@ -1 +1 @@
-| test.cpp:27:5:27:6 | f1 | The variable 'b' is used in this function but may not be initialized when it is called. |
+| test.cpp:27:5:27:6 | f1 | The variable $@ is used in this function but may not be initialized when it is called. | test.cpp:14:5:14:5 | b | b |