C++: Demonstrate AmbiguouslySignedBitField FP

Author: jbj

cpp/ql/test/query-tests/Likely Bugs/AmbiguouslySignedBitField/AmbiguouslySignedBitField.expected

@@ -3,3 +3,4 @@
 | test.cpp:20:8:20:18 | nosignshort | Bit field nosignshort of type short should have explicitly unsigned integral, explicitly signed integral, or enumeration type. |
 | test.cpp:21:18:21:30 | nosigntypedef | Bit field nosigntypedef of type int should have explicitly unsigned integral, explicitly signed integral, or enumeration type. |
 | test.cpp:23:15:23:25 | nosignconst | Bit field nosignconst of type const int should have explicitly unsigned integral, explicitly signed integral, or enumeration type. |
+| test.cpp:31:5:31:16 | templatesign | Bit field templatesign of type T should have explicitly unsigned integral, explicitly signed integral, or enumeration type. |

cpp/ql/test/query-tests/Likely Bugs/AmbiguouslySignedBitField/test.cpp

@@ -25,3 +25,10 @@ struct {
     myEnum nosignenum : 2;
     const myEnum constnosignenum : 2;
 };
+
+template<typename T>
+struct TemplateWithBitfield {
+  T templatesign : 2; // GOOD [FALSE POSITIVE]
+};
+
+TemplateWithBitfield<signed int> twb;