C++: FP test for "operator= doesn't return *this"

This rule should not apply to functions that never return.

Author: jbj

cpp/ql/test/query-tests/jsf/4.10 Classes/AV Rule 82/AV Rule 82.cpp

@@ -112,6 +112,28 @@ class Obj2 {
   int val;
 };
 
+struct Exception {
+  virtual ~Exception();
+};
+
+class AlwaysThrows {
+public:
+  AlwaysThrows &operator=(int _val) { // GOOD [FALSE POSITIVE]
+    throw Exception();
+    // No `return` statement is generated by the C++ front end because it can
+    // statically see that the end of the function is unreachable.
+  }
+
+  AlwaysThrows &operator=(int *_val) { // GOOD [FALSE POSITIVE]
+    int one = 1;
+    if (one)
+      throw Exception();
+    // A `return` statement is generated by the C++ front end, but the
+    // control-flow pruning in QL will establish that this is unreachable.
+  }
+};
+
+
 int main() {
   Container c;
   c = c;

cpp/ql/test/query-tests/jsf/4.10 Classes/AV Rule 82/AV Rule 82.expected

@@ -2,3 +2,5 @@
 | AV Rule 82.cpp:24:8:24:16 | operator= | Assignment operator in class Bad2 should have return type Bad2&. Otherwise a copy is created at each call. |
 | AV Rule 82.cpp:63:29:63:37 | operator= | Assignment operator in class TemplateReturnAssignment<T> does not return a reference to *this. |
 | AV Rule 82.cpp:63:29:63:37 | operator= | Assignment operator in class TemplateReturnAssignment<int> does not return a reference to *this. |
+| AV Rule 82.cpp:121:17:121:25 | operator= | Assignment operator in class AlwaysThrows does not return a reference to *this. |
+| AV Rule 82.cpp:127:17:127:25 | operator= | Assignment operator in class AlwaysThrows does not return a reference to *this. |