Merge pull request #362 from jbj/return-this-noreturn

C++: Fix "Overloaded assignment does not return 'this'" for non-returning functions

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

@@ -112,6 +112,65 @@ private:
   int val;
 };
 
+struct Exception {
+  virtual ~Exception();
+};
+
+class AlwaysThrows {
+public:
+  AlwaysThrows &operator=(int _val) { // GOOD (always throws)
+    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 (always throws)
+    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.
+  }
+};
+
+class Reachability {
+  Reachability &operator=(Reachability &that) { // GOOD
+    int one = 1;
+    if (one)
+      return *this;
+    else
+      return that; // unreachable
+  }
+
+  // helper function that always returns a reference to `*this`.
+  Reachability &returnThisReference() {
+    int one = 1;
+    if (one)
+      return *this;
+    else
+      return staticInstance; // unreachable
+  }
+
+  // helper function that always returns `this`.
+  Reachability *const returnThisPointer() {
+    int one = 1;
+    if (one)
+      return this;
+    else
+      return &staticInstance; // unreachable
+  }
+
+  Reachability &operator=(int _val) { // GOOD
+    return returnThisReference();
+  }
+
+  Reachability &operator=(short _val) { // GOOD
+    return *returnThisPointer();
+  }
+
+  static Reachability staticInstance;
+};
+
 int main() {
   Container c;
   c = c;