Exceptional C++ Style 40 New Engineering Puzzles, Programming Problems, and Solutions

Chapter 14. Order, Order!

Difficulty: 2

Programmers learning C++ often come up with interesting misconceptions of what can and can't be done in C++. In this example, contributed by Jan Christiaan van Winkel, a student makes a basic mistake—but one that many compilers let pass with no warnings at all.

JG Question

1. The following code was actually written by a student taking a C++ course, and the compiler the student was using issued no warnings about it. Indeed, several popular compilers issue no warnings for this code. What's wrong with it, and why?

   #include <string>
   using namespace std;
   
   class A {
   public:
    A(const string& s) { /* … */ } string f() { return "hello, world"; } }; class B : public A { public: B() : A(s = f()) {} private: string s; }; int ...