Question

I just stumbled across this bug in some legacy code:

class MyAPIHandler {     private:      int handle;     public:     void MyApiHandler()  // default constructor     {         handle = 42;     }; }; 

It compiles fine, with no warnings – but the behaviour wasn’t what I intended, because the constructor name is misspelt. This by itself would have produced a warning about ‘function does not return a value’, but I guess I was on autopilot and added a ‘void’ return type to ‘fix’ this.

Now, the bugfix was easy, but my question is this:-

What techniques could I use to prevent this type of bug recurring?

Some languages require an explicit ‘constructor’ keyword, which should make this problem obvious. Unit testing, obviously should also have caught it. What else can I do?

Answer 1

If you always use initialiser lists in your constructors:

MyApiHandler()  // default constructor : handle(42) { } 

the misnamed constructor bug would be even more unlikely, and it’s better style anyway.

Edit: thanks to commenter for the link