In C++, what do you do nearly all the time?

Question

There are a few things that I almost always do when I put a class together in C++.

1) Virtual Destructor 2) Copy constructor and assignment operator (I either implement them in terms of a private function called Copy(), or declare them private and thus explicitly disallow the compiler to auto generate them).

What things do you find are almost always useful?

Answer 1

Oddly, most of the suggestions here are things I specifically don't do.

• I don't make dtors virtual unless I am designing it specifically to be inherited. It adds a lot of overhead and prevents automatic inlining, which is bad since most dtors are empty anyways (and few classes benefit from inheritance)
• I don't make copy ctor/assignment op unless the defaults won't work -- and if it won't, I may want to reconsider the design. Remember, between string & vector, there's hardly ever a reason to call new anymore. And creating your own copy ctor identical to the default one will almost certainly be less efficient.
• I don't add string cast. It causes too many problems where the cast is called silently where you didn't intend it to be. Better to add a ToString() method.
• I don't add a friend oper<<, because friends are evil and messy. Better to add a Display(ostream) method. Then the oper<< can call that, and doesn't need to be a friend. In fact, you could make the oper<< a template function calling Display() and never have to worry about it again.

Answer 2

I find turning on the gcc flags -Wall, -Werror, and (this is the fun one) -Weffc++ help catch a lot of potential problems. From the gcc man page:

  -Weffc++ (C++ only)
      Warn about violations of the following style guidelines from Scott
      Meyers’ Effective C++ book:

      ·   Item 11:  Define a copy constructor and an assignment operator
          for classes with dynamically allocated memory.

      ·   Item 12:  Prefer initialization to assignment in constructors.

      ·   Item 14:  Make destructors virtual in base classes.

      ·   Item 15:  Have "operator=" return a reference to *this.

      ·   Item 23:  Don’t try to return a reference when you must return
          an object.

      and about violations of the following style guidelines from Scott
      Meyers’ More Effective C++ book:

      ·   Item 6:  Distinguish between prefix and postfix forms of incre-
          ment and decrement operators.

      ·   Item 7:  Never overload "&&", "││", or ",".

      If you use this option, you should be aware that the standard
      library headers do not obey all of these guidelines; you can use
      grep -v to filter out those warnings.

Answer 3

The first i do when putting a class together is putting some doxygen comment above it about why it exists and what it does.

I once worked on a group project where they said they want to document the stuff at the end of the project. And it was all of a mess to put the comments into the code later on. I don't want to have this happen again.

Answer 4

Adding a semicolon after the class definition. This continuously bites me in the ass every time I forget to do it since gcc's error messages are vague and it generally says something like "can't define a type in the return type of a function" which doesn't mean a whole lot...