The C++ Shoot-yourself-in-the-Foot of the Week

I think we can all agree that C++, compared to other languages, provides quite a number of possibilities to screw up. Everybody working with the language at some point probably had problems with e.g. its exception system, operator overloading or automatic type conversions – to name just a few of the darker corners.

There are also many mitigation strategies which all come down to ban certain aspects of the language and/or define strict code conventions. If you follow Google’s style guide, for example, you cannot use exceptions and you are restricted to a very small set of boost libs.

But developers – being humans – often find creative and surprising ways to thwart every good intentions. In an external project the following conventions are in place:

  • Use const wherever you possibly can
  • Use boost::shared_ptr wherever it makes sense.
  • Define typedefs to shared_ptrs  in order to make code more readable.
  • typedefs to shared_ptrs are to be defined like this:
typedef boost::shared_ptr<MySuperDuperClass> MySuperDuperClassPtr;
  • typedefs to shared const pointers are to be defined like this:
typedef boost::shared_ptr<const MySuperDuperClass> MySuperDuperClassCPtr;

As you can see, postfixes Ptr and CPtr are the markers for normal shared_ptrs and constant shared_ptrs.

Last week, a compile error about some const to non-const conversion made me nearly pull my hair out. The types of variables that were involved all had the CPtr postfix but still the code didn’t compile. After a little digging I found that one of the typedefs involved was like this:

typedef boost::shared_ptr<  MySuperDuperClass> MySuperDuperClassCPtr;

Somebody just deleted the const modifier in front of MySuperDuperClass but left the name with the CPtr untouched. And because non-const to const conversions are allowed this was not detected for a couple of weeks. Nice going!

Any suggestions for a decent style checker for c++? Thanks in advance 😉

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.