No arguments that depend on a template parameter

Aside

I have a C++ program of moderate complexity that I have to return to every 12-18 months to fix an obscure bug or add a modest festure. And every time, I spent one or two days just trying to get the thing build with the latest compiler, which picks up previously legal code and decides to whine about it, generating dozens of errors.

This is not the fault of the compiler. This is the fault of C++ for being so sloppy and complex. This is why C++ should just die and give way to Java.

The Error

Compiling a templated class that "worked previously" (under gcc3.3. as opposed to 4.x), an error was thrown on a previously acceptable and non-templated member:

/Users/agapow/Desktop/mloc/ComboMill.h:188: error:
there are no arguments to 'SetMemberShip' that depend on
a template parameter, so a declaration of 'SetMemberShip'
must be available

Huh. A simplfied version of the class looks like this:

template class ComboMill {
   // ...
   void SetMembership (bool iIsMember) {
      for (int i = 0; i < mMembership.size(); i++) {
         mMembership[i] = iIsMember;
      }
   }

   void First () {
      // error on next line
      SetMembership (false);
   }
   // ...
};

SetMembership is called by a number of other methods to toggle the state of set members. But that isn't the problem - the problem occurs where other methods go to call SetMembership.

Solution

It's a tough error to google for, but basically C++ is being stricter about how it identifies what you are calling. Where previously a symbol "X" would be implicitly taken to refer to a member or method "X" on the parent class, here C++ is insisting that you make it explicit. Thus it can easily be fixed by writing:

void First () {
   // error on next line
   this->SetMembership (false);
}

One of the criticisms made about Python is that you have to explicitly member access qualify with "self". It seems C++ is also not longer immune form this.

References

• Secction 11.9.2 in C++ misunderstandings