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Asked: 2026-05-16T09:03:40+00:00

In my header, I have a prototype declaration like this: void move(int, int); I

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In my header, I have a prototype declaration like this:

void move(int, int);

I can omit the parameter names, that’s how I’m used to it from C. I do that so that I don’t have to keep the parameter names in sync – it’s extremely confusing if they differ between prototype and implementation.

Right now, I’m documenting all of my code with Doxygen, and I decided to put all comments into the header. Now I have to refer to parameter names that are defined in the implementation but not in the header: I find that confusing.

/**
 * Moves the entity to the specified point.
 * @param x The x coordinate of the new position.
 * @param y The y coordinate of the new position.
 */
void move(int, int);

In the generated Doxygen HTML, it is not easy to figure out which parameter is which. Of course, one could follow the same order here, but if one has many parameters, it is still confusing.

The alternative would be to duplicate parameter names and try to keep them in sync. However, some people don’t encourage this approach, saying that header parameters should start with a double underscore so that the user of a method can not possibly use the same name (names starting with __ are disallowed in C++).

How do you do it?

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1 Answer

  1. Editorial Team

    Surely if "names starting with __ are disallowed in C++", you shouldn’t be using them in prototypes either 🙂 *a

    I see two ways to do it.

    One, you can ensure that the order of parameters in your comments always matches the order in your prototype.

    Or, two, you could actually put the real names in your prototypes as well.

    Myself, I prefer the second approach since I like to be able to tell what parameters are passed in, even if the function has no comments on it (or worse, the comments get out of date). This is far easier with a prototype like:

    void move(int xcoord, int ycoord);

    than it is with:

    void move(int, int);

    In some environments, we’ve even gone so far as to have the build process ensure that all function prototypes have identically named parameters as the function definition.

    *a) These identifiers are actually not for the use of regular programs. Section 17.6.3.3.2 of cpp0x (but this restriction has been around for quite a while in both C and C++) states:

    Certain sets of names and function signatures are always reserved to the implementation:

    • Each name that contains a double underscore __ or begins with an underscore followed by an uppercase letter is reserved to the implementation for any use.
    • Each name that begins with an underscore is reserved to the implementation for use as a name in the global namespace.

    In other words, don’t use them for your own purposes.

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