What to do if I hate C++ header files?

Question

I was always confused about header files. They are so strange: you include .h file which doesn't include .cpp but .cpp are somehow compiled too.

Recently I joined a team project, and of course, both .h and .cpp are used.
I understand that this is very important, but I can't live with copy-pasting every function declaration in each of multiple classes we have.

How do I handle the 2-file convention efficiently?
Are there any tools to help with that, or automatically change one file that looks like example below to .h and .cpp? (specifically for MS VC++ 2010)

class A
{
...
    Type f(Type a,Type b)
    {
        //implementation here, not in another file!
    }
...
};

Type f(Type a)
{
     //implementation here
}
...

Answer 1

You could use Lzz. It's a command line tool that takes declarations written in a C++ syntax and generates the header and source files.

Answer 2

Writing More Refactoring Friendly C++

In C++ you don't have to use headers at all. You can define the whole object in one file just as you would with C# or Java. C developers will commonly only keep external calls in a header file. All the internal calls would be defined in the .c file. By the same token, you can reserve your C++ .h files for the classes/interfaces (pure virtual abstract classes)/etc. that are intended to be shared outside the DLL. For internal classes/structs/interfaces, etc. you would simply include the .cpp file you need:

#include<myclass.cpp>

This doesn't seem to be the most popular approach, but it is legal C++. It would definitely be a possibility for all your internal code. This allows the internal code and set of classes to change a lot more radically while providing a more stable interface for code outside your library/executable to interact with.

Having your whole class inside one file will make it easier to do what you want. It won't solve the problem of renaming a method and having to search down every place that method is called, but it will make sure you have more intelligable error messages. Nothing worse than having your header declare a method one way, but you implement it differently. Other code that calls the header file will compile properly and you'll get a link exception, while the implementation file will be the one that complains that the method wasn't defined. When you define every method in place (in the actual class declaration), you'll get the same error message no matter what file includes it.

You may also want to look at this question: Good refactoring tools for C++

How C/C++ Resolves Header/Implementation Files

At the base C level (and C++ is built on that foundation), the header files declare the promise of a function/struct/variable which is enough to allow a compiler to create the object file. Similarly C++ header files declare the promise of functions, structs, classes, etc. It is this definition that the compiler uses to reserve space in the stack, etc.

The the .c or .cpp files have the implementation. As the compiler converts each implementation file to an object file, there are hooks to unimplemented concepts (what was declared in the header). The linker ties the hooks to the implementations in other object files and creates a larger binary that includes all the code (shared library or executable).

VS Specific

As to working with those in Visual Studio, there are some wizards that help make things a bit easier. The new class wizard will create your matching pair of header and implementation files. There is even a class browser feature that will allow you declare new methods. It will inject the definition in the header and the implementation stub in the .cpp file. Visual Studio has had those features for more than a decade (as long as I've used them).

Answer 3

Become a Java developer.

If you really must carry on developing in C++, you could try using an IDE. Often they offer some mechanism by which you can add a method to a class, and it automagically places the declaration in the .h file and the definition in the .cpp file.

Answer 4

You could be interested in the makeheaders program from Hwaci (those who do SQLite and Fossil).

Also have a look at how fossil is built to have an idea.

Answer 5

When you write the first lines of a new class, it usually is because you need it in one place only at that time. At a later time, it might be used at more places, but initially it usually isn't.

Many of my classes start at the top of the current .cpp file. When it has stablized enough to use it in multiple places, I cut-paste it to a header. Though often the class disappears as fast as it appeared.

Answer 6

The Header (.h) file describes the interface to the code, because that's the only bit that other code gets to see.

The Source (.cpp) file provides the implementation of the code that nobody else needs to know about.

you include .h file which doesn't include .cpp ...

Correct.

As a consumer of this code, you only need the Header file so that the compiler knows what's available in that code for you to work with. The C++ source code is not used in any way, shape or form at this point (or, at least, it shouldn't be).

... but .cpp are somehow compiled too.

Yes that are, but completely separately.

The .cpp file of a module/library that you are using is compiled into an Object file (.o / .dll) by the Developer of that library. That object file will contain entry points that are the same "shape" as those described in the Header file.

You will need that Object file when you come to link your finished executable, at which point the Linker may grab the contents of the Object file and embed it into your executable (that's for static linking; dynamic linking gets more complicated)
Basically the linker has to "joins the dots" between the entry points that your code expects to be able to call, based on what it saw in the Header file, and what's actually in the library itself.

Answer 7

As a suggestion to help handle C++ header files, is common to use them without file extension or file suffix, such as "GCC" libraries does.

If this is your case, I suggest to use a ".hpp" (or unleast ".hxx") file extension or file suffix.

You may have to configure your compiler, developer enviroment, or Built program.

Answer 8

Become a Swift developer. No header files. Except if you say to yourself “I wish I could see only the things that a user of this file needs”, you tell the IDE to show the interface of the file, with all implementations and with all non-public functions gone. (One better than C++ header files containing inline definitions and private methods).