I’ve tried a lot of the “newer” languages and, somehow, I’m always happiest when I go back to C++ or even C. However, there is one thing that gets a little on my nerves when I go back: the need to have header files with a declaration and then a separate file with almost the same information duplicated. I constantly make a change and forget to update the header, and many other languages take care of that for you. So I went looking for a way to automate things. Sure, some IDEs will automatically insert declarations but I’ve never been very happy with those for a variety of reasons. I wanted something lightweight that I could use in lots of different toolsets.

I found an older tool, however, that does a pretty good job, although there are a few limitations. The tool seems to be a little obscure, so I thought I’d show you what makeheaders — part of the Fossil software configuration management system. The program dates back to 1993 when [Dwayne Richard Hipp] — the same guy that wrote SQLite — created it for his own use. It isn’t very complex — the whole thing lives in one fairly large C source file but it can scan a directory and create header files for everything. In some cases, you won’t need to make big changes to your source code, but if you are willing, there are several things you can do.

The Problem

Suppose you have two C files that cooperate. Let’s say you have A.c and B.c. Inside the A file, you have a simple function:

double ctof(double c)
{
  return (9.0*c)/f+32.0;
}

If you expect to use this inside file B, there needs to be a declaration so that when you compile B, the compiler can know that the function takes a single double argument and returns a double. With ANSI C (and C++) you need something like:

double ctf(double c);

There’s no actual programming, just a note to the compiler about what the function looks like. This is what you call a prototype. Normally, you’ll create a header file with the prototype. You can include that header in both A.c and B.c.

The problem is when you change the function in A.c:

double ctof(double c1, int double c2)
{
  return (9.0*(c1+c2))/f+32.0;
}

If you don’t change the header to match, you’ll have problems. Not only that, but you need to make the same change. If you make a mistake and mark the arguments as floats in the header, that won’t work either.

The Program

Assuming you’ve installed the software, you can simply run it passing all the C and H files you want it to scan. Usually, the glob *.[ch] will do the trick. You can also use it with .cpp files and even a mix. By default, this will pull all the global variable declarations and global functions you define into a series of header files.

Why a series? The program makes an odd assumption that makes sense once you think about it. Since the …read more

Source:: Hackaday