module.h

Overview

module.h is a header-only library contains an implementation of simple module system for C programming language. This is quite experimental library. So, use at your own risks.

Usage

Creating a module

A module should consist of a pair of a header file and .c source file. Here is an example below:

greet.h

#pragma once
#include <module.h>

/* module declaration.
 * `module(name)` is a macro function which generates struct definition and more.
 */
module (greet)
{
  /* function should be declared as a function pointer. */
  void (*hello) (const char *); 
};

greet.c

#include <stdio.h>
#include "greet.h"

/* module members should be static. */
static void
hello (const char *name)
{
  printf ("Hello, %s\n", name);
}

/* you should define a function to initialize module menmbers. 
 * `constructor` is a macro defined in `module.h`.
 */
constructor
__init_greet (void)
{
  greet.hello = hello;
}

You can use this greet module as follows.

#include "greet.h"

int
main (int argc, char *argv[])
{
  greet.hello ("Kojiro");
  return 0;
}

How it works

module (foo) { ... }; is expanded as follows:

constructor __init_foo (void);
struct module_foo foo;
struct module_foo { ... };

constructor is expanded to __attribute__((constructor)) void. So, the function __init_foo is hooked to main function and it initializes the struct foo. It can be said that each modules are singletons.

You can also create sub-modules like this:

module (foo)
{
  struct
    {
      void (*baz) (void); 
    } bar;
}

The constructor should be:

constructor
__init_foo (void)
{
  foo.bar.baz = baz;
}

Limitations

All the functions or the variables belonging to a module are actualy members of a struct named same as the module. So, macros and types could not be contained in a module.

module (foo)
{
  int (*bar) (void); /* works */
  double baz;        /* works */
  typedef qux quux;  /* error */
};

Benefits

module.h allows you to avoid a kind of name-conflicting problems. C basically doesn't have namespaces, so, sometimes some kinf of prefix or suffix rules are taken, for example, fprintf for files and printf for stdout.
module.h can avoid this old manner. Please refer examples/io.

License

moule.h is distributed under MIT License.

Author

TANI Kojiro (kojiro0531@gmail.com)