A template with Linux Kernel like build system (Kbuild).

Writing a basic makefile for a small project is fairly simple. But when you maintain a large project, you will probably need more than just basics: automatic dependency tracking, recursive builds in subdirectories, and so on. Instead of implementing those functions by yourself, you can use Autotools (Autoconf/Automake/Libtool). Especially, you are following GNU Coding Standards, Autotools would be a best choice. Otherwise, Kbuild are also quite powerful, recommended build system. Now some open source projects such as busybox, are using Kbuild, although, originally, kbuild system were written for Linux Kernel.

This project includes a pretty simple application with Kbuild system. Some files needed for Kbuild features were copied from Linux Kernel. Copied files include the top-level Makefile and some helper programs and makefiles under scripts/ directory. They were modified for simplisity because modules support are not necessary for general applications.

I hope this template will be a good startpoint of your new project.

    make config    # This creates a file called ".config"
    make           # This creates an executable

These steps generate a small application myapp, which just print some messages to the console.

The full list of configuration and build targets is available by:

    make help

This project includes a small program called myapp just for example. So when you start your own project, replace C source files of myapp with those of your own. C source files of myapp are located under lib/ and main/ and include/. If you don't need them, delete all of them. Although, of course, you can still reuse them for your own project. You will also need to modify Kconfig for your project.

In order to change the name of application, modify the top-level Makefile.

    grep -i myapp *

will show the lines where myapp string are used. Modify those myapp strings with your application name.

You can add more subdirectories by adding to objs-y or libs-y variables of top-level Makefile. For myapp, these variable are set as follows:

    objs-y          := main
    libs-y          := lib

In this case, all objectes under main/ subdirectory are combined together into main/builtin.o, and all objects under lib/ subdirectory are archived as lib/lib.a. Finally, they are linked to generate the final application, myapp.

About the detail of how to write makefiles under subdirectories, refer to: Documentation/kbuild/makefiles.txt.

About how to write Kconfig, refer to: Documentation/kbuild/kconfig-language.txt.

Both of them were copied from Linux Kernel Documentation.