The Contiki build system
http://contiki.sourceforge.net/docs/2.6/a01796.html
先看官方文档的说明，对contiki的构建系统有个总体的概览。
The Contiki build system ======================== The Contiki build system is designed to make it easy to compile Contiki applications for different hardware platforms or into a simulation platform by simply supplying different parameters to the make command, without having to edit makefiles or modify the application code. The file example project in examples/hello-world/ shows how the Contiki build system works. The hello-world.c application can be built into a complete Contiki system by running make in the examples/hello-world/ directory. Running make without parameters will build a Contiki system using the native target. The native target is a special Contiki platform that builds an entire Contiki system as a program that runs on the development system. After compiling the application for the native target it is possible to run the Contiki system with the application by running the file hello-world.native. To compile the application and a Contiki system for the ESB platform the command make TARGET=esb is used. This produces a hello-world.esb file that can be loaded into an ESB board. To compile the hello-world application into a stand-alone executable that can be loaded into a running Contiki system, the command make hello-world.ce is used. To build an executable file for the ESB platform, make TARGET=esb hello-world.ce is run. To avoid having to type TARGET= every time make is run, it is possible to run make TARGET=esb savetarget to save the selected target as the default target platform for subsequent invocations of make. A file called Makefile.target containing the currently saved target is saved in the project's directory. Beside TARGET= there's DEFINES= which allows to set arbitrary variables for the C preprocessor in form of a comma-separated list. Again it is possible to avoid having to re-type i.e. DEFINES=MYTRACE,MYVALUE=4711 by running make TARGET=esb DEFINES=MYTRACE,MYVALUE=4711 savedefines. A file called Makefile.esb.defines is saved in the project's directory containing the currently saved defines for the ESB platform. Makefiles used in the Contiki build system The Contiki build system is composed of a number of Makefiles. These are: * Makefile: the project's makefile, located in the project directory. * Makefile.include: the system-wide Contiki makefile, located in the root of the Contiki source tree. * Makefile.$(TARGET) (where $(TARGET) is the name of the platform that is currently being built): rules for the specific platform, located in the platform's subdirectory in the platform/ directory. * Makefile.$(CPU) (where $(CPU) is the name of the CPU or microcontroller architecture used on the platform for which Contiki is built): rules for the CPU architecture, located in the CPU architecture's subdirectory in the cpu/ directory. * Makefile.$(APP) (where $(APP) is the name of an application in the apps/ directory): rules for applications in the apps/ directories. Each application has its own makefile. The Makefile in the project's directory is intentionally simple. It specifies where the Contiki source code resides in the system and includes the system-wide Makefile, Makefile.include. The project's makefile can also define in the APPS variable a list of applications from the apps/ directory that should be included in the Contiki system. The Makefile used in the hello-world example project looks like this: CONTIKI_PROJECT = hello-world all: $(CONTIKI_PROJECT) CONTIKI = ../.. include $(CONTIKI)/Makefile.include First, the location of the Contiki source code tree is given by defining the CONTIKI variable. Next, the name of the application is defined. Finally, the system-wide Makefile.include is included. The Makefile.include contains definitions of the C files of the core Contiki system. Makefile.include always reside in the root of the Contiki source tree. When make is run, Makefile.include includes the Makefile.$(TARGET) as well as all makefiles for the applications in the APPS list (which is specified by the project's Makefile). Makefile.$(TARGET), which is located in the platform/$(TARGET)/ directory, contains the list of C files that the platform adds to the Contiki system. This list is defined by the CONTIKI_TARGET_SOURCEFILES variable. The Makefile.$(TARGET) also includes the Makefile.$(CPU) from the cpu/$(CPU)/ directory. The Makefile.$(CPU) typically contains definitions for the C compiler used for the particular CPU. If multiple C compilers are used, the Makefile.$(CPU) can either contain a conditional expression that allows different C compilers to be defined, or it can be completely overridden by the platform specific makefile Makefile.$(TARGET).
总结如下： (注：以hello-world为例子)
1. Contiki 的构建系统使编译Contiki应用程序很简单，只需要给make命令提供不同的参数，就可以把Contiki应用程序编译成不同平台的不同应用程序的可执行文件，而不用去修改makefiles或者应用程序代码。
2. make 默认会编译成本机（native target)可执行文件，编译完的文件（如hello-world.native)可运行在我们的开发环境上。
3. 指定平台，可以在make命令增加TARGET参数，如指定平台esb，将会生成hello-world.esb文件
make TARGET=esb
4. 编译成Contiki运行时可加载的文件，则需要执行以下命令
make TARGET=esb hello-world.ce
5. 为了避免每次执行make命令都要输入TARGET变量，可运行如下命令
make TARGET=esb savetarget
将TARGET= esb 保存在Makefile.target文件中，作为默认的TARGET.
6. 除了TARGET参数，还有DEFINES参数，可为c预处理设定任意的变量
make TARGET=esb DEFINES=MYTRACE,MYVALUE=4711 savedefines
同样可将DEFINES保存在Makefile.esb.defines中，作为默认的DEFINES。其中esb是平台名称。
7. Makefiles 文件种类
Makefile： 工程Makefile，可理解为总控Makefile
Makefile.include: 在Contiki根目录下, the systme-wide Contiki makefile
Makefile.$(TARGET): 在平台目录下，及platform/$(TARGET)，rules for the specific platform
Makefile.$(CPU): $(CPU)是cpu的名字，在cpu/$(CPU)目录下，rules for the CPU architecture
Makefile.$(APP）: $(APP）是应用名称，在apps/$(APP）目录下，rules for applications
8. APPS 变量
APPS变量定义apps/目录下那些应用程序需要被Contiki 操作系统包含。
Makefile.include会根据APPS包含进所有apps/目录下相关的makefiles。
9. 工程Makefile
CONTIKI_PROJECT = hello-world
all: $(CONTIKI_PROJECT)
CONTIKI = ../..
include $(CONTIKI)/Makefile.include
工程Makefile一般都比较简单，定义Contiki 源代码的根目录位置，用变量CONTIKI存储。
包含Makefile.include文件。
也还可以定义APPS变量，包含所需的应用。
10. Makefile.include
The Makefile.include contains definitions of the C files of the core Contiki system. Makefile.include always reside in the root of the Contiki source tree. When make is run, Makefile.include includes the Makefile.$(TARGET) as well as all makefiles for the applications in the APPS list (which is specified by the project's Makefile).
11. Makefile.$(TARGET)
Makefile.$(TARGET), which is located in the platform/$(TARGET)/ directory, contains the list of C files that the platform adds to the Contiki system. This list is defined by the CONTIKI_TARGET_SOURCEFILES variable. The Makefile.$(TARGET) also includes the Makefile.$(CPU) from the cpu/$(CPU)/ directory.
12. Makefile.$(CPU)
The Makefile.$(CPU) typically contains definitions for the C compiler used for the particular CPU. If multiple C compilers are used, the Makefile.$(CPU) can either contain a conditional expression that allows different C compilers to be defined, or it can be completely overridden by the platform specific makefile Makefile.$(TARGET).