Understanding the makefile
A makefile defines how to build a particular application. Makefiles typically include all of the following elements:
Name: Give your build a name (LOCAL_MODULE := ).
Local Variables: Clear local variables with CLEAR_VARS (include $(CLEAR_VARS)).
Files: Determine which files your application depends upon (LOCAL_SRC_FILES := main.c).
Tags: Define tags, as necessary (LOCAL_MODULE_TAGS := eng development).
Libraries: Define whether your application links with other libraries (LOCAL_SHARED_LIBRARIES := cutils).
Template file: Include a template file to define underlining make tools for a particular target (include $(BUILD_EXECUTABLE)).
The following snippet illustrates a typical makefile.
LOCAL_PATH := $(my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE :=
LOCAL_SRC_FILES := main.c
LOCAL_MODULE_TAGS := eng development
LOCAL_SHARED_LIBRARIES := cutils
include $(BUILD_EXECUTABLE)
(HOST_)EXECUTABLE, (HOST_)JAVA_LIBRARY, (HOST_)PREBUILT, (HOST_)SHARED_LIBRARY,
(HOST_)STATIC_LIBRARY, PACKAGE, JAVADOC, RAW_EXECUTABLE, RAW_STATIC_LIBRARY,
COPY_HEADERS, KEY_CHAR_MAP
The snippet above includes artificial line breaks to maintain a print-friendly document.
Layers
The build hierarchy includes the abstraction layers described in the table below.
Each layer relates to the one above it in a one-to-many relationship. For example, an arch can have more than one board and each board can have more than one device. You may define an element in a given layer as a specialization of an element in the same layer, thus eliminating copying and simplifying maintenance.
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