Application.mk file syntax specification

Introduction:
-------------

This document describes the syntax of Application.mk build files
written to describe the native modules required by your Android
application. To understand what follows, it is assumed that you have
read the docs/OVERVIEW.TXT file that explains their role and
usage.

Readers of this document should have read docs/OVERVIEW.TXT and
docs/ANDROID-MK.TXT


Overview:
---------

The purpose of Application.mk is to describe which native
'modules' (i.e. static/shared libraries) are needed by your
application.

An Application.mk file is usually placed under $PROJECT/jni/Application.mk,
where $PROJECT points to your application's project directory.

Another alternative is to place it under a sub-directory of the top-level
$NDK/apps directory, e.g.:

   $NDK/apps/<myapp>/Application.mk

Where <myapp> is a short name used to describe your 'application'
to the NDK build system (this name doesn't go into your generated
shared libraries or your final packages).

The Application.mk is really a tiny GNU Makefile fragment that must
define a few variables:

APP_PROJECT_PATH
    This variable should give the *absolute* path to your
    Application's project root directory. This is used to copy/install
    stripped versions of the generated JNI shared libraries to a
    specific location known to the APK-generating tools.

    Note that it is optional for $PROJECT/jni/Application.mk, but
    *mandatory* for $NDK/apps/<myapp>/Application.mk

APP_MODULES
    This variable is optional. If not defined, the NDK will build by
    default _all_ the modules declared by your Android.mk, and any
    sub-makefile it may include.

    If APP_MODULES is defined, it must be a space-separated list of module
    names as they appear in the LOCAL_MODULE definitions of Android.mk
    files. Note that the NDK will compute module dependencies automatically.

    NOTE: This variable's behaviour changed in NDK r4. Before that:

      - the variable was mandatory in your Application.mk
      - all required modules had to be listed explicitely.

APP_OPTIM
    This optional variable can be defined to either 'release' or
    'debug'. This is used to alter the optimization level when
    building your application's modules.

    A 'release' mode is the default, and will generate highly
    optimized binaries. The 'debug' mode will generate un-optimized
    binaries which are much easier to debug.

    Note that if your application is debuggable (i.e. if your manifest
    sets the android:debuggable attribute to "true" in its <application>
    tag), the default will be 'debug' instead of 'release'. This can
    be overriden by setting APP_OPTIM to 'release'.

    Note that it is possible to debug both 'release' and 'debug'
    binaries, but the 'release' builds tend to provide less information
    during debugging sessions: some variables are optimized out and
    can't be inspected, code re-ordering can make stepping through
    the code difficult, stack traces may not be reliable, etc...

APP_CFLAGS
    A set of C compiler flags passed when compiling any C or C++ source code
    of any of the modules. This can be used to change the build of a given
    module depending on the application that needs it, instead of modifying
    the Android.mk file itself.

    IMPORTANT WARNING: +++++++++++++++++++++++++++++++++++++++++++++++++++
    +
    + All paths in these flags should be relative to the top-level NDK
    + directory. For example, if you have the following setup:
    +
    +    sources/foo/Android.mk
    +    sources/bar/Android.mk
    +
    +  To specify in foo/Android.mk that you want to add the path to the
    + 'bar' sources during compilation, you should use:
    +
    +   APP_CFLAGS += -Isources/bar
    +
    + Or alternatively:
    +
    +   APP_CFLAGS += -I$(LOCAL_PATH)/../bar
    +
    + Using '-I../bar' will *NOT* work since it will be equivalent to
    + '-I$NDK_ROOT/../bar' instead.
    +
    +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

    NOTE: In android-ndk-1.5_r1, this only applied to C sources, not C++ ones.
          This has been corrected to match the full Android build system.

APP_CXXFLAGS
    An alias for APP_CPPFLAGS, to be considered obsolete as it may disappear
    in a future release of the NDK.

APP_CPPFLAGS
    A set of C++ compiler flags passed when building C++ sources *only*.

    NOTE: In android-ndk-1.5_r1, this applied to both C and C++ sources.
          This has been corrected to match the full Android build system.
          You can now use APP_CFLAGS for flags that shall apply to C and
          C++ souces.

APP_BUILD_SCRIPT
    By default, the NDK build system will look for a file named Android.mk
    under $(APP_PROJECT_PATH)/jni, i.e. for the file:

       $(APP_PROJECT_PATH)/jni/Android.mk

    If you want to override this behaviour, you can define APP_BUILD_SCRIPT
    to point to an alternate build script. A non-absolute path will always
    be interpreated as relative to the NDK's top-level directory.

APP_ABI
    By default, the NDK build system will generate machine code for the
    'armeabi' ABI. This corresponds to an ARMv5TE based CPU with software
    floating point operations. You can use APP_ABI to select a different
    ABI.

    For example, to support hardware FPU instructions on ARMv7 based devices,
    use:

        APP_ABI := armeabi-v7a

    Or to support both ARMv5TE and ARMv7 based devices, use:

        APP_ABI := armeabi armeabi-v7a

    For the list of all supported ABIs and details about their usage and
    limitations, please read docs/CPU-ARCH-ABIS.TXT


A trivial Application.mk file would be:

-------------- cut here -------------------------
APP_PROJECT_PATH := <path to project>
-------------- cut here -------------------------
