Application.mk file syntax specification

This is a mirror of official Google NDK documentation.

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.html file that explains their role and
usage.

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


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 explicitly.

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 overridden 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++ sources.

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 interpreted 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 the IA-32 instruction set, use:

        APP_ABI := x86

    Or to support all three at the same time, use:

        APP_ABI := armeabi armeabi-v7a x86

    Or even better, since NDK r7, you can also use the special value
    'all' which means "all ABIs supported by this NDK release":

        APP_ABI := all

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

APP_STL
    By default, the NDK build system provides C++ headers for the minimal
    C++ runtime library (/system/lib/libstdc++.so) provided by the Android
    system.

    However, the NDK comes with alternative C++ implementations that you can
    use or link to in your own applications. Define APP_STL to select one of
    them. Examples are:

       APP_STL := stlport_static    --> static STLport library
       APP_STL := stlport_shared    --> shared STLport library
       APP_STL := system            --> default C++ runtime library

    For more information on the subject, please read docs/CPLUSPLUS-SUPPORT.html

APP_GNUSTL_FORCE_CPP_FEATURES
    In prior NDK versions, the simple fact of using the GNU libstdc++
    runtime (i.e. by setting APP_STL to either 'gnustl_static' or
    'gnustl_shared') enforced the support for exceptions and RTTI in all
    generated machine code. This could be problematic in specific, but rare,
    cases, and also generated un-necessarily bigger code for projects that
    don't require these features.

    This bug was fixed in NDK r7b, but this means that if your code requires
    exceptions or RTTI, it should now explicitely say so, either in your
    APP_CPPFLAGS, or your LOCAL_CPPFLAGS / LOCAL_CPP_FEATURES definitions.

    To make it easier to port projects to NDK r7b and later, one can
    optionally defined APP_GNUSTL_CPP_FEATURES to contain one or more of the
    following values:

       exceptions    -> to enforce exceptions support for all modules.
       rtti          -> to enforce rtti support for all modules.

    For example, to get the exact same behaviour than NDK r7:

       APP_GNUSTL_FORCE_CPP_FEATURES := exceptions rtti

    IMPORTANT: This variable is provided here as a convenience to make it
               easier to transition to a newer version of the NDK. It will
               be removed in a future revision. We thus encourage all
               developers to modify the module definitions properly instead
               of relying on it here.

A trivial Application.mk file would be:

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