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https://android.googlesource.com/platform/development/+/donut-release/ndk/docs/OVERVIEW.TXT

https://android.googlesource.com/platform/ndk/+/4e159d95ebf23b5f72bb707b0cb1518ef96b3d03/docs/ANDROID-MK.TXT

https://android.googlesource.com/platform/ndk/+/4e159d95ebf23b5f72bb707b0cb1518ef96b3d03/docs/APPLICATION-MK.TXT

http://hualang.iteye.com/blog/1149359

http://blog.csdn.net/smfwuxiao/article/details/8523479

1. Android NDK Overview
3. Introduction:
5. The Android NDK is a set of tools that allows Android application developers
6. to embed native machine code compiled from C and/or C++ source files into
7. their application packages.
9. IMPORTANT:
10. The Android NDK can only be used to target Android system images
11. running Cupcake (a.k.a 1.5) or later versions of the platform.
13. 1.0 and 1.1 system images are specifically *not* supported due to
14. subtle ABI and toolchain changes that happened for the 1.5 release.
17. I. Android NDK Goals:
18. ---------------------
20. The Android VM allows your application‘s source code to call methods
21. implemented in native code through the JNI. In a nutshell, this means that:
23. - Your application‘s source code will declare one or more methods
24. with the ‘native‘ keyword to indicate that they are implemented through
25. native code. E.g.:
27. native byte[] loadFile(String filePath);
29. - You must provide a native shared library that contains the
30. implementation of these methods, which will be packaged into your
31. application‘s .apk. This library must be named according to standard
32. Unix conventions as lib<something>.so, and shall contain a standard JNI
33. entry point (more on this later). For example:
35. libFileLoader.so
37. - Your application must explicitely load the library. For example, to load
38. it at application startup, simply add the following to its source code:
40. static {
41. System.loadLibrary("FileLoader");
42. }
44. Note that you should not use the ‘lib‘ prefix and ‘.so‘ suffix here.
47. The Android NDK is a complement to the Android SDK that helps you to:
49. - Generate JNI-compatible shared libraries that can run on the Android
50. 1.5 platform (and later) running on ARM CPUs.
52. - Copy the generated shared libraries to a proper location of your
53. application project path, so they will be automatically added to your
54. final (and signed) .apks
56. - In later revisions of the NDK, we intend to provide tools that help
57. debug your native code through a remote gdb connection and as much
58. source/symbol information as possible.
60. Moreover, the Android NDK provides:
62. - A set of cross-toolchains (compilers, linkers, etc..) that can
63. generate native ARM binaries on Linux, OS X and Windows (with Cygwin)
65. - A set of system headers corresponding to the list of stable native APIs
66. supported by the Android platform. This corresponds to definitions that
67. are guaranteed to be supported in all later releases of the platform.
69. They are documented in the file docs/STABLE-APIS.TXT
71. IMPORTANT:
72. Keep in mind that most of the native system libraries in Android system
73. images are not frozen and might changed drastically, or even deleted,
74. in later updates and releases of the platform.
76. - A build system that allow developers to only write very short build files
77. to describe which sources need to be compiled, and how. The build system
78. deals with all the hairy toolchain/platform/CPU/ABI specifics. Moreover,
79. later updates of the NDK can add support for more toolchains, platforms,
80. system interfaces without requiring changes in the developer‘s build
81. files (more on this later).
84. II. Android NDK Non-Goals:
85. --------------------------
87. The NDK is *not* a good way to write generic native code that runs on Android
88. devices. In particular, your applications should still be written in the Java
89. programming language, handle Android system events appropriately to avoid the
90. "Application Not Responding" dialog or deal with the Android application
91. life-cycle.
93. Note however that is is possible to write a sophisticated application in
94. native code with a small "application wrapper" used to start/stop it
95. appropriately.
97. A good understanding of JNI is highly recommended, since many operations
98. in this environment require specific actions from the developers, that are
99. not necessarily common in typical native code. These include:
101. - Not being able to directly access the content of VM objects through
102. direct native pointers. E.g. you cannot safely get a pointer to a
103. String object‘s 16-bit char array to iterate over it in a loop.
105. - Requiring explicit reference management when the native code wants to
106. keep handles to VM objects between JNI calls.
109. The NDK only provides system headers for a very limited set of native
110. APIs and libraries supported by the Android platform. While a typical
111. Android system image includes many native shared libraries, these should
112. be considered an implementation detail that might change drastically between
113. updates and releases of the platform.
115. If an Android system library is not explicitely supported by the NDK
116. headers, then applications should not depend on it being available, or
117. they risk breaking after the next over-the-air system update on various
118. devices.
120. Selected system libraries will gradually be added to the set of stable NDK
121. APIs.
124. III. NDK development in practice:
125. ---------------------------------
127. Here‘s a very rough overview of how you can develop native code with the
128. Android NDK:
130. 1/ Run build/host-setup.sh to configure the NDK
132. 2/ Place your native sources under $PROJECT/jni/...
134. 3/ Write $PROJECT/jni/Android.mk to describe your sources
135. to the NDK build system
137. 4/ Write apps/<myapp>/Application.mk to describe your application
138. and the native sources it needs to the NDK build system
140. 5/ Build your native code by running "make APP=<myapp>"
141. in the top-level NDK directory.
143. The last step will copy, in case of success, the stripped shared libraries
144. your application needs to your application‘s root project directory. You
145. will then need to generate your final .apk through the usual means.
147. Now, for a few more details:
150. III.1/ Configuring the NDK:
151. - - - - - - - - - - - - - -
153. After installing the NDK as described in docs/INSTALL.TXT, you should call
154. the ‘build/host-setup.sh‘ script to configure your NDK.
156. This script is used to probe your host system and verify a few pre-requisites.
157. It will then generate a configuration file (e.g. out/host/config-host.mk) that
158. is later used during NDK builds.
160. In some cases, this might instruct you to download an archive containing
161. prebuilt toolchain binaries for your development platform, the unzip it
162. to the NDK root directory. The message should contain enough information
163. to let you do that.
165. If you forget this step, trying to build with the NDK will generate an
166. error message telling you what to do.
169. III.2/ Placing C and C++ sources:
170. - - - - - - - - - - - - - - - - -
172. You should place your native sources under the following directory:
174. $PROJECT/jni/
176. Where $PROJECT corresponds to the path of your Android application
177. project.
179. You are pretty free to organize the content of ‘jni‘ as you want,
180. the directory names and structure here will not influence the final
181. generated application packages, so you don‘t have to use pseudo-unique
182. names like com.<mycompany>.<myproject> as is the case for application
183. package names.
185. Note that C and C++ sources are supported. The default C++ file extensions
186. supported by the NDK is ‘.cpp‘, but other extensions can be handled as well
187. (see docs/ANDROID-MK.TXT for details).
189. It is possible to store your sources in a different location by adjusting
190. your Android.mk file (see below).
193. III.3/ Writing an Android.mk build script:
194. - - - - - - - - - - - - - - - - - - - - - -
196. An Android.mk file is a small build script that you write to describe your
197. sources to the NDK build system. Its syntax is described in details in
198. the file docs/ANDROID-MK.TXT.
200. In a nutshell, the NDK groups your sources into "modules", where each module
201. can be one of the following:
203. - a static library
204. - a shared library
206. You can define several modules in a single Android.mk, or you can write
207. several Android.mk files, each one defining a single module.
209. Note that a single Android.mk might be parsed several times by the build
210. system so don‘t assume that certain variables are not defined in them.
211. By default, the NDK will look for the following build script:
213. $PROJECT/jni/Android.mk
215. If you want to define Android.mk files in sub-directories, you should
216. include them explicitely in your top-level Android.mk. There is even
217. a helper function to do that, i.e. use:
219. include $(call all-subdir-makefiles)
221. This will include all Android.mk files in sub-directories of the current
222. build file‘s path.
225. III.4/ Writing an Application.mk build file:
226. - - - - - - - - - - - - - - - - - - - - - - -
228. While an Android.mk file describes your modules to the build system, you
229. need to write an Application.mk file to describe your application and the
230. modules it requires. This file must be located in:
232. $NDK/apps/<myapp>/Application.mk
234. Where <myapp> is a short descriptive name for your application that will
235. be used to invoke the NDK build (and not go into final APKs). The file is
236. used to provide the following to the NDK build:
238. - The location of your Android application‘s project path
240. - The list of NDK modules that is required by your application.
241. This should really be a list of ‘shared library‘ modules.
243. - Optional information, like whether you want a release or debug
244. build, specific C or C++ compiler flags and others.
246. - Planned: the list of specific platforms/CPUs you want to explicitely
247. target (currently only one is supported).
249. The syntax of an Application.mk file is very simple and is described in
250. docs/APPLICATION-MK.TXT
252. You can define several Application.mk corresponding to different builds
253. of the same application, for example:
255. $NDK/apps/release/Application.mk
256. $NDK/apps/debug/Application.mk
259. III.5/ Invoke the NDK build system:
260. - - - - - - - - - - - - - - - - - -
262. On the command-line, go to the top-level NDK directory, then invoke the
263. build system with:
265. make APP=<myapp>
267. Where ‘make‘ refers to GNU Make, and <myapp> is the name of one of the
268. subdirectories of ‘$NDK/apps/‘
270. This will try to build all modules with relevant options, the final
271. shared libraries listed by your Application.mk and, in case of success,
272. will copy stripped versions of the shared libraries to your application‘s
273. project path. (Note that unstripped versions are kept for debugging
274. purposes, there is no need to copy unstripped binaries to a device).
278. IV. Debugging support:
279. - - - - - - - - - - - -
281. Debugging your native code with this initial release of the NDK is still
282. very rough.
284. Note that we plan to make this much easier in a later NDK release, all of
285. this without changing your sources, Android.mk and Application.mk files.
287. =========================
289. 1. Android.mk file syntax specification
     3. Introduction:
     4. -------------
     6. This document describes the syntax of Android.mk build file
     7. written to describe your C and C++ source files to the Android
     8. NDK. To understand what follows, it is assumed that you have
     9. read the docs/OVERVIEW.TXT file that explains their role and
     10. usage.
     12. Overview:
     13. ---------
     15. An Android.mk file is written to describe your sources to the
     16. build system. More specifically:
     18. - The file is really a tiny GNU Makefile fragment that will be
     19. parsed one or more times by the build system. As such, you
     20. should try to minimize the variables you declare there and
     21. do not assume that anything is not defined during parsing.
     23. - The file syntax is designed to allow you to group your
     24. sources into ‘modules‘. A module is one of the following:
     26. - a static library
     27. - a shared library
     29. Only shared libraries will be installed/copied to your
     30. application package. Static libraries can be used to generate
     31. shared libraries though.
     33. You can define one or more modules in each Android.mk file,
     34. and you can use the same source file in several modules.
     36. - The build system handles many details for you. For example, you
     37. don‘t need to list header files or explicit dependencies between
     38. generated files in your Android.mk. The NDK build system will
     39. compute these automatically for you.
     41. This also means that, when updating to newer releases of the NDK,
     42. you should be able to benefit from new toolchain/platform support
     43. without having to touch your Android.mk files.
     45. Note that the syntax is *very* close to the one used in Android.mk files
     46. distributed with the full open-source Android platform sources. While
     47. the build system implementation that uses them is different, this is
     48. an intentional design decision made to allow reuse of ‘external‘ libraries‘
     49. source code easier for application developers.
     51. Simple example:
     52. ---------------
     54. Before describing the syntax in details, let‘s consider a simple
     55. "hello world" example, i.e. the following files:
     57. sources/helloworld/helloworld.c
     58. sources/helloworld/Android.mk
     60. Where ‘helloworld.c‘ is the source of a simple JNI shared library
     61. that implements a native method that returns the "hello world"
     62. string.
     64. The corresponding Android.mk file will look like this:
     66. ---------- cut here ------------------
     67. LOCAL_PATH := $(call my-dir)
     69. include $(CLEAR_VARS)
     71. LOCAL_MODULE := helloworld
     72. LOCAL_SRC_FILES := helloworld.c
     74. include $(BUILD_SHARED_LIBRARY)
     75. ---------- cut here ------------------
     77. Now, let‘s explain these lines:
     79. LOCAL_PATH := $(call my-dir)
     81. An Android.mk file must begin with the definition of the LOCAL_PATH variable.
     82. It is used to locate source files in the development tree. In this example,
     83. the macro function ‘my-dir‘, provided by the build system, is used to return
     84. the path of the current directory (i.e. the directory containing the
     85. Android.mk file itself).
     87. include $(CLEAR_VARS)
     89. The CLEAR_VARS variable is provided by the build system and points to a
     90. special GNU Makefile that will clear many LOCAL_XXX variables for you
     91. (e.g. LOCAL_MODULE, LOCAL_SRC_FILES, LOCAL_STATIC_LIBRARIES, etc...),
     92. with the exception of LOCAL_PATH. This is needed because all build
     93. control files are parsed in a single GNU Make execution context where
     94. all variables are global.
     96. LOCAL_MODULE := helloworld
     98. The LOCAL_MODULE variable must be defined to identify each module you
     99. describe in your Android.mk. The name must be *unique* and not contain
     100. any spaces. Note that the build system will automatically add proper
     101. prefix and suffix to the corresponding generated file. In other words,
     102. a shared library module named ‘foo‘ will generate ‘libfoo.so‘.
     104. IMPORTANT NOTE:
     105. If you name your module ‘libfoo‘, the build system will not
     106. add another ‘lib‘ prefix and will generate libfoo.so as well.
     107. This is to support Android.mk files that originate from the
     108. Android platform sources, would you need to use these.
     110. LOCAL_SRC_FILES := helloworld.c
     112. The LOCAL_SRC_FILES variables must contain a list of C and/or C++ source
     113. files that will be built and assemble into a module. Note that you should
     114. not list header and included files here, because the build system will
     115. compute dependencies automatically for you; just list the source files
     116. that will be passed directly to a compiler, and you should be good.
     118. Note that the default extension for C++ source files is ‘.cpp‘. It is
     119. however possible to specify a different one by defining the variable
     120. LOCAL_DEFAULT_CPP_EXTENSION. Don‘t forget the initial dot (i.e. ‘.cxx‘
     121. will work, but not ‘cxx‘).
     123. include $(BUILD_SHARED_LIBRARY)
     125. The BUILD_SHARED_LIBRARY is a variable provided by the build system that
     126. points to a GNU Makefile script that is in charge of collecting all the
     127. information you defined in LOCAL_XXX variables since the latest
     128. ‘include $(CLEAR_VARS)‘ and determine what to build, and how to do it
     129. exactly. There is also BUILD_STATIC_LIBRARY to generate a static library.
     131. There are more complex examples under sources/samples, with commented
     132. Android.mk files that you can look at.
     134. Reference:
     135. ----------
     137. This is the list of variables you should either rely on or define in
     138. an Android.mk. You can define other variables for your own usage, but
     139. the NDK build system reserves the following variable names:
     141. - names that begin with LOCAL_ (e.g. LOCAL_MODULE)
     142. - names that begin with PRIVATE_, NDK_ or APP_ (used internally)
     143. - lower-case names (used internally, e.g. ‘my-dir‘)
     145. If you need to define your own convenience variables in an Android.mk
     146. file, we recommend using the MY_ prefix, for a trivial example:
     148. ---------- cut here ------------------
     149. MY_SOURCES := foo.c
     150. ifneq ($(MY_CONFIG_BAR),)
     151. MY_SOURCES += bar.c
     152. endif
     154. LOCAL_SRC_FILES += $(MY_SOURCES)
     155. ---------- cut here ------------------
     157. So, here we go:
     160. NDK-provided variables:
     161. - - - - - - - - - - - -
     163. These GNU Make variables are defined by the build system before
     164. your Android.mk file is parsed. Note that under certain circumstances
     165. the NDK might parse your Android.mk several times, each with different
     166. definition for some of these variables.
     168. CLEAR_VARS
     169. Points to a build script that undefines nearly all LOCAL_XXX variables
     170. listed in the "Module-description" section below. You must include
     171. the script before starting a new module, e.g.:
     173. include $(CLEAR_VARS)
     175. BUILD_SHARED_LIBRARY
     176. Points to a build script that collects all the information about the
     177. module you provided in LOCAL_XXX variables and determines how to build
     178. a target shared library from the sources you listed. Note that you
     179. must have LOCAL_MODULE and LOCAL_SRC_FILES defined, at a minimum before
     180. including this file. Example usage:
     182. include $(BUILD_SHARED_LIBRARY)
     184. note that this will generate a file named lib$(LOCAL_MODULE).so
     186. BUILD_STATIC_LIBRARY
     187. A variant of BUILD_SHARED_LIBRARY that is used to build a target static
     188. library instead. Static libraries are not copied into your
     189. project/packages but can be used to build shared libraries (see
     190. LOCAL_STATIC_LIBRARIES and LOCAL_STATIC_WHOLE_LIBRARIES described below).
     191. Example usage:
     193. include $(BUILD_STATIC_LIBRARY)
     195. Note that this will generate a file named lib$(LOCAL_MODULE).a
     197. TARGET_ARCH
     198. Name of the target CPU architecture as it is specified by the
     199. full Android open-source build. This is ‘arm‘ for any ARM-compatible
     200. build, independent of the CPU architecture revision.
     202. TARGET_PLATFORM
     203. Name of the target Android platform when this Android.mk is parsed.
     204. For now, only ‘android-1.5‘ is supported.
     206. TARGET_ARCH_ABI
     207. Name of the target CPU+ABI when this Android.mk is parsed.
     208. For now, only ‘arm‘ is supported, which really means the following:
     210. ARMv5TE or higher CPU, with ‘softfloat‘ floating point support
     212. Other target ABIs will be introduced in future releases of the NDK
     213. and will have a different name. Note that all ARM-based ABIs will
     214. have ‘TARGET_ARCH‘ defined to ‘arm‘, but may have different
     215. ‘TARGET_ARCH_ABI‘
     217. TARGET_ABI
     218. The concatenation of target platform and abi, it really is defined
     219. as $(TARGET_PLATFORM)-$(TARGET_ARCH_ABI) and is useful when you want
     220. to test against a specific target system image for a real device.
     222. By default, this will be ‘android-1.5-arm‘
     225. NDK-provided function macros:
     226. - - - - - - - - - - - - - - -
     228. The following are GNU Make ‘function‘ macros, and must be evaluated
     229. by using ‘$(call <function>)‘. They return textual information.
     231. my-dir
     232. Returns the path of the current Android.mk‘s directory, relative
     233. to the top of the NDK build system. This is useful to define
     234. LOCAL_PATH at the start of your Android.mk as with:
     236. LOCAL_PATH := $(call my-dir)
     238. all-subdir-makefiles
     239. Returns a list of Android.mk located in all sub-directories of
     240. the current ‘my-dir‘ path. For example, consider the following
     241. hierarchy:
     243. sources/foo/Android.mk
     244. sources/foo/lib1/Android.mk
     245. sources/foo/lib2/Android.mk
     247. If sources/foo/Android.mk contains the single line:
     249. include $(call all-subdir-makefiles)
     251. Then it will include automatically sources/foo/lib1/Android.mk and
     252. sources/foo/lib2/Android.mk
     254. This function can be used to provide deep-nested source directory
     255. hierarchies to the build system. Note that by default, the NDK
     256. will only look for files in sources/*/Android.mk
     258. this-makefile
     259. Returns the path of the current Makefile (i.e. where the function
     260. is called).
     262. parent-makefile
     263. Returns the path of the parent Makefile in the inclusion tree,
     264. i.e. the path of the Makefile that included the current one.
     266. grand-parent-makefile
     267. Guess what...
     270. Module-description variables:
     271. - - - - - - - - - - - - - - -
     273. The following variables are used to describe your module to the build
     274. system. You should define some of them between an ‘include $(CLEAR_VARS)‘
     275. and an ‘include $(BUILD_XXXXX)‘. As written previously, $(CLEAR_VARS) is
     276. a script that will undefine/clear all of these variables, unless explicitely
     277. noted in their description.
     279. LOCAL_PATH
     280. This variable is used to give the path of the current file.
     281. You MUST define it at the start of your Android.mk, which can
     282. be done with:
     284. LOCAL_PATH := $(call my-dir)
     286. This variable is *not* cleared by $(CLEAR_VARS) so only one
     287. definition per Android.mk is needed (in case you define several
     288. modules in a single file).
     290. LOCAL_MODULE
     291. This is the name of your module. It must be unique among all
     292. module names, and shall not contain any space. You MUST define
     293. it before including any $(BUILD_XXXX) script.
     295. The module name determines the name of generated files, e.g.
     296. lib<foo>.so for a shared library module named <foo>. However
     297. you should only refer to other modules with their ‘normal‘
     298. name (e.g. <foo>) in your NDK build files (either Android.mk
     299. or Application.mk)
     301. LOCAL_SRC_FILES
     302. This is a list of source files that will be built for your module.
     303. Only list the files that will be passed to a compiler, since the
     304. build system automatically computes dependencies for you.
     306. Note that source files names are all relative to LOCAL_PATH and
     307. you can use path components, e.g.:
     309. LOCAL_SRC_FILES := foo.c \
     310. toto/bar.c
     312. NOTE: Always use Unix-style forward slashes (/) in build files.
     313. Windows-style back-slashes will not be handled properly.
     315. LOCAL_CPP_EXTENSION
     316. This is an optional variable that can be defined to indicate
     317. the file extension of C++ source files. The default is ‘.cpp‘
     318. but you can change it. For example:
     320. LOCAL_CPP_EXTENSION := .cxx
     322. LOCAL_CFLAGS
     323. An optional set of compiler flags that will be passed when building
     324. C source files (*not* C++ sources).
     326. This can be useful to specify an additionnal include path
     327. (relative to the top of the NDK directory), macro definitions
     328. or compile options.
     330. IMPORTANT: Try not to change the optimization/debugging level in
     331. your Android.mk, this can be handled automatically for
     332. you by specifying the appropriate information in
     333. your Application.mk, and will let the NDK generate
     334. useful data files used during debugging.
     336. LOCAL_CXXFLAGS
     337. Same as LOCAL_CFLAGS for C++ source files
     339. LOCAL_CPPFLAGS
     340. Same as LOCAL_CFLAGS but used for both C and C++ source files
     342. LOCAL_STATIC_LIBRARIES
     343. The list of static libraries modules (built with BUILD_STATIC_LIBRARY)
     344. that should be linked to this module. This only makes sense in
     345. shared library modules.
     347. LOCAL_SHARED_LIBRARIES
     348. The list of shared libraries *modules* this module depends on at runtime.
     349. This is necessary at link time and to embed the corresponding information
     350. in the generated file.
     352. Note that this does not append the listed modules to the build graph,
     353. i.e. you should still add them to your application‘s required modules
     354. in your Application.mk
     356. ===================
290. 1. Application.mk file syntax specification
     3. Introduction:
     4. -------------
     6. This document describes the syntax of Application.mk build files
     7. written to describe the native modules required by your Android
     8. application. To understand what follows, it is assumed that you have
     9. read the docs/OVERVIEW.TXT file that explains their role and
     10. usage.
     12. Readers of this document should have read docs/OVERVIEW.TXT and
     13. docs/ANDROID-MK.TXT
     16. Overview:
     17. ---------
     19. The purpose of Application.mk is to describe which native
     20. ‘modules‘ (i.e. static/shared libraries) are needed by your
     21. application.
     23. Each Application.mk must be placed under a sub-directory of
     24. the top-level apps directory, e.g.:
     26. $NDK/apps/<myapp>/Application.mk
     28. Where <myapp> is a short name used to describe your ‘application‘
     29. to the NDK build system (this name doesn‘t go into your generated
     30. shared libraries or your final packages).
     32. The Application.mk is really a tiny GNU Makefile fragment that must
     33. define a few variables:
     35. APP_MODULES
     36. This variable is mandatory and lists all the native modules
     37. (described through Android.mk files) that your application
     38. requires.
     40. This must be a space-separated list of module names as they
     41. appear in the LOCAL_MODULE definitions of Android.mk files
     43. APP_PROJECT_PATH
     44. This variable is mandatory and should give the *absolute*
     45. path to your Application‘s project root directory. This is used
     46. to copy/install stripped versions of the generated JNI shared
     47. libraries to a specific location known to the APK-generating tools.
     49. APP_OPTIM
     50. This optional variable can be defined to either ‘release‘ or
     51. ‘debug‘. This is used to alter the optimization level when
     52. building your application‘s modules.
     54. A ‘release‘ mode is the default, and will generate highly
     55. optimized binaries. The ‘debug‘ mode will generate un-optimized
     56. binaries which are much easier to debug.
     58. Note that it is possible to debug both ‘release‘ and ‘debug‘
     59. binaries, but the ‘release‘ builds tend to provide less information
     60. during debugging sessions: some variables are optimized out and
     61. can‘t be inspected, code re-ordering can make stepping through
     62. the code difficult, stack traces may not be reliable, etc...
     64. APP_CFLAGS
     65. A set of C compiler flags passed when compiling any C source code
     66. of any of the modules. This can be used to change the build of a given
     67. module depending on the application that needs it, instead of modifying
     68. the Android.mk file itself.
     70. IMPORTANT WARNING: +++++++++++++++++++++++++++++++++++++++++++++++++++
     71. +
     72. + All paths in these flags should be relative to the top-level NDK
     73. + directory. For example, if you have the following setup:
     74. +
     75. + sources/foo/Android.mk
     76. + sources/bar/Android.mk
     77. +
     78. + To specify in foo/Android.mk that you want to add the path to the
     79. + ‘bar‘ sources during compilation, you should use:
     80. +
     81. + APP_CFLAGS += -Isources/bar
     82. +
     83. + Or alternatively:
     84. +
     85. + APP_CFLAGS += -I$(LOCAL_PATH)/../bar
     86. +
     87. + Using ‘-I../bar‘ will *NOT* work since it will be equivalent to
     88. + ‘-I$NDK_ROOT/../bar‘ instead.
     89. +
     90. +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
     92. APP_CXXFLAGS
     93. Same as APP_CFLAGS for C++ sources.
     95. APP_CPPFLAGS
     96. Same as APP_CFLAGS but will be passed to both C and C++ sources
     98. A trivial Application.mk file would be:
     100. -------------- cut here -------------------------
     101. APP_MODULES := <list of modules>
     102. APP_PROJECT_PATH := <path to project>
     103. -------------- cut here -------------------------

     104. ============================

     105. Application.mk文件
          
          简介：
          -----------------------------
          要将C\C++代码编译为SO文件，光有Android.mk文件还不行，还需要一个Application.mk文件。
          本文档是描述你的Android应用程序中需要的本地模块的Application.mk的语法使用，要明白如下。
          
          Application.mk目的是描述在你的应用程序中所需要的模块(即静态库或动态库)。
          
          Application.mk文件通常被放置在$PROJECT/jni/Application.mk下，$PROJECT指的是您的项目。
          
          另一种方法是将其放在顶层的子目录下：
          $NDK/apps目录下，例如：
          $NDK/apps/<myapp>/Application.mk
          
          <myapp>是一个简称，用于描述你的NDK编译系统的应用程序（这个名字不会生成共享库或者最终的包）
          
          下面是Application.mk中定义的几个变量。
          
          APP_PROJECT_PATH
          这个变量是强制性的，并且会给出应用程序工程的根目录的一个绝对路径。这是用来复制或者安装一个没有任何版本限制的JNI库，从而给APK生成工具一个详细的路径。
          
          APP_MODULES
          这个变量是可选的，如果没有定义，NDK将由在Android.mk中声明的默认的模块编译，并且包含所有的子文件（makefile文件）
          如果APP_MODULES定义了，它不许是一个空格分隔的模块列表，这个模块名字被定义在Android.mk文件中的LOCAL_MODULE中。注意NDK会自动计算模块的依赖
          
          注意：NDK在R4开始改变了这个变量的行为，再次之前：
           - 在您的Application.mk中，该变量是强制的
           - 必须明确列出所有需要的模块
          
          APP_OPTIM
          这个变量是可选的，用来定义“release”或"debug"。在编译您的应用程序模块的时候，可以用来改变优先级。
          
          “release”模式是默认的，并且会生成高度优化的二进制代码。"debug"模式生成的是未优化的二进制代码，但可以检测出很多的BUG，可以用于调试。
          
          注意：如果你的应用程序是可调试的（即，如果你的清单文件中设置了android:debuggable的属性是"true"）。默认的是"debug"而不是"release"。这可以通过设置APP_OPTIM为"release"来将其覆盖。
          
          注意：可以在"release"和"debug"模式下一起调试，但是"release"模式编译后将会提供更少的BUG信息。在我们清楚BUG的过程 中，有一些变量被优化了，或者根本就无法被检测出来，代码的重新排序会让这些带阿弥变得更加难以阅读，并且让这些轨迹更加不可靠。
          
          APP_CFLAGS
          当编译模块中有任何C文件或者C++文件的时候，C编译器的信号就会被发出。这里可以在你的应用中需要这些模块时，进行编译的调整，这样就不许要直接更改Android.mk为文件本身了
          
          重要警告：+++++++++++++++++++++++++++++++++++++++++++++++ + +
          +
          + 在这些编制中，所有的路径都需要于最顶层的NDK目录相对应。
          + 例如，如果您有以下设置：
          +
          +sources/foo/Android.mk
          +sources/bar/ Android.mk
          + 编译过程中，若要在foo/Android.mk中指定你要添加的路径到bar源代码中，
          + 你应该使用
          + APP_CFLAGS += -Isources/bar
          + 或者交替：
          + APP_CFLAGS += -I $（LOCAL_PATH )/../bar
          +
          + 使用‘-l../bar/‘将不会工作，以为它将等同于"-l$NDK_ROOT/../bar"
          ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++
          注意：在Android的NDK 1.5_r1，只适用于C源文件，而不适合C++。
          这已得到纠正，以建立完整相匹配的Andr??oid系统。
          
          APP_CXXFLAGS
          APP_CPPFLAGS的别名，已经考虑在将在未来的版本中废除了
          
          APP_CPPFLAGS
          当编译的只有C++源文件的时候，可以通过这个C++编译器来设置
          
          注意：在Android NDK-1.5_r1中，这个标志可以应用于C和C++源文件中。并且得到了纠正，以建立完整的与系统相匹配的Android编译系统。你先可也可以使用APP_CFLAGS来应用于C或者C++源文件中。
          建议使用APP_CFLAGS
          
          APP_BUILD_SCRIPT
          默认情况下，NDK编译系统会在$(APP_PROJECT_PATH)/jni目录下寻找名为Android.mk文件：
          $(APP_PROJECT_PATH)/jni/Android.mk
          
          如果你想覆盖此行为，你可以定义APP_BUILD_SCRIPT来指定一个备用的编译脚本。一个非绝对路径总是被解释为相对于NDK的顶层的目录。
          
          APP_ABI
          默认情况下，NDK的编译系统回味"armeabi"ABI生成机器代码。喜爱哪个相当于一个基于CPU可以进行浮点运算的ARMv5TE。你可以使用APP_ABI来选择一个不同的ABI。
          
          比如：为了在ARMv7的设备上支持硬件FPU指令。可以使用
          APP_ABI := armeabi-v7a
          
          或者为了支持IA-32指令集，可以使用
          APP_ABI := x86
          
          或者为了同时支持这三种，可以使用
          APP_ABI := armeabi armeabi-v7a x86
          
          APP_STL
          默认情况下，NDK的编译系统为最小的C++运行时库（/system/lib/libstdc++.so）提供C++头文件。
          然而，NDK的C++的实现，可以让你使用或着链接在自己的应用程序中。
          例如：
          APP_STL := stlport_static    --> static STLport library
          APP_STL := stlport_shared    --> shared STLport library
          APP_STL := system            --> default C++ runtime library
          
          下面是一个Application.mk文件的示例：
          APP_PROJECT_PATH := <path to project>

     108. =================================

     109. NDK提供的共享库（Prebuilt）

     110. Android NDK r5 开始支持预编译库（动态库和静态库），即程序能使用库的预编译版本。

          该特性可用于以下两方面：

          1）向第三方NDK开发人员发布你的共享库而不用提供源码。
          2）使用一个提前编译好的库（预编译库）来加速编译过程。
          

          本文说明该特性如何工作。

          I. 声明一个预编译库的模块

          对于Android编译工具而言，每个预编译库必须声明为一个独立的模块。这里举一个例子，假设 libfoo.so 文件与 Android.mk 位于同一个目录：
          
          [plain] view plaincopy

          1. LOCAL_PATH := $(call my-dir)  
          2. include $(CLEAR_VARS)  
          3. LOCAL_MODULE := foo-prebuilt  
          4. LOCAL_SRC_FILES := libfoo.so  
          5. include $(PREBUILT_SHARED_LIBRARY)  
          按以下步骤声明这样一个模块：
          1. 给该模块取一个名字（这里是 foo-prebuilt）。这个名字不需要与预编译库自身的名字相同。
          2. 将 LOCAL_SRC_FILES 指定为你要提供的共享库的路径。通常，该路径是相对于 LOCAL_PATH 的路径。注意：必须保证共享库ABI的兼容性。
          3. 如果你的库是共享库，则包含 PREBUILT_SHARED_LIBRARY 而不是 BUILD_SHARED_LIBRARY；如果是静态库，则包含 PREBUILT_STATIC_LIBRARY。
          

          预编译模块不需要编译。该预编译模块会被拷贝到 $PROJECT/obj/local 下面，还会被拷贝到 $PROJECT/libs/<abi> 下面（这里的库被strip过）。

          II. 在其他模块中引用这个预编译库

          在依赖该预编译库的模块对应的Android.mk中，将预编译库的名字（前面取的）加入到 LOCAL_STATIC_LIBRARIES 或 LOCAL_SHARED_LIBRARIES 声明中。例如，一个使用上面libfoo.so的简单例子如下：
          

          [plain] view plaincopy

          1. include $(CLEAR_VARS)  
          2. LOCAL_MODULE := foo-user  
          3. LOCAL_SRC_FILES := foo-user.c  
          4. LOCAL_SHARED_LIBRARIES := foo-prebuilt  
          5. include $(BUILD_SHARED_LIBRARY)  

          III. 将预编译库的头文件导出
          

          得到预编译库之后，一般需要它对应的头文件。例如前面的libfoo.so，它有对应的foo.h。编译依赖libfoo.so的模块时，需要将该 头文件和它的路径提供给NDK编译系统。一种简单方法是，前面在定义该预编译库的时候，使用LOCAL_EXPORT_C_INCLUDES 变量。例如，假设文件 foo.h 位于当前预编译模块所在目录的 include 子目录，则可以在预编译模块的Android.mk文件中编写如下：

          [plain] view plaincopy

          1. include $(CLEAR_VARS)  
          2. LOCAL_MODULE := foo-prebuilt  
          3. LOCAL_SRC_FILES := libfoo.so  
          4. LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include  
          5. include $(PREBUILT_SHARED_LIBRARY)  
          这个 LOCAL_EXPORT_C_INCLUDES 定义确保了任何依赖这个预编译库的模块会自动在自己的 LOCAL_C_INCLUDES 变量中增加到这个预编译库的include目录的路径，从而能够找到其中的头文件。

          IV. 调试预编译库

          建议你在预编译库中保留调试信息。位于 $PROJECT/libs/<abi> 的版本都是不含调试信息的（被NDK编译系统执行strip过的），调试版的库才能用于 ndk-gdb。

          V. 共享库ABI的选择

          如前所述，共享库与目标系统的ABI兼容性至关重要。应检查一下 TARGET_ARCH_ABI 的值，可以是以下值：
          armeabi        目标系统CPU是ARMv5TE或更高
          armeabi-v7a    目标系统CPU是ARMv7或更高
          x86            目标系统CPU是x86
          注意，armeabi-v7a的CPU可以很好地执行armeabi的程序。
          举一个例子，我们提供一个预编译库的两个版本，然后选择不同的ABI：
          

          [plain] view plaincopy

          1. include $(CLEAR_VARS)  
          2. LOCAL_MODULE := foo-prebuilt  
          3. LOCAL_SRC_FILES := $(TARGET_ARCH_ABI)/libfoo.so  
          4. LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include  
          5. include $(PREBUILT_SHARED_LIBRARY)  
          这里假设要拷贝的预编译库所在的目录结构如下：
              Android.mk            --> 编译这个预编译库的Android.mk
              armeabi/libfoo.so     --> armeabi版本的共享库
              armeabi-v7a/libfoo.so --> armeabi-v7a版本的共享库
              include/foo.h         --> 预编译库导出的头文件
          注意：你不必提供armeabi-v7a版本，因为armeabi版本的共享库能够被armeabi-v7a的兼容，但是反过来就不行。

Android NDK开发指南---Application.mk文件和android.mk文件

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原文地址：http://www.cnblogs.com/welhzh/p/4537166.html