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22 <title>Android Build System</title>
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72<h1><a name="My_Project_" />Android Build System</h1>
73
74<!-- Status is one of: Draft, Current, Needs Update, Obsolete -->
75<p style="text-align:center">
76 <strong>Status:</strong> <em>Draft </em> &nbsp;
77 <small>(as of May 18, 2006)</small>
78</p>
79
80<p><b>Contents</b></p>
81<!-- this div expands out to a list of contents based on the H2 and H3 headings.
82Believe it! -->
83 <div id="nav" class="nav-2-levels"></div>
84
85<h2>Objective</h2>
86<p>The primary goals of reworking the build system are (1) to make dependencies
87work more reliably, so that when files need to rebuilt, they are, and (2) to
88improve performance of the build system so that unnecessary modules are not
89rebuilt, and so doing a top-level build when little or nothing needs to be done
90for a build takes as little time as possible.</p>
91
92<h2>Principles and Use Cases and Policy</h2>
93<p>Given the above objective, these are the overall principles and use cases
94that we will support. This is not an exhaustive list.</p>
95<h3>Multiple Targets</h3>
96<p>It needs to be possible to build the Android platform for multiple targets.
97This means:</p>
98<ul>
99 <li>The build system will support building tools for the host platform,
100 both ones that are used in the build process itself, and developer tools
101 like the simulator.</li>
102 <li>The build system will need to be able to build tools on Linux
103 (definitely Goobuntu and maybe Grhat), MacOS, and to some degree on
104 Windows.</li>
105 <li>The build system will need to be able to build the OS on Linux, and in
106 the short-term, MacOS. Note that this is a conscious decision to stop
107 building the OS on Windows. We are going to rely on the emulator there
108 and not attempt to use the simulator. This is a requirement change now
109 that the emulator story is looking brighter.</li>
110</ul>
111<h3>Non-Recursive Make</h3>
112<p>To achieve the objectives, the build system will be rewritten to use make
113non-recursively. For more background on this, read <a href="http://aegis.sourceforge.net/auug97.pdf">Recursive Make Considered Harmful</a>. For those that don't
114want PDF, here is the
115<a href="http://72.14.203.104/search?q=cache:HwuX7YF2uBIJ:aegis.sourceforge.net/auug97.pdf&hl=en&gl=us&ct=clnk&cd=2&client=firefox">Google translated version</a>.
116<h3>Rapid Compile-Test Cycles</h3>
117<p>When developing a component, for example a C++ shared library, it must be
118possible to easily rebuild just that component, and not have to wait more than a
119couple seconds for dependency checks, and not have to wait for unneeded
120components to be built.</p>
121<h3>Both Environment and Config File Based Settings</h3>
122<p>To set the target, and other options, some people on the team like to have a
123configuration file in a directory so they do not have an environment setup
124script to run, and others want an environment setup script to run so they can
125run builds in different terminals on the same tree, or switch back and forth
126in one terminal. We will support both.</p>
127<h3>Object File Directory / make clean</h3>
128<p>Object files and other intermediate files will be generated into a directory
129that is separate from the source tree. The goal is to have make clean be
130"rm -rf <obj>" in the tree root directory. The primary goals of
131this are to simplify searching the source tree, and to make "make clean" more
132reliable.</p>
133
134<h3>SDK</h3>
135<p>The SDK will be a tarball that will allow non-OS-developers to write apps.
136The apps will actually be built by first building the SDK, and then building
137the apps against that SDK. This will hopefully (1) make writing apps easier
138for us, because we won't have to rebuild the OS as much, and we can use the
139standard java-app development tools, and (2) allow us to dog-food the SDK, to
140help ensure its quality. Cedric has suggested (and I agree) that apps built
141from the SDK should be built with ant. Stay tuned for more details as we
142figure out exactly how this will work.</p>
143
144<h3>Dependecies</h3>
145<p>Dependencies should all be automatic. Unless there is a custom tool involved
146(e.g. the webkit has several), the dependencies for shared and static libraries,
147.c, .cpp, .h, .java, java libraries, etc., should all work without intervention
148in the Android.mk file.</p>
149
150<h3>Hiding command lines</h3>
151<p>The default of the build system will be to hide the command lines being
152executed for make steps. It will be possible to override this by specifying
153the showcommands pseudo-target, and possibly by setting an environment
154variable.</p>
155
156<h3>Wildcard source files</h3>
157<p>Wildcarding source file will be discouraged. It may be useful in some
158scenarios. The default <code>$(wildcard *)</code> will not work due to the
159current directory being set to the root of the build tree.<p>
160
161<h3>Multiple targets in one directory</h3>
162<p>It will be possible to generate more than one target from a given
163subdirectory. For example, libutils generates a shared library for the target
164and a static library for the host.</p>
165
166<h3>Makefile fragments for modules</h3>
167<p><b>Android.mk</b> is the standard name for the makefile fragments that
168control the building of a given module. Only the top directory should
169have a file named "Makefile".</p>
170
171<h3>Use shared libraries</h3>
172<p>Currently, the simulator is not built to use shared libraries. This should
173be fixed, and now is a good time to do it. This implies getting shared
174libraries to work on Mac OS.</p>
175
176
177<h2>Nice to Have</h2>
178
179<p>These things would be nice to have, and this is a good place to record them,
180however these are not promises.</p>
181
182<h3>Simultaneous Builds</h3>
183<p>The hope is to be able to do two builds for different combos in the same
184tree at the same time, but this is a stretch goal, not a requirement.
185Doing two builds in the same tree, not at the same time must work. (update:
186it's looking like we'll get the two builds at the same time working)</p>
187
188<h3>Deleting headers (or other dependecies)</h3>
189<p>Problems can arise if you delete a header file that is referenced in
190".d" files. The easy way to deal with this is "make clean". There
191should be a better way to handle it. (from fadden)</p>
192<p>One way of solving this is introducing a dependency on the directory. The
193problem is that this can create extra dependecies and slow down the build.
194It's a tradeoff.</p>
195
196<h3>Multiple builds</h3>
197<p>General way to perform builds across the set of known platforms. This
198would make it easy to perform multiple platform builds when testing a
199change, and allow a wide-scale "make clean". Right now the buildspec.mk
200or environment variables need to be updated before each build. (from fadden)</p>
201
202<h3>Aftermarket Locales and Carrier</h3>
203<p>We will eventually need to add support for creating locales and carrier
204customizations to the SDK, but that will not be addressed right now.</p>
205
206
207<h2><a id="usage"/>Usage</h2>
208<p>You've read (or scrolled past) all of the motivations for this build system,
209and you want to know how to use it. This is the place.</p>
210
211<h3>Your first build</h3>
212<p>The <a href="../building.html">Building</a> document describes how do do
213builds.</p>
214
215<h3>build/envsetup.sh functions</h3>
216If you source the file build/envsetup.sh into your bash environment,
217<code>. build/envsetup.sh</code>you'll get a few helpful shell functions:
218
219<ul>
220<li><b>printconfig</b> - Prints the current configuration as set by the
221lunch and choosecombo commands.</li>
222<li><b>m</b> - Runs <code>make</code> from the top of the tree. This is
223useful because you can run make from within subdirectories. If you have the
224<code>TOP</code> environment variable set, it uses that. If you don't, it looks
225up the tree from the current directory, trying to find the top of the tree.</li>
226<li><b>croot</b> - <code>cd</code> to the top of the tree.</li>
227<li><b>sgrep</b> - grep for the regex you provide in all .c, .cpp, .h, .java,
228and .xml files below the current directory.</li>
229</ul>
230
231<h3>Build flavors/types</h3>
232<p>
233When building for a particular product, it's often useful to have minor
234variations on what is ultimately the final release build. These are the
235currently-defined "flavors" or "types" (we need to settle on a real name
236for these).
237</p>
238
239<table border=1>
240<tr>
241 <td>
242 <code>eng<code>
243 </td>
244 <td>
245 This is the default flavor. A plain "<code>make</code>" is the
246 same as "<code>make eng</code>". <code>droid</code> is an alias
247 for <code>eng</code>.
248 <ul>
249 <li>Installs modules tagged with: <code>eng</code>, <code>debug</code>,
250 <code>user</code>, and/or <code>development</code>.
251 <li>Installs non-APK modules that have no tags specified.
252 <li>Installs APKs according to the product definition files, in
253 addition to tagged APKs.
254 <li><code>ro.secure=0</code>
255 <li><code>ro.debuggable=1</code>
256 <li><code>ro.kernel.android.checkjni=1</code>
257 <li><code>adb</code> is enabled by default.
258 </td>
259</tr>
260<tr>
261 <td>
262 <code>user<code>
263 </td>
264 <td>
265 "<code>make user</code>"
266 <p>
267 This is the flavor intended to be the final release bits.
268 <ul>
Elliott Hughes32bfd702013-11-05 11:13:49 -0800[diff] [blame]269 <li>Installs modules tagged with <code>user</code>.
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]270 <li>Installs non-APK modules that have no tags specified.
271 <li>Installs APKs according to the product definition files; tags
272 are ignored for APK modules.
Daniel Micay18a141c2015-12-16 16:42:49 -0500[diff] [blame^]273 <li><code>ro.adb.secure=1</code>
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]274 <li><code>ro.secure=1</code>
275 <li><code>ro.debuggable=0</code>
276 <li><code>adb</code> is disabled by default.
277 </td>
278</tr>
279<tr>
280 <td>
281 <code>userdebug<code>
282 </td>
283 <td>
284 "<code>make userdebug</code>"
285 <p>
286 The same as <code>user</code>, except:
287 <ul>
288 <li>Also installs modules tagged with <code>debug</code>.
289 <li><code>ro.debuggable=1</code>
290 <li><code>adb</code> is enabled by default.
291 </td>
292</tr>
293</table>
294
295<p>
296If you build one flavor and then want to build another, you should run
297"<code>make installclean</code>" between the two makes to guarantee that
298you don't pick up files installed by the previous flavor. "<code>make
299clean</code>" will also suffice, but it takes a lot longer.
300</p>
301
302
303<h3>More pseudotargets</h3>
304<p>Sometimes you want to just build one thing. The following pseudotargets are
305there for your convenience:</p>
306
307<ul>
308<li><b>droid</b> - <code>make droid</code> is the normal build. This target
309is here because the default target has to have a name.</li>
310<li><b>all</b> - <code>make all</code> builds everything <code>make
311droid</code> does, plus everything whose <code>LOCAL_MODULE_TAGS</code> do not
312include the "droid" tag. The build server runs this to make sure
313that everything that is in the tree and has an Android.mk builds.</li>
314<li><b>clean-$(LOCAL_MODULE)</b> and <b>clean-$(LOCAL_PACKAGE_NAME)</b> -
315Let you selectively clean one target. For example, you can type
316<code>make clean-libutils</code> and it will delete libutils.so and all of the
317intermediate files, or you can type <code>make clean-Home</code> and it will
318clean just the Home app.</li>
319<li><b>clean</b> - <code>make clean</code> deletes all of the output and
320intermediate files for this configuration. This is the same as <code>rm -rf
321out/&lt;configuration&gt;/</code></li>
322<li><b>clobber</b> - <code>make clobber</code> deletes all of the output
323and intermediate files for all configurations. This is the same as
324<code>rm -rf out/</code>.</li>
325<li><b>dataclean</b> - <code>make dataclean</code> deletes contents of the data
326directory inside the current combo directory. This is especially useful on the
327simulator and emulator, where the persistent data remains present between
328builds.</li>
329<li><b>showcommands</b> - <code>showcommands</code> is a modifier target
330which causes the build system to show the actual command lines for the build
331steps, instead of the brief descriptions. Most people don't like seeing the
332actual commands, because they're quite long and hard to read, but if you need
333to for debugging purposes, you can add <code>showcommands</code> to the list
334of targets you build. For example <code>make showcommands</code> will build
335the default android configuration, and <code>make runtime showcommands</code>
336will build just the runtime, and targets that it depends on, while displaying
337the full command lines. Please note that there are a couple places where the
338commands aren't shown here. These are considered bugs, and should be fixed,
339but they're often hard to track down. Please let
340<a href="mailto:android-build-team">android-build-team</a> know if you find
341any.</li>
342<li><b>LOCAL_MODULE</b> - Anything you specify as a <code>LOCAL_MODULE</code>
343in an Android.mk is made into a pseudotarget. For example, <code>make
344runtime</code> might be shorthand for <code>make
345out/linux-x86-debug/system/bin/runtime</code> (which would work), and
346<code>make libkjs</code> might be shorthand for <code>make
347out/linux-x86-debug/system/lib/libkjs.so</code> (which would also work).</li>
348<li><b>targets</b> - <code>make targets</code> will print a list of all of
349the LOCAL_MODULE names you can make.</li>
350</ul>
351
352<h3><a name="templates"/>How to add another component to the build - Android.mk templates</h3>
353<p>You have a new library, a new app, or a new executable. For each of the
354common types of modules, there is a corresponding file in the templates
355directory. It will usually be enough to copy one of these, and fill in your
356own values. Some of the more esoteric values are not included in the
357templates, but are instead just documented here, as is the documentation
358on using custom tools to generate files.</p>
359<p>Mostly, you can just look for the TODO comments in the templates and do
360what it says. Please remember to delete the TODO comments when you're done
361to keep the files clean. The templates have minimal documentation in them,
362because they're going to be copied, and when that gets stale, the copies just
363won't get updated. So read on...</p>
364
365<h4>Apps</h4>
366<p>Use the <code>templates/apps</code> file.</p>
367<p>This template is pretty self-explanitory. See the variables below for more
368details.</p>
369
370<h4>Java Libraries</h4>
371<p>Use the <code>templates/java_library</code> file.</p>
372<p>The interesting thing here is the value of LOCAL_MODULE, which becomes
373the name of the jar file. (Actually right now, we're not making jar files yet,
374just directories of .class files, but the directory is named according to
375what you put in LOCAL_MODULE). This name will be what goes in the
376LOCAL_JAVA_LIBRARIES variable in modules that depend on your java library.</p>
377
378<h4>C/C++ Executables</h4>
379<p>Use the <code>templates/executable</code> file, or the
380<code>templates/executable_host</code> file.</p>
381<p>This template has a couple extra options that you usually don't need.
382Please delete the ones you don't need, and remove the TODO comments. It makes
383the rest of them easier to read, and you can always refer back to the templates
384if you need them again later.</p>
385<p>By default, on the target these are built into /system/bin, and on the
386host, they're built into <combo>/host/bin. These can be overridden by setting
Colin Cross639c3362014-01-24 19:23:40 -0800[diff] [blame]387<code>LOCAL_MODULE_PATH</code> or <code>LOCAL_MODULE_RELATIVE_PATH</code>. See
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]388<a href="#moving-targets">Putting targets elsewhere</a>
389for more.</p>
390
391<h4>Shared Libraries</h4>
392<p>Use the <code>templates/shared_library</code> file, or the
393<code>templates/shared_library_host</code> file.</p>
394<p>Remember that on the target, we use shared libraries, and on the host,
395we use static libraries, since executable size isn't as big an issue, and it
396simplifies distribution in the SDK.</p>
397
398<h4>Static Libraries</h4>
399<p>Use the <code>templates/static_library</code> file, or the
400<code>templates/static_library_host</code> file.</p>
401<p>Remember that on the target, we use shared libraries, and on the host,
402we use static libraries, since executable size isn't as big an issue, and it
403simplifies distribution in the SDK.</p>
404
405<h4><a name="custom-tools"/>Using Custom Tools</h4>
406<p>If you have a tool that generates source files for you, it's possible
407to have the build system get the dependencies correct for it. Here are
408a couple of examples. <code>$@</code> is the make built-in variable for
409"the current target." The <font color=red>red</font> parts are the parts you'll
410need to change.</p>
411
412<p>You need to put this after you have declared <code>LOCAL_PATH</code> and
Colin Crossd8262642014-01-24 23:17:21 -0800[diff] [blame]413<code>LOCAL_MODULE</code>, because the <code>$(local-generated-sources-dir)</code>
414and <code>$(local-host-generated-sources-dir)</code> macros use these variables
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]415to determine where to put the files.
416
417<h5>Example 1</h5>
418<p>Here, there is one generated file, called
419chartables.c, which doesn't depend on anything. And is built by the tool
420built to $(HOST_OUT_EXECUTABLES)/dftables. Note on the second to last line
421that a dependency is created on the tool.</p>
422<pre>
Colin Crossd8262642014-01-24 23:17:21 -0800[diff] [blame]423intermediates:= $(local-generated-sources-dir)
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]424GEN := $(intermediates)/<font color=red>chartables.c</font>
425$(GEN): PRIVATE_CUSTOM_TOOL = <font color=red>$(HOST_OUT_EXECUTABLES)/dftables $@</font>
426$(GEN): <font color=red>$(HOST_OUT_EXECUTABLES)/dftables</font>
427 $(transform-generated-source)
428LOCAL_GENERATED_SOURCES += $(GEN)
429</pre>
430
431<h5>Example 2</h5>
432<p>Here as a hypothetical example, we use use cat as if it were to transform
433a file. Pretend that it does something useful. Note how we use a
434target-specific variable called PRIVATE_INPUT_FILE to store the name of the
435input file.</p>
436<pre>
Colin Crossd8262642014-01-24 23:17:21 -0800[diff] [blame]437intermediates:= $(local-generated-sources-dir)
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]438GEN := $(intermediates)/<font color=red>file.c</font>
439$(GEN): PRIVATE_INPUT_FILE := $(LOCAL_PATH)/<font color=red>input.file</font>
440$(GEN): PRIVATE_CUSTOM_TOOL = <font color=red>cat $(PRIVATE_INPUT_FILE) &gt; $@</font>
441$(GEN): <font color=red>$(LOCAL_PATH)/file.c</font>
442 $(transform-generated-source)
443LOCAL_GENERATED_SOURCES += $(GEN)
444</pre>
445
446<h5>Example 3</h5>
447<p>If you have several files that are all similar in
448name, and use the same tool, you can combine them. (here the *.lut.h files are
449the generated ones, and the *.cpp files are the input files)</p>
450<pre>
Colin Crossd8262642014-01-24 23:17:21 -0800[diff] [blame]451intermediates:= $(local-generated-sources-dir)
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]452GEN := $(addprefix $(intermediates)<font color=red>/kjs/, \
453 array_object.lut.h \
454 bool_object.lut.h \</font>
455 )
456$(GEN): PRIVATE_CUSTOM_TOOL = <font color=red>perl libs/WebKitLib/WebKit/JavaScriptCore/kjs/create_hash_table $< -i > $@</font>
457$(GEN): $(intermediates)/<font color=red>%.lut.h</font> : $(LOCAL_PATH)/<font color=red>%.cpp</font>
458 $(transform-generated-source)
459LOCAL_GENERATED_SOURCES += $(GEN)
460</pre>
461
462<h3><a name="platform-specific"/>Platform specific conditionals</h3>
463<p>Sometimes you need to set flags specifically for different platforms. Here
464is a list of which values the different build-system defined variables will be
465set to and some examples.</p>
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]466<table cellspacing=25>
467<tr>
468 <td valign=top align=center>
469 <b>HOST_OS</b><br/>
470 linux<br/>
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]471 darwin
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]472 </td>
473 <td valign=top align=center>
474 <b>HOST_ARCH</b><br/>
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]475 x86<br/>
476 x86_64
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]477 </td>
478 <td valign=top align=center>
479 <b>HOST_BUILD_TYPE</b><br/>
480 release<br/>
481 debug
482 </td>
483</tr>
484<tr>
485 <td valign=top align=center>
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]486 <b>TARGET_ARCH</b><br/>
487 arm<br/>
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]488 arm64<br/>
489 mips<br/>
490 mips64<br/>
491 x86<br/>
492 x86_64
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]493 </td>
494 <td valign=top align=center>
495 <b>TARGET_BUILD_TYPE</b><br/>
496 release<br/>
497 debug
498 </td>
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]499</tr>
500</table>
501
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]502<p>There are also special variables to use instead of conditionals. Many of the
503normal variables (LOCAL_SRC_FILES, LOCAL_CFLAGS, etc) can be conditionally added
504to with _{arch} _{32|64}, and for the host, _{os}.</p>
505
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]506<h4>Some Examples</h4>
Jeff Browne33ba4c2011-07-11 22:11:46 -0700[diff] [blame]507<pre>ifeq ($(TARGET_BUILD_TYPE),release)
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]508LOCAL_CFLAGS += -DNDEBUG=1
509endif
510
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]511LOCAL_CFLAGS_arm += -DTARGET_IS_ARM
512
513LOCAL_CFLAGS_64 += -DBIG_POINTER
514
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]515# from libutils
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]516# Use the futex based mutex and condition variable
517# implementation from android-arm because it's shared mem safe
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]518LOCAL_SRC_FILES_linux += futex_synchro.c
519LOCAL_LDLIBS_linux += -lrt -ldl
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]520
521</pre>
522
523
524<h3><a name="moving-modules"/>Putting modules elsewhere</h3>
525<p>If you have modules that normally go somewhere, and you need to have them
Colin Cross639c3362014-01-24 19:23:40 -0800[diff] [blame]526build somewhere else, read this.</p>
527<p>If you have modules that need to go in a subdirectory of their normal
528location, for example HAL modules that need to go in /system/lib/hw or
529/vendor/lib/hw, set LOCAL_MODULE_RELATIVE_PATH in your Android.mk, for
530example:</p>
531<pre>
532LOCAL_MODULE_RELATIVE_PATH := hw
533</pre>
534<p>If you have modules that need to go in an entirely different location, for
535example the root filesystem instead of in /system, add these lines to your
536Android.mk:</p>
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]537<pre>
538LOCAL_MODULE_PATH := $(TARGET_ROOT_OUT_SBIN)
539LOCAL_UNSTRIPPED_PATH := $(TARGET_ROOT_OUT_SBIN_UNSTRIPPED)
540</pre>
Colin Cross639c3362014-01-24 19:23:40 -0800[diff] [blame]541<p>For executables and libraries, you need to specify a
542<code>LOCAL_UNSTRIPPED_PATH</code> location if you specified a
543<code>LOCAL_MODULE_PATH</code>, because on target builds, we keep
544the unstripped executables so GDB can find the symbols.
545<code>LOCAL_UNSTRIPPED_PATH</code> is not necessary if you only specified
546<code>LOCAL_MODULE_RELATIVE_PATH</code>.</p>
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]547<p>Look in <code>core/envsetup.mk</code> for all of the variables defining
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]548places to build things.</p>
549<p>FYI: If you're installing an executable to /sbin, you probably also want to
550set <code>LOCAL_FORCE_STATIC_EXCUTABLE := true</code> in your Android.mk, which
551will force the linker to only accept static libraries.</p>
552
553
554<h3>Android.mk variables</h3>
555<p>These are the variables that you'll commonly see in Android.mk files, listed
556alphabetically.</p>
557<p>But first, a note on variable naming:
558<ul>
559 <li><b>LOCAL_</b> - These variables are set per-module. They are cleared
560 by the <code>include $(CLEAR_VARS)</code> line, so you can rely on them
561 being empty after including that file. Most of the variables you'll use
562 in most modules are LOCAL_ variables.</li>
563 <li><b>PRIVATE_</b> - These variables are make-target-specific variables. That
564 means they're only usable within the commands for that module. It also
565 means that they're unlikely to change behind your back from modules that
566 are included after yours. This
567 <a href="http://www.gnu.org/software/make/manual/make.html#Target_002dspecific">link to the make documentation</a>
568 describes more about target-specific variables. Please note that there
569 are a couple of these laying around the tree that aren't prefixed with
570 PRIVATE_. It is safe, and they will be fixed as they are discovered.
571 Sorry for the confusion.</li>
572 <li><b>INTERNAL_</b> - These variables are critical to functioning of
573 the build system, so you shouldn't create variables named like this, and
574 you probably shouldn't be messing with these variables in your makefiles.
575 </li>
576 <li><b>HOST_</b> and <b>TARGET_</b> - These contain the directories
577 and definitions that are specific to either the host or the target builds.
578 Do not set variables that start with HOST_ or TARGET_ in your makefiles.
579 </li>
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]580 <li><b>HOST_CROSS_</b> - These contain the directories and definitions that
581 are specific to cross-building host binaries. The common case is building
582 windows host tools on linux. Do not set variables that start with
583 HOST_CROSS_ in your makefiles.
584 </li>
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]585 <li><b>BUILD_</b> and <b>CLEAR_VARS</b> - These contain the names of
586 well-defined template makefiles to include. Some examples are CLEAR_VARS
587 and BUILD_HOST_PACKAGE.</li>
588 <li>Any other name is fair-game for you to use in your Android.mk. However,
589 remember that this is a non-recursive build system, so it is possible that
590 your variable will be changed by another Android.mk included later, and be
591 different when the commands for your rule / module are executed.</li>
592</ul>
593</p>
594
595<h4>LOCAL_ASSET_FILES</h4>
596<p>In Android.mk files that <code>include $(BUILD_PACKAGE)</code> set this
597to the set of files you want built into your app. Usually:</p>
598<p><code>LOCAL_ASSET_FILES += $(call find-subdir-assets)</code></p>
599<p>This will probably change when we switch to ant for the apps' build
600system.</p>
601
602<h4>LOCAL_CC</h4>
603<p>If you want to use a different C compiler for this module, set LOCAL_CC
604to the path to the compiler. If LOCAL_CC is blank, the appropriate default
605compiler is used.</p>
606
607<h4>LOCAL_CXX</h4>
608<p>If you want to use a different C++ compiler for this module, set LOCAL_CXX
609to the path to the compiler. If LOCAL_CXX is blank, the appropriate default
610compiler is used.</p>
611
612<h4>LOCAL_CFLAGS</h4>
613<p>If you have additional flags to pass into the C or C++ compiler, add
614them here. For example:</p>
615<p><code>LOCAL_CFLAGS += -DLIBUTILS_NATIVE=1</code></p>
616
617<h4>LOCAL_CPPFLAGS</h4>
618<p>If you have additional flags to pass into <i>only</i> the C++ compiler, add
619them here. For example:</p>
620<p><code>LOCAL_CPPFLAGS += -ffriend-injection</code></p>
621<code>LOCAL_CPPFLAGS</code> is guaranteed to be after <code>LOCAL_CFLAGS</code>
622on the compile line, so you can use it to override flags listed in
623<code>LOCAL_CFLAGS</code>.
624
625<h4>LOCAL_CPP_EXTENSION</h4>
626<p>If your C++ files end in something other than "<code>.cpp</code>",
627you can specify the custom extension here. For example:</p>
628<p><code>LOCAL_CPP_EXTENSION := .cc</code></p>
629Note that all C++ files for a given module must have the same
630extension; it is not currently possible to mix different extensions.
631
632<h4>LOCAL_NO_DEFAULT_COMPILER_FLAGS</h4>
633<p>Normally, the compile line for C and C++ files includes global include
634paths and global cflags. If <code>LOCAL_NO_DEFAULT_COMPILER_FLAGS</code>
635is non-empty, none of the default includes or flags will be used when compiling
636C and C++ files in this module.
637<code>LOCAL_C_INCLUDES</code>, <code>LOCAL_CFLAGS</code>, and
638<code>LOCAL_CPPFLAGS</code> will still be used in this case, as will
639any <code>DEBUG_CFLAGS</code> that are defined for the module.
640
641<h4>LOCAL_COPY_HEADERS</h4>
642<p class=warning>This will be going away.</p>
643<p>The set of files to copy to the install include tree. You must also
644supply <code>LOCAL_COPY_HEADERS_TO</code>.</p>
645<p>This is going away because copying headers messes up the error messages, and
646may lead to people editing those headers instead of the correct ones. It also
647makes it easier to do bad layering in the system, which we want to avoid. We
648also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any
649headers.</p>
650
651<h4>LOCAL_COPY_HEADERS_TO</h4>
652<p class=warning>This will be going away.</p>
653<p>The directory within "include" to copy the headers listed in
654<code>LOCAL_COPY_HEADERS</code> to.</p>
655<p>This is going away because copying headers messes up the error messages, and
656may lead to people editing those headers instead of the correct ones. It also
657makes it easier to do bad layering in the system, which we want to avoid. We
658also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any
659headers.</p>
660
661<h4>LOCAL_C_INCLUDES</h4>
662<p>Additional directories to instruct the C/C++ compilers to look for header
663files in. These paths are rooted at the top of the tree. Use
664<code>LOCAL_PATH</code> if you have subdirectories of your own that you
665want in the include paths. For example:</p>
666<p><code>
667LOCAL_C_INCLUDES += extlibs/zlib-1.2.3<br/>
668LOCAL_C_INCLUDES += $(LOCAL_PATH)/src
669</code></p>
670<p>You should not add subdirectories of include to
671<code>LOCAL_C_INCLUDES</code>, instead you should reference those files
672in the <code>#include</code> statement with their subdirectories. For
673example:</p>
674<p><code>#include &lt;utils/KeyedVector.h&gt;</code><br/>
675not <code><s>#include &lt;KeyedVector.h&gt;</s></code></p>
676<p>There are some components that are doing this wrong, and should be cleaned
677up.</p>
678
679<h4>LOCAL_MODULE_TAGS</h4>
680<p>Set <code>LOCAL_MODULE_TAGS</code> to any number of whitespace-separated
681tags. If the tag list is empty or contains <code>droid</code>, the module
Elliott Hughes32bfd702013-11-05 11:13:49 -0800[diff] [blame]682will get installed as part of a <code>make droid</code>. Otherwise, it will
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]683only get installed by running <code>make &lt;your-module&gt;</code>
684or with the <code>make all</code> pseudotarget.</p>
685
686<h4>LOCAL_REQUIRED_MODULES</h4>
687<p>Set <code>LOCAL_REQUIRED_MODULES</code> to any number of whitespace-separated
688module names, like "libblah" or "Email". If this module is installed, all
689of the modules that it requires will be installed as well. This can be
690used to, e.g., ensure that necessary shared libraries or providers are
691installed when a given app is installed.
692
693<h4>LOCAL_FORCE_STATIC_EXECUTABLE</h4>
694<p>If your executable should be linked statically, set
695<code>LOCAL_FORCE_STATIC_EXECUTABLE:=true</code>. There is a very short
696list of libraries that we have in static form (currently only libc). This is
697really only used for executables in /sbin on the root filesystem.</p>
698
699<h4>LOCAL_GENERATED_SOURCES</h4>
700<p>Files that you add to <code>LOCAL_GENERATED_SOURCES</code> will be
701automatically generated and then linked in when your module is built.
702See the <a href="#custom-tools">Custom Tools</a> template makefile for an
703example.</p>
704
Brian Carlstromf184a0f2010-02-01 11:13:32 -0800[diff] [blame]705<h4>LOCAL_JAVACFLAGS</h4>
706<p>If you have additional flags to pass into the javac compiler, add
707them here. For example:</p>
708<p><code>LOCAL_JAVACFLAGS += -Xlint:deprecation</code></p>
709
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]710<h4>LOCAL_JAVA_LIBRARIES</h4>
711<p>When linking Java apps and libraries, <code>LOCAL_JAVA_LIBRARIES</code>
712specifies which sets of java classes to include. Currently there are
713two of these: <code>core</code> and <code>framework</code>.
714In most cases, it will look like this:</p>
715<p><code>LOCAL_JAVA_LIBRARIES := core framework</code></p>
716<p>Note that setting <code>LOCAL_JAVA_LIBRARIES</code> is not necessary
717(and is not allowed) when building an APK with
718"<code>include $(BUILD_PACKAGE)</code>". The appropriate libraries
719will be included automatically.</p>
720
721<h4>LOCAL_LDFLAGS</h4>
722<p>You can pass additional flags to the linker by setting
723<code>LOCAL_LDFLAGS</code>. Keep in mind that the order of parameters is
724very important to ld, so test whatever you do on all platforms.</p>
725
726<h4>LOCAL_LDLIBS</h4>
727<p><code>LOCAL_LDLIBS</code> allows you to specify additional libraries
728that are not part of the build for your executable or library. Specify
729the libraries you want in -lxxx format; they're passed directly to the
730link line. However, keep in mind that there will be no dependency generated
731for these libraries. It's most useful in simulator builds where you want
732to use a library preinstalled on the host. The linker (ld) is a particularly
733fussy beast, so it's sometimes necessary to pass other flags here if you're
734doing something sneaky. Some examples:</p>
735<p><code>LOCAL_LDLIBS += -lcurses -lpthread<br/>
736LOCAL_LDLIBS += -Wl,-z,origin
737</code></p>
738
739<h4>LOCAL_NO_MANIFEST</h4>
740<p>If your package doesn't have a manifest (AndroidManifest.xml), then
741set <code>LOCAL_NO_MANIFEST:=true</code>. The common resources package
742does this.</p>
743
744<h4>LOCAL_PACKAGE_NAME</h4>
745<p><code>LOCAL_PACKAGE_NAME</code> is the name of an app. For example,
746Dialer, Contacts, etc. This will probably change or go away when we switch
747to an ant-based build system for the apps.</p>
748
749<h4>LOCAL_PATH</h4>
750<p>The directory your Android.mk file is in. You can set it by putting the
751following as the first line in your Android.mk:</p>
752<p><code>LOCAL_PATH := $(my-dir)</code></p>
753<p>The <code>my-dir</code> macro uses the
754<code><a href="http://www.gnu.org/software/make/manual/make.html#MAKEFILE_005fLIST-Variable">MAKEFILE_LIST</a></code>
755variable, so you must call it before you include any other makefiles. Also,
756consider that any subdirectories you inlcude might reset LOCAL_PATH, so do your
757own stuff before you include them. This also means that if you try to write
758several <code>include</code> lines that reference <code>LOCAL_PATH</code>,
759it won't work, because those included makefiles might reset LOCAL_PATH.
760
761<h4>LOCAL_POST_PROCESS_COMMAND</h4>
762<p>For host executables, you can specify a command to run on the module
763after it's been linked. You might have to go through some contortions
764to get variables right because of early or late variable evaluation:</p>
765<p><code>module := $(HOST_OUT_EXECUTABLES)/$(LOCAL_MODULE)<br/>
766LOCAL_POST_PROCESS_COMMAND := /Developer/Tools/Rez -d __DARWIN__ -t APPL\<br/>
767&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;-d __WXMAC__ -o $(module) Carbon.r
768</code></p>
769
770<h4>LOCAL_PREBUILT_EXECUTABLES</h4>
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]771<p>When including $(BUILD_MULTI_PREBUILT) or $(BUILD_HOST_PREBUILT), set these
772to executables that you want copied. They're located automatically into the
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]773right bin directory.</p>
774
775<h4>LOCAL_PREBUILT_LIBS</h4>
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]776<p>When including $(BUILD_MULTI_PREBUILT) or $(BUILD_HOST_PREBUILT), set these
777to libraries that you want copied. They're located automatically into the
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]778right lib directory.</p>
779
780<h4>LOCAL_SHARED_LIBRARIES</h4>
781<p>These are the libraries you directly link against. You don't need to
782pass transitively included libraries. Specify the name without the suffix:</p>
783<p><code>LOCAL_SHARED_LIBRARIES := \<br/>
784 &nbsp;&nbsp;&nbsp;&nbsp;libutils \<br/>
785 &nbsp;&nbsp;&nbsp;&nbsp;libui \<br/>
786 &nbsp;&nbsp;&nbsp;&nbsp;libaudio \<br/>
787 &nbsp;&nbsp;&nbsp;&nbsp;libexpat \<br/>
788 &nbsp;&nbsp;&nbsp;&nbsp;libsgl
789</code></p>
790
791<h4>LOCAL_SRC_FILES</h4>
792<p>The build system looks at <code>LOCAL_SRC_FILES</code> to know what source
793files to compile -- .cpp .c .y .l .java. For lex and yacc files, it knows
794how to correctly do the intermediate .h and .c/.cpp files automatically. If
795the files are in a subdirectory of the one containing the Android.mk, prefix
796them with the directory name:</p>
797<p><code>LOCAL_SRC_FILES := \<br/>
798 &nbsp;&nbsp;&nbsp;&nbsp;file1.cpp \<br/>
799 &nbsp;&nbsp;&nbsp;&nbsp;dir/file2.cpp
800</code></p>
801
802<h4>LOCAL_STATIC_LIBRARIES</h4>
803<p>These are the static libraries that you want to include in your module.
804Mostly, we use shared libraries, but there are a couple of places, like
805executables in sbin and host executables where we use static libraries instead.
806<p><code>LOCAL_STATIC_LIBRARIES := \<br/>
807 &nbsp;&nbsp;&nbsp;&nbsp;libutils \<br/>
808 &nbsp;&nbsp;&nbsp;&nbsp;libtinyxml
809</code></p>
810
811<h4>LOCAL_MODULE</h4>
812<p><code>LOCAL_MODULE</code> is the name of what's supposed to be generated
813from your Android.mk. For exmample, for libkjs, the <code>LOCAL_MODULE</code>
814is "libkjs" (the build system adds the appropriate suffix -- .so .dylib .dll).
815For app modules, use <code>LOCAL_PACKAGE_NAME</code> instead of
816<code>LOCAL_MODULE</code>. We're planning on switching to ant for the apps,
817so this might become moot.</p>
818
819<h4>LOCAL_MODULE_PATH</h4>
820<p>Instructs the build system to put the module somewhere other than what's
821normal for its type. If you override this, make sure you also set
822<code>LOCAL_UNSTRIPPED_PATH</code> if it's an executable or a shared library
823so the unstripped binary has somewhere to go. An error will occur if you forget
824to.</p>
825<p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p>
826
Colin Cross639c3362014-01-24 19:23:40 -0800[diff] [blame]827<h4>LOCAL_MODULE_RELATIVE_PATH</h4>
828<p>Instructs the build system to put the module in a subdirectory under the
829directory that is normal for its type. If you set this you do not need to
830set <code>LOCAL_UNSTRIPPED_PATH</code>, the unstripped binaries will also use
831the relative path.</p>
832<p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p>
833
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]834<h4>LOCAL_MODULE_HOST_OS</h4>
835<p>This specifies which OSes are supported by this host module. It is not used
836for target builds. The accepted values here are combinations of
837<code>linux</code>, <code>darwin</code>, and <code>windows</code>. By default,
838linux and darwin(MacOS) are considered to be supported. If a module should
839build under windows, you must specify windows, and any others to be supported.
840Some examples:</p>
841<p><code>LOCAL_MODULE_HOST_OS := linux<br/>
842LOCAL_MODULE_HOST_OS := darwin linux windows</code></p>
843
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]844<h4>LOCAL_UNSTRIPPED_PATH</h4>
845<p>Instructs the build system to put the unstripped version of the module
846somewhere other than what's normal for its type. Usually, you override this
847because you overrode <code>LOCAL_MODULE_PATH</code> for an executable or a
848shared library. If you overrode <code>LOCAL_MODULE_PATH</code>, but not
849<code>LOCAL_UNSTRIPPED_PATH</code>, an error will occur.</p>
850<p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p>
851
852<h4>LOCAL_WHOLE_STATIC_LIBRARIES</h4>
853<p>These are the static libraries that you want to include in your module without allowing
854the linker to remove dead code from them. This is mostly useful if you want to add a static library
855to a shared library and have the static library's content exposed from the shared library.
856<p><code>LOCAL_WHOLE_STATIC_LIBRARIES := \<br/>
857 &nbsp;&nbsp;&nbsp;&nbsp;libsqlite3_android<br/>
858</code></p>
859
860<h4>LOCAL_YACCFLAGS</h4>
861<p>Any flags to pass to invocations of yacc for your module. A known limitation
862here is that the flags will be the same for all invocations of YACC for your
863module. This can be fixed. If you ever need it to be, just ask.</p>
864<p><code>LOCAL_YACCFLAGS := -p kjsyy</code></p>
865
866
867
868<h2>Implementation Details</h2>
869
870<p>You should never have to touch anything in the config directory unless
871you're adding a new platform, new tools, or adding new features to the
872build system. In general, please consult with the build system owner(s)
873(<a href="mailto:android-build-team">android-build-team</a>) before you go
874mucking around in here. That said, here are some notes on what's going on
875under the hood.</p>
876
877<h3>Environment Setup / buildspec.mk Versioning</h3>
878<p>In order to make easier for people when the build system changes, when
879it is necessary to make changes to buildspec.mk or to rerun the environment
880setup scripts, they contain a version number in the variable
881BUILD_ENV_SEQUENCE_NUMBER. If this variable does not match what the build
882system expects, it fails printing an error message explaining what happened.
883If you make a change that requires an update, you need to update two places
884so this message will be printed.
885<ul>
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]886 <li>In core/envsetup.mk, increment the
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]887 CORRECT_BUILD_ENV_SEQUENCE_NUMBER definition.</li>
888 <li>In buildspec.mk.default, update the BUILD_ENV_SEQUENCE_DUMBER
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]889 definition to match the one in core/envsetup.mk</li>
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]890</ul>
891The scripts automatically get the value from the build system, so they will
892trigger the warning as well.
893</p>
894
895<h3>Additional makefile variables</h3>
896<p>You probably shouldn't use these variables. Please consult
897<a href="mailto:android-build-team">android-build-team</a> before using them.
898These are mostly there for workarounds for other issues, or things that aren't
899completely done right.</p>
900
901<h4>LOCAL_ADDITIONAL_DEPENDENCIES</h4>
902<p>If your module needs to depend on anything else that
903isn't actually built in to it, you can add those make targets to
904<code>LOCAL_ADDITIONAL_DEPENDENCIES</code>. Usually this is a workaround
905for some other dependency that isn't created automatically.</p>
906
907<h4>LOCAL_BUILT_MODULE</h4>
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]908<p class=warning>This should not be used, since multiple binaries are now
909created from a single module defintiion.</p>
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]910<p>When a module is built, the module is created in an intermediate
911directory then copied to its final location. LOCAL_BUILT_MODULE is
912the full path to the intermediate file. See LOCAL_INSTALLED_MODULE
913for the path to the final installed location of the module.</p>
914
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]915<h4>LOCAL_IS_HOST_MODULE</h4>
916<p>Set by the host_xxx.mk includes to tell base_rules.mk and the other
917includes that we're building for the host.</p>
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]918
919<h4>LOCAL_INSTALLED_MODULE</h4>
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]920<p class=warning>This should not be used, since multiple binaries are now
921created from a single module defintiion.</p>
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]922<p>The fully qualified path name of the final location of the module.
923See LOCAL_BUILT_MODULE for the location of the intermediate file that
924the make rules should actually be constructing.</p>
925
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]926<h4>LOCAL_MODULE_CLASS</h4>
927<p>Which kind of module this is. This variable is used to construct other
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]928variable names used to locate the modules. See base_rules.mk and
929envsetup.mk.</p>
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]930
931<h4>LOCAL_MODULE_SUFFIX</h4>
932<p>The suffix that will be appended to <code>LOCAL_MODULE</code> to form
933<code>LOCAL_MODULE_NAME</code>. For example, .so, .a, .dylib.</p>
934
935<h4>LOCAL_STRIP_MODULE</h4>
Dan Willemsen0b6c3482015-09-09 16:51:09 -0700[diff] [blame]936<p>If set to true (the default), the binary will be stripped and a debug
937link will be set up so that GDB will still work. If set to no_debuglink,
938the binary will be stripped, but no debug link will be added. If set to
939keep_symbols, it will strip the debug information, but keep the symbol table.
940Any other value will prevent stripping.</p>
Joe Onorato2303bf02008-10-23 19:37:58 -0700[diff] [blame]941
942<h4>LOCAL_SYSTEM_SHARED_LIBRARIES</h4>
943<p>Used while building the base libraries: libc, libm, libdl. Usually
944it should be set to "none," as it is in $(CLEAR_VARS). When building
945these libraries, it's set to the ones they link against. For example,
946libc, libstdc++ and libdl don't link against anything, and libm links against
947libc. Normally, when the value is none, these libraries are automatically
948linked in to executables and libraries, so you don't need to specify them
949manually.</p>
950
951
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953</html>