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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>
				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.
				82	Believe 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
				87	work more reliably, so that when files need to rebuilt, they are, and (2) to
				88	improve performance of the build system so that unnecessary modules are not
				89	rebuilt, and so doing a top-level build when little or nothing needs to be done
				90	for 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
				94	that 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.
				97	This 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
				113	non-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
				114	want 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
				118	possible to easily rebuild just that component, and not have to wait more than a
				119	couple seconds for dependency checks, and not have to wait for unneeded
				120	components 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
				123	configuration file in a directory so they do not have an environment setup
				124	script to run, and others want an environment setup script to run so they can
				125	run builds in different terminals on the same tree, or switch back and forth
				126	in 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
				129	that 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
				131	this are to simplify searching the source tree, and to make "make clean" more
				132	reliable.</p>
				133
				134	<h3>SDK</h3>
				135	<p>The SDK will be a tarball that will allow non-OS-developers to write apps.
				136	The apps will actually be built by first building the SDK, and then building
				137	the apps against that SDK. This will hopefully (1) make writing apps easier
				138	for us, because we won't have to rebuild the OS as much, and we can use the
				139	standard java-app development tools, and (2) allow us to dog-food the SDK, to
				140	help ensure its quality. Cedric has suggested (and I agree) that apps built
				141	from the SDK should be built with ant. Stay tuned for more details as we
				142	figure 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
				148	in 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
				152	executed for make steps. It will be possible to override this by specifying
				153	the showcommands pseudo-target, and possibly by setting an environment
				154	variable.</p>
				155
				156	<h3>Wildcard source files</h3>
				157	<p>Wildcarding source file will be discouraged. It may be useful in some
				158	scenarios. The default <code>$(wildcard *)</code> will not work due to the
				159	current 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
				163	subdirectory. For example, libutils generates a shared library for the target
				164	and 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
				168	control the building of a given module. Only the top directory should
				169	have 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
				173	be fixed, and now is a good time to do it. This implies getting shared
				174	libraries 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,
				180	however 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
				184	tree at the same time, but this is a stretch goal, not a requirement.
				185	Doing two builds in the same tree, not at the same time must work. (update:
				186	it'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
				191	should 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
				193	problem is that this can create extra dependecies and slow down the build.
				194	It's a tradeoff.</p>
				195
				196	<h3>Multiple builds</h3>
				197	<p>General way to perform builds across the set of known platforms. This
				198	would make it easy to perform multiple platform builds when testing a
				199	change, and allow a wide-scale "make clean". Right now the buildspec.mk
				200	or 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
				204	customizations 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,
				209	and 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
				213	builds.</p>
				214
				215	<h3>build/envsetup.sh functions</h3>
				216	If 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
				221	lunch and choosecombo commands.</li>
				222	<li><b>m</b> - Runs <code>make</code> from the top of the tree. This is
				223	useful 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
				225	up 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,
				228	and .xml files below the current directory.</li>
				229	</ul>
				230
				231	<h3>Build flavors/types</h3>
				232	<p>
				233	When building for a particular product, it's often useful to have minor
				234	variations on what is ultimately the final release build. These are the
				235	currently-defined "flavors" or "types" (we need to settle on a real name
				236	for 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>,
Thorsten Glaser	2213aab	2010-06-03 19:57:02 +0200	[diff] [blame]	250	<code>shell_</code>$(TARGET_SHELL),
Joe Onorato	2303bf0	2008-10-23 19:37:58 -0700	[diff] [blame]	251	<code>user</code>, and/or <code>development</code>.
				252	<li>Installs non-APK modules that have no tags specified.
				253	<li>Installs APKs according to the product definition files, in
				254	addition to tagged APKs.
				255	<li><code>ro.secure=0</code>
				256	<li><code>ro.debuggable=1</code>
				257	<li><code>ro.kernel.android.checkjni=1</code>
				258	<li><code>adb</code> is enabled by default.
				259	</td>
				260	</tr>
				261	<tr>
				262	<td>
				263	<code>user<code>
				264	</td>
				265	<td>
				266	"<code>make user</code>"
				267	<p>
				268	This is the flavor intended to be the final release bits.
				269	<ul>
Thorsten Glaser	2213aab	2010-06-03 19:57:02 +0200	[diff] [blame]	270	<li>Installs modules tagged with <code>shell_</code>$(TARGET_SHELL) and <code>user</code>.
Joe Onorato	2303bf0	2008-10-23 19:37:58 -0700	[diff] [blame]	271	<li>Installs non-APK modules that have no tags specified.
				272	<li>Installs APKs according to the product definition files; tags
				273	are ignored for APK modules.
				274	<li><code>ro.secure=1</code>
				275	<li><code>ro.debuggable=0</code>
				276	<li><code>adb</code> is disabled by default.
				277	</td>
				278	</tr>
				279	<tr>
				280	<td>
				281	<code>userdebug<code>
				282	</td>
				283	<td>
				284	"<code>make userdebug</code>"
				285	<p>
				286	The same as <code>user</code>, except:
				287	<ul>
				288	<li>Also installs modules tagged with <code>debug</code>.
				289	<li><code>ro.debuggable=1</code>
				290	<li><code>adb</code> is enabled by default.
				291	</td>
				292	</tr>
				293	</table>
				294
				295	<p>
				296	If you build one flavor and then want to build another, you should run
				297	"<code>make installclean</code>" between the two makes to guarantee that
				298	you don't pick up files installed by the previous flavor. "<code>make
				299	clean</code>" will also suffice, but it takes a lot longer.
				300	</p>
				301
				302
				303	<h3>More pseudotargets</h3>
				304	<p>Sometimes you want to just build one thing. The following pseudotargets are
				305	there for your convenience:</p>
				306
				307	<ul>
				308	<li><b>droid</b> - <code>make droid</code> is the normal build. This target
				309	is here because the default target has to have a name.</li>
				310	<li><b>all</b> - <code>make all</code> builds everything <code>make
				311	droid</code> does, plus everything whose <code>LOCAL_MODULE_TAGS</code> do not
				312	include the "droid" tag. The build server runs this to make sure
				313	that everything that is in the tree and has an Android.mk builds.</li>
				314	<li><b>clean-$(LOCAL_MODULE)</b> and <b>clean-$(LOCAL_PACKAGE_NAME)</b> -
				315	Let 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
				317	intermediate files, or you can type <code>make clean-Home</code> and it will
				318	clean just the Home app.</li>
				319	<li><b>clean</b> - <code>make clean</code> deletes all of the output and
				320	intermediate files for this configuration. This is the same as <code>rm -rf
				321	out/<configuration>/</code></li>
				322	<li><b>clobber</b> - <code>make clobber</code> deletes all of the output
				323	and 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
				326	directory inside the current combo directory. This is especially useful on the
				327	simulator and emulator, where the persistent data remains present between
				328	builds.</li>
				329	<li><b>showcommands</b> - <code>showcommands</code> is a modifier target
				330	which causes the build system to show the actual command lines for the build
				331	steps, instead of the brief descriptions. Most people don't like seeing the
				332	actual commands, because they're quite long and hard to read, but if you need
				333	to for debugging purposes, you can add <code>showcommands</code> to the list
				334	of targets you build. For example <code>make showcommands</code> will build
				335	the default android configuration, and <code>make runtime showcommands</code>
				336	will build just the runtime, and targets that it depends on, while displaying
				337	the full command lines. Please note that there are a couple places where the
				338	commands aren't shown here. These are considered bugs, and should be fixed,
				339	but they're often hard to track down. Please let
				340	<a href="mailto:android-build-team">android-build-team</a> know if you find
				341	any.</li>
				342	<li><b>LOCAL_MODULE</b> - Anything you specify as a <code>LOCAL_MODULE</code>
				343	in an Android.mk is made into a pseudotarget. For example, <code>make
				344	runtime</code> might be shorthand for <code>make
				345	out/linux-x86-debug/system/bin/runtime</code> (which would work), and
				346	<code>make libkjs</code> might be shorthand for <code>make
				347	out/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
				349	the 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
				354	common types of modules, there is a corresponding file in the templates
				355	directory. It will usually be enough to copy one of these, and fill in your
				356	own values. Some of the more esoteric values are not included in the
				357	templates, but are instead just documented here, as is the documentation
				358	on using custom tools to generate files.</p>
				359	<p>Mostly, you can just look for the TODO comments in the templates and do
				360	what it says. Please remember to delete the TODO comments when you're done
				361	to keep the files clean. The templates have minimal documentation in them,
				362	because they're going to be copied, and when that gets stale, the copies just
				363	won'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
				368	details.</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
				373	the name of the jar file. (Actually right now, we're not making jar files yet,
				374	just directories of .class files, but the directory is named according to
				375	what you put in LOCAL_MODULE). This name will be what goes in the
				376	LOCAL_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.
				382	Please delete the ones you don't need, and remove the TODO comments. It makes
				383	the rest of them easier to read, and you can always refer back to the templates
				384	if you need them again later.</p>
				385	<p>By default, on the target these are built into /system/bin, and on the
				386	host, they're built into <combo>/host/bin. These can be overridden by setting
				387	<code>LOCAL_MODULE_PATH</code>. See
				388	<a href="#moving-targets">Putting targets elsewhere</a>
				389	for 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,
				395	we use static libraries, since executable size isn't as big an issue, and it
				396	simplifies 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,
				402	we use static libraries, since executable size isn't as big an issue, and it
				403	simplifies 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
				407	to have the build system get the dependencies correct for it. Here are
				408	a 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
				410	need to change.</p>
				411
				412	<p>You need to put this after you have declared <code>LOCAL_PATH</code> and
				413	<code>LOCAL_MODULE</code>, because the <code>$(local-intermediates-dir)</code>
				414	and <code>$(local-host-intermediates-dir)</code> macros use these variables
				415	to determine where to put the files.
				416
				417	<h5>Example 1</h5>
				418	<p>Here, there is one generated file, called
				419	chartables.c, which doesn't depend on anything. And is built by the tool
				420	built to $(HOST_OUT_EXECUTABLES)/dftables. Note on the second to last line
				421	that a dependency is created on the tool.</p>
				422	<pre>
				423	intermediates:= $(local-intermediates-dir)
				424	GEN := $(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)
				428	LOCAL_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
				433	a file. Pretend that it does something useful. Note how we use a
				434	target-specific variable called PRIVATE_INPUT_FILE to store the name of the
				435	input file.</p>
				436	<pre>
				437	intermediates:= $(local-intermediates-dir)
				438	GEN := $(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) > $@</font>
				441	$(GEN): <font color=red>$(LOCAL_PATH)/file.c</font>
				442	$(transform-generated-source)
				443	LOCAL_GENERATED_SOURCES += $(GEN)
				444	</pre>
				445
				446	<h5>Example 3</h5>
				447	<p>If you have several files that are all similar in
				448	name, and use the same tool, you can combine them. (here the *.lut.h files are
				449	the generated ones, and the *.cpp files are the input files)</p>
				450	<pre>
				451	intermediates:= $(local-intermediates-dir)
				452	GEN := $(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)
				459	LOCAL_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
				464	is a list of which values the different build-system defined variables will be
				465	set to and some examples.</p>
				466	<p>For a device build, <code>TARGET_OS</code> is <code>linux</code> (we're using
				467	linux!), and <code>TARGET_ARCH</code> is <code>arm</code>.</p>
				468	<p>For a simulator build, <code>TARGET_OS</code> and <code>TARGET_ARCH</code>
				469	are set to the same as <code>HOST_OS</code> and <code>HOST_ARCH</code> are
				470	on your platform. <code>TARGET_PRODUCT</code> is the name of the target
				471	hardware/product you are building for. The value <code>sim</code> is used
				472	for the simulator. We haven't thought through the full extent of customization
				473	that will happen here, but likely there will be additional UI configurations
				474	specified here as well.</p>
				475	<table cellspacing=25>
				476	<tr>
				477	<td valign=top align=center>
				478	<b>HOST_OS</b><br/>
				479	linux<br/>
				480	darwin<br/>
				481	(cygwin)
				482	</td>
				483	<td valign=top align=center>
				484	<b>HOST_ARCH</b><br/>
				485	x86
				486	</td>
				487	<td valign=top align=center>
				488	<b>HOST_BUILD_TYPE</b><br/>
				489	release<br/>
				490	debug
				491	</td>
				492	</tr>
				493	<tr>
				494	<td valign=top align=center>
				495	<b>TARGET_OS</b><br/>
				496	linux<br/>
				497	darwin<br/>
				498	(cygwin)
				499	</td>
				500	<td valign=top align=center>
				501	<b>TARGET_ARCH</b><br/>
				502	arm<br/>
				503	x86
				504	</td>
				505	<td valign=top align=center>
				506	<b>TARGET_BUILD_TYPE</b><br/>
				507	release<br/>
				508	debug
				509	</td>
				510	<td valign=top align=center>
				511	<b>TARGET_PRODUCT</b><br/>
				512	sim<br/>
				513	dream<br/>
				514	sooner
				515	</td>
				516	</tr>
				517	</table>
				518
				519	<h4>TARGET_SIMULATOR</h4>
				520	<p>If we're building the simulator, as opposed to the arm or emulator builds,
				521	<code>TARGET_SIMULATOR</code> will be set to <code>true</code>.
				522
				523	<h4>Some Examples</h4>
				524	<pre>ifeq ($(TARGET_SIMULATOR),true)
				525	LOCAL_CFLAGS += -DSIMULATOR
				526	endif
				527
				528	ifeq ($(TARGET_BUILD_TYPE),release)
				529	LOCAL_CFLAGS += -DNDEBUG=1
				530	endif
				531
				532	# from libutils
				533	ifeq ($(TARGET_OS),linux)
				534	# Use the futex based mutex and condition variable
				535	# implementation from android-arm because it's shared mem safe
				536	LOCAL_SRC_FILES += futex_synchro.c
				537	LOCAL_LDLIBS += -lrt -ldl
				538	endif
				539
				540	</pre>
				541
				542
				543	<h3><a name="moving-modules"/>Putting modules elsewhere</h3>
				544	<p>If you have modules that normally go somewhere, and you need to have them
				545	build somewhere else, read this. One use of this is putting files on
				546	the root filesystem instead of where they normally go in /system. Add these
				547	lines to your Android.mk:</p>
				548	<pre>
				549	LOCAL_MODULE_PATH := $(TARGET_ROOT_OUT_SBIN)
				550	LOCAL_UNSTRIPPED_PATH := $(TARGET_ROOT_OUT_SBIN_UNSTRIPPED)
				551	</pre>
				552	<p>For executables and libraries, you need to also specify a
				553	<code>LOCAL_UNSTRIPPED_PATH</code> location, because on target builds, we keep
				554	the unstripped executables so GDB can find the symbols.</code>
				555	<p>Look in <code>config/envsetup.make</code> for all of the variables defining
				556	places to build things.</p>
				557	<p>FYI: If you're installing an executable to /sbin, you probably also want to
				558	set <code>LOCAL_FORCE_STATIC_EXCUTABLE := true</code> in your Android.mk, which
				559	will force the linker to only accept static libraries.</p>
				560
				561
				562	<h3>Android.mk variables</h3>
				563	<p>These are the variables that you'll commonly see in Android.mk files, listed
				564	alphabetically.</p>
				565	<p>But first, a note on variable naming:
				566	<ul>
				567	<li><b>LOCAL_</b> - These variables are set per-module. They are cleared
				568	by the <code>include $(CLEAR_VARS)</code> line, so you can rely on them
				569	being empty after including that file. Most of the variables you'll use
				570	in most modules are LOCAL_ variables.</li>
				571	<li><b>PRIVATE_</b> - These variables are make-target-specific variables. That
				572	means they're only usable within the commands for that module. It also
				573	means that they're unlikely to change behind your back from modules that
				574	are included after yours. This
				575	<a href="http://www.gnu.org/software/make/manual/make.html#Target_002dspecific">link to the make documentation</a>
				576	describes more about target-specific variables. Please note that there
				577	are a couple of these laying around the tree that aren't prefixed with
				578	PRIVATE_. It is safe, and they will be fixed as they are discovered.
				579	Sorry for the confusion.</li>
				580	<li><b>INTERNAL_</b> - These variables are critical to functioning of
				581	the build system, so you shouldn't create variables named like this, and
				582	you probably shouldn't be messing with these variables in your makefiles.
				583	</li>
				584	<li><b>HOST_</b> and <b>TARGET_</b> - These contain the directories
				585	and definitions that are specific to either the host or the target builds.
				586	Do not set variables that start with HOST_ or TARGET_ in your makefiles.
				587	</li>
				588	<li><b>BUILD_</b> and <b>CLEAR_VARS</b> - These contain the names of
				589	well-defined template makefiles to include. Some examples are CLEAR_VARS
				590	and BUILD_HOST_PACKAGE.</li>
				591	<li>Any other name is fair-game for you to use in your Android.mk. However,
				592	remember that this is a non-recursive build system, so it is possible that
				593	your variable will be changed by another Android.mk included later, and be
				594	different when the commands for your rule / module are executed.</li>
				595	</ul>
				596	</p>
				597
				598	<h4>LOCAL_ASSET_FILES</h4>
				599	<p>In Android.mk files that <code>include $(BUILD_PACKAGE)</code> set this
				600	to the set of files you want built into your app. Usually:</p>
				601	<p><code>LOCAL_ASSET_FILES += $(call find-subdir-assets)</code></p>
				602	<p>This will probably change when we switch to ant for the apps' build
				603	system.</p>
				604
				605	<h4>LOCAL_CC</h4>
				606	<p>If you want to use a different C compiler for this module, set LOCAL_CC
				607	to the path to the compiler. If LOCAL_CC is blank, the appropriate default
				608	compiler is used.</p>
				609
				610	<h4>LOCAL_CXX</h4>
				611	<p>If you want to use a different C++ compiler for this module, set LOCAL_CXX
				612	to the path to the compiler. If LOCAL_CXX is blank, the appropriate default
				613	compiler is used.</p>
				614
				615	<h4>LOCAL_CFLAGS</h4>
				616	<p>If you have additional flags to pass into the C or C++ compiler, add
				617	them here. For example:</p>
				618	<p><code>LOCAL_CFLAGS += -DLIBUTILS_NATIVE=1</code></p>
				619
				620	<h4>LOCAL_CPPFLAGS</h4>
				621	<p>If you have additional flags to pass into <i>only</i> the C++ compiler, add
				622	them here. For example:</p>
				623	<p><code>LOCAL_CPPFLAGS += -ffriend-injection</code></p>
				624	<code>LOCAL_CPPFLAGS</code> is guaranteed to be after <code>LOCAL_CFLAGS</code>
				625	on the compile line, so you can use it to override flags listed in
				626	<code>LOCAL_CFLAGS</code>.
				627
				628	<h4>LOCAL_CPP_EXTENSION</h4>
				629	<p>If your C++ files end in something other than "<code>.cpp</code>",
				630	you can specify the custom extension here. For example:</p>
				631	<p><code>LOCAL_CPP_EXTENSION := .cc</code></p>
				632	Note that all C++ files for a given module must have the same
				633	extension; it is not currently possible to mix different extensions.
				634
				635	<h4>LOCAL_NO_DEFAULT_COMPILER_FLAGS</h4>
				636	<p>Normally, the compile line for C and C++ files includes global include
				637	paths and global cflags. If <code>LOCAL_NO_DEFAULT_COMPILER_FLAGS</code>
				638	is non-empty, none of the default includes or flags will be used when compiling
				639	C and C++ files in this module.
				640	<code>LOCAL_C_INCLUDES</code>, <code>LOCAL_CFLAGS</code>, and
				641	<code>LOCAL_CPPFLAGS</code> will still be used in this case, as will
				642	any <code>DEBUG_CFLAGS</code> that are defined for the module.
				643
				644	<h4>LOCAL_COPY_HEADERS</h4>
				645	<p class=warning>This will be going away.</p>
				646	<p>The set of files to copy to the install include tree. You must also
				647	supply <code>LOCAL_COPY_HEADERS_TO</code>.</p>
				648	<p>This is going away because copying headers messes up the error messages, and
				649	may lead to people editing those headers instead of the correct ones. It also
				650	makes it easier to do bad layering in the system, which we want to avoid. We
				651	also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any
				652	headers.</p>
				653
				654	<h4>LOCAL_COPY_HEADERS_TO</h4>
				655	<p class=warning>This will be going away.</p>
				656	<p>The directory within "include" to copy the headers listed in
				657	<code>LOCAL_COPY_HEADERS</code> to.</p>
				658	<p>This is going away because copying headers messes up the error messages, and
				659	may lead to people editing those headers instead of the correct ones. It also
				660	makes it easier to do bad layering in the system, which we want to avoid. We
				661	also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any
				662	headers.</p>
				663
				664	<h4>LOCAL_C_INCLUDES</h4>
				665	<p>Additional directories to instruct the C/C++ compilers to look for header
				666	files in. These paths are rooted at the top of the tree. Use
				667	<code>LOCAL_PATH</code> if you have subdirectories of your own that you
				668	want in the include paths. For example:</p>
				669	<p><code>
				670	LOCAL_C_INCLUDES += extlibs/zlib-1.2.3<br/>
				671	LOCAL_C_INCLUDES += $(LOCAL_PATH)/src
				672	</code></p>
				673	<p>You should not add subdirectories of include to
				674	<code>LOCAL_C_INCLUDES</code>, instead you should reference those files
				675	in the <code>#include</code> statement with their subdirectories. For
				676	example:</p>
				677	<p><code>#include <utils/KeyedVector.h></code><br/>
				678	not <code><s>#include <KeyedVector.h></s></code></p>
				679	<p>There are some components that are doing this wrong, and should be cleaned
				680	up.</p>
				681
				682	<h4>LOCAL_MODULE_TAGS</h4>
				683	<p>Set <code>LOCAL_MODULE_TAGS</code> to any number of whitespace-separated
				684	tags. If the tag list is empty or contains <code>droid</code>, the module
Thorsten Glaser	2213aab	2010-06-03 19:57:02 +0200	[diff] [blame]	685	will get installed as part of a <code>make droid</code>. Modules with the tag
				686	<code>shell_</code>$(TARGET_SHELL) will also be installed. Otherwise, it will
Joe Onorato	2303bf0	2008-10-23 19:37:58 -0700	[diff] [blame]	687	only get installed by running <code>make <your-module></code>
				688	or with the <code>make all</code> pseudotarget.</p>
				689
				690	<h4>LOCAL_REQUIRED_MODULES</h4>
				691	<p>Set <code>LOCAL_REQUIRED_MODULES</code> to any number of whitespace-separated
				692	module names, like "libblah" or "Email". If this module is installed, all
				693	of the modules that it requires will be installed as well. This can be
				694	used to, e.g., ensure that necessary shared libraries or providers are
				695	installed when a given app is installed.
				696
				697	<h4>LOCAL_FORCE_STATIC_EXECUTABLE</h4>
				698	<p>If your executable should be linked statically, set
				699	<code>LOCAL_FORCE_STATIC_EXECUTABLE:=true</code>. There is a very short
				700	list of libraries that we have in static form (currently only libc). This is
				701	really only used for executables in /sbin on the root filesystem.</p>
				702
				703	<h4>LOCAL_GENERATED_SOURCES</h4>
				704	<p>Files that you add to <code>LOCAL_GENERATED_SOURCES</code> will be
				705	automatically generated and then linked in when your module is built.
				706	See the <a href="#custom-tools">Custom Tools</a> template makefile for an
				707	example.</p>
				708
Brian Carlstrom	f184a0f	2010-02-01 11:13:32 -0800	[diff] [blame]	709	<h4>LOCAL_JAVACFLAGS</h4>
				710	<p>If you have additional flags to pass into the javac compiler, add
				711	them here. For example:</p>
				712	<p><code>LOCAL_JAVACFLAGS += -Xlint:deprecation</code></p>
				713
Joe Onorato	2303bf0	2008-10-23 19:37:58 -0700	[diff] [blame]	714	<h4>LOCAL_JAVA_LIBRARIES</h4>
				715	<p>When linking Java apps and libraries, <code>LOCAL_JAVA_LIBRARIES</code>
				716	specifies which sets of java classes to include. Currently there are
				717	two of these: <code>core</code> and <code>framework</code>.
				718	In most cases, it will look like this:</p>
				719	<p><code>LOCAL_JAVA_LIBRARIES := core framework</code></p>
				720	<p>Note that setting <code>LOCAL_JAVA_LIBRARIES</code> is not necessary
				721	(and is not allowed) when building an APK with
				722	"<code>include $(BUILD_PACKAGE)</code>". The appropriate libraries
				723	will be included automatically.</p>
				724
				725	<h4>LOCAL_LDFLAGS</h4>
				726	<p>You can pass additional flags to the linker by setting
				727	<code>LOCAL_LDFLAGS</code>. Keep in mind that the order of parameters is
				728	very important to ld, so test whatever you do on all platforms.</p>
				729
				730	<h4>LOCAL_LDLIBS</h4>
				731	<p><code>LOCAL_LDLIBS</code> allows you to specify additional libraries
				732	that are not part of the build for your executable or library. Specify
				733	the libraries you want in -lxxx format; they're passed directly to the
				734	link line. However, keep in mind that there will be no dependency generated
				735	for these libraries. It's most useful in simulator builds where you want
				736	to use a library preinstalled on the host. The linker (ld) is a particularly
				737	fussy beast, so it's sometimes necessary to pass other flags here if you're
				738	doing something sneaky. Some examples:</p>
				739	<p><code>LOCAL_LDLIBS += -lcurses -lpthread<br/>
				740	LOCAL_LDLIBS += -Wl,-z,origin
				741	</code></p>
				742
				743	<h4>LOCAL_NO_MANIFEST</h4>
				744	<p>If your package doesn't have a manifest (AndroidManifest.xml), then
				745	set <code>LOCAL_NO_MANIFEST:=true</code>. The common resources package
				746	does this.</p>
				747
				748	<h4>LOCAL_PACKAGE_NAME</h4>
				749	<p><code>LOCAL_PACKAGE_NAME</code> is the name of an app. For example,
				750	Dialer, Contacts, etc. This will probably change or go away when we switch
				751	to an ant-based build system for the apps.</p>
				752
				753	<h4>LOCAL_PATH</h4>
				754	<p>The directory your Android.mk file is in. You can set it by putting the
				755	following as the first line in your Android.mk:</p>
				756	<p><code>LOCAL_PATH := $(my-dir)</code></p>
				757	<p>The <code>my-dir</code> macro uses the
				758	<code><a href="http://www.gnu.org/software/make/manual/make.html#MAKEFILE_005fLIST-Variable">MAKEFILE_LIST</a></code>
				759	variable, so you must call it before you include any other makefiles. Also,
				760	consider that any subdirectories you inlcude might reset LOCAL_PATH, so do your
				761	own stuff before you include them. This also means that if you try to write
				762	several <code>include</code> lines that reference <code>LOCAL_PATH</code>,
				763	it won't work, because those included makefiles might reset LOCAL_PATH.
				764
				765	<h4>LOCAL_POST_PROCESS_COMMAND</h4>
				766	<p>For host executables, you can specify a command to run on the module
				767	after it's been linked. You might have to go through some contortions
				768	to get variables right because of early or late variable evaluation:</p>
				769	<p><code>module := $(HOST_OUT_EXECUTABLES)/$(LOCAL_MODULE)<br/>
				770	LOCAL_POST_PROCESS_COMMAND := /Developer/Tools/Rez -d __DARWIN__ -t APPL\<br/>
				771	-d __WXMAC__ -o $(module) Carbon.r
				772	</code></p>
				773
				774	<h4>LOCAL_PREBUILT_EXECUTABLES</h4>
				775	<p>When including $(BUILD_PREBUILT) or $(BUILD_HOST_PREBUILT), set these to
				776	executables that you want copied. They're located automatically into the
				777	right bin directory.</p>
				778
				779	<h4>LOCAL_PREBUILT_LIBS</h4>
				780	<p>When including $(BUILD_PREBUILT) or $(BUILD_HOST_PREBUILT), set these to
				781	libraries that you want copied. They're located automatically into the
				782	right lib directory.</p>
				783
				784	<h4>LOCAL_SHARED_LIBRARIES</h4>
				785	<p>These are the libraries you directly link against. You don't need to
				786	pass transitively included libraries. Specify the name without the suffix:</p>
				787	<p><code>LOCAL_SHARED_LIBRARIES := \<br/>
				788	libutils \<br/>
				789	libui \<br/>
				790	libaudio \<br/>
				791	libexpat \<br/>
				792	libsgl
				793	</code></p>
				794
				795	<h4>LOCAL_SRC_FILES</h4>
				796	<p>The build system looks at <code>LOCAL_SRC_FILES</code> to know what source
				797	files to compile -- .cpp .c .y .l .java. For lex and yacc files, it knows
				798	how to correctly do the intermediate .h and .c/.cpp files automatically. If
				799	the files are in a subdirectory of the one containing the Android.mk, prefix
				800	them with the directory name:</p>
				801	<p><code>LOCAL_SRC_FILES := \<br/>
				802	file1.cpp \<br/>
				803	dir/file2.cpp
				804	</code></p>
				805
				806	<h4>LOCAL_STATIC_LIBRARIES</h4>
				807	<p>These are the static libraries that you want to include in your module.
				808	Mostly, we use shared libraries, but there are a couple of places, like
				809	executables in sbin and host executables where we use static libraries instead.
				810	<p><code>LOCAL_STATIC_LIBRARIES := \<br/>
				811	libutils \<br/>
				812	libtinyxml
				813	</code></p>
				814
				815	<h4>LOCAL_MODULE</h4>
				816	<p><code>LOCAL_MODULE</code> is the name of what's supposed to be generated
				817	from your Android.mk. For exmample, for libkjs, the <code>LOCAL_MODULE</code>
				818	is "libkjs" (the build system adds the appropriate suffix -- .so .dylib .dll).
				819	For app modules, use <code>LOCAL_PACKAGE_NAME</code> instead of
				820	<code>LOCAL_MODULE</code>. We're planning on switching to ant for the apps,
				821	so this might become moot.</p>
				822
				823	<h4>LOCAL_MODULE_PATH</h4>
				824	<p>Instructs the build system to put the module somewhere other than what's
				825	normal for its type. If you override this, make sure you also set
				826	<code>LOCAL_UNSTRIPPED_PATH</code> if it's an executable or a shared library
				827	so the unstripped binary has somewhere to go. An error will occur if you forget
				828	to.</p>
				829	<p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p>
				830
				831	<h4>LOCAL_UNSTRIPPED_PATH</h4>
				832	<p>Instructs the build system to put the unstripped version of the module
				833	somewhere other than what's normal for its type. Usually, you override this
				834	because you overrode <code>LOCAL_MODULE_PATH</code> for an executable or a
				835	shared library. If you overrode <code>LOCAL_MODULE_PATH</code>, but not
				836	<code>LOCAL_UNSTRIPPED_PATH</code>, an error will occur.</p>
				837	<p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p>
				838
				839	<h4>LOCAL_WHOLE_STATIC_LIBRARIES</h4>
				840	<p>These are the static libraries that you want to include in your module without allowing
				841	the linker to remove dead code from them. This is mostly useful if you want to add a static library
				842	to a shared library and have the static library's content exposed from the shared library.
				843	<p><code>LOCAL_WHOLE_STATIC_LIBRARIES := \<br/>
				844	libsqlite3_android<br/>
				845	</code></p>
				846
				847	<h4>LOCAL_YACCFLAGS</h4>
				848	<p>Any flags to pass to invocations of yacc for your module. A known limitation
				849	here is that the flags will be the same for all invocations of YACC for your
				850	module. This can be fixed. If you ever need it to be, just ask.</p>
				851	<p><code>LOCAL_YACCFLAGS := -p kjsyy</code></p>
				852
				853
				854
				855	<h2>Implementation Details</h2>
				856
				857	<p>You should never have to touch anything in the config directory unless
				858	you're adding a new platform, new tools, or adding new features to the
				859	build system. In general, please consult with the build system owner(s)
				860	(<a href="mailto:android-build-team">android-build-team</a>) before you go
				861	mucking around in here. That said, here are some notes on what's going on
				862	under the hood.</p>
				863
				864	<h3>Environment Setup / buildspec.mk Versioning</h3>
				865	<p>In order to make easier for people when the build system changes, when
				866	it is necessary to make changes to buildspec.mk or to rerun the environment
				867	setup scripts, they contain a version number in the variable
				868	BUILD_ENV_SEQUENCE_NUMBER. If this variable does not match what the build
				869	system expects, it fails printing an error message explaining what happened.
				870	If you make a change that requires an update, you need to update two places
				871	so this message will be printed.
				872	<ul>
				873	<li>In config/envsetup.make, increment the
				874	CORRECT_BUILD_ENV_SEQUENCE_NUMBER definition.</li>
				875	<li>In buildspec.mk.default, update the BUILD_ENV_SEQUENCE_DUMBER
				876	definition to match the one in config/envsetup.make</li>
				877	</ul>
				878	The scripts automatically get the value from the build system, so they will
				879	trigger the warning as well.
				880	</p>
				881
				882	<h3>Additional makefile variables</h3>
				883	<p>You probably shouldn't use these variables. Please consult
				884	<a href="mailto:android-build-team">android-build-team</a> before using them.
				885	These are mostly there for workarounds for other issues, or things that aren't
				886	completely done right.</p>
				887
				888	<h4>LOCAL_ADDITIONAL_DEPENDENCIES</h4>
				889	<p>If your module needs to depend on anything else that
				890	isn't actually built in to it, you can add those make targets to
				891	<code>LOCAL_ADDITIONAL_DEPENDENCIES</code>. Usually this is a workaround
				892	for some other dependency that isn't created automatically.</p>
				893
				894	<h4>LOCAL_BUILT_MODULE</h4>
				895	<p>When a module is built, the module is created in an intermediate
				896	directory then copied to its final location. LOCAL_BUILT_MODULE is
				897	the full path to the intermediate file. See LOCAL_INSTALLED_MODULE
				898	for the path to the final installed location of the module.</p>
				899
				900	<h4>LOCAL_HOST</h4>
				901	<p>Set by the host_xxx.make includes to tell base_rules.make and the other
				902	includes that we're building for the host. Kenneth did this as part of
				903	openbinder, and I would like to clean it up so the rules, includes and
				904	definitions aren't duplicated for host and target.</p>
				905
				906	<h4>LOCAL_INSTALLED_MODULE</h4>
				907	<p>The fully qualified path name of the final location of the module.
				908	See LOCAL_BUILT_MODULE for the location of the intermediate file that
				909	the make rules should actually be constructing.</p>
				910
				911	<h4>LOCAL_REPLACE_VARS</h4>
				912	<p>Used in some stuff remaining from the openbinder for building scripts
				913	with particular values set,</p>
				914
				915	<h4>LOCAL_SCRIPTS</h4>
				916	<p>Used in some stuff remaining from the openbinder build system that we
				917	might find handy some day.</p>
				918
				919	<h4>LOCAL_MODULE_CLASS</h4>
				920	<p>Which kind of module this is. This variable is used to construct other
				921	variable names used to locate the modules. See base_rules.make and
				922	envsetup.make.</p>
				923
				924	<h4>LOCAL_MODULE_NAME</h4>
				925	<p>Set to the leaf name of the LOCAL_BUILT_MODULE. I'm not sure,
				926	but it looks like it's just used in the WHO_AM_I variable to identify
				927	in the pretty printing what's being built.</p>
				928
				929	<h4>LOCAL_MODULE_SUFFIX</h4>
				930	<p>The suffix that will be appended to <code>LOCAL_MODULE</code> to form
				931	<code>LOCAL_MODULE_NAME</code>. For example, .so, .a, .dylib.</p>
				932
				933	<h4>LOCAL_STRIP_MODULE</h4>
				934	<p>Calculated in base_rules.make to determine if this module should actually
				935	be stripped or not, based on whether <code>LOCAL_STRIPPABLE_MODULE</code>
				936	is set, and whether the combo is configured to ever strip modules. With
				937	Iliyan's stripping tool, this might change.</p>
				938
				939	<h4>LOCAL_STRIPPABLE_MODULE</h4>
				940	<p>Set by the include makefiles if that type of module is strippable.
				941	Executables and shared libraries are.</p>
				942
				943	<h4>LOCAL_SYSTEM_SHARED_LIBRARIES</h4>
				944	<p>Used while building the base libraries: libc, libm, libdl. Usually
				945	it should be set to "none," as it is in $(CLEAR_VARS). When building
				946	these libraries, it's set to the ones they link against. For example,
				947	libc, libstdc++ and libdl don't link against anything, and libm links against
				948	libc. Normally, when the value is none, these libraries are automatically
				949	linked in to executables and libraries, so you don't need to specify them
				950	manually.</p>
				951
				952
				953	</body>
				954	</html>