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71
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>Wildcard source files</h3>
151<p>Wildcarding source file will be discouraged.  It may be useful in some
152scenarios.  The default <code>$(wildcard *)</code> will not work due to the
153current directory being set to the root of the build tree.<p>
154
155<h3>Multiple targets in one directory</h3>
156<p>It will be possible to generate more than one target from a given
157subdirectory.  For example, libutils generates a shared library for the target
158and a static library for the host.</p>
159
160<h3>Makefile fragments for modules</h3>
161<p><b>Android.mk</b> is the standard name for the makefile fragments that
162control the building of a given module.  Only the top directory should
163have a file named "Makefile".</p>
164
165<h3>Use shared libraries</h3>
166<p>Currently, the simulator is not built to use shared libraries.  This should
167be fixed, and now is a good time to do it.  This implies getting shared
168libraries to work on Mac OS.</p>
169
170
171<h2>Nice to Have</h2>
172
173<p>These things would be nice to have, and this is a good place to record them,
174however these are not promises.</p>
175
176<h3>Simultaneous Builds</h3>
177<p>The hope is to be able to do two builds for different combos in the same
178tree at the same time, but this is a stretch goal, not a requirement.
179Doing two builds in the same tree, not at the same time must work.  (update:
180it's looking like we'll get the two builds at the same time working)</p>
181
182<h3>Deleting headers (or other dependecies)</h3>
183<p>Problems can arise if you delete a header file that is referenced in
184".d" files.  The easy way to deal with this is "make clean".  There
185should be a better way to handle it. (from fadden)</p>
186<p>One way of solving this is introducing a dependency on the directory.  The
187problem is that this can create extra dependecies and slow down the build.
188It's a tradeoff.</p>
189
190<h3>Multiple builds</h3>
191<p>General way to perform builds across the set of known platforms.  This
192would make it easy to perform multiple platform builds when testing a
193change, and allow a wide-scale "make clean".  Right now the buildspec.mk
194or environment variables need to be updated before each build. (from fadden)</p>
195
196<h3>Aftermarket Locales and Carrier</h3>
197<p>We will eventually need to add support for creating locales and carrier
198customizations to the SDK, but that will not be addressed right now.</p>
199
200
201<h2><a id="usage"/>Usage</h2>
202<p>You've read (or scrolled past) all of the motivations for this build system,
203and you want to know how to use it.  This is the place.</p>
204
205<h3>Your first build</h3>
206<p>The <a href="../building.html">Building</a> document describes how do do
207builds.</p>
208
209<h3>build/envsetup.sh functions</h3>
210If you source the file build/envsetup.sh into your bash environment,
211<code>. build/envsetup.sh</code>you'll get a few helpful shell functions:
212
213<ul>
214<li><b>printconfig</b> - Prints the current configuration as set by the
215lunch and choosecombo commands.</li>
216<li><b>m</b> - Runs <code>make</code> from the top of the tree.  This is
217useful because you can run make from within subdirectories.  If you have the
218<code>TOP</code> environment variable set, it uses that.  If you don't, it looks
219up the tree from the current directory, trying to find the top of the tree.</li>
220<li><b>croot</b> - <code>cd</code> to the top of the tree.</li>
221<li><b>sgrep</b> - grep for the regex you provide in all .c, .cpp, .h, .java,
222and .xml files below the current directory.</li>
223</ul>
224
225<h3>Build flavors/types</h3>
226<p>
227When building for a particular product, it's often useful to have minor
228variations on what is ultimately the final release build.  These are the
229currently-defined "flavors" or "types" (we need to settle on a real name
230for these).
231</p>
232
233<table border=1>
234<tr>
235    <td>
236        <code>eng<code>
237    </td>
238    <td>
239        This is the default flavor. A plain "<code>make</code>" is the
240        same as "<code>make eng</code>".  <code>droid</code> is an alias
241        for <code>eng</code>.
242        <ul>
243        <li>Installs modules tagged with: <code>eng</code>, <code>debug</code>,
244            <code>user</code>, and/or <code>development</code>.
245        <li>Installs non-APK modules that have no tags specified.
246        <li>Installs APKs according to the product definition files, in
247            addition to tagged APKs.
248        <li><code>ro.secure=0</code>
249        <li><code>ro.debuggable=1</code>
250        <li><code>ro.kernel.android.checkjni=1</code>
251        <li><code>adb</code> is enabled by default.
252    </td>
253</tr>
254<tr>
255    <td>
256        <code>user<code>
257    </td>
258    <td>
259        "<code>make user</code>"
260        <p>
261        This is the flavor intended to be the final release bits.
262        <ul>
263        <li>Installs modules tagged with <code>user</code>.
264        <li>Installs non-APK modules that have no tags specified.
265        <li>Installs APKs according to the product definition files; tags
266            are ignored for APK modules.
267        <li><code>ro.adb.secure=1</code>
268        <li><code>ro.secure=1</code>
269        <li><code>ro.debuggable=0</code>
270        <li><code>adb</code> is disabled by default.
271    </td>
272</tr>
273<tr>
274    <td>
275        <code>userdebug<code>
276    </td>
277    <td>
278        "<code>make userdebug</code>"
279        <p>
280        The same as <code>user</code>, except:
281        <ul>
282        <li>Also installs modules tagged with <code>debug</code>.
283        <li><code>ro.debuggable=1</code>
284        <li><code>adb</code> is enabled by default.
285    </td>
286</tr>
287</table>
288
289<p>
290If you build one flavor and then want to build another, you should run
291"<code>make installclean</code>" between the two makes to guarantee that
292you don't pick up files installed by the previous flavor.  "<code>make
293clean</code>" will also suffice, but it takes a lot longer.
294</p>
295
296
297<h3>More pseudotargets</h3>
298<p>Sometimes you want to just build one thing.  The following pseudotargets are
299there for your convenience:</p>
300
301<ul>
302<li><b>droid</b> - <code>make droid</code> is the normal build.  This target
303is here because the default target has to have a name.</li>
304<li><b>all</b> - <code>make all</code> builds everything <code>make
305droid</code> does, plus everything whose <code>LOCAL_MODULE_TAGS</code> do not
306include the "droid" tag.  The build server runs this to make sure
307that everything that is in the tree and has an Android.mk builds.</li>
308<li><b>clean-$(LOCAL_MODULE)</b> and <b>clean-$(LOCAL_PACKAGE_NAME)</b> -
309Let you selectively clean one target.  For example, you can type
310<code>make clean-libutils</code> and it will delete libutils.so and all of the
311intermediate files, or you can type <code>make clean-Home</code> and it will
312clean just the Home app.</li>
313<li><b>clean</b> - <code>make clean</code> deletes all of the output and
314intermediate files for this configuration.  This is the same as <code>rm -rf
315out/&lt;configuration&gt;/</code></li>
316<li><b>clobber</b> - <code>make clobber</code> deletes all of the output
317and intermediate files for all configurations.  This is the same as
318<code>rm -rf out/</code>.</li>
319<li><b>dataclean</b> - <code>make dataclean</code> deletes contents of the data
320directory inside the current combo directory.  This is especially useful on the
321simulator and emulator, where the persistent data remains present between
322builds.</li>
323<li><b>LOCAL_MODULE</b> - Anything you specify as a <code>LOCAL_MODULE</code>
324in an Android.mk is made into a pseudotarget.  For example, <code>make
325runtime</code> might be shorthand for <code>make
326out/linux-x86-debug/system/bin/runtime</code> (which would work), and
327<code>make libkjs</code> might be shorthand for <code>make
328out/linux-x86-debug/system/lib/libkjs.so</code> (which would also work).</li>
329<li><b>targets</b> - <code>make targets</code> will print a list of all of
330the LOCAL_MODULE names you can make.</li>
331</ul>
332
333<h3><a name="templates"/>How to add another component to the build - Android.mk templates</h3>
334<p>You have a new library, a new app, or a new executable.  For each of the
335common types of modules, there is a corresponding file in the templates
336directory.  It will usually be enough to copy one of these, and fill in your
337own values.  Some of the more esoteric values are not included in the
338templates, but are instead just documented here, as is the documentation
339on using custom tools to generate files.</p>
340<p>Mostly, you can just look for the TODO comments in the templates and do
341what it says.  Please remember to delete the TODO comments when you're done
342to keep the files clean.  The templates have minimal documentation in them,
343because they're going to be copied, and when that gets stale, the copies just
344won't get updated.  So read on...</p>
345
346<h4>Apps</h4>
347<p>Use the <code>templates/apps</code> file.</p>
348<p>This template is pretty self-explanitory.  See the variables below for more
349details.</p>
350
351<h4>Java Libraries</h4>
352<p>Use the <code>templates/java_library</code> file.</p>
353<p>The interesting thing here is the value of LOCAL_MODULE, which becomes
354the name of the jar file.  (Actually right now, we're not making jar files yet,
355just directories of .class files,  but the directory is named according to
356what you put in LOCAL_MODULE).  This name will be what goes in the
357LOCAL_JAVA_LIBRARIES variable in modules that depend on your java library.</p>
358
359<h4>C/C++ Executables</h4>
360<p>Use the <code>templates/executable</code> file, or the
361<code>templates/executable_host</code> file.</p>
362<p>This template has a couple extra options that you usually don't need.
363Please delete the ones you don't need, and remove the TODO comments.  It makes
364the rest of them easier to read, and you can always refer back to the templates
365if you need them again later.</p>
366<p>By default, on the target these are built into /system/bin, and on the
367host, they're built into <combo>/host/bin.  These can be overridden by setting
368<code>LOCAL_MODULE_PATH</code> or <code>LOCAL_MODULE_RELATIVE_PATH</code>.  See
369<a href="#moving-targets">Putting targets elsewhere</a>
370for more.</p>
371
372<h4>Shared Libraries</h4>
373<p>Use the <code>templates/shared_library</code> file, or the
374<code>templates/shared_library_host</code> file.</p>
375<p>Remember that on the target, we use shared libraries, and on the host,
376we use static libraries, since executable size isn't as big an issue, and it
377simplifies distribution in the SDK.</p>
378
379<h4>Static Libraries</h4>
380<p>Use the <code>templates/static_library</code> file, or the
381<code>templates/static_library_host</code> file.</p>
382<p>Remember that on the target, we use shared libraries, and on the host,
383we use static libraries, since executable size isn't as big an issue, and it
384simplifies distribution in the SDK.</p>
385
386<h4><a name="custom-tools"/>Using Custom Tools</h4>
387<p>If you have a tool that generates source files for you, it's possible
388to have the build system get the dependencies correct for it.  Here are
389a couple of examples.  <code>$@</code> is the make built-in variable for
390"the current target." The <font color=red>red</font> parts are the parts you'll
391need to change.</p>
392
393<p>You need to put this after you have declared <code>LOCAL_PATH</code> and
394<code>LOCAL_MODULE</code>, because the <code>$(local-generated-sources-dir)</code>
395and <code>$(local-host-generated-sources-dir)</code> macros use these variables
396to determine where to put the files.
397
398<h5>Example 1</h5>
399<p>Here, there is one generated file, called
400chartables.c, which doesn't depend on anything.  And is built by the tool
401built to $(HOST_OUT_EXECUTABLES)/dftables.  Note on the second to last line
402that a dependency is created on the tool.</p>
403<pre>
404intermediates:= $(local-generated-sources-dir)
405GEN := $(intermediates)/<font color=red>chartables.c</font>
406$(GEN): PRIVATE_CUSTOM_TOOL = <font color=red>$(HOST_OUT_EXECUTABLES)/dftables $@</font>
407$(GEN): <font color=red>$(HOST_OUT_EXECUTABLES)/dftables</font>
408	$(transform-generated-source)
409LOCAL_GENERATED_SOURCES += $(GEN)
410</pre>
411
412<h5>Example 2</h5>
413<p>Here as a hypothetical example, we use use cat as if it were to transform
414a file.  Pretend that it does something useful.  Note how we use a
415target-specific variable called PRIVATE_INPUT_FILE to store the name of the
416input file.</p>
417<pre>
418intermediates:= $(local-generated-sources-dir)
419GEN := $(intermediates)/<font color=red>file.c</font>
420$(GEN): PRIVATE_INPUT_FILE := $(LOCAL_PATH)/<font color=red>input.file</font>
421$(GEN): PRIVATE_CUSTOM_TOOL = <font color=red>cat $(PRIVATE_INPUT_FILE) &gt; $@</font>
422$(GEN): <font color=red>$(LOCAL_PATH)/input.file</font>
423	$(transform-generated-source)
424LOCAL_GENERATED_SOURCES += $(GEN)
425</pre>
426
427<h5>Example 3</h5>
428<p>If you have several files that are all similar in
429name, and use the same tool, you can combine them.  (here the *.lut.h files are
430the generated ones, and the *.cpp files are the input files)</p>
431<pre>
432intermediates:= $(local-generated-sources-dir)
433GEN := $(addprefix $(intermediates)<font color=red>/kjs/, \
434            array_object.lut.h \
435            bool_object.lut.h \</font>
436        )
437$(GEN): PRIVATE_CUSTOM_TOOL = <font color=red>perl libs/WebKitLib/WebKit/JavaScriptCore/kjs/create_hash_table $< -i > $@</font>
438$(GEN): $(intermediates)/<font color=red>%.lut.h</font> : $(LOCAL_PATH)/<font color=red>%.cpp</font>
439	$(transform-generated-source)
440LOCAL_GENERATED_SOURCES += $(GEN)
441</pre>
442
443<h3><a name="platform-specific"/>Platform specific conditionals</h3>
444<p>Sometimes you need to set flags specifically for different platforms.  Here
445is a list of which values the different build-system defined variables will be
446set to and some examples.</p>
447<table cellspacing=25>
448<tr>
449    <td valign=top align=center>
450        <b>HOST_OS</b><br/>
451        linux<br/>
452        darwin
453    </td>
454    <td valign=top align=center>
455        <b>HOST_ARCH</b><br/>
456        x86<br/>
457        x86_64
458    </td>
459    <td valign=top align=center>
460        <b>HOST_BUILD_TYPE</b><br/>
461        release<br/>
462        debug
463    </td>
464</tr>
465<tr>
466    <td valign=top align=center>
467        <b>TARGET_ARCH</b><br/>
468        arm<br/>
469        arm64<br/>
470        mips<br/>
471        mips64<br/>
472        x86<br/>
473        x86_64
474    </td>
475    <td valign=top align=center>
476        <b>TARGET_BUILD_TYPE</b><br/>
477        release<br/>
478        debug
479    </td>
480</tr>
481</table>
482
483<p>There are also special variables to use instead of conditionals. Many of the
484normal variables (LOCAL_SRC_FILES, LOCAL_CFLAGS, etc) can be conditionally added
485to with _{arch} _{32|64}, and for the host, _{os}.</p>
486
487<h4>Some Examples</h4>
488<pre>ifeq ($(TARGET_BUILD_TYPE),release)
489LOCAL_CFLAGS += -DNDEBUG=1
490endif
491
492LOCAL_CFLAGS_arm += -DTARGET_IS_ARM
493
494LOCAL_CFLAGS_64 += -DBIG_POINTER
495
496# from libutils
497# Use the futex based mutex and condition variable
498# implementation from android-arm because it's shared mem safe
499LOCAL_SRC_FILES_linux += futex_synchro.c
500LOCAL_LDLIBS_linux += -lrt -ldl
501
502</pre>
503
504
505<h3><a name="moving-modules"/>Putting modules elsewhere</h3>
506<p>If you have modules that normally go somewhere, and you need to have them
507build somewhere else, read this.</p>
508<p>If you have modules that need to go in a subdirectory of their normal
509location, for example HAL modules that need to go in /system/lib/hw or
510/vendor/lib/hw, set LOCAL_MODULE_RELATIVE_PATH in your Android.mk, for
511example:</p>
512<pre>
513LOCAL_MODULE_RELATIVE_PATH := hw
514</pre>
515<p>If you have modules that need to go in an entirely different location, for
516example the root filesystem instead of in /system, add these lines to your
517Android.mk:</p>
518<pre>
519LOCAL_MODULE_PATH := $(TARGET_ROOT_OUT)
520LOCAL_UNSTRIPPED_PATH := $(TARGET_ROOT_OUT_UNSTRIPPED)
521</pre>
522<p>For executables and libraries, you need to specify a
523<code>LOCAL_UNSTRIPPED_PATH</code> location if you specified a
524<code>LOCAL_MODULE_PATH</code>, because on target builds, we keep
525the unstripped executables so GDB can find the symbols.
526<code>LOCAL_UNSTRIPPED_PATH</code> is not necessary if you only specified
527<code>LOCAL_MODULE_RELATIVE_PATH</code>.</p>
528<p>Look in <code>core/envsetup.mk</code> for all of the variables defining
529places to build things.</p>
530
531
532<h3>Android.mk variables</h3>
533<p>These are the variables that you'll commonly see in Android.mk files, listed
534alphabetically.</p>
535<p>But first, a note on variable naming:
536<ul>
537    <li><b>LOCAL_</b> - These variables are set per-module.  They are cleared
538    by the <code>include $(CLEAR_VARS)</code> line, so you can rely on them
539    being empty after including that file.  Most of the variables you'll use
540    in most modules are LOCAL_ variables.</li>
541    <li><b>PRIVATE_</b> - These variables are make-target-specific variables.  That
542    means they're only usable within the commands for that module.  It also
543    means that they're unlikely to change behind your back from modules that
544    are included after yours.  This
545    <a href="http://www.gnu.org/software/make/manual/make.html#Target_002dspecific">link to the make documentation</a>
546    describes more about target-specific variables.  Please note that there
547    are a couple of these laying around the tree that aren't prefixed with
548    PRIVATE_.  It is safe, and they will be fixed as they are discovered.
549    Sorry for the confusion.</li>
550    <li><b>INTERNAL_</b> - These variables are critical to functioning of
551    the build system, so you shouldn't create variables named like this, and
552    you probably shouldn't be messing with these variables in your makefiles.
553    </li>
554    <li><b>HOST_</b> and <b>TARGET_</b> - These contain the directories
555    and definitions that are specific to either the host or the target builds.
556    Do not set variables that start with HOST_ or TARGET_ in your makefiles.
557    </li>
558    <li><b>HOST_CROSS_</b> - These contain the directories and definitions that
559    are specific to cross-building host binaries. The common case is building
560    windows host tools on linux. Do not set variables that start with
561    HOST_CROSS_ in your makefiles.
562    </li>
563    <li><b>BUILD_</b> and <b>CLEAR_VARS</b> - These contain the names of
564    well-defined template makefiles to include.  Some examples are CLEAR_VARS
565    and BUILD_HOST_PACKAGE.</li>
566    <li>Any other name is fair-game for you to use in your Android.mk.  However,
567    remember that this is a non-recursive build system, so it is possible that
568    your variable will be changed by another Android.mk included later, and be
569    different when the commands for your rule / module are executed.</li>
570</ul>
571</p>
572
573<h4>LOCAL_ANNOTATION_PROCESSORS</h4>
574<p>Set this to a list of modules built with <code>BUILD_HOST_JAVA_LIBRARY</code>
575to have their jars passed to javac with -processorpath for use as annotation
576processors.</p>
577
578<h4>LOCAL_ANNOTATION_PROCESSOR_CLASSES</h4>
579<p>Set this to a list of classes to be passed to javac as -processor arguments.
580This list is would be unnecessary, as javac will autodetect annotation processor
581classes, except that the Grok tool that is used on the Android source code
582does not autodetect them and requires listing them manually.</p>
583
584<h4>LOCAL_ASSET_FILES</h4>
585<p>In Android.mk files that <code>include $(BUILD_PACKAGE)</code> set this
586to the set of files you want built into your app.  Usually:</p>
587<p><code>LOCAL_ASSET_FILES += $(call find-subdir-assets)</code></p>
588<p>This will probably change when we switch to ant for the apps' build
589system.</p>
590
591<h4>LOCAL_CC</h4>
592<p>If you want to use a different C compiler for this module, set LOCAL_CC
593to the path to the compiler.  If LOCAL_CC is blank, the appropriate default
594compiler is used.</p>
595
596<h4>LOCAL_CXX</h4>
597<p>If you want to use a different C++ compiler for this module, set LOCAL_CXX
598to the path to the compiler.  If LOCAL_CXX is blank, the appropriate default
599compiler is used.</p>
600
601<h4>LOCAL_CFLAGS</h4>
602<p>If you have additional flags to pass into the C or C++ compiler, add
603them here.  For example:</p>
604<p><code>LOCAL_CFLAGS += -DLIBUTILS_NATIVE=1</code></p>
605
606<h4>LOCAL_CPPFLAGS</h4>
607<p>If you have additional flags to pass into <i>only</i> the C++ compiler, add
608them here.  For example:</p>
609<p><code>LOCAL_CPPFLAGS += -ffriend-injection</code></p>
610<code>LOCAL_CPPFLAGS</code> is guaranteed to be after <code>LOCAL_CFLAGS</code>
611on the compile line, so you can use it to override flags listed in
612<code>LOCAL_CFLAGS</code>.
613
614<h4>LOCAL_CPP_EXTENSION</h4>
615<p>If your C++ files end in something other than "<code>.cpp</code>",
616you can specify the custom extension here.  For example:</p>
617<p><code>LOCAL_CPP_EXTENSION := .cc</code></p>
618Note that all C++ files for a given module must have the same
619extension; it is not currently possible to mix different extensions.
620
621<h4>LOCAL_NO_DEFAULT_COMPILER_FLAGS</h4>
622<p>Normally, the compile line for C and C++ files includes global include
623paths and global cflags.  If <code>LOCAL_NO_DEFAULT_COMPILER_FLAGS</code>
624is non-empty, none of the default includes or flags will be used when compiling
625C and C++ files in this module.
626<code>LOCAL_C_INCLUDES</code>, <code>LOCAL_CFLAGS</code>, and
627<code>LOCAL_CPPFLAGS</code> will still be used in this case, as will
628any <code>DEBUG_CFLAGS</code> that are defined for the module.
629
630<h4>LOCAL_COPY_HEADERS</h4>
631<p class=warning>This will be going away.</p>
632<p>The set of files to copy to the install include tree.  You must also
633supply <code>LOCAL_COPY_HEADERS_TO</code>.</p>
634<p>This is going away because copying headers messes up the error messages, and
635may lead to people editing those headers instead of the correct ones.  It also
636makes it easier to do bad layering in the system, which we want to avoid.  We
637also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any
638headers.</p>
639
640<h4>LOCAL_COPY_HEADERS_TO</h4>
641<p class=warning>This will be going away.</p>
642<p>The directory within "include" to copy the headers listed in
643<code>LOCAL_COPY_HEADERS</code> to.</p>
644<p>This is going away because copying headers messes up the error messages, and
645may lead to people editing those headers instead of the correct ones.  It also
646makes it easier to do bad layering in the system, which we want to avoid.  We
647also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any
648headers.</p>
649
650<h4>LOCAL_C_INCLUDES</h4>
651<p>Additional directories to instruct the C/C++ compilers to look for header
652files in.  These paths are rooted at the top of the tree.  Use
653<code>LOCAL_PATH</code> if you have subdirectories of your own that you
654want in the include paths.  For example:</p>
655<p><code>
656LOCAL_C_INCLUDES += extlibs/zlib-1.2.3<br/>
657LOCAL_C_INCLUDES += $(LOCAL_PATH)/src
658</code></p>
659<p>You should not add subdirectories of include to
660<code>LOCAL_C_INCLUDES</code>, instead you should reference those files
661in the <code>#include</code> statement with their subdirectories.  For
662example:</p>
663<p><code>#include &lt;utils/KeyedVector.h&gt;</code><br/>
664not <code><s>#include &lt;KeyedVector.h&gt;</s></code></p>
665<p>There are some components that are doing this wrong, and should be cleaned
666up.</p>
667
668<h4>LOCAL_MODULE_TAGS</h4>
669<p>Set <code>LOCAL_MODULE_TAGS</code> to any number of whitespace-separated
670tags.  If the tag list is empty or contains <code>droid</code>, the module
671will get installed as part of a <code>make droid</code>.  Otherwise, it will
672only get installed by running <code>make &lt;your-module&gt;</code>
673or with the <code>make all</code> pseudotarget.</p>
674
675<h4>LOCAL_REQUIRED_MODULES</h4>
676<p>Set <code>LOCAL_REQUIRED_MODULES</code> to any number of whitespace-separated
677module names, like "libblah" or "Email".  If this module is installed, all
678of the modules that it requires will be installed as well.  This can be
679used to, e.g., ensure that necessary shared libraries or providers are
680installed when a given app is installed.
681
682<h4>LOCAL_FORCE_STATIC_EXECUTABLE</h4>
683<p>If your executable should be linked statically, set
684<code>LOCAL_FORCE_STATIC_EXECUTABLE:=true</code>.  There is a very short
685list of libraries that we have in static form (currently only libc).</p>
686
687<h4>LOCAL_GENERATED_SOURCES</h4>
688<p>Files that you add to <code>LOCAL_GENERATED_SOURCES</code> will be
689automatically generated and then linked in when your module is built.
690See the <a href="#custom-tools">Custom Tools</a> template makefile for an
691example.</p>
692
693<h4>LOCAL_JAVACFLAGS</h4>
694<p>If you have additional flags to pass into the javac compiler, add
695them here.  For example:</p>
696<p><code>LOCAL_JAVACFLAGS += -Xlint:deprecation</code></p>
697
698<h4>LOCAL_ERROR_PRONE_FLAGS</h4>
699<p>If you have additional flags to pass into the error prone compiler, add
700them here.  For example:</p>
701<p><code>LOCAL_ERROR_PRONE_FLAGS += -Xep:ClassCanBeStatic:ERROR</code></p>
702
703<h4>LOCAL_JAVA_LIBRARIES</h4>
704<p>When linking Java apps and libraries, <code>LOCAL_JAVA_LIBRARIES</code>
705specifies which sets of java classes to include.  Currently there are
706two of these: <code>core</code> and <code>framework</code>.
707In most cases, it will look like this:</p>
708<p><code>LOCAL_JAVA_LIBRARIES := core framework</code></p>
709<p>Note that setting <code>LOCAL_JAVA_LIBRARIES</code> is not necessary
710(and is not allowed) when building an APK with
711"<code>include $(BUILD_PACKAGE)</code>".  The appropriate libraries
712will be included automatically.</p>
713
714<h4>LOCAL_LDFLAGS</h4>
715<p>You can pass additional flags to the linker by setting
716<code>LOCAL_LDFLAGS</code>.  Keep in mind that the order of parameters is
717very important to ld, so test whatever you do on all platforms.</p>
718
719<h4>LOCAL_LDLIBS</h4>
720<p><code>LOCAL_LDLIBS</code> allows you to specify additional libraries
721that are not part of the build for your executable or library.  Specify
722the libraries you want in -lxxx format; they're passed directly to the
723link line.  However, keep in mind that there will be no dependency generated
724for these libraries.  It's most useful in simulator builds where you want
725to use a library preinstalled on the host.  The linker (ld) is a particularly
726fussy beast, so it's sometimes necessary to pass other flags here if you're
727doing something sneaky. Some examples:</p>
728<p><code>LOCAL_LDLIBS += -lcurses -lpthread<br/>
729LOCAL_LDLIBS += -Wl,-z,origin
730</code></p>
731
732<h4>LOCAL_NO_MANIFEST</h4>
733<p>If your package doesn't have a manifest (AndroidManifest.xml), then
734set <code>LOCAL_NO_MANIFEST:=true</code>.  The common resources package
735does this.</p>
736
737<h4>LOCAL_PACKAGE_NAME</h4>
738<p><code>LOCAL_PACKAGE_NAME</code> is the name of an app.  For example,
739Dialer, Contacts, etc.  This will probably change or go away when we switch
740to an ant-based build system for the apps.</p>
741
742<h4>LOCAL_PATCH_MODULE (experimental option)</h4>
743<p>As of January 2018, you almost certainly don't need this option, so please
744ask and only use it if you understand what you're doing. This feature is
745experimental and may go away in future.</p>
746<p>
747When compiling language level 9+ .java code in packages that are part of a
748a system module, <code>LOCAL_PATCH_MODULE</code> names the module that your
749sources and dependencies should be patched into. The Android runtime currently
750(Jan 2018) doesn't implement the JEP 261 module system so this option is only
751supported at compile time. It should only be needed to compile tests in packages
752that exist in libcore and which are inconvenient to move elsewhere.
753</p>
754
755<h4>LOCAL_PATH</h4>
756<p>The directory your Android.mk file is in. You can set it by putting the
757following as the first line in your Android.mk:</p>
758<p><code>LOCAL_PATH := $(my-dir)</code></p>
759<p>The <code>my-dir</code> macro uses the
760<code><a href="http://www.gnu.org/software/make/manual/make.html#MAKEFILE_005fLIST-Variable">MAKEFILE_LIST</a></code>
761variable, so you must call it before you include any other makefiles.  Also,
762consider that any subdirectories you inlcude might reset LOCAL_PATH, so do your
763own stuff before you include them.  This also means that if you try to write
764several <code>include</code> lines that reference <code>LOCAL_PATH</code>,
765it won't work, because those included makefiles might reset LOCAL_PATH.
766
767<h4>LOCAL_POST_PROCESS_COMMAND</h4>
768<p>For host executables, you can specify a command to run on the module
769after it's been linked.  You might have to go through some contortions
770to get variables right because of early or late variable evaluation:</p>
771<p><code>module := $(HOST_OUT_EXECUTABLES)/$(LOCAL_MODULE)<br/>
772LOCAL_POST_PROCESS_COMMAND := /Developer/Tools/Rez -d __DARWIN__ -t APPL\<br/>
773&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;-d __WXMAC__ -o $(module) Carbon.r
774</code></p>
775
776<h4>LOCAL_PREBUILT_EXECUTABLES</h4>
777<p>When including $(BUILD_MULTI_PREBUILT) or $(BUILD_HOST_PREBUILT), set these
778to executables that you want copied.  They're located automatically into the
779right bin directory.</p>
780
781<h4>LOCAL_PREBUILT_LIBS</h4>
782<p>When including $(BUILD_MULTI_PREBUILT) or $(BUILD_HOST_PREBUILT), set these
783to libraries that you want copied.  They're located automatically into the
784right lib directory.</p>
785
786<h4>LOCAL_SHARED_LIBRARIES</h4>
787<p>These are the libraries you directly link against.  You don't need to
788pass transitively included libraries.  Specify the name without the suffix:</p>
789<p><code>LOCAL_SHARED_LIBRARIES := \<br/>
790	&nbsp;&nbsp;&nbsp;&nbsp;libutils \<br/>
791	&nbsp;&nbsp;&nbsp;&nbsp;libui \<br/>
792	&nbsp;&nbsp;&nbsp;&nbsp;libaudio \<br/>
793	&nbsp;&nbsp;&nbsp;&nbsp;libexpat \<br/>
794	&nbsp;&nbsp;&nbsp;&nbsp;libsgl
795</code></p>
796
797<h4>LOCAL_SRC_FILES</h4>
798<p>The build system looks at <code>LOCAL_SRC_FILES</code> to know what source
799files to compile -- .cpp .c .y .l .java.  For lex and yacc files, it knows
800how to correctly do the intermediate .h and .c/.cpp files automatically.  If
801the files are in a subdirectory of the one containing the Android.mk, prefix
802them with the directory name:</p>
803<p><code>LOCAL_SRC_FILES := \<br/>
804	&nbsp;&nbsp;&nbsp;&nbsp;file1.cpp \<br/>
805	&nbsp;&nbsp;&nbsp;&nbsp;dir/file2.cpp
806</code></p>
807
808<h4>LOCAL_STATIC_LIBRARIES</h4>
809<p>These are the static libraries that you want to include in your module.
810Mostly, we use shared libraries, but there are a couple of places, like
811host executables where we use static libraries instead.
812<p><code>LOCAL_STATIC_LIBRARIES := \<br/>
813	&nbsp;&nbsp;&nbsp;&nbsp;libutils \<br/>
814	&nbsp;&nbsp;&nbsp;&nbsp;libtinyxml
815</code></p>
816
817<h4>LOCAL_MODULE</h4>
818<p><code>LOCAL_MODULE</code> is the name of what's supposed to be generated
819from your Android.mk.  For exmample, for libkjs, the <code>LOCAL_MODULE</code>
820is "libkjs" (the build system adds the appropriate suffix -- .so .dylib .dll).
821For app modules, use <code>LOCAL_PACKAGE_NAME</code> instead of
822<code>LOCAL_MODULE</code>.  We're planning on switching to ant for the apps,
823so this might become moot.</p>
824
825<h4>LOCAL_MODULE_PATH</h4>
826<p>Instructs the build system to put the module somewhere other than what's
827normal for its type.  If you override this, make sure you also set
828<code>LOCAL_UNSTRIPPED_PATH</code> if it's an executable or a shared library
829so the unstripped binary has somewhere to go.  An error will occur if you forget
830to.</p>
831<p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p>
832
833<h4>LOCAL_MODULE_RELATIVE_PATH</h4>
834<p>Instructs the build system to put the module in a subdirectory under the
835directory that is normal for its type.  If you set this you do not need to
836set <code>LOCAL_UNSTRIPPED_PATH</code>, the unstripped binaries will also use
837the relative path.</p>
838<p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p>
839
840<h4>LOCAL_MODULE_HOST_OS</h4>
841<p>This specifies which OSes are supported by this host module. It is not used
842for target builds. The accepted values here are combinations of
843<code>linux</code>, <code>darwin</code>, and <code>windows</code>. By default,
844linux and darwin(MacOS) are considered to be supported. If a module should
845build under windows, you must specify windows, and any others to be supported.
846Some examples:</p>
847<p><code>LOCAL_MODULE_HOST_OS := linux<br/>
848LOCAL_MODULE_HOST_OS := darwin linux windows</code></p>
849
850<h4>LOCAL_UNSTRIPPED_PATH</h4>
851<p>Instructs the build system to put the unstripped version of the module
852somewhere other than what's normal for its type.  Usually, you override this
853because you overrode <code>LOCAL_MODULE_PATH</code> for an executable or a
854shared library.  If you overrode <code>LOCAL_MODULE_PATH</code>, but not
855<code>LOCAL_UNSTRIPPED_PATH</code>, an error will occur.</p>
856<p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p>
857
858<h4>LOCAL_WHOLE_STATIC_LIBRARIES</h4>
859<p>These are the static libraries that you want to include in your module without allowing
860the linker to remove dead code from them. This is mostly useful if you want to add a static library
861to a shared library and have the static library's content exposed from the shared library.
862<p><code>LOCAL_WHOLE_STATIC_LIBRARIES := \<br/>
863	&nbsp;&nbsp;&nbsp;&nbsp;libsqlite3_android<br/>
864</code></p>
865
866<h4>LOCAL_YACCFLAGS</h4>
867<p>Any flags to pass to invocations of yacc for your module.  A known limitation
868here is that the flags will be the same for all invocations of YACC for your
869module.  This can be fixed.  If you ever need it to be, just ask.</p>
870<p><code>LOCAL_YACCFLAGS := -p kjsyy</code></p>
871
872
873
874<h2>Implementation Details</h2>
875
876<p>You should never have to touch anything in the config directory unless
877you're adding a new platform, new tools, or adding new features to the
878build system.  In general, please consult with the build system owner(s)
879(<a href="mailto:android-build-team">android-build-team</a>) before you go
880mucking around in here.  That said, here are some notes on what's going on
881under the hood.</p>
882
883<h3>Environment Setup / buildspec.mk Versioning</h3>
884<p>In order to make easier for people when the build system changes, when
885it is necessary to make changes to buildspec.mk or to rerun the environment
886setup scripts, they contain a version number in the variable
887BUILD_ENV_SEQUENCE_NUMBER.  If this variable does not match what the build
888system expects, it fails printing an error message explaining what happened.
889If you make a change that requires an update, you need to update two places
890so this message will be printed.
891<ul>
892    <li>In core/envsetup.mk, increment the
893        CORRECT_BUILD_ENV_SEQUENCE_NUMBER definition.</li>
894    <li>In buildspec.mk.default, update the BUILD_ENV_SEQUENCE_DUMBER
895        definition to match the one in core/envsetup.mk</li>
896</ul>
897The scripts automatically get the value from the build system, so they will
898trigger the warning as well.
899</p>
900
901<h3>Additional makefile variables</h3>
902<p>You probably shouldn't use these variables.  Please consult
903<a href="mailto:android-build-team">android-build-team</a> before using them.
904These are mostly there for workarounds for other issues, or things that aren't
905completely done right.</p>
906
907<h4>LOCAL_ADDITIONAL_DEPENDENCIES</h4>
908<p>If your module needs to depend on anything else that
909isn't actually built in to it, you can add those make targets to
910<code>LOCAL_ADDITIONAL_DEPENDENCIES</code>.  Usually this is a workaround
911for some other dependency that isn't created automatically.</p>
912
913<h4>LOCAL_BUILT_MODULE</h4>
914<p class=warning>This should not be used, since multiple binaries are now
915created from a single module defintiion.</p>
916<p>When a module is built, the module is created in an intermediate
917directory then copied to its final location.  LOCAL_BUILT_MODULE is
918the full path to the intermediate file.  See LOCAL_INSTALLED_MODULE
919for the path to the final installed location of the module.</p>
920
921<h4>LOCAL_IS_HOST_MODULE</h4>
922<p>Set by the host_xxx.mk includes to tell base_rules.mk and the other
923includes that we're building for the host.</p>
924
925<h4>LOCAL_INSTALLED_MODULE</h4>
926<p class=warning>This should not be used, since multiple binaries are now
927created from a single module defintiion.</p>
928<p>The fully qualified path name of the final location of the module.
929See LOCAL_BUILT_MODULE for the location of the intermediate file that
930the make rules should actually be constructing.</p>
931
932<h4>LOCAL_MODULE_CLASS</h4>
933<p>Which kind of module this is.  This variable is used to construct other
934variable names used to locate the modules.  See base_rules.mk and
935envsetup.mk.</p>
936
937<h4>LOCAL_MODULE_SUFFIX</h4>
938<p>The suffix that will be appended to <code>LOCAL_MODULE</code> to form
939<code>LOCAL_MODULE_NAME</code>.  For example, .so, .a, .dylib.</p>
940
941<h4>LOCAL_STRIP_MODULE</h4>
942<p>If set to true (the default), the binary will be stripped and a debug
943link will be set up so that GDB will still work. If set to no_debuglink,
944the binary will be stripped, but no debug link will be added. If set to
945keep_symbols, it will strip the debug information, but keep the symbol table.
946Any other value will prevent stripping.</p>
947
948<h4>LOCAL_SYSTEM_SHARED_LIBRARIES</h4>
949<p>Used while building the base libraries: libc, libm, libdl.  Usually
950it should be set to "none," as it is in $(CLEAR_VARS).  When building
951these libraries, it's set to the ones they link against.  For example,
952libc, libstdc++ and libdl don't link against anything, and libm links against
953libc.  Normally, when the value is none, these libraries are automatically
954linked in to executables and libraries, so you don't need to specify them
955manually.</p>
956
957
958</body>
959</html>
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