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22 <title>Android Build System</title>
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72 <h1><a name="My_Project_" />Android Build System</h1>
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>
80 <p><b>Contents</b></p>
81 <!-- this div expands out to a list of contents based on the H2 and H3 headings.
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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>
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.
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
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>
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
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>
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>
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
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>
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>
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>
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>
177 <h2>Nice to Have</h2>
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>
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>
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.
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>
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>
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>
211 <h3>Your first build</h3>
212 <p>The <a href="../building.html">Building</a> document describes how do do
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:
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>
231 <h3>Build flavors/types</h3>
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
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>.
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.
265 "<code>make user</code>"
267 This is the flavor intended to be the final release bits.
269 <li>Installs modules tagged with <code>user</code>.
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.
273 <li><code>ro.adb.secure=1</code>
274 <li><code>ro.secure=1</code>
275 <li><code>ro.debuggable=0</code>
276 <li><code>adb</code> is disabled by default.
281 <code>userdebug<code>
284 "<code>make userdebug</code>"
286 The same as <code>user</code>, except:
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.
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.
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>
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
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
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>
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>
366 <p>Use the <code>templates/apps</code> file.</p>
367 <p>This template is pretty self-explanitory. See the variables below for more
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>
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> or <code>LOCAL_MODULE_RELATIVE_PATH</code>. See
388 <a href="#moving-targets">Putting targets elsewhere</a>
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>
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>
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
412 <p>You need to put this after you have declared <code>LOCAL_PATH</code> and
413 <code>LOCAL_MODULE</code>, because the <code>$(local-generated-sources-dir)</code>
414 and <code>$(local-host-generated-sources-dir)</code> macros use these variables
415 to determine where to put the files.
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>
423 intermediates:= $(local-generated-sources-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)
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
437 intermediates:= $(local-generated-sources-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)
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>
451 intermediates:= $(local-generated-sources-dir)
452 GEN := $(addprefix $(intermediates)<font color=red>/kjs/, \
454 bool_object.lut.h \</font>
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 += $(GEN)
462 <h3><a name="platform-specific"/>Platform specific conditionals</h3>
463 <p>Sometimes you need to set flags specifically for different platforms. Here
464 is a list of which values the different build-system defined variables will be
465 set to and some examples.</p>
466 <table cellspacing=25>
468 <td valign=top align=center>
473 <td valign=top align=center>
474 <b>HOST_ARCH</b><br/>
478 <td valign=top align=center>
479 <b>HOST_BUILD_TYPE</b><br/>
485 <td valign=top align=center>
486 <b>TARGET_ARCH</b><br/>
494 <td valign=top align=center>
495 <b>TARGET_BUILD_TYPE</b><br/>
502 <p>There are also special variables to use instead of conditionals. Many of the
503 normal variables (LOCAL_SRC_FILES, LOCAL_CFLAGS, etc) can be conditionally added
504 to with _{arch} _{32|64}, and for the host, _{os}.</p>
506 <h4>Some Examples</h4>
507 <pre>ifeq ($(TARGET_BUILD_TYPE),release)
508 LOCAL_CFLAGS += -DNDEBUG=1
511 LOCAL_CFLAGS_arm += -DTARGET_IS_ARM
513 LOCAL_CFLAGS_64 += -DBIG_POINTER
516 # Use the futex based mutex and condition variable
517 # implementation from android-arm because it's shared mem safe
518 LOCAL_SRC_FILES_linux += futex_synchro.c
519 LOCAL_LDLIBS_linux += -lrt -ldl
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
526 build somewhere else, read this.</p>
527 <p>If you have modules that need to go in a subdirectory of their normal
528 location, 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
532 LOCAL_MODULE_RELATIVE_PATH := hw
534 <p>If you have modules that need to go in an entirely different location, for
535 example the root filesystem instead of in /system, add these lines to your
538 LOCAL_MODULE_PATH := $(TARGET_ROOT_OUT_SBIN)
539 LOCAL_UNSTRIPPED_PATH := $(TARGET_ROOT_OUT_SBIN_UNSTRIPPED)
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
544 the 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>
547 <p>Look in <code>core/envsetup.mk</code> for all of the variables defining
548 places to build things.</p>
549 <p>FYI: If you're installing an executable to /sbin, you probably also want to
550 set <code>LOCAL_FORCE_STATIC_EXCUTABLE := true</code> in your Android.mk, which
551 will force the linker to only accept static libraries.</p>
554 <h3>Android.mk variables</h3>
555 <p>These are the variables that you'll commonly see in Android.mk files, listed
557 <p>But first, a note on variable naming:
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.
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.
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.
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>
595 <h4>LOCAL_ASSET_FILES</h4>
596 <p>In Android.mk files that <code>include $(BUILD_PACKAGE)</code> set this
597 to 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
603 <p>If you want to use a different C compiler for this module, set LOCAL_CC
604 to the path to the compiler. If LOCAL_CC is blank, the appropriate default
605 compiler is used.</p>
608 <p>If you want to use a different C++ compiler for this module, set LOCAL_CXX
609 to the path to the compiler. If LOCAL_CXX is blank, the appropriate default
610 compiler is used.</p>
612 <h4>LOCAL_CFLAGS</h4>
613 <p>If you have additional flags to pass into the C or C++ compiler, add
614 them here. For example:</p>
615 <p><code>LOCAL_CFLAGS += -DLIBUTILS_NATIVE=1</code></p>
617 <h4>LOCAL_CPPFLAGS</h4>
618 <p>If you have additional flags to pass into <i>only</i> the C++ compiler, add
619 them 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>
622 on the compile line, so you can use it to override flags listed in
623 <code>LOCAL_CFLAGS</code>.
625 <h4>LOCAL_CPP_EXTENSION</h4>
626 <p>If your C++ files end in something other than "<code>.cpp</code>",
627 you can specify the custom extension here. For example:</p>
628 <p><code>LOCAL_CPP_EXTENSION := .cc</code></p>
629 Note that all C++ files for a given module must have the same
630 extension; it is not currently possible to mix different extensions.
632 <h4>LOCAL_NO_DEFAULT_COMPILER_FLAGS</h4>
633 <p>Normally, the compile line for C and C++ files includes global include
634 paths and global cflags. If <code>LOCAL_NO_DEFAULT_COMPILER_FLAGS</code>
635 is non-empty, none of the default includes or flags will be used when compiling
636 C 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
639 any <code>DEBUG_CFLAGS</code> that are defined for the module.
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
644 supply <code>LOCAL_COPY_HEADERS_TO</code>.</p>
645 <p>This is going away because copying headers messes up the error messages, and
646 may lead to people editing those headers instead of the correct ones. It also
647 makes it easier to do bad layering in the system, which we want to avoid. We
648 also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any
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
656 may lead to people editing those headers instead of the correct ones. It also
657 makes it easier to do bad layering in the system, which we want to avoid. We
658 also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any
661 <h4>LOCAL_C_INCLUDES</h4>
662 <p>Additional directories to instruct the C/C++ compilers to look for header
663 files 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
665 want in the include paths. For example:</p>
667 LOCAL_C_INCLUDES += extlibs/zlib-1.2.3<br/>
668 LOCAL_C_INCLUDES += $(LOCAL_PATH)/src
670 <p>You should not add subdirectories of include to
671 <code>LOCAL_C_INCLUDES</code>, instead you should reference those files
672 in the <code>#include</code> statement with their subdirectories. For
674 <p><code>#include <utils/KeyedVector.h></code><br/>
675 not <code><s>#include <KeyedVector.h></s></code></p>
676 <p>There are some components that are doing this wrong, and should be cleaned
679 <h4>LOCAL_MODULE_TAGS</h4>
680 <p>Set <code>LOCAL_MODULE_TAGS</code> to any number of whitespace-separated
681 tags. If the tag list is empty or contains <code>droid</code>, the module
682 will get installed as part of a <code>make droid</code>. Otherwise, it will
683 only get installed by running <code>make <your-module></code>
684 or with the <code>make all</code> pseudotarget.</p>
686 <h4>LOCAL_REQUIRED_MODULES</h4>
687 <p>Set <code>LOCAL_REQUIRED_MODULES</code> to any number of whitespace-separated
688 module names, like "libblah" or "Email". If this module is installed, all
689 of the modules that it requires will be installed as well. This can be
690 used to, e.g., ensure that necessary shared libraries or providers are
691 installed when a given app is installed.
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
696 list of libraries that we have in static form (currently only libc). This is
697 really only used for executables in /sbin on the root filesystem.</p>
699 <h4>LOCAL_GENERATED_SOURCES</h4>
700 <p>Files that you add to <code>LOCAL_GENERATED_SOURCES</code> will be
701 automatically generated and then linked in when your module is built.
702 See the <a href="#custom-tools">Custom Tools</a> template makefile for an
705 <h4>LOCAL_JAVACFLAGS</h4>
706 <p>If you have additional flags to pass into the javac compiler, add
707 them here. For example:</p>
708 <p><code>LOCAL_JAVACFLAGS += -Xlint:deprecation</code></p>
710 <h4>LOCAL_JAVA_LIBRARIES</h4>
711 <p>When linking Java apps and libraries, <code>LOCAL_JAVA_LIBRARIES</code>
712 specifies which sets of java classes to include. Currently there are
713 two of these: <code>core</code> and <code>framework</code>.
714 In 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
719 will be included automatically.</p>
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
724 very important to ld, so test whatever you do on all platforms.</p>
726 <h4>LOCAL_LDLIBS</h4>
727 <p><code>LOCAL_LDLIBS</code> allows you to specify additional libraries
728 that are not part of the build for your executable or library. Specify
729 the libraries you want in -lxxx format; they're passed directly to the
730 link line. However, keep in mind that there will be no dependency generated
731 for these libraries. It's most useful in simulator builds where you want
732 to use a library preinstalled on the host. The linker (ld) is a particularly
733 fussy beast, so it's sometimes necessary to pass other flags here if you're
734 doing something sneaky. Some examples:</p>
735 <p><code>LOCAL_LDLIBS += -lcurses -lpthread<br/>
736 LOCAL_LDLIBS += -Wl,-z,origin
739 <h4>LOCAL_NO_MANIFEST</h4>
740 <p>If your package doesn't have a manifest (AndroidManifest.xml), then
741 set <code>LOCAL_NO_MANIFEST:=true</code>. The common resources package
744 <h4>LOCAL_PACKAGE_NAME</h4>
745 <p><code>LOCAL_PACKAGE_NAME</code> is the name of an app. For example,
746 Dialer, Contacts, etc. This will probably change or go away when we switch
747 to an ant-based build system for the apps.</p>
750 <p>The directory your Android.mk file is in. You can set it by putting the
751 following 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>
755 variable, so you must call it before you include any other makefiles. Also,
756 consider that any subdirectories you inlcude might reset LOCAL_PATH, so do your
757 own stuff before you include them. This also means that if you try to write
758 several <code>include</code> lines that reference <code>LOCAL_PATH</code>,
759 it won't work, because those included makefiles might reset LOCAL_PATH.
761 <h4>LOCAL_POST_PROCESS_COMMAND</h4>
762 <p>For host executables, you can specify a command to run on the module
763 after it's been linked. You might have to go through some contortions
764 to get variables right because of early or late variable evaluation:</p>
765 <p><code>module := $(HOST_OUT_EXECUTABLES)/$(LOCAL_MODULE)<br/>
766 LOCAL_POST_PROCESS_COMMAND := /Developer/Tools/Rez -d __DARWIN__ -t APPL\<br/>
767 -d __WXMAC__ -o $(module) Carbon.r
770 <h4>LOCAL_PREBUILT_EXECUTABLES</h4>
771 <p>When including $(BUILD_MULTI_PREBUILT) or $(BUILD_HOST_PREBUILT), set these
772 to executables that you want copied. They're located automatically into the
773 right bin directory.</p>
775 <h4>LOCAL_PREBUILT_LIBS</h4>
776 <p>When including $(BUILD_MULTI_PREBUILT) or $(BUILD_HOST_PREBUILT), set these
777 to libraries that you want copied. They're located automatically into the
778 right lib directory.</p>
780 <h4>LOCAL_SHARED_LIBRARIES</h4>
781 <p>These are the libraries you directly link against. You don't need to
782 pass transitively included libraries. Specify the name without the suffix:</p>
783 <p><code>LOCAL_SHARED_LIBRARIES := \<br/>
784 libutils \<br/>
785 libui \<br/>
786 libaudio \<br/>
787 libexpat \<br/>
788 libsgl
791 <h4>LOCAL_SRC_FILES</h4>
792 <p>The build system looks at <code>LOCAL_SRC_FILES</code> to know what source
793 files to compile -- .cpp .c .y .l .java. For lex and yacc files, it knows
794 how to correctly do the intermediate .h and .c/.cpp files automatically. If
795 the files are in a subdirectory of the one containing the Android.mk, prefix
796 them with the directory name:</p>
797 <p><code>LOCAL_SRC_FILES := \<br/>
798 file1.cpp \<br/>
799 dir/file2.cpp
802 <h4>LOCAL_STATIC_LIBRARIES</h4>
803 <p>These are the static libraries that you want to include in your module.
804 Mostly, we use shared libraries, but there are a couple of places, like
805 executables in sbin and host executables where we use static libraries instead.
806 <p><code>LOCAL_STATIC_LIBRARIES := \<br/>
807 libutils \<br/>
808 libtinyxml
811 <h4>LOCAL_MODULE</h4>
812 <p><code>LOCAL_MODULE</code> is the name of what's supposed to be generated
813 from your Android.mk. For exmample, for libkjs, the <code>LOCAL_MODULE</code>
814 is "libkjs" (the build system adds the appropriate suffix -- .so .dylib .dll).
815 For 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,
817 so this might become moot.</p>
819 <h4>LOCAL_MODULE_PATH</h4>
820 <p>Instructs the build system to put the module somewhere other than what's
821 normal 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
823 so the unstripped binary has somewhere to go. An error will occur if you forget
825 <p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p>
827 <h4>LOCAL_MODULE_RELATIVE_PATH</h4>
828 <p>Instructs the build system to put the module in a subdirectory under the
829 directory that is normal for its type. If you set this you do not need to
830 set <code>LOCAL_UNSTRIPPED_PATH</code>, the unstripped binaries will also use
831 the relative path.</p>
832 <p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p>
834 <h4>LOCAL_MODULE_HOST_OS</h4>
835 <p>This specifies which OSes are supported by this host module. It is not used
836 for target builds. The accepted values here are combinations of
837 <code>linux</code>, <code>darwin</code>, and <code>windows</code>. By default,
838 linux and darwin(MacOS) are considered to be supported. If a module should
839 build under windows, you must specify windows, and any others to be supported.
841 <p><code>LOCAL_MODULE_HOST_OS := linux<br/>
842 LOCAL_MODULE_HOST_OS := darwin linux windows</code></p>
844 <h4>LOCAL_UNSTRIPPED_PATH</h4>
845 <p>Instructs the build system to put the unstripped version of the module
846 somewhere other than what's normal for its type. Usually, you override this
847 because you overrode <code>LOCAL_MODULE_PATH</code> for an executable or a
848 shared 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>
852 <h4>LOCAL_WHOLE_STATIC_LIBRARIES</h4>
853 <p>These are the static libraries that you want to include in your module without allowing
854 the linker to remove dead code from them. This is mostly useful if you want to add a static library
855 to a shared library and have the static library's content exposed from the shared library.
856 <p><code>LOCAL_WHOLE_STATIC_LIBRARIES := \<br/>
857 libsqlite3_android<br/>
860 <h4>LOCAL_YACCFLAGS</h4>
861 <p>Any flags to pass to invocations of yacc for your module. A known limitation
862 here is that the flags will be the same for all invocations of YACC for your
863 module. This can be fixed. If you ever need it to be, just ask.</p>
864 <p><code>LOCAL_YACCFLAGS := -p kjsyy</code></p>
868 <h2>Implementation Details</h2>
870 <p>You should never have to touch anything in the config directory unless
871 you're adding a new platform, new tools, or adding new features to the
872 build 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
874 mucking around in here. That said, here are some notes on what's going on
877 <h3>Environment Setup / buildspec.mk Versioning</h3>
878 <p>In order to make easier for people when the build system changes, when
879 it is necessary to make changes to buildspec.mk or to rerun the environment
880 setup scripts, they contain a version number in the variable
881 BUILD_ENV_SEQUENCE_NUMBER. If this variable does not match what the build
882 system expects, it fails printing an error message explaining what happened.
883 If you make a change that requires an update, you need to update two places
884 so this message will be printed.
886 <li>In core/envsetup.mk, increment the
887 CORRECT_BUILD_ENV_SEQUENCE_NUMBER definition.</li>
888 <li>In buildspec.mk.default, update the BUILD_ENV_SEQUENCE_DUMBER
889 definition to match the one in core/envsetup.mk</li>
891 The scripts automatically get the value from the build system, so they will
892 trigger the warning as well.
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.
898 These are mostly there for workarounds for other issues, or things that aren't
899 completely done right.</p>
901 <h4>LOCAL_ADDITIONAL_DEPENDENCIES</h4>
902 <p>If your module needs to depend on anything else that
903 isn't actually built in to it, you can add those make targets to
904 <code>LOCAL_ADDITIONAL_DEPENDENCIES</code>. Usually this is a workaround
905 for some other dependency that isn't created automatically.</p>
907 <h4>LOCAL_BUILT_MODULE</h4>
908 <p class=warning>This should not be used, since multiple binaries are now
909 created from a single module defintiion.</p>
910 <p>When a module is built, the module is created in an intermediate
911 directory then copied to its final location. LOCAL_BUILT_MODULE is
912 the full path to the intermediate file. See LOCAL_INSTALLED_MODULE
913 for the path to the final installed location of the module.</p>
915 <h4>LOCAL_IS_HOST_MODULE</h4>
916 <p>Set by the host_xxx.mk includes to tell base_rules.mk and the other
917 includes that we're building for the host.</p>
919 <h4>LOCAL_INSTALLED_MODULE</h4>
920 <p class=warning>This should not be used, since multiple binaries are now
921 created from a single module defintiion.</p>
922 <p>The fully qualified path name of the final location of the module.
923 See LOCAL_BUILT_MODULE for the location of the intermediate file that
924 the make rules should actually be constructing.</p>
926 <h4>LOCAL_MODULE_CLASS</h4>
927 <p>Which kind of module this is. This variable is used to construct other
928 variable names used to locate the modules. See base_rules.mk and
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>
935 <h4>LOCAL_STRIP_MODULE</h4>
936 <p>If set to true (the default), the binary will be stripped and a debug
937 link will be set up so that GDB will still work. If set to no_debuglink,
938 the binary will be stripped, but no debug link will be added. If set to
939 keep_symbols, it will strip the debug information, but keep the symbol table.
940 Any other value will prevent stripping.</p>
942 <h4>LOCAL_SYSTEM_SHARED_LIBRARIES</h4>
943 <p>Used while building the base libraries: libc, libm, libdl. Usually
944 it should be set to "none," as it is in $(CLEAR_VARS). When building
945 these libraries, it's set to the ones they link against. For example,
946 libc, libstdc++ and libdl don't link against anything, and libm links against
947 libc. Normally, when the value is none, these libraries are automatically
948 linked in to executables and libraries, so you don't need to specify them