1<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 2 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3 4<html xmlns="http://www.w3.org/1999/xhtml"> 5 6<!-- 7 A lot of people read this document template. 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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/<configuration>/</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) > $@</font> 422$(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="unbundled-build"/>Unbundled build</h3> 444<p>Unbundled build has several meanings by the context. 445Let me explain the meaning by the flags related to "unbundled build"</p> 446<h4>TARGET_BUILD_UNBUNDLED</h4> 447<p>The source tree might not have the full platform sources. It is always set if 448<code>TARGET_BUILD_APPS</code> or <code>TARGET_BUILD_UNBUNDLED_IMAGE</code> is set.</p> 449<h4>TARGET_BUILD_USE_PREBUILT_SDKS</h4> 450<p>It is an internal flag. If it is set, prebuilt SDKs are used, even if a module's 451<code>LOCAL_SDK_VERSION</code> is <code>current</code> (including <code>system_current</code>, 452<code>core_current</code>, and so on). If it is unset, build current SDKs, 453and use them as usual.</p> 454<h4>DISABLE_PREOPT</h4> 455<p>It is an internal flag as well. If it is set, dexpreopt is disabled. 456It is always set if <code>TARGET_BUILD_APPS</code> or <code>TARGET_BUILD_UNBUNDLED_IMAGE</code> is set, 457because dexpreopt tightly depends on the platform.</p> 458<h4>TARGET_BUILD_APPS</h4> 459<p>Build the apps that can be distributed outside the platform, so it turns on 460<code>TARGET_BUILD_UNBUNDLED</code> and <code>DISABLE_PREOPT</code>. 461Also, it turns on <code>TARGET_BUILD_USE_PREBUILT_SDKS</code>, unless 462<code>UNBUNDLED_BUILD_SDKS_FROM_SOURCE</code> is set.</p> 463<h4>TARGET_BUILD_UNBUNDLED_IMAGE</h4> 464<p>It is similar to <code>TARGET_BUILD_APPS</code>, but its target is an unbundled partition 465(such as the vendor partition). Accordingly, it sets <code>TARGET_BUILD_UNBUNDLED</code> and <code>DISABLE_PREOPT</code>. 466We can call the partition unbundled, because the partition can be distributed outside the platform. 467And also, it turns on <code>TARGET_BUILD_USE_PREBUILT_SDKS</code>, unless 468<code>UNBUNDLED_BUILD_SDKS_FROM_SOURCE</code> is set.</p> 469 470<h3><a name="platform-specific"/>Platform specific conditionals</h3> 471<p>Sometimes you need to set flags specifically for different platforms. Here 472is a list of which values the different build-system defined variables will be 473set to and some examples.</p> 474<table cellspacing=25> 475<tr> 476 <td valign=top align=center> 477 <b>HOST_OS</b><br/> 478 linux<br/> 479 darwin 480 </td> 481 <td valign=top align=center> 482 <b>HOST_ARCH</b><br/> 483 x86<br/> 484 x86_64 485 </td> 486 <td valign=top align=center> 487 <b>HOST_BUILD_TYPE</b><br/> 488 release<br/> 489 debug 490 </td> 491</tr> 492<tr> 493 <td valign=top align=center> 494 <b>TARGET_ARCH</b><br/> 495 arm<br/> 496 arm64<br/> 497 x86<br/> 498 x86_64 499 </td> 500 <td valign=top align=center> 501 <b>TARGET_BUILD_TYPE</b><br/> 502 release<br/> 503 debug 504 </td> 505</tr> 506</table> 507 508<p>There are also special variables to use instead of conditionals. Many of the 509normal variables (LOCAL_SRC_FILES, LOCAL_CFLAGS, etc) can be conditionally added 510to with _{arch} _{32|64}, and for the host, _{os}.</p> 511 512<h4>Some Examples</h4> 513<pre>ifeq ($(TARGET_BUILD_TYPE),release) 514LOCAL_CFLAGS += -DNDEBUG=1 515endif 516 517LOCAL_CFLAGS_arm += -DTARGET_IS_ARM 518 519LOCAL_CFLAGS_64 += -DBIG_POINTER 520 521# from libutils 522# Use the futex based mutex and condition variable 523# implementation from android-arm because it's shared mem safe 524LOCAL_SRC_FILES_linux += futex_synchro.c 525LOCAL_LDLIBS_linux += -lrt -ldl 526 527</pre> 528 529 530<h3><a name="moving-modules"/>Putting modules elsewhere</h3> 531<p>If you have modules that normally go somewhere, and you need to have them 532build somewhere else, read this.</p> 533<p>If you have modules that need to go in a subdirectory of their normal 534location, for example HAL modules that need to go in /system/lib/hw or 535/vendor/lib/hw, set LOCAL_MODULE_RELATIVE_PATH in your Android.mk, for 536example:</p> 537<pre> 538LOCAL_MODULE_RELATIVE_PATH := hw 539</pre> 540<p>If you have modules that need to go in an entirely different location, for 541example the root filesystem instead of in /system, add these lines to your 542Android.mk:</p> 543<pre> 544LOCAL_MODULE_PATH := $(TARGET_ROOT_OUT) 545LOCAL_UNSTRIPPED_PATH := $(TARGET_ROOT_OUT_UNSTRIPPED) 546</pre> 547<p>For executables and libraries, you need to specify a 548<code>LOCAL_UNSTRIPPED_PATH</code> location if you specified a 549<code>LOCAL_MODULE_PATH</code>, because on target builds, we keep 550the unstripped executables so GDB can find the symbols. 551<code>LOCAL_UNSTRIPPED_PATH</code> is not necessary if you only specified 552<code>LOCAL_MODULE_RELATIVE_PATH</code>.</p> 553<p>Look in <code>core/envsetup.mk</code> for all of the variables defining 554places to build things.</p> 555 556 557<h3>Android.mk variables</h3> 558<p>These are the variables that you'll commonly see in Android.mk files, listed 559alphabetically.</p> 560<p>But first, a note on variable naming: 561<ul> 562 <li><b>LOCAL_</b> - These variables are set per-module. They are cleared 563 by the <code>include $(CLEAR_VARS)</code> line, so you can rely on them 564 being empty after including that file. Most of the variables you'll use 565 in most modules are LOCAL_ variables.</li> 566 <li><b>PRIVATE_</b> - These variables are make-target-specific variables. That 567 means they're only usable within the commands for that module. It also 568 means that they're unlikely to change behind your back from modules that 569 are included after yours. This 570 <a href="http://www.gnu.org/software/make/manual/make.html#Target_002dspecific">link to the make documentation</a> 571 describes more about target-specific variables. Please note that there 572 are a couple of these laying around the tree that aren't prefixed with 573 PRIVATE_. It is safe, and they will be fixed as they are discovered. 574 Sorry for the confusion.</li> 575 <li><b>INTERNAL_</b> - These variables are critical to functioning of 576 the build system, so you shouldn't create variables named like this, and 577 you probably shouldn't be messing with these variables in your makefiles. 578 </li> 579 <li><b>HOST_</b> and <b>TARGET_</b> - These contain the directories 580 and definitions that are specific to either the host or the target builds. 581 Do not set variables that start with HOST_ or TARGET_ in your makefiles. 582 </li> 583 <li><b>HOST_CROSS_</b> - These contain the directories and definitions that 584 are specific to cross-building host binaries. The common case is building 585 windows host tools on linux. Do not set variables that start with 586 HOST_CROSS_ 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_ANNOTATION_PROCESSORS</h4> 599<p>Set this to a list of modules built with <code>BUILD_HOST_JAVA_LIBRARY</code> 600to have their jars passed to javac with -processorpath for use as annotation 601processors.</p> 602 603<h4>LOCAL_ANNOTATION_PROCESSOR_CLASSES</h4> 604<p>Set this to a list of classes to be passed to javac as -processor arguments. 605This list is would be unnecessary, as javac will autodetect annotation processor 606classes, except that the Grok tool that is used on the Android source code 607does not autodetect them and requires listing them manually.</p> 608 609<h4>LOCAL_ASSET_FILES</h4> 610<p>In Android.mk files that <code>include $(BUILD_PACKAGE)</code> set this 611to the set of files you want built into your app. Usually:</p> 612<p><code>LOCAL_ASSET_FILES += $(call find-subdir-assets)</code></p> 613<p>This will probably change when we switch to ant for the apps' build 614system.</p> 615 616<h4>LOCAL_CC</h4> 617<p>If you want to use a different C compiler for this module, set LOCAL_CC 618to the path to the compiler. If LOCAL_CC is blank, the appropriate default 619compiler is used.</p> 620 621<h4>LOCAL_CXX</h4> 622<p>If you want to use a different C++ compiler for this module, set LOCAL_CXX 623to the path to the compiler. If LOCAL_CXX is blank, the appropriate default 624compiler is used.</p> 625 626<h4>LOCAL_CFLAGS</h4> 627<p>If you have additional flags to pass into the C or C++ compiler, add 628them here. For example:</p> 629<p><code>LOCAL_CFLAGS += -DLIBUTILS_NATIVE=1</code></p> 630 631<h4>LOCAL_CPPFLAGS</h4> 632<p>If you have additional flags to pass into <i>only</i> the C++ compiler, add 633them here. For example:</p> 634<p><code>LOCAL_CPPFLAGS += -ffriend-injection</code></p> 635<code>LOCAL_CPPFLAGS</code> is guaranteed to be after <code>LOCAL_CFLAGS</code> 636on the compile line, so you can use it to override flags listed in 637<code>LOCAL_CFLAGS</code>. 638 639<h4>LOCAL_CPP_EXTENSION</h4> 640<p>If your C++ files end in something other than "<code>.cpp</code>", 641you can specify the custom extension here. For example:</p> 642<p><code>LOCAL_CPP_EXTENSION := .cc</code></p> 643Note that all C++ files for a given module must have the same 644extension; it is not currently possible to mix different extensions. 645 646<h4>LOCAL_NO_DEFAULT_COMPILER_FLAGS</h4> 647<p>Normally, the compile line for C and C++ files includes global include 648paths and global cflags. If <code>LOCAL_NO_DEFAULT_COMPILER_FLAGS</code> 649is non-empty, none of the default includes or flags will be used when compiling 650C and C++ files in this module. 651<code>LOCAL_C_INCLUDES</code>, <code>LOCAL_CFLAGS</code>, and 652<code>LOCAL_CPPFLAGS</code> will still be used in this case, as will 653any <code>DEBUG_CFLAGS</code> that are defined for the module. 654 655<h4>LOCAL_COPY_HEADERS</h4> 656<p class=warning>This will be going away.</p> 657<p>The set of files to copy to the install include tree. You must also 658supply <code>LOCAL_COPY_HEADERS_TO</code>.</p> 659<p>This is going away because copying headers messes up the error messages, and 660may lead to people editing those headers instead of the correct ones. It also 661makes it easier to do bad layering in the system, which we want to avoid. We 662also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any 663headers.</p> 664 665<h4>LOCAL_COPY_HEADERS_TO</h4> 666<p class=warning>This will be going away.</p> 667<p>The directory within "include" to copy the headers listed in 668<code>LOCAL_COPY_HEADERS</code> to.</p> 669<p>This is going away because copying headers messes up the error messages, and 670may lead to people editing those headers instead of the correct ones. It also 671makes it easier to do bad layering in the system, which we want to avoid. We 672also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any 673headers.</p> 674 675<h4>LOCAL_C_INCLUDES</h4> 676<p>Additional directories to instruct the C/C++ compilers to look for header 677files in. These paths are rooted at the top of the tree. Use 678<code>LOCAL_PATH</code> if you have subdirectories of your own that you 679want in the include paths. For example:</p> 680<p><code> 681LOCAL_C_INCLUDES += extlibs/zlib-1.2.3<br/> 682LOCAL_C_INCLUDES += $(LOCAL_PATH)/src 683</code></p> 684<p>You should not add subdirectories of include to 685<code>LOCAL_C_INCLUDES</code>, instead you should reference those files 686in the <code>#include</code> statement with their subdirectories. For 687example:</p> 688<p><code>#include <utils/KeyedVector.h></code><br/> 689not <code><s>#include <KeyedVector.h></s></code></p> 690<p>There are some components that are doing this wrong, and should be cleaned 691up.</p> 692 693<h4>LOCAL_MODULE_TAGS</h4> 694<p>Set <code>LOCAL_MODULE_TAGS</code> to any number of whitespace-separated 695tags. If the tag list is empty or contains <code>droid</code>, the module 696will get installed as part of a <code>make droid</code>. Otherwise, it will 697only get installed by running <code>make <your-module></code> 698or with the <code>make all</code> pseudotarget.</p> 699 700<h4>LOCAL_REQUIRED_MODULES</h4> 701<p>Set <code>LOCAL_REQUIRED_MODULES</code> to any number of whitespace-separated 702module names, like "libblah" or "Email". If this module is installed, all 703of the modules that it requires will be installed as well. This can be 704used to, e.g., ensure that necessary shared libraries or providers are 705installed when a given app is installed. 706 707<h4>LOCAL_FORCE_STATIC_EXECUTABLE</h4> 708<p>If your executable should be linked statically, set 709<code>LOCAL_FORCE_STATIC_EXECUTABLE:=true</code>. There is a very short 710list of libraries that we have in static form (currently only libc).</p> 711 712<h4>LOCAL_GENERATED_SOURCES</h4> 713<p>Files that you add to <code>LOCAL_GENERATED_SOURCES</code> will be 714automatically generated and then linked in when your module is built. 715See the <a href="#custom-tools">Custom Tools</a> template makefile for an 716example.</p> 717 718<h4>LOCAL_JAVACFLAGS</h4> 719<p>If you have additional flags to pass into the javac compiler, add 720them here. For example:</p> 721<p><code>LOCAL_JAVACFLAGS += -Xlint:deprecation</code></p> 722 723<h4>LOCAL_ERROR_PRONE_FLAGS</h4> 724<p>If you have additional flags to pass into the error prone compiler, add 725them here. For example:</p> 726<p><code>LOCAL_ERROR_PRONE_FLAGS += -Xep:ClassCanBeStatic:ERROR</code></p> 727 728<h4>LOCAL_JAVA_LIBRARIES</h4> 729<p>When linking Java apps and libraries, <code>LOCAL_JAVA_LIBRARIES</code> 730specifies which sets of java classes to include. Currently there are 731two of these: <code>core</code> and <code>framework</code>. 732In most cases, it will look like this:</p> 733<p><code>LOCAL_JAVA_LIBRARIES := core framework</code></p> 734<p>Note that setting <code>LOCAL_JAVA_LIBRARIES</code> is not necessary 735(and is not allowed) when building an APK with 736"<code>include $(BUILD_PACKAGE)</code>". The appropriate libraries 737will be included automatically.</p> 738 739<h4>LOCAL_LDFLAGS</h4> 740<p>You can pass additional flags to the linker by setting 741<code>LOCAL_LDFLAGS</code>. Keep in mind that the order of parameters is 742very important to ld, so test whatever you do on all platforms.</p> 743 744<h4>LOCAL_LDLIBS</h4> 745<p><code>LOCAL_LDLIBS</code> allows you to specify additional libraries 746that are not part of the build for your executable or library. Specify 747the libraries you want in -lxxx format; they're passed directly to the 748link line. However, keep in mind that there will be no dependency generated 749for these libraries. It's most useful in simulator builds where you want 750to use a library preinstalled on the host. The linker (ld) is a particularly 751fussy beast, so it's sometimes necessary to pass other flags here if you're 752doing something sneaky. Some examples:</p> 753<p><code>LOCAL_LDLIBS += -lcurses -lpthread<br/> 754LOCAL_LDLIBS += -Wl,-z,origin 755</code></p> 756 757<h4>LOCAL_NO_MANIFEST</h4> 758<p>If your package doesn't have a manifest (AndroidManifest.xml), then 759set <code>LOCAL_NO_MANIFEST:=true</code>. The common resources package 760does this.</p> 761 762<h4>LOCAL_PACKAGE_NAME</h4> 763<p><code>LOCAL_PACKAGE_NAME</code> is the name of an app. For example, 764Dialer, Contacts, etc. This will probably change or go away when we switch 765to an ant-based build system for the apps.</p> 766 767<h4>LOCAL_PATCH_MODULE (experimental option)</h4> 768<p>As of January 2018, you almost certainly don't need this option, so please 769ask and only use it if you understand what you're doing. This feature is 770experimental and may go away in future.</p> 771<p> 772When compiling language level 9+ .java code in packages that are part of a 773a system module, <code>LOCAL_PATCH_MODULE</code> names the module that your 774sources and dependencies should be patched into. The Android runtime currently 775(Jan 2018) doesn't implement the JEP 261 module system so this option is only 776supported at compile time. It should only be needed to compile tests in packages 777that exist in libcore and which are inconvenient to move elsewhere. 778</p> 779 780<h4>LOCAL_PATH</h4> 781<p>The directory your Android.mk file is in. You can set it by putting the 782following as the first line in your Android.mk:</p> 783<p><code>LOCAL_PATH := $(my-dir)</code></p> 784<p>The <code>my-dir</code> macro uses the 785<code><a href="http://www.gnu.org/software/make/manual/make.html#MAKEFILE_005fLIST-Variable">MAKEFILE_LIST</a></code> 786variable, so you must call it before you include any other makefiles. Also, 787consider that any subdirectories you inlcude might reset LOCAL_PATH, so do your 788own stuff before you include them. This also means that if you try to write 789several <code>include</code> lines that reference <code>LOCAL_PATH</code>, 790it won't work, because those included makefiles might reset LOCAL_PATH. 791 792<h4>LOCAL_POST_PROCESS_COMMAND</h4> 793<p>For host executables, you can specify a command to run on the module 794after it's been linked. You might have to go through some contortions 795to get variables right because of early or late variable evaluation:</p> 796<p><code>module := $(HOST_OUT_EXECUTABLES)/$(LOCAL_MODULE)<br/> 797LOCAL_POST_PROCESS_COMMAND := /Developer/Tools/Rez -d __DARWIN__ -t APPL\<br/> 798 -d __WXMAC__ -o $(module) Carbon.r 799</code></p> 800 801<h4>LOCAL_PREBUILT_EXECUTABLES</h4> 802<p>When including $(BUILD_MULTI_PREBUILT) or $(BUILD_HOST_PREBUILT), set these 803to executables that you want copied. They're located automatically into the 804right bin directory.</p> 805 806<h4>LOCAL_PREBUILT_LIBS</h4> 807<p>When including $(BUILD_MULTI_PREBUILT) or $(BUILD_HOST_PREBUILT), set these 808to libraries that you want copied. They're located automatically into the 809right lib directory.</p> 810 811<h4>LOCAL_SHARED_LIBRARIES</h4> 812<p>These are the libraries you directly link against. You don't need to 813pass transitively included libraries. Specify the name without the suffix:</p> 814<p><code>LOCAL_SHARED_LIBRARIES := \<br/> 815 libutils \<br/> 816 libui \<br/> 817 libaudio \<br/> 818 libexpat \<br/> 819 libsgl 820</code></p> 821 822<h4>LOCAL_SRC_FILES</h4> 823<p>The build system looks at <code>LOCAL_SRC_FILES</code> to know what source 824files to compile -- .cpp .c .y .l .java. For lex and yacc files, it knows 825how to correctly do the intermediate .h and .c/.cpp files automatically. If 826the files are in a subdirectory of the one containing the Android.mk, prefix 827them with the directory name:</p> 828<p><code>LOCAL_SRC_FILES := \<br/> 829 file1.cpp \<br/> 830 dir/file2.cpp 831</code></p> 832 833<h4>LOCAL_STATIC_LIBRARIES</h4> 834<p>These are the static libraries that you want to include in your module. 835Mostly, we use shared libraries, but there are a couple of places, like 836host executables where we use static libraries instead. 837<p><code>LOCAL_STATIC_LIBRARIES := \<br/> 838 libutils \<br/> 839 libtinyxml 840</code></p> 841 842<h4>LOCAL_MODULE</h4> 843<p><code>LOCAL_MODULE</code> is the name of what's supposed to be generated 844from your Android.mk. For exmample, for libkjs, the <code>LOCAL_MODULE</code> 845is "libkjs" (the build system adds the appropriate suffix -- .so .dylib .dll). 846For app modules, use <code>LOCAL_PACKAGE_NAME</code> instead of 847<code>LOCAL_MODULE</code>. We're planning on switching to ant for the apps, 848so this might become moot.</p> 849 850<h4>LOCAL_MODULE_PATH</h4> 851<p>Instructs the build system to put the module somewhere other than what's 852normal for its type. If you override this, make sure you also set 853<code>LOCAL_UNSTRIPPED_PATH</code> if it's an executable or a shared library 854so the unstripped binary has somewhere to go. An error will occur if you forget 855to.</p> 856<p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p> 857 858<h4>LOCAL_MODULE_RELATIVE_PATH</h4> 859<p>Instructs the build system to put the module in a subdirectory under the 860directory that is normal for its type. If you set this you do not need to 861set <code>LOCAL_UNSTRIPPED_PATH</code>, the unstripped binaries will also use 862the relative path.</p> 863<p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p> 864 865<h4>LOCAL_MODULE_HOST_OS</h4> 866<p>This specifies which OSes are supported by this host module. It is not used 867for target builds. The accepted values here are combinations of 868<code>linux</code>, <code>darwin</code>, and <code>windows</code>. By default, 869linux and darwin(MacOS) are considered to be supported. If a module should 870build under windows, you must specify windows, and any others to be supported. 871Some examples:</p> 872<p><code>LOCAL_MODULE_HOST_OS := linux<br/> 873LOCAL_MODULE_HOST_OS := darwin linux windows</code></p> 874 875<h4>LOCAL_UNSTRIPPED_PATH</h4> 876<p>Instructs the build system to put the unstripped version of the module 877somewhere other than what's normal for its type. Usually, you override this 878because you overrode <code>LOCAL_MODULE_PATH</code> for an executable or a 879shared library. If you overrode <code>LOCAL_MODULE_PATH</code>, but not 880<code>LOCAL_UNSTRIPPED_PATH</code>, an error will occur.</p> 881<p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p> 882 883<h4>LOCAL_WHOLE_STATIC_LIBRARIES</h4> 884<p>These are the static libraries that you want to include in your module without allowing 885the linker to remove dead code from them. This is mostly useful if you want to add a static library 886to a shared library and have the static library's content exposed from the shared library. 887<p><code>LOCAL_WHOLE_STATIC_LIBRARIES := \<br/> 888 libsqlite3_android<br/> 889</code></p> 890 891<h4>LOCAL_YACCFLAGS</h4> 892<p>Any flags to pass to invocations of yacc for your module. A known limitation 893here is that the flags will be the same for all invocations of YACC for your 894module. This can be fixed. If you ever need it to be, just ask.</p> 895<p><code>LOCAL_YACCFLAGS := -p kjsyy</code></p> 896 897 898 899<h2>Implementation Details</h2> 900 901<p>You should never have to touch anything in the config directory unless 902you're adding a new platform, new tools, or adding new features to the 903build system. In general, please consult with the build system owner(s) 904(<a href="mailto:android-build-team">android-build-team</a>) before you go 905mucking around in here. That said, here are some notes on what's going on 906under the hood.</p> 907 908<h3>Environment Setup / buildspec.mk Versioning</h3> 909<p>In order to make easier for people when the build system changes, when 910it is necessary to make changes to buildspec.mk or to rerun the environment 911setup scripts, they contain a version number in the variable 912BUILD_ENV_SEQUENCE_NUMBER. If this variable does not match what the build 913system expects, it fails printing an error message explaining what happened. 914If you make a change that requires an update, you need to update two places 915so this message will be printed. 916<ul> 917 <li>In core/envsetup.mk, increment the 918 CORRECT_BUILD_ENV_SEQUENCE_NUMBER definition.</li> 919 <li>In buildspec.mk.default, update the BUILD_ENV_SEQUENCE_DUMBER 920 definition to match the one in core/envsetup.mk</li> 921</ul> 922The scripts automatically get the value from the build system, so they will 923trigger the warning as well. 924</p> 925 926<h3>Additional makefile variables</h3> 927<p>You probably shouldn't use these variables. Please consult 928<a href="mailto:android-build-team">android-build-team</a> before using them. 929These are mostly there for workarounds for other issues, or things that aren't 930completely done right.</p> 931 932<h4>LOCAL_ADDITIONAL_DEPENDENCIES</h4> 933<p>If your module needs to depend on anything else that 934isn't actually built in to it, you can add those make targets to 935<code>LOCAL_ADDITIONAL_DEPENDENCIES</code>. Usually this is a workaround 936for some other dependency that isn't created automatically.</p> 937 938<h4>LOCAL_BUILT_MODULE</h4> 939<p class=warning>This should not be used, since multiple binaries are now 940created from a single module defintiion.</p> 941<p>When a module is built, the module is created in an intermediate 942directory then copied to its final location. LOCAL_BUILT_MODULE is 943the full path to the intermediate file. See LOCAL_INSTALLED_MODULE 944for the path to the final installed location of the module.</p> 945 946<h4>LOCAL_IS_HOST_MODULE</h4> 947<p>Set by the host_xxx.mk includes to tell base_rules.mk and the other 948includes that we're building for the host.</p> 949 950<h4>LOCAL_INSTALLED_MODULE</h4> 951<p class=warning>This should not be used, since multiple binaries are now 952created from a single module defintiion.</p> 953<p>The fully qualified path name of the final location of the module. 954See LOCAL_BUILT_MODULE for the location of the intermediate file that 955the make rules should actually be constructing.</p> 956 957<h4>LOCAL_MODULE_CLASS</h4> 958<p>Which kind of module this is. This variable is used to construct other 959variable names used to locate the modules. See base_rules.mk and 960envsetup.mk.</p> 961 962<h4>LOCAL_MODULE_SUFFIX</h4> 963<p>The suffix that will be appended to <code>LOCAL_MODULE</code> to form 964<code>LOCAL_MODULE_NAME</code>. For example, .so, .a, .dylib.</p> 965 966<h4>LOCAL_STRIP_MODULE</h4> 967<p>If set to true (the default), the binary will be stripped and a debug 968link will be set up so that GDB will still work. If set to no_debuglink, 969the binary will be stripped, but no debug link will be added. If set to 970keep_symbols, it will strip the debug information, but keep the symbol table. 971Any other value will prevent stripping.</p> 972 973<h4>LOCAL_SYSTEM_SHARED_LIBRARIES</h4> 974<p>Used while building the base libraries: libc, libm, libdl. Usually 975it should be set to "none," as it is in $(CLEAR_VARS). When building 976these libraries, it's set to the ones they link against. For example, 977libc, libstdc++ and libdl don't link against anything, and libm links against 978libc. Normally, when the value is none, these libraries are automatically 979linked in to executables and libraries, so you don't need to specify them 980manually.</p> 981 982 983</body> 984</html> 985