github.com/westcoastroms/westcoastroms-build@v0.0.0-20190928114312-2350e5a73030/build/make/core/build-system.html (about) 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. 97 This means:</p> 98 <ul> 99 <li>The build system will support building tools for the host platform, 100 both ones that are used in the build process itself, and developer tools 101 like the simulator.</li> 102 <li>The build system will need to be able to build tools on Linux 103 (definitely Goobuntu and maybe Grhat), MacOS, and to some degree on 104 Windows.</li> 105 <li>The build system will need to be able to build the OS on Linux, and in 106 the short-term, MacOS. Note that this is a conscious decision to stop 107 building the OS on Windows. We are going to rely on the emulator there 108 and not attempt to use the simulator. This is a requirement change now 109 that the emulator story is looking brighter.</li> 110 </ul> 111 <h3>Non-Recursive Make</h3> 112 <p>To achieve the objectives, the build system will be rewritten to use make 113 non-recursively. For more background on this, read <a href="http://aegis.sourceforge.net/auug97.pdf">Recursive Make Considered Harmful</a>. For those that don't 114 want PDF, here is the 115 <a href="http://72.14.203.104/search?q=cache:HwuX7YF2uBIJ:aegis.sourceforge.net/auug97.pdf&hl=en&gl=us&ct=clnk&cd=2&client=firefox">Google translated version</a>. 116 <h3>Rapid Compile-Test Cycles</h3> 117 <p>When developing a component, for example a C++ shared library, it must be 118 possible to easily rebuild just that component, and not have to wait more than a 119 couple seconds for dependency checks, and not have to wait for unneeded 120 components to be built.</p> 121 <h3>Both Environment and Config File Based Settings</h3> 122 <p>To set the target, and other options, some people on the team like to have a 123 configuration file in a directory so they do not have an environment setup 124 script to run, and others want an environment setup script to run so they can 125 run builds in different terminals on the same tree, or switch back and forth 126 in one terminal. We will support both.</p> 127 <h3>Object File Directory / make clean</h3> 128 <p>Object files and other intermediate files will be generated into a directory 129 that is separate from the source tree. The goal is to have make clean be 130 "rm -rf <obj>" in the tree root directory. The primary goals of 131 this are to simplify searching the source tree, and to make "make clean" more 132 reliable.</p> 133 134 <h3>SDK</h3> 135 <p>The SDK will be a tarball that will allow non-OS-developers to write apps. 136 The apps will actually be built by first building the SDK, and then building 137 the apps against that SDK. This will hopefully (1) make writing apps easier 138 for us, because we won't have to rebuild the OS as much, and we can use the 139 standard java-app development tools, and (2) allow us to dog-food the SDK, to 140 help ensure its quality. Cedric has suggested (and I agree) that apps built 141 from the SDK should be built with ant. Stay tuned for more details as we 142 figure out exactly how this will work.</p> 143 144 <h3>Dependecies</h3> 145 <p>Dependencies should all be automatic. Unless there is a custom tool involved 146 (e.g. the webkit has several), the dependencies for shared and static libraries, 147 .c, .cpp, .h, .java, java libraries, etc., should all work without intervention 148 in the Android.mk file.</p> 149 150 <h3>Hiding command lines</h3> 151 <p>The default of the build system will be to hide the command lines being 152 executed for make steps. It will be possible to override this by specifying 153 the showcommands pseudo-target, and possibly by setting an environment 154 variable.</p> 155 156 <h3>Wildcard source files</h3> 157 <p>Wildcarding source file will be discouraged. It may be useful in some 158 scenarios. The default <code>$(wildcard *)</code> will not work due to the 159 current directory being set to the root of the build tree.<p> 160 161 <h3>Multiple targets in one directory</h3> 162 <p>It will be possible to generate more than one target from a given 163 subdirectory. For example, libutils generates a shared library for the target 164 and a static library for the host.</p> 165 166 <h3>Makefile fragments for modules</h3> 167 <p><b>Android.mk</b> is the standard name for the makefile fragments that 168 control the building of a given module. Only the top directory should 169 have a file named "Makefile".</p> 170 171 <h3>Use shared libraries</h3> 172 <p>Currently, the simulator is not built to use shared libraries. This should 173 be fixed, and now is a good time to do it. This implies getting shared 174 libraries to work on Mac OS.</p> 175 176 177 <h2>Nice to Have</h2> 178 179 <p>These things would be nice to have, and this is a good place to record them, 180 however these are not promises.</p> 181 182 <h3>Simultaneous Builds</h3> 183 <p>The hope is to be able to do two builds for different combos in the same 184 tree at the same time, but this is a stretch goal, not a requirement. 185 Doing two builds in the same tree, not at the same time must work. (update: 186 it's looking like we'll get the two builds at the same time working)</p> 187 188 <h3>Deleting headers (or other dependecies)</h3> 189 <p>Problems can arise if you delete a header file that is referenced in 190 ".d" files. The easy way to deal with this is "make clean". There 191 should be a better way to handle it. (from fadden)</p> 192 <p>One way of solving this is introducing a dependency on the directory. The 193 problem is that this can create extra dependecies and slow down the build. 194 It's a tradeoff.</p> 195 196 <h3>Multiple builds</h3> 197 <p>General way to perform builds across the set of known platforms. This 198 would make it easy to perform multiple platform builds when testing a 199 change, and allow a wide-scale "make clean". Right now the buildspec.mk 200 or environment variables need to be updated before each build. (from fadden)</p> 201 202 <h3>Aftermarket Locales and Carrier</h3> 203 <p>We will eventually need to add support for creating locales and carrier 204 customizations to the SDK, but that will not be addressed right now.</p> 205 206 207 <h2><a id="usage"/>Usage</h2> 208 <p>You've read (or scrolled past) all of the motivations for this build system, 209 and you want to know how to use it. This is the place.</p> 210 211 <h3>Your first build</h3> 212 <p>The <a href="../building.html">Building</a> document describes how do do 213 builds.</p> 214 215 <h3>build/envsetup.sh functions</h3> 216 If you source the file build/envsetup.sh into your bash environment, 217 <code>. build/envsetup.sh</code>you'll get a few helpful shell functions: 218 219 <ul> 220 <li><b>printconfig</b> - Prints the current configuration as set by the 221 lunch and choosecombo commands.</li> 222 <li><b>m</b> - Runs <code>make</code> from the top of the tree. This is 223 useful because you can run make from within subdirectories. If you have the 224 <code>TOP</code> environment variable set, it uses that. If you don't, it looks 225 up the tree from the current directory, trying to find the top of the tree.</li> 226 <li><b>croot</b> - <code>cd</code> to the top of the tree.</li> 227 <li><b>sgrep</b> - grep for the regex you provide in all .c, .cpp, .h, .java, 228 and .xml files below the current directory.</li> 229 </ul> 230 231 <h3>Build flavors/types</h3> 232 <p> 233 When building for a particular product, it's often useful to have minor 234 variations on what is ultimately the final release build. These are the 235 currently-defined "flavors" or "types" (we need to settle on a real name 236 for these). 237 </p> 238 239 <table border=1> 240 <tr> 241 <td> 242 <code>eng<code> 243 </td> 244 <td> 245 This is the default flavor. A plain "<code>make</code>" is the 246 same as "<code>make eng</code>". <code>droid</code> is an alias 247 for <code>eng</code>. 248 <ul> 249 <li>Installs modules tagged with: <code>eng</code>, <code>debug</code>, 250 <code>user</code>, and/or <code>development</code>. 251 <li>Installs non-APK modules that have no tags specified. 252 <li>Installs APKs according to the product definition files, in 253 addition to tagged APKs. 254 <li><code>ro.secure=0</code> 255 <li><code>ro.debuggable=1</code> 256 <li><code>ro.kernel.android.checkjni=1</code> 257 <li><code>adb</code> is enabled by default. 258 </td> 259 </tr> 260 <tr> 261 <td> 262 <code>user<code> 263 </td> 264 <td> 265 "<code>make user</code>" 266 <p> 267 This is the flavor intended to be the final release bits. 268 <ul> 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. 277 </td> 278 </tr> 279 <tr> 280 <td> 281 <code>userdebug<code> 282 </td> 283 <td> 284 "<code>make userdebug</code>" 285 <p> 286 The same as <code>user</code>, except: 287 <ul> 288 <li>Also installs modules tagged with <code>debug</code>. 289 <li><code>ro.debuggable=1</code> 290 <li><code>adb</code> is enabled by default. 291 </td> 292 </tr> 293 </table> 294 295 <p> 296 If you build one flavor and then want to build another, you should run 297 "<code>make installclean</code>" between the two makes to guarantee that 298 you don't pick up files installed by the previous flavor. "<code>make 299 clean</code>" will also suffice, but it takes a lot longer. 300 </p> 301 302 303 <h3>More pseudotargets</h3> 304 <p>Sometimes you want to just build one thing. The following pseudotargets are 305 there for your convenience:</p> 306 307 <ul> 308 <li><b>droid</b> - <code>make droid</code> is the normal build. This target 309 is here because the default target has to have a name.</li> 310 <li><b>all</b> - <code>make all</code> builds everything <code>make 311 droid</code> does, plus everything whose <code>LOCAL_MODULE_TAGS</code> do not 312 include the "droid" tag. The build server runs this to make sure 313 that everything that is in the tree and has an Android.mk builds.</li> 314 <li><b>clean-$(LOCAL_MODULE)</b> and <b>clean-$(LOCAL_PACKAGE_NAME)</b> - 315 Let you selectively clean one target. For example, you can type 316 <code>make clean-libutils</code> and it will delete libutils.so and all of the 317 intermediate files, or you can type <code>make clean-Home</code> and it will 318 clean just the Home app.</li> 319 <li><b>clean</b> - <code>make clean</code> deletes all of the output and 320 intermediate files for this configuration. This is the same as <code>rm -rf 321 out/<configuration>/</code></li> 322 <li><b>clobber</b> - <code>make clobber</code> deletes all of the output 323 and intermediate files for all configurations. This is the same as 324 <code>rm -rf out/</code>.</li> 325 <li><b>dataclean</b> - <code>make dataclean</code> deletes contents of the data 326 directory inside the current combo directory. This is especially useful on the 327 simulator and emulator, where the persistent data remains present between 328 builds.</li> 329 <li><b>showcommands</b> - <code>showcommands</code> is a modifier target 330 which causes the build system to show the actual command lines for the build 331 steps, instead of the brief descriptions. Most people don't like seeing the 332 actual commands, because they're quite long and hard to read, but if you need 333 to for debugging purposes, you can add <code>showcommands</code> to the list 334 of targets you build. For example <code>make showcommands</code> will build 335 the default android configuration, and <code>make runtime showcommands</code> 336 will build just the runtime, and targets that it depends on, while displaying 337 the full command lines. Please note that there are a couple places where the 338 commands aren't shown here. These are considered bugs, and should be fixed, 339 but they're often hard to track down. Please let 340 <a href="mailto:android-build-team">android-build-team</a> know if you find 341 any.</li> 342 <li><b>LOCAL_MODULE</b> - Anything you specify as a <code>LOCAL_MODULE</code> 343 in an Android.mk is made into a pseudotarget. For example, <code>make 344 runtime</code> might be shorthand for <code>make 345 out/linux-x86-debug/system/bin/runtime</code> (which would work), and 346 <code>make libkjs</code> might be shorthand for <code>make 347 out/linux-x86-debug/system/lib/libkjs.so</code> (which would also work).</li> 348 <li><b>targets</b> - <code>make targets</code> will print a list of all of 349 the LOCAL_MODULE names you can make.</li> 350 </ul> 351 352 <h3><a name="templates"/>How to add another component to the build - Android.mk templates</h3> 353 <p>You have a new library, a new app, or a new executable. For each of the 354 common types of modules, there is a corresponding file in the templates 355 directory. It will usually be enough to copy one of these, and fill in your 356 own values. Some of the more esoteric values are not included in the 357 templates, but are instead just documented here, as is the documentation 358 on using custom tools to generate files.</p> 359 <p>Mostly, you can just look for the TODO comments in the templates and do 360 what it says. Please remember to delete the TODO comments when you're done 361 to keep the files clean. The templates have minimal documentation in them, 362 because they're going to be copied, and when that gets stale, the copies just 363 won't get updated. So read on...</p> 364 365 <h4>Apps</h4> 366 <p>Use the <code>templates/apps</code> file.</p> 367 <p>This template is pretty self-explanitory. See the variables below for more 368 details.</p> 369 370 <h4>Java Libraries</h4> 371 <p>Use the <code>templates/java_library</code> file.</p> 372 <p>The interesting thing here is the value of LOCAL_MODULE, which becomes 373 the name of the jar file. (Actually right now, we're not making jar files yet, 374 just directories of .class files, but the directory is named according to 375 what you put in LOCAL_MODULE). This name will be what goes in the 376 LOCAL_JAVA_LIBRARIES variable in modules that depend on your java library.</p> 377 378 <h4>C/C++ Executables</h4> 379 <p>Use the <code>templates/executable</code> file, or the 380 <code>templates/executable_host</code> file.</p> 381 <p>This template has a couple extra options that you usually don't need. 382 Please delete the ones you don't need, and remove the TODO comments. It makes 383 the rest of them easier to read, and you can always refer back to the templates 384 if you need them again later.</p> 385 <p>By default, on the target these are built into /system/bin, and on the 386 host, they're built into <combo>/host/bin. These can be overridden by setting 387 <code>LOCAL_MODULE_PATH</code> or <code>LOCAL_MODULE_RELATIVE_PATH</code>. See 388 <a href="#moving-targets">Putting targets elsewhere</a> 389 for more.</p> 390 391 <h4>Shared Libraries</h4> 392 <p>Use the <code>templates/shared_library</code> file, or the 393 <code>templates/shared_library_host</code> file.</p> 394 <p>Remember that on the target, we use shared libraries, and on the host, 395 we use static libraries, since executable size isn't as big an issue, and it 396 simplifies distribution in the SDK.</p> 397 398 <h4>Static Libraries</h4> 399 <p>Use the <code>templates/static_library</code> file, or the 400 <code>templates/static_library_host</code> file.</p> 401 <p>Remember that on the target, we use shared libraries, and on the host, 402 we use static libraries, since executable size isn't as big an issue, and it 403 simplifies distribution in the SDK.</p> 404 405 <h4><a name="custom-tools"/>Using Custom Tools</h4> 406 <p>If you have a tool that generates source files for you, it's possible 407 to have the build system get the dependencies correct for it. Here are 408 a couple of examples. <code>$@</code> is the make built-in variable for 409 "the current target." The <font color=red>red</font> parts are the parts you'll 410 need to change.</p> 411 412 <p>You need to put this after you have declared <code>LOCAL_PATH</code> and 413 <code>LOCAL_MODULE</code>, because the <code>$(local-generated-sources-dir)</code> 414 and <code>$(local-host-generated-sources-dir)</code> macros use these variables 415 to determine where to put the files. 416 417 <h5>Example 1</h5> 418 <p>Here, there is one generated file, called 419 chartables.c, which doesn't depend on anything. And is built by the tool 420 built to $(HOST_OUT_EXECUTABLES)/dftables. Note on the second to last line 421 that a dependency is created on the tool.</p> 422 <pre> 423 intermediates:= $(local-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) 429 </pre> 430 431 <h5>Example 2</h5> 432 <p>Here as a hypothetical example, we use use cat as if it were to transform 433 a file. Pretend that it does something useful. Note how we use a 434 target-specific variable called PRIVATE_INPUT_FILE to store the name of the 435 input file.</p> 436 <pre> 437 intermediates:= $(local-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)/input.file</font> 442 $(transform-generated-source) 443 LOCAL_GENERATED_SOURCES += $(GEN) 444 </pre> 445 446 <h5>Example 3</h5> 447 <p>If you have several files that are all similar in 448 name, and use the same tool, you can combine them. (here the *.lut.h files are 449 the generated ones, and the *.cpp files are the input files)</p> 450 <pre> 451 intermediates:= $(local-generated-sources-dir) 452 GEN := $(addprefix $(intermediates)<font color=red>/kjs/, \ 453 array_object.lut.h \ 454 bool_object.lut.h \</font> 455 ) 456 $(GEN): PRIVATE_CUSTOM_TOOL = <font color=red>perl libs/WebKitLib/WebKit/JavaScriptCore/kjs/create_hash_table $< -i > $@</font> 457 $(GEN): $(intermediates)/<font color=red>%.lut.h</font> : $(LOCAL_PATH)/<font color=red>%.cpp</font> 458 $(transform-generated-source) 459 LOCAL_GENERATED_SOURCES += $(GEN) 460 </pre> 461 462 <h3><a name="platform-specific"/>Platform specific conditionals</h3> 463 <p>Sometimes you need to set flags specifically for different platforms. Here 464 is a list of which values the different build-system defined variables will be 465 set to and some examples.</p> 466 <table cellspacing=25> 467 <tr> 468 <td valign=top align=center> 469 <b>HOST_OS</b><br/> 470 linux<br/> 471 darwin 472 </td> 473 <td valign=top align=center> 474 <b>HOST_ARCH</b><br/> 475 x86<br/> 476 x86_64 477 </td> 478 <td valign=top align=center> 479 <b>HOST_BUILD_TYPE</b><br/> 480 release<br/> 481 debug 482 </td> 483 </tr> 484 <tr> 485 <td valign=top align=center> 486 <b>TARGET_ARCH</b><br/> 487 arm<br/> 488 arm64<br/> 489 mips<br/> 490 mips64<br/> 491 x86<br/> 492 x86_64 493 </td> 494 <td valign=top align=center> 495 <b>TARGET_BUILD_TYPE</b><br/> 496 release<br/> 497 debug 498 </td> 499 </tr> 500 </table> 501 502 <p>There are also special variables to use instead of conditionals. Many of the 503 normal variables (LOCAL_SRC_FILES, LOCAL_CFLAGS, etc) can be conditionally added 504 to with _{arch} _{32|64}, and for the host, _{os}.</p> 505 506 <h4>Some Examples</h4> 507 <pre>ifeq ($(TARGET_BUILD_TYPE),release) 508 LOCAL_CFLAGS += -DNDEBUG=1 509 endif 510 511 LOCAL_CFLAGS_arm += -DTARGET_IS_ARM 512 513 LOCAL_CFLAGS_64 += -DBIG_POINTER 514 515 # from libutils 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 520 521 </pre> 522 523 524 <h3><a name="moving-modules"/>Putting modules elsewhere</h3> 525 <p>If you have modules that normally go somewhere, and you need to have them 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 530 example:</p> 531 <pre> 532 LOCAL_MODULE_RELATIVE_PATH := hw 533 </pre> 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 536 Android.mk:</p> 537 <pre> 538 LOCAL_MODULE_PATH := $(TARGET_ROOT_OUT_SBIN) 539 LOCAL_UNSTRIPPED_PATH := $(TARGET_ROOT_OUT_SBIN_UNSTRIPPED) 540 </pre> 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> 552 553 554 <h3>Android.mk variables</h3> 555 <p>These are the variables that you'll commonly see in Android.mk files, listed 556 alphabetically.</p> 557 <p>But first, a note on variable naming: 558 <ul> 559 <li><b>LOCAL_</b> - These variables are set per-module. They are cleared 560 by the <code>include $(CLEAR_VARS)</code> line, so you can rely on them 561 being empty after including that file. Most of the variables you'll use 562 in most modules are LOCAL_ variables.</li> 563 <li><b>PRIVATE_</b> - These variables are make-target-specific variables. That 564 means they're only usable within the commands for that module. It also 565 means that they're unlikely to change behind your back from modules that 566 are included after yours. This 567 <a href="http://www.gnu.org/software/make/manual/make.html#Target_002dspecific">link to the make documentation</a> 568 describes more about target-specific variables. Please note that there 569 are a couple of these laying around the tree that aren't prefixed with 570 PRIVATE_. It is safe, and they will be fixed as they are discovered. 571 Sorry for the confusion.</li> 572 <li><b>INTERNAL_</b> - These variables are critical to functioning of 573 the build system, so you shouldn't create variables named like this, and 574 you probably shouldn't be messing with these variables in your makefiles. 575 </li> 576 <li><b>HOST_</b> and <b>TARGET_</b> - These contain the directories 577 and definitions that are specific to either the host or the target builds. 578 Do not set variables that start with HOST_ or TARGET_ in your makefiles. 579 </li> 580 <li><b>HOST_CROSS_</b> - These contain the directories and definitions that 581 are specific to cross-building host binaries. The common case is building 582 windows host tools on linux. Do not set variables that start with 583 HOST_CROSS_ in your makefiles. 584 </li> 585 <li><b>BUILD_</b> and <b>CLEAR_VARS</b> - These contain the names of 586 well-defined template makefiles to include. Some examples are CLEAR_VARS 587 and BUILD_HOST_PACKAGE.</li> 588 <li>Any other name is fair-game for you to use in your Android.mk. However, 589 remember that this is a non-recursive build system, so it is possible that 590 your variable will be changed by another Android.mk included later, and be 591 different when the commands for your rule / module are executed.</li> 592 </ul> 593 </p> 594 595 <h4>LOCAL_ANNOTATION_PROCESSORS</h4> 596 <p>Set this to a list of modules built with <code>BUILD_HOST_JAVA_LIBRARY</code> 597 to have their jars passed to javac with -processorpath for use as annotation 598 processors.</p> 599 600 <h4>LOCAL_ANNOTATION_PROCESSOR_CLASSES</h4> 601 <p>Set this to a list of classes to be passed to javac as -processor arguments. 602 This list is would be unnecessary, as javac will autodetect annotation processor 603 classes, except that the Grok tool that is used on the Android source code 604 does not autodetect them and requires listing them manually.</p> 605 606 <h4>LOCAL_ASSET_FILES</h4> 607 <p>In Android.mk files that <code>include $(BUILD_PACKAGE)</code> set this 608 to the set of files you want built into your app. Usually:</p> 609 <p><code>LOCAL_ASSET_FILES += $(call find-subdir-assets)</code></p> 610 <p>This will probably change when we switch to ant for the apps' build 611 system.</p> 612 613 <h4>LOCAL_CC</h4> 614 <p>If you want to use a different C compiler for this module, set LOCAL_CC 615 to the path to the compiler. If LOCAL_CC is blank, the appropriate default 616 compiler is used.</p> 617 618 <h4>LOCAL_CXX</h4> 619 <p>If you want to use a different C++ compiler for this module, set LOCAL_CXX 620 to the path to the compiler. If LOCAL_CXX is blank, the appropriate default 621 compiler is used.</p> 622 623 <h4>LOCAL_CFLAGS</h4> 624 <p>If you have additional flags to pass into the C or C++ compiler, add 625 them here. For example:</p> 626 <p><code>LOCAL_CFLAGS += -DLIBUTILS_NATIVE=1</code></p> 627 628 <h4>LOCAL_CPPFLAGS</h4> 629 <p>If you have additional flags to pass into <i>only</i> the C++ compiler, add 630 them here. For example:</p> 631 <p><code>LOCAL_CPPFLAGS += -ffriend-injection</code></p> 632 <code>LOCAL_CPPFLAGS</code> is guaranteed to be after <code>LOCAL_CFLAGS</code> 633 on the compile line, so you can use it to override flags listed in 634 <code>LOCAL_CFLAGS</code>. 635 636 <h4>LOCAL_CPP_EXTENSION</h4> 637 <p>If your C++ files end in something other than "<code>.cpp</code>", 638 you can specify the custom extension here. For example:</p> 639 <p><code>LOCAL_CPP_EXTENSION := .cc</code></p> 640 Note that all C++ files for a given module must have the same 641 extension; it is not currently possible to mix different extensions. 642 643 <h4>LOCAL_NO_DEFAULT_COMPILER_FLAGS</h4> 644 <p>Normally, the compile line for C and C++ files includes global include 645 paths and global cflags. If <code>LOCAL_NO_DEFAULT_COMPILER_FLAGS</code> 646 is non-empty, none of the default includes or flags will be used when compiling 647 C and C++ files in this module. 648 <code>LOCAL_C_INCLUDES</code>, <code>LOCAL_CFLAGS</code>, and 649 <code>LOCAL_CPPFLAGS</code> will still be used in this case, as will 650 any <code>DEBUG_CFLAGS</code> that are defined for the module. 651 652 <h4>LOCAL_COPY_HEADERS</h4> 653 <p class=warning>This will be going away.</p> 654 <p>The set of files to copy to the install include tree. You must also 655 supply <code>LOCAL_COPY_HEADERS_TO</code>.</p> 656 <p>This is going away because copying headers messes up the error messages, and 657 may lead to people editing those headers instead of the correct ones. It also 658 makes it easier to do bad layering in the system, which we want to avoid. We 659 also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any 660 headers.</p> 661 662 <h4>LOCAL_COPY_HEADERS_TO</h4> 663 <p class=warning>This will be going away.</p> 664 <p>The directory within "include" to copy the headers listed in 665 <code>LOCAL_COPY_HEADERS</code> to.</p> 666 <p>This is going away because copying headers messes up the error messages, and 667 may lead to people editing those headers instead of the correct ones. It also 668 makes it easier to do bad layering in the system, which we want to avoid. We 669 also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any 670 headers.</p> 671 672 <h4>LOCAL_C_INCLUDES</h4> 673 <p>Additional directories to instruct the C/C++ compilers to look for header 674 files in. These paths are rooted at the top of the tree. Use 675 <code>LOCAL_PATH</code> if you have subdirectories of your own that you 676 want in the include paths. For example:</p> 677 <p><code> 678 LOCAL_C_INCLUDES += extlibs/zlib-1.2.3<br/> 679 LOCAL_C_INCLUDES += $(LOCAL_PATH)/src 680 </code></p> 681 <p>You should not add subdirectories of include to 682 <code>LOCAL_C_INCLUDES</code>, instead you should reference those files 683 in the <code>#include</code> statement with their subdirectories. For 684 example:</p> 685 <p><code>#include <utils/KeyedVector.h></code><br/> 686 not <code><s>#include <KeyedVector.h></s></code></p> 687 <p>There are some components that are doing this wrong, and should be cleaned 688 up.</p> 689 690 <h4>LOCAL_MODULE_TAGS</h4> 691 <p>Set <code>LOCAL_MODULE_TAGS</code> to any number of whitespace-separated 692 tags. If the tag list is empty or contains <code>droid</code>, the module 693 will get installed as part of a <code>make droid</code>. Otherwise, it will 694 only get installed by running <code>make <your-module></code> 695 or with the <code>make all</code> pseudotarget.</p> 696 697 <h4>LOCAL_REQUIRED_MODULES</h4> 698 <p>Set <code>LOCAL_REQUIRED_MODULES</code> to any number of whitespace-separated 699 module names, like "libblah" or "Email". If this module is installed, all 700 of the modules that it requires will be installed as well. This can be 701 used to, e.g., ensure that necessary shared libraries or providers are 702 installed when a given app is installed. 703 704 <h4>LOCAL_FORCE_STATIC_EXECUTABLE</h4> 705 <p>If your executable should be linked statically, set 706 <code>LOCAL_FORCE_STATIC_EXECUTABLE:=true</code>. There is a very short 707 list of libraries that we have in static form (currently only libc). This is 708 really only used for executables in /sbin on the root filesystem.</p> 709 710 <h4>LOCAL_GENERATED_SOURCES</h4> 711 <p>Files that you add to <code>LOCAL_GENERATED_SOURCES</code> will be 712 automatically generated and then linked in when your module is built. 713 See the <a href="#custom-tools">Custom Tools</a> template makefile for an 714 example.</p> 715 716 <h4>LOCAL_JAVACFLAGS</h4> 717 <p>If you have additional flags to pass into the javac compiler, add 718 them here. For example:</p> 719 <p><code>LOCAL_JAVACFLAGS += -Xlint:deprecation</code></p> 720 721 <h4>LOCAL_ERROR_PRONE_FLAGS</h4> 722 <p>If you have additional flags to pass into the error prone compiler, add 723 them here. For example:</p> 724 <p><code>LOCAL_ERROR_PRONE_FLAGS += -Xep:ClassCanBeStatic:ERROR</code></p> 725 726 <h4>LOCAL_JAVA_LIBRARIES</h4> 727 <p>When linking Java apps and libraries, <code>LOCAL_JAVA_LIBRARIES</code> 728 specifies which sets of java classes to include. Currently there are 729 two of these: <code>core</code> and <code>framework</code>. 730 In most cases, it will look like this:</p> 731 <p><code>LOCAL_JAVA_LIBRARIES := core framework</code></p> 732 <p>Note that setting <code>LOCAL_JAVA_LIBRARIES</code> is not necessary 733 (and is not allowed) when building an APK with 734 "<code>include $(BUILD_PACKAGE)</code>". The appropriate libraries 735 will be included automatically.</p> 736 737 <h4>LOCAL_LDFLAGS</h4> 738 <p>You can pass additional flags to the linker by setting 739 <code>LOCAL_LDFLAGS</code>. Keep in mind that the order of parameters is 740 very important to ld, so test whatever you do on all platforms.</p> 741 742 <h4>LOCAL_LDLIBS</h4> 743 <p><code>LOCAL_LDLIBS</code> allows you to specify additional libraries 744 that are not part of the build for your executable or library. Specify 745 the libraries you want in -lxxx format; they're passed directly to the 746 link line. However, keep in mind that there will be no dependency generated 747 for these libraries. It's most useful in simulator builds where you want 748 to use a library preinstalled on the host. The linker (ld) is a particularly 749 fussy beast, so it's sometimes necessary to pass other flags here if you're 750 doing something sneaky. Some examples:</p> 751 <p><code>LOCAL_LDLIBS += -lcurses -lpthread<br/> 752 LOCAL_LDLIBS += -Wl,-z,origin 753 </code></p> 754 755 <h4>LOCAL_NO_MANIFEST</h4> 756 <p>If your package doesn't have a manifest (AndroidManifest.xml), then 757 set <code>LOCAL_NO_MANIFEST:=true</code>. The common resources package 758 does this.</p> 759 760 <h4>LOCAL_PACKAGE_NAME</h4> 761 <p><code>LOCAL_PACKAGE_NAME</code> is the name of an app. For example, 762 Dialer, Contacts, etc. This will probably change or go away when we switch 763 to an ant-based build system for the apps.</p> 764 765 <h4>LOCAL_PATCH_MODULE (experimental option)</h4> 766 <p>As of January 2018, you almost certainly don't need this option, so please 767 ask and only use it if you understand what you're doing. This feature is 768 experimental and may go away in future.</p> 769 <p> 770 When compiling language level 9+ .java code in packages that are part of a 771 a system module, <code>LOCAL_PATCH_MODULE</code> names the module that your 772 sources and dependencies should be patched into. The Android runtime currently 773 (Jan 2018) doesn't implement the JEP 261 module system so this option is only 774 supported at compile time. It should only be needed to compile tests in packages 775 that exist in libcore and which are inconvenient to move elsewhere. 776 </p> 777 778 <h4>LOCAL_PATH</h4> 779 <p>The directory your Android.mk file is in. You can set it by putting the 780 following as the first line in your Android.mk:</p> 781 <p><code>LOCAL_PATH := $(my-dir)</code></p> 782 <p>The <code>my-dir</code> macro uses the 783 <code><a href="http://www.gnu.org/software/make/manual/make.html#MAKEFILE_005fLIST-Variable">MAKEFILE_LIST</a></code> 784 variable, so you must call it before you include any other makefiles. Also, 785 consider that any subdirectories you inlcude might reset LOCAL_PATH, so do your 786 own stuff before you include them. This also means that if you try to write 787 several <code>include</code> lines that reference <code>LOCAL_PATH</code>, 788 it won't work, because those included makefiles might reset LOCAL_PATH. 789 790 <h4>LOCAL_POST_PROCESS_COMMAND</h4> 791 <p>For host executables, you can specify a command to run on the module 792 after it's been linked. You might have to go through some contortions 793 to get variables right because of early or late variable evaluation:</p> 794 <p><code>module := $(HOST_OUT_EXECUTABLES)/$(LOCAL_MODULE)<br/> 795 LOCAL_POST_PROCESS_COMMAND := /Developer/Tools/Rez -d __DARWIN__ -t APPL\<br/> 796 -d __WXMAC__ -o $(module) Carbon.r 797 </code></p> 798 799 <h4>LOCAL_PREBUILT_EXECUTABLES</h4> 800 <p>When including $(BUILD_MULTI_PREBUILT) or $(BUILD_HOST_PREBUILT), set these 801 to executables that you want copied. They're located automatically into the 802 right bin directory.</p> 803 804 <h4>LOCAL_PREBUILT_LIBS</h4> 805 <p>When including $(BUILD_MULTI_PREBUILT) or $(BUILD_HOST_PREBUILT), set these 806 to libraries that you want copied. They're located automatically into the 807 right lib directory.</p> 808 809 <h4>LOCAL_SHARED_LIBRARIES</h4> 810 <p>These are the libraries you directly link against. You don't need to 811 pass transitively included libraries. Specify the name without the suffix:</p> 812 <p><code>LOCAL_SHARED_LIBRARIES := \<br/> 813 libutils \<br/> 814 libui \<br/> 815 libaudio \<br/> 816 libexpat \<br/> 817 libsgl 818 </code></p> 819 820 <h4>LOCAL_SRC_FILES</h4> 821 <p>The build system looks at <code>LOCAL_SRC_FILES</code> to know what source 822 files to compile -- .cpp .c .y .l .java. For lex and yacc files, it knows 823 how to correctly do the intermediate .h and .c/.cpp files automatically. If 824 the files are in a subdirectory of the one containing the Android.mk, prefix 825 them with the directory name:</p> 826 <p><code>LOCAL_SRC_FILES := \<br/> 827 file1.cpp \<br/> 828 dir/file2.cpp 829 </code></p> 830 831 <h4>LOCAL_STATIC_LIBRARIES</h4> 832 <p>These are the static libraries that you want to include in your module. 833 Mostly, we use shared libraries, but there are a couple of places, like 834 executables in sbin and host executables where we use static libraries instead. 835 <p><code>LOCAL_STATIC_LIBRARIES := \<br/> 836 libutils \<br/> 837 libtinyxml 838 </code></p> 839 840 <h4>LOCAL_MODULE</h4> 841 <p><code>LOCAL_MODULE</code> is the name of what's supposed to be generated 842 from your Android.mk. For exmample, for libkjs, the <code>LOCAL_MODULE</code> 843 is "libkjs" (the build system adds the appropriate suffix -- .so .dylib .dll). 844 For app modules, use <code>LOCAL_PACKAGE_NAME</code> instead of 845 <code>LOCAL_MODULE</code>. We're planning on switching to ant for the apps, 846 so this might become moot.</p> 847 848 <h4>LOCAL_MODULE_PATH</h4> 849 <p>Instructs the build system to put the module somewhere other than what's 850 normal for its type. If you override this, make sure you also set 851 <code>LOCAL_UNSTRIPPED_PATH</code> if it's an executable or a shared library 852 so the unstripped binary has somewhere to go. An error will occur if you forget 853 to.</p> 854 <p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p> 855 856 <h4>LOCAL_MODULE_RELATIVE_PATH</h4> 857 <p>Instructs the build system to put the module in a subdirectory under the 858 directory that is normal for its type. If you set this you do not need to 859 set <code>LOCAL_UNSTRIPPED_PATH</code>, the unstripped binaries will also use 860 the relative path.</p> 861 <p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p> 862 863 <h4>LOCAL_MODULE_HOST_OS</h4> 864 <p>This specifies which OSes are supported by this host module. It is not used 865 for target builds. The accepted values here are combinations of 866 <code>linux</code>, <code>darwin</code>, and <code>windows</code>. By default, 867 linux and darwin(MacOS) are considered to be supported. If a module should 868 build under windows, you must specify windows, and any others to be supported. 869 Some examples:</p> 870 <p><code>LOCAL_MODULE_HOST_OS := linux<br/> 871 LOCAL_MODULE_HOST_OS := darwin linux windows</code></p> 872 873 <h4>LOCAL_UNSTRIPPED_PATH</h4> 874 <p>Instructs the build system to put the unstripped version of the module 875 somewhere other than what's normal for its type. Usually, you override this 876 because you overrode <code>LOCAL_MODULE_PATH</code> for an executable or a 877 shared library. If you overrode <code>LOCAL_MODULE_PATH</code>, but not 878 <code>LOCAL_UNSTRIPPED_PATH</code>, an error will occur.</p> 879 <p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p> 880 881 <h4>LOCAL_WHOLE_STATIC_LIBRARIES</h4> 882 <p>These are the static libraries that you want to include in your module without allowing 883 the linker to remove dead code from them. This is mostly useful if you want to add a static library 884 to a shared library and have the static library's content exposed from the shared library. 885 <p><code>LOCAL_WHOLE_STATIC_LIBRARIES := \<br/> 886 libsqlite3_android<br/> 887 </code></p> 888 889 <h4>LOCAL_YACCFLAGS</h4> 890 <p>Any flags to pass to invocations of yacc for your module. A known limitation 891 here is that the flags will be the same for all invocations of YACC for your 892 module. This can be fixed. If you ever need it to be, just ask.</p> 893 <p><code>LOCAL_YACCFLAGS := -p kjsyy</code></p> 894 895 896 897 <h2>Implementation Details</h2> 898 899 <p>You should never have to touch anything in the config directory unless 900 you're adding a new platform, new tools, or adding new features to the 901 build system. In general, please consult with the build system owner(s) 902 (<a href="mailto:android-build-team">android-build-team</a>) before you go 903 mucking around in here. That said, here are some notes on what's going on 904 under the hood.</p> 905 906 <h3>Environment Setup / buildspec.mk Versioning</h3> 907 <p>In order to make easier for people when the build system changes, when 908 it is necessary to make changes to buildspec.mk or to rerun the environment 909 setup scripts, they contain a version number in the variable 910 BUILD_ENV_SEQUENCE_NUMBER. If this variable does not match what the build 911 system expects, it fails printing an error message explaining what happened. 912 If you make a change that requires an update, you need to update two places 913 so this message will be printed. 914 <ul> 915 <li>In core/envsetup.mk, increment the 916 CORRECT_BUILD_ENV_SEQUENCE_NUMBER definition.</li> 917 <li>In buildspec.mk.default, update the BUILD_ENV_SEQUENCE_DUMBER 918 definition to match the one in core/envsetup.mk</li> 919 </ul> 920 The scripts automatically get the value from the build system, so they will 921 trigger the warning as well. 922 </p> 923 924 <h3>Additional makefile variables</h3> 925 <p>You probably shouldn't use these variables. Please consult 926 <a href="mailto:android-build-team">android-build-team</a> before using them. 927 These are mostly there for workarounds for other issues, or things that aren't 928 completely done right.</p> 929 930 <h4>LOCAL_ADDITIONAL_DEPENDENCIES</h4> 931 <p>If your module needs to depend on anything else that 932 isn't actually built in to it, you can add those make targets to 933 <code>LOCAL_ADDITIONAL_DEPENDENCIES</code>. Usually this is a workaround 934 for some other dependency that isn't created automatically.</p> 935 936 <h4>LOCAL_BUILT_MODULE</h4> 937 <p class=warning>This should not be used, since multiple binaries are now 938 created from a single module defintiion.</p> 939 <p>When a module is built, the module is created in an intermediate 940 directory then copied to its final location. LOCAL_BUILT_MODULE is 941 the full path to the intermediate file. See LOCAL_INSTALLED_MODULE 942 for the path to the final installed location of the module.</p> 943 944 <h4>LOCAL_IS_HOST_MODULE</h4> 945 <p>Set by the host_xxx.mk includes to tell base_rules.mk and the other 946 includes that we're building for the host.</p> 947 948 <h4>LOCAL_INSTALLED_MODULE</h4> 949 <p class=warning>This should not be used, since multiple binaries are now 950 created from a single module defintiion.</p> 951 <p>The fully qualified path name of the final location of the module. 952 See LOCAL_BUILT_MODULE for the location of the intermediate file that 953 the make rules should actually be constructing.</p> 954 955 <h4>LOCAL_MODULE_CLASS</h4> 956 <p>Which kind of module this is. This variable is used to construct other 957 variable names used to locate the modules. See base_rules.mk and 958 envsetup.mk.</p> 959 960 <h4>LOCAL_MODULE_SUFFIX</h4> 961 <p>The suffix that will be appended to <code>LOCAL_MODULE</code> to form 962 <code>LOCAL_MODULE_NAME</code>. For example, .so, .a, .dylib.</p> 963 964 <h4>LOCAL_STRIP_MODULE</h4> 965 <p>If set to true (the default), the binary will be stripped and a debug 966 link will be set up so that GDB will still work. If set to no_debuglink, 967 the binary will be stripped, but no debug link will be added. If set to 968 keep_symbols, it will strip the debug information, but keep the symbol table. 969 Any other value will prevent stripping.</p> 970 971 <h4>LOCAL_SYSTEM_SHARED_LIBRARIES</h4> 972 <p>Used while building the base libraries: libc, libm, libdl. Usually 973 it should be set to "none," as it is in $(CLEAR_VARS). When building 974 these libraries, it's set to the ones they link against. For example, 975 libc, libstdc++ and libdl don't link against anything, and libm links against 976 libc. Normally, when the value is none, these libraries are automatically 977 linked in to executables and libraries, so you don't need to specify them 978 manually.</p> 979 980 981 </body> 982 </html>