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. Please keep it clean: 8 9 - keep the document xhtml-compliant, as many people use validating editors 10 - check your edits for typos, spelling errors, and questionable grammar 11 - prefer css styles to formatting tags like <font>, <tt>, etc. 12 - keep it human-readable and human-editable in a plain text editor: 13 - strive to keep lines wrapped at 80 columns, unless a link prevents it 14 - use plenty of whitespace 15 - try to pretty-format (wrt nesting and indenting) any hairy html 16 - check your inline javascript for errors using the javascript console 17 18 Your readers will be very appreciative. 19--> 20 21<head> 22 <title>Android Build System</title> 23 24 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 25 26 <link href="../android.css" type="text/css" rel="stylesheet" /> 27 28<!-- commenting out so the xhtml validator doesn't whine about < and &&; 29 the browser should still find the script tag. --> 30<script language="JavaScript1.2" type="text/javascript"> 31<!-- 32function highlight(name) { 33 if (document.getElementsByTagName) { 34 tags = [ 'span', 'div', 'tr', 'td' ]; 35 for (i in tags) { 36 elements = document.getElementsByTagName(tags[i]); 37 if (elements) { 38 for (j = 0; j < elements.length; j++) { 39 elementName = elements[j].getAttribute("class"); 40 if (elementName == name) { 41 elements[j].style.backgroundColor = "#C0F0C0"; 42 } else if (elementName && elementName.indexOf("rev") == 0) { 43 elements[j].style.backgroundColor = "#FFFFFF"; 44 } 45 } 46 } 47 } 48 } 49} 50//--> 51 </script> 52 <!-- this style sheet is for the style of the toc --> 53 <link href="toc.css" type="text/css" rel="stylesheet" /> 54 55 <style type="text/css"> 56 .warning { 57 border: 1px solid red; 58 padding: 8px; 59 color: red; 60 } 61 pre.prettyprint { 62 margin-top: 0; 63 } 64 li { 65 margin-top: 8px; 66 } 67 </style> 68</head> 69 70<body onload="prettyPrint()"> 71 72<h1><a name="My_Project_" />Android Build System</h1> 73 74<!-- Status is one of: Draft, Current, Needs Update, Obsolete --> 75<p style="text-align:center"> 76 <strong>Status:</strong> <em>Draft </em> 77 <small>(as of May 18, 2006)</small> 78</p> 79 80<p><b>Contents</b></p> 81<!-- this div expands out to a list of contents based on the H2 and H3 headings. 82Believe it! --> 83 <div id="nav" class="nav-2-levels"></div> 84 85<h2>Objective</h2> 86<p>The primary goals of reworking the build system are (1) to make dependencies 87work more reliably, so that when files need to rebuilt, they are, and (2) to 88improve performance of the build system so that unnecessary modules are not 89rebuilt, and so doing a top-level build when little or nothing needs to be done 90for a build takes as little time as possible.</p> 91 92<h2>Principles and Use Cases and Policy</h2> 93<p>Given the above objective, these are the overall principles and use cases 94that we will support. This is not an exhaustive list.</p> 95<h3>Multiple Targets</h3> 96<p>It needs to be possible to build the Android platform for multiple targets. 97This means:</p> 98<ul> 99 <li>The build system will support building tools for the host platform, 100 both ones that are used in the build process itself, and developer tools 101 like the simulator.</li> 102 <li>The build system will need to be able to build tools on Linux 103 (definitely Goobuntu and maybe Grhat), MacOS, and to some degree on 104 Windows.</li> 105 <li>The build system will need to be able to build the OS on Linux, and in 106 the short-term, MacOS. Note that this is a conscious decision to stop 107 building the OS on Windows. We are going to rely on the emulator there 108 and not attempt to use the simulator. This is a requirement change now 109 that the emulator story is looking brighter.</li> 110</ul> 111<h3>Non-Recursive Make</h3> 112<p>To achieve the objectives, the build system will be rewritten to use make 113non-recursively. For more background on this, read <a href="http://aegis.sourceforge.net/auug97.pdf">Recursive Make Considered Harmful</a>. For those that don't 114want PDF, here is the 115<a href="http://72.14.203.104/search?q=cache:HwuX7YF2uBIJ:aegis.sourceforge.net/auug97.pdf&hl=en&gl=us&ct=clnk&cd=2&client=firefox">Google translated version</a>. 116<h3>Rapid Compile-Test Cycles</h3> 117<p>When developing a component, for example a C++ shared library, it must be 118possible to easily rebuild just that component, and not have to wait more than a 119couple seconds for dependency checks, and not have to wait for unneeded 120components to be built.</p> 121<h3>Both Environment and Config File Based Settings</h3> 122<p>To set the target, and other options, some people on the team like to have a 123configuration file in a directory so they do not have an environment setup 124script to run, and others want an environment setup script to run so they can 125run builds in different terminals on the same tree, or switch back and forth 126in one terminal. We will support both.</p> 127<h3>Object File Directory / make clean</h3> 128<p>Object files and other intermediate files will be generated into a directory 129that is separate from the source tree. The goal is to have make clean be 130"rm -rf <obj>" in the tree root directory. The primary goals of 131this are to simplify searching the source tree, and to make "make clean" more 132reliable.</p> 133 134<h3>SDK</h3> 135<p>The SDK will be a tarball that will allow non-OS-developers to write apps. 136The apps will actually be built by first building the SDK, and then building 137the apps against that SDK. This will hopefully (1) make writing apps easier 138for us, because we won't have to rebuild the OS as much, and we can use the 139standard java-app development tools, and (2) allow us to dog-food the SDK, to 140help ensure its quality. Cedric has suggested (and I agree) that apps built 141from the SDK should be built with ant. Stay tuned for more details as we 142figure out exactly how this will work.</p> 143 144<h3>Dependecies</h3> 145<p>Dependencies should all be automatic. Unless there is a custom tool involved 146(e.g. the webkit has several), the dependencies for shared and static libraries, 147.c, .cpp, .h, .java, java libraries, etc., should all work without intervention 148in the Android.mk file.</p> 149 150<h3>Hiding command lines</h3> 151<p>The default of the build system will be to hide the command lines being 152executed for make steps. It will be possible to override this by specifying 153the showcommands pseudo-target, and possibly by setting an environment 154variable.</p> 155 156<h3>Wildcard source files</h3> 157<p>Wildcarding source file will be discouraged. It may be useful in some 158scenarios. The default <code>$(wildcard *)</code> will not work due to the 159current 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 163subdirectory. For example, libutils generates a shared library for the target 164and 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 168control the building of a given module. Only the top directory should 169have 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 173be fixed, and now is a good time to do it. This implies getting shared 174libraries 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, 180however 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 184tree at the same time, but this is a stretch goal, not a requirement. 185Doing two builds in the same tree, not at the same time must work. (update: 186it'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 191should 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 193problem is that this can create extra dependecies and slow down the build. 194It's a tradeoff.</p> 195 196<h3>Multiple builds</h3> 197<p>General way to perform builds across the set of known platforms. This 198would make it easy to perform multiple platform builds when testing a 199change, and allow a wide-scale "make clean". Right now the buildspec.mk 200or 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 204customizations 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, 209and 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 213builds.</p> 214 215<h3>build/envsetup.sh functions</h3> 216If 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 221lunch and choosecombo commands.</li> 222<li><b>m</b> - Runs <code>make</code> from the top of the tree. This is 223useful 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 225up 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, 228and .xml files below the current directory.</li> 229</ul> 230 231<h3>Build flavors/types</h3> 232<p> 233When building for a particular product, it's often useful to have minor 234variations on what is ultimately the final release build. These are the 235currently-defined "flavors" or "types" (we need to settle on a real name 236for 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> 296If 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 298you don't pick up files installed by the previous flavor. "<code>make 299clean</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 305there for your convenience:</p> 306 307<ul> 308<li><b>droid</b> - <code>make droid</code> is the normal build. This target 309is here because the default target has to have a name.</li> 310<li><b>all</b> - <code>make all</code> builds everything <code>make 311droid</code> does, plus everything whose <code>LOCAL_MODULE_TAGS</code> do not 312include the "droid" tag. The build server runs this to make sure 313that 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> - 315Let 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 317intermediate files, or you can type <code>make clean-Home</code> and it will 318clean just the Home app.</li> 319<li><b>clean</b> - <code>make clean</code> deletes all of the output and 320intermediate files for this configuration. This is the same as <code>rm -rf 321out/<configuration>/</code></li> 322<li><b>clobber</b> - <code>make clobber</code> deletes all of the output 323and 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 326directory inside the current combo directory. This is especially useful on the 327simulator and emulator, where the persistent data remains present between 328builds.</li> 329<li><b>showcommands</b> - <code>showcommands</code> is a modifier target 330which causes the build system to show the actual command lines for the build 331steps, instead of the brief descriptions. Most people don't like seeing the 332actual commands, because they're quite long and hard to read, but if you need 333to for debugging purposes, you can add <code>showcommands</code> to the list 334of targets you build. For example <code>make showcommands</code> will build 335the default android configuration, and <code>make runtime showcommands</code> 336will build just the runtime, and targets that it depends on, while displaying 337the full command lines. Please note that there are a couple places where the 338commands aren't shown here. These are considered bugs, and should be fixed, 339but they're often hard to track down. Please let 340<a href="mailto:android-build-team">android-build-team</a> know if you find 341any.</li> 342<li><b>LOCAL_MODULE</b> - Anything you specify as a <code>LOCAL_MODULE</code> 343in an Android.mk is made into a pseudotarget. For example, <code>make 344runtime</code> might be shorthand for <code>make 345out/linux-x86-debug/system/bin/runtime</code> (which would work), and 346<code>make libkjs</code> might be shorthand for <code>make 347out/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 349the 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 354common types of modules, there is a corresponding file in the templates 355directory. It will usually be enough to copy one of these, and fill in your 356own values. Some of the more esoteric values are not included in the 357templates, but are instead just documented here, as is the documentation 358on using custom tools to generate files.</p> 359<p>Mostly, you can just look for the TODO comments in the templates and do 360what it says. Please remember to delete the TODO comments when you're done 361to keep the files clean. The templates have minimal documentation in them, 362because they're going to be copied, and when that gets stale, the copies just 363won'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 368details.</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 373the name of the jar file. (Actually right now, we're not making jar files yet, 374just directories of .class files, but the directory is named according to 375what you put in LOCAL_MODULE). This name will be what goes in the 376LOCAL_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. 382Please delete the ones you don't need, and remove the TODO comments. It makes 383the rest of them easier to read, and you can always refer back to the templates 384if you need them again later.</p> 385<p>By default, on the target these are built into /system/bin, and on the 386host, 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> 389for 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, 395we use static libraries, since executable size isn't as big an issue, and it 396simplifies 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, 402we use static libraries, since executable size isn't as big an issue, and it 403simplifies 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 407to have the build system get the dependencies correct for it. Here are 408a 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 410need 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>$(local-generated-sources-dir)</code> 414and <code>$(local-host-generated-sources-dir)</code> macros use these variables 415to determine where to put the files. 416 417<h5>Example 1</h5> 418<p>Here, there is one generated file, called 419chartables.c, which doesn't depend on anything. And is built by the tool 420built to $(HOST_OUT_EXECUTABLES)/dftables. Note on the second to last line 421that a dependency is created on the tool.</p> 422<pre> 423intermediates:= $(local-generated-sources-dir) 424GEN := $(intermediates)/<font color=red>chartables.c</font> 425$(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) 428LOCAL_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 433a file. Pretend that it does something useful. Note how we use a 434target-specific variable called PRIVATE_INPUT_FILE to store the name of the 435input file.</p> 436<pre> 437intermediates:= $(local-generated-sources-dir) 438GEN := $(intermediates)/<font color=red>file.c</font> 439$(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) 443LOCAL_GENERATED_SOURCES += $(GEN) 444</pre> 445 446<h5>Example 3</h5> 447<p>If you have several files that are all similar in 448name, and use the same tool, you can combine them. (here the *.lut.h files are 449the generated ones, and the *.cpp files are the input files)</p> 450<pre> 451intermediates:= $(local-generated-sources-dir) 452GEN := $(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) 459LOCAL_GENERATED_SOURCES += $(GEN) 460</pre> 461 462<h3><a name="platform-specific"/>Platform specific conditionals</h3> 463<p>Sometimes you need to set flags specifically for different platforms. Here 464is a list of which values the different build-system defined variables will be 465set to and some examples.</p> 466<table cellspacing=25> 467<tr> 468 <td valign=top align=center> 469 <b>HOST_OS</b><br/> 470 linux<br/> 471 darwin 472 </td> 473 <td valign=top align=center> 474 <b>HOST_ARCH</b><br/> 475 x86<br/> 476 x86_64 477 </td> 478 <td valign=top align=center> 479 <b>HOST_BUILD_TYPE</b><br/> 480 release<br/> 481 debug 482 </td> 483</tr> 484<tr> 485 <td valign=top align=center> 486 <b>TARGET_ARCH</b><br/> 487 arm<br/> 488 arm64<br/> 489 mips<br/> 490 mips64<br/> 491 x86<br/> 492 x86_64 493 </td> 494 <td valign=top align=center> 495 <b>TARGET_BUILD_TYPE</b><br/> 496 release<br/> 497 debug 498 </td> 499</tr> 500</table> 501 502<p>There are also special variables to use instead of conditionals. Many of the 503normal variables (LOCAL_SRC_FILES, LOCAL_CFLAGS, etc) can be conditionally added 504to with _{arch} _{32|64}, and for the host, _{os}.</p> 505 506<h4>Some Examples</h4> 507<pre>ifeq ($(TARGET_BUILD_TYPE),release) 508LOCAL_CFLAGS += -DNDEBUG=1 509endif 510 511LOCAL_CFLAGS_arm += -DTARGET_IS_ARM 512 513LOCAL_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 518LOCAL_SRC_FILES_linux += futex_synchro.c 519LOCAL_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 526build somewhere else, read this.</p> 527<p>If you have modules that need to go in a subdirectory of their normal 528location, 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 530example:</p> 531<pre> 532LOCAL_MODULE_RELATIVE_PATH := hw 533</pre> 534<p>If you have modules that need to go in an entirely different location, for 535example the root filesystem instead of in /system, add these lines to your 536Android.mk:</p> 537<pre> 538LOCAL_MODULE_PATH := $(TARGET_ROOT_OUT_SBIN) 539LOCAL_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 544the 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 548places to build things.</p> 549<p>FYI: If you're installing an executable to /sbin, you probably also want to 550set <code>LOCAL_FORCE_STATIC_EXCUTABLE := true</code> in your Android.mk, which 551will 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 556alphabetically.</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_ASSET_FILES</h4> 596<p>In Android.mk files that <code>include $(BUILD_PACKAGE)</code> set this 597to 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 600system.</p> 601 602<h4>LOCAL_CC</h4> 603<p>If you want to use a different C compiler for this module, set LOCAL_CC 604to the path to the compiler. If LOCAL_CC is blank, the appropriate default 605compiler is used.</p> 606 607<h4>LOCAL_CXX</h4> 608<p>If you want to use a different C++ compiler for this module, set LOCAL_CXX 609to the path to the compiler. If LOCAL_CXX is blank, the appropriate default 610compiler is used.</p> 611 612<h4>LOCAL_CFLAGS</h4> 613<p>If you have additional flags to pass into the C or C++ compiler, add 614them here. For example:</p> 615<p><code>LOCAL_CFLAGS += -DLIBUTILS_NATIVE=1</code></p> 616 617<h4>LOCAL_CPPFLAGS</h4> 618<p>If you have additional flags to pass into <i>only</i> the C++ compiler, add 619them 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> 622on the compile line, so you can use it to override flags listed in 623<code>LOCAL_CFLAGS</code>. 624 625<h4>LOCAL_CPP_EXTENSION</h4> 626<p>If your C++ files end in something other than "<code>.cpp</code>", 627you can specify the custom extension here. For example:</p> 628<p><code>LOCAL_CPP_EXTENSION := .cc</code></p> 629Note that all C++ files for a given module must have the same 630extension; it is not currently possible to mix different extensions. 631 632<h4>LOCAL_NO_DEFAULT_COMPILER_FLAGS</h4> 633<p>Normally, the compile line for C and C++ files includes global include 634paths and global cflags. If <code>LOCAL_NO_DEFAULT_COMPILER_FLAGS</code> 635is non-empty, none of the default includes or flags will be used when compiling 636C 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 639any <code>DEBUG_CFLAGS</code> that are defined for the module. 640 641<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 644supply <code>LOCAL_COPY_HEADERS_TO</code>.</p> 645<p>This is going away because copying headers messes up the error messages, and 646may lead to people editing those headers instead of the correct ones. It also 647makes it easier to do bad layering in the system, which we want to avoid. We 648also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any 649headers.</p> 650 651<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 656may lead to people editing those headers instead of the correct ones. It also 657makes it easier to do bad layering in the system, which we want to avoid. We 658also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any 659headers.</p> 660 661<h4>LOCAL_C_INCLUDES</h4> 662<p>Additional directories to instruct the C/C++ compilers to look for header 663files 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 665want in the include paths. For example:</p> 666<p><code> 667LOCAL_C_INCLUDES += extlibs/zlib-1.2.3<br/> 668LOCAL_C_INCLUDES += $(LOCAL_PATH)/src 669</code></p> 670<p>You should not add subdirectories of include to 671<code>LOCAL_C_INCLUDES</code>, instead you should reference those files 672in the <code>#include</code> statement with their subdirectories. For 673example:</p> 674<p><code>#include <utils/KeyedVector.h></code><br/> 675not <code><s>#include <KeyedVector.h></s></code></p> 676<p>There are some components that are doing this wrong, and should be cleaned 677up.</p> 678 679<h4>LOCAL_MODULE_TAGS</h4> 680<p>Set <code>LOCAL_MODULE_TAGS</code> to any number of whitespace-separated 681tags. If the tag list is empty or contains <code>droid</code>, the module 682will get installed as part of a <code>make droid</code>. Otherwise, it will 683only get installed by running <code>make <your-module></code> 684or with the <code>make all</code> pseudotarget.</p> 685 686<h4>LOCAL_REQUIRED_MODULES</h4> 687<p>Set <code>LOCAL_REQUIRED_MODULES</code> to any number of whitespace-separated 688module names, like "libblah" or "Email". If this module is installed, all 689of the modules that it requires will be installed as well. This can be 690used to, e.g., ensure that necessary shared libraries or providers are 691installed when a given app is installed. 692 693<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 696list of libraries that we have in static form (currently only libc). This is 697really only used for executables in /sbin on the root filesystem.</p> 698 699<h4>LOCAL_GENERATED_SOURCES</h4> 700<p>Files that you add to <code>LOCAL_GENERATED_SOURCES</code> will be 701automatically generated and then linked in when your module is built. 702See the <a href="#custom-tools">Custom Tools</a> template makefile for an 703example.</p> 704 705<h4>LOCAL_JAVACFLAGS</h4> 706<p>If you have additional flags to pass into the javac compiler, add 707them here. For example:</p> 708<p><code>LOCAL_JAVACFLAGS += -Xlint:deprecation</code></p> 709 710<h4>LOCAL_JAVA_LIBRARIES</h4> 711<p>When linking Java apps and libraries, <code>LOCAL_JAVA_LIBRARIES</code> 712specifies which sets of java classes to include. Currently there are 713two of these: <code>core</code> and <code>framework</code>. 714In 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 719will be included automatically.</p> 720 721<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 724very important to ld, so test whatever you do on all platforms.</p> 725 726<h4>LOCAL_LDLIBS</h4> 727<p><code>LOCAL_LDLIBS</code> allows you to specify additional libraries 728that are not part of the build for your executable or library. Specify 729the libraries you want in -lxxx format; they're passed directly to the 730link line. However, keep in mind that there will be no dependency generated 731for these libraries. It's most useful in simulator builds where you want 732to use a library preinstalled on the host. The linker (ld) is a particularly 733fussy beast, so it's sometimes necessary to pass other flags here if you're 734doing something sneaky. Some examples:</p> 735<p><code>LOCAL_LDLIBS += -lcurses -lpthread<br/> 736LOCAL_LDLIBS += -Wl,-z,origin 737</code></p> 738 739<h4>LOCAL_NO_MANIFEST</h4> 740<p>If your package doesn't have a manifest (AndroidManifest.xml), then 741set <code>LOCAL_NO_MANIFEST:=true</code>. The common resources package 742does this.</p> 743 744<h4>LOCAL_PACKAGE_NAME</h4> 745<p><code>LOCAL_PACKAGE_NAME</code> is the name of an app. For example, 746Dialer, Contacts, etc. This will probably change or go away when we switch 747to an ant-based build system for the apps.</p> 748 749<h4>LOCAL_PATH</h4> 750<p>The directory your Android.mk file is in. You can set it by putting the 751following 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> 755variable, so you must call it before you include any other makefiles. Also, 756consider that any subdirectories you inlcude might reset LOCAL_PATH, so do your 757own stuff before you include them. This also means that if you try to write 758several <code>include</code> lines that reference <code>LOCAL_PATH</code>, 759it won't work, because those included makefiles might reset LOCAL_PATH. 760 761<h4>LOCAL_POST_PROCESS_COMMAND</h4> 762<p>For host executables, you can specify a command to run on the module 763after it's been linked. You might have to go through some contortions 764to get variables right because of early or late variable evaluation:</p> 765<p><code>module := $(HOST_OUT_EXECUTABLES)/$(LOCAL_MODULE)<br/> 766LOCAL_POST_PROCESS_COMMAND := /Developer/Tools/Rez -d __DARWIN__ -t APPL\<br/> 767 -d __WXMAC__ -o $(module) Carbon.r 768</code></p> 769 770<h4>LOCAL_PREBUILT_EXECUTABLES</h4> 771<p>When including $(BUILD_MULTI_PREBUILT) or $(BUILD_HOST_PREBUILT), set these 772to executables that you want copied. They're located automatically into the 773right bin directory.</p> 774 775<h4>LOCAL_PREBUILT_LIBS</h4> 776<p>When including $(BUILD_MULTI_PREBUILT) or $(BUILD_HOST_PREBUILT), set these 777to libraries that you want copied. They're located automatically into the 778right lib directory.</p> 779 780<h4>LOCAL_SHARED_LIBRARIES</h4> 781<p>These are the libraries you directly link against. You don't need to 782pass 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 789</code></p> 790 791<h4>LOCAL_SRC_FILES</h4> 792<p>The build system looks at <code>LOCAL_SRC_FILES</code> to know what source 793files to compile -- .cpp .c .y .l .java. For lex and yacc files, it knows 794how to correctly do the intermediate .h and .c/.cpp files automatically. If 795the files are in a subdirectory of the one containing the Android.mk, prefix 796them with the directory name:</p> 797<p><code>LOCAL_SRC_FILES := \<br/> 798 file1.cpp \<br/> 799 dir/file2.cpp 800</code></p> 801 802<h4>LOCAL_STATIC_LIBRARIES</h4> 803<p>These are the static libraries that you want to include in your module. 804Mostly, we use shared libraries, but there are a couple of places, like 805executables in sbin and host executables where we use static libraries instead. 806<p><code>LOCAL_STATIC_LIBRARIES := \<br/> 807 libutils \<br/> 808 libtinyxml 809</code></p> 810 811<h4>LOCAL_MODULE</h4> 812<p><code>LOCAL_MODULE</code> is the name of what's supposed to be generated 813from your Android.mk. For exmample, for libkjs, the <code>LOCAL_MODULE</code> 814is "libkjs" (the build system adds the appropriate suffix -- .so .dylib .dll). 815For 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, 817so this might become moot.</p> 818 819<h4>LOCAL_MODULE_PATH</h4> 820<p>Instructs the build system to put the module somewhere other than what's 821normal 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 823so the unstripped binary has somewhere to go. An error will occur if you forget 824to.</p> 825<p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p> 826 827<h4>LOCAL_MODULE_RELATIVE_PATH</h4> 828<p>Instructs the build system to put the module in a subdirectory under the 829directory that is normal for its type. If you set this you do not need to 830set <code>LOCAL_UNSTRIPPED_PATH</code>, the unstripped binaries will also use 831the relative path.</p> 832<p>See <a href="#moving-modules">Putting modules elsewhere</a> for more.</p> 833 834<h4>LOCAL_MODULE_HOST_OS</h4> 835<p>This specifies which OSes are supported by this host module. It is not used 836for target builds. The accepted values here are combinations of 837<code>linux</code>, <code>darwin</code>, and <code>windows</code>. By default, 838linux and darwin(MacOS) are considered to be supported. If a module should 839build under windows, you must specify windows, and any others to be supported. 840Some examples:</p> 841<p><code>LOCAL_MODULE_HOST_OS := linux<br/> 842LOCAL_MODULE_HOST_OS := darwin linux windows</code></p> 843 844<h4>LOCAL_UNSTRIPPED_PATH</h4> 845<p>Instructs the build system to put the unstripped version of the module 846somewhere other than what's normal for its type. Usually, you override this 847because you overrode <code>LOCAL_MODULE_PATH</code> for an executable or a 848shared 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> 851 852<h4>LOCAL_WHOLE_STATIC_LIBRARIES</h4> 853<p>These are the static libraries that you want to include in your module without allowing 854the linker to remove dead code from them. This is mostly useful if you want to add a static library 855to 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/> 858</code></p> 859 860<h4>LOCAL_YACCFLAGS</h4> 861<p>Any flags to pass to invocations of yacc for your module. A known limitation 862here is that the flags will be the same for all invocations of YACC for your 863module. This can be fixed. If you ever need it to be, just ask.</p> 864<p><code>LOCAL_YACCFLAGS := -p kjsyy</code></p> 865 866 867 868<h2>Implementation Details</h2> 869 870<p>You should never have to touch anything in the config directory unless 871you're adding a new platform, new tools, or adding new features to the 872build 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 874mucking around in here. That said, here are some notes on what's going on 875under the hood.</p> 876 877<h3>Environment Setup / buildspec.mk Versioning</h3> 878<p>In order to make easier for people when the build system changes, when 879it is necessary to make changes to buildspec.mk or to rerun the environment 880setup scripts, they contain a version number in the variable 881BUILD_ENV_SEQUENCE_NUMBER. If this variable does not match what the build 882system expects, it fails printing an error message explaining what happened. 883If you make a change that requires an update, you need to update two places 884so this message will be printed. 885<ul> 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> 890</ul> 891The scripts automatically get the value from the build system, so they will 892trigger the warning as well. 893</p> 894 895<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. 898These are mostly there for workarounds for other issues, or things that aren't 899completely done right.</p> 900 901<h4>LOCAL_ADDITIONAL_DEPENDENCIES</h4> 902<p>If your module needs to depend on anything else that 903isn't actually built in to it, you can add those make targets to 904<code>LOCAL_ADDITIONAL_DEPENDENCIES</code>. Usually this is a workaround 905for some other dependency that isn't created automatically.</p> 906 907<h4>LOCAL_BUILT_MODULE</h4> 908<p class=warning>This should not be used, since multiple binaries are now 909created from a single module defintiion.</p> 910<p>When a module is built, the module is created in an intermediate 911directory then copied to its final location. LOCAL_BUILT_MODULE is 912the full path to the intermediate file. See LOCAL_INSTALLED_MODULE 913for the path to the final installed location of the module.</p> 914 915<h4>LOCAL_IS_HOST_MODULE</h4> 916<p>Set by the host_xxx.mk includes to tell base_rules.mk and the other 917includes that we're building for the host.</p> 918 919<h4>LOCAL_INSTALLED_MODULE</h4> 920<p class=warning>This should not be used, since multiple binaries are now 921created from a single module defintiion.</p> 922<p>The fully qualified path name of the final location of the module. 923See LOCAL_BUILT_MODULE for the location of the intermediate file that 924the make rules should actually be constructing.</p> 925 926<h4>LOCAL_MODULE_CLASS</h4> 927<p>Which kind of module this is. This variable is used to construct other 928variable names used to locate the modules. See base_rules.mk and 929envsetup.mk.</p> 930 931<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> 934 935<h4>LOCAL_STRIP_MODULE</h4> 936<p>If set to true (the default), the binary will be stripped and a debug 937link will be set up so that GDB will still work. If set to no_debuglink, 938the binary will be stripped, but no debug link will be added. If set to 939keep_symbols, it will strip the debug information, but keep the symbol table. 940Any other value will prevent stripping.</p> 941 942<h4>LOCAL_SYSTEM_SHARED_LIBRARIES</h4> 943<p>Used while building the base libraries: libc, libm, libdl. Usually 944it should be set to "none," as it is in $(CLEAR_VARS). When building 945these libraries, it's set to the ones they link against. For example, 946libc, libstdc++ and libdl don't link against anything, and libm links against 947libc. Normally, when the value is none, these libraries are automatically 948linked in to executables and libraries, so you don't need to specify them 949manually.</p> 950 951 952</body> 953</html> 954