1 % Building OpenJDK
   2 
   3 ## TL;DR (Instructions for the Impatient)
   4 
   5 If you are eager to try out building OpenJDK, these simple steps works most of
   6 the time. They assume that you have installed Mercurial (and Cygwin if running
   7 on Windows) and cloned the top-level OpenJDK repository that you want to build.
   8 
   9  1. [Get the complete source code](#getting-the-source-code): \
  10     `bash get_source.sh`
  11 
  12  2. [Run configure](#running-configure): \
  13     `bash configure`
  14 
  15     If `configure` fails due to missing dependencies (to either the
  16     [toolchain](#native-compiler-toolchain-requirements), [external libraries](
  17     #external-library-requirements) or the [boot JDK](#boot-jdk-requirements)),
  18     most of the time it prints a suggestion on how to resolve the situation on
  19     your platform. Follow the instructions, and try running `bash configure`
  20     again.
  21 
  22  3. [Run make](#running-make): \
  23     `make images`
  24 
  25  4. Verify your newly built JDK: \
  26     `./build/*/images/jdk/bin/java -version`
  27 
  28  5. [Run basic tests](##running-tests): \
  29     `make run-test-tier1`
  30 
  31 If any of these steps failed, or if you want to know more about build
  32 requirements or build functionality, please continue reading this document.
  33 
  34 ## Introduction
  35 
  36 OpenJDK is a complex software project. Building it requires a certain amount of
  37 technical expertise, a fair number of dependencies on external software, and
  38 reasonably powerful hardware.
  39 
  40 If you just want to use OpenJDK and not build it yourself, this document is not
  41 for you. See for instance [OpenJDK installation](
  42 http://openjdk.java.net/install) for some methods of installing a prebuilt
  43 OpenJDK.
  44 
  45 ## Getting the Source Code
  46 
  47 OpenJDK uses [Mercurial](http://www.mercurial-scm.org) for source control. The
  48 source code is contained not in a single Mercurial repository, but in a tree
  49 ("forest") of interrelated repositories. You will need to check out all of the
  50 repositories to be able to build OpenJDK. To assist you in dealing with this
  51 somewhat unusual arrangement, there are multiple tools available, which are
  52 explained below.
  53 
  54 In any case, make sure you are getting the correct version. At the [OpenJDK
  55 Mercurial server](http://hg.openjdk.java.net/) you can see a list of all
  56 available forests. If you want to build an older version, e.g. JDK 8, it is
  57 recommended that you get the `jdk8u` forest, which contains incremental
  58 updates, instead of the `jdk8` forest, which was frozen at JDK 8 GA.
  59 
  60 If you are new to Mercurial, a good place to start is the [Mercurial Beginner's
  61 Guide](http://www.mercurial-scm.org/guide). The rest of this document assumes a
  62 working knowledge of Mercurial.
  63 
  64 ### Special Considerations
  65 
  66 For a smooth building experience, it is recommended that you follow these rules
  67 on where and how to check out the source code.
  68 
  69   * Do not check out the source code in a path which contains spaces. Chances
  70     are the build will not work. This is most likely to be an issue on Windows
  71     systems.
  72 
  73   * Do not check out the source code in a path which has a very long name or is
  74     nested many levels deep. Chances are you will hit an OS limitation during
  75     the build.
  76 
  77   * Put the source code on a local disk, not a network share. If possible, use
  78     an SSD. The build process is very disk intensive, and having slow disk
  79     access will significantly increase build times. If you need to use a
  80     network share for the source code, see below for suggestions on how to keep
  81     the build artifacts on a local disk.
  82 
  83   * On Windows, extra care must be taken to make sure the [Cygwin](#cygwin)
  84     environment is consistent. It is recommended that you follow this
  85     procedure:
  86 
  87       * Create the directory that is going to contain the top directory of the
  88         OpenJDK clone by using the `mkdir` command in the Cygwin bash shell.
  89         That is, do *not* create it using Windows Explorer. This will ensure
  90         that it will have proper Cygwin attributes, and that it's children will
  91         inherit those attributes.
  92 
  93       * Do not put the OpenJDK clone in a path under your Cygwin home
  94         directory. This is especially important if your user name contains
  95         spaces and/or mixed upper and lower case letters.
  96 
  97       * Clone the OpenJDK repository using the Cygwin command line `hg` client
  98         as instructed in this document. That is, do *not* use another Mercurial
  99         client such as TortoiseHg.
 100 
 101     Failure to follow this procedure might result in hard-to-debug build
 102     problems.
 103 
 104 ### Using get\_source.sh
 105 
 106 The simplest way to get the entire forest is probably to clone the top-level
 107 repository and then run the `get_source.sh` script, like this:
 108 
 109 ```
 110 hg clone http://hg.openjdk.java.net/jdk9/jdk9
 111 cd jdk9
 112 bash get_source.sh
 113 ```
 114 
 115 The first time this is run, it will clone all the sub-repositories. Any
 116 subsequent execution of the script will update all sub-repositories to the
 117 latest revision.
 118 
 119 ### Using hgforest.sh
 120 
 121 The `hgforest.sh` script is more expressive than `get_source.sh`. It takes any
 122 number of arguments, and runs `hg` with those arguments on each sub-repository
 123 in the forest. The `get_source.sh` script is basically a simple wrapper that
 124 runs either `hgforest.sh clone` or `hgforest.sh pull -u`.
 125 
 126   * Cloning the forest:
 127     ```
 128     hg clone http://hg.openjdk.java.net/jdk9/jdk9
 129     cd jdk9
 130     bash common/bin/hgforest.sh clone
 131     ```
 132 
 133   * Pulling and updating the forest:
 134     ```
 135     bash common/bin/hgforest.sh pull -u
 136     ```
 137 
 138   * Merging over the entire forest:
 139     ```
 140     bash common/bin/hgforest.sh merge
 141     ```
 142 
 143 ### Using the Trees Extension
 144 
 145 The trees extension is a Mercurial add-on that helps you deal with the forest.
 146 More information is available on the [Code Tools trees page](
 147 http://openjdk.java.net/projects/code-tools/trees).
 148 
 149 #### Installing the Extension
 150 
 151 Install the extension by cloning `http://hg.openjdk.java.net/code-tools/trees`
 152 and updating your `.hgrc` file. Here's one way to do this:
 153 
 154 ```
 155 cd ~
 156 mkdir hg-ext
 157 cd hg-ext
 158 hg clone http://hg.openjdk.java.net/code-tools/trees
 159 cat << EOT >> ~/.hgrc
 160 [extensions]
 161 trees=~/hg-ext/trees/trees.py
 162 EOT
 163 ```
 164 
 165 #### Initializing the Tree
 166 
 167 The trees extension needs to know the structure of the forest. If you have
 168 already cloned the entire forest using another method, you can initialize the
 169 forest like this:
 170 
 171 ```
 172 hg tconf --set --walk --depth
 173 ```
 174 
 175 Or you can clone the entire forest at once, if you substitute `clone` with
 176 `tclone` when cloning the top-level repository, e.g. like this:
 177 
 178 ```
 179 hg tclone http://hg.openjdk.java.net/jdk9/jdk9
 180 ```
 181 
 182 In this case, the forest will be properly initialized from the start.
 183 
 184 #### Other Operations
 185 
 186 The trees extensions supplement many common operations with a trees version by
 187 prefixing a `t` to the normal Mercurial command, e.g. `tcommit`, `tstatus` or
 188 `tmerge`. For instance, to update the entire forest:
 189 
 190 ```
 191 hg tpull -u
 192 ```
 193 
 194 ## Build Hardware Requirements
 195 
 196 OpenJDK is a massive project, and require machines ranging from decent to
 197 powerful to be able to build in a reasonable amount of time, or to be able to
 198 complete a build at all.
 199 
 200 We *strongly* recommend usage of an SSD disk for the build, since disk speed is
 201 one of the limiting factors for build performance.
 202 
 203 ### Building on x86
 204 
 205 At a minimum, a machine with 2-4 cores is advisable, as well as 2-4 GB of RAM.
 206 (The more cores to use, the more memory you need.) At least 6 GB of free disk
 207 space is required (8 GB minimum for building on Solaris).
 208 
 209 Even for 32-bit builds, it is recommended to use a 64-bit build machine, and
 210 instead create a 32-bit target using `--with-target-bits=32`.
 211 
 212 ### Building on sparc
 213 
 214 At a minimum, a machine with 4 cores is advisable, as well as 4 GB of RAM. (The
 215 more cores to use, the more memory you need.) At least 8 GB of free disk space
 216 is required.
 217 
 218 ### Building on arm/aarch64
 219 
 220 This is not recommended. Instead, see the section on [Cross-compiling](
 221 #cross-compiling).
 222 
 223 ## Operating System Requirements
 224 
 225 The mainline OpenJDK project supports Linux, Solaris, macOS, AIX and Windows.
 226 Support for other operating system, e.g. BSD, exists in separate "port"
 227 projects.
 228 
 229 In general, OpenJDK can be built on a wide range of versions of these operating
 230 systems, but the further you deviate from what is tested on a daily basis, the
 231 more likely you are to run into problems.
 232 
 233 This table lists the OS versions used by Oracle when building JDK 9. Such
 234 information is always subject to change, but this table is up to date at the
 235 time of writing.
 236 
 237  Operating system   Vendor/version used
 238  -----------------  -------------------------------------------------------
 239  Linux              Oracle Enterprise Linux 6.4 / 7.1 (using kernel 3.8.13)
 240  Solaris            Solaris 11.1 SRU 21.4.1 / 11.2 SRU 5.5
 241  macOS              Mac OS X 10.9 (Mavericks) / 10.10 (Yosemite)
 242  Windows            Windows Server 2012 R2
 243 
 244 The double version numbers for Linux, Solaris and macOS is due to the hybrid
 245 model used at Oracle, where header files and external libraries from an older
 246 version is used when building on a more modern version of the OS.
 247 
 248 The Build Group has a wiki page with [Supported Build Platforms](
 249 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms). From
 250 time to time, this is updated by the community to list successes or failures of
 251 building on different platforms.
 252 
 253 ### Windows
 254 
 255 Windows XP is not a supported platform, but all newer Windows should be able to
 256 build OpenJDK.
 257 
 258 On Windows, it is important that you pay attention to the instructions in the
 259 [Special Considerations](#special-considerations).
 260 
 261 Windows is the only non-POSIX OS supported by OpenJDK, and as such, requires
 262 some extra care. A POSIX support layer is required to build on Windows. For
 263 OpenJDK 9, the only supported such layer is Cygwin. (Msys is no longer
 264 supported due to a too old bash; msys2 and the new Windows Subsystem for Linux
 265 (WSL) would likely be possible to support in a future version but that would
 266 require a community effort to implement.)
 267 
 268 Internally in the build system, all paths are represented as Unix-style paths,
 269 e.g. `/cygdrive/c/hg/jdk9/Makefile` rather than `C:\hg\jdk9\Makefile`. This
 270 rule also applies to input to the build system, e.g. in arguments to
 271 `configure`. So, use `--with-freetype=/cygdrive/c/freetype` rather than
 272 `--with-freetype=c:\freetype`. For details on this conversion, see the section
 273 on [Fixpath](#fixpath).
 274 
 275 #### Cygwin
 276 
 277 A functioning [Cygwin](http://www.cygwin.com/) environment is thus required for
 278 building OpenJDK on Windows. If you have a 64-bit OS, we strongly recommend
 279 using the 64-bit version of Cygwin.
 280 
 281 **Note:** Cygwin has a model of continuously updating all packages without any
 282 easy way to install or revert to a specific version of a package. This means
 283 that whenever you add or update a package in Cygwin, you might (inadvertently)
 284 update tools that are used by the OpenJDK build process, and that can cause
 285 unexpected build problems.
 286 
 287 OpenJDK requires GNU Make 4.0 or greater on Windows. This is usually not a
 288 problem, since Cygwin currently only distributes GNU Make at a version above
 289 4.0.
 290 
 291 Apart from the basic Cygwin installation, the following packages must also be
 292 installed:
 293 
 294   * `make`
 295   * `zip`
 296   * `unzip`
 297 
 298 Often, you can install these packages using the following command line:
 299 ```
 300 <path to Cygwin setup>/setup-x86_64 -q -P make -P unzip -P zip
 301 ```
 302 
 303 Unfortunately, Cygwin can be unreliable in certain circumstances. If you
 304 experience build tool crashes or strange issues when building on Windows,
 305 please check the Cygwin FAQ on the ["BLODA" list](
 306 https://cygwin.com/faq/faq.html#faq.using.bloda) and the section on [fork()
 307 failures](https://cygwin.com/faq/faq.html#faq.using.fixing-fork-failures).
 308 
 309 ### Solaris
 310 
 311 See `make/devkit/solaris11.1-package-list.txt` for a list of recommended
 312 packages to install when building on Solaris. The versions specified in this
 313 list is the versions used by the daily builds at Oracle, and is likely to work
 314 properly.
 315 
 316 Older versions of Solaris shipped a broken version of `objcopy`. At least
 317 version 2.21.1 is needed, which is provided by Solaris 11 Update 1. Objcopy is
 318 needed if you want to have external debug symbols. Please make sure you are
 319 using at least version 2.21.1 of objcopy, or that you disable external debug
 320 symbols.
 321 
 322 ### macOS
 323 
 324 Apple is using a quite aggressive scheme of pushing OS updates, and coupling
 325 these updates with required updates of Xcode. Unfortunately, this makes it
 326 difficult for a project like OpenJDK to keep pace with a continuously updated
 327 machine running macOS. See the section on [Apple Xcode](#apple-xcode) on some
 328 strategies to deal with this.
 329 
 330 It is recommended that you use at least Mac OS X 10.9 (Mavericks). At the time
 331 of writing, OpenJDK has been successfully compiled on macOS versions up to
 332 10.12.5 (Sierra), using XCode 8.3.2 and `--disable-warnings-as-errors`.
 333 
 334 The standard macOS environment contains the basic tooling needed to build, but
 335 for external libraries a package manager is recommended. OpenJDK uses
 336 [homebrew](https://brew.sh/) in the examples, but feel free to use whatever
 337 manager you want (or none).
 338 
 339 ### Linux
 340 
 341 It is often not much problem to build OpenJDK on Linux. The only general advice
 342 is to try to use the compilers, external libraries and header files as provided
 343 by your distribution.
 344 
 345 The basic tooling is provided as part of the core operating system, but you
 346 will most likely need to install developer packages.
 347 
 348 For apt-based distributions (Debian, Ubuntu, etc), try this:
 349 ```
 350 sudo apt-get install build-essential
 351 ```
 352 
 353 For rpm-based distributions (Fedora, Red Hat, etc), try this:
 354 ```
 355 sudo yum groupinstall "Development Tools"
 356 ```
 357 
 358 ### AIX
 359 
 360 The regular builds by SAP is using AIX version 7.1, but AIX 5.3 is also
 361 supported. See the [OpenJDK PowerPC Port Status Page](
 362 http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details.
 363 
 364 ## Native Compiler (Toolchain) Requirements
 365 
 366 Large portions of OpenJDK consists of native code, that needs to be compiled to
 367 be able to run on the target platform. In theory, toolchain and operating
 368 system should be independent factors, but in practice there's more or less a
 369 one-to-one correlation between target operating system and toolchain.
 370 
 371  Operating system   Supported toolchain
 372  ------------------ -------------------------
 373  Linux              gcc, clang
 374  macOS              Apple Xcode (using clang)
 375  Solaris            Oracle Solaris Studio
 376  AIX                IBM XL C/C++
 377  Windows            Microsoft Visual Studio
 378 
 379 Please see the individual sections on the toolchains for version
 380 recommendations. As a reference, these versions of the toolchains are used, at
 381 the time of writing, by Oracle for the daily builds of OpenJDK. It should be
 382 possible to compile OpenJDK with both older and newer versions, but the closer
 383 you stay to this list, the more likely you are to compile successfully without
 384 issues.
 385 
 386  Operating system   Toolchain version
 387  ------------------ -------------------------------------------------------
 388  Linux              gcc 4.9.2
 389  macOS              Apple Xcode 6.3 (using clang 6.1.0)
 390  Solaris            Oracle Solaris Studio 12.4 (with compiler version 5.13)
 391  Windows            Microsoft Visual Studio 2013 update 4
 392 
 393 ### gcc
 394 
 395 The minimum accepted version of gcc is 4.3. Older versions will not be accepted
 396 by `configure`.
 397 
 398 However, gcc 4.3 is quite old and OpenJDK is not regularly tested on this
 399 version, so it is recommended to use a more modern gcc.
 400 
 401 OpenJDK 9 includes patches that should allow gcc 6 to compile, but this should
 402 be considered experimental.
 403 
 404 In general, any version between these two should be usable.
 405 
 406 ### clang
 407 
 408 The minimum accepted version of clang is 3.2. Older versions will not be
 409 accepted by `configure`.
 410 
 411 To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`.
 412 
 413 ### Apple Xcode
 414 
 415 The oldest supported version of Xcode is 5.
 416 
 417 You will need the Xcode command lines developers tools to be able to build
 418 OpenJDK. (Actually, *only* the command lines tools are needed, not the IDE.)
 419 The simplest way to install these is to run:
 420 ```
 421 xcode-select --install
 422 ```
 423 
 424 It is advisable to keep an older version of Xcode for building OpenJDK when
 425 updating Xcode. This [blog page](
 426 http://iosdevelopertips.com/xcode/install-multiple-versions-of-xcode.html) has
 427 good suggestions on managing multiple Xcode versions. To use a specific version
 428 of Xcode, use `xcode-select -s` before running `configure`, or use
 429 `--with-toolchain-path` to point to the version of Xcode to use, e.g.
 430 `configure --with-toolchain-path=/Applications/Xcode5.app/Contents/Developer/usr/bin`
 431 
 432 If you have recently (inadvertently) updated your OS and/or Xcode version, and
 433 OpenJDK can no longer be built, please see the section on [Problems with the
 434 Build Environment](#problems-with-the-build-environment), and [Getting
 435 Help](#getting-help) to find out if there are any recent, non-merged patches
 436 available for this update.
 437 
 438 ### Oracle Solaris Studio
 439 
 440 The minimum accepted version of the Solaris Studio compilers is 5.13
 441 (corresponding to Solaris Studio 12.4). Older versions will not be accepted by
 442 configure.
 443 
 444 The Solaris Studio installation should contain at least these packages:
 445 
 446  Package                                            Version
 447  -------------------------------------------------- -------------
 448  developer/solarisstudio-124/backend                12.4-1.0.6.0
 449  developer/solarisstudio-124/c++                    12.4-1.0.10.0
 450  developer/solarisstudio-124/cc                     12.4-1.0.4.0
 451  developer/solarisstudio-124/library/c++-libs       12.4-1.0.10.0
 452  developer/solarisstudio-124/library/math-libs      12.4-1.0.0.1
 453  developer/solarisstudio-124/library/studio-gccrt   12.4-1.0.0.1
 454  developer/solarisstudio-124/studio-common          12.4-1.0.0.1
 455  developer/solarisstudio-124/studio-ja              12.4-1.0.0.1
 456  developer/solarisstudio-124/studio-legal           12.4-1.0.0.1
 457  developer/solarisstudio-124/studio-zhCN            12.4-1.0.0.1
 458 
 459 Compiling with Solaris Studio can sometimes be finicky. This is the exact
 460 version used by Oracle, which worked correctly at the time of writing:
 461 ```
 462 $ cc -V
 463 cc: Sun C 5.13 SunOS_i386 2014/10/20
 464 $ CC -V
 465 CC: Sun C++ 5.13 SunOS_i386 151846-10 2015/10/30
 466 ```
 467 
 468 ### Microsoft Visual Studio
 469 
 470 The minimum accepted version of Visual Studio is 2010. Older versions will not
 471 be accepted by `configure`. The maximum accepted version of Visual Studio is
 472 2013.
 473 
 474 If you have multiple versions of Visual Studio installed, `configure` will by
 475 default pick the latest. You can request a specific version to be used by
 476 setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2010`.
 477 
 478 If you get `LINK: fatal error LNK1123: failure during conversion to COFF: file
 479 invalid` when building using Visual Studio 2010, you have encountered
 480 [KB2757355](http://support.microsoft.com/kb/2757355), a bug triggered by a
 481 specific installation order. However, the solution suggested by the KB article
 482 does not always resolve the problem. See [this stackoverflow discussion](
 483 https://stackoverflow.com/questions/10888391) for other suggestions.
 484 
 485 ### IBM XL C/C++
 486 
 487 The regular builds by SAP is using version 12.1, described as `IBM XL C/C++ for
 488 AIX, V12.1 (5765-J02, 5725-C72) Version: 12.01.0000.0017`.
 489 
 490 See the [OpenJDK PowerPC Port Status Page](
 491 http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details.
 492 
 493 ## Boot JDK Requirements
 494 
 495 Paradoxically, building OpenJDK requires a pre-existing JDK. This is called the
 496 "boot JDK". The boot JDK does not have to be OpenJDK, though. If you are
 497 porting OpenJDK to a new platform, chances are that there already exists
 498 another JDK for that platform that is usable as boot JDK.
 499 
 500 The rule of thumb is that the boot JDK for building JDK major version *N*
 501 should be an JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be
 502 suitable as boot JDK. However, OpenJDK should be able to "build itself", so an
 503 up-to-date build of the current OpenJDK source is an acceptable alternative. If
 504 you are following the *N-1* rule, make sure you got the latest update version,
 505 since JDK 8 GA might not be able to build JDK 9 on all platforms.
 506 
 507 If the Boot JDK is not automatically detected, or the wrong JDK is picked, use
 508 `--with-boot-jdk` to point to the JDK to use.
 509 
 510 ### JDK 8 on Linux
 511 
 512 On apt-based distros (like Debian and Ubuntu), `sudo apt-get install
 513 openjdk-8-jdk` is typically enough to install OpenJDK 8. On rpm-based distros
 514 (like Fedora and Red Hat), try `sudo yum install java-1.8.0-openjdk-devel`.
 515 
 516 ### JDK 8 on Windows
 517 
 518 No pre-compiled binaries of OpenJDK 8 are readily available for Windows at the
 519 time of writing. An alternative is to download the [Oracle JDK](
 520 http://www.oracle.com/technetwork/java/javase/downloads). Another is the [Adopt
 521 OpenJDK Project](https://adoptopenjdk.net/), which publishes experimental
 522 prebuilt binaries for Windows.
 523 
 524 ### JDK 8 on macOS
 525 
 526 No pre-compiled binaries of OpenJDK 8 are readily available for macOS at the
 527 time of writing. An alternative is to download the [Oracle JDK](
 528 http://www.oracle.com/technetwork/java/javase/downloads), or to install it
 529 using `brew cask install java`. Another option is the [Adopt OpenJDK Project](
 530 https://adoptopenjdk.net/), which publishes experimental prebuilt binaries for
 531 macOS.
 532 
 533 ### JDK 8 on AIX
 534 
 535 No pre-compiled binaries of OpenJDK 8 are readily available for AIX at the
 536 time of writing. A starting point for working with OpenJDK on AIX is
 537 the [PowerPC/AIX Port Project](http://openjdk.java.net/projects/ppc-aix-port/).
 538 
 539 ## External Library Requirements
 540 
 541 Different platforms require different external libraries. In general, libraries
 542 are not optional - that is, they are either required or not used.
 543 
 544 If a required library is not detected by `configure`, you need to provide the
 545 path to it. There are two forms of the `configure` arguments to point to an
 546 external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to
 547 include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise,
 548 but require the include files an library files to reside in a default hierarchy
 549 under this directory. In most cases, it works fine.
 550 
 551 As a fallback, the second version allows you to point to the include directory
 552 and the lib directory separately.
 553 
 554 ### FreeType
 555 
 556 FreeType2 from [The FreeType Project](http://www.freetype.org/) is required on
 557 all platforms. At least version 2.3 is required.
 558 
 559   * To install on an apt-based Linux, try running `sudo apt-get install
 560     libcups2-dev`.
 561   * To install on an rpm-based Linux, try running `sudo yum install
 562     cups-devel`.
 563   * To install on Solaris, try running `pkg install system/library/freetype-2`.
 564   * To install on macOS, try running `brew install freetype`.
 565   * To install on Windows, see [below](#building-freetype-on-windows).
 566 
 567 Use `--with-freetype=<path>` if `configure` does not properly locate your
 568 FreeType files.
 569 
 570 #### Building FreeType on Windows
 571 
 572 On Windows, there is no readily available compiled version of FreeType. OpenJDK
 573 can help you compile FreeType from source. Download the FreeType sources and
 574 unpack them into an arbitrary directory:
 575 
 576 ```
 577 wget http://download.savannah.gnu.org/releases/freetype/freetype-2.5.3.tar.gz
 578 tar -xzf freetype-2.5.3.tar.gz
 579 ```
 580 
 581 Then run `configure` with `--with-freetype-src=<freetype_src>`. This will
 582 automatically build the freetype library into `<freetype_src>/lib64` for 64-bit
 583 builds or into `<freetype_src>/lib32` for 32-bit builds. Afterwards you can
 584 always use `--with-freetype-include=<freetype_src>/include` and
 585 `--with-freetype-lib=<freetype_src>/lib[32|64]` for other builds.
 586 
 587 Alternatively you can unpack the sources like this to use the default
 588 directory:
 589 
 590 ```
 591 tar --one-top-level=$HOME/freetype --strip-components=1 -xzf freetype-2.5.3.tar.gz
 592 ```
 593 
 594 ### CUPS
 595 
 596 CUPS, [Common UNIX Printing System](http://www.cups.org) header files are
 597 required on all platforms, except Windows. Often these files are provided by
 598 your operating system.
 599 
 600   * To install on an apt-based Linux, try running `sudo apt-get install
 601     libcups2-dev`.
 602   * To install on an rpm-based Linux, try running `sudo yum install
 603     cups-devel`.
 604   * To install on Solaris, try running `pkg install print/cups`.
 605 
 606 Use `--with-cups=<path>` if `configure` does not properly locate your CUPS
 607 files.
 608 
 609 ### X11
 610 
 611 Certain [X11](http://www.x.org/) libraries and include files are required on
 612 Linux and Solaris.
 613 
 614   * To install on an apt-based Linux, try running `sudo apt-get install
 615     libx11-dev libxext-dev libxrender-dev libxtst-dev libxt-dev`.
 616   * To install on an rpm-based Linux, try running `sudo yum install
 617     libXtst-devel libXt-devel libXrender-devel libXi-devel`.
 618   * To install on Solaris, try running `pkg install x11/header/x11-protocols
 619     x11/library/libice x11/library/libpthread-stubs x11/library/libsm
 620     x11/library/libx11 x11/library/libxau x11/library/libxcb
 621     x11/library/libxdmcp x11/library/libxevie x11/library/libxext
 622     x11/library/libxrender x11/library/libxscrnsaver x11/library/libxtst
 623     x11/library/toolkit/libxt`.
 624 
 625 Use `--with-x=<path>` if `configure` does not properly locate your X11 files.
 626 
 627 ### ALSA
 628 
 629 ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is
 630 required on Linux. At least version 0.9.1 of ALSA is required.
 631 
 632   * To install on an apt-based Linux, try running `sudo apt-get install
 633     libasound2-dev`.
 634   * To install on an rpm-based Linux, try running `sudo yum install
 635     alsa-lib-devel`.
 636 
 637 Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA
 638 files.
 639 
 640 ### libffi
 641 
 642 libffi, the [Portable Foreign Function Interface Library](
 643 http://sourceware.org/libffi) is required when building the Zero version of
 644 Hotspot.
 645 
 646   * To install on an apt-based Linux, try running `sudo apt-get install
 647     libffi-dev`.
 648   * To install on an rpm-based Linux, try running `sudo yum install
 649     libffi-devel`.
 650 
 651 Use `--with-libffi=<path>` if `configure` does not properly locate your libffi
 652 files.
 653 
 654 ### libelf
 655 
 656 libelf from the [elfutils project](http://sourceware.org/elfutils) is required
 657 when building the AOT feature of Hotspot.
 658 
 659   * To install on an apt-based Linux, try running `sudo apt-get install
 660     libelf-dev`.
 661   * To install on an rpm-based Linux, try running `sudo yum install
 662     elfutils-libelf-devel`.
 663 
 664 Use `--with-libelf=<path>` if `configure` does not properly locate your libelf
 665 files.
 666 
 667 ## Other Tooling Requirements
 668 
 669 ### GNU Make
 670 
 671 OpenJDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors
 672 of make are supported.
 673 
 674 At least version 3.81 of GNU Make must be used. For distributions supporting
 675 GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful
 676 functionality to handle parallel building (supported by `--with-output-sync`)
 677 and speed and stability improvements.
 678 
 679 Note that `configure` locates and verifies a properly functioning version of
 680 `make` and stores the path to this `make` binary in the configuration. If you
 681 start a build using `make` on the command line, you will be using the version
 682 of make found first in your `PATH`, and not necessarily the one stored in the
 683 configuration. This initial make will be used as "bootstrap make", and in a
 684 second stage, the make located by `configure` will be called. Normally, this
 685 will present no issues, but if you have a very old `make`, or a non-GNU Make
 686 `make` in your path, this might cause issues.
 687 
 688 If you want to override the default make found by `configure`, use the `MAKE`
 689 configure variable, e.g. `configure MAKE=/opt/gnu/make`.
 690 
 691 On Solaris, it is common to call the GNU version of make by using `gmake`.
 692 
 693 ### GNU Bash
 694 
 695 OpenJDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells
 696 are supported.
 697 
 698 At least version 3.2 of GNU Bash must be used.
 699 
 700 ### Autoconf
 701 
 702 If you want to modify the build system itself, you need to install [Autoconf](
 703 http://www.gnu.org/software/autoconf).
 704 
 705 However, if you only need to build OpenJDK or if you only edit the actual
 706 OpenJDK source files, there is no dependency on autoconf, since the source
 707 distribution includes a pre-generated `configure` shell script.
 708 
 709 See the section on [Autoconf Details](#autoconf-details) for details on how
 710 OpenJDK uses autoconf. This is especially important if you plan to contribute
 711 changes to OpenJDK that modifies the build system.
 712 
 713 ## Running Configure
 714 
 715 To build OpenJDK, you need a "configuration", which consists of a directory
 716 where to store the build output, coupled with information about the platform,
 717 the specific build machine, and choices that affect how OpenJDK is built.
 718 
 719 The configuration is created by the `configure` script. The basic invocation of
 720 the `configure` script looks like this:
 721 
 722 ```
 723 bash configure [options]
 724 ```
 725 
 726 This will create an output directory containing the configuration and setup an
 727 area for the build result. This directory typically looks like
 728 `build/linux-x64-normal-server-release`, but the actual name depends on your
 729 specific configuration. (It can also be set directly, see [Using Multiple
 730 Configurations](#using-multiple-configurations)). This directory is referred to
 731 as `$BUILD` in this documentation.
 732 
 733 `configure` will try to figure out what system you are running on and where all
 734 necessary build components are. If you have all prerequisites for building
 735 installed, it should find everything. If it fails to detect any component
 736 automatically, it will exit and inform you about the problem.
 737 
 738 Some command line examples:
 739 
 740   * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`:
 741     ```
 742     bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32
 743     ```
 744 
 745   * Create a debug build with the `server` JVM and DTrace enabled:
 746     ```
 747     bash configure --enable-debug --with-jvm-variants=server --enable-dtrace
 748     ```
 749 
 750 ### Common Configure Arguments
 751 
 752 Here follows some of the most common and important `configure` argument.
 753 
 754 To get up-to-date information on *all* available `configure` argument, please
 755 run:
 756 ```
 757 bash configure --help
 758 ```
 759 
 760 (Note that this help text also include general autoconf options, like
 761 `--dvidir`, that is not relevant to OpenJDK. To list only OpenJDK specific
 762 features, use `bash configure --help=short` instead.)
 763 
 764 #### Configure Arguments for Tailoring the Build
 765 
 766   * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand
 767     for `--with-debug-level=fastdebug`)
 768   * `--with-debug-level=<level>` - Set the debug level, which can be `release`,
 769     `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized`
 770     is variant of `release` with additional Hotspot debug code.
 771   * `--with-native-debug-symbols=<method>` - Specify if and how native debug
 772     symbols should be built. Available methods are `none`, `internal`,
 773     `external`, `zipped`. Default behavior depends on platform. See [Native
 774     Debug Symbols](#native-debug-symbols) for more details.
 775   * `--with-version-string=<string>` - Specify the version string this build
 776     will be identified with.
 777   * `--with-version-<part>=<value>` - A group of options, where `<part>` can be
 778     any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use
 779     these options to modify just the corresponding part of the version string
 780     from the default, or the value provided by `--with-version-string`.
 781   * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant
 782     (or variants) of Hotspot. Valid variants are: `server`, `client`,
 783     `minimal`, `core`, `zero`, `zeroshark`, `custom`. Note that not all
 784     variants are possible to combine in a single build.
 785   * `--with-jvm-features=<feature>[,<feature>...]` - Use the specified JVM
 786     features when building Hotspot. The list of features will be enabled on top
 787     of the default list. For the `custom` JVM variant, this default list is
 788     empty. A complete list of available JVM features can be found using `bash
 789     configure --help`.
 790   * `--with-target-bits=<bits>` - Create a target binary suitable for running
 791     on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build
 792     platform, instead of doing a full cross-compile. (This is known as a
 793     *reduced* build.)
 794 
 795 #### Configure Arguments for Native Compilation
 796 
 797   * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources
 798   * `--with-sysroot=<path>` - Use this directory as sysroot
 799   * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the
 800     default path when searching for all kinds of binaries
 801   * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when
 802     searching for toolchain binaries (compilers etc)
 803   * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C
 804     files
 805   * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++
 806     files
 807   * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK
 808     libraries
 809 
 810 #### Configure Arguments for External Dependencies
 811 
 812   * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK](
 813     #boot-jdk-requirements)
 814   * `--with-freetype=<path>` - Set the path to [FreeType](#freetype)
 815   * `--with-cups=<path>` - Set the path to [CUPS](#cups)
 816   * `--with-x=<path>` - Set the path to [X11](#x11)
 817   * `--with-alsa=<path>` - Set the path to [ALSA](#alsa)
 818   * `--with-libffi=<path>` - Set the path to [libffi](#libffi)
 819   * `--with-libelf=<path>` - Set the path to [libelf](#libelf)
 820   * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests](
 821     #running-tests)
 822 
 823 Certain third-party libraries used by OpenJDK (libjpeg, giflib, libpng, lcms
 824 and zlib) are included in the OpenJDK repository. The default behavior of the
 825 OpenJDK build is to use this version of these libraries, but they might be
 826 replaced by an external version. To do so, specify `system` as the `<source>`
 827 option in these arguments. (The default is `bundled`).
 828 
 829   * `--with-libjpeg=<source>` - Use the specified source for libjpeg
 830   * `--with-giflib=<source>` - Use the specified source for giflib
 831   * `--with-libpng=<source>` - Use the specified source for libpng
 832   * `--with-lcms=<source>` - Use the specified source for lcms
 833   * `--with-zlib=<source>` - Use the specified source for zlib
 834 
 835 On Linux, it is possible to select either static or dynamic linking of the C++
 836 runtime. The default is static linking, with dynamic linking as fallback if the
 837 static library is not found.
 838 
 839   * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic`
 840     or `default`) for linking the C++ runtime.
 841 
 842 ### Configure Control Variables
 843 
 844 It is possible to control certain aspects of `configure` by overriding the
 845 value of `configure` variables, either on the command line or in the
 846 environment.
 847 
 848 Normally, this is **not recommended**. If used improperly, it can lead to a
 849 broken configuration. Unless you're well versed in the build system, this is
 850 hard to use properly. Therefore, `configure` will print a warning if this is
 851 detected.
 852 
 853 However, there are a few `configure` variables, known as *control variables*
 854 that are supposed to be overriden on the command line. These are variables that
 855 describe the location of tools needed by the build, like `MAKE` or `GREP`. If
 856 any such variable is specified, `configure` will use that value instead of
 857 trying to autodetect the tool. For instance, `bash configure
 858 MAKE=/opt/gnumake4.0/bin/make`.
 859 
 860 If a configure argument exists, use that instead, e.g. use `--with-jtreg`
 861 instead of setting `JTREGEXE`.
 862 
 863 Also note that, despite what autoconf claims, setting `CFLAGS` will not
 864 accomplish anything. Instead use `--with-extra-cflags` (and similar for
 865 `cxxflags` and `ldflags`).
 866 
 867 ## Running Make
 868 
 869 When you have a proper configuration, all you need to do to build OpenJDK is to
 870 run `make`. (But see the warning at [GNU Make](#gnu-make) about running the
 871 correct version of make.)
 872 
 873 When running `make` without any arguments, the default target is used, which is
 874 the same as running `make default` or `make jdk`. This will build a minimal (or
 875 roughly minimal) set of compiled output (known as an "exploded image") needed
 876 for a developer to actually execute the newly built JDK. The idea is that in an
 877 incremental development fashion, when doing a normal make, you should only
 878 spend time recompiling what's changed (making it purely incremental) and only
 879 do the work that's needed to actually run and test your code.
 880 
 881 The output of the exploded image resides in `$BUILD/jdk`. You can test the
 882 newly built JDK like this: `$BUILD/jdk/bin/java -version`.
 883 
 884 ### Common Make Targets
 885 
 886 Apart from the default target, here are some common make targets:
 887 
 888   * `hotspot` - Build all of hotspot (but only hotspot)
 889   * `hotspot-<variant>` - Build just the specified jvm variant
 890   * `images` or `product-images` - Build the JRE and JDK images
 891   * `docs` or `docs-image` - Build the documentation image
 892   * `test-image` - Build the test image
 893   * `all` or `all-images` - Build all images (product, docs and test)
 894   * `bootcycle-images` - Build images twice, second time with newly built JDK
 895     (good for testing)
 896   * `clean` - Remove all files generated by make, but not those generated by
 897     configure
 898   * `dist-clean` - Remove all files, including configuration
 899 
 900 Run `make help` to get an up-to-date list of important make targets and make
 901 control variables.
 902 
 903 It is possible to build just a single module, a single phase, or a single phase
 904 of a single module, by creating make targets according to these followin
 905 patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`,
 906 `launchers`, `libs` or `rmic`. See [Using Fine-Grained Make Targets](
 907 #using-fine-grained-make-targets) for more details about this functionality.
 908 
 909   * `<phase>` - Build the specified phase and everything it depends on
 910   * `<module>` - Build the specified module and everything it depends on
 911   * `<module>-<phase>` - Compile the specified phase for the specified module
 912     and everything it depends on
 913 
 914 Similarly, it is possible to clean just a part of the build by creating make
 915 targets according to these patterns:
 916 
 917   * `clean-<outputdir>` - Remove the subdir in the output dir with the name
 918   * `clean-<phase>` - Remove all build results related to a certain build
 919     phase
 920   * `clean-<module>` - Remove all build results related to a certain module
 921   * `clean-<module>-<phase>` - Remove all build results related to a certain
 922     module and phase
 923 
 924 ### Make Control Variables
 925 
 926 It is possible to control `make` behavior by overriding the value of `make`
 927 variables, either on the command line or in the environment.
 928 
 929 Normally, this is **not recommended**. If used improperly, it can lead to a
 930 broken build. Unless you're well versed in the build system, this is hard to
 931 use properly. Therefore, `make` will print a warning if this is detected.
 932 
 933 However, there are a few `make` variables, known as *control variables* that
 934 are supposed to be overriden on the command line. These make up the "make time"
 935 configuration, as opposed to the "configure time" configuration.
 936 
 937 #### General Make Control Variables
 938 
 939   * `JOBS` - Specify the number of jobs to build with. See [Build
 940     Performance](#build-performance).
 941   * `LOG` - Specify the logging level and functionality. See [Checking the
 942     Build Log File](#checking-the-build-log-file)
 943   * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using
 944     Multiple Configurations](#using-multiple-configurations)
 945 
 946 #### Test Make Control Variables
 947 
 948 These make control variables only make sense when running tests. Please see
 949 [Testing OpenJDK](testing.html) for details.
 950 
 951   * `TEST`
 952   * `TEST_JOBS`
 953   * `JTREG`
 954   * `GTEST`
 955 
 956 #### Advanced Make Control Variables
 957 
 958 These advanced make control variables can be potentially unsafe. See [Hints and
 959 Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and
 960 [Understanding the Build System](#understanding-the-build-system) for details.
 961 
 962   * `SPEC`
 963   * `CONF_CHECK`
 964   * `COMPARE_BUILD`
 965   * `JDK_FILTER`
 966 
 967 ## Running Tests
 968 
 969 Most of the OpenJDK tests are using the [JTReg](http://openjdk.java.net/jtreg)
 970 test framework. Make sure that your configuration knows where to find your
 971 installation of JTReg. If this is not picked up automatically, use the
 972 `--with-jtreg=<path to jtreg home>` option to point to the JTReg framework.
 973 Note that this option should point to the JTReg home, i.e. the top directory,
 974 containing `lib/jtreg.jar` etc.
 975 
 976 To execute the most basic tests (tier 1), use:
 977 ```
 978 make run-test-tier1
 979 ```
 980 
 981 For more details on how to run tests, please see the [Testing
 982 OpenJDK](testing.html) document.
 983 
 984 ## Cross-compiling
 985 
 986 Cross-compiling means using one platform (the *build* platform) to generate
 987 output that can ran on another platform (the *target* platform).
 988 
 989 The typical reason for cross-compiling is that the build is performed on a more
 990 powerful desktop computer, but the resulting binaries will be able to run on a
 991 different, typically low-performing system. Most of the complications that
 992 arise when building for embedded is due to this separation of *build* and
 993 *target* systems.
 994 
 995 This requires a more complex setup and build procedure. This section assumes
 996 you are familiar with cross-compiling in general, and will only deal with the
 997 particularities of cross-compiling OpenJDK. If you are new to cross-compiling,
 998 please see the [external links at Wikipedia](
 999 https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start
1000 on reading materials.
1001 
1002 Cross-compiling OpenJDK requires you to be able to build both for the build
1003 platform and for the target platform. The reason for the former is that we need
1004 to build and execute tools during the build process, both native tools and Java
1005 tools.
1006 
1007 If all you want to do is to compile a 32-bit version, for the same OS, on a
1008 64-bit machine, consider using `--with-target-bits=32` instead of doing a
1009 full-blown cross-compilation. (While this surely is possible, it's a lot more
1010 work and will take much longer to build.)
1011 
1012 ### Boot JDK and Build JDK
1013 
1014 When cross-compiling, make sure you use a boot JDK that runs on the *build*
1015 system, and not on the *target* system.
1016 
1017 To be able to build, we need a "Build JDK", which is a JDK built from the
1018 current sources (that is, the same as the end result of the entire build
1019 process), but able to run on the *build* system, and not the *target* system.
1020 (In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when
1021 building JDK 9.)
1022 
1023 The build process will create a minimal Build JDK for you, as part of building.
1024 To speed up the build, you can use `--with-build-jdk` to `configure` to point
1025 to a pre-built Build JDK. Please note that the build result is unpredictable,
1026 and can possibly break in subtle ways, if the Build JDK does not **exactly**
1027 match the current sources.
1028 
1029 ### Specifying the Target Platform
1030 
1031 You *must* specify the target platform when cross-compiling. Doing so will also
1032 automatically turn the build into a cross-compiling mode. The simplest way to
1033 do this is to use the `--openjdk-target` argument, e.g.
1034 `--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`.
1035 This will automatically set the `--build`, `--host` and `--target` options for
1036 autoconf, which can otherwise be confusing. (In autoconf terminology, the
1037 "target" is known as "host", and "target" is used for building a Canadian
1038 cross-compiler.)
1039 
1040 ### Toolchain Considerations
1041 
1042 You will need two copies of your toolchain, one which generates output that can
1043 run on the target system (the normal, or *target*, toolchain), and one that
1044 generates output that can run on the build system (the *build* toolchain). Note
1045 that cross-compiling is only supported for gcc at the time being. The gcc
1046 standard is to prefix cross-compiling toolchains with the target denominator.
1047 If you follow this standard, `configure` is likely to pick up the toolchain
1048 correctly.
1049 
1050 The *build* toolchain will be autodetected just the same way the normal
1051 *build*/*target* toolchain will be autodetected when not cross-compiling. If
1052 this is not what you want, or if the autodetection fails, you can specify a
1053 devkit containing the *build* toolchain using `--with-build-devkit` to
1054 `configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments.
1055 
1056 It is often helpful to locate the cross-compilation tools, headers and
1057 libraries in a separate directory, outside the normal path, and point out that
1058 directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and
1059 appending the directory when searching for cross-compilations tools
1060 (`--with-toolchain-path`). As a compact form, you can also use `--with-devkit`
1061 to point to a single directory, if it is correctly setup. (See `basics.m4` for
1062 details.)
1063 
1064 If you are unsure what toolchain and versions to use, these have been proved
1065 working at the time of writing:
1066 
1067   * [aarch64](
1068 https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-linux-gnu-4.8-2013.11_linux.tar.xz)
1069   * [arm 32-bit hardware floating  point](
1070 https://launchpad.net/linaro-toolchain-unsupported/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux.tar.bz2)
1071 
1072 ### Native Libraries
1073 
1074 You will need copies of external native libraries for the *target* system,
1075 present on the *build* machine while building.
1076 
1077 Take care not to replace the *build* system's version of these libraries by
1078 mistake, since that can render the *build* machine unusable.
1079 
1080 Make sure that the libraries you point to (ALSA, X11, etc) are for the
1081 *target*, not the *build*, platform.
1082 
1083 #### ALSA
1084 
1085 You will need alsa libraries suitable for your *target* system. For most cases,
1086 using Debian's pre-built libraries work fine.
1087 
1088 Note that alsa is needed even if you only want to build a headless JDK.
1089 
1090   * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and
1091     search for the `libasound2` and `libasound2-dev` packages for your *target*
1092     system. Download them to /tmp.
1093 
1094   * Install the libraries into the cross-compilation toolchain. For instance:
1095 ```
1096 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc
1097 dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb .
1098 dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb .
1099 ```
1100 
1101   * If alsa is not properly detected by `configure`, you can point it out by
1102     `--with-alsa`.
1103 
1104 #### X11
1105 
1106 You will need X11 libraries suitable for your *target* system. For most cases,
1107 using Debian's pre-built libraries work fine.
1108 
1109 Note that X11 is needed even if you only want to build a headless JDK.
1110 
1111   * Go to [Debian Package Search](https://www.debian.org/distrib/packages),
1112     search for the following packages for your *target* system, and download them
1113     to /tmp/target-x11:
1114       * libxi
1115       * libxi-dev
1116       * x11proto-core-dev
1117       * x11proto-input-dev
1118       * x11proto-kb-dev
1119       * x11proto-render-dev
1120       * x11proto-xext-dev
1121       * libice-dev
1122       * libxrender
1123       * libxrender-dev
1124       * libsm-dev
1125       * libxt-dev
1126       * libx11
1127       * libx11-dev
1128       * libxtst
1129       * libxtst-dev
1130       * libxext
1131       * libxext-dev
1132 
1133   * Install the libraries into the cross-compilation toolchain. For instance:
1134     ```
1135     cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr
1136     mkdir X11R6
1137     cd X11R6
1138     for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done
1139     mv usr/* .
1140     cd lib
1141     cp arm-linux-gnueabihf/* .
1142     ```
1143 
1144     You can ignore the following messages. These libraries are not needed to
1145     successfully complete a full JDK build.
1146     ```
1147     cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory
1148     cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory
1149     cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory
1150     ```
1151 
1152   * If the X11 libraries are not properly detected by `configure`, you can
1153     point them out by `--with-x`.
1154 
1155 ### Building for ARM/aarch64
1156 
1157 A common cross-compilation target is the ARM CPU. When building for ARM, it is
1158 useful to set the ABI profile. A number of pre-defined ABI profiles are
1159 available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt,
1160 armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer
1161 properly supported on OpenJDK.
1162 
1163 OpenJDK contains two different ports for the aarch64 platform, one is the
1164 original aarch64 port from the [AArch64 Port Project](
1165 http://openjdk.java.net/projects/aarch64-port) and one is a 64-bit version of
1166 the Oracle contributed ARM port. When targeting aarch64, by the default the
1167 original aarch64 port is used. To select the Oracle ARM 64 port, use
1168 `--with-cpu-port=arm64`. Also set the corresponding value (`aarch64` or
1169 `arm64`) to --with-abi-profile, to ensure a consistent build.
1170 
1171 ### Verifying the Build
1172 
1173 The build will end up in a directory named like
1174 `build/linux-arm-normal-server-release`.
1175 
1176 Inside this build output directory, the `images/jdk` and `images/jre` will
1177 contain the newly built JDK and JRE, respectively, for your *target* system.
1178 
1179 Copy these folders to your *target* system. Then you can run e.g.
1180 `images/jdk/bin/java -version`.
1181 
1182 ## Build Performance
1183 
1184 Building OpenJDK requires a lot of horsepower. Some of the build tools can be
1185 adjusted to utilize more or less of resources such as parallel threads and
1186 memory. The `configure` script analyzes your system and selects reasonable
1187 values for such options based on your hardware. If you encounter resource
1188 problems, such as out of memory conditions, you can modify the detected values
1189 with:
1190 
1191   * `--with-num-cores` -- number of cores in the build system, e.g.
1192     `--with-num-cores=8`.
1193 
1194   * `--with-memory-size` -- memory (in MB) available in the build system, e.g.
1195     `--with-memory-size=1024`
1196 
1197 You can also specify directly the number of build jobs to use with
1198 `--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag
1199 to `make`. In most cases it will be ignored by the makefiles, but it can cause
1200 problems for some make targets.
1201 
1202 It might also be necessary to specify the JVM arguments passed to the Boot JDK,
1203 using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the
1204 default JVM arguments passed to the Boot JDK.
1205 
1206 At the end of a successful execution of `configure`, you will get a performance
1207 summary, indicating how well the build will perform. Here you will also get
1208 performance hints. If you want to build fast, pay attention to those!
1209 
1210 If you want to tweak build performance, run with `make LOG=info` to get a build
1211 time summary at the end of the build process.
1212 
1213 ### Disk Speed
1214 
1215 If you are using network shares, e.g. via NFS, for your source code, make sure
1216 the build directory is situated on local disk (e.g. by `ln -s
1217 /localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely
1218 high for building on a network share; close to unusable.
1219 
1220 Also, make sure that your build tools (including Boot JDK and toolchain) is
1221 located on a local disk and not a network share.
1222 
1223 As has been stressed elsewhere, do use SSD for source code and build directory,
1224 as well as (if possible) the build tools.
1225 
1226 ### Virus Checking
1227 
1228 The use of virus checking software, especially on Windows, can *significantly*
1229 slow down building of OpenJDK. If possible, turn off such software, or exclude
1230 the directory containing the OpenJDK source code from on-the-fly checking.
1231 
1232 ### Ccache
1233 
1234 The OpenJDK build supports building with ccache when using gcc or clang. Using
1235 ccache can radically speed up compilation of native code if you often rebuild
1236 the same sources. Your milage may vary however, so we recommend evaluating it
1237 for yourself. To enable it, make sure it's on the path and configure with
1238 `--enable-ccache`.
1239 
1240 ### Precompiled Headers
1241 
1242 By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains
1243 were it is properly supported (clang, gcc, and Visual Studio). Normally, this
1244 speeds up the build process, but in some circumstances, it can actually slow
1245 things down.
1246 
1247 You can experiment by disabling precompiled headers using
1248 `--disable-precompiled-headers`.
1249 
1250 ### Icecc / icecream
1251 
1252 [icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a
1253 distributed compiler network. If you have multiple machines available for
1254 building OpenJDK, you can drastically cut individual build times by utilizing
1255 it.
1256 
1257 To use, setup an icecc network, and install icecc on the build machine. Then
1258 run `configure` using `--enable-icecc`.
1259 
1260 ### Using sjavac
1261 
1262 To speed up Java compilation, especially incremental compilations, you can try
1263 the experimental sjavac compiler by using `--enable-sjavac`.
1264 
1265 ### Building the Right Target
1266 
1267 Selecting the proper target to build can have dramatic impact on build time.
1268 For normal usage, `jdk` or the default target is just fine. You only need to
1269 build `images` for shipping, or if your tests require it.
1270 
1271 See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on
1272 how to build an even smaller subset of the product.
1273 
1274 ## Troubleshooting
1275 
1276 If your build fails, it can sometimes be difficult to pinpoint the problem or
1277 find a proper solution.
1278 
1279 ### Locating the Source of the Error
1280 
1281 When a build fails, it can be hard to pinpoint the actual cause of the error.
1282 In a typical build process, different parts of the product build in parallel,
1283 with the output interlaced.
1284 
1285 #### Build Failure Summary
1286 
1287 To help you, the build system will print a failure summary at the end. It looks
1288 like this:
1289 
1290 ```
1291 ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2)
1292 
1293 === Output from failing command(s) repeated here ===
1294 * For target hotspot_variant-server_libjvm_objs_psMemoryPool.o:
1295 /localhome/hg/jdk9-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type
1296    ... (rest of output omitted)
1297 
1298 * All command lines available in /localhome/hg/jdk9-sandbox/build/linux-x64/make-support/failure-logs.
1299 === End of repeated output ===
1300 
1301 === Make failed targets repeated here ===
1302 lib/CompileJvm.gmk:207: recipe for target '/localhome/hg/jdk9-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed
1303 make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed
1304 === End of repeated output ===
1305 
1306 Hint: Try searching the build log for the name of the first failed target.
1307 Hint: If caused by a warning, try configure --disable-warnings-as-errors.
1308 ```
1309 
1310 Let's break it down! First, the selected configuration, and the top-level
1311 target you entered on the command line that caused the failure is printed.
1312 
1313 Then, between the `Output from failing command(s) repeated here` and `End of
1314 repeated output` the first lines of output (stdout and stderr) from the actual
1315 failing command is repeated. In most cases, this is the error message that
1316 caused the build to fail. If multiple commands were failing (this can happen in
1317 a parallel build), output from all failed commands will be printed here.
1318 
1319 The path to the `failure-logs` directory is printed. In this file you will find
1320 a `<target>.log` file that contains the output from this command in its
1321 entirety, and also a `<target>.cmd`, which contain the complete command line
1322 used for running this command. You can re-run the failing command by executing
1323 `. <path to failure-logs>/<target>.cmd` in your shell.
1324 
1325 Another way to trace the failure is to follow the chain of make targets, from
1326 top-level targets to individual file targets. Between `Make failed targets
1327 repeated here` and `End of repeated output` the output from make showing this
1328 chain is repeated. The first failed recipe will typically contain the full path
1329 to the file in question that failed to compile. Following lines will show a
1330 trace of make targets why we ended up trying to compile that file.
1331 
1332 Finally, some hints are given on how to locate the error in the complete log.
1333 In this example, we would try searching the log file for "`psMemoryPool.o`".
1334 Another way to quickly locate make errors in the log is to search for "`]
1335 Error`" or "`***`".
1336 
1337 Note that the build failure summary will only help you if the issue was a
1338 compilation failure or similar. If the problem is more esoteric, or is due to
1339 errors in the build machinery, you will likely get empty output logs, and `No
1340 indication of failed target found` instead of the make target chain.
1341 
1342 #### Checking the Build Log File
1343 
1344 The output (stdout and stderr) from the latest build is always stored in
1345 `$BUILD/build.log`. The previous build log is stored as `build.log.old`. This
1346 means that it is not necessary to redirect the build output yourself if you
1347 want to process it.
1348 
1349 You can increase the verbosity of the log file, by the `LOG` control variable
1350 to `make`. If you want to see the command lines used in compilations, use
1351 `LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug`
1352 or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g.
1353 `LOG=info,cmdlines`. The `debug` log level will show most shell commands
1354 executed by make, and `trace` will show all. Beware that both these log levels
1355 will produce a massive build log!
1356 
1357 ### Fixing Unexpected Build Failures
1358 
1359 Most of the time, the build will fail due to incorrect changes in the source
1360 code.
1361 
1362 Sometimes the build can fail with no apparent changes that have caused the
1363 failure. If this is the first time you are building OpenJDK on this particular
1364 computer, and the build fails, the problem is likely with your build
1365 environment. But even if you have previously built OpenJDK with success, and it
1366 now fails, your build environment might have changed (perhaps due to OS
1367 upgrades or similar). But most likely, such failures are due to problems with
1368 the incremental rebuild.
1369 
1370 #### Problems with the Build Environment
1371 
1372 Make sure your configuration is correct. Re-run `configure`, and look for any
1373 warnings. Warnings that appear in the middle of the `configure` output is also
1374 repeated at the end, after the summary. The entire log is stored in
1375 `$BUILD/configure.log`.
1376 
1377 Verify that the summary at the end looks correct. Are you indeed using the Boot
1378 JDK and native toolchain that you expect?
1379 
1380 By default, OpenJDK has a strict approach where warnings from the compiler is
1381 considered errors which fail the build. For very new or very old compiler
1382 versions, this can trigger new classes of warnings, which thus fails the build.
1383 Run `configure` with `--disable-warnings-as-errors` to turn of this behavior.
1384 (The warnings will still show, but not make the build fail.)
1385 
1386 #### Problems with Incremental Rebuilds
1387 
1388 Incremental rebuilds mean that when you modify part of the product, only the
1389 affected parts get rebuilt. While this works great in most cases, and
1390 significantly speed up the development process, from time to time complex
1391 interdependencies will result in an incorrect build result. This is the most
1392 common cause for unexpected build problems, together with inconsistencies
1393 between the different Mercurial repositories in the forest.
1394 
1395 Here are a suggested list of things to try if you are having unexpected build
1396 problems. Each step requires more time than the one before, so try them in
1397 order. Most issues will be solved at step 1 or 2.
1398 
1399  1. Make sure your forest is up-to-date
1400 
1401     Run `bash get_source.sh` to make sure you have the latest version of all
1402     repositories.
1403 
1404  2. Clean build results
1405 
1406     The simplest way to fix incremental rebuild issues is to run `make clean`.
1407     This will remove all build results, but not the configuration or any build
1408     system support artifacts. In most cases, this will solve build errors
1409     resulting from incremental build mismatches.
1410 
1411  3. Completely clean the build directory.
1412 
1413     If this does not work, the next step is to run `make dist-clean`, or
1414     removing the build output directory (`$BUILD`). This will clean all
1415     generated output, including your configuration. You will need to re-run
1416     `configure` after this step. A good idea is to run `make
1417     print-configuration` before running `make dist-clean`, as this will print
1418     your current `configure` command line. Here's a way to do this:
1419 
1420     ```
1421     make print-configuration > current-configuration
1422     make dist-clean
1423     bash configure $(cat current-configuration)
1424     make
1425     ```
1426 
1427  4. Re-clone the Mercurial forest
1428 
1429     Sometimes the Mercurial repositories themselves gets in a state that causes
1430     the product to be un-buildable. In such a case, the simplest solution is
1431     often the "sledgehammer approach": delete the entire forest, and re-clone
1432     it. If you have local changes, save them first to a different location
1433     using `hg export`.
1434 
1435 ### Specific Build Issues
1436 
1437 #### Clock Skew
1438 
1439 If you get an error message like this:
1440 ```
1441 File 'xxx' has modification time in the future.
1442 Clock skew detected. Your build may be incomplete.
1443 ```
1444 then the clock on your build machine is out of sync with the timestamps on the
1445 source files. Other errors, apparently unrelated but in fact caused by the
1446 clock skew, can occur along with the clock skew warnings. These secondary
1447 errors may tend to obscure the fact that the true root cause of the problem is
1448 an out-of-sync clock.
1449 
1450 If you see these warnings, reset the clock on the build machine, run `make
1451 clean` and restart the build.
1452 
1453 #### Out of Memory Errors
1454 
1455 On Solaris, you might get an error message like this:
1456 ```
1457 Trouble writing out table to disk
1458 ```
1459 To solve this, increase the amount of swap space on your build machine.
1460 
1461 On Windows, you might get error messages like this:
1462 ```
1463 fatal error - couldn't allocate heap
1464 cannot create ... Permission denied
1465 spawn failed
1466 ```
1467 This can be a sign of a Cygwin problem. See the information about solving
1468 problems in the [Cygwin](#cygwin) section. Rebooting the computer might help
1469 temporarily.
1470 
1471 ### Getting Help
1472 
1473 If none of the suggestions in this document helps you, or if you find what you
1474 believe is a bug in the build system, please contact the Build Group by sending
1475 a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net).
1476 Please include the relevant parts of the configure and/or build log.
1477 
1478 If you need general help or advice about developing for OpenJDK, you can also
1479 contact the Adoption Group. See the section on [Contributing to OpenJDK](
1480 #contributing-to-openjdk) for more information.
1481 
1482 ## Hints and Suggestions for Advanced Users
1483 
1484 ### Setting Up a Forest for Pushing Changes (defpath)
1485 
1486 To help you prepare a proper push path for a Mercurial repository, there exists
1487 a useful tool known as [defpath](
1488 http://openjdk.java.net/projects/code-tools/defpath). It will help you setup a
1489 proper push path for pushing changes to OpenJDK.
1490 
1491 Install the extension by cloning
1492 `http://hg.openjdk.java.net/code-tools/defpath` and updating your `.hgrc` file.
1493 Here's one way to do this:
1494 
1495 ```
1496 cd ~
1497 mkdir hg-ext
1498 cd hg-ext
1499 hg clone http://hg.openjdk.java.net/code-tools/defpath
1500 cat << EOT >> ~/.hgrc
1501 [extensions]
1502 defpath=~/hg-ext/defpath/defpath.py
1503 EOT
1504 ```
1505 
1506 You can now setup a proper push path using:
1507 ```
1508 hg defpath -d -u <your OpenJDK username>
1509 ```
1510 
1511 If you also have the `trees` extension installed in Mercurial, you will
1512 automatically get a `tdefpath` command, which is even more useful. By running
1513 `hg tdefpath -du <username>` in the top repository of your forest, all repos
1514 will get setup automatically. This is the recommended usage.
1515 
1516 ### Bash Completion
1517 
1518 The `configure` and `make` commands tries to play nice with bash command-line
1519 completion (using `<tab>` or `<tab><tab>`). To use this functionality, make
1520 sure you enable completion in your `~/.bashrc` (see instructions for bash in
1521 your operating system).
1522 
1523 Make completion will work out of the box, and will complete valid make targets.
1524 For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`.
1525 
1526 The `configure` script can get completion for options, but for this to work you
1527 need to help `bash` on the way. The standard way of running the script, `bash
1528 configure`, will not be understood by bash completion. You need `configure` to
1529 be the command to run. One way to achieve this is to add a simple helper script
1530 to your path:
1531 
1532 ```
1533 cat << EOT > /tmp/configure
1534 #!/bin/bash
1535 if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then
1536   echo >&2 "Abort: Trying to call configure helper recursively"
1537   exit 1
1538 fi
1539 
1540 bash \$PWD/configure "\$@"
1541 EOT
1542 chmod +x /tmp/configure
1543 sudo mv /tmp/configure /usr/local/bin
1544 ```
1545 
1546 Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`.
1547 
1548 ### Using Multiple Configurations
1549 
1550 You can have multiple configurations for a single source forest. When you
1551 create a new configuration, run `configure --with-conf-name=<name>` to create a
1552 configuration with the name `<name>`. Alternatively, you can create a directory
1553 under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd
1554 build/<name> && bash ../../configure`.
1555 
1556 Then you can build that configuration using `make CONF_NAME=<name>` or `make
1557 CONF=<pattern>`, where `<pattern>` is a substring matching one or several
1558 configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will
1559 match *all* available configuration, so `make CONF= hotspot` will build the
1560 `hotspot` target for all configurations. Alternatively, you can execute `make`
1561 in the configuration directory, e.g. `cd build/<name> && make`.
1562 
1563 ### Handling Reconfigurations
1564 
1565 If you update the forest and part of the configure script has changed, the
1566 build system will force you to re-run `configure`.
1567 
1568 Most of the time, you will be fine by running `configure` again with the same
1569 arguments as the last time, which can easily be performed by `make
1570 reconfigure`. To simplify this, you can use the `CONF_CHECK` make control
1571 variable, either as `make CONF_CHECK=auto`, or by setting an environment
1572 variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc`
1573 file, `make` will always run `reconfigure` automatically whenever the configure
1574 script has changed.
1575 
1576 You can also use `CONF_CHECK=ignore` to skip the check for a needed configure
1577 update. This might speed up the build, but comes at the risk of an incorrect
1578 build result. This is only recommended if you know what you're doing.
1579 
1580 From time to time, you will also need to modify the command line to `configure`
1581 due to changes. Use `make print-configure` to show the command line used for
1582 your current configuration.
1583 
1584 ### Using Fine-Grained Make Targets
1585 
1586 The default behavior for make is to create consistent and correct output, at
1587 the expense of build speed, if necessary.
1588 
1589 If you are prepared to take some risk of an incorrect build, and know enough of
1590 the system to understand how things build and interact, you can speed up the
1591 build process considerably by instructing make to only build a portion of the
1592 product.
1593 
1594 #### Building Individual Modules
1595 
1596 The safe way to use fine-grained make targets is to use the module specific
1597 make targets. All source code in JDK 9 is organized so it belongs to a module,
1598 e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific module, by
1599 giving it as make target: `make jdk.jdwp.agent`. If the specified module
1600 depends on other modules (e.g. `java.base`), those modules will be built first.
1601 
1602 You can also specify a set of modules, just as you can always specify a set of
1603 make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi
1604 jdk.crypto.ucrypto`
1605 
1606 #### Building Individual Module Phases
1607 
1608 The build process for each module is divided into separate phases. Not all
1609 modules need all phases. Which are needed depends on what kind of source code
1610 and other artifact the module consists of. The phases are:
1611 
1612   * `gensrc` (Generate source code to compile)
1613   * `gendata` (Generate non-source code artifacts)
1614   * `copy` (Copy resource artifacts)
1615   * `java` (Compile Java code)
1616   * `launchers` (Compile native executables)
1617   * `libs` (Compile native libraries)
1618   * `rmic` (Run the `rmic` tool)
1619 
1620 You can build only a single phase for a module by using the notation
1621 `$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`,
1622 use `make java.base-gensrc`.
1623 
1624 Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if
1625 present). Make will build all needed prerequisites before building the
1626 requested phase.
1627 
1628 #### Skipping the Dependency Check
1629 
1630 When using an iterative development style with frequent quick rebuilds, the
1631 dependency check made by make can take up a significant portion of the time
1632 spent on the rebuild. In such cases, it can be useful to bypass the dependency
1633 check in make.
1634 
1635 > **Note that if used incorrectly, this can lead to a broken build!**
1636 
1637 To achieve this, append `-only` to the build target. For instance, `make
1638 jdk.jdwp.agent-java-only` will *only* build the `java` phase of the
1639 `jdk.jdwp.agent` module. If the required dependencies are not present, the
1640 build can fail. On the other hand, the execution time measures in milliseconds.
1641 
1642 A useful pattern is to build the first time normally (e.g. `make
1643 jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target.
1644 
1645 #### Rebuilding Part of java.base (JDK\_FILTER)
1646 
1647 If you are modifying files in `java.base`, which is the by far largest module
1648 in OpenJDK, then you need to rebuild all those files whenever a single file has
1649 changed. (This inefficiency will hopefully be addressed in JDK 10.)
1650 
1651 As a hack, you can use the make control variable `JDK_FILTER` to specify a
1652 pattern that will be used to limit the set of files being recompiled. For
1653 instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods,
1654 `make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation
1655 to files in the `javax.crypto` package.
1656 
1657 ### Learn About Mercurial
1658 
1659 To become an efficient OpenJDK developer, it is recommended that you invest in
1660 learning Mercurial properly. Here are some links that can get you started:
1661 
1662   * [Mercurial for git users](http://www.mercurial-scm.org/wiki/GitConcepts)
1663   * [The official Mercurial tutorial](http://www.mercurial-scm.org/wiki/Tutorial)
1664   * [hg init](http://hginit.com/)
1665   * [Mercurial: The Definitive Guide](http://hgbook.red-bean.com/read/)
1666 
1667 ## Understanding the Build System
1668 
1669 This section will give you a more technical description on the details of the
1670 build system.
1671 
1672 ### Configurations
1673 
1674 The build system expects to find one or more configuration. These are
1675 technically defined by the `spec.gmk` in a subdirectory to the `build`
1676 subdirectory. The `spec.gmk` file is generated by `configure`, and contains in
1677 principle the configuration (directly or by files included by `spec.gmk`).
1678 
1679 You can, in fact, select a configuration to build by pointing to the `spec.gmk`
1680 file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`.
1681 While this is not the recommended way to call `make` as a user, it is what is
1682 used under the hood by the build system.
1683 
1684 ### Build Output Structure
1685 
1686 The build output for a configuration will end up in `build/<configuration
1687 name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory
1688 contains the following important directories:
1689 
1690 ```
1691 buildtools/
1692 configure-support/
1693 hotspot/
1694 images/
1695 jdk/
1696 make-support/
1697 support/
1698 test-results/
1699 test-support/
1700 ```
1701 
1702 This is what they are used for:
1703 
1704   * `images`: This is the directory were the output of the `*-image` make
1705     targets end up. For instance, `make jdk-image` ends up in `images/jdk`.
1706 
1707   * `jdk`: This is the "exploded image". After `make jdk`, you will be able to
1708     launch the newly built JDK by running `$BUILD/jdk/bin/java`.
1709 
1710   * `test-results`: This directory contains the results from running tests.
1711 
1712   * `support`: This is an area for intermediate files needed during the build,
1713     e.g. generated source code, object files and class files. Some noteworthy
1714     directories in `support` is `gensrc`, which contains the generated source
1715     code, and the `modules_*` directories, which contains the files in a
1716     per-module hierarchy that will later be collapsed into the `jdk` directory
1717     of the exploded image.
1718 
1719   * `buildtools`: This is an area for tools compiled for the build platform
1720     that are used during the rest of the build.
1721 
1722   * `hotspot`: This is an area for intermediate files needed when building
1723     hotspot.
1724 
1725   * `configure-support`, `make-support` and `test-support`: These directories
1726     contain files that are needed by the build system for `configure`, `make`
1727     and for running tests.
1728 
1729 ### Fixpath
1730 
1731 Windows path typically look like `C:\User\foo`, while Unix paths look like
1732 `/home/foo`. Tools with roots from Unix often experience issues related to this
1733 mismatch when running on Windows.
1734 
1735 In the OpenJDK build, we always use Unix paths internally, and only just before
1736 calling a tool that does not understand Unix paths do we convert them to
1737 Windows paths.
1738 
1739 This conversion is done by the `fixpath` tool, which is a small wrapper that
1740 modifies unix-style paths to Windows-style paths in command lines. Fixpath is
1741 compiled automatically by `configure`.
1742 
1743 ### Native Debug Symbols
1744 
1745 Native libraries and executables can have debug symbol (and other debug
1746 information) associated with them. How this works is very much platform
1747 dependent, but a common problem is that debug symbol information takes a lot of
1748 disk space, but is rarely needed by the end user.
1749 
1750 The OpenJDK supports different methods on how to handle debug symbols. The
1751 method used is selected by `--with-native-debug-symbols`, and available methods
1752 are `none`, `internal`, `external`, `zipped`.
1753 
1754   * `none` means that no debug symbols will be generated during the build.
1755 
1756   * `internal` means that debug symbols will be generated during the build, and
1757     they will be stored in the generated binary.
1758 
1759   * `external` means that debug symbols will be generated during the build, and
1760     after the compilation, they will be moved into a separate `.debuginfo` file.
1761     (This was previously known as FDS, Full Debug Symbols).
1762 
1763   * `zipped` is like `external`, but the .debuginfo file will also be zipped
1764     into a `.diz` file.
1765 
1766 When building for distribution, `zipped` is a good solution. Binaries built
1767 with `internal` is suitable for use by developers, since they facilitate
1768 debugging, but should be stripped before distributed to end users.
1769 
1770 ### Autoconf Details
1771 
1772 The `configure` script is based on the autoconf framework, but in some details
1773 deviate from a normal autoconf `configure` script.
1774 
1775 The `configure` script in the top level directory of OpenJDK is just a thin
1776 wrapper that calls `common/autoconf/configure`. This in turn provides
1777 functionality that is not easily expressed in the normal Autoconf framework,
1778 and then calls into the core of the `configure` script, which is the
1779 `common/autoconf/generated-configure.sh` file.
1780 
1781 As the name implies, this file is generated by Autoconf. It is checked in after
1782 regeneration, to alleviate the common user to have to install Autoconf.
1783 
1784 The build system will detect if the Autoconf source files have changed, and
1785 will trigger a regeneration of `common/autoconf/generated-configure.sh` if
1786 needed. You can also manually request such an update by `bash
1787 common/autoconf/autogen.sh`.
1788 
1789 If you make changes to the build system that requires a re-generation, note the
1790 following:
1791 
1792   * You must use *exactly* version 2.69 of autoconf for your patch to be
1793     accepted. This is to avoid spurious changes in the generated file. Note
1794     that Ubuntu 16.04 ships a patched version of autoconf which claims to be
1795     2.69, but is not.
1796 
1797   * You do not need to include the generated file in reviews.
1798 
1799   * If the generated file needs updating, the Oracle JDK closed counter-part
1800     will also need to be updated. It is very much appreciated if you ask for an
1801     Oracle engineer to sponsor your push so this can be made in tandem.
1802 
1803 ### Developing the Build System Itself
1804 
1805 This section contains a few remarks about how to develop for the build system
1806 itself. It is not relevant if you are only making changes in the product source
1807 code.
1808 
1809 While technically using `make`, the make source files of the OpenJDK does not
1810 resemble most other Makefiles. Instead of listing specific targets and actions
1811 (perhaps using patterns), the basic modus operandi is to call a high-level
1812 function (or properly, macro) from the API in `make/common`. For instance, to
1813 compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module,
1814 a call like this would be made:
1815 
1816 ```
1817 $(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \
1818     SETUP := GENERATE_OLDBYTECODE, \
1819     SRC := $(JDK_TOPDIR)/src/jkd.foo/share/classes, \
1820     INCLUDES := jdk/internal/foo, \
1821     BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \
1822 ))
1823 ```
1824 
1825 By encapsulating and expressing the high-level knowledge of *what* should be
1826 done, rather than *how* it should be done (as is normal in Makefiles), we can
1827 build a much more powerful and flexible build system.
1828 
1829 Correct dependency tracking is paramount. Sloppy dependency tracking will lead
1830 to improper parallelization, or worse, race conditions.
1831 
1832 To test for/debug race conditions, try running `make JOBS=1` and `make
1833 JOBS=100` and see if it makes any difference. (It shouldn't).
1834 
1835 To compare the output of two different builds and see if, and how, they differ,
1836 run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two
1837 builds you want to compare.
1838 
1839 To automatically build two consecutive versions and compare them, use
1840 `COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value
1841 assignments, like this:
1842 ```
1843 make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot
1844 ```
1845 See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`.
1846 
1847 To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`.
1848 Use `JOBS=1` to avoid parallelism.
1849 
1850 Please check that you adhere to the [Code Conventions for the Build System](
1851 http://openjdk.java.net/groups/build/doc/code-conventions.html) before
1852 submitting patches. Also see the section in [Autoconf Details](
1853 #autoconf-details) about the generated configure script.
1854 
1855 ## Contributing to OpenJDK
1856 
1857 So, now you've build your OpenJDK, and made your first patch, and want to
1858 contribute it back to the OpenJDK community.
1859 
1860 First of all: Thank you! We gladly welcome your contribution to the OpenJDK.
1861 However, please bear in mind that OpenJDK is a massive project, and we must ask
1862 you to follow our rules and guidelines to be able to accept your contribution.
1863 
1864 The official place to start is the ['How to contribute' page](
1865 http://openjdk.java.net/contribute/). There is also an official (but somewhat
1866 outdated and skimpy on details) [Developer's Guide](
1867 http://openjdk.java.net/guide/).
1868 
1869 If this seems overwhelming to you, the Adoption Group is there to help you! A
1870 good place to start is their ['New Contributor' page](
1871 https://wiki.openjdk.java.net/display/Adoption/New+Contributor), or start
1872 reading the comprehensive [Getting Started Kit](
1873 https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The
1874 Adoption Group will also happily answer any questions you have about
1875 contributing. Contact them by [mail](
1876 http://mail.openjdk.java.net/mailman/listinfo/adoption-discuss) or [IRC](
1877 http://openjdk.java.net/irc/).
1878 
1879 ---
1880 # Override styles from the base CSS file that are not ideal for this document.
1881 header-includes:
1882  - '<style type="text/css">pre, code, tt { color: #1d6ae5; }</style>'
1883 ---