1 % Building OpenJDK
   3 ## TL;DR (Instructions for the Impatient)
   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.
   9  1. [Get the complete source code](#getting-the-source-code): \
  10     `hg clone http://hg.openjdk.java.net/jdk/jdk`
  12  2. [Run configure](#running-configure): \
  13     `bash configure`
  15     If `configure` fails due to missing dependencies (to either the
  16     [toolchain](#native-compiler-toolchain-requirements), [build tools](
  17     #build-tools-requirements), [external libraries](
  18     #external-library-requirements) or the [boot JDK](#boot-jdk-requirements)),
  19     most of the time it prints a suggestion on how to resolve the situation on
  20     your platform. Follow the instructions, and try running `bash configure`
  21     again.
  23  3. [Run make](#running-make): \
  24     `make images`
  26  4. Verify your newly built JDK: \
  27     `./build/*/images/jdk/bin/java -version`
  29  5. [Run basic tests](##running-tests): \
  30     `make run-test-tier1`
  32 If any of these steps failed, or if you want to know more about build
  33 requirements or build functionality, please continue reading this document.
  35 ## Introduction
  37 OpenJDK is a complex software project. Building it requires a certain amount of
  38 technical expertise, a fair number of dependencies on external software, and
  39 reasonably powerful hardware.
  41 If you just want to use OpenJDK and not build it yourself, this document is not
  42 for you. See for instance [OpenJDK installation](
  43 http://openjdk.java.net/install) for some methods of installing a prebuilt
  44 OpenJDK.
  46 ## Getting the Source Code
  48 Make sure you are getting the correct version. As of JDK 10, the source is no
  49 longer split into separate repositories so you only need to clone one single
  50 repository. At the [OpenJDK Mercurial server](http://hg.openjdk.java.net/) you
  51 can see a list of all available forests. If you want to build an older version,
  52 e.g. JDK 8, it is recommended that you get the `jdk8u` forest, which contains
  53 incremental updates, instead of the `jdk8` forest, which was frozen at JDK 8 GA.
  55 If you are new to Mercurial, a good place to start is the [Mercurial Beginner's
  56 Guide](http://www.mercurial-scm.org/guide). The rest of this document assumes a
  57 working knowledge of Mercurial.
  59 ### Special Considerations
  61 For a smooth building experience, it is recommended that you follow these rules
  62 on where and how to check out the source code.
  64   * Do not check out the source code in a path which contains spaces. Chances
  65     are the build will not work. This is most likely to be an issue on Windows
  66     systems.
  68   * Do not check out the source code in a path which has a very long name or is
  69     nested many levels deep. Chances are you will hit an OS limitation during
  70     the build.
  72   * Put the source code on a local disk, not a network share. If possible, use
  73     an SSD. The build process is very disk intensive, and having slow disk
  74     access will significantly increase build times. If you need to use a
  75     network share for the source code, see below for suggestions on how to keep
  76     the build artifacts on a local disk.
  78   * On Windows, extra care must be taken to make sure the [Cygwin](#cygwin)
  79     environment is consistent. It is recommended that you follow this
  80     procedure:
  82       * Create the directory that is going to contain the top directory of the
  83         OpenJDK clone by using the `mkdir` command in the Cygwin bash shell.
  84         That is, do *not* create it using Windows Explorer. This will ensure
  85         that it will have proper Cygwin attributes, and that it's children will
  86         inherit those attributes.
  88       * Do not put the OpenJDK clone in a path under your Cygwin home
  89         directory. This is especially important if your user name contains
  90         spaces and/or mixed upper and lower case letters.
  92       * Clone the OpenJDK repository using the Cygwin command line `hg` client
  93         as instructed in this document. That is, do *not* use another Mercurial
  94         client such as TortoiseHg.
  96     Failure to follow this procedure might result in hard-to-debug build
  97     problems.
  99 ## Build Hardware Requirements
 101 OpenJDK is a massive project, and require machines ranging from decent to
 102 powerful to be able to build in a reasonable amount of time, or to be able to
 103 complete a build at all.
 105 We *strongly* recommend usage of an SSD disk for the build, since disk speed is
 106 one of the limiting factors for build performance.
 108 ### Building on x86
 110 At a minimum, a machine with 2-4 cores is advisable, as well as 2-4 GB of RAM.
 111 (The more cores to use, the more memory you need.) At least 6 GB of free disk
 112 space is required (8 GB minimum for building on Solaris).
 114 Even for 32-bit builds, it is recommended to use a 64-bit build machine, and
 115 instead create a 32-bit target using `--with-target-bits=32`.
 117 ### Building on sparc
 119 At a minimum, a machine with 4 cores is advisable, as well as 4 GB of RAM. (The
 120 more cores to use, the more memory you need.) At least 8 GB of free disk space
 121 is required.
 123 ### Building on arm/aarch64
 125 This is not recommended. Instead, see the section on [Cross-compiling](
 126 #cross-compiling).
 128 ## Operating System Requirements
 130 The mainline OpenJDK project supports Linux, Solaris, macOS, AIX and Windows.
 131 Support for other operating system, e.g. BSD, exists in separate "port"
 132 projects.
 134 In general, OpenJDK can be built on a wide range of versions of these operating
 135 systems, but the further you deviate from what is tested on a daily basis, the
 136 more likely you are to run into problems.
 138 This table lists the OS versions used by Oracle when building JDK 9. Such
 139 information is always subject to change, but this table is up to date at the
 140 time of writing.
 142  Operating system   Vendor/version used
 143  -----------------  -------------------------------------------------------
 144  Linux              Oracle Enterprise Linux 6.4 / 7.1 (using kernel 3.8.13)
 145  Solaris            Solaris 11.1 SRU 21.4.1 / 11.2 SRU 5.5
 146  macOS              Mac OS X 10.9 (Mavericks) / 10.10 (Yosemite)
 147  Windows            Windows Server 2012 R2
 149 The double version numbers for Linux, Solaris and macOS is due to the hybrid
 150 model used at Oracle, where header files and external libraries from an older
 151 version is used when building on a more modern version of the OS.
 153 The Build Group has a wiki page with [Supported Build Platforms](
 154 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms). From
 155 time to time, this is updated by the community to list successes or failures of
 156 building on different platforms.
 158 ### Windows
 160 Windows XP is not a supported platform, but all newer Windows should be able to
 161 build OpenJDK.
 163 On Windows, it is important that you pay attention to the instructions in the
 164 [Special Considerations](#special-considerations).
 166 Windows is the only non-POSIX OS supported by OpenJDK, and as such, requires
 167 some extra care. A POSIX support layer is required to build on Windows. For
 168 OpenJDK 9, the only supported such layer is Cygwin. (Msys is no longer
 169 supported due to a too old bash; msys2 and the new Windows Subsystem for Linux
 170 (WSL) would likely be possible to support in a future version but that would
 171 require a community effort to implement.)
 173 Internally in the build system, all paths are represented as Unix-style paths,
 174 e.g. `/cygdrive/c/hg/jdk9/Makefile` rather than `C:\hg\jdk9\Makefile`. This
 175 rule also applies to input to the build system, e.g. in arguments to
 176 `configure`. So, use `--with-freetype=/cygdrive/c/freetype` rather than
 177 `--with-freetype=c:\freetype`. For details on this conversion, see the section
 178 on [Fixpath](#fixpath).
 180 #### Cygwin
 182 A functioning [Cygwin](http://www.cygwin.com/) environment is thus required for
 183 building OpenJDK on Windows. If you have a 64-bit OS, we strongly recommend
 184 using the 64-bit version of Cygwin.
 186 **Note:** Cygwin has a model of continuously updating all packages without any
 187 easy way to install or revert to a specific version of a package. This means
 188 that whenever you add or update a package in Cygwin, you might (inadvertently)
 189 update tools that are used by the OpenJDK build process, and that can cause
 190 unexpected build problems.
 192 OpenJDK requires GNU Make 4.0 or greater on Windows. This is usually not a
 193 problem, since Cygwin currently only distributes GNU Make at a version above
 194 4.0.
 196 Apart from the basic Cygwin installation, the following packages must also be
 197 installed:
 199   * `autoconf`
 200   * `make`
 201   * `zip`
 202   * `unzip`
 204 Often, you can install these packages using the following command line:
 205 ```
 206 <path to Cygwin setup>/setup-x86_64 -q -P autoconf -P make -P unzip -P zip
 207 ```
 209 Unfortunately, Cygwin can be unreliable in certain circumstances. If you
 210 experience build tool crashes or strange issues when building on Windows,
 211 please check the Cygwin FAQ on the ["BLODA" list](
 212 https://cygwin.com/faq/faq.html#faq.using.bloda) and the section on [fork()
 213 failures](https://cygwin.com/faq/faq.html#faq.using.fixing-fork-failures).
 215 ### Solaris
 217 See `make/devkit/solaris11.1-package-list.txt` for a list of recommended
 218 packages to install when building on Solaris. The versions specified in this
 219 list is the versions used by the daily builds at Oracle, and is likely to work
 220 properly.
 222 Older versions of Solaris shipped a broken version of `objcopy`. At least
 223 version 2.21.1 is needed, which is provided by Solaris 11 Update 1. Objcopy is
 224 needed if you want to have external debug symbols. Please make sure you are
 225 using at least version 2.21.1 of objcopy, or that you disable external debug
 226 symbols.
 228 ### macOS
 230 Apple is using a quite aggressive scheme of pushing OS updates, and coupling
 231 these updates with required updates of Xcode. Unfortunately, this makes it
 232 difficult for a project like OpenJDK to keep pace with a continuously updated
 233 machine running macOS. See the section on [Apple Xcode](#apple-xcode) on some
 234 strategies to deal with this.
 236 It is recommended that you use at least Mac OS X 10.9 (Mavericks). At the time
 237 of writing, OpenJDK has been successfully compiled on macOS versions up to
 238 10.12.5 (Sierra), using XCode 8.3.2 and `--disable-warnings-as-errors`.
 240 The standard macOS environment contains the basic tooling needed to build, but
 241 for external libraries a package manager is recommended. OpenJDK uses
 242 [homebrew](https://brew.sh/) in the examples, but feel free to use whatever
 243 manager you want (or none).
 245 ### Linux
 247 It is often not much problem to build OpenJDK on Linux. The only general advice
 248 is to try to use the compilers, external libraries and header files as provided
 249 by your distribution.
 251 The basic tooling is provided as part of the core operating system, but you
 252 will most likely need to install developer packages.
 254 For apt-based distributions (Debian, Ubuntu, etc), try this:
 255 ```
 256 sudo apt-get install build-essential
 257 ```
 259 For rpm-based distributions (Fedora, Red Hat, etc), try this:
 260 ```
 261 sudo yum groupinstall "Development Tools"
 262 ```
 264 ### AIX
 266 The regular builds by SAP is using AIX version 7.1, but AIX 5.3 is also
 267 supported. See the [OpenJDK PowerPC Port Status Page](
 268 http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details.
 270 ## Native Compiler (Toolchain) Requirements
 272 Large portions of OpenJDK consists of native code, that needs to be compiled to
 273 be able to run on the target platform. In theory, toolchain and operating
 274 system should be independent factors, but in practice there's more or less a
 275 one-to-one correlation between target operating system and toolchain.
 277  Operating system   Supported toolchain
 278  ------------------ -------------------------
 279  Linux              gcc, clang
 280  macOS              Apple Xcode (using clang)
 281  Solaris            Oracle Solaris Studio
 282  AIX                IBM XL C/C++
 283  Windows            Microsoft Visual Studio
 285 Please see the individual sections on the toolchains for version
 286 recommendations. As a reference, these versions of the toolchains are used, at
 287 the time of writing, by Oracle for the daily builds of OpenJDK. It should be
 288 possible to compile OpenJDK with both older and newer versions, but the closer
 289 you stay to this list, the more likely you are to compile successfully without
 290 issues.
 292  Operating system   Toolchain version
 293  ------------------ -------------------------------------------------------
 294  Linux              gcc 4.9.2
 295  macOS              Apple Xcode 6.3 (using clang 6.1.0)
 296  Solaris            Oracle Solaris Studio 12.4 (with compiler version 5.13)
 297  Windows            Microsoft Visual Studio 2013 update 4
 299 ### gcc
 301 The minimum accepted version of gcc is 4.7. Older versions will generate a warning
 302 by `configure` and are unlikely to work.
 304 OpenJDK 9 includes patches that should allow gcc 6 to compile, but this should
 305 be considered experimental.
 307 In general, any version between these two should be usable.
 309 ### clang
 311 The minimum accepted version of clang is 3.2. Older versions will not be
 312 accepted by `configure`.
 314 To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`.
 316 ### Apple Xcode
 318 The oldest supported version of Xcode is 5.
 320 You will need the Xcode command lines developers tools to be able to build
 321 OpenJDK. (Actually, *only* the command lines tools are needed, not the IDE.)
 322 The simplest way to install these is to run:
 323 ```
 324 xcode-select --install
 325 ```
 327 It is advisable to keep an older version of Xcode for building OpenJDK when
 328 updating Xcode. This [blog page](
 329 http://iosdevelopertips.com/xcode/install-multiple-versions-of-xcode.html) has
 330 good suggestions on managing multiple Xcode versions. To use a specific version
 331 of Xcode, use `xcode-select -s` before running `configure`, or use
 332 `--with-toolchain-path` to point to the version of Xcode to use, e.g.
 333 `configure --with-toolchain-path=/Applications/Xcode5.app/Contents/Developer/usr/bin`
 335 If you have recently (inadvertently) updated your OS and/or Xcode version, and
 336 OpenJDK can no longer be built, please see the section on [Problems with the
 337 Build Environment](#problems-with-the-build-environment), and [Getting
 338 Help](#getting-help) to find out if there are any recent, non-merged patches
 339 available for this update.
 341 ### Oracle Solaris Studio
 343 The minimum accepted version of the Solaris Studio compilers is 5.13
 344 (corresponding to Solaris Studio 12.4). Older versions will not be accepted by
 345 configure.
 347 The Solaris Studio installation should contain at least these packages:
 349  Package                                            Version
 350  -------------------------------------------------- -------------
 351  developer/solarisstudio-124/backend                12.4-
 352  developer/solarisstudio-124/c++                    12.4-
 353  developer/solarisstudio-124/cc                     12.4-
 354  developer/solarisstudio-124/library/c++-libs       12.4-
 355  developer/solarisstudio-124/library/math-libs      12.4-
 356  developer/solarisstudio-124/library/studio-gccrt   12.4-
 357  developer/solarisstudio-124/studio-common          12.4-
 358  developer/solarisstudio-124/studio-ja              12.4-
 359  developer/solarisstudio-124/studio-legal           12.4-
 360  developer/solarisstudio-124/studio-zhCN            12.4-
 362 Compiling with Solaris Studio can sometimes be finicky. This is the exact
 363 version used by Oracle, which worked correctly at the time of writing:
 364 ```
 365 $ cc -V
 366 cc: Sun C 5.13 SunOS_i386 2014/10/20
 367 $ CC -V
 368 CC: Sun C++ 5.13 SunOS_i386 151846-10 2015/10/30
 369 ```
 371 ### Microsoft Visual Studio
 373 The minimum accepted version of Visual Studio is 2010. Older versions will not
 374 be accepted by `configure`. The maximum accepted version of Visual Studio is
 375 2013.
 377 If you have multiple versions of Visual Studio installed, `configure` will by
 378 default pick the latest. You can request a specific version to be used by
 379 setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2010`.
 381 If you get `LINK: fatal error LNK1123: failure during conversion to COFF: file
 382 invalid` when building using Visual Studio 2010, you have encountered
 383 [KB2757355](http://support.microsoft.com/kb/2757355), a bug triggered by a
 384 specific installation order. However, the solution suggested by the KB article
 385 does not always resolve the problem. See [this stackoverflow discussion](
 386 https://stackoverflow.com/questions/10888391) for other suggestions.
 388 ### IBM XL C/C++
 390 The regular builds by SAP is using version 12.1, described as `IBM XL C/C++ for
 391 AIX, V12.1 (5765-J02, 5725-C72) Version: 12.01.0000.0017`.
 393 See the [OpenJDK PowerPC Port Status Page](
 394 http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details.
 396 ## Boot JDK Requirements
 398 Paradoxically, building OpenJDK requires a pre-existing JDK. This is called the
 399 "boot JDK". The boot JDK does not have to be OpenJDK, though. If you are
 400 porting OpenJDK to a new platform, chances are that there already exists
 401 another JDK for that platform that is usable as boot JDK.
 403 The rule of thumb is that the boot JDK for building JDK major version *N*
 404 should be an JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be
 405 suitable as boot JDK. However, OpenJDK should be able to "build itself", so an
 406 up-to-date build of the current OpenJDK source is an acceptable alternative. If
 407 you are following the *N-1* rule, make sure you got the latest update version,
 408 since JDK 8 GA might not be able to build JDK 9 on all platforms.
 410 If the Boot JDK is not automatically detected, or the wrong JDK is picked, use
 411 `--with-boot-jdk` to point to the JDK to use.
 413 ### JDK 8 on Linux
 415 On apt-based distros (like Debian and Ubuntu), `sudo apt-get install
 416 openjdk-8-jdk` is typically enough to install OpenJDK 8. On rpm-based distros
 417 (like Fedora and Red Hat), try `sudo yum install java-1.8.0-openjdk-devel`.
 419 ### JDK 8 on Windows
 421 No pre-compiled binaries of OpenJDK 8 are readily available for Windows at the
 422 time of writing. An alternative is to download the [Oracle JDK](
 423 http://www.oracle.com/technetwork/java/javase/downloads). Another is the [Adopt
 424 OpenJDK Project](https://adoptopenjdk.net/), which publishes experimental
 425 prebuilt binaries for Windows.
 427 ### JDK 8 on macOS
 429 No pre-compiled binaries of OpenJDK 8 are readily available for macOS at the
 430 time of writing. An alternative is to download the [Oracle JDK](
 431 http://www.oracle.com/technetwork/java/javase/downloads), or to install it
 432 using `brew cask install java`. Another option is the [Adopt OpenJDK Project](
 433 https://adoptopenjdk.net/), which publishes experimental prebuilt binaries for
 434 macOS.
 436 ### JDK 8 on AIX
 438 No pre-compiled binaries of OpenJDK 8 are readily available for AIX at the
 439 time of writing. A starting point for working with OpenJDK on AIX is
 440 the [PowerPC/AIX Port Project](http://openjdk.java.net/projects/ppc-aix-port/).
 442 ## External Library Requirements
 444 Different platforms require different external libraries. In general, libraries
 445 are not optional - that is, they are either required or not used.
 447 If a required library is not detected by `configure`, you need to provide the
 448 path to it. There are two forms of the `configure` arguments to point to an
 449 external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to
 450 include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise,
 451 but require the include files an library files to reside in a default hierarchy
 452 under this directory. In most cases, it works fine.
 454 As a fallback, the second version allows you to point to the include directory
 455 and the lib directory separately.
 457 ### FreeType
 459 FreeType2 from [The FreeType Project](http://www.freetype.org/) is required on
 460 all platforms. At least version 2.3 is required.
 462   * To install on an apt-based Linux, try running `sudo apt-get install
 463     libcups2-dev`.
 464   * To install on an rpm-based Linux, try running `sudo yum install
 465     cups-devel`.
 466   * To install on Solaris, try running `pkg install system/library/freetype-2`.
 467   * To install on macOS, try running `brew install freetype`.
 468   * To install on Windows, see [below](#building-freetype-on-windows).
 470 Use `--with-freetype=<path>` if `configure` does not properly locate your
 471 FreeType files.
 473 #### Building FreeType on Windows
 475 On Windows, there is no readily available compiled version of FreeType. OpenJDK
 476 can help you compile FreeType from source. Download the FreeType sources and
 477 unpack them into an arbitrary directory:
 479 ```
 480 wget http://download.savannah.gnu.org/releases/freetype/freetype-2.5.3.tar.gz
 481 tar -xzf freetype-2.5.3.tar.gz
 482 ```
 484 Then run `configure` with `--with-freetype-src=<freetype_src>`. This will
 485 automatically build the freetype library into `<freetype_src>/lib64` for 64-bit
 486 builds or into `<freetype_src>/lib32` for 32-bit builds. Afterwards you can
 487 always use `--with-freetype-include=<freetype_src>/include` and
 488 `--with-freetype-lib=<freetype_src>/lib[32|64]` for other builds.
 490 Alternatively you can unpack the sources like this to use the default
 491 directory:
 493 ```
 494 tar --one-top-level=$HOME/freetype --strip-components=1 -xzf freetype-2.5.3.tar.gz
 495 ```
 497 ### CUPS
 499 CUPS, [Common UNIX Printing System](http://www.cups.org) header files are
 500 required on all platforms, except Windows. Often these files are provided by
 501 your operating system.
 503   * To install on an apt-based Linux, try running `sudo apt-get install
 504     libcups2-dev`.
 505   * To install on an rpm-based Linux, try running `sudo yum install
 506     cups-devel`.
 507   * To install on Solaris, try running `pkg install print/cups`.
 509 Use `--with-cups=<path>` if `configure` does not properly locate your CUPS
 510 files.
 512 ### X11
 514 Certain [X11](http://www.x.org/) libraries and include files are required on
 515 Linux and Solaris.
 517   * To install on an apt-based Linux, try running `sudo apt-get install
 518     libx11-dev libxext-dev libxrender-dev libxtst-dev libxt-dev`.
 519   * To install on an rpm-based Linux, try running `sudo yum install
 520     libXtst-devel libXt-devel libXrender-devel libXi-devel`.
 521   * To install on Solaris, try running `pkg install x11/header/x11-protocols
 522     x11/library/libice x11/library/libpthread-stubs x11/library/libsm
 523     x11/library/libx11 x11/library/libxau x11/library/libxcb
 524     x11/library/libxdmcp x11/library/libxevie x11/library/libxext
 525     x11/library/libxrender x11/library/libxscrnsaver x11/library/libxtst
 526     x11/library/toolkit/libxt`.
 528 Use `--with-x=<path>` if `configure` does not properly locate your X11 files.
 530 ### ALSA
 532 ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is
 533 required on Linux. At least version 0.9.1 of ALSA is required.
 535   * To install on an apt-based Linux, try running `sudo apt-get install
 536     libasound2-dev`.
 537   * To install on an rpm-based Linux, try running `sudo yum install
 538     alsa-lib-devel`.
 540 Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA
 541 files.
 543 ### libffi
 545 libffi, the [Portable Foreign Function Interface Library](
 546 http://sourceware.org/libffi) is required when building the Zero version of
 547 Hotspot.
 549   * To install on an apt-based Linux, try running `sudo apt-get install
 550     libffi-dev`.
 551   * To install on an rpm-based Linux, try running `sudo yum install
 552     libffi-devel`.
 554 Use `--with-libffi=<path>` if `configure` does not properly locate your libffi
 555 files.
 557 ## Build Tools Requirements
 559 ### Autoconf
 561 OpenJDK requires [Autoconf](http://www.gnu.org/software/autoconf) on all
 562 platforms. At least version 2.69 is required.
 564   * To install on an apt-based Linux, try running `sudo apt-get install
 565     autoconf`.
 566   * To install on an rpm-based Linux, try running `sudo yum install
 567     autoconf`.
 568   * To install on macOS, try running `brew install autoconf`.
 569   * To install on Windows, try running `<path to Cygwin setup>/setup-x86_64 -q
 570     -P autoconf`.
 572 If `configure` has problems locating your installation of autoconf, you can
 573 specify it using the `AUTOCONF` environment variable, like this:
 575 ```
 576 AUTOCONF=<path to autoconf> configure ...
 577 ```
 579 ### GNU Make
 581 OpenJDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors
 582 of make are supported.
 584 At least version 3.81 of GNU Make must be used. For distributions supporting
 585 GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful
 586 functionality to handle parallel building (supported by `--with-output-sync`)
 587 and speed and stability improvements.
 589 Note that `configure` locates and verifies a properly functioning version of
 590 `make` and stores the path to this `make` binary in the configuration. If you
 591 start a build using `make` on the command line, you will be using the version
 592 of make found first in your `PATH`, and not necessarily the one stored in the
 593 configuration. This initial make will be used as "bootstrap make", and in a
 594 second stage, the make located by `configure` will be called. Normally, this
 595 will present no issues, but if you have a very old `make`, or a non-GNU Make
 596 `make` in your path, this might cause issues.
 598 If you want to override the default make found by `configure`, use the `MAKE`
 599 configure variable, e.g. `configure MAKE=/opt/gnu/make`.
 601 On Solaris, it is common to call the GNU version of make by using `gmake`.
 603 ### GNU Bash
 605 OpenJDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells
 606 are supported.
 608 At least version 3.2 of GNU Bash must be used.
 610 ## Running Configure
 612 To build OpenJDK, you need a "configuration", which consists of a directory
 613 where to store the build output, coupled with information about the platform,
 614 the specific build machine, and choices that affect how OpenJDK is built.
 616 The configuration is created by the `configure` script. The basic invocation of
 617 the `configure` script looks like this:
 619 ```
 620 bash configure [options]
 621 ```
 623 This will create an output directory containing the configuration and setup an
 624 area for the build result. This directory typically looks like
 625 `build/linux-x64-normal-server-release`, but the actual name depends on your
 626 specific configuration. (It can also be set directly, see [Using Multiple
 627 Configurations](#using-multiple-configurations)). This directory is referred to
 628 as `$BUILD` in this documentation.
 630 `configure` will try to figure out what system you are running on and where all
 631 necessary build components are. If you have all prerequisites for building
 632 installed, it should find everything. If it fails to detect any component
 633 automatically, it will exit and inform you about the problem.
 635 Some command line examples:
 637   * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`:
 638     ```
 639     bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32
 640     ```
 642   * Create a debug build with the `server` JVM and DTrace enabled:
 643     ```
 644     bash configure --enable-debug --with-jvm-variants=server --enable-dtrace
 645     ```
 647 ### Common Configure Arguments
 649 Here follows some of the most common and important `configure` argument.
 651 To get up-to-date information on *all* available `configure` argument, please
 652 run:
 653 ```
 654 bash configure --help
 655 ```
 657 (Note that this help text also include general autoconf options, like
 658 `--dvidir`, that is not relevant to OpenJDK. To list only OpenJDK specific
 659 features, use `bash configure --help=short` instead.)
 661 #### Configure Arguments for Tailoring the Build
 663   * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand
 664     for `--with-debug-level=fastdebug`)
 665   * `--with-debug-level=<level>` - Set the debug level, which can be `release`,
 666     `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized`
 667     is variant of `release` with additional Hotspot debug code.
 668   * `--with-native-debug-symbols=<method>` - Specify if and how native debug
 669     symbols should be built. Available methods are `none`, `internal`,
 670     `external`, `zipped`. Default behavior depends on platform. See [Native
 671     Debug Symbols](#native-debug-symbols) for more details.
 672   * `--with-version-string=<string>` - Specify the version string this build
 673     will be identified with.
 674   * `--with-version-<part>=<value>` - A group of options, where `<part>` can be
 675     any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use
 676     these options to modify just the corresponding part of the version string
 677     from the default, or the value provided by `--with-version-string`.
 678   * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant
 679     (or variants) of Hotspot. Valid variants are: `server`, `client`,
 680     `minimal`, `core`, `zero`, `custom`. Note that not all
 681     variants are possible to combine in a single build.
 682   * `--with-jvm-features=<feature>[,<feature>...]` - Use the specified JVM
 683     features when building Hotspot. The list of features will be enabled on top
 684     of the default list. For the `custom` JVM variant, this default list is
 685     empty. A complete list of available JVM features can be found using `bash
 686     configure --help`.
 687   * `--with-target-bits=<bits>` - Create a target binary suitable for running
 688     on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build
 689     platform, instead of doing a full cross-compile. (This is known as a
 690     *reduced* build.)
 692 #### Configure Arguments for Native Compilation
 694   * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources
 695   * `--with-sysroot=<path>` - Use this directory as sysroot
 696   * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the
 697     default path when searching for all kinds of binaries
 698   * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when
 699     searching for toolchain binaries (compilers etc)
 700   * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C
 701     files
 702   * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++
 703     files
 704   * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK
 705     libraries
 707 #### Configure Arguments for External Dependencies
 709   * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK](
 710     #boot-jdk-requirements)
 711   * `--with-freetype=<path>` - Set the path to [FreeType](#freetype)
 712   * `--with-cups=<path>` - Set the path to [CUPS](#cups)
 713   * `--with-x=<path>` - Set the path to [X11](#x11)
 714   * `--with-alsa=<path>` - Set the path to [ALSA](#alsa)
 715   * `--with-libffi=<path>` - Set the path to [libffi](#libffi)
 716   * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests](
 717     #running-tests)
 719 Certain third-party libraries used by OpenJDK (libjpeg, giflib, libpng, lcms
 720 and zlib) are included in the OpenJDK repository. The default behavior of the
 721 OpenJDK build is to use this version of these libraries, but they might be
 722 replaced by an external version. To do so, specify `system` as the `<source>`
 723 option in these arguments. (The default is `bundled`).
 725   * `--with-libjpeg=<source>` - Use the specified source for libjpeg
 726   * `--with-giflib=<source>` - Use the specified source for giflib
 727   * `--with-libpng=<source>` - Use the specified source for libpng
 728   * `--with-lcms=<source>` - Use the specified source for lcms
 729   * `--with-zlib=<source>` - Use the specified source for zlib
 731 On Linux, it is possible to select either static or dynamic linking of the C++
 732 runtime. The default is static linking, with dynamic linking as fallback if the
 733 static library is not found.
 735   * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic`
 736     or `default`) for linking the C++ runtime.
 738 ### Configure Control Variables
 740 It is possible to control certain aspects of `configure` by overriding the
 741 value of `configure` variables, either on the command line or in the
 742 environment.
 744 Normally, this is **not recommended**. If used improperly, it can lead to a
 745 broken configuration. Unless you're well versed in the build system, this is
 746 hard to use properly. Therefore, `configure` will print a warning if this is
 747 detected.
 749 However, there are a few `configure` variables, known as *control variables*
 750 that are supposed to be overriden on the command line. These are variables that
 751 describe the location of tools needed by the build, like `MAKE` or `GREP`. If
 752 any such variable is specified, `configure` will use that value instead of
 753 trying to autodetect the tool. For instance, `bash configure
 754 MAKE=/opt/gnumake4.0/bin/make`.
 756 If a configure argument exists, use that instead, e.g. use `--with-jtreg`
 757 instead of setting `JTREGEXE`.
 759 Also note that, despite what autoconf claims, setting `CFLAGS` will not
 760 accomplish anything. Instead use `--with-extra-cflags` (and similar for
 761 `cxxflags` and `ldflags`).
 763 ## Running Make
 765 When you have a proper configuration, all you need to do to build OpenJDK is to
 766 run `make`. (But see the warning at [GNU Make](#gnu-make) about running the
 767 correct version of make.)
 769 When running `make` without any arguments, the default target is used, which is
 770 the same as running `make default` or `make jdk`. This will build a minimal (or
 771 roughly minimal) set of compiled output (known as an "exploded image") needed
 772 for a developer to actually execute the newly built JDK. The idea is that in an
 773 incremental development fashion, when doing a normal make, you should only
 774 spend time recompiling what's changed (making it purely incremental) and only
 775 do the work that's needed to actually run and test your code.
 777 The output of the exploded image resides in `$BUILD/jdk`. You can test the
 778 newly built JDK like this: `$BUILD/jdk/bin/java -version`.
 780 ### Common Make Targets
 782 Apart from the default target, here are some common make targets:
 784   * `hotspot` - Build all of hotspot (but only hotspot)
 785   * `hotspot-<variant>` - Build just the specified jvm variant
 786   * `images` or `product-images` - Build the JRE and JDK images
 787   * `docs` or `docs-image` - Build the documentation image
 788   * `test-image` - Build the test image
 789   * `all` or `all-images` - Build all images (product, docs and test)
 790   * `bootcycle-images` - Build images twice, second time with newly built JDK
 791     (good for testing)
 792   * `clean` - Remove all files generated by make, but not those generated by
 793     configure
 794   * `dist-clean` - Remove all files, including configuration
 796 Run `make help` to get an up-to-date list of important make targets and make
 797 control variables.
 799 It is possible to build just a single module, a single phase, or a single phase
 800 of a single module, by creating make targets according to these followin
 801 patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`,
 802 `launchers`, `libs` or `rmic`. See [Using Fine-Grained Make Targets](
 803 #using-fine-grained-make-targets) for more details about this functionality.
 805   * `<phase>` - Build the specified phase and everything it depends on
 806   * `<module>` - Build the specified module and everything it depends on
 807   * `<module>-<phase>` - Compile the specified phase for the specified module
 808     and everything it depends on
 810 Similarly, it is possible to clean just a part of the build by creating make
 811 targets according to these patterns:
 813   * `clean-<outputdir>` - Remove the subdir in the output dir with the name
 814   * `clean-<phase>` - Remove all build results related to a certain build
 815     phase
 816   * `clean-<module>` - Remove all build results related to a certain module
 817   * `clean-<module>-<phase>` - Remove all build results related to a certain
 818     module and phase
 820 ### Make Control Variables
 822 It is possible to control `make` behavior by overriding the value of `make`
 823 variables, either on the command line or in the environment.
 825 Normally, this is **not recommended**. If used improperly, it can lead to a
 826 broken build. Unless you're well versed in the build system, this is hard to
 827 use properly. Therefore, `make` will print a warning if this is detected.
 829 However, there are a few `make` variables, known as *control variables* that
 830 are supposed to be overriden on the command line. These make up the "make time"
 831 configuration, as opposed to the "configure time" configuration.
 833 #### General Make Control Variables
 835   * `JOBS` - Specify the number of jobs to build with. See [Build
 836     Performance](#build-performance).
 837   * `LOG` - Specify the logging level and functionality. See [Checking the
 838     Build Log File](#checking-the-build-log-file)
 839   * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using
 840     Multiple Configurations](#using-multiple-configurations)
 842 #### Test Make Control Variables
 844 These make control variables only make sense when running tests. Please see
 845 [Testing OpenJDK](testing.html) for details.
 847   * `TEST`
 848   * `TEST_JOBS`
 849   * `JTREG`
 850   * `GTEST`
 852 #### Advanced Make Control Variables
 854 These advanced make control variables can be potentially unsafe. See [Hints and
 855 Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and
 856 [Understanding the Build System](#understanding-the-build-system) for details.
 858   * `SPEC`
 859   * `CONF_CHECK`
 860   * `COMPARE_BUILD`
 861   * `JDK_FILTER`
 863 ## Running Tests
 865 Most of the OpenJDK tests are using the [JTReg](http://openjdk.java.net/jtreg)
 866 test framework. Make sure that your configuration knows where to find your
 867 installation of JTReg. If this is not picked up automatically, use the
 868 `--with-jtreg=<path to jtreg home>` option to point to the JTReg framework.
 869 Note that this option should point to the JTReg home, i.e. the top directory,
 870 containing `lib/jtreg.jar` etc.
 872 To execute the most basic tests (tier 1), use:
 873 ```
 874 make run-test-tier1
 875 ```
 877 For more details on how to run tests, please see the [Testing
 878 OpenJDK](testing.html) document.
 880 ## Cross-compiling
 882 Cross-compiling means using one platform (the *build* platform) to generate
 883 output that can ran on another platform (the *target* platform).
 885 The typical reason for cross-compiling is that the build is performed on a more
 886 powerful desktop computer, but the resulting binaries will be able to run on a
 887 different, typically low-performing system. Most of the complications that
 888 arise when building for embedded is due to this separation of *build* and
 889 *target* systems.
 891 This requires a more complex setup and build procedure. This section assumes
 892 you are familiar with cross-compiling in general, and will only deal with the
 893 particularities of cross-compiling OpenJDK. If you are new to cross-compiling,
 894 please see the [external links at Wikipedia](
 895 https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start
 896 on reading materials.
 898 Cross-compiling OpenJDK requires you to be able to build both for the build
 899 platform and for the target platform. The reason for the former is that we need
 900 to build and execute tools during the build process, both native tools and Java
 901 tools.
 903 If all you want to do is to compile a 32-bit version, for the same OS, on a
 904 64-bit machine, consider using `--with-target-bits=32` instead of doing a
 905 full-blown cross-compilation. (While this surely is possible, it's a lot more
 906 work and will take much longer to build.)
 908 ### Boot JDK and Build JDK
 910 When cross-compiling, make sure you use a boot JDK that runs on the *build*
 911 system, and not on the *target* system.
 913 To be able to build, we need a "Build JDK", which is a JDK built from the
 914 current sources (that is, the same as the end result of the entire build
 915 process), but able to run on the *build* system, and not the *target* system.
 916 (In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when
 917 building JDK 9.)
 919 The build process will create a minimal Build JDK for you, as part of building.
 920 To speed up the build, you can use `--with-build-jdk` to `configure` to point
 921 to a pre-built Build JDK. Please note that the build result is unpredictable,
 922 and can possibly break in subtle ways, if the Build JDK does not **exactly**
 923 match the current sources.
 925 ### Specifying the Target Platform
 927 You *must* specify the target platform when cross-compiling. Doing so will also
 928 automatically turn the build into a cross-compiling mode. The simplest way to
 929 do this is to use the `--openjdk-target` argument, e.g.
 930 `--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`.
 931 This will automatically set the `--build`, `--host` and `--target` options for
 932 autoconf, which can otherwise be confusing. (In autoconf terminology, the
 933 "target" is known as "host", and "target" is used for building a Canadian
 934 cross-compiler.)
 936 ### Toolchain Considerations
 938 You will need two copies of your toolchain, one which generates output that can
 939 run on the target system (the normal, or *target*, toolchain), and one that
 940 generates output that can run on the build system (the *build* toolchain). Note
 941 that cross-compiling is only supported for gcc at the time being. The gcc
 942 standard is to prefix cross-compiling toolchains with the target denominator.
 943 If you follow this standard, `configure` is likely to pick up the toolchain
 944 correctly.
 946 The *build* toolchain will be autodetected just the same way the normal
 947 *build*/*target* toolchain will be autodetected when not cross-compiling. If
 948 this is not what you want, or if the autodetection fails, you can specify a
 949 devkit containing the *build* toolchain using `--with-build-devkit` to
 950 `configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments.
 952 It is often helpful to locate the cross-compilation tools, headers and
 953 libraries in a separate directory, outside the normal path, and point out that
 954 directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and
 955 appending the directory when searching for cross-compilations tools
 956 (`--with-toolchain-path`). As a compact form, you can also use `--with-devkit`
 957 to point to a single directory, if it is correctly setup. (See `basics.m4` for
 958 details.)
 960 If you are unsure what toolchain and versions to use, these have been proved
 961 working at the time of writing:
 963   * [aarch64](
 964 https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-linux-gnu-4.8-2013.11_linux.tar.xz)
 965   * [arm 32-bit hardware floating  point](
 966 https://launchpad.net/linaro-toolchain-unsupported/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux.tar.bz2)
 968 ### Native Libraries
 970 You will need copies of external native libraries for the *target* system,
 971 present on the *build* machine while building.
 973 Take care not to replace the *build* system's version of these libraries by
 974 mistake, since that can render the *build* machine unusable.
 976 Make sure that the libraries you point to (ALSA, X11, etc) are for the
 977 *target*, not the *build*, platform.
 979 #### ALSA
 981 You will need alsa libraries suitable for your *target* system. For most cases,
 982 using Debian's pre-built libraries work fine.
 984 Note that alsa is needed even if you only want to build a headless JDK.
 986   * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and
 987     search for the `libasound2` and `libasound2-dev` packages for your *target*
 988     system. Download them to /tmp.
 990   * Install the libraries into the cross-compilation toolchain. For instance:
 991 ```
 992 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc
 993 dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb .
 994 dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb .
 995 ```
 997   * If alsa is not properly detected by `configure`, you can point it out by
 998     `--with-alsa`.
1000 #### X11
1002 You will need X11 libraries suitable for your *target* system. For most cases,
1003 using Debian's pre-built libraries work fine.
1005 Note that X11 is needed even if you only want to build a headless JDK.
1007   * Go to [Debian Package Search](https://www.debian.org/distrib/packages),
1008     search for the following packages for your *target* system, and download them
1009     to /tmp/target-x11:
1010       * libxi
1011       * libxi-dev
1012       * x11proto-core-dev
1013       * x11proto-input-dev
1014       * x11proto-kb-dev
1015       * x11proto-render-dev
1016       * x11proto-xext-dev
1017       * libice-dev
1018       * libxrender
1019       * libxrender-dev
1020       * libsm-dev
1021       * libxt-dev
1022       * libx11
1023       * libx11-dev
1024       * libxtst
1025       * libxtst-dev
1026       * libxext
1027       * libxext-dev
1029   * Install the libraries into the cross-compilation toolchain. For instance:
1030     ```
1031     cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr
1032     mkdir X11R6
1033     cd X11R6
1034     for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done
1035     mv usr/* .
1036     cd lib
1037     cp arm-linux-gnueabihf/* .
1038     ```
1040     You can ignore the following messages. These libraries are not needed to
1041     successfully complete a full JDK build.
1042     ```
1043     cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory
1044     cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory
1045     cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory
1046     ```
1048   * If the X11 libraries are not properly detected by `configure`, you can
1049     point them out by `--with-x`.
1051 ### Building for ARM/aarch64
1053 A common cross-compilation target is the ARM CPU. When building for ARM, it is
1054 useful to set the ABI profile. A number of pre-defined ABI profiles are
1055 available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt,
1056 armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer
1057 properly supported on OpenJDK.
1059 OpenJDK contains two different ports for the aarch64 platform, one is the
1060 original aarch64 port from the [AArch64 Port Project](
1061 http://openjdk.java.net/projects/aarch64-port) and one is a 64-bit version of
1062 the Oracle contributed ARM port. When targeting aarch64, by the default the
1063 original aarch64 port is used. To select the Oracle ARM 64 port, use
1064 `--with-cpu-port=arm64`. Also set the corresponding value (`aarch64` or
1065 `arm64`) to --with-abi-profile, to ensure a consistent build.
1067 ### Verifying the Build
1069 The build will end up in a directory named like
1070 `build/linux-arm-normal-server-release`.
1072 Inside this build output directory, the `images/jdk` and `images/jre` will
1073 contain the newly built JDK and JRE, respectively, for your *target* system.
1075 Copy these folders to your *target* system. Then you can run e.g.
1076 `images/jdk/bin/java -version`.
1078 ## Build Performance
1080 Building OpenJDK requires a lot of horsepower. Some of the build tools can be
1081 adjusted to utilize more or less of resources such as parallel threads and
1082 memory. The `configure` script analyzes your system and selects reasonable
1083 values for such options based on your hardware. If you encounter resource
1084 problems, such as out of memory conditions, you can modify the detected values
1085 with:
1087   * `--with-num-cores` -- number of cores in the build system, e.g.
1088     `--with-num-cores=8`.
1090   * `--with-memory-size` -- memory (in MB) available in the build system, e.g.
1091     `--with-memory-size=1024`
1093 You can also specify directly the number of build jobs to use with
1094 `--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag
1095 to `make`. In most cases it will be ignored by the makefiles, but it can cause
1096 problems for some make targets.
1098 It might also be necessary to specify the JVM arguments passed to the Boot JDK,
1099 using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the
1100 default JVM arguments passed to the Boot JDK.
1102 At the end of a successful execution of `configure`, you will get a performance
1103 summary, indicating how well the build will perform. Here you will also get
1104 performance hints. If you want to build fast, pay attention to those!
1106 If you want to tweak build performance, run with `make LOG=info` to get a build
1107 time summary at the end of the build process.
1109 ### Disk Speed
1111 If you are using network shares, e.g. via NFS, for your source code, make sure
1112 the build directory is situated on local disk (e.g. by `ln -s
1113 /localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely
1114 high for building on a network share; close to unusable.
1116 Also, make sure that your build tools (including Boot JDK and toolchain) is
1117 located on a local disk and not a network share.
1119 As has been stressed elsewhere, do use SSD for source code and build directory,
1120 as well as (if possible) the build tools.
1122 ### Virus Checking
1124 The use of virus checking software, especially on Windows, can *significantly*
1125 slow down building of OpenJDK. If possible, turn off such software, or exclude
1126 the directory containing the OpenJDK source code from on-the-fly checking.
1128 ### Ccache
1130 The OpenJDK build supports building with ccache when using gcc or clang. Using
1131 ccache can radically speed up compilation of native code if you often rebuild
1132 the same sources. Your milage may vary however, so we recommend evaluating it
1133 for yourself. To enable it, make sure it's on the path and configure with
1134 `--enable-ccache`.
1136 ### Precompiled Headers
1138 By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains
1139 were it is properly supported (clang, gcc, and Visual Studio). Normally, this
1140 speeds up the build process, but in some circumstances, it can actually slow
1141 things down.
1143 You can experiment by disabling precompiled headers using
1144 `--disable-precompiled-headers`.
1146 ### Icecc / icecream
1148 [icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a
1149 distributed compiler network. If you have multiple machines available for
1150 building OpenJDK, you can drastically cut individual build times by utilizing
1151 it.
1153 To use, setup an icecc network, and install icecc on the build machine. Then
1154 run `configure` using `--enable-icecc`.
1156 ### Using sjavac
1158 To speed up Java compilation, especially incremental compilations, you can try
1159 the experimental sjavac compiler by using `--enable-sjavac`.
1161 ### Building the Right Target
1163 Selecting the proper target to build can have dramatic impact on build time.
1164 For normal usage, `jdk` or the default target is just fine. You only need to
1165 build `images` for shipping, or if your tests require it.
1167 See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on
1168 how to build an even smaller subset of the product.
1170 ## Troubleshooting
1172 If your build fails, it can sometimes be difficult to pinpoint the problem or
1173 find a proper solution.
1175 ### Locating the Source of the Error
1177 When a build fails, it can be hard to pinpoint the actual cause of the error.
1178 In a typical build process, different parts of the product build in parallel,
1179 with the output interlaced.
1181 #### Build Failure Summary
1183 To help you, the build system will print a failure summary at the end. It looks
1184 like this:
1186 ```
1187 ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2)
1189 === Output from failing command(s) repeated here ===
1190 * For target hotspot_variant-server_libjvm_objs_psMemoryPool.o:
1191 /localhome/hg/jdk9-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type
1192    ... (rest of output omitted)
1194 * All command lines available in /localhome/hg/jdk9-sandbox/build/linux-x64/make-support/failure-logs.
1195 === End of repeated output ===
1197 === Make failed targets repeated here ===
1198 lib/CompileJvm.gmk:207: recipe for target '/localhome/hg/jdk9-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed
1199 make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed
1200 === End of repeated output ===
1202 Hint: Try searching the build log for the name of the first failed target.
1203 Hint: If caused by a warning, try configure --disable-warnings-as-errors.
1204 ```
1206 Let's break it down! First, the selected configuration, and the top-level
1207 target you entered on the command line that caused the failure is printed.
1209 Then, between the `Output from failing command(s) repeated here` and `End of
1210 repeated output` the first lines of output (stdout and stderr) from the actual
1211 failing command is repeated. In most cases, this is the error message that
1212 caused the build to fail. If multiple commands were failing (this can happen in
1213 a parallel build), output from all failed commands will be printed here.
1215 The path to the `failure-logs` directory is printed. In this file you will find
1216 a `<target>.log` file that contains the output from this command in its
1217 entirety, and also a `<target>.cmd`, which contain the complete command line
1218 used for running this command. You can re-run the failing command by executing
1219 `. <path to failure-logs>/<target>.cmd` in your shell.
1221 Another way to trace the failure is to follow the chain of make targets, from
1222 top-level targets to individual file targets. Between `Make failed targets
1223 repeated here` and `End of repeated output` the output from make showing this
1224 chain is repeated. The first failed recipe will typically contain the full path
1225 to the file in question that failed to compile. Following lines will show a
1226 trace of make targets why we ended up trying to compile that file.
1228 Finally, some hints are given on how to locate the error in the complete log.
1229 In this example, we would try searching the log file for "`psMemoryPool.o`".
1230 Another way to quickly locate make errors in the log is to search for "`]
1231 Error`" or "`***`".
1233 Note that the build failure summary will only help you if the issue was a
1234 compilation failure or similar. If the problem is more esoteric, or is due to
1235 errors in the build machinery, you will likely get empty output logs, and `No
1236 indication of failed target found` instead of the make target chain.
1238 #### Checking the Build Log File
1240 The output (stdout and stderr) from the latest build is always stored in
1241 `$BUILD/build.log`. The previous build log is stored as `build.log.old`. This
1242 means that it is not necessary to redirect the build output yourself if you
1243 want to process it.
1245 You can increase the verbosity of the log file, by the `LOG` control variable
1246 to `make`. If you want to see the command lines used in compilations, use
1247 `LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug`
1248 or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g.
1249 `LOG=info,cmdlines`. The `debug` log level will show most shell commands
1250 executed by make, and `trace` will show all. Beware that both these log levels
1251 will produce a massive build log!
1253 ### Fixing Unexpected Build Failures
1255 Most of the time, the build will fail due to incorrect changes in the source
1256 code.
1258 Sometimes the build can fail with no apparent changes that have caused the
1259 failure. If this is the first time you are building OpenJDK on this particular
1260 computer, and the build fails, the problem is likely with your build
1261 environment. But even if you have previously built OpenJDK with success, and it
1262 now fails, your build environment might have changed (perhaps due to OS
1263 upgrades or similar). But most likely, such failures are due to problems with
1264 the incremental rebuild.
1266 #### Problems with the Build Environment
1268 Make sure your configuration is correct. Re-run `configure`, and look for any
1269 warnings. Warnings that appear in the middle of the `configure` output is also
1270 repeated at the end, after the summary. The entire log is stored in
1271 `$BUILD/configure.log`.
1273 Verify that the summary at the end looks correct. Are you indeed using the Boot
1274 JDK and native toolchain that you expect?
1276 By default, OpenJDK has a strict approach where warnings from the compiler is
1277 considered errors which fail the build. For very new or very old compiler
1278 versions, this can trigger new classes of warnings, which thus fails the build.
1279 Run `configure` with `--disable-warnings-as-errors` to turn of this behavior.
1280 (The warnings will still show, but not make the build fail.)
1282 #### Problems with Incremental Rebuilds
1284 Incremental rebuilds mean that when you modify part of the product, only the
1285 affected parts get rebuilt. While this works great in most cases, and
1286 significantly speed up the development process, from time to time complex
1287 interdependencies will result in an incorrect build result. This is the most
1288 common cause for unexpected build problems, together with inconsistencies
1289 between the different Mercurial repositories in the forest.
1291 Here are a suggested list of things to try if you are having unexpected build
1292 problems. Each step requires more time than the one before, so try them in
1293 order. Most issues will be solved at step 1 or 2.
1295  1. Make sure your forest is up-to-date
1297     Run `bash get_source.sh` to make sure you have the latest version of all
1298     repositories.
1300  2. Clean build results
1302     The simplest way to fix incremental rebuild issues is to run `make clean`.
1303     This will remove all build results, but not the configuration or any build
1304     system support artifacts. In most cases, this will solve build errors
1305     resulting from incremental build mismatches.
1307  3. Completely clean the build directory.
1309     If this does not work, the next step is to run `make dist-clean`, or
1310     removing the build output directory (`$BUILD`). This will clean all
1311     generated output, including your configuration. You will need to re-run
1312     `configure` after this step. A good idea is to run `make
1313     print-configuration` before running `make dist-clean`, as this will print
1314     your current `configure` command line. Here's a way to do this:
1316     ```
1317     make print-configuration > current-configuration
1318     make dist-clean
1319     bash configure $(cat current-configuration)
1320     make
1321     ```
1323  4. Re-clone the Mercurial forest
1325     Sometimes the Mercurial repositories themselves gets in a state that causes
1326     the product to be un-buildable. In such a case, the simplest solution is
1327     often the "sledgehammer approach": delete the entire forest, and re-clone
1328     it. If you have local changes, save them first to a different location
1329     using `hg export`.
1331 ### Specific Build Issues
1333 #### Clock Skew
1335 If you get an error message like this:
1336 ```
1337 File 'xxx' has modification time in the future.
1338 Clock skew detected. Your build may be incomplete.
1339 ```
1340 then the clock on your build machine is out of sync with the timestamps on the
1341 source files. Other errors, apparently unrelated but in fact caused by the
1342 clock skew, can occur along with the clock skew warnings. These secondary
1343 errors may tend to obscure the fact that the true root cause of the problem is
1344 an out-of-sync clock.
1346 If you see these warnings, reset the clock on the build machine, run `make
1347 clean` and restart the build.
1349 #### Out of Memory Errors
1351 On Solaris, you might get an error message like this:
1352 ```
1353 Trouble writing out table to disk
1354 ```
1355 To solve this, increase the amount of swap space on your build machine.
1357 On Windows, you might get error messages like this:
1358 ```
1359 fatal error - couldn't allocate heap
1360 cannot create ... Permission denied
1361 spawn failed
1362 ```
1363 This can be a sign of a Cygwin problem. See the information about solving
1364 problems in the [Cygwin](#cygwin) section. Rebooting the computer might help
1365 temporarily.
1367 ### Getting Help
1369 If none of the suggestions in this document helps you, or if you find what you
1370 believe is a bug in the build system, please contact the Build Group by sending
1371 a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net).
1372 Please include the relevant parts of the configure and/or build log.
1374 If you need general help or advice about developing for OpenJDK, you can also
1375 contact the Adoption Group. See the section on [Contributing to OpenJDK](
1376 #contributing-to-openjdk) for more information.
1378 ## Hints and Suggestions for Advanced Users
1380 ### Setting Up a Forest for Pushing Changes (defpath)
1382 To help you prepare a proper push path for a Mercurial repository, there exists
1383 a useful tool known as [defpath](
1384 http://openjdk.java.net/projects/code-tools/defpath). It will help you setup a
1385 proper push path for pushing changes to OpenJDK.
1387 Install the extension by cloning
1388 `http://hg.openjdk.java.net/code-tools/defpath` and updating your `.hgrc` file.
1389 Here's one way to do this:
1391 ```
1392 cd ~
1393 mkdir hg-ext
1394 cd hg-ext
1395 hg clone http://hg.openjdk.java.net/code-tools/defpath
1396 cat << EOT >> ~/.hgrc
1397 [extensions]
1398 defpath=~/hg-ext/defpath/defpath.py
1399 EOT
1400 ```
1402 You can now setup a proper push path using:
1403 ```
1404 hg defpath -d -u <your OpenJDK username>
1405 ```
1407 If you also have the `trees` extension installed in Mercurial, you will
1408 automatically get a `tdefpath` command, which is even more useful. By running
1409 `hg tdefpath -du <username>` in the top repository of your forest, all repos
1410 will get setup automatically. This is the recommended usage.
1412 ### Bash Completion
1414 The `configure` and `make` commands tries to play nice with bash command-line
1415 completion (using `<tab>` or `<tab><tab>`). To use this functionality, make
1416 sure you enable completion in your `~/.bashrc` (see instructions for bash in
1417 your operating system).
1419 Make completion will work out of the box, and will complete valid make targets.
1420 For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`.
1422 The `configure` script can get completion for options, but for this to work you
1423 need to help `bash` on the way. The standard way of running the script, `bash
1424 configure`, will not be understood by bash completion. You need `configure` to
1425 be the command to run. One way to achieve this is to add a simple helper script
1426 to your path:
1428 ```
1429 cat << EOT > /tmp/configure
1430 #!/bin/bash
1431 if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then
1432   echo >&2 "Abort: Trying to call configure helper recursively"
1433   exit 1
1434 fi
1436 bash \$PWD/configure "\$@"
1437 EOT
1438 chmod +x /tmp/configure
1439 sudo mv /tmp/configure /usr/local/bin
1440 ```
1442 Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`.
1444 ### Using Multiple Configurations
1446 You can have multiple configurations for a single source forest. When you
1447 create a new configuration, run `configure --with-conf-name=<name>` to create a
1448 configuration with the name `<name>`. Alternatively, you can create a directory
1449 under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd
1450 build/<name> && bash ../../configure`.
1452 Then you can build that configuration using `make CONF_NAME=<name>` or `make
1453 CONF=<pattern>`, where `<pattern>` is a substring matching one or several
1454 configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will
1455 match *all* available configuration, so `make CONF= hotspot` will build the
1456 `hotspot` target for all configurations. Alternatively, you can execute `make`
1457 in the configuration directory, e.g. `cd build/<name> && make`.
1459 ### Handling Reconfigurations
1461 If you update the forest and part of the configure script has changed, the
1462 build system will force you to re-run `configure`.
1464 Most of the time, you will be fine by running `configure` again with the same
1465 arguments as the last time, which can easily be performed by `make
1466 reconfigure`. To simplify this, you can use the `CONF_CHECK` make control
1467 variable, either as `make CONF_CHECK=auto`, or by setting an environment
1468 variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc`
1469 file, `make` will always run `reconfigure` automatically whenever the configure
1470 script has changed.
1472 You can also use `CONF_CHECK=ignore` to skip the check for a needed configure
1473 update. This might speed up the build, but comes at the risk of an incorrect
1474 build result. This is only recommended if you know what you're doing.
1476 From time to time, you will also need to modify the command line to `configure`
1477 due to changes. Use `make print-configure` to show the command line used for
1478 your current configuration.
1480 ### Using Fine-Grained Make Targets
1482 The default behavior for make is to create consistent and correct output, at
1483 the expense of build speed, if necessary.
1485 If you are prepared to take some risk of an incorrect build, and know enough of
1486 the system to understand how things build and interact, you can speed up the
1487 build process considerably by instructing make to only build a portion of the
1488 product.
1490 #### Building Individual Modules
1492 The safe way to use fine-grained make targets is to use the module specific
1493 make targets. All source code in JDK 9 is organized so it belongs to a module,
1494 e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific module, by
1495 giving it as make target: `make jdk.jdwp.agent`. If the specified module
1496 depends on other modules (e.g. `java.base`), those modules will be built first.
1498 You can also specify a set of modules, just as you can always specify a set of
1499 make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi
1500 jdk.crypto.ucrypto`
1502 #### Building Individual Module Phases
1504 The build process for each module is divided into separate phases. Not all
1505 modules need all phases. Which are needed depends on what kind of source code
1506 and other artifact the module consists of. The phases are:
1508   * `gensrc` (Generate source code to compile)
1509   * `gendata` (Generate non-source code artifacts)
1510   * `copy` (Copy resource artifacts)
1511   * `java` (Compile Java code)
1512   * `launchers` (Compile native executables)
1513   * `libs` (Compile native libraries)
1514   * `rmic` (Run the `rmic` tool)
1516 You can build only a single phase for a module by using the notation
1517 `$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`,
1518 use `make java.base-gensrc`.
1520 Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if
1521 present). Make will build all needed prerequisites before building the
1522 requested phase.
1524 #### Skipping the Dependency Check
1526 When using an iterative development style with frequent quick rebuilds, the
1527 dependency check made by make can take up a significant portion of the time
1528 spent on the rebuild. In such cases, it can be useful to bypass the dependency
1529 check in make.
1531 > **Note that if used incorrectly, this can lead to a broken build!**
1533 To achieve this, append `-only` to the build target. For instance, `make
1534 jdk.jdwp.agent-java-only` will *only* build the `java` phase of the
1535 `jdk.jdwp.agent` module. If the required dependencies are not present, the
1536 build can fail. On the other hand, the execution time measures in milliseconds.
1538 A useful pattern is to build the first time normally (e.g. `make
1539 jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target.
1541 #### Rebuilding Part of java.base (JDK\_FILTER)
1543 If you are modifying files in `java.base`, which is the by far largest module
1544 in OpenJDK, then you need to rebuild all those files whenever a single file has
1545 changed. (This inefficiency will hopefully be addressed in JDK 10.)
1547 As a hack, you can use the make control variable `JDK_FILTER` to specify a
1548 pattern that will be used to limit the set of files being recompiled. For
1549 instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods,
1550 `make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation
1551 to files in the `javax.crypto` package.
1553 ### Learn About Mercurial
1555 To become an efficient OpenJDK developer, it is recommended that you invest in
1556 learning Mercurial properly. Here are some links that can get you started:
1558   * [Mercurial for git users](http://www.mercurial-scm.org/wiki/GitConcepts)
1559   * [The official Mercurial tutorial](http://www.mercurial-scm.org/wiki/Tutorial)
1560   * [hg init](http://hginit.com/)
1561   * [Mercurial: The Definitive Guide](http://hgbook.red-bean.com/read/)
1563 ## Understanding the Build System
1565 This section will give you a more technical description on the details of the
1566 build system.
1568 ### Configurations
1570 The build system expects to find one or more configuration. These are
1571 technically defined by the `spec.gmk` in a subdirectory to the `build`
1572 subdirectory. The `spec.gmk` file is generated by `configure`, and contains in
1573 principle the configuration (directly or by files included by `spec.gmk`).
1575 You can, in fact, select a configuration to build by pointing to the `spec.gmk`
1576 file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`.
1577 While this is not the recommended way to call `make` as a user, it is what is
1578 used under the hood by the build system.
1580 ### Build Output Structure
1582 The build output for a configuration will end up in `build/<configuration
1583 name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory
1584 contains the following important directories:
1586 ```
1587 buildtools/
1588 configure-support/
1589 hotspot/
1590 images/
1591 jdk/
1592 make-support/
1593 support/
1594 test-results/
1595 test-support/
1596 ```
1598 This is what they are used for:
1600   * `images`: This is the directory were the output of the `*-image` make
1601     targets end up. For instance, `make jdk-image` ends up in `images/jdk`.
1603   * `jdk`: This is the "exploded image". After `make jdk`, you will be able to
1604     launch the newly built JDK by running `$BUILD/jdk/bin/java`.
1606   * `test-results`: This directory contains the results from running tests.
1608   * `support`: This is an area for intermediate files needed during the build,
1609     e.g. generated source code, object files and class files. Some noteworthy
1610     directories in `support` is `gensrc`, which contains the generated source
1611     code, and the `modules_*` directories, which contains the files in a
1612     per-module hierarchy that will later be collapsed into the `jdk` directory
1613     of the exploded image.
1615   * `buildtools`: This is an area for tools compiled for the build platform
1616     that are used during the rest of the build.
1618   * `hotspot`: This is an area for intermediate files needed when building
1619     hotspot.
1621   * `configure-support`, `make-support` and `test-support`: These directories
1622     contain files that are needed by the build system for `configure`, `make`
1623     and for running tests.
1625 ### Fixpath
1627 Windows path typically look like `C:\User\foo`, while Unix paths look like
1628 `/home/foo`. Tools with roots from Unix often experience issues related to this
1629 mismatch when running on Windows.
1631 In the OpenJDK build, we always use Unix paths internally, and only just before
1632 calling a tool that does not understand Unix paths do we convert them to
1633 Windows paths.
1635 This conversion is done by the `fixpath` tool, which is a small wrapper that
1636 modifies unix-style paths to Windows-style paths in command lines. Fixpath is
1637 compiled automatically by `configure`.
1639 ### Native Debug Symbols
1641 Native libraries and executables can have debug symbol (and other debug
1642 information) associated with them. How this works is very much platform
1643 dependent, but a common problem is that debug symbol information takes a lot of
1644 disk space, but is rarely needed by the end user.
1646 The OpenJDK supports different methods on how to handle debug symbols. The
1647 method used is selected by `--with-native-debug-symbols`, and available methods
1648 are `none`, `internal`, `external`, `zipped`.
1650   * `none` means that no debug symbols will be generated during the build.
1652   * `internal` means that debug symbols will be generated during the build, and
1653     they will be stored in the generated binary.
1655   * `external` means that debug symbols will be generated during the build, and
1656     after the compilation, they will be moved into a separate `.debuginfo` file.
1657     (This was previously known as FDS, Full Debug Symbols).
1659   * `zipped` is like `external`, but the .debuginfo file will also be zipped
1660     into a `.diz` file.
1662 When building for distribution, `zipped` is a good solution. Binaries built
1663 with `internal` is suitable for use by developers, since they facilitate
1664 debugging, but should be stripped before distributed to end users.
1666 ### Autoconf Details
1668 The `configure` script is based on the autoconf framework, but in some details
1669 deviate from a normal autoconf `configure` script.
1671 The `configure` script in the top level directory of OpenJDK is just a thin
1672 wrapper that calls `make/autoconf/configure`. This in turn will run `autoconf`
1673 to create the runnable (generated) configure script, as
1674 `.build/generated-configure.sh`. Apart from being responsible for the
1675 generation of the runnable script, the `configure` script also provides
1676 functionality that is not easily expressed in the normal Autoconf framework. As
1677 part of this functionality, the generated script is called.
1679 The build system will detect if the Autoconf source files have changed, and
1680 will trigger a regeneration of the generated script if needed. You can also
1681 manually request such an update by `bash configure autogen`.
1683 In previous versions of the OpenJDK, the generated script was checked in at
1684 `make/autoconf/generated-configure.sh`. This is no longer the case.
1686 ### Developing the Build System Itself
1688 This section contains a few remarks about how to develop for the build system
1689 itself. It is not relevant if you are only making changes in the product source
1690 code.
1692 While technically using `make`, the make source files of the OpenJDK does not
1693 resemble most other Makefiles. Instead of listing specific targets and actions
1694 (perhaps using patterns), the basic modus operandi is to call a high-level
1695 function (or properly, macro) from the API in `make/common`. For instance, to
1696 compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module,
1697 a call like this would be made:
1699 ```
1700 $(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \
1702     SRC := $(TOPDIR)/src/jkd.foo/share/classes, \
1703     INCLUDES := jdk/internal/foo, \
1704     BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \
1705 ))
1706 ```
1708 By encapsulating and expressing the high-level knowledge of *what* should be
1709 done, rather than *how* it should be done (as is normal in Makefiles), we can
1710 build a much more powerful and flexible build system.
1712 Correct dependency tracking is paramount. Sloppy dependency tracking will lead
1713 to improper parallelization, or worse, race conditions.
1715 To test for/debug race conditions, try running `make JOBS=1` and `make
1716 JOBS=100` and see if it makes any difference. (It shouldn't).
1718 To compare the output of two different builds and see if, and how, they differ,
1719 run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two
1720 builds you want to compare.
1722 To automatically build two consecutive versions and compare them, use
1723 `COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value
1724 assignments, like this:
1725 ```
1726 make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot
1727 ```
1728 See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`.
1730 To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`.
1731 Use `JOBS=1` to avoid parallelism.
1733 Please check that you adhere to the [Code Conventions for the Build System](
1734 http://openjdk.java.net/groups/build/doc/code-conventions.html) before
1735 submitting patches.
1737 ## Contributing to OpenJDK
1739 So, now you've build your OpenJDK, and made your first patch, and want to
1740 contribute it back to the OpenJDK community.
1742 First of all: Thank you! We gladly welcome your contribution to the OpenJDK.
1743 However, please bear in mind that OpenJDK is a massive project, and we must ask
1744 you to follow our rules and guidelines to be able to accept your contribution.
1746 The official place to start is the ['How to contribute' page](
1747 http://openjdk.java.net/contribute/). There is also an official (but somewhat
1748 outdated and skimpy on details) [Developer's Guide](
1749 http://openjdk.java.net/guide/).
1751 If this seems overwhelming to you, the Adoption Group is there to help you! A
1752 good place to start is their ['New Contributor' page](
1753 https://wiki.openjdk.java.net/display/Adoption/New+Contributor), or start
1754 reading the comprehensive [Getting Started Kit](
1755 https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The
1756 Adoption Group will also happily answer any questions you have about
1757 contributing. Contact them by [mail](
1758 http://mail.openjdk.java.net/mailman/listinfo/adoption-discuss) or [IRC](
1759 http://openjdk.java.net/irc/).
1761 ---
1762 # Override styles from the base CSS file that are not ideal for this document.
1763 header-includes:
1764  - '<style type="text/css">pre, code, tt { color: #1d6ae5; }</style>'
1765 ---