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/jdk10/master`
  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), [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.
  22  3. [Run make](#running-make): \
  23     `make images`
  25  4. Verify your newly built JDK: \
  26     `./build/*/images/jdk/bin/java -version`
  28  5. [Run basic tests](##running-tests): \
  29     `make run-test-tier1`
  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.
  34 ## Introduction
  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.
  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.
  45 ## Getting the Source Code
  47 Make sure you are getting the correct version. As of JDK 10, the source is no
  48 longer split into separate repositories so you only need to clone one single
  49 repository. At the [OpenJDK Mercurial server](http://hg.openjdk.java.net/) you
  50 can see a list of all available forests. If you want to build an older version,
  51 e.g. JDK 8, it is recommended that you get the `jdk8u` forest, which contains
  52 incremental updates, instead of the `jdk8` forest, which was frozen at JDK 8 GA.
  54 If you are new to Mercurial, a good place to start is the [Mercurial Beginner's
  55 Guide](http://www.mercurial-scm.org/guide). The rest of this document assumes a
  56 working knowledge of Mercurial.
  58 ### Special Considerations
  60 For a smooth building experience, it is recommended that you follow these rules
  61 on where and how to check out the source code.
  63   * Do not check out the source code in a path which contains spaces. Chances
  64     are the build will not work. This is most likely to be an issue on Windows
  65     systems.
  67   * Do not check out the source code in a path which has a very long name or is
  68     nested many levels deep. Chances are you will hit an OS limitation during
  69     the build.
  71   * Put the source code on a local disk, not a network share. If possible, use
  72     an SSD. The build process is very disk intensive, and having slow disk
  73     access will significantly increase build times. If you need to use a
  74     network share for the source code, see below for suggestions on how to keep
  75     the build artifacts on a local disk.
  77   * On Windows, extra care must be taken to make sure the [Cygwin](#cygwin)
  78     environment is consistent. It is recommended that you follow this
  79     procedure:
  81       * Create the directory that is going to contain the top directory of the
  82         OpenJDK clone by using the `mkdir` command in the Cygwin bash shell.
  83         That is, do *not* create it using Windows Explorer. This will ensure
  84         that it will have proper Cygwin attributes, and that it's children will
  85         inherit those attributes.
  87       * Do not put the OpenJDK clone in a path under your Cygwin home
  88         directory. This is especially important if your user name contains
  89         spaces and/or mixed upper and lower case letters.
  91       * Clone the OpenJDK repository using the Cygwin command line `hg` client
  92         as instructed in this document. That is, do *not* use another Mercurial
  93         client such as TortoiseHg.
  95     Failure to follow this procedure might result in hard-to-debug build
  96     problems.
  98 ## Build Hardware Requirements
 100 OpenJDK is a massive project, and require machines ranging from decent to
 101 powerful to be able to build in a reasonable amount of time, or to be able to
 102 complete a build at all.
 104 We *strongly* recommend usage of an SSD disk for the build, since disk speed is
 105 one of the limiting factors for build performance.
 107 ### Building on x86
 109 At a minimum, a machine with 2-4 cores is advisable, as well as 2-4 GB of RAM.
 110 (The more cores to use, the more memory you need.) At least 6 GB of free disk
 111 space is required (8 GB minimum for building on Solaris).
 113 Even for 32-bit builds, it is recommended to use a 64-bit build machine, and
 114 instead create a 32-bit target using `--with-target-bits=32`.
 116 ### Building on sparc
 118 At a minimum, a machine with 4 cores is advisable, as well as 4 GB of RAM. (The
 119 more cores to use, the more memory you need.) At least 8 GB of free disk space
 120 is required.
 122 ### Building on arm/aarch64
 124 This is not recommended. Instead, see the section on [Cross-compiling](
 125 #cross-compiling).
 127 ## Operating System Requirements
 129 The mainline OpenJDK project supports Linux, Solaris, macOS, AIX and Windows.
 130 Support for other operating system, e.g. BSD, exists in separate "port"
 131 projects.
 133 In general, OpenJDK can be built on a wide range of versions of these operating
 134 systems, but the further you deviate from what is tested on a daily basis, the
 135 more likely you are to run into problems.
 137 This table lists the OS versions used by Oracle when building JDK 9. Such
 138 information is always subject to change, but this table is up to date at the
 139 time of writing.
 141  Operating system   Vendor/version used
 142  -----------------  -------------------------------------------------------
 143  Linux              Oracle Enterprise Linux 6.4 / 7.1 (using kernel 3.8.13)
 144  Solaris            Solaris 11.1 SRU 21.4.1 / 11.2 SRU 5.5
 145  macOS              Mac OS X 10.9 (Mavericks) / 10.10 (Yosemite)
 146  Windows            Windows Server 2012 R2
 148 The double version numbers for Linux, Solaris and macOS is due to the hybrid
 149 model used at Oracle, where header files and external libraries from an older
 150 version is used when building on a more modern version of the OS.
 152 The Build Group has a wiki page with [Supported Build Platforms](
 153 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms). From
 154 time to time, this is updated by the community to list successes or failures of
 155 building on different platforms.
 157 ### Windows
 159 Windows XP is not a supported platform, but all newer Windows should be able to
 160 build OpenJDK.
 162 On Windows, it is important that you pay attention to the instructions in the
 163 [Special Considerations](#special-considerations).
 165 Windows is the only non-POSIX OS supported by OpenJDK, and as such, requires
 166 some extra care. A POSIX support layer is required to build on Windows. For
 167 OpenJDK 9, the only supported such layer is Cygwin. (Msys is no longer
 168 supported due to a too old bash; msys2 and the new Windows Subsystem for Linux
 169 (WSL) would likely be possible to support in a future version but that would
 170 require a community effort to implement.)
 172 Internally in the build system, all paths are represented as Unix-style paths,
 173 e.g. `/cygdrive/c/hg/jdk9/Makefile` rather than `C:\hg\jdk9\Makefile`. This
 174 rule also applies to input to the build system, e.g. in arguments to
 175 `configure`. So, use `--with-freetype=/cygdrive/c/freetype` rather than
 176 `--with-freetype=c:\freetype`. For details on this conversion, see the section
 177 on [Fixpath](#fixpath).
 179 #### Cygwin
 181 A functioning [Cygwin](http://www.cygwin.com/) environment is thus required for
 182 building OpenJDK on Windows. If you have a 64-bit OS, we strongly recommend
 183 using the 64-bit version of Cygwin.
 185 **Note:** Cygwin has a model of continuously updating all packages without any
 186 easy way to install or revert to a specific version of a package. This means
 187 that whenever you add or update a package in Cygwin, you might (inadvertently)
 188 update tools that are used by the OpenJDK build process, and that can cause
 189 unexpected build problems.
 191 OpenJDK requires GNU Make 4.0 or greater on Windows. This is usually not a
 192 problem, since Cygwin currently only distributes GNU Make at a version above
 193 4.0.
 195 Apart from the basic Cygwin installation, the following packages must also be
 196 installed:
 198   * `make`
 199   * `zip`
 200   * `unzip`
 202 Often, you can install these packages using the following command line:
 203 ```
 204 <path to Cygwin setup>/setup-x86_64 -q -P make -P unzip -P zip
 205 ```
 207 Unfortunately, Cygwin can be unreliable in certain circumstances. If you
 208 experience build tool crashes or strange issues when building on Windows,
 209 please check the Cygwin FAQ on the ["BLODA" list](
 210 https://cygwin.com/faq/faq.html#faq.using.bloda) and the section on [fork()
 211 failures](https://cygwin.com/faq/faq.html#faq.using.fixing-fork-failures).
 213 ### Solaris
 215 See `make/devkit/solaris11.1-package-list.txt` for a list of recommended
 216 packages to install when building on Solaris. The versions specified in this
 217 list is the versions used by the daily builds at Oracle, and is likely to work
 218 properly.
 220 Older versions of Solaris shipped a broken version of `objcopy`. At least
 221 version 2.21.1 is needed, which is provided by Solaris 11 Update 1. Objcopy is
 222 needed if you want to have external debug symbols. Please make sure you are
 223 using at least version 2.21.1 of objcopy, or that you disable external debug
 224 symbols.
 226 ### macOS
 228 Apple is using a quite aggressive scheme of pushing OS updates, and coupling
 229 these updates with required updates of Xcode. Unfortunately, this makes it
 230 difficult for a project like OpenJDK to keep pace with a continuously updated
 231 machine running macOS. See the section on [Apple Xcode](#apple-xcode) on some
 232 strategies to deal with this.
 234 It is recommended that you use at least Mac OS X 10.9 (Mavericks). At the time
 235 of writing, OpenJDK has been successfully compiled on macOS versions up to
 236 10.12.5 (Sierra), using XCode 8.3.2 and `--disable-warnings-as-errors`.
 238 The standard macOS environment contains the basic tooling needed to build, but
 239 for external libraries a package manager is recommended. OpenJDK uses
 240 [homebrew](https://brew.sh/) in the examples, but feel free to use whatever
 241 manager you want (or none).
 243 ### Linux
 245 It is often not much problem to build OpenJDK on Linux. The only general advice
 246 is to try to use the compilers, external libraries and header files as provided
 247 by your distribution.
 249 The basic tooling is provided as part of the core operating system, but you
 250 will most likely need to install developer packages.
 252 For apt-based distributions (Debian, Ubuntu, etc), try this:
 253 ```
 254 sudo apt-get install build-essential
 255 ```
 257 For rpm-based distributions (Fedora, Red Hat, etc), try this:
 258 ```
 259 sudo yum groupinstall "Development Tools"
 260 ```
 262 ### AIX
 264 The regular builds by SAP is using AIX version 7.1, but AIX 5.3 is also
 265 supported. See the [OpenJDK PowerPC Port Status Page](
 266 http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details.
 268 ## Native Compiler (Toolchain) Requirements
 270 Large portions of OpenJDK consists of native code, that needs to be compiled to
 271 be able to run on the target platform. In theory, toolchain and operating
 272 system should be independent factors, but in practice there's more or less a
 273 one-to-one correlation between target operating system and toolchain.
 275  Operating system   Supported toolchain
 276  ------------------ -------------------------
 277  Linux              gcc, clang
 278  macOS              Apple Xcode (using clang)
 279  Solaris            Oracle Solaris Studio
 280  AIX                IBM XL C/C++
 281  Windows            Microsoft Visual Studio
 283 Please see the individual sections on the toolchains for version
 284 recommendations. As a reference, these versions of the toolchains are used, at
 285 the time of writing, by Oracle for the daily builds of OpenJDK. It should be
 286 possible to compile OpenJDK with both older and newer versions, but the closer
 287 you stay to this list, the more likely you are to compile successfully without
 288 issues.
 290  Operating system   Toolchain version
 291  ------------------ -------------------------------------------------------
 292  Linux              gcc 4.9.2
 293  macOS              Apple Xcode 6.3 (using clang 6.1.0)
 294  Solaris            Oracle Solaris Studio 12.4 (with compiler version 5.13)
 295  Windows            Microsoft Visual Studio 2013 update 4
 297 ### gcc
 299 The minimum accepted version of gcc is 4.7. Older versions will generate a warning
 300 by `configure` and are unlikely to work.
 302 OpenJDK 9 includes patches that should allow gcc 6 to compile, but this should
 303 be considered experimental.
 305 In general, any version between these two should be usable.
 307 ### clang
 309 The minimum accepted version of clang is 3.2. Older versions will not be
 310 accepted by `configure`.
 312 To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`.
 314 ### Apple Xcode
 316 The oldest supported version of Xcode is 5.
 318 You will need the Xcode command lines developers tools to be able to build
 319 OpenJDK. (Actually, *only* the command lines tools are needed, not the IDE.)
 320 The simplest way to install these is to run:
 321 ```
 322 xcode-select --install
 323 ```
 325 It is advisable to keep an older version of Xcode for building OpenJDK when
 326 updating Xcode. This [blog page](
 327 http://iosdevelopertips.com/xcode/install-multiple-versions-of-xcode.html) has
 328 good suggestions on managing multiple Xcode versions. To use a specific version
 329 of Xcode, use `xcode-select -s` before running `configure`, or use
 330 `--with-toolchain-path` to point to the version of Xcode to use, e.g.
 331 `configure --with-toolchain-path=/Applications/Xcode5.app/Contents/Developer/usr/bin`
 333 If you have recently (inadvertently) updated your OS and/or Xcode version, and
 334 OpenJDK can no longer be built, please see the section on [Problems with the
 335 Build Environment](#problems-with-the-build-environment), and [Getting
 336 Help](#getting-help) to find out if there are any recent, non-merged patches
 337 available for this update.
 339 ### Oracle Solaris Studio
 341 The minimum accepted version of the Solaris Studio compilers is 5.13
 342 (corresponding to Solaris Studio 12.4). Older versions will not be accepted by
 343 configure.
 345 The Solaris Studio installation should contain at least these packages:
 347  Package                                            Version
 348  -------------------------------------------------- -------------
 349  developer/solarisstudio-124/backend                12.4-
 350  developer/solarisstudio-124/c++                    12.4-
 351  developer/solarisstudio-124/cc                     12.4-
 352  developer/solarisstudio-124/library/c++-libs       12.4-
 353  developer/solarisstudio-124/library/math-libs      12.4-
 354  developer/solarisstudio-124/library/studio-gccrt   12.4-
 355  developer/solarisstudio-124/studio-common          12.4-
 356  developer/solarisstudio-124/studio-ja              12.4-
 357  developer/solarisstudio-124/studio-legal           12.4-
 358  developer/solarisstudio-124/studio-zhCN            12.4-
 360 Compiling with Solaris Studio can sometimes be finicky. This is the exact
 361 version used by Oracle, which worked correctly at the time of writing:
 362 ```
 363 $ cc -V
 364 cc: Sun C 5.13 SunOS_i386 2014/10/20
 365 $ CC -V
 366 CC: Sun C++ 5.13 SunOS_i386 151846-10 2015/10/30
 367 ```
 369 ### Microsoft Visual Studio
 371 The minimum accepted version of Visual Studio is 2010. Older versions will not
 372 be accepted by `configure`. The maximum accepted version of Visual Studio is
 373 2013.
 375 If you have multiple versions of Visual Studio installed, `configure` will by
 376 default pick the latest. You can request a specific version to be used by
 377 setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2010`.
 379 If you get `LINK: fatal error LNK1123: failure during conversion to COFF: file
 380 invalid` when building using Visual Studio 2010, you have encountered
 381 [KB2757355](http://support.microsoft.com/kb/2757355), a bug triggered by a
 382 specific installation order. However, the solution suggested by the KB article
 383 does not always resolve the problem. See [this stackoverflow discussion](
 384 https://stackoverflow.com/questions/10888391) for other suggestions.
 386 ### IBM XL C/C++
 388 The regular builds by SAP is using version 12.1, described as `IBM XL C/C++ for
 389 AIX, V12.1 (5765-J02, 5725-C72) Version: 12.01.0000.0017`.
 391 See the [OpenJDK PowerPC Port Status Page](
 392 http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details.
 394 ## Boot JDK Requirements
 396 Paradoxically, building OpenJDK requires a pre-existing JDK. This is called the
 397 "boot JDK". The boot JDK does not have to be OpenJDK, though. If you are
 398 porting OpenJDK to a new platform, chances are that there already exists
 399 another JDK for that platform that is usable as boot JDK.
 401 The rule of thumb is that the boot JDK for building JDK major version *N*
 402 should be an JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be
 403 suitable as boot JDK. However, OpenJDK should be able to "build itself", so an
 404 up-to-date build of the current OpenJDK source is an acceptable alternative. If
 405 you are following the *N-1* rule, make sure you got the latest update version,
 406 since JDK 8 GA might not be able to build JDK 9 on all platforms.
 408 If the Boot JDK is not automatically detected, or the wrong JDK is picked, use
 409 `--with-boot-jdk` to point to the JDK to use.
 411 ### JDK 8 on Linux
 413 On apt-based distros (like Debian and Ubuntu), `sudo apt-get install
 414 openjdk-8-jdk` is typically enough to install OpenJDK 8. On rpm-based distros
 415 (like Fedora and Red Hat), try `sudo yum install java-1.8.0-openjdk-devel`.
 417 ### JDK 8 on Windows
 419 No pre-compiled binaries of OpenJDK 8 are readily available for Windows at the
 420 time of writing. An alternative is to download the [Oracle JDK](
 421 http://www.oracle.com/technetwork/java/javase/downloads). Another is the [Adopt
 422 OpenJDK Project](https://adoptopenjdk.net/), which publishes experimental
 423 prebuilt binaries for Windows.
 425 ### JDK 8 on macOS
 427 No pre-compiled binaries of OpenJDK 8 are readily available for macOS at the
 428 time of writing. An alternative is to download the [Oracle JDK](
 429 http://www.oracle.com/technetwork/java/javase/downloads), or to install it
 430 using `brew cask install java`. Another option is the [Adopt OpenJDK Project](
 431 https://adoptopenjdk.net/), which publishes experimental prebuilt binaries for
 432 macOS.
 434 ### JDK 8 on AIX
 436 No pre-compiled binaries of OpenJDK 8 are readily available for AIX at the
 437 time of writing. A starting point for working with OpenJDK on AIX is
 438 the [PowerPC/AIX Port Project](http://openjdk.java.net/projects/ppc-aix-port/).
 440 ## External Library Requirements
 442 Different platforms require different external libraries. In general, libraries
 443 are not optional - that is, they are either required or not used.
 445 If a required library is not detected by `configure`, you need to provide the
 446 path to it. There are two forms of the `configure` arguments to point to an
 447 external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to
 448 include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise,
 449 but require the include files an library files to reside in a default hierarchy
 450 under this directory. In most cases, it works fine.
 452 As a fallback, the second version allows you to point to the include directory
 453 and the lib directory separately.
 455 ### FreeType
 457 FreeType2 from [The FreeType Project](http://www.freetype.org/) is required on
 458 all platforms. At least version 2.3 is required.
 460   * To install on an apt-based Linux, try running `sudo apt-get install
 461     libcups2-dev`.
 462   * To install on an rpm-based Linux, try running `sudo yum install
 463     cups-devel`.
 464   * To install on Solaris, try running `pkg install system/library/freetype-2`.
 465   * To install on macOS, try running `brew install freetype`.
 466   * To install on Windows, see [below](#building-freetype-on-windows).
 468 Use `--with-freetype=<path>` if `configure` does not properly locate your
 469 FreeType files.
 471 #### Building FreeType on Windows
 473 On Windows, there is no readily available compiled version of FreeType. OpenJDK
 474 can help you compile FreeType from source. Download the FreeType sources and
 475 unpack them into an arbitrary directory:
 477 ```
 478 wget http://download.savannah.gnu.org/releases/freetype/freetype-2.5.3.tar.gz
 479 tar -xzf freetype-2.5.3.tar.gz
 480 ```
 482 Then run `configure` with `--with-freetype-src=<freetype_src>`. This will
 483 automatically build the freetype library into `<freetype_src>/lib64` for 64-bit
 484 builds or into `<freetype_src>/lib32` for 32-bit builds. Afterwards you can
 485 always use `--with-freetype-include=<freetype_src>/include` and
 486 `--with-freetype-lib=<freetype_src>/lib[32|64]` for other builds.
 488 Alternatively you can unpack the sources like this to use the default
 489 directory:
 491 ```
 492 tar --one-top-level=$HOME/freetype --strip-components=1 -xzf freetype-2.5.3.tar.gz
 493 ```
 495 ### CUPS
 497 CUPS, [Common UNIX Printing System](http://www.cups.org) header files are
 498 required on all platforms, except Windows. Often these files are provided by
 499 your operating system.
 501   * To install on an apt-based Linux, try running `sudo apt-get install
 502     libcups2-dev`.
 503   * To install on an rpm-based Linux, try running `sudo yum install
 504     cups-devel`.
 505   * To install on Solaris, try running `pkg install print/cups`.
 507 Use `--with-cups=<path>` if `configure` does not properly locate your CUPS
 508 files.
 510 ### X11
 512 Certain [X11](http://www.x.org/) libraries and include files are required on
 513 Linux and Solaris.
 515   * To install on an apt-based Linux, try running `sudo apt-get install
 516     libx11-dev libxext-dev libxrender-dev libxtst-dev libxt-dev`.
 517   * To install on an rpm-based Linux, try running `sudo yum install
 518     libXtst-devel libXt-devel libXrender-devel libXi-devel`.
 519   * To install on Solaris, try running `pkg install x11/header/x11-protocols
 520     x11/library/libice x11/library/libpthread-stubs x11/library/libsm
 521     x11/library/libx11 x11/library/libxau x11/library/libxcb
 522     x11/library/libxdmcp x11/library/libxevie x11/library/libxext
 523     x11/library/libxrender x11/library/libxscrnsaver x11/library/libxtst
 524     x11/library/toolkit/libxt`.
 526 Use `--with-x=<path>` if `configure` does not properly locate your X11 files.
 528 ### ALSA
 530 ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is
 531 required on Linux. At least version 0.9.1 of ALSA is required.
 533   * To install on an apt-based Linux, try running `sudo apt-get install
 534     libasound2-dev`.
 535   * To install on an rpm-based Linux, try running `sudo yum install
 536     alsa-lib-devel`.
 538 Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA
 539 files.
 541 ### libffi
 543 libffi, the [Portable Foreign Function Interface Library](
 544 http://sourceware.org/libffi) is required when building the Zero version of
 545 Hotspot.
 547   * To install on an apt-based Linux, try running `sudo apt-get install
 548     libffi-dev`.
 549   * To install on an rpm-based Linux, try running `sudo yum install
 550     libffi-devel`.
 552 Use `--with-libffi=<path>` if `configure` does not properly locate your libffi
 553 files.
 555 ## Other Tooling Requirements
 557 ### GNU Make
 559 OpenJDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors
 560 of make are supported.
 562 At least version 3.81 of GNU Make must be used. For distributions supporting
 563 GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful
 564 functionality to handle parallel building (supported by `--with-output-sync`)
 565 and speed and stability improvements.
 567 Note that `configure` locates and verifies a properly functioning version of
 568 `make` and stores the path to this `make` binary in the configuration. If you
 569 start a build using `make` on the command line, you will be using the version
 570 of make found first in your `PATH`, and not necessarily the one stored in the
 571 configuration. This initial make will be used as "bootstrap make", and in a
 572 second stage, the make located by `configure` will be called. Normally, this
 573 will present no issues, but if you have a very old `make`, or a non-GNU Make
 574 `make` in your path, this might cause issues.
 576 If you want to override the default make found by `configure`, use the `MAKE`
 577 configure variable, e.g. `configure MAKE=/opt/gnu/make`.
 579 On Solaris, it is common to call the GNU version of make by using `gmake`.
 581 ### GNU Bash
 583 OpenJDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells
 584 are supported.
 586 At least version 3.2 of GNU Bash must be used.
 588 ### Autoconf
 590 If you want to modify the build system itself, you need to install [Autoconf](
 591 http://www.gnu.org/software/autoconf).
 593 However, if you only need to build OpenJDK or if you only edit the actual
 594 OpenJDK source files, there is no dependency on autoconf, since the source
 595 distribution includes a pre-generated `configure` shell script.
 597 See the section on [Autoconf Details](#autoconf-details) for details on how
 598 OpenJDK uses autoconf. This is especially important if you plan to contribute
 599 changes to OpenJDK that modifies the build system.
 601 ## Running Configure
 603 To build OpenJDK, you need a "configuration", which consists of a directory
 604 where to store the build output, coupled with information about the platform,
 605 the specific build machine, and choices that affect how OpenJDK is built.
 607 The configuration is created by the `configure` script. The basic invocation of
 608 the `configure` script looks like this:
 610 ```
 611 bash configure [options]
 612 ```
 614 This will create an output directory containing the configuration and setup an
 615 area for the build result. This directory typically looks like
 616 `build/linux-x64-normal-server-release`, but the actual name depends on your
 617 specific configuration. (It can also be set directly, see [Using Multiple
 618 Configurations](#using-multiple-configurations)). This directory is referred to
 619 as `$BUILD` in this documentation.
 621 `configure` will try to figure out what system you are running on and where all
 622 necessary build components are. If you have all prerequisites for building
 623 installed, it should find everything. If it fails to detect any component
 624 automatically, it will exit and inform you about the problem.
 626 Some command line examples:
 628   * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`:
 629     ```
 630     bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32
 631     ```
 633   * Create a debug build with the `server` JVM and DTrace enabled:
 634     ```
 635     bash configure --enable-debug --with-jvm-variants=server --enable-dtrace
 636     ```
 638 ### Common Configure Arguments
 640 Here follows some of the most common and important `configure` argument.
 642 To get up-to-date information on *all* available `configure` argument, please
 643 run:
 644 ```
 645 bash configure --help
 646 ```
 648 (Note that this help text also include general autoconf options, like
 649 `--dvidir`, that is not relevant to OpenJDK. To list only OpenJDK specific
 650 features, use `bash configure --help=short` instead.)
 652 #### Configure Arguments for Tailoring the Build
 654   * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand
 655     for `--with-debug-level=fastdebug`)
 656   * `--with-debug-level=<level>` - Set the debug level, which can be `release`,
 657     `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized`
 658     is variant of `release` with additional Hotspot debug code.
 659   * `--with-native-debug-symbols=<method>` - Specify if and how native debug
 660     symbols should be built. Available methods are `none`, `internal`,
 661     `external`, `zipped`. Default behavior depends on platform. See [Native
 662     Debug Symbols](#native-debug-symbols) for more details.
 663   * `--with-version-string=<string>` - Specify the version string this build
 664     will be identified with.
 665   * `--with-version-<part>=<value>` - A group of options, where `<part>` can be
 666     any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use
 667     these options to modify just the corresponding part of the version string
 668     from the default, or the value provided by `--with-version-string`.
 669   * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant
 670     (or variants) of Hotspot. Valid variants are: `server`, `client`,
 671     `minimal`, `core`, `zero`, `custom`. Note that not all
 672     variants are possible to combine in a single build.
 673   * `--with-jvm-features=<feature>[,<feature>...]` - Use the specified JVM
 674     features when building Hotspot. The list of features will be enabled on top
 675     of the default list. For the `custom` JVM variant, this default list is
 676     empty. A complete list of available JVM features can be found using `bash
 677     configure --help`.
 678   * `--with-target-bits=<bits>` - Create a target binary suitable for running
 679     on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build
 680     platform, instead of doing a full cross-compile. (This is known as a
 681     *reduced* build.)
 683 #### Configure Arguments for Native Compilation
 685   * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources
 686   * `--with-sysroot=<path>` - Use this directory as sysroot
 687   * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the
 688     default path when searching for all kinds of binaries
 689   * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when
 690     searching for toolchain binaries (compilers etc)
 691   * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C
 692     files
 693   * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++
 694     files
 695   * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK
 696     libraries
 698 #### Configure Arguments for External Dependencies
 700   * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK](
 701     #boot-jdk-requirements)
 702   * `--with-freetype=<path>` - Set the path to [FreeType](#freetype)
 703   * `--with-cups=<path>` - Set the path to [CUPS](#cups)
 704   * `--with-x=<path>` - Set the path to [X11](#x11)
 705   * `--with-alsa=<path>` - Set the path to [ALSA](#alsa)
 706   * `--with-libffi=<path>` - Set the path to [libffi](#libffi)
 707   * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests](
 708     #running-tests)
 710 Certain third-party libraries used by OpenJDK (libjpeg, giflib, libpng, lcms
 711 and zlib) are included in the OpenJDK repository. The default behavior of the
 712 OpenJDK build is to use this version of these libraries, but they might be
 713 replaced by an external version. To do so, specify `system` as the `<source>`
 714 option in these arguments. (The default is `bundled`).
 716   * `--with-libjpeg=<source>` - Use the specified source for libjpeg
 717   * `--with-giflib=<source>` - Use the specified source for giflib
 718   * `--with-libpng=<source>` - Use the specified source for libpng
 719   * `--with-lcms=<source>` - Use the specified source for lcms
 720   * `--with-zlib=<source>` - Use the specified source for zlib
 722 On Linux, it is possible to select either static or dynamic linking of the C++
 723 runtime. The default is static linking, with dynamic linking as fallback if the
 724 static library is not found.
 726   * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic`
 727     or `default`) for linking the C++ runtime.
 729 ### Configure Control Variables
 731 It is possible to control certain aspects of `configure` by overriding the
 732 value of `configure` variables, either on the command line or in the
 733 environment.
 735 Normally, this is **not recommended**. If used improperly, it can lead to a
 736 broken configuration. Unless you're well versed in the build system, this is
 737 hard to use properly. Therefore, `configure` will print a warning if this is
 738 detected.
 740 However, there are a few `configure` variables, known as *control variables*
 741 that are supposed to be overriden on the command line. These are variables that
 742 describe the location of tools needed by the build, like `MAKE` or `GREP`. If
 743 any such variable is specified, `configure` will use that value instead of
 744 trying to autodetect the tool. For instance, `bash configure
 745 MAKE=/opt/gnumake4.0/bin/make`.
 747 If a configure argument exists, use that instead, e.g. use `--with-jtreg`
 748 instead of setting `JTREGEXE`.
 750 Also note that, despite what autoconf claims, setting `CFLAGS` will not
 751 accomplish anything. Instead use `--with-extra-cflags` (and similar for
 752 `cxxflags` and `ldflags`).
 754 ## Running Make
 756 When you have a proper configuration, all you need to do to build OpenJDK is to
 757 run `make`. (But see the warning at [GNU Make](#gnu-make) about running the
 758 correct version of make.)
 760 When running `make` without any arguments, the default target is used, which is
 761 the same as running `make default` or `make jdk`. This will build a minimal (or
 762 roughly minimal) set of compiled output (known as an "exploded image") needed
 763 for a developer to actually execute the newly built JDK. The idea is that in an
 764 incremental development fashion, when doing a normal make, you should only
 765 spend time recompiling what's changed (making it purely incremental) and only
 766 do the work that's needed to actually run and test your code.
 768 The output of the exploded image resides in `$BUILD/jdk`. You can test the
 769 newly built JDK like this: `$BUILD/jdk/bin/java -version`.
 771 ### Common Make Targets
 773 Apart from the default target, here are some common make targets:
 775   * `hotspot` - Build all of hotspot (but only hotspot)
 776   * `hotspot-<variant>` - Build just the specified jvm variant
 777   * `images` or `product-images` - Build the JRE and JDK images
 778   * `docs` or `docs-image` - Build the documentation image
 779   * `test-image` - Build the test image
 780   * `all` or `all-images` - Build all images (product, docs and test)
 781   * `bootcycle-images` - Build images twice, second time with newly built JDK
 782     (good for testing)
 783   * `clean` - Remove all files generated by make, but not those generated by
 784     configure
 785   * `dist-clean` - Remove all files, including configuration
 787 Run `make help` to get an up-to-date list of important make targets and make
 788 control variables.
 790 It is possible to build just a single module, a single phase, or a single phase
 791 of a single module, by creating make targets according to these followin
 792 patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`,
 793 `launchers`, `libs` or `rmic`. See [Using Fine-Grained Make Targets](
 794 #using-fine-grained-make-targets) for more details about this functionality.
 796   * `<phase>` - Build the specified phase and everything it depends on
 797   * `<module>` - Build the specified module and everything it depends on
 798   * `<module>-<phase>` - Compile the specified phase for the specified module
 799     and everything it depends on
 801 Similarly, it is possible to clean just a part of the build by creating make
 802 targets according to these patterns:
 804   * `clean-<outputdir>` - Remove the subdir in the output dir with the name
 805   * `clean-<phase>` - Remove all build results related to a certain build
 806     phase
 807   * `clean-<module>` - Remove all build results related to a certain module
 808   * `clean-<module>-<phase>` - Remove all build results related to a certain
 809     module and phase
 811 ### Make Control Variables
 813 It is possible to control `make` behavior by overriding the value of `make`
 814 variables, either on the command line or in the environment.
 816 Normally, this is **not recommended**. If used improperly, it can lead to a
 817 broken build. Unless you're well versed in the build system, this is hard to
 818 use properly. Therefore, `make` will print a warning if this is detected.
 820 However, there are a few `make` variables, known as *control variables* that
 821 are supposed to be overriden on the command line. These make up the "make time"
 822 configuration, as opposed to the "configure time" configuration.
 824 #### General Make Control Variables
 826   * `JOBS` - Specify the number of jobs to build with. See [Build
 827     Performance](#build-performance).
 828   * `LOG` - Specify the logging level and functionality. See [Checking the
 829     Build Log File](#checking-the-build-log-file)
 830   * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using
 831     Multiple Configurations](#using-multiple-configurations)
 833 #### Test Make Control Variables
 835 These make control variables only make sense when running tests. Please see
 836 [Testing OpenJDK](testing.html) for details.
 838   * `TEST`
 839   * `TEST_JOBS`
 840   * `JTREG`
 841   * `GTEST`
 843 #### Advanced Make Control Variables
 845 These advanced make control variables can be potentially unsafe. See [Hints and
 846 Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and
 847 [Understanding the Build System](#understanding-the-build-system) for details.
 849   * `SPEC`
 850   * `CONF_CHECK`
 851   * `COMPARE_BUILD`
 852   * `JDK_FILTER`
 854 ## Running Tests
 856 Most of the OpenJDK tests are using the [JTReg](http://openjdk.java.net/jtreg)
 857 test framework. Make sure that your configuration knows where to find your
 858 installation of JTReg. If this is not picked up automatically, use the
 859 `--with-jtreg=<path to jtreg home>` option to point to the JTReg framework.
 860 Note that this option should point to the JTReg home, i.e. the top directory,
 861 containing `lib/jtreg.jar` etc.
 863 To execute the most basic tests (tier 1), use:
 864 ```
 865 make run-test-tier1
 866 ```
 868 For more details on how to run tests, please see the [Testing
 869 OpenJDK](testing.html) document.
 871 ## Cross-compiling
 873 Cross-compiling means using one platform (the *build* platform) to generate
 874 output that can ran on another platform (the *target* platform).
 876 The typical reason for cross-compiling is that the build is performed on a more
 877 powerful desktop computer, but the resulting binaries will be able to run on a
 878 different, typically low-performing system. Most of the complications that
 879 arise when building for embedded is due to this separation of *build* and
 880 *target* systems.
 882 This requires a more complex setup and build procedure. This section assumes
 883 you are familiar with cross-compiling in general, and will only deal with the
 884 particularities of cross-compiling OpenJDK. If you are new to cross-compiling,
 885 please see the [external links at Wikipedia](
 886 https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start
 887 on reading materials.
 889 Cross-compiling OpenJDK requires you to be able to build both for the build
 890 platform and for the target platform. The reason for the former is that we need
 891 to build and execute tools during the build process, both native tools and Java
 892 tools.
 894 If all you want to do is to compile a 32-bit version, for the same OS, on a
 895 64-bit machine, consider using `--with-target-bits=32` instead of doing a
 896 full-blown cross-compilation. (While this surely is possible, it's a lot more
 897 work and will take much longer to build.)
 899 ### Boot JDK and Build JDK
 901 When cross-compiling, make sure you use a boot JDK that runs on the *build*
 902 system, and not on the *target* system.
 904 To be able to build, we need a "Build JDK", which is a JDK built from the
 905 current sources (that is, the same as the end result of the entire build
 906 process), but able to run on the *build* system, and not the *target* system.
 907 (In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when
 908 building JDK 9.)
 910 The build process will create a minimal Build JDK for you, as part of building.
 911 To speed up the build, you can use `--with-build-jdk` to `configure` to point
 912 to a pre-built Build JDK. Please note that the build result is unpredictable,
 913 and can possibly break in subtle ways, if the Build JDK does not **exactly**
 914 match the current sources.
 916 ### Specifying the Target Platform
 918 You *must* specify the target platform when cross-compiling. Doing so will also
 919 automatically turn the build into a cross-compiling mode. The simplest way to
 920 do this is to use the `--openjdk-target` argument, e.g.
 921 `--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`.
 922 This will automatically set the `--build`, `--host` and `--target` options for
 923 autoconf, which can otherwise be confusing. (In autoconf terminology, the
 924 "target" is known as "host", and "target" is used for building a Canadian
 925 cross-compiler.)
 927 ### Toolchain Considerations
 929 You will need two copies of your toolchain, one which generates output that can
 930 run on the target system (the normal, or *target*, toolchain), and one that
 931 generates output that can run on the build system (the *build* toolchain). Note
 932 that cross-compiling is only supported for gcc at the time being. The gcc
 933 standard is to prefix cross-compiling toolchains with the target denominator.
 934 If you follow this standard, `configure` is likely to pick up the toolchain
 935 correctly.
 937 The *build* toolchain will be autodetected just the same way the normal
 938 *build*/*target* toolchain will be autodetected when not cross-compiling. If
 939 this is not what you want, or if the autodetection fails, you can specify a
 940 devkit containing the *build* toolchain using `--with-build-devkit` to
 941 `configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments.
 943 It is often helpful to locate the cross-compilation tools, headers and
 944 libraries in a separate directory, outside the normal path, and point out that
 945 directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and
 946 appending the directory when searching for cross-compilations tools
 947 (`--with-toolchain-path`). As a compact form, you can also use `--with-devkit`
 948 to point to a single directory, if it is correctly setup. (See `basics.m4` for
 949 details.)
 951 If you are unsure what toolchain and versions to use, these have been proved
 952 working at the time of writing:
 954   * [aarch64](
 955 https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-linux-gnu-4.8-2013.11_linux.tar.xz)
 956   * [arm 32-bit hardware floating  point](
 957 https://launchpad.net/linaro-toolchain-unsupported/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux.tar.bz2)
 959 ### Native Libraries
 961 You will need copies of external native libraries for the *target* system,
 962 present on the *build* machine while building.
 964 Take care not to replace the *build* system's version of these libraries by
 965 mistake, since that can render the *build* machine unusable.
 967 Make sure that the libraries you point to (ALSA, X11, etc) are for the
 968 *target*, not the *build*, platform.
 970 #### ALSA
 972 You will need alsa libraries suitable for your *target* system. For most cases,
 973 using Debian's pre-built libraries work fine.
 975 Note that alsa is needed even if you only want to build a headless JDK.
 977   * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and
 978     search for the `libasound2` and `libasound2-dev` packages for your *target*
 979     system. Download them to /tmp.
 981   * Install the libraries into the cross-compilation toolchain. For instance:
 982 ```
 983 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc
 984 dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb .
 985 dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb .
 986 ```
 988   * If alsa is not properly detected by `configure`, you can point it out by
 989     `--with-alsa`.
 991 #### X11
 993 You will need X11 libraries suitable for your *target* system. For most cases,
 994 using Debian's pre-built libraries work fine.
 996 Note that X11 is needed even if you only want to build a headless JDK.
 998   * Go to [Debian Package Search](https://www.debian.org/distrib/packages),
 999     search for the following packages for your *target* system, and download them
1000     to /tmp/target-x11:
1001       * libxi
1002       * libxi-dev
1003       * x11proto-core-dev
1004       * x11proto-input-dev
1005       * x11proto-kb-dev
1006       * x11proto-render-dev
1007       * x11proto-xext-dev
1008       * libice-dev
1009       * libxrender
1010       * libxrender-dev
1011       * libsm-dev
1012       * libxt-dev
1013       * libx11
1014       * libx11-dev
1015       * libxtst
1016       * libxtst-dev
1017       * libxext
1018       * libxext-dev
1020   * Install the libraries into the cross-compilation toolchain. For instance:
1021     ```
1022     cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr
1023     mkdir X11R6
1024     cd X11R6
1025     for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done
1026     mv usr/* .
1027     cd lib
1028     cp arm-linux-gnueabihf/* .
1029     ```
1031     You can ignore the following messages. These libraries are not needed to
1032     successfully complete a full JDK build.
1033     ```
1034     cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory
1035     cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory
1036     cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory
1037     ```
1039   * If the X11 libraries are not properly detected by `configure`, you can
1040     point them out by `--with-x`.
1042 ### Building for ARM/aarch64
1044 A common cross-compilation target is the ARM CPU. When building for ARM, it is
1045 useful to set the ABI profile. A number of pre-defined ABI profiles are
1046 available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt,
1047 armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer
1048 properly supported on OpenJDK.
1050 OpenJDK contains two different ports for the aarch64 platform, one is the
1051 original aarch64 port from the [AArch64 Port Project](
1052 http://openjdk.java.net/projects/aarch64-port) and one is a 64-bit version of
1053 the Oracle contributed ARM port. When targeting aarch64, by the default the
1054 original aarch64 port is used. To select the Oracle ARM 64 port, use
1055 `--with-cpu-port=arm64`. Also set the corresponding value (`aarch64` or
1056 `arm64`) to --with-abi-profile, to ensure a consistent build.
1058 ### Verifying the Build
1060 The build will end up in a directory named like
1061 `build/linux-arm-normal-server-release`.
1063 Inside this build output directory, the `images/jdk` and `images/jre` will
1064 contain the newly built JDK and JRE, respectively, for your *target* system.
1066 Copy these folders to your *target* system. Then you can run e.g.
1067 `images/jdk/bin/java -version`.
1069 ## Build Performance
1071 Building OpenJDK requires a lot of horsepower. Some of the build tools can be
1072 adjusted to utilize more or less of resources such as parallel threads and
1073 memory. The `configure` script analyzes your system and selects reasonable
1074 values for such options based on your hardware. If you encounter resource
1075 problems, such as out of memory conditions, you can modify the detected values
1076 with:
1078   * `--with-num-cores` -- number of cores in the build system, e.g.
1079     `--with-num-cores=8`.
1081   * `--with-memory-size` -- memory (in MB) available in the build system, e.g.
1082     `--with-memory-size=1024`
1084 You can also specify directly the number of build jobs to use with
1085 `--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag
1086 to `make`. In most cases it will be ignored by the makefiles, but it can cause
1087 problems for some make targets.
1089 It might also be necessary to specify the JVM arguments passed to the Boot JDK,
1090 using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the
1091 default JVM arguments passed to the Boot JDK.
1093 At the end of a successful execution of `configure`, you will get a performance
1094 summary, indicating how well the build will perform. Here you will also get
1095 performance hints. If you want to build fast, pay attention to those!
1097 If you want to tweak build performance, run with `make LOG=info` to get a build
1098 time summary at the end of the build process.
1100 ### Disk Speed
1102 If you are using network shares, e.g. via NFS, for your source code, make sure
1103 the build directory is situated on local disk (e.g. by `ln -s
1104 /localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely
1105 high for building on a network share; close to unusable.
1107 Also, make sure that your build tools (including Boot JDK and toolchain) is
1108 located on a local disk and not a network share.
1110 As has been stressed elsewhere, do use SSD for source code and build directory,
1111 as well as (if possible) the build tools.
1113 ### Virus Checking
1115 The use of virus checking software, especially on Windows, can *significantly*
1116 slow down building of OpenJDK. If possible, turn off such software, or exclude
1117 the directory containing the OpenJDK source code from on-the-fly checking.
1119 ### Ccache
1121 The OpenJDK build supports building with ccache when using gcc or clang. Using
1122 ccache can radically speed up compilation of native code if you often rebuild
1123 the same sources. Your milage may vary however, so we recommend evaluating it
1124 for yourself. To enable it, make sure it's on the path and configure with
1125 `--enable-ccache`.
1127 ### Precompiled Headers
1129 By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains
1130 were it is properly supported (clang, gcc, and Visual Studio). Normally, this
1131 speeds up the build process, but in some circumstances, it can actually slow
1132 things down.
1134 You can experiment by disabling precompiled headers using
1135 `--disable-precompiled-headers`.
1137 ### Icecc / icecream
1139 [icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a
1140 distributed compiler network. If you have multiple machines available for
1141 building OpenJDK, you can drastically cut individual build times by utilizing
1142 it.
1144 To use, setup an icecc network, and install icecc on the build machine. Then
1145 run `configure` using `--enable-icecc`.
1147 ### Using sjavac
1149 To speed up Java compilation, especially incremental compilations, you can try
1150 the experimental sjavac compiler by using `--enable-sjavac`.
1152 ### Building the Right Target
1154 Selecting the proper target to build can have dramatic impact on build time.
1155 For normal usage, `jdk` or the default target is just fine. You only need to
1156 build `images` for shipping, or if your tests require it.
1158 See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on
1159 how to build an even smaller subset of the product.
1161 ## Troubleshooting
1163 If your build fails, it can sometimes be difficult to pinpoint the problem or
1164 find a proper solution.
1166 ### Locating the Source of the Error
1168 When a build fails, it can be hard to pinpoint the actual cause of the error.
1169 In a typical build process, different parts of the product build in parallel,
1170 with the output interlaced.
1172 #### Build Failure Summary
1174 To help you, the build system will print a failure summary at the end. It looks
1175 like this:
1177 ```
1178 ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2)
1180 === Output from failing command(s) repeated here ===
1181 * For target hotspot_variant-server_libjvm_objs_psMemoryPool.o:
1182 /localhome/hg/jdk9-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type
1183    ... (rest of output omitted)
1185 * All command lines available in /localhome/hg/jdk9-sandbox/build/linux-x64/make-support/failure-logs.
1186 === End of repeated output ===
1188 === Make failed targets repeated here ===
1189 lib/CompileJvm.gmk:207: recipe for target '/localhome/hg/jdk9-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed
1190 make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed
1191 === End of repeated output ===
1193 Hint: Try searching the build log for the name of the first failed target.
1194 Hint: If caused by a warning, try configure --disable-warnings-as-errors.
1195 ```
1197 Let's break it down! First, the selected configuration, and the top-level
1198 target you entered on the command line that caused the failure is printed.
1200 Then, between the `Output from failing command(s) repeated here` and `End of
1201 repeated output` the first lines of output (stdout and stderr) from the actual
1202 failing command is repeated. In most cases, this is the error message that
1203 caused the build to fail. If multiple commands were failing (this can happen in
1204 a parallel build), output from all failed commands will be printed here.
1206 The path to the `failure-logs` directory is printed. In this file you will find
1207 a `<target>.log` file that contains the output from this command in its
1208 entirety, and also a `<target>.cmd`, which contain the complete command line
1209 used for running this command. You can re-run the failing command by executing
1210 `. <path to failure-logs>/<target>.cmd` in your shell.
1212 Another way to trace the failure is to follow the chain of make targets, from
1213 top-level targets to individual file targets. Between `Make failed targets
1214 repeated here` and `End of repeated output` the output from make showing this
1215 chain is repeated. The first failed recipe will typically contain the full path
1216 to the file in question that failed to compile. Following lines will show a
1217 trace of make targets why we ended up trying to compile that file.
1219 Finally, some hints are given on how to locate the error in the complete log.
1220 In this example, we would try searching the log file for "`psMemoryPool.o`".
1221 Another way to quickly locate make errors in the log is to search for "`]
1222 Error`" or "`***`".
1224 Note that the build failure summary will only help you if the issue was a
1225 compilation failure or similar. If the problem is more esoteric, or is due to
1226 errors in the build machinery, you will likely get empty output logs, and `No
1227 indication of failed target found` instead of the make target chain.
1229 #### Checking the Build Log File
1231 The output (stdout and stderr) from the latest build is always stored in
1232 `$BUILD/build.log`. The previous build log is stored as `build.log.old`. This
1233 means that it is not necessary to redirect the build output yourself if you
1234 want to process it.
1236 You can increase the verbosity of the log file, by the `LOG` control variable
1237 to `make`. If you want to see the command lines used in compilations, use
1238 `LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug`
1239 or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g.
1240 `LOG=info,cmdlines`. The `debug` log level will show most shell commands
1241 executed by make, and `trace` will show all. Beware that both these log levels
1242 will produce a massive build log!
1244 ### Fixing Unexpected Build Failures
1246 Most of the time, the build will fail due to incorrect changes in the source
1247 code.
1249 Sometimes the build can fail with no apparent changes that have caused the
1250 failure. If this is the first time you are building OpenJDK on this particular
1251 computer, and the build fails, the problem is likely with your build
1252 environment. But even if you have previously built OpenJDK with success, and it
1253 now fails, your build environment might have changed (perhaps due to OS
1254 upgrades or similar). But most likely, such failures are due to problems with
1255 the incremental rebuild.
1257 #### Problems with the Build Environment
1259 Make sure your configuration is correct. Re-run `configure`, and look for any
1260 warnings. Warnings that appear in the middle of the `configure` output is also
1261 repeated at the end, after the summary. The entire log is stored in
1262 `$BUILD/configure.log`.
1264 Verify that the summary at the end looks correct. Are you indeed using the Boot
1265 JDK and native toolchain that you expect?
1267 By default, OpenJDK has a strict approach where warnings from the compiler is
1268 considered errors which fail the build. For very new or very old compiler
1269 versions, this can trigger new classes of warnings, which thus fails the build.
1270 Run `configure` with `--disable-warnings-as-errors` to turn of this behavior.
1271 (The warnings will still show, but not make the build fail.)
1273 #### Problems with Incremental Rebuilds
1275 Incremental rebuilds mean that when you modify part of the product, only the
1276 affected parts get rebuilt. While this works great in most cases, and
1277 significantly speed up the development process, from time to time complex
1278 interdependencies will result in an incorrect build result. This is the most
1279 common cause for unexpected build problems, together with inconsistencies
1280 between the different Mercurial repositories in the forest.
1282 Here are a suggested list of things to try if you are having unexpected build
1283 problems. Each step requires more time than the one before, so try them in
1284 order. Most issues will be solved at step 1 or 2.
1286  1. Make sure your forest is up-to-date
1288     Run `bash get_source.sh` to make sure you have the latest version of all
1289     repositories.
1291  2. Clean build results
1293     The simplest way to fix incremental rebuild issues is to run `make clean`.
1294     This will remove all build results, but not the configuration or any build
1295     system support artifacts. In most cases, this will solve build errors
1296     resulting from incremental build mismatches.
1298  3. Completely clean the build directory.
1300     If this does not work, the next step is to run `make dist-clean`, or
1301     removing the build output directory (`$BUILD`). This will clean all
1302     generated output, including your configuration. You will need to re-run
1303     `configure` after this step. A good idea is to run `make
1304     print-configuration` before running `make dist-clean`, as this will print
1305     your current `configure` command line. Here's a way to do this:
1307     ```
1308     make print-configuration > current-configuration
1309     make dist-clean
1310     bash configure $(cat current-configuration)
1311     make
1312     ```
1314  4. Re-clone the Mercurial forest
1316     Sometimes the Mercurial repositories themselves gets in a state that causes
1317     the product to be un-buildable. In such a case, the simplest solution is
1318     often the "sledgehammer approach": delete the entire forest, and re-clone
1319     it. If you have local changes, save them first to a different location
1320     using `hg export`.
1322 ### Specific Build Issues
1324 #### Clock Skew
1326 If you get an error message like this:
1327 ```
1328 File 'xxx' has modification time in the future.
1329 Clock skew detected. Your build may be incomplete.
1330 ```
1331 then the clock on your build machine is out of sync with the timestamps on the
1332 source files. Other errors, apparently unrelated but in fact caused by the
1333 clock skew, can occur along with the clock skew warnings. These secondary
1334 errors may tend to obscure the fact that the true root cause of the problem is
1335 an out-of-sync clock.
1337 If you see these warnings, reset the clock on the build machine, run `make
1338 clean` and restart the build.
1340 #### Out of Memory Errors
1342 On Solaris, you might get an error message like this:
1343 ```
1344 Trouble writing out table to disk
1345 ```
1346 To solve this, increase the amount of swap space on your build machine.
1348 On Windows, you might get error messages like this:
1349 ```
1350 fatal error - couldn't allocate heap
1351 cannot create ... Permission denied
1352 spawn failed
1353 ```
1354 This can be a sign of a Cygwin problem. See the information about solving
1355 problems in the [Cygwin](#cygwin) section. Rebooting the computer might help
1356 temporarily.
1358 ### Getting Help
1360 If none of the suggestions in this document helps you, or if you find what you
1361 believe is a bug in the build system, please contact the Build Group by sending
1362 a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net).
1363 Please include the relevant parts of the configure and/or build log.
1365 If you need general help or advice about developing for OpenJDK, you can also
1366 contact the Adoption Group. See the section on [Contributing to OpenJDK](
1367 #contributing-to-openjdk) for more information.
1369 ## Hints and Suggestions for Advanced Users
1371 ### Setting Up a Forest for Pushing Changes (defpath)
1373 To help you prepare a proper push path for a Mercurial repository, there exists
1374 a useful tool known as [defpath](
1375 http://openjdk.java.net/projects/code-tools/defpath). It will help you setup a
1376 proper push path for pushing changes to OpenJDK.
1378 Install the extension by cloning
1379 `http://hg.openjdk.java.net/code-tools/defpath` and updating your `.hgrc` file.
1380 Here's one way to do this:
1382 ```
1383 cd ~
1384 mkdir hg-ext
1385 cd hg-ext
1386 hg clone http://hg.openjdk.java.net/code-tools/defpath
1387 cat << EOT >> ~/.hgrc
1388 [extensions]
1389 defpath=~/hg-ext/defpath/defpath.py
1390 EOT
1391 ```
1393 You can now setup a proper push path using:
1394 ```
1395 hg defpath -d -u <your OpenJDK username>
1396 ```
1398 If you also have the `trees` extension installed in Mercurial, you will
1399 automatically get a `tdefpath` command, which is even more useful. By running
1400 `hg tdefpath -du <username>` in the top repository of your forest, all repos
1401 will get setup automatically. This is the recommended usage.
1403 ### Bash Completion
1405 The `configure` and `make` commands tries to play nice with bash command-line
1406 completion (using `<tab>` or `<tab><tab>`). To use this functionality, make
1407 sure you enable completion in your `~/.bashrc` (see instructions for bash in
1408 your operating system).
1410 Make completion will work out of the box, and will complete valid make targets.
1411 For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`.
1413 The `configure` script can get completion for options, but for this to work you
1414 need to help `bash` on the way. The standard way of running the script, `bash
1415 configure`, will not be understood by bash completion. You need `configure` to
1416 be the command to run. One way to achieve this is to add a simple helper script
1417 to your path:
1419 ```
1420 cat << EOT > /tmp/configure
1421 #!/bin/bash
1422 if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then
1423   echo >&2 "Abort: Trying to call configure helper recursively"
1424   exit 1
1425 fi
1427 bash \$PWD/configure "\$@"
1428 EOT
1429 chmod +x /tmp/configure
1430 sudo mv /tmp/configure /usr/local/bin
1431 ```
1433 Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`.
1435 ### Using Multiple Configurations
1437 You can have multiple configurations for a single source forest. When you
1438 create a new configuration, run `configure --with-conf-name=<name>` to create a
1439 configuration with the name `<name>`. Alternatively, you can create a directory
1440 under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd
1441 build/<name> && bash ../../configure`.
1443 Then you can build that configuration using `make CONF_NAME=<name>` or `make
1444 CONF=<pattern>`, where `<pattern>` is a substring matching one or several
1445 configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will
1446 match *all* available configuration, so `make CONF= hotspot` will build the
1447 `hotspot` target for all configurations. Alternatively, you can execute `make`
1448 in the configuration directory, e.g. `cd build/<name> && make`.
1450 ### Handling Reconfigurations
1452 If you update the forest and part of the configure script has changed, the
1453 build system will force you to re-run `configure`.
1455 Most of the time, you will be fine by running `configure` again with the same
1456 arguments as the last time, which can easily be performed by `make
1457 reconfigure`. To simplify this, you can use the `CONF_CHECK` make control
1458 variable, either as `make CONF_CHECK=auto`, or by setting an environment
1459 variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc`
1460 file, `make` will always run `reconfigure` automatically whenever the configure
1461 script has changed.
1463 You can also use `CONF_CHECK=ignore` to skip the check for a needed configure
1464 update. This might speed up the build, but comes at the risk of an incorrect
1465 build result. This is only recommended if you know what you're doing.
1467 From time to time, you will also need to modify the command line to `configure`
1468 due to changes. Use `make print-configure` to show the command line used for
1469 your current configuration.
1471 ### Using Fine-Grained Make Targets
1473 The default behavior for make is to create consistent and correct output, at
1474 the expense of build speed, if necessary.
1476 If you are prepared to take some risk of an incorrect build, and know enough of
1477 the system to understand how things build and interact, you can speed up the
1478 build process considerably by instructing make to only build a portion of the
1479 product.
1481 #### Building Individual Modules
1483 The safe way to use fine-grained make targets is to use the module specific
1484 make targets. All source code in JDK 9 is organized so it belongs to a module,
1485 e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific module, by
1486 giving it as make target: `make jdk.jdwp.agent`. If the specified module
1487 depends on other modules (e.g. `java.base`), those modules will be built first.
1489 You can also specify a set of modules, just as you can always specify a set of
1490 make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi
1491 jdk.crypto.ucrypto`
1493 #### Building Individual Module Phases
1495 The build process for each module is divided into separate phases. Not all
1496 modules need all phases. Which are needed depends on what kind of source code
1497 and other artifact the module consists of. The phases are:
1499   * `gensrc` (Generate source code to compile)
1500   * `gendata` (Generate non-source code artifacts)
1501   * `copy` (Copy resource artifacts)
1502   * `java` (Compile Java code)
1503   * `launchers` (Compile native executables)
1504   * `libs` (Compile native libraries)
1505   * `rmic` (Run the `rmic` tool)
1507 You can build only a single phase for a module by using the notation
1508 `$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`,
1509 use `make java.base-gensrc`.
1511 Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if
1512 present). Make will build all needed prerequisites before building the
1513 requested phase.
1515 #### Skipping the Dependency Check
1517 When using an iterative development style with frequent quick rebuilds, the
1518 dependency check made by make can take up a significant portion of the time
1519 spent on the rebuild. In such cases, it can be useful to bypass the dependency
1520 check in make.
1522 > **Note that if used incorrectly, this can lead to a broken build!**
1524 To achieve this, append `-only` to the build target. For instance, `make
1525 jdk.jdwp.agent-java-only` will *only* build the `java` phase of the
1526 `jdk.jdwp.agent` module. If the required dependencies are not present, the
1527 build can fail. On the other hand, the execution time measures in milliseconds.
1529 A useful pattern is to build the first time normally (e.g. `make
1530 jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target.
1532 #### Rebuilding Part of java.base (JDK\_FILTER)
1534 If you are modifying files in `java.base`, which is the by far largest module
1535 in OpenJDK, then you need to rebuild all those files whenever a single file has
1536 changed. (This inefficiency will hopefully be addressed in JDK 10.)
1538 As a hack, you can use the make control variable `JDK_FILTER` to specify a
1539 pattern that will be used to limit the set of files being recompiled. For
1540 instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods,
1541 `make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation
1542 to files in the `javax.crypto` package.
1544 ### Learn About Mercurial
1546 To become an efficient OpenJDK developer, it is recommended that you invest in
1547 learning Mercurial properly. Here are some links that can get you started:
1549   * [Mercurial for git users](http://www.mercurial-scm.org/wiki/GitConcepts)
1550   * [The official Mercurial tutorial](http://www.mercurial-scm.org/wiki/Tutorial)
1551   * [hg init](http://hginit.com/)
1552   * [Mercurial: The Definitive Guide](http://hgbook.red-bean.com/read/)
1554 ## Understanding the Build System
1556 This section will give you a more technical description on the details of the
1557 build system.
1559 ### Configurations
1561 The build system expects to find one or more configuration. These are
1562 technically defined by the `spec.gmk` in a subdirectory to the `build`
1563 subdirectory. The `spec.gmk` file is generated by `configure`, and contains in
1564 principle the configuration (directly or by files included by `spec.gmk`).
1566 You can, in fact, select a configuration to build by pointing to the `spec.gmk`
1567 file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`.
1568 While this is not the recommended way to call `make` as a user, it is what is
1569 used under the hood by the build system.
1571 ### Build Output Structure
1573 The build output for a configuration will end up in `build/<configuration
1574 name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory
1575 contains the following important directories:
1577 ```
1578 buildtools/
1579 configure-support/
1580 hotspot/
1581 images/
1582 jdk/
1583 make-support/
1584 support/
1585 test-results/
1586 test-support/
1587 ```
1589 This is what they are used for:
1591   * `images`: This is the directory were the output of the `*-image` make
1592     targets end up. For instance, `make jdk-image` ends up in `images/jdk`.
1594   * `jdk`: This is the "exploded image". After `make jdk`, you will be able to
1595     launch the newly built JDK by running `$BUILD/jdk/bin/java`.
1597   * `test-results`: This directory contains the results from running tests.
1599   * `support`: This is an area for intermediate files needed during the build,
1600     e.g. generated source code, object files and class files. Some noteworthy
1601     directories in `support` is `gensrc`, which contains the generated source
1602     code, and the `modules_*` directories, which contains the files in a
1603     per-module hierarchy that will later be collapsed into the `jdk` directory
1604     of the exploded image.
1606   * `buildtools`: This is an area for tools compiled for the build platform
1607     that are used during the rest of the build.
1609   * `hotspot`: This is an area for intermediate files needed when building
1610     hotspot.
1612   * `configure-support`, `make-support` and `test-support`: These directories
1613     contain files that are needed by the build system for `configure`, `make`
1614     and for running tests.
1616 ### Fixpath
1618 Windows path typically look like `C:\User\foo`, while Unix paths look like
1619 `/home/foo`. Tools with roots from Unix often experience issues related to this
1620 mismatch when running on Windows.
1622 In the OpenJDK build, we always use Unix paths internally, and only just before
1623 calling a tool that does not understand Unix paths do we convert them to
1624 Windows paths.
1626 This conversion is done by the `fixpath` tool, which is a small wrapper that
1627 modifies unix-style paths to Windows-style paths in command lines. Fixpath is
1628 compiled automatically by `configure`.
1630 ### Native Debug Symbols
1632 Native libraries and executables can have debug symbol (and other debug
1633 information) associated with them. How this works is very much platform
1634 dependent, but a common problem is that debug symbol information takes a lot of
1635 disk space, but is rarely needed by the end user.
1637 The OpenJDK supports different methods on how to handle debug symbols. The
1638 method used is selected by `--with-native-debug-symbols`, and available methods
1639 are `none`, `internal`, `external`, `zipped`.
1641   * `none` means that no debug symbols will be generated during the build.
1643   * `internal` means that debug symbols will be generated during the build, and
1644     they will be stored in the generated binary.
1646   * `external` means that debug symbols will be generated during the build, and
1647     after the compilation, they will be moved into a separate `.debuginfo` file.
1648     (This was previously known as FDS, Full Debug Symbols).
1650   * `zipped` is like `external`, but the .debuginfo file will also be zipped
1651     into a `.diz` file.
1653 When building for distribution, `zipped` is a good solution. Binaries built
1654 with `internal` is suitable for use by developers, since they facilitate
1655 debugging, but should be stripped before distributed to end users.
1657 ### Autoconf Details
1659 The `configure` script is based on the autoconf framework, but in some details
1660 deviate from a normal autoconf `configure` script.
1662 The `configure` script in the top level directory of OpenJDK is just a thin
1663 wrapper that calls `make/autoconf/configure`. This in turn provides
1664 functionality that is not easily expressed in the normal Autoconf framework,
1665 and then calls into the core of the `configure` script, which is the
1666 `make/autoconf/generated-configure.sh` file.
1668 As the name implies, this file is generated by Autoconf. It is checked in after
1669 regeneration, to alleviate the common user to have to install Autoconf.
1671 The build system will detect if the Autoconf source files have changed, and
1672 will trigger a regeneration of `make/autoconf/generated-configure.sh` if
1673 needed. You can also manually request such an update by `bash
1674 make/autoconf/autogen.sh`.
1676 If you make changes to the build system that requires a re-generation, note the
1677 following:
1679   * You must use *exactly* version 2.69 of autoconf for your patch to be
1680     accepted. This is to avoid spurious changes in the generated file. Note
1681     that Ubuntu 16.04 ships a patched version of autoconf which claims to be
1682     2.69, but is not.
1684   * You do not need to include the generated file in reviews.
1686   * If the generated file needs updating, the Oracle JDK closed counter-part
1687     will also need to be updated. It is very much appreciated if you ask for an
1688     Oracle engineer to sponsor your push so this can be made in tandem.
1690 ### Developing the Build System Itself
1692 This section contains a few remarks about how to develop for the build system
1693 itself. It is not relevant if you are only making changes in the product source
1694 code.
1696 While technically using `make`, the make source files of the OpenJDK does not
1697 resemble most other Makefiles. Instead of listing specific targets and actions
1698 (perhaps using patterns), the basic modus operandi is to call a high-level
1699 function (or properly, macro) from the API in `make/common`. For instance, to
1700 compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module,
1701 a call like this would be made:
1703 ```
1704 $(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \
1706     SRC := $(TOPDIR)/src/jkd.foo/share/classes, \
1707     INCLUDES := jdk/internal/foo, \
1708     BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \
1709 ))
1710 ```
1712 By encapsulating and expressing the high-level knowledge of *what* should be
1713 done, rather than *how* it should be done (as is normal in Makefiles), we can
1714 build a much more powerful and flexible build system.
1716 Correct dependency tracking is paramount. Sloppy dependency tracking will lead
1717 to improper parallelization, or worse, race conditions.
1719 To test for/debug race conditions, try running `make JOBS=1` and `make
1720 JOBS=100` and see if it makes any difference. (It shouldn't).
1722 To compare the output of two different builds and see if, and how, they differ,
1723 run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two
1724 builds you want to compare.
1726 To automatically build two consecutive versions and compare them, use
1727 `COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value
1728 assignments, like this:
1729 ```
1730 make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot
1731 ```
1732 See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`.
1734 To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`.
1735 Use `JOBS=1` to avoid parallelism.
1737 Please check that you adhere to the [Code Conventions for the Build System](
1738 http://openjdk.java.net/groups/build/doc/code-conventions.html) before
1739 submitting patches. Also see the section in [Autoconf Details](
1740 #autoconf-details) about the generated configure script.
1742 ## Contributing to OpenJDK
1744 So, now you've build your OpenJDK, and made your first patch, and want to
1745 contribute it back to the OpenJDK community.
1747 First of all: Thank you! We gladly welcome your contribution to the OpenJDK.
1748 However, please bear in mind that OpenJDK is a massive project, and we must ask
1749 you to follow our rules and guidelines to be able to accept your contribution.
1751 The official place to start is the ['How to contribute' page](
1752 http://openjdk.java.net/contribute/). There is also an official (but somewhat
1753 outdated and skimpy on details) [Developer's Guide](
1754 http://openjdk.java.net/guide/).
1756 If this seems overwhelming to you, the Adoption Group is there to help you! A
1757 good place to start is their ['New Contributor' page](
1758 https://wiki.openjdk.java.net/display/Adoption/New+Contributor), or start
1759 reading the comprehensive [Getting Started Kit](
1760 https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The
1761 Adoption Group will also happily answer any questions you have about
1762 contributing. Contact them by [mail](
1763 http://mail.openjdk.java.net/mailman/listinfo/adoption-discuss) or [IRC](
1764 http://openjdk.java.net/irc/).
1766 ---
1767 # Override styles from the base CSS file that are not ideal for this document.
1768 header-includes:
1769  - '<style type="text/css">pre, code, tt { color: #1d6ae5; }</style>'
1770 ---