1 % Building the JDK
   3 ## TL;DR (Instructions for the Impatient)
   5 If you are eager to try out building the JDK, 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 JDK 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 The JDK 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 the JDK 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 JDK.
  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 repositories. 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, if using [Cygwin](#cygwin), extra care must be taken to make sure
  79     the 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         JDK 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 JDK 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 JDK 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 The JDK 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 aarch64
 125 At a minimum, a machine with 8 cores is advisable, as well as 8 GB of RAM.
 126 (The more cores to use, the more memory you need.) At least 6 GB of free disk
 127 space is required.
 129 If you do not have access to sufficiently powerful hardware, it is also
 130 possible to use [cross-compiling](#cross-compiling).
 132 ### Building on 32-bit arm
 134 This is not recommended. Instead, see the section on [Cross-compiling](
 135 #cross-compiling).
 137 ## Operating System Requirements
 139 The mainline JDK project supports Linux, Solaris, macOS, AIX and Windows.
 140 Support for other operating system, e.g. BSD, exists in separate "port"
 141 projects.
 143 In general, the JDK can be built on a wide range of versions of these operating
 144 systems, but the further you deviate from what is tested on a daily basis, the
 145 more likely you are to run into problems.
 147 This table lists the OS versions used by Oracle when building the JDK. Such
 148 information is always subject to change, but this table is up to date at the
 149 time of writing.
 151  Operating system   Vendor/version used
 152  -----------------  -------------------------------------------------------
 153  Linux              Oracle Enterprise Linux 6.4 / 7.1 (using kernel 3.8.13)
 154  Solaris            Solaris 11.1 SRU 21.4.1 / 11.2 SRU 5.5
 155  macOS              Mac OS X 10.9 (Mavericks) / 10.10 (Yosemite)
 156  Windows            Windows Server 2012 R2
 158 The double version numbers for Linux, Solaris and macOS is due to the hybrid
 159 model used at Oracle, where header files and external libraries from an older
 160 version are used when building on a more modern version of the OS.
 162 The Build Group has a wiki page with [Supported Build Platforms](
 163 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms). From
 164 time to time, this is updated by contributors to list successes or failures of
 165 building on different platforms.
 167 ### Windows
 169 Windows XP is not a supported platform, but all newer Windows should be able to
 170 build the JDK.
 172 On Windows, it is important that you pay attention to the instructions in the
 173 [Special Considerations](#special-considerations).
 175 Windows is the only non-POSIX OS supported by the JDK, and as such, requires
 176 some extra care. A POSIX support layer is required to build on Windows.
 177 Currently, the only supported such layers are Cygwin and Windows Subsystem for
 178 Linux (WSL). (Msys is no longer supported due to a too old bash; msys2 would
 179 likely be possible to support in a future version but that would require effort
 180 to implement.)
 182 Internally in the build system, all paths are represented as Unix-style paths,
 183 e.g. `/cygdrive/c/hg/jdk9/Makefile` rather than `C:\hg\jdk9\Makefile`. This
 184 rule also applies to input to the build system, e.g. in arguments to
 185 `configure`. So, use `--with-msvcr-dll=/cygdrive/c/msvcr100.dll` rather than
 186 `--with-msvcr-dll=c:\msvcr100.dll`. For details on this conversion, see the section
 187 on [Fixpath](#fixpath).
 189 #### Cygwin
 191 A functioning [Cygwin](http://www.cygwin.com/) environment is required for
 192 building the JDK on Windows. If you have a 64-bit OS, we strongly recommend
 193 using the 64-bit version of Cygwin.
 195 **Note:** Cygwin has a model of continuously updating all packages without any
 196 easy way to install or revert to a specific version of a package. This means
 197 that whenever you add or update a package in Cygwin, you might (inadvertently)
 198 update tools that are used by the JDK build process, and that can cause
 199 unexpected build problems.
 201 The JDK requires GNU Make 4.0 or greater in Cygwin. This is usually not a
 202 problem, since Cygwin currently only distributes GNU Make at a version above
 203 4.0.
 205 Apart from the basic Cygwin installation, the following packages must also be
 206 installed:
 208   * `autoconf`
 209   * `make`
 210   * `zip`
 211   * `unzip`
 213 Often, you can install these packages using the following command line:
 214 ```
 215 <path to Cygwin setup>/setup-x86_64 -q -P autoconf -P make -P unzip -P zip
 216 ```
 218 Unfortunately, Cygwin can be unreliable in certain circumstances. If you
 219 experience build tool crashes or strange issues when building on Windows,
 220 please check the Cygwin FAQ on the ["BLODA" list](
 221 https://cygwin.com/faq/faq.html#faq.using.bloda) and the section on [fork()
 222 failures](https://cygwin.com/faq/faq.html#faq.using.fixing-fork-failures).
 224 #### Windows Subsystem for Linux (WSL)
 226 Windows 10 1809 or newer is supported due to a dependency on the wslpath utility
 227 and support for environment variable sharing through WSLENV. Version 1803 can
 228 work but intermittent build failures have been observed.
 230 It's possible to build both Windows and Linux binaries from WSL. To build
 231 Windows binaries, you must use a Windows boot JDK (located in a
 232 Windows-accessible directory). To build Linux binaries, you must use a Linux
 233 boot JDK. The default behavior is to build for Windows. To build for Linux, pass
 234 `--build=x86_64-unknown-linux-gnu --host=x86_64-unknown-linux-gnu` to
 235 `configure`.
 237 If building Windows binaries, the source code must be located in a Windows-
 238 accessible directory. This is because Windows executables (such as Visual Studio
 239 and the boot JDK) must be able to access the source code. Also, the drive where
 240 the source is stored must be mounted as case-insensitive by changing either
 241 /etc/fstab or /etc/wsl.conf in WSL. Individual directories may be corrected
 242 using the fsutil tool in case the source was cloned before changing the mount
 243 options.
 245 Note that while it's possible to build on WSL, testing is still not fully
 246 supported.
 248 ### Solaris
 250 See `make/devkit/solaris11.1-package-list.txt` for a list of recommended
 251 packages to install when building on Solaris. The versions specified in this
 252 list is the versions used by the daily builds at Oracle, and is likely to work
 253 properly.
 255 Older versions of Solaris shipped a broken version of `objcopy`. At least
 256 version 2.21.1 is needed, which is provided by Solaris 11 Update 1. Objcopy is
 257 needed if you want to have external debug symbols. Please make sure you are
 258 using at least version 2.21.1 of objcopy, or that you disable external debug
 259 symbols.
 261 ### macOS
 263 Apple is using a quite aggressive scheme of pushing OS updates, and coupling
 264 these updates with required updates of Xcode. Unfortunately, this makes it
 265 difficult for a project such as the JDK to keep pace with a continuously updated
 266 machine running macOS. See the section on [Apple Xcode](#apple-xcode) on some
 267 strategies to deal with this.
 269 It is recommended that you use at least Mac OS X 10.13 (High Sierra). At the time
 270 of writing, the JDK has been successfully compiled on macOS 10.12 (Sierra).
 272 The standard macOS environment contains the basic tooling needed to build, but
 273 for external libraries a package manager is recommended. The JDK uses
 274 [homebrew](https://brew.sh/) in the examples, but feel free to use whatever
 275 manager you want (or none).
 277 ### Linux
 279 It is often not much problem to build the JDK on Linux. The only general advice
 280 is to try to use the compilers, external libraries and header files as provided
 281 by your distribution.
 283 The basic tooling is provided as part of the core operating system, but you
 284 will most likely need to install developer packages.
 286 For apt-based distributions (Debian, Ubuntu, etc), try this:
 287 ```
 288 sudo apt-get install build-essential
 289 ```
 291 For rpm-based distributions (Fedora, Red Hat, etc), try this:
 292 ```
 293 sudo yum groupinstall "Development Tools"
 294 ```
 296 ### AIX
 298 Please consult the AIX section of the [Supported Build Platforms](
 299 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms) OpenJDK
 300 Build Wiki page for details about which versions of AIX are supported.
 302 ## Native Compiler (Toolchain) Requirements
 304 Large portions of the JDK consists of native code, that needs to be compiled to
 305 be able to run on the target platform. In theory, toolchain and operating
 306 system should be independent factors, but in practice there's more or less a
 307 one-to-one correlation between target operating system and toolchain.
 309  Operating system   Supported toolchain
 310  ------------------ -------------------------
 311  Linux              gcc, clang
 312  macOS              Apple Xcode (using clang)
 313  Solaris            Oracle Solaris Studio
 314  AIX                IBM XL C/C++
 315  Windows            Microsoft Visual Studio
 317 Please see the individual sections on the toolchains for version
 318 recommendations. As a reference, these versions of the toolchains are used, at
 319 the time of writing, by Oracle for the daily builds of the JDK. It should be
 320 possible to compile the JDK with both older and newer versions, but the closer
 321 you stay to this list, the more likely you are to compile successfully without
 322 issues.
 324  Operating system   Toolchain version
 325  ------------------ -------------------------------------------------------
 326  Linux              gcc 7.3.0
 327  macOS              Apple Xcode 9.4 (using clang 9.1.0)
 328  Solaris            Oracle Solaris Studio 12.4 (with compiler version 5.13)
 329  Windows            Microsoft Visual Studio 2017 update 15.5.5
 331 ### gcc
 333 The minimum accepted version of gcc is 4.8. Older versions will generate a warning
 334 by `configure` and are unlikely to work.
 336 The JDK is currently known to be able to compile with at least version 7.4 of
 337 gcc.
 339 In general, any version between these two should be usable.
 341 ### clang
 343 The minimum accepted version of clang is 3.2. Older versions will not be
 344 accepted by `configure`.
 346 To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`.
 348 ### Apple Xcode
 350 The oldest supported version of Xcode is 8.
 352 You will need the Xcode command lines developers tools to be able to build
 353 the JDK. (Actually, *only* the command lines tools are needed, not the IDE.)
 354 The simplest way to install these is to run:
 355 ```
 356 xcode-select --install
 357 ```
 359 It is advisable to keep an older version of Xcode for building the JDK when
 360 updating Xcode. This [blog page](
 361 http://iosdevelopertips.com/xcode/install-multiple-versions-of-xcode.html) has
 362 good suggestions on managing multiple Xcode versions. To use a specific version
 363 of Xcode, use `xcode-select -s` before running `configure`, or use
 364 `--with-toolchain-path` to point to the version of Xcode to use, e.g.
 365 `configure --with-toolchain-path=/Applications/Xcode8.app/Contents/Developer/usr/bin`
 367 If you have recently (inadvertently) updated your OS and/or Xcode version, and
 368 the JDK can no longer be built, please see the section on [Problems with the
 369 Build Environment](#problems-with-the-build-environment), and [Getting
 370 Help](#getting-help) to find out if there are any recent, non-merged patches
 371 available for this update.
 373 ### Oracle Solaris Studio
 375 The minimum accepted version of the Solaris Studio compilers is 5.13
 376 (corresponding to Solaris Studio 12.4). Older versions will not be accepted by
 377 configure.
 379 The Solaris Studio installation should contain at least these packages:
 381  Package                                            Version
 382  -------------------------------------------------- -------------
 383  developer/solarisstudio-124/backend                12.4-
 384  developer/solarisstudio-124/c++                    12.4-
 385  developer/solarisstudio-124/cc                     12.4-
 386  developer/solarisstudio-124/library/c++-libs       12.4-
 387  developer/solarisstudio-124/library/math-libs      12.4-
 388  developer/solarisstudio-124/library/studio-gccrt   12.4-
 389  developer/solarisstudio-124/studio-common          12.4-
 390  developer/solarisstudio-124/studio-ja              12.4-
 391  developer/solarisstudio-124/studio-legal           12.4-
 392  developer/solarisstudio-124/studio-zhCN            12.4-
 394 Compiling with Solaris Studio can sometimes be finicky. This is the exact
 395 version used by Oracle, which worked correctly at the time of writing:
 396 ```
 397 $ cc -V
 398 cc: Sun C 5.13 SunOS_i386 2014/10/20
 399 $ CC -V
 400 CC: Sun C++ 5.13 SunOS_i386 151846-10 2015/10/30
 401 ```
 403 ### Microsoft Visual Studio
 405 The minimum accepted version of Visual Studio is 2010. Older versions will not
 406 be accepted by `configure`. The maximum accepted version of Visual Studio is
 407 2017. Versions older than 2017 are unlikely to continue working for long.
 409 If you have multiple versions of Visual Studio installed, `configure` will by
 410 default pick the latest. You can request a specific version to be used by
 411 setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2015`.
 413 If you get `LINK: fatal error LNK1123: failure during conversion to COFF: file
 414 invalid` when building using Visual Studio 2010, you have encountered
 415 [KB2757355](http://support.microsoft.com/kb/2757355), a bug triggered by a
 416 specific installation order. However, the solution suggested by the KB article
 417 does not always resolve the problem. See [this stackoverflow discussion](
 418 https://stackoverflow.com/questions/10888391) for other suggestions.
 420 ### IBM XL C/C++
 422 Please consult the AIX section of the [Supported Build Platforms](
 423 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms) OpenJDK
 424 Build Wiki page for details about which versions of XLC are supported.
 427 ## Boot JDK Requirements
 429 Paradoxically, building the JDK requires a pre-existing JDK. This is called the
 430 "boot JDK". The boot JDK does not, however, have to be a JDK built directly from
 431 the source code available in the OpenJDK Community.  If you are porting the JDK
 432 to a new platform, chances are that there already exists another JDK for that
 433 platform that is usable as boot JDK.
 435 The rule of thumb is that the boot JDK for building JDK major version *N*
 436 should be a JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be
 437 suitable as boot JDK. However, the JDK should be able to "build itself", so an
 438 up-to-date build of the current JDK source is an acceptable alternative. If
 439 you are following the *N-1* rule, make sure you've got the latest update
 440 version, since JDK 8 GA might not be able to build JDK 9 on all platforms.
 442 Early in the release cycle, version *N-1* may not yet have been released. In
 443 that case, the preferred boot JDK will be version *N-2* until version *N-1*
 444 is available.
 446 If the boot JDK is not automatically detected, or the wrong JDK is picked, use
 447 `--with-boot-jdk` to point to the JDK to use.
 449 ### Getting JDK binaries
 451 JDK binaries for Linux, Windows and macOS can be downloaded from
 452 [jdk.java.net](http://jdk.java.net). An alternative is to download the
 453 [Oracle JDK](http://www.oracle.com/technetwork/java/javase/downloads). Another
 454 is the [Adopt OpenJDK Project](https://adoptopenjdk.net/), which publishes
 455 experimental prebuilt binaries for various platforms.
 457 On Linux you can also get a JDK from the Linux distribution. On apt-based
 458 distros (like Debian and Ubuntu), `sudo apt-get install openjdk-<VERSION>-jdk`
 459 is typically enough to install a JDK \<VERSION\>. On rpm-based distros (like
 460 Fedora and Red Hat), try `sudo yum install java-<VERSION>-openjdk-devel`.
 462 ## External Library Requirements
 464 Different platforms require different external libraries. In general, libraries
 465 are not optional - that is, they are either required or not used.
 467 If a required library is not detected by `configure`, you need to provide the
 468 path to it. There are two forms of the `configure` arguments to point to an
 469 external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to
 470 include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise,
 471 but require the include files an library files to reside in a default hierarchy
 472 under this directory. In most cases, it works fine.
 474 As a fallback, the second version allows you to point to the include directory
 475 and the lib directory separately.
 477 ### FreeType
 479 FreeType2 from [The FreeType Project](http://www.freetype.org/) is not required
 480 on any platform. The exception is on Unix-based platforms when configuring such
 481 that the build artifacts will reference a system installed library,
 482 rather than bundling the JDK’s own copy.
 484   * To install on an apt-based Linux, try running `sudo apt-get install
 485     libfreetype6-dev`.
 486   * To install on an rpm-based Linux, try running `sudo yum install
 487     freetype-devel`.
 488   * To install on Solaris, try running `pkg install system/library/freetype-2`.
 490 Use `--with-freetype-include=<path>` and `--with-freetype-lib=<path>`
 491 if `configure` does not automatically locate the platform FreeType files.
 493 ### CUPS
 495 CUPS, [Common UNIX Printing System](http://www.cups.org) header files are
 496 required on all platforms, except Windows. Often these files are provided by
 497 your operating system.
 499   * To install on an apt-based Linux, try running `sudo apt-get install
 500     libcups2-dev`.
 501   * To install on an rpm-based Linux, try running `sudo yum install
 502     cups-devel`.
 503   * To install on Solaris, try running `pkg install print/cups`.
 505 Use `--with-cups=<path>` if `configure` does not properly locate your CUPS
 506 files.
 508 ### X11
 510 Certain [X11](http://www.x.org/) libraries and include files are required on
 511 Linux and Solaris.
 513   * To install on an apt-based Linux, try running `sudo apt-get install
 514     libx11-dev libxext-dev libxrender-dev libxrandr-dev libxtst-dev libxt-dev`.
 515   * To install on an rpm-based Linux, try running `sudo yum install
 516     libXtst-devel libXt-devel libXrender-devel libXrandr-devel libXi-devel`.
 517   * To install on Solaris, try running `pkg install x11/header/x11-protocols
 518     x11/library/libice x11/library/libpthread-stubs x11/library/libsm
 519     x11/library/libx11 x11/library/libxau x11/library/libxcb
 520     x11/library/libxdmcp x11/library/libxevie x11/library/libxext
 521     x11/library/libxrender x11/library/libxrandr x11/library/libxscrnsaver
 522     x11/library/libxtst x11/library/toolkit/libxt`.
 524 Use `--with-x=<path>` if `configure` does not properly locate your X11 files.
 526 ### ALSA
 528 ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is
 529 required on Linux. At least version 0.9.1 of ALSA is required.
 531   * To install on an apt-based Linux, try running `sudo apt-get install
 532     libasound2-dev`.
 533   * To install on an rpm-based Linux, try running `sudo yum install
 534     alsa-lib-devel`.
 536 Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA
 537 files.
 539 ### libffi
 541 libffi, the [Portable Foreign Function Interface Library](
 542 http://sourceware.org/libffi) is required when building the Zero version of
 543 Hotspot.
 545   * To install on an apt-based Linux, try running `sudo apt-get install
 546     libffi-dev`.
 547   * To install on an rpm-based Linux, try running `sudo yum install
 548     libffi-devel`.
 550 Use `--with-libffi=<path>` if `configure` does not properly locate your libffi
 551 files.
 553 ## Build Tools Requirements
 555 ### Autoconf
 557 The JDK requires [Autoconf](http://www.gnu.org/software/autoconf) on all
 558 platforms. At least version 2.69 is required.
 560   * To install on an apt-based Linux, try running `sudo apt-get install
 561     autoconf`.
 562   * To install on an rpm-based Linux, try running `sudo yum install
 563     autoconf`.
 564   * To install on macOS, try running `brew install autoconf`.
 565   * To install on Windows, try running `<path to Cygwin setup>/setup-x86_64 -q
 566     -P autoconf`.
 568 If `configure` has problems locating your installation of autoconf, you can
 569 specify it using the `AUTOCONF` environment variable, like this:
 571 ```
 572 AUTOCONF=<path to autoconf> configure ...
 573 ```
 575 ### GNU Make
 577 The JDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors
 578 of make are supported.
 580 At least version 3.81 of GNU Make must be used. For distributions supporting
 581 GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful
 582 functionality to handle parallel building (supported by `--with-output-sync`)
 583 and speed and stability improvements.
 585 Note that `configure` locates and verifies a properly functioning version of
 586 `make` and stores the path to this `make` binary in the configuration. If you
 587 start a build using `make` on the command line, you will be using the version
 588 of make found first in your `PATH`, and not necessarily the one stored in the
 589 configuration. This initial make will be used as "bootstrap make", and in a
 590 second stage, the make located by `configure` will be called. Normally, this
 591 will present no issues, but if you have a very old `make`, or a non-GNU Make
 592 `make` in your path, this might cause issues.
 594 If you want to override the default make found by `configure`, use the `MAKE`
 595 configure variable, e.g. `configure MAKE=/opt/gnu/make`.
 597 On Solaris, it is common to call the GNU version of make by using `gmake`.
 599 ### GNU Bash
 601 The JDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells
 602 are supported.
 604 At least version 3.2 of GNU Bash must be used.
 606 ## Running Configure
 608 To build the JDK, you need a "configuration", which consists of a directory
 609 where to store the build output, coupled with information about the platform,
 610 the specific build machine, and choices that affect how the JDK is built.
 612 The configuration is created by the `configure` script. The basic invocation of
 613 the `configure` script looks like this:
 615 ```
 616 bash configure [options]
 617 ```
 619 This will create an output directory containing the configuration and setup an
 620 area for the build result. This directory typically looks like
 621 `build/linux-x64-normal-server-release`, but the actual name depends on your
 622 specific configuration. (It can also be set directly, see [Using Multiple
 623 Configurations](#using-multiple-configurations)). This directory is referred to
 624 as `$BUILD` in this documentation.
 626 `configure` will try to figure out what system you are running on and where all
 627 necessary build components are. If you have all prerequisites for building
 628 installed, it should find everything. If it fails to detect any component
 629 automatically, it will exit and inform you about the problem.
 631 Some command line examples:
 633   * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`:
 634     ```
 635     bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32
 636     ```
 638   * Create a debug build with the `server` JVM and DTrace enabled:
 639     ```
 640     bash configure --enable-debug --with-jvm-variants=server --enable-dtrace
 641     ```
 643 ### Common Configure Arguments
 645 Here follows some of the most common and important `configure` argument.
 647 To get up-to-date information on *all* available `configure` argument, please
 648 run:
 649 ```
 650 bash configure --help
 651 ```
 653 (Note that this help text also include general autoconf options, like
 654 `--dvidir`, that is not relevant to the JDK. To list only JDK-specific
 655 features, use `bash configure --help=short` instead.)
 657 #### Configure Arguments for Tailoring the Build
 659   * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand
 660     for `--with-debug-level=fastdebug`)
 661   * `--with-debug-level=<level>` - Set the debug level, which can be `release`,
 662     `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized`
 663     is variant of `release` with additional Hotspot debug code.
 664   * `--with-native-debug-symbols=<method>` - Specify if and how native debug
 665     symbols should be built. Available methods are `none`, `internal`,
 666     `external`, `zipped`. Default behavior depends on platform. See [Native
 667     Debug Symbols](#native-debug-symbols) for more details.
 668   * `--with-version-string=<string>` - Specify the version string this build
 669     will be identified with.
 670   * `--with-version-<part>=<value>` - A group of options, where `<part>` can be
 671     any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use
 672     these options to modify just the corresponding part of the version string
 673     from the default, or the value provided by `--with-version-string`.
 674   * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant
 675     (or variants) of Hotspot. Valid variants are: `server`, `client`,
 676     `minimal`, `core`, `zero`, `custom`. Note that not all
 677     variants are possible to combine in a single build.
 678   * `--with-jvm-features=<feature>[,<feature>...]` - Use the specified JVM
 679     features when building Hotspot. The list of features will be enabled on top
 680     of the default list. For the `custom` JVM variant, this default list is
 681     empty. A complete list of available JVM features can be found using `bash
 682     configure --help`.
 683   * `--with-target-bits=<bits>` - Create a target binary suitable for running
 684     on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build
 685     platform, instead of doing a full cross-compile. (This is known as a
 686     *reduced* build.)
 688 On Linux, BSD and AIX, it is possible to override where Java by default
 689 searches for runtime/JNI libraries. This can be useful in situations where
 690 there is a special shared directory for system JNI libraries. This setting
 691 can in turn be overriden at runtime by setting the `java.library.path` property.
 693   * `--with-jni-libpath=<path>` - Use the specified path as a default
 694   when searching for runtime libraries.
 696 #### Configure Arguments for Native Compilation
 698   * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources
 699   * `--with-sysroot=<path>` - Use this directory as sysroot
 700   * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the
 701     default path when searching for all kinds of binaries
 702   * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when
 703     searching for toolchain binaries (compilers etc)
 704   * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C
 705     files
 706   * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++
 707     files
 708   * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK
 709     libraries
 711 #### Configure Arguments for External Dependencies
 713   * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK](
 714     #boot-jdk-requirements)
 715   * `--with-freetype=<path>` - Set the path to [FreeType](#freetype)
 716   * `--with-cups=<path>` - Set the path to [CUPS](#cups)
 717   * `--with-x=<path>` - Set the path to [X11](#x11)
 718   * `--with-alsa=<path>` - Set the path to [ALSA](#alsa)
 719   * `--with-libffi=<path>` - Set the path to [libffi](#libffi)
 720   * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests](
 721     #running-tests)
 723 Certain third-party libraries used by the JDK (libjpeg, giflib, libpng, lcms
 724 and zlib) are included in the JDK repository. The default behavior of the
 725 JDK build is to use this version of these libraries, but they might be
 726 replaced by an external version. To do so, specify `system` as the `<source>`
 727 option in these arguments. (The default is `bundled`).
 729   * `--with-libjpeg=<source>` - Use the specified source for libjpeg
 730   * `--with-giflib=<source>` - Use the specified source for giflib
 731   * `--with-libpng=<source>` - Use the specified source for libpng
 732   * `--with-lcms=<source>` - Use the specified source for lcms
 733   * `--with-zlib=<source>` - Use the specified source for zlib
 735 On Linux, it is possible to select either static or dynamic linking of the C++
 736 runtime. The default is static linking, with dynamic linking as fallback if the
 737 static library is not found.
 739   * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic`
 740     or `default`) for linking the C++ runtime.
 742 ### Configure Control Variables
 744 It is possible to control certain aspects of `configure` by overriding the
 745 value of `configure` variables, either on the command line or in the
 746 environment.
 748 Normally, this is **not recommended**. If used improperly, it can lead to a
 749 broken configuration. Unless you're well versed in the build system, this is
 750 hard to use properly. Therefore, `configure` will print a warning if this is
 751 detected.
 753 However, there are a few `configure` variables, known as *control variables*
 754 that are supposed to be overriden on the command line. These are variables that
 755 describe the location of tools needed by the build, like `MAKE` or `GREP`. If
 756 any such variable is specified, `configure` will use that value instead of
 757 trying to autodetect the tool. For instance, `bash configure
 758 MAKE=/opt/gnumake4.0/bin/make`.
 760 If a configure argument exists, use that instead, e.g. use `--with-jtreg`
 761 instead of setting `JTREGEXE`.
 763 Also note that, despite what autoconf claims, setting `CFLAGS` will not
 764 accomplish anything. Instead use `--with-extra-cflags` (and similar for
 765 `cxxflags` and `ldflags`).
 767 ## Running Make
 769 When you have a proper configuration, all you need to do to build the JDK is to
 770 run `make`. (But see the warning at [GNU Make](#gnu-make) about running the
 771 correct version of make.)
 773 When running `make` without any arguments, the default target is used, which is
 774 the same as running `make default` or `make jdk`. This will build a minimal (or
 775 roughly minimal) set of compiled output (known as an "exploded image") needed
 776 for a developer to actually execute the newly built JDK. The idea is that in an
 777 incremental development fashion, when doing a normal make, you should only
 778 spend time recompiling what's changed (making it purely incremental) and only
 779 do the work that's needed to actually run and test your code.
 781 The output of the exploded image resides in `$BUILD/jdk`. You can test the
 782 newly built JDK like this: `$BUILD/jdk/bin/java -version`.
 784 ### Common Make Targets
 786 Apart from the default target, here are some common make targets:
 788   * `hotspot` - Build all of hotspot (but only hotspot)
 789   * `hotspot-<variant>` - Build just the specified jvm variant
 790   * `images` or `product-images` - Build the JDK image
 791   * `docs` or `docs-image` - Build the documentation image
 792   * `test-image` - Build the test image
 793   * `all` or `all-images` - Build all images (product, docs and test)
 794   * `bootcycle-images` - Build images twice, second time with newly built JDK
 795     (good for testing)
 796   * `clean` - Remove all files generated by make, but not those generated by
 797     configure
 798   * `dist-clean` - Remove all files, including configuration
 800 Run `make help` to get an up-to-date list of important make targets and make
 801 control variables.
 803 It is possible to build just a single module, a single phase, or a single phase
 804 of a single module, by creating make targets according to these followin
 805 patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`,
 806 `launchers`, `libs` or `rmic`. See [Using Fine-Grained Make Targets](
 807 #using-fine-grained-make-targets) for more details about this functionality.
 809   * `<phase>` - Build the specified phase and everything it depends on
 810   * `<module>` - Build the specified module and everything it depends on
 811   * `<module>-<phase>` - Compile the specified phase for the specified module
 812     and everything it depends on
 814 Similarly, it is possible to clean just a part of the build by creating make
 815 targets according to these patterns:
 817   * `clean-<outputdir>` - Remove the subdir in the output dir with the name
 818   * `clean-<phase>` - Remove all build results related to a certain build
 819     phase
 820   * `clean-<module>` - Remove all build results related to a certain module
 821   * `clean-<module>-<phase>` - Remove all build results related to a certain
 822     module and phase
 824 ### Make Control Variables
 826 It is possible to control `make` behavior by overriding the value of `make`
 827 variables, either on the command line or in the environment.
 829 Normally, this is **not recommended**. If used improperly, it can lead to a
 830 broken build. Unless you're well versed in the build system, this is hard to
 831 use properly. Therefore, `make` will print a warning if this is detected.
 833 However, there are a few `make` variables, known as *control variables* that
 834 are supposed to be overriden on the command line. These make up the "make time"
 835 configuration, as opposed to the "configure time" configuration.
 837 #### General Make Control Variables
 839   * `JOBS` - Specify the number of jobs to build with. See [Build
 840     Performance](#build-performance).
 841   * `LOG` - Specify the logging level and functionality. See [Checking the
 842     Build Log File](#checking-the-build-log-file)
 843   * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using
 844     Multiple Configurations](#using-multiple-configurations)
 846 #### Test Make Control Variables
 848 These make control variables only make sense when running tests. Please see
 849 [Testing the JDK](testing.html) for details.
 851   * `TEST`
 852   * `TEST_JOBS`
 853   * `JTREG`
 854   * `GTEST`
 856 #### Advanced Make Control Variables
 858 These advanced make control variables can be potentially unsafe. See [Hints and
 859 Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and
 860 [Understanding the Build System](#understanding-the-build-system) for details.
 862   * `SPEC`
 863   * `CONF_CHECK`
 864   * `COMPARE_BUILD`
 865   * `JDK_FILTER`
 867 ## Running Tests
 869 Most of the JDK tests are using the [JTReg](http://openjdk.java.net/jtreg)
 870 test framework. Make sure that your configuration knows where to find your
 871 installation of JTReg. If this is not picked up automatically, use the
 872 `--with-jtreg=<path to jtreg home>` option to point to the JTReg framework.
 873 Note that this option should point to the JTReg home, i.e. the top directory,
 874 containing `lib/jtreg.jar` etc.
 876 The [Adoption Group](https://wiki.openjdk.java.net/display/Adoption) provides
 877 recent builds of jtreg [here](
 878 https://adopt-openjdk.ci.cloudbees.com/job/jtreg/lastSuccessfulBuild/artifact).
 879 Download the latest `.tar.gz` file, unpack it, and point `--with-jtreg` to the
 880 `jtreg` directory that you just unpacked.
 882 To execute the most basic tests (tier 1), use:
 883 ```
 884 make run-test-tier1
 885 ```
 887 For more details on how to run tests, please see the [Testing
 888 the JDK](testing.html) document.
 890 ## Cross-compiling
 892 Cross-compiling means using one platform (the *build* platform) to generate
 893 output that can ran on another platform (the *target* platform).
 895 The typical reason for cross-compiling is that the build is performed on a more
 896 powerful desktop computer, but the resulting binaries will be able to run on a
 897 different, typically low-performing system. Most of the complications that
 898 arise when building for embedded is due to this separation of *build* and
 899 *target* systems.
 901 This requires a more complex setup and build procedure. This section assumes
 902 you are familiar with cross-compiling in general, and will only deal with the
 903 particularities of cross-compiling the JDK. If you are new to cross-compiling,
 904 please see the [external links at Wikipedia](
 905 https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start
 906 on reading materials.
 908 Cross-compiling the JDK requires you to be able to build both for the build
 909 platform and for the target platform. The reason for the former is that we need
 910 to build and execute tools during the build process, both native tools and Java
 911 tools.
 913 If all you want to do is to compile a 32-bit version, for the same OS, on a
 914 64-bit machine, consider using `--with-target-bits=32` instead of doing a
 915 full-blown cross-compilation. (While this surely is possible, it's a lot more
 916 work and will take much longer to build.)
 918 ### Cross compiling the easy way with OpenJDK devkits
 920 The OpenJDK build system provides out-of-the box support for creating and using
 921 so called devkits. A `devkit` is basically a collection of a cross-compiling
 922 toolchain and a sysroot environment which can easily be used together with the
 923 `--with-devkit` configure option to cross compile the OpenJDK. On Linux/x86_64,
 924 the following command:
 925 ```
 926 bash configure --with-devkit=<devkit-path> --openjdk-target=ppc64-linux-gnu && make
 927 ```
 929 will configure and build OpenJDK for Linux/ppc64 assuming that `<devkit-path>`
 930 points to a Linux/x86_64 to Linux/ppc64 devkit.
 932 Devkits can be created from the `make/devkit` directory by executing:
 933 ```
 935 ```
 937 where `TARGETS` contains one or more `TARGET_TRIPLET`s of the form
 938 described in [section 3.4 of the GNU Autobook](
 939 https://sourceware.org/autobook/autobook/autobook_17.html). If no
 940 targets are given, a native toolchain for the current platform will be
 941 created. Currently, at least the following targets are known to work:
 943  Supported devkit targets
 944  -------------------------
 945  x86_64-linux-gnu
 946  aarch64-linux-gnu
 947  arm-linux-gnueabihf
 948  ppc64-linux-gnu
 949  ppc64le-linux-gnu
 950  s390x-linux-gnu
 952 `BASE_OS` must be one of "OEL6" for Oracle Enterprise Linux 6 or
 953 "Fedora" (if not specified "OEL6" will be the default). If the base OS
 954 is "Fedora" the corresponding Fedora release can be specified with the
 955 help of the `BASE_OS_VERSION` option (with "27" as default version).
 956 If the build is successful, the new devkits can be found in the
 957 `build/devkit/result` subdirectory:
 958 ```
 959 cd make/devkit
 960 make TARGETS="ppc64le-linux-gnu aarch64-linux-gnu" BASE_OS=Fedora BASE_OS_VERSION=21
 961 ls -1 ../../build/devkit/result/
 962 x86_64-linux-gnu-to-aarch64-linux-gnu
 963 x86_64-linux-gnu-to-ppc64le-linux-gnu
 964 ```
 966 Notice that devkits are not only useful for targeting different build
 967 platforms. Because they contain the full build dependencies for a
 968 system (i.e. compiler and root file system), they can easily be used
 969 to build well-known, reliable and reproducible build environments. You
 970 can for example create and use a devkit with GCC 7.3 and a Fedora 12
 971 sysroot environment (with glibc 2.11) on Ubuntu 14.04 (which doesn't
 972 have GCC 7.3 by default) to produce OpenJDK binaries which will run on
 973 all Linux systems with runtime libraries newer than the ones from
 974 Fedora 12 (e.g. Ubuntu 16.04, SLES 11 or RHEL 6).
 976 ### Boot JDK and Build JDK
 978 When cross-compiling, make sure you use a boot JDK that runs on the *build*
 979 system, and not on the *target* system.
 981 To be able to build, we need a "Build JDK", which is a JDK built from the
 982 current sources (that is, the same as the end result of the entire build
 983 process), but able to run on the *build* system, and not the *target* system.
 984 (In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when
 985 building JDK 9.)
 987 The build process will create a minimal Build JDK for you, as part of building.
 988 To speed up the build, you can use `--with-build-jdk` to `configure` to point
 989 to a pre-built Build JDK. Please note that the build result is unpredictable,
 990 and can possibly break in subtle ways, if the Build JDK does not **exactly**
 991 match the current sources.
 993 ### Specifying the Target Platform
 995 You *must* specify the target platform when cross-compiling. Doing so will also
 996 automatically turn the build into a cross-compiling mode. The simplest way to
 997 do this is to use the `--openjdk-target` argument, e.g.
 998 `--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`.
 999 This will automatically set the `--build`, `--host` and `--target` options for
1000 autoconf, which can otherwise be confusing. (In autoconf terminology, the
1001 "target" is known as "host", and "target" is used for building a Canadian
1002 cross-compiler.)
1004 ### Toolchain Considerations
1006 You will need two copies of your toolchain, one which generates output that can
1007 run on the target system (the normal, or *target*, toolchain), and one that
1008 generates output that can run on the build system (the *build* toolchain). Note
1009 that cross-compiling is only supported for gcc at the time being. The gcc
1010 standard is to prefix cross-compiling toolchains with the target denominator.
1011 If you follow this standard, `configure` is likely to pick up the toolchain
1012 correctly.
1014 The *build* toolchain will be autodetected just the same way the normal
1015 *build*/*target* toolchain will be autodetected when not cross-compiling. If
1016 this is not what you want, or if the autodetection fails, you can specify a
1017 devkit containing the *build* toolchain using `--with-build-devkit` to
1018 `configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments.
1020 It is often helpful to locate the cross-compilation tools, headers and
1021 libraries in a separate directory, outside the normal path, and point out that
1022 directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and
1023 appending the directory when searching for cross-compilations tools
1024 (`--with-toolchain-path`). As a compact form, you can also use `--with-devkit`
1025 to point to a single directory, if it is correctly setup. (See `basics.m4` for
1026 details.)
1028 If you are unsure what toolchain and versions to use, these have been proved
1029 working at the time of writing:
1031   * [aarch64](
1032 https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-linux-gnu-4.8-2013.11_linux.tar.xz)
1033   * [arm 32-bit hardware floating  point](
1034 https://launchpad.net/linaro-toolchain-unsupported/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux.tar.bz2)
1036 ### Native Libraries
1038 You will need copies of external native libraries for the *target* system,
1039 present on the *build* machine while building.
1041 Take care not to replace the *build* system's version of these libraries by
1042 mistake, since that can render the *build* machine unusable.
1044 Make sure that the libraries you point to (ALSA, X11, etc) are for the
1045 *target*, not the *build*, platform.
1047 #### ALSA
1049 You will need alsa libraries suitable for your *target* system. For most cases,
1050 using Debian's pre-built libraries work fine.
1052 Note that alsa is needed even if you only want to build a headless JDK.
1054   * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and
1055     search for the `libasound2` and `libasound2-dev` packages for your *target*
1056     system. Download them to /tmp.
1058   * Install the libraries into the cross-compilation toolchain. For instance:
1059 ```
1060 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc
1061 dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb .
1062 dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb .
1063 ```
1065   * If alsa is not properly detected by `configure`, you can point it out by
1066     `--with-alsa`.
1068 #### X11
1070 You will need X11 libraries suitable for your *target* system. For most cases,
1071 using Debian's pre-built libraries work fine.
1073 Note that X11 is needed even if you only want to build a headless JDK.
1075   * Go to [Debian Package Search](https://www.debian.org/distrib/packages),
1076     search for the following packages for your *target* system, and download them
1077     to /tmp/target-x11:
1078       * libxi
1079       * libxi-dev
1080       * x11proto-core-dev
1081       * x11proto-input-dev
1082       * x11proto-kb-dev
1083       * x11proto-render-dev
1084       * x11proto-xext-dev
1085       * libice-dev
1086       * libxrender
1087       * libxrender-dev
1088       * libxrandr-dev
1089       * libsm-dev
1090       * libxt-dev
1091       * libx11
1092       * libx11-dev
1093       * libxtst
1094       * libxtst-dev
1095       * libxext
1096       * libxext-dev
1098   * Install the libraries into the cross-compilation toolchain. For instance:
1099     ```
1100     cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr
1101     mkdir X11R6
1102     cd X11R6
1103     for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done
1104     mv usr/* .
1105     cd lib
1106     cp arm-linux-gnueabihf/* .
1107     ```
1109     You can ignore the following messages. These libraries are not needed to
1110     successfully complete a full JDK build.
1111     ```
1112     cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory
1113     cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory
1114     cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory
1115     ```
1117   * If the X11 libraries are not properly detected by `configure`, you can
1118     point them out by `--with-x`.
1120 ### Creating And Using Sysroots With qemu-deboostrap
1122 Fortunately, you can create sysroots for foreign architectures with tools
1123 provided by your OS. On Debian/Ubuntu systems, one could use `qemu-deboostrap` to
1124 create the *target* system chroot, which would have the native libraries and headers
1125 specific to that *target* system. After that, we can use the cross-compiler on the *build*
1126 system, pointing into chroot to get the build dependencies right. This allows building
1127 for foreign architectures with native compilation speed.
1129 For example, cross-compiling to AArch64 from x86_64 could be done like this:
1131   * Install cross-compiler on the *build* system:
1132 ```
1133 apt install g++-aarch64-linux-gnu gcc-aarch64-linux-gnu
1134 ```
1136   * Create chroot on the *build* system, configuring it for *target* system:
1137 ```
1138 sudo qemu-debootstrap --arch=arm64 --verbose \
1139        --include=fakeroot,build-essential,libx11-dev,libxext-dev,libxrender-dev,libxrandr-dev,libxtst-dev,libxt-dev,libcups2-dev,libfontconfig1-dev,libasound2-dev,libfreetype6-dev,libpng12-dev \
1140        --resolve-deps jessie /chroots/arm64 http://httpredir.debian.org/debian/
1141 ```
1143   * Configure and build with newly created chroot as sysroot/toolchain-path:
1144 ```
1145 CC=aarch64-linux-gnu-gcc CXX=aarch64-linux-gnu-g++ sh ./configure --openjdk-target=aarch64-linux-gnu --with-sysroot=/chroots/arm64/ --with-toolchain-path=/chroots/arm64/
1146 make images
1147 ls build/linux-aarch64-normal-server-release/
1148 ```
1150 The build does not create new files in that chroot, so it can be reused for multiple builds
1151 without additional cleanup.
1153 Architectures that are known to successfully cross-compile like this are:
1155   Target        `CC`                      `CXX`                       `--arch=...`  `--openjdk-target=...`
1156   ------------  ------------------------- --------------------------- ------------- -----------------------
1157   x86           default                   default                     i386          i386-linux-gnu
1158   armhf         gcc-arm-linux-gnueabihf   g++-arm-linux-gnueabihf     armhf         arm-linux-gnueabihf
1159   aarch64       gcc-aarch64-linux-gnu     g++-aarch64-linux-gnu       arm64         aarch64-linux-gnu
1160   ppc64el       gcc-powerpc64le-linux-gnu g++-powerpc64le-linux-gnu   ppc64el       powerpc64le-linux-gnu
1161   s390x         gcc-s390x-linux-gnu       g++-s390x-linux-gnu         s390x         s390x-linux-gnu
1163 Additional architectures might be supported by Debian/Ubuntu Ports.
1165 ### Building for ARM/aarch64
1167 A common cross-compilation target is the ARM CPU. When building for ARM, it is
1168 useful to set the ABI profile. A number of pre-defined ABI profiles are
1169 available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt,
1170 armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer
1171 properly supported by the JDK.
1173 ### Verifying the Build
1175 The build will end up in a directory named like
1176 `build/linux-arm-normal-server-release`.
1178 Inside this build output directory, the `images/jdk` will contain the newly
1179 built JDK, for your *target* system.
1181 Copy these folders to your *target* system. Then you can run e.g.
1182 `images/jdk/bin/java -version`.
1184 ## Build Performance
1186 Building the JDK requires a lot of horsepower. Some of the build tools can be
1187 adjusted to utilize more or less of resources such as parallel threads and
1188 memory. The `configure` script analyzes your system and selects reasonable
1189 values for such options based on your hardware. If you encounter resource
1190 problems, such as out of memory conditions, you can modify the detected values
1191 with:
1193   * `--with-num-cores` -- number of cores in the build system, e.g.
1194     `--with-num-cores=8`.
1196   * `--with-memory-size` -- memory (in MB) available in the build system, e.g.
1197     `--with-memory-size=1024`
1199 You can also specify directly the number of build jobs to use with
1200 `--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag
1201 to `make`. In most cases it will be ignored by the makefiles, but it can cause
1202 problems for some make targets.
1204 It might also be necessary to specify the JVM arguments passed to the Boot JDK,
1205 using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the
1206 default JVM arguments passed to the Boot JDK.
1208 At the end of a successful execution of `configure`, you will get a performance
1209 summary, indicating how well the build will perform. Here you will also get
1210 performance hints. If you want to build fast, pay attention to those!
1212 If you want to tweak build performance, run with `make LOG=info` to get a build
1213 time summary at the end of the build process.
1215 ### Disk Speed
1217 If you are using network shares, e.g. via NFS, for your source code, make sure
1218 the build directory is situated on local disk (e.g. by `ln -s
1219 /localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely
1220 high for building on a network share; close to unusable.
1222 Also, make sure that your build tools (including Boot JDK and toolchain) is
1223 located on a local disk and not a network share.
1225 As has been stressed elsewhere, do use SSD for source code and build directory,
1226 as well as (if possible) the build tools.
1228 ### Virus Checking
1230 The use of virus checking software, especially on Windows, can *significantly*
1231 slow down building of the JDK. If possible, turn off such software, or exclude
1232 the directory containing the JDK source code from on-the-fly checking.
1234 ### Ccache
1236 The JDK build supports building with ccache when using gcc or clang. Using
1237 ccache can radically speed up compilation of native code if you often rebuild
1238 the same sources. Your milage may vary however, so we recommend evaluating it
1239 for yourself. To enable it, make sure it's on the path and configure with
1240 `--enable-ccache`.
1242 ### Precompiled Headers
1244 By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains
1245 were it is properly supported (clang, gcc, and Visual Studio). Normally, this
1246 speeds up the build process, but in some circumstances, it can actually slow
1247 things down.
1249 You can experiment by disabling precompiled headers using
1250 `--disable-precompiled-headers`.
1252 ### Icecc / icecream
1254 [icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a
1255 distributed compiler network. If you have multiple machines available for
1256 building the JDK, you can drastically cut individual build times by utilizing
1257 it.
1259 To use, setup an icecc network, and install icecc on the build machine. Then
1260 run `configure` using `--enable-icecc`.
1262 ### Using sjavac
1264 To speed up Java compilation, especially incremental compilations, you can try
1265 the experimental sjavac compiler by using `--enable-sjavac`.
1267 ### Building the Right Target
1269 Selecting the proper target to build can have dramatic impact on build time.
1270 For normal usage, `jdk` or the default target is just fine. You only need to
1271 build `images` for shipping, or if your tests require it.
1273 See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on
1274 how to build an even smaller subset of the product.
1276 ## Troubleshooting
1278 If your build fails, it can sometimes be difficult to pinpoint the problem or
1279 find a proper solution.
1281 ### Locating the Source of the Error
1283 When a build fails, it can be hard to pinpoint the actual cause of the error.
1284 In a typical build process, different parts of the product build in parallel,
1285 with the output interlaced.
1287 #### Build Failure Summary
1289 To help you, the build system will print a failure summary at the end. It looks
1290 like this:
1292 ```
1293 ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2)
1295 === Output from failing command(s) repeated here ===
1296 * For target hotspot_variant-server_libjvm_objs_psMemoryPool.o:
1297 /localhome/hg/jdk9-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type
1298    ... (rest of output omitted)
1300 * All command lines available in /localhome/hg/jdk9-sandbox/build/linux-x64/make-support/failure-logs.
1301 === End of repeated output ===
1303 === Make failed targets repeated here ===
1304 lib/CompileJvm.gmk:207: recipe for target '/localhome/hg/jdk9-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed
1305 make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed
1306 === End of repeated output ===
1308 Hint: Try searching the build log for the name of the first failed target.
1309 Hint: If caused by a warning, try configure --disable-warnings-as-errors.
1310 ```
1312 Let's break it down! First, the selected configuration, and the top-level
1313 target you entered on the command line that caused the failure is printed.
1315 Then, between the `Output from failing command(s) repeated here` and `End of
1316 repeated output` the first lines of output (stdout and stderr) from the actual
1317 failing command is repeated. In most cases, this is the error message that
1318 caused the build to fail. If multiple commands were failing (this can happen in
1319 a parallel build), output from all failed commands will be printed here.
1321 The path to the `failure-logs` directory is printed. In this file you will find
1322 a `<target>.log` file that contains the output from this command in its
1323 entirety, and also a `<target>.cmd`, which contain the complete command line
1324 used for running this command. You can re-run the failing command by executing
1325 `. <path to failure-logs>/<target>.cmd` in your shell.
1327 Another way to trace the failure is to follow the chain of make targets, from
1328 top-level targets to individual file targets. Between `Make failed targets
1329 repeated here` and `End of repeated output` the output from make showing this
1330 chain is repeated. The first failed recipe will typically contain the full path
1331 to the file in question that failed to compile. Following lines will show a
1332 trace of make targets why we ended up trying to compile that file.
1334 Finally, some hints are given on how to locate the error in the complete log.
1335 In this example, we would try searching the log file for "`psMemoryPool.o`".
1336 Another way to quickly locate make errors in the log is to search for "`]
1337 Error`" or "`***`".
1339 Note that the build failure summary will only help you if the issue was a
1340 compilation failure or similar. If the problem is more esoteric, or is due to
1341 errors in the build machinery, you will likely get empty output logs, and `No
1342 indication of failed target found` instead of the make target chain.
1344 #### Checking the Build Log File
1346 The output (stdout and stderr) from the latest build is always stored in
1347 `$BUILD/build.log`. The previous build log is stored as `build.log.old`. This
1348 means that it is not necessary to redirect the build output yourself if you
1349 want to process it.
1351 You can increase the verbosity of the log file, by the `LOG` control variable
1352 to `make`. If you want to see the command lines used in compilations, use
1353 `LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug`
1354 or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g.
1355 `LOG=info,cmdlines`. The `debug` log level will show most shell commands
1356 executed by make, and `trace` will show all. Beware that both these log levels
1357 will produce a massive build log!
1359 ### Fixing Unexpected Build Failures
1361 Most of the time, the build will fail due to incorrect changes in the source
1362 code.
1364 Sometimes the build can fail with no apparent changes that have caused the
1365 failure. If this is the first time you are building the JDK on this particular
1366 computer, and the build fails, the problem is likely with your build
1367 environment. But even if you have previously built the JDK with success, and it
1368 now fails, your build environment might have changed (perhaps due to OS
1369 upgrades or similar). But most likely, such failures are due to problems with
1370 the incremental rebuild.
1372 #### Problems with the Build Environment
1374 Make sure your configuration is correct. Re-run `configure`, and look for any
1375 warnings. Warnings that appear in the middle of the `configure` output is also
1376 repeated at the end, after the summary. The entire log is stored in
1377 `$BUILD/configure.log`.
1379 Verify that the summary at the end looks correct. Are you indeed using the Boot
1380 JDK and native toolchain that you expect?
1382 By default, the JDK has a strict approach where warnings from the compiler is
1383 considered errors which fail the build. For very new or very old compiler
1384 versions, this can trigger new classes of warnings, which thus fails the build.
1385 Run `configure` with `--disable-warnings-as-errors` to turn of this behavior.
1386 (The warnings will still show, but not make the build fail.)
1388 #### Problems with Incremental Rebuilds
1390 Incremental rebuilds mean that when you modify part of the product, only the
1391 affected parts get rebuilt. While this works great in most cases, and
1392 significantly speed up the development process, from time to time complex
1393 interdependencies will result in an incorrect build result. This is the most
1394 common cause for unexpected build problems.
1396 Here are a suggested list of things to try if you are having unexpected build
1397 problems. Each step requires more time than the one before, so try them in
1398 order. Most issues will be solved at step 1 or 2.
1400  1. Make sure your repository is up-to-date
1402     Run `hg pull -u` to make sure you have the latest changes.
1404  2. Clean build results
1406     The simplest way to fix incremental rebuild issues is to run `make clean`.
1407     This will remove all build results, but not the configuration or any build
1408     system support artifacts. In most cases, this will solve build errors
1409     resulting from incremental build mismatches.
1411  3. Completely clean the build directory.
1413     If this does not work, the next step is to run `make dist-clean`, or
1414     removing the build output directory (`$BUILD`). This will clean all
1415     generated output, including your configuration. You will need to re-run
1416     `configure` after this step. A good idea is to run `make
1417     print-configuration` before running `make dist-clean`, as this will print
1418     your current `configure` command line. Here's a way to do this:
1420     ```
1421     make print-configuration > current-configuration
1422     make dist-clean
1423     bash configure $(cat current-configuration)
1424     make
1425     ```
1427  4. Re-clone the Mercurial repository
1429     Sometimes the Mercurial repository gets in a state that causes the product
1430     to be un-buildable. In such a case, the simplest solution is often the
1431     "sledgehammer approach": delete the entire repository, and re-clone it.
1432     If you have local changes, save them first to a different location using
1433     `hg export`.
1435 ### Specific Build Issues
1437 #### Clock Skew
1439 If you get an error message like this:
1440 ```
1441 File 'xxx' has modification time in the future.
1442 Clock skew detected. Your build may be incomplete.
1443 ```
1444 then the clock on your build machine is out of sync with the timestamps on the
1445 source files. Other errors, apparently unrelated but in fact caused by the
1446 clock skew, can occur along with the clock skew warnings. These secondary
1447 errors may tend to obscure the fact that the true root cause of the problem is
1448 an out-of-sync clock.
1450 If you see these warnings, reset the clock on the build machine, run `make
1451 clean` and restart the build.
1453 #### Out of Memory Errors
1455 On Solaris, you might get an error message like this:
1456 ```
1457 Trouble writing out table to disk
1458 ```
1459 To solve this, increase the amount of swap space on your build machine.
1461 On Windows, you might get error messages like this:
1462 ```
1463 fatal error - couldn't allocate heap
1464 cannot create ... Permission denied
1465 spawn failed
1466 ```
1467 This can be a sign of a Cygwin problem. See the information about solving
1468 problems in the [Cygwin](#cygwin) section. Rebooting the computer might help
1469 temporarily.
1471 ### Getting Help
1473 If none of the suggestions in this document helps you, or if you find what you
1474 believe is a bug in the build system, please contact the Build Group by sending
1475 a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net).
1476 Please include the relevant parts of the configure and/or build log.
1478 If you need general help or advice about developing for the JDK, you can also
1479 contact the Adoption Group. See the section on [Contributing to OpenJDK](
1480 #contributing-to-openjdk) for more information.
1482 ## Hints and Suggestions for Advanced Users
1484 ### Setting Up a Repository for Pushing Changes (defpath)
1486 To help you prepare a proper push path for a Mercurial repository, there exists
1487 a useful tool known as [defpath](
1488 http://openjdk.java.net/projects/code-tools/defpath). It will help you setup a
1489 proper push path for pushing changes to the JDK.
1491 Install the extension by cloning
1492 `http://hg.openjdk.java.net/code-tools/defpath` and updating your `.hgrc` file.
1493 Here's one way to do this:
1495 ```
1496 cd ~
1497 mkdir hg-ext
1498 cd hg-ext
1499 hg clone http://hg.openjdk.java.net/code-tools/defpath
1500 cat << EOT >> ~/.hgrc
1501 [extensions]
1502 defpath=~/hg-ext/defpath/defpath.py
1503 EOT
1504 ```
1506 You can now setup a proper push path using:
1507 ```
1508 hg defpath -d -u <your OpenJDK username>
1509 ```
1511 ### Bash Completion
1513 The `configure` and `make` commands tries to play nice with bash command-line
1514 completion (using `<tab>` or `<tab><tab>`). To use this functionality, make
1515 sure you enable completion in your `~/.bashrc` (see instructions for bash in
1516 your operating system).
1518 Make completion will work out of the box, and will complete valid make targets.
1519 For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`.
1521 The `configure` script can get completion for options, but for this to work you
1522 need to help `bash` on the way. The standard way of running the script, `bash
1523 configure`, will not be understood by bash completion. You need `configure` to
1524 be the command to run. One way to achieve this is to add a simple helper script
1525 to your path:
1527 ```
1528 cat << EOT > /tmp/configure
1529 #!/bin/bash
1530 if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then
1531   echo >&2 "Abort: Trying to call configure helper recursively"
1532   exit 1
1533 fi
1535 bash \$PWD/configure "\$@"
1536 EOT
1537 chmod +x /tmp/configure
1538 sudo mv /tmp/configure /usr/local/bin
1539 ```
1541 Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`.
1543 ### Using Multiple Configurations
1545 You can have multiple configurations for a single source repository. When you
1546 create a new configuration, run `configure --with-conf-name=<name>` to create a
1547 configuration with the name `<name>`. Alternatively, you can create a directory
1548 under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd
1549 build/<name> && bash ../../configure`.
1551 Then you can build that configuration using `make CONF_NAME=<name>` or `make
1552 CONF=<pattern>`, where `<pattern>` is a substring matching one or several
1553 configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will
1554 match *all* available configuration, so `make CONF= hotspot` will build the
1555 `hotspot` target for all configurations. Alternatively, you can execute `make`
1556 in the configuration directory, e.g. `cd build/<name> && make`.
1558 ### Handling Reconfigurations
1560 If you update the repository and part of the configure script has changed, the
1561 build system will force you to re-run `configure`.
1563 Most of the time, you will be fine by running `configure` again with the same
1564 arguments as the last time, which can easily be performed by `make
1565 reconfigure`. To simplify this, you can use the `CONF_CHECK` make control
1566 variable, either as `make CONF_CHECK=auto`, or by setting an environment
1567 variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc`
1568 file, `make` will always run `reconfigure` automatically whenever the configure
1569 script has changed.
1571 You can also use `CONF_CHECK=ignore` to skip the check for a needed configure
1572 update. This might speed up the build, but comes at the risk of an incorrect
1573 build result. This is only recommended if you know what you're doing.
1575 From time to time, you will also need to modify the command line to `configure`
1576 due to changes. Use `make print-configure` to show the command line used for
1577 your current configuration.
1579 ### Using Fine-Grained Make Targets
1581 The default behavior for make is to create consistent and correct output, at
1582 the expense of build speed, if necessary.
1584 If you are prepared to take some risk of an incorrect build, and know enough of
1585 the system to understand how things build and interact, you can speed up the
1586 build process considerably by instructing make to only build a portion of the
1587 product.
1589 #### Building Individual Modules
1591 The safe way to use fine-grained make targets is to use the module specific
1592 make targets. All source code in the JDK is organized so it belongs to a
1593 module, e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific
1594 module, by giving it as make target: `make jdk.jdwp.agent`. If the specified
1595 module depends on other modules (e.g. `java.base`), those modules will be built
1596 first.
1598 You can also specify a set of modules, just as you can always specify a set of
1599 make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi
1600 jdk.crypto.ucrypto`
1602 #### Building Individual Module Phases
1604 The build process for each module is divided into separate phases. Not all
1605 modules need all phases. Which are needed depends on what kind of source code
1606 and other artifact the module consists of. The phases are:
1608   * `gensrc` (Generate source code to compile)
1609   * `gendata` (Generate non-source code artifacts)
1610   * `copy` (Copy resource artifacts)
1611   * `java` (Compile Java code)
1612   * `launchers` (Compile native executables)
1613   * `libs` (Compile native libraries)
1614   * `rmic` (Run the `rmic` tool)
1616 You can build only a single phase for a module by using the notation
1617 `$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`,
1618 use `make java.base-gensrc`.
1620 Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if
1621 present). Make will build all needed prerequisites before building the
1622 requested phase.
1624 #### Skipping the Dependency Check
1626 When using an iterative development style with frequent quick rebuilds, the
1627 dependency check made by make can take up a significant portion of the time
1628 spent on the rebuild. In such cases, it can be useful to bypass the dependency
1629 check in make.
1631 > **Note that if used incorrectly, this can lead to a broken build!**
1633 To achieve this, append `-only` to the build target. For instance, `make
1634 jdk.jdwp.agent-java-only` will *only* build the `java` phase of the
1635 `jdk.jdwp.agent` module. If the required dependencies are not present, the
1636 build can fail. On the other hand, the execution time measures in milliseconds.
1638 A useful pattern is to build the first time normally (e.g. `make
1639 jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target.
1641 #### Rebuilding Part of java.base (JDK\_FILTER)
1643 If you are modifying files in `java.base`, which is the by far largest module
1644 in the JDK, then you need to rebuild all those files whenever a single file has
1645 changed. (This inefficiency will hopefully be addressed in JDK 10.)
1647 As a hack, you can use the make control variable `JDK_FILTER` to specify a
1648 pattern that will be used to limit the set of files being recompiled. For
1649 instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods,
1650 `make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation
1651 to files in the `javax.crypto` package.
1653 ### Learn About Mercurial
1655 To become an efficient JDK developer, it is recommended that you invest in
1656 learning Mercurial properly. Here are some links that can get you started:
1658   * [Mercurial for git users](http://www.mercurial-scm.org/wiki/GitConcepts)
1659   * [The official Mercurial tutorial](http://www.mercurial-scm.org/wiki/Tutorial)
1660   * [hg init](http://hginit.com/)
1661   * [Mercurial: The Definitive Guide](http://hgbook.red-bean.com/read/)
1663 ## Understanding the Build System
1665 This section will give you a more technical description on the details of the
1666 build system.
1668 ### Configurations
1670 The build system expects to find one or more configuration. These are
1671 technically defined by the `spec.gmk` in a subdirectory to the `build`
1672 subdirectory. The `spec.gmk` file is generated by `configure`, and contains in
1673 principle the configuration (directly or by files included by `spec.gmk`).
1675 You can, in fact, select a configuration to build by pointing to the `spec.gmk`
1676 file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`.
1677 While this is not the recommended way to call `make` as a user, it is what is
1678 used under the hood by the build system.
1680 ### Build Output Structure
1682 The build output for a configuration will end up in `build/<configuration
1683 name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory
1684 contains the following important directories:
1686 ```
1687 buildtools/
1688 configure-support/
1689 hotspot/
1690 images/
1691 jdk/
1692 make-support/
1693 support/
1694 test-results/
1695 test-support/
1696 ```
1698 This is what they are used for:
1700   * `images`: This is the directory were the output of the `*-image` make
1701     targets end up. For instance, `make jdk-image` ends up in `images/jdk`.
1703   * `jdk`: This is the "exploded image". After `make jdk`, you will be able to
1704     launch the newly built JDK by running `$BUILD/jdk/bin/java`.
1706   * `test-results`: This directory contains the results from running tests.
1708   * `support`: This is an area for intermediate files needed during the build,
1709     e.g. generated source code, object files and class files. Some noteworthy
1710     directories in `support` is `gensrc`, which contains the generated source
1711     code, and the `modules_*` directories, which contains the files in a
1712     per-module hierarchy that will later be collapsed into the `jdk` directory
1713     of the exploded image.
1715   * `buildtools`: This is an area for tools compiled for the build platform
1716     that are used during the rest of the build.
1718   * `hotspot`: This is an area for intermediate files needed when building
1719     hotspot.
1721   * `configure-support`, `make-support` and `test-support`: These directories
1722     contain files that are needed by the build system for `configure`, `make`
1723     and for running tests.
1725 ### Fixpath
1727 Windows path typically look like `C:\User\foo`, while Unix paths look like
1728 `/home/foo`. Tools with roots from Unix often experience issues related to this
1729 mismatch when running on Windows.
1731 In the JDK build, we always use Unix paths internally, and only just before
1732 calling a tool that does not understand Unix paths do we convert them to
1733 Windows paths.
1735 This conversion is done by the `fixpath` tool, which is a small wrapper that
1736 modifies unix-style paths to Windows-style paths in command lines. Fixpath is
1737 compiled automatically by `configure`.
1739 ### Native Debug Symbols
1741 Native libraries and executables can have debug symbol (and other debug
1742 information) associated with them. How this works is very much platform
1743 dependent, but a common problem is that debug symbol information takes a lot of
1744 disk space, but is rarely needed by the end user.
1746 The JDK supports different methods on how to handle debug symbols. The
1747 method used is selected by `--with-native-debug-symbols`, and available methods
1748 are `none`, `internal`, `external`, `zipped`.
1750   * `none` means that no debug symbols will be generated during the build.
1752   * `internal` means that debug symbols will be generated during the build, and
1753     they will be stored in the generated binary.
1755   * `external` means that debug symbols will be generated during the build, and
1756     after the compilation, they will be moved into a separate `.debuginfo` file.
1757     (This was previously known as FDS, Full Debug Symbols).
1759   * `zipped` is like `external`, but the .debuginfo file will also be zipped
1760     into a `.diz` file.
1762 When building for distribution, `zipped` is a good solution. Binaries built
1763 with `internal` is suitable for use by developers, since they facilitate
1764 debugging, but should be stripped before distributed to end users.
1766 ### Autoconf Details
1768 The `configure` script is based on the autoconf framework, but in some details
1769 deviate from a normal autoconf `configure` script.
1771 The `configure` script in the top level directory of the JDK is just a thin
1772 wrapper that calls `make/autoconf/configure`. This in turn will run `autoconf`
1773 to create the runnable (generated) configure script, as
1774 `.build/generated-configure.sh`. Apart from being responsible for the
1775 generation of the runnable script, the `configure` script also provides
1776 functionality that is not easily expressed in the normal Autoconf framework. As
1777 part of this functionality, the generated script is called.
1779 The build system will detect if the Autoconf source files have changed, and
1780 will trigger a regeneration of the generated script if needed. You can also
1781 manually request such an update by `bash configure autogen`.
1783 In previous versions of the JDK, the generated script was checked in at
1784 `make/autoconf/generated-configure.sh`. This is no longer the case.
1786 ### Developing the Build System Itself
1788 This section contains a few remarks about how to develop for the build system
1789 itself. It is not relevant if you are only making changes in the product source
1790 code.
1792 While technically using `make`, the make source files of the JDK does not
1793 resemble most other Makefiles. Instead of listing specific targets and actions
1794 (perhaps using patterns), the basic modus operandi is to call a high-level
1795 function (or properly, macro) from the API in `make/common`. For instance, to
1796 compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module,
1797 a call like this would be made:
1799 ```
1800 $(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \
1802     SRC := $(TOPDIR)/src/jkd.foo/share/classes, \
1803     INCLUDES := jdk/internal/foo, \
1804     BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \
1805 ))
1806 ```
1808 By encapsulating and expressing the high-level knowledge of *what* should be
1809 done, rather than *how* it should be done (as is normal in Makefiles), we can
1810 build a much more powerful and flexible build system.
1812 Correct dependency tracking is paramount. Sloppy dependency tracking will lead
1813 to improper parallelization, or worse, race conditions.
1815 To test for/debug race conditions, try running `make JOBS=1` and `make
1816 JOBS=100` and see if it makes any difference. (It shouldn't).
1818 To compare the output of two different builds and see if, and how, they differ,
1819 run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two
1820 builds you want to compare.
1822 To automatically build two consecutive versions and compare them, use
1823 `COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value
1824 assignments, like this:
1825 ```
1826 make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot
1827 ```
1828 See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`.
1830 To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`.
1831 Use `JOBS=1` to avoid parallelism.
1833 Please check that you adhere to the [Code Conventions for the Build System](
1834 http://openjdk.java.net/groups/build/doc/code-conventions.html) before
1835 submitting patches.
1837 ## Contributing to the JDK
1839 So, now you've built your JDK, and made your first patch, and want to
1840 contribute it back to the OpenJDK Community.
1842 First of all: Thank you! We gladly welcome your contribution.
1843 However, please bear in mind that the JDK is a massive project, and we must ask
1844 you to follow our rules and guidelines to be able to accept your contribution.
1846 The official place to start is the ['How to contribute' page](
1847 http://openjdk.java.net/contribute/). There is also an official (but somewhat
1848 outdated and skimpy on details) [Developer's Guide](
1849 http://openjdk.java.net/guide/).
1851 If this seems overwhelming to you, the Adoption Group is there to help you! A
1852 good place to start is their ['New Contributor' page](
1853 https://wiki.openjdk.java.net/display/Adoption/New+Contributor), or start
1854 reading the comprehensive [Getting Started Kit](
1855 https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The
1856 Adoption Group will also happily answer any questions you have about
1857 contributing. Contact them by [mail](
1858 http://mail.openjdk.java.net/mailman/listinfo/adoption-discuss) or [IRC](
1859 http://openjdk.java.net/irc/).
1861 ---
1862 # Override styles from the base CSS file that are not ideal for this document.
1863 header-includes:
1864  - '<style type="text/css">pre, code, tt { color: #1d6ae5; }</style>'
1865 ---