1% Building the JDK 2 3## TL;DR (Instructions for the Impatient) 4 5If you are eager to try out building the JDK, these simple steps works most of 6the time. They assume that you have installed Git (and Cygwin if running 7on Windows) and cloned the top-level JDK repository that you want to build. 8 9 1. [Get the complete source code](#getting-the-source-code): \ 10 `git clone https://git.openjdk.java.net/jdk/` 11 12 2. [Run configure](#running-configure): \ 13 `bash configure` 14 15 If `configure` fails due to missing dependencies (to either the 16 [toolchain](#native-compiler-toolchain-requirements), [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. 22 23 3. [Run make](#running-make): \ 24 `make images` 25 26 4. Verify your newly built JDK: \ 27 `./build/*/images/jdk/bin/java -version` 28 29 5. [Run basic tests](##running-tests): \ 30 `make run-test-tier1` 31 32If any of these steps failed, or if you want to know more about build 33requirements or build functionality, please continue reading this document. 34 35## Introduction 36 37The JDK is a complex software project. Building it requires a certain amount of 38technical expertise, a fair number of dependencies on external software, and 39reasonably powerful hardware. 40 41If you just want to use the JDK and not build it yourself, this document is not 42for you. See for instance [OpenJDK installation]( 43http://openjdk.java.net/install) for some methods of installing a prebuilt 44JDK. 45 46## Getting the Source Code 47 48Make sure you are getting the correct version. As of JDK 10, the source is no 49longer split into separate repositories so you only need to clone one single 50repository. At the [OpenJDK Git site](https://git.openjdk.java.net/) you 51can see a list of all available repositories. If you want to build an older version, 52e.g. JDK 11, it is recommended that you get the `jdk11u` repo, which contains 53incremental updates, instead of the `jdk11` repo, which was frozen at JDK 11 GA. 54 55If you are new to Git, a good place to start is the book [Pro 56Git](https://git-scm.com/book/en/v2). The rest of this document 57assumes a working knowledge of Git. 58 59### Special Considerations 60 61For a smooth building experience, it is recommended that you follow these rules 62on where and how to check out the source code. 63 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. 67 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. 71 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. 77 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: 81 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. 87 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. 91 92 * You need to install a git client. You have two choices, Cygwin git or 93 Git for Windows. Unfortunately there are pros and cons with each choice. 94 95 * The Cygwin `git` client has no line ending issues and understands 96 Cygwin paths (which are used throughout the JDK build system). 97 However, it does not currently work well with the Skara CLI tooling. 98 Please see the [Skara wiki on Git clients]( 99 https://wiki.openjdk.java.net/display/SKARA/Skara#Skara-Git) for 100 up-to-date information about the Skara git client support. 101 102 * The [Git for Windows](https://gitforwindows.org) client has issues 103 with line endings, and do not understand Cygwin paths. It does work 104 well with the Skara CLI tooling, however. To alleviate the line ending 105 problems, make sure you set `core.autocrlf` to `false` (this is asked 106 during installation). 107 108 Failure to follow this procedure might result in hard-to-debug build 109 problems. 110 111## Build Hardware Requirements 112 113The JDK is a massive project, and require machines ranging from decent to 114powerful to be able to build in a reasonable amount of time, or to be able to 115complete a build at all. 116 117We *strongly* recommend usage of an SSD disk for the build, since disk speed is 118one of the limiting factors for build performance. 119 120### Building on x86 121 122At a minimum, a machine with 2-4 cores is advisable, as well as 2-4 GB of RAM. 123(The more cores to use, the more memory you need.) At least 6 GB of free disk 124space is required (8 GB minimum for building on Solaris). 125 126Even for 32-bit builds, it is recommended to use a 64-bit build machine, and 127instead create a 32-bit target using `--with-target-bits=32`. 128 129### Building on sparc 130 131At a minimum, a machine with 4 cores is advisable, as well as 4 GB of RAM. (The 132more cores to use, the more memory you need.) At least 8 GB of free disk space 133is required. 134 135### Building on aarch64 136 137At a minimum, a machine with 8 cores is advisable, as well as 8 GB of RAM. 138(The more cores to use, the more memory you need.) At least 6 GB of free disk 139space is required. 140 141If you do not have access to sufficiently powerful hardware, it is also 142possible to use [cross-compiling](#cross-compiling). 143 144### Building on 32-bit arm 145 146This is not recommended. Instead, see the section on [Cross-compiling]( 147#cross-compiling). 148 149## Operating System Requirements 150 151The mainline JDK project supports Linux, Solaris, macOS, AIX and Windows. 152Support for other operating system, e.g. BSD, exists in separate "port" 153projects. 154 155In general, the JDK can be built on a wide range of versions of these operating 156systems, but the further you deviate from what is tested on a daily basis, the 157more likely you are to run into problems. 158 159This table lists the OS versions used by Oracle when building the JDK. Such 160information is always subject to change, but this table is up to date at the 161time of writing. 162 163 Operating system Vendor/version used 164 ----------------- ------------------------------------------------------- 165 Linux Oracle Enterprise Linux 6.4 / 7.6 166 Solaris Solaris 11.3 SRU 20 167 macOS Mac OS X 10.13 (High Sierra) 168 Windows Windows Server 2012 R2 169 170The double version numbers for Linux and Solaris are due to the hybrid model 171used at Oracle, where header files and external libraries from an older version 172are used when building on a more modern version of the OS. 173 174The Build Group has a wiki page with [Supported Build Platforms]( 175https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms). From 176time to time, this is updated by contributors to list successes or failures of 177building on different platforms. 178 179### Windows 180 181Windows XP is not a supported platform, but all newer Windows should be able to 182build the JDK. 183 184On Windows, it is important that you pay attention to the instructions in the 185[Special Considerations](#special-considerations). 186 187Windows is the only non-POSIX OS supported by the JDK, and as such, requires 188some extra care. A POSIX support layer is required to build on Windows. 189Currently, the only supported such layers are Cygwin and Windows Subsystem for 190Linux (WSL). (Msys is no longer supported due to a too old bash; msys2 would 191likely be possible to support in a future version but that would require effort 192to implement.) 193 194Internally in the build system, all paths are represented as Unix-style paths, 195e.g. `/cygdrive/c/git/jdk/Makefile` rather than `C:\git\jdk\Makefile`. This 196rule also applies to input to the build system, e.g. in arguments to 197`configure`. So, use `--with-msvcr-dll=/cygdrive/c/msvcr100.dll` rather than 198`--with-msvcr-dll=c:\msvcr100.dll`. For details on this conversion, see the section 199on [Fixpath](#fixpath). 200 201#### Cygwin 202 203A functioning [Cygwin](http://www.cygwin.com/) environment is required for 204building the JDK on Windows. If you have a 64-bit OS, we strongly recommend 205using the 64-bit version of Cygwin. 206 207**Note:** Cygwin has a model of continuously updating all packages without any 208easy way to install or revert to a specific version of a package. This means 209that whenever you add or update a package in Cygwin, you might (inadvertently) 210update tools that are used by the JDK build process, and that can cause 211unexpected build problems. 212 213The JDK requires GNU Make 4.0 or greater in Cygwin. This is usually not a 214problem, since Cygwin currently only distributes GNU Make at a version above 2154.0. 216 217Apart from the basic Cygwin installation, the following packages must also be 218installed: 219 220 * `autoconf` 221 * `make` 222 * `zip` 223 * `unzip` 224 225Often, you can install these packages using the following command line: 226``` 227<path to Cygwin setup>/setup-x86_64 -q -P autoconf -P make -P unzip -P zip 228``` 229 230Unfortunately, Cygwin can be unreliable in certain circumstances. If you 231experience build tool crashes or strange issues when building on Windows, 232please check the Cygwin FAQ on the ["BLODA" list]( 233https://cygwin.com/faq/faq.html#faq.using.bloda) and the section on [fork() 234failures](https://cygwin.com/faq/faq.html#faq.using.fixing-fork-failures). 235 236#### Windows Subsystem for Linux (WSL) 237 238Windows 10 1809 or newer is supported due to a dependency on the wslpath utility 239and support for environment variable sharing through WSLENV. Version 1803 can 240work but intermittent build failures have been observed. 241 242It's possible to build both Windows and Linux binaries from WSL. To build 243Windows binaries, you must use a Windows boot JDK (located in a 244Windows-accessible directory). To build Linux binaries, you must use a Linux 245boot JDK. The default behavior is to build for Windows. To build for Linux, pass 246`--build=x86_64-unknown-linux-gnu --host=x86_64-unknown-linux-gnu` to 247`configure`. 248 249If building Windows binaries, the source code must be located in a Windows- 250accessible directory. This is because Windows executables (such as Visual Studio 251and the boot JDK) must be able to access the source code. Also, the drive where 252the source is stored must be mounted as case-insensitive by changing either 253/etc/fstab or /etc/wsl.conf in WSL. Individual directories may be corrected 254using the fsutil tool in case the source was cloned before changing the mount 255options. 256 257Note that while it's possible to build on WSL, testing is still not fully 258supported. 259 260### Solaris 261 262See `make/devkit/solaris11.1-package-list.txt` for a list of recommended 263packages to install when building on Solaris. The versions specified in this 264list is the versions used by the daily builds at Oracle, and is likely to work 265properly. 266 267Older versions of Solaris shipped a broken version of `objcopy`. At least 268version 2.21.1 is needed, which is provided by Solaris 11 Update 1. Objcopy is 269needed if you want to have external debug symbols. Please make sure you are 270using at least version 2.21.1 of objcopy, or that you disable external debug 271symbols. 272 273### macOS 274 275Apple is using a quite aggressive scheme of pushing OS updates, and coupling 276these updates with required updates of Xcode. Unfortunately, this makes it 277difficult for a project such as the JDK to keep pace with a continuously updated 278machine running macOS. See the section on [Apple Xcode](#apple-xcode) on some 279strategies to deal with this. 280 281It is recommended that you use at least Mac OS X 10.13 (High Sierra). At the time 282of writing, the JDK has been successfully compiled on macOS 10.12 (Sierra). 283 284The standard macOS environment contains the basic tooling needed to build, but 285for external libraries a package manager is recommended. The JDK uses 286[homebrew](https://brew.sh/) in the examples, but feel free to use whatever 287manager you want (or none). 288 289### Linux 290 291It is often not much problem to build the JDK on Linux. The only general advice 292is to try to use the compilers, external libraries and header files as provided 293by your distribution. 294 295The basic tooling is provided as part of the core operating system, but you 296will most likely need to install developer packages. 297 298For apt-based distributions (Debian, Ubuntu, etc), try this: 299``` 300sudo apt-get install build-essential 301``` 302 303For rpm-based distributions (Fedora, Red Hat, etc), try this: 304``` 305sudo yum groupinstall "Development Tools" 306``` 307 308### AIX 309 310Please consult the AIX section of the [Supported Build Platforms]( 311https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms) OpenJDK 312Build Wiki page for details about which versions of AIX are supported. 313 314## Native Compiler (Toolchain) Requirements 315 316Large portions of the JDK consists of native code, that needs to be compiled to 317be able to run on the target platform. In theory, toolchain and operating 318system should be independent factors, but in practice there's more or less a 319one-to-one correlation between target operating system and toolchain. 320 321 Operating system Supported toolchain 322 ------------------ ------------------------- 323 Linux gcc, clang 324 macOS Apple Xcode (using clang) 325 Solaris Oracle Solaris Studio 326 AIX IBM XL C/C++ 327 Windows Microsoft Visual Studio 328 329Please see the individual sections on the toolchains for version 330recommendations. As a reference, these versions of the toolchains are used, at 331the time of writing, by Oracle for the daily builds of the JDK. It should be 332possible to compile the JDK with both older and newer versions, but the closer 333you stay to this list, the more likely you are to compile successfully without 334issues. 335 336 Operating system Toolchain version 337 ------------------ ------------------------------------------------------- 338 Linux gcc 8.2.0 339 macOS Apple Xcode 10.1 (using clang 10.0.0) 340 Solaris Oracle Solaris Studio 12.6 (with compiler version 5.15) 341 Windows Microsoft Visual Studio 2017 update 15.9.6 342 343All compilers are expected to be able to compile to the C99 language standard, 344as some C99 features are used in the source code. Microsoft Visual Studio 345doesn't fully support C99 so in practice shared code is limited to using C99 346features that it does support. 347 348### gcc 349 350The minimum accepted version of gcc is 4.8. Older versions will generate a warning 351by `configure` and are unlikely to work. 352 353The JDK is currently known to be able to compile with at least version 7.4 of 354gcc. 355 356In general, any version between these two should be usable. 357 358### clang 359 360The minimum accepted version of clang is 3.2. Older versions will not be 361accepted by `configure`. 362 363To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`. 364 365### Apple Xcode 366 367The oldest supported version of Xcode is 8. 368 369You will need the Xcode command lines developers tools to be able to build 370the JDK. (Actually, *only* the command lines tools are needed, not the IDE.) 371The simplest way to install these is to run: 372``` 373xcode-select --install 374``` 375 376It is advisable to keep an older version of Xcode for building the JDK when 377updating Xcode. This [blog page]( 378http://iosdevelopertips.com/xcode/install-multiple-versions-of-xcode.html) has 379good suggestions on managing multiple Xcode versions. To use a specific version 380of Xcode, use `xcode-select -s` before running `configure`, or use 381`--with-toolchain-path` to point to the version of Xcode to use, e.g. 382`configure --with-toolchain-path=/Applications/Xcode8.app/Contents/Developer/usr/bin` 383 384If you have recently (inadvertently) updated your OS and/or Xcode version, and 385the JDK can no longer be built, please see the section on [Problems with the 386Build Environment](#problems-with-the-build-environment), and [Getting 387Help](#getting-help) to find out if there are any recent, non-merged patches 388available for this update. 389 390### Oracle Solaris Studio 391 392The minimum accepted version of the Solaris Studio compilers is 5.13 393(corresponding to Solaris Studio 12.4). Older versions will not be accepted by 394configure. 395 396The Solaris Studio installation should contain at least these packages: 397 398 Package Version 399 -------------------------------------------------- ------------- 400 developer/solarisstudio-124/backend 12.4-1.0.6.0 401 developer/solarisstudio-124/c++ 12.4-1.0.10.0 402 developer/solarisstudio-124/cc 12.4-1.0.4.0 403 developer/solarisstudio-124/library/c++-libs 12.4-1.0.10.0 404 developer/solarisstudio-124/library/math-libs 12.4-1.0.0.1 405 developer/solarisstudio-124/library/studio-gccrt 12.4-1.0.0.1 406 developer/solarisstudio-124/studio-common 12.4-1.0.0.1 407 developer/solarisstudio-124/studio-ja 12.4-1.0.0.1 408 developer/solarisstudio-124/studio-legal 12.4-1.0.0.1 409 developer/solarisstudio-124/studio-zhCN 12.4-1.0.0.1 410 411Compiling with Solaris Studio can sometimes be finicky. This is the exact 412version used by Oracle, which worked correctly at the time of writing: 413``` 414$ cc -V 415cc: Sun C 5.13 SunOS_i386 2014/10/20 416$ CC -V 417CC: Sun C++ 5.13 SunOS_i386 151846-10 2015/10/30 418``` 419 420### Microsoft Visual Studio 421 422The minimum accepted version of Visual Studio is 2010. Older versions will not 423be accepted by `configure`. The maximum accepted version of Visual Studio is 4242019. Versions older than 2017 are unlikely to continue working for long. 425 426If you have multiple versions of Visual Studio installed, `configure` will by 427default pick the latest. You can request a specific version to be used by 428setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2015`. 429 430If you get `LINK: fatal error LNK1123: failure during conversion to COFF: file 431invalid` when building using Visual Studio 2010, you have encountered 432[KB2757355](http://support.microsoft.com/kb/2757355), a bug triggered by a 433specific installation order. However, the solution suggested by the KB article 434does not always resolve the problem. See [this stackoverflow discussion]( 435https://stackoverflow.com/questions/10888391) for other suggestions. 436 437### IBM XL C/C++ 438 439Please consult the AIX section of the [Supported Build Platforms]( 440https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms) OpenJDK 441Build Wiki page for details about which versions of XLC are supported. 442 443 444## Boot JDK Requirements 445 446Paradoxically, building the JDK requires a pre-existing JDK. This is called the 447"boot JDK". The boot JDK does not, however, have to be a JDK built directly from 448the source code available in the OpenJDK Community. If you are porting the JDK 449to a new platform, chances are that there already exists another JDK for that 450platform that is usable as boot JDK. 451 452The rule of thumb is that the boot JDK for building JDK major version *N* 453should be a JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be 454suitable as boot JDK. However, the JDK should be able to "build itself", so an 455up-to-date build of the current JDK source is an acceptable alternative. If 456you are following the *N-1* rule, make sure you've got the latest update 457version, since JDK 8 GA might not be able to build JDK 9 on all platforms. 458 459Early in the release cycle, version *N-1* may not yet have been released. In 460that case, the preferred boot JDK will be version *N-2* until version *N-1* 461is available. 462 463If the boot JDK is not automatically detected, or the wrong JDK is picked, use 464`--with-boot-jdk` to point to the JDK to use. 465 466### Getting JDK binaries 467 468JDK binaries for Linux, Windows and macOS can be downloaded from 469[jdk.java.net](http://jdk.java.net). An alternative is to download the 470[Oracle JDK](http://www.oracle.com/technetwork/java/javase/downloads). Another 471is the [Adopt OpenJDK Project](https://adoptopenjdk.net/), which publishes 472experimental prebuilt binaries for various platforms. 473 474On Linux you can also get a JDK from the Linux distribution. On apt-based 475distros (like Debian and Ubuntu), `sudo apt-get install openjdk-<VERSION>-jdk` 476is typically enough to install a JDK \<VERSION\>. On rpm-based distros (like 477Fedora and Red Hat), try `sudo yum install java-<VERSION>-openjdk-devel`. 478 479## External Library Requirements 480 481Different platforms require different external libraries. In general, libraries 482are not optional - that is, they are either required or not used. 483 484If a required library is not detected by `configure`, you need to provide the 485path to it. There are two forms of the `configure` arguments to point to an 486external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to 487include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise, 488but require the include files and library files to reside in a default 489hierarchy under this directory. In most cases, it works fine. 490 491As a fallback, the second version allows you to point to the include directory 492and the lib directory separately. 493 494### FreeType 495 496FreeType2 from [The FreeType Project](http://www.freetype.org/) is not required 497on any platform. The exception is on Unix-based platforms when configuring such 498that the build artifacts will reference a system installed library, 499rather than bundling the JDK's own copy. 500 501 * To install on an apt-based Linux, try running `sudo apt-get install 502 libfreetype6-dev`. 503 * To install on an rpm-based Linux, try running `sudo yum install 504 freetype-devel`. 505 * To install on Solaris, try running `pkg install system/library/freetype-2`. 506 507Use `--with-freetype-include=<path>` and `--with-freetype-lib=<path>` 508if `configure` does not automatically locate the platform FreeType files. 509 510### CUPS 511 512CUPS, [Common UNIX Printing System](http://www.cups.org) header files are 513required on all platforms, except Windows. Often these files are provided by 514your operating system. 515 516 * To install on an apt-based Linux, try running `sudo apt-get install 517 libcups2-dev`. 518 * To install on an rpm-based Linux, try running `sudo yum install 519 cups-devel`. 520 * To install on Solaris, try running `pkg install print/cups`. 521 522Use `--with-cups=<path>` if `configure` does not properly locate your CUPS 523files. 524 525### X11 526 527Certain [X11](http://www.x.org/) libraries and include files are required on 528Linux and Solaris. 529 530 * To install on an apt-based Linux, try running `sudo apt-get install 531 libx11-dev libxext-dev libxrender-dev libxrandr-dev libxtst-dev libxt-dev`. 532 * To install on an rpm-based Linux, try running `sudo yum install 533 libXtst-devel libXt-devel libXrender-devel libXrandr-devel libXi-devel`. 534 * To install on Solaris, try running `pkg install x11/header/x11-protocols 535 x11/library/libice x11/library/libpthread-stubs x11/library/libsm 536 x11/library/libx11 x11/library/libxau x11/library/libxcb 537 x11/library/libxdmcp x11/library/libxevie x11/library/libxext 538 x11/library/libxrender x11/library/libxrandr x11/library/libxscrnsaver 539 x11/library/libxtst x11/library/toolkit/libxt`. 540 541Use `--with-x=<path>` if `configure` does not properly locate your X11 files. 542 543### ALSA 544 545ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is 546required on Linux. At least version 0.9.1 of ALSA is required. 547 548 * To install on an apt-based Linux, try running `sudo apt-get install 549 libasound2-dev`. 550 * To install on an rpm-based Linux, try running `sudo yum install 551 alsa-lib-devel`. 552 553Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA 554files. 555 556### libffi 557 558libffi, the [Portable Foreign Function Interface Library]( 559http://sourceware.org/libffi) is required when building the Zero version of 560Hotspot. 561 562 * To install on an apt-based Linux, try running `sudo apt-get install 563 libffi-dev`. 564 * To install on an rpm-based Linux, try running `sudo yum install 565 libffi-devel`. 566 567Use `--with-libffi=<path>` if `configure` does not properly locate your libffi 568files. 569 570## Build Tools Requirements 571 572### Autoconf 573 574The JDK requires [Autoconf](http://www.gnu.org/software/autoconf) on all 575platforms. At least version 2.69 is required. 576 577 * To install on an apt-based Linux, try running `sudo apt-get install 578 autoconf`. 579 * To install on an rpm-based Linux, try running `sudo yum install 580 autoconf`. 581 * To install on macOS, try running `brew install autoconf`. 582 * To install on Windows, try running `<path to Cygwin setup>/setup-x86_64 -q 583 -P autoconf`. 584 585If `configure` has problems locating your installation of autoconf, you can 586specify it using the `AUTOCONF` environment variable, like this: 587 588``` 589AUTOCONF=<path to autoconf> configure ... 590``` 591 592### GNU Make 593 594The JDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors 595of make are supported. 596 597At least version 3.81 of GNU Make must be used. For distributions supporting 598GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful 599functionality to handle parallel building (supported by `--with-output-sync`) 600and speed and stability improvements. 601 602Note that `configure` locates and verifies a properly functioning version of 603`make` and stores the path to this `make` binary in the configuration. If you 604start a build using `make` on the command line, you will be using the version 605of make found first in your `PATH`, and not necessarily the one stored in the 606configuration. This initial make will be used as "bootstrap make", and in a 607second stage, the make located by `configure` will be called. Normally, this 608will present no issues, but if you have a very old `make`, or a non-GNU Make 609`make` in your path, this might cause issues. 610 611If you want to override the default make found by `configure`, use the `MAKE` 612configure variable, e.g. `configure MAKE=/opt/gnu/make`. 613 614On Solaris, it is common to call the GNU version of make by using `gmake`. 615 616### GNU Bash 617 618The JDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells 619are supported. 620 621At least version 3.2 of GNU Bash must be used. 622 623## Running Configure 624 625To build the JDK, you need a "configuration", which consists of a directory 626where to store the build output, coupled with information about the platform, 627the specific build machine, and choices that affect how the JDK is built. 628 629The configuration is created by the `configure` script. The basic invocation of 630the `configure` script looks like this: 631 632``` 633bash configure [options] 634``` 635 636This will create an output directory containing the configuration and setup an 637area for the build result. This directory typically looks like 638`build/linux-x64-server-release`, but the actual name depends on your specific 639configuration. (It can also be set directly, see [Using Multiple 640Configurations](#using-multiple-configurations)). This directory is referred to 641as `$BUILD` in this documentation. 642 643`configure` will try to figure out what system you are running on and where all 644necessary build components are. If you have all prerequisites for building 645installed, it should find everything. If it fails to detect any component 646automatically, it will exit and inform you about the problem. 647 648Some command line examples: 649 650 * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`: 651 ``` 652 bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32 653 ``` 654 655 * Create a debug build with the `server` JVM and DTrace enabled: 656 ``` 657 bash configure --enable-debug --with-jvm-variants=server --enable-dtrace 658 ``` 659 660### Common Configure Arguments 661 662Here follows some of the most common and important `configure` argument. 663 664To get up-to-date information on *all* available `configure` argument, please 665run: 666``` 667bash configure --help 668``` 669 670(Note that this help text also include general autoconf options, like 671`--dvidir`, that is not relevant to the JDK. To list only JDK-specific 672features, use `bash configure --help=short` instead.) 673 674#### Configure Arguments for Tailoring the Build 675 676 * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand 677 for `--with-debug-level=fastdebug`) 678 * `--with-debug-level=<level>` - Set the debug level, which can be `release`, 679 `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized` 680 is variant of `release` with additional Hotspot debug code. 681 * `--with-native-debug-symbols=<method>` - Specify if and how native debug 682 symbols should be built. Available methods are `none`, `internal`, 683 `external`, `zipped`. Default behavior depends on platform. See [Native 684 Debug Symbols](#native-debug-symbols) for more details. 685 * `--with-version-string=<string>` - Specify the version string this build 686 will be identified with. 687 * `--with-version-<part>=<value>` - A group of options, where `<part>` can be 688 any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use 689 these options to modify just the corresponding part of the version string 690 from the default, or the value provided by `--with-version-string`. 691 * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant 692 (or variants) of Hotspot. Valid variants are: `server`, `client`, 693 `minimal`, `core`, `zero`, `custom`. Note that not all 694 variants are possible to combine in a single build. 695 * `--with-jvm-features=<feature>[,<feature>...]` - Use the specified JVM 696 features when building Hotspot. The list of features will be enabled on top 697 of the default list. For the `custom` JVM variant, this default list is 698 empty. A complete list of available JVM features can be found using `bash 699 configure --help`. 700 * `--with-target-bits=<bits>` - Create a target binary suitable for running 701 on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build 702 platform, instead of doing a full cross-compile. (This is known as a 703 *reduced* build.) 704 705On Linux, BSD and AIX, it is possible to override where Java by default 706searches for runtime/JNI libraries. This can be useful in situations where 707there is a special shared directory for system JNI libraries. This setting 708can in turn be overriden at runtime by setting the `java.library.path` property. 709 710 * `--with-jni-libpath=<path>` - Use the specified path as a default 711 when searching for runtime libraries. 712 713#### Configure Arguments for Native Compilation 714 715 * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources 716 * `--with-sysroot=<path>` - Use this directory as sysroot 717 * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the 718 default path when searching for all kinds of binaries 719 * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when 720 searching for toolchain binaries (compilers etc) 721 * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C 722 files 723 * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++ 724 files 725 * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK 726 libraries 727 728#### Configure Arguments for External Dependencies 729 730 * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK]( 731 #boot-jdk-requirements) 732 * `--with-freetype=<path>` - Set the path to [FreeType](#freetype) 733 * `--with-cups=<path>` - Set the path to [CUPS](#cups) 734 * `--with-x=<path>` - Set the path to [X11](#x11) 735 * `--with-alsa=<path>` - Set the path to [ALSA](#alsa) 736 * `--with-libffi=<path>` - Set the path to [libffi](#libffi) 737 * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests]( 738 #running-tests) 739 740Certain third-party libraries used by the JDK (libjpeg, giflib, libpng, lcms 741and zlib) are included in the JDK repository. The default behavior of the 742JDK build is to use the included ("bundled") versions of libjpeg, giflib, 743libpng and lcms. 744For zlib, the system lib (if present) is used except on Windows and AIX. 745However the bundled libraries may be replaced by an external version. 746To do so, specify `system` as the `<source>` option in these arguments. 747(The default is `bundled`). 748 749 * `--with-libjpeg=<source>` - Use the specified source for libjpeg 750 * `--with-giflib=<source>` - Use the specified source for giflib 751 * `--with-libpng=<source>` - Use the specified source for libpng 752 * `--with-lcms=<source>` - Use the specified source for lcms 753 * `--with-zlib=<source>` - Use the specified source for zlib 754 755On Linux, it is possible to select either static or dynamic linking of the C++ 756runtime. The default is static linking, with dynamic linking as fallback if the 757static library is not found. 758 759 * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic` 760 or `default`) for linking the C++ runtime. 761 762### Configure Control Variables 763 764It is possible to control certain aspects of `configure` by overriding the 765value of `configure` variables, either on the command line or in the 766environment. 767 768Normally, this is **not recommended**. If used improperly, it can lead to a 769broken configuration. Unless you're well versed in the build system, this is 770hard to use properly. Therefore, `configure` will print a warning if this is 771detected. 772 773However, there are a few `configure` variables, known as *control variables* 774that are supposed to be overriden on the command line. These are variables that 775describe the location of tools needed by the build, like `MAKE` or `GREP`. If 776any such variable is specified, `configure` will use that value instead of 777trying to autodetect the tool. For instance, `bash configure 778MAKE=/opt/gnumake4.0/bin/make`. 779 780If a configure argument exists, use that instead, e.g. use `--with-jtreg` 781instead of setting `JTREGEXE`. 782 783Also note that, despite what autoconf claims, setting `CFLAGS` will not 784accomplish anything. Instead use `--with-extra-cflags` (and similar for 785`cxxflags` and `ldflags`). 786 787## Running Make 788 789When you have a proper configuration, all you need to do to build the JDK is to 790run `make`. (But see the warning at [GNU Make](#gnu-make) about running the 791correct version of make.) 792 793When running `make` without any arguments, the default target is used, which is 794the same as running `make default` or `make jdk`. This will build a minimal (or 795roughly minimal) set of compiled output (known as an "exploded image") needed 796for a developer to actually execute the newly built JDK. The idea is that in an 797incremental development fashion, when doing a normal make, you should only 798spend time recompiling what's changed (making it purely incremental) and only 799do the work that's needed to actually run and test your code. 800 801The output of the exploded image resides in `$BUILD/jdk`. You can test the 802newly built JDK like this: `$BUILD/jdk/bin/java -version`. 803 804### Common Make Targets 805 806Apart from the default target, here are some common make targets: 807 808 * `hotspot` - Build all of hotspot (but only hotspot) 809 * `hotspot-<variant>` - Build just the specified jvm variant 810 * `images` or `product-images` - Build the JDK image 811 * `docs` or `docs-image` - Build the documentation image 812 * `test-image` - Build the test image 813 * `all` or `all-images` - Build all images (product, docs and test) 814 * `bootcycle-images` - Build images twice, second time with newly built JDK 815 (good for testing) 816 * `clean` - Remove all files generated by make, but not those generated by 817 configure 818 * `dist-clean` - Remove all files, including configuration 819 820Run `make help` to get an up-to-date list of important make targets and make 821control variables. 822 823It is possible to build just a single module, a single phase, or a single phase 824of a single module, by creating make targets according to these followin 825patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`, 826`launchers`, `libs` or `rmic`. See [Using Fine-Grained Make Targets]( 827#using-fine-grained-make-targets) for more details about this functionality. 828 829 * `<phase>` - Build the specified phase and everything it depends on 830 * `<module>` - Build the specified module and everything it depends on 831 * `<module>-<phase>` - Compile the specified phase for the specified module 832 and everything it depends on 833 834Similarly, it is possible to clean just a part of the build by creating make 835targets according to these patterns: 836 837 * `clean-<outputdir>` - Remove the subdir in the output dir with the name 838 * `clean-<phase>` - Remove all build results related to a certain build 839 phase 840 * `clean-<module>` - Remove all build results related to a certain module 841 * `clean-<module>-<phase>` - Remove all build results related to a certain 842 module and phase 843 844### Make Control Variables 845 846It is possible to control `make` behavior by overriding the value of `make` 847variables, either on the command line or in the environment. 848 849Normally, this is **not recommended**. If used improperly, it can lead to a 850broken build. Unless you're well versed in the build system, this is hard to 851use properly. Therefore, `make` will print a warning if this is detected. 852 853However, there are a few `make` variables, known as *control variables* that 854are supposed to be overriden on the command line. These make up the "make time" 855configuration, as opposed to the "configure time" configuration. 856 857#### General Make Control Variables 858 859 * `JOBS` - Specify the number of jobs to build with. See [Build 860 Performance](#build-performance). 861 * `LOG` - Specify the logging level and functionality. See [Checking the 862 Build Log File](#checking-the-build-log-file) 863 * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using 864 Multiple Configurations](#using-multiple-configurations) 865 866#### Test Make Control Variables 867 868These make control variables only make sense when running tests. Please see 869[Testing the JDK](testing.html) for details. 870 871 * `TEST` 872 * `TEST_JOBS` 873 * `JTREG` 874 * `GTEST` 875 876#### Advanced Make Control Variables 877 878These advanced make control variables can be potentially unsafe. See [Hints and 879Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and 880[Understanding the Build System](#understanding-the-build-system) for details. 881 882 * `SPEC` 883 * `CONF_CHECK` 884 * `COMPARE_BUILD` 885 * `JDK_FILTER` 886 887## Running Tests 888 889Most of the JDK tests are using the [JTReg](http://openjdk.java.net/jtreg) 890test framework. Make sure that your configuration knows where to find your 891installation of JTReg. If this is not picked up automatically, use the 892`--with-jtreg=<path to jtreg home>` option to point to the JTReg framework. 893Note that this option should point to the JTReg home, i.e. the top directory, 894containing `lib/jtreg.jar` etc. 895 896The [Adoption Group](https://wiki.openjdk.java.net/display/Adoption) provides 897recent builds of jtreg [here]( 898https://adopt-openjdk.ci.cloudbees.com/job/jtreg/lastSuccessfulBuild/artifact). 899Download the latest `.tar.gz` file, unpack it, and point `--with-jtreg` to the 900`jtreg` directory that you just unpacked. 901 902To execute the most basic tests (tier 1), use: 903``` 904make run-test-tier1 905``` 906 907For more details on how to run tests, please see the [Testing 908the JDK](testing.html) document. 909 910## Cross-compiling 911 912Cross-compiling means using one platform (the *build* platform) to generate 913output that can ran on another platform (the *target* platform). 914 915The typical reason for cross-compiling is that the build is performed on a more 916powerful desktop computer, but the resulting binaries will be able to run on a 917different, typically low-performing system. Most of the complications that 918arise when building for embedded is due to this separation of *build* and 919*target* systems. 920 921This requires a more complex setup and build procedure. This section assumes 922you are familiar with cross-compiling in general, and will only deal with the 923particularities of cross-compiling the JDK. If you are new to cross-compiling, 924please see the [external links at Wikipedia]( 925https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start 926on reading materials. 927 928Cross-compiling the JDK requires you to be able to build both for the build 929platform and for the target platform. The reason for the former is that we need 930to build and execute tools during the build process, both native tools and Java 931tools. 932 933If all you want to do is to compile a 32-bit version, for the same OS, on a 93464-bit machine, consider using `--with-target-bits=32` instead of doing a 935full-blown cross-compilation. (While this surely is possible, it's a lot more 936work and will take much longer to build.) 937 938### Cross compiling the easy way with OpenJDK devkits 939 940The OpenJDK build system provides out-of-the box support for creating and using 941so called devkits. A `devkit` is basically a collection of a cross-compiling 942toolchain and a sysroot environment which can easily be used together with the 943`--with-devkit` configure option to cross compile the OpenJDK. On Linux/x86_64, 944the following command: 945``` 946bash configure --with-devkit=<devkit-path> --openjdk-target=ppc64-linux-gnu && make 947``` 948 949will configure and build OpenJDK for Linux/ppc64 assuming that `<devkit-path>` 950points to a Linux/x86_64 to Linux/ppc64 devkit. 951 952Devkits can be created from the `make/devkit` directory by executing: 953``` 954make [ TARGETS="<TARGET_TRIPLET>+" ] [ BASE_OS=<OS> ] [ BASE_OS_VERSION=<VER> ] 955``` 956 957where `TARGETS` contains one or more `TARGET_TRIPLET`s of the form 958described in [section 3.4 of the GNU Autobook]( 959https://sourceware.org/autobook/autobook/autobook_17.html). If no 960targets are given, a native toolchain for the current platform will be 961created. Currently, at least the following targets are known to work: 962 963 Supported devkit targets 964 ------------------------- 965 x86_64-linux-gnu 966 aarch64-linux-gnu 967 arm-linux-gnueabihf 968 ppc64-linux-gnu 969 ppc64le-linux-gnu 970 s390x-linux-gnu 971 972`BASE_OS` must be one of "OEL6" for Oracle Enterprise Linux 6 or 973"Fedora" (if not specified "OEL6" will be the default). If the base OS 974is "Fedora" the corresponding Fedora release can be specified with the 975help of the `BASE_OS_VERSION` option (with "27" as default version). 976If the build is successful, the new devkits can be found in the 977`build/devkit/result` subdirectory: 978``` 979cd make/devkit 980make TARGETS="ppc64le-linux-gnu aarch64-linux-gnu" BASE_OS=Fedora BASE_OS_VERSION=21 981ls -1 ../../build/devkit/result/ 982x86_64-linux-gnu-to-aarch64-linux-gnu 983x86_64-linux-gnu-to-ppc64le-linux-gnu 984``` 985 986Notice that devkits are not only useful for targeting different build 987platforms. Because they contain the full build dependencies for a 988system (i.e. compiler and root file system), they can easily be used 989to build well-known, reliable and reproducible build environments. You 990can for example create and use a devkit with GCC 7.3 and a Fedora 12 991sysroot environment (with glibc 2.11) on Ubuntu 14.04 (which doesn't 992have GCC 7.3 by default) to produce OpenJDK binaries which will run on 993all Linux systems with runtime libraries newer than the ones from 994Fedora 12 (e.g. Ubuntu 16.04, SLES 11 or RHEL 6). 995 996### Boot JDK and Build JDK 997 998When cross-compiling, make sure you use a boot JDK that runs on the *build* 999system, and not on the *target* system. 1000 1001To be able to build, we need a "Build JDK", which is a JDK built from the 1002current sources (that is, the same as the end result of the entire build 1003process), but able to run on the *build* system, and not the *target* system. 1004(In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when 1005building JDK 9.) 1006 1007The build process will create a minimal Build JDK for you, as part of building. 1008To speed up the build, you can use `--with-build-jdk` to `configure` to point 1009to a pre-built Build JDK. Please note that the build result is unpredictable, 1010and can possibly break in subtle ways, if the Build JDK does not **exactly** 1011match the current sources. 1012 1013### Specifying the Target Platform 1014 1015You *must* specify the target platform when cross-compiling. Doing so will also 1016automatically turn the build into a cross-compiling mode. The simplest way to 1017do this is to use the `--openjdk-target` argument, e.g. 1018`--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`. 1019This will automatically set the `--build`, `--host` and `--target` options for 1020autoconf, which can otherwise be confusing. (In autoconf terminology, the 1021"target" is known as "host", and "target" is used for building a Canadian 1022cross-compiler.) 1023 1024### Toolchain Considerations 1025 1026You will need two copies of your toolchain, one which generates output that can 1027run on the target system (the normal, or *target*, toolchain), and one that 1028generates output that can run on the build system (the *build* toolchain). Note 1029that cross-compiling is only supported for gcc at the time being. The gcc 1030standard is to prefix cross-compiling toolchains with the target denominator. 1031If you follow this standard, `configure` is likely to pick up the toolchain 1032correctly. 1033 1034The *build* toolchain will be autodetected just the same way the normal 1035*build*/*target* toolchain will be autodetected when not cross-compiling. If 1036this is not what you want, or if the autodetection fails, you can specify a 1037devkit containing the *build* toolchain using `--with-build-devkit` to 1038`configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments. 1039 1040It is often helpful to locate the cross-compilation tools, headers and 1041libraries in a separate directory, outside the normal path, and point out that 1042directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and 1043appending the directory when searching for cross-compilations tools 1044(`--with-toolchain-path`). As a compact form, you can also use `--with-devkit` 1045to point to a single directory, if it is correctly setup. (See `basics.m4` for 1046details.) 1047 1048If you are unsure what toolchain and versions to use, these have been proved 1049working at the time of writing: 1050 1051 * [aarch64]( 1052https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-linux-gnu-4.8-2013.11_linux.tar.xz) 1053 * [arm 32-bit hardware floating point]( 1054https://launchpad.net/linaro-toolchain-unsupported/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux.tar.bz2) 1055 1056### Native Libraries 1057 1058You will need copies of external native libraries for the *target* system, 1059present on the *build* machine while building. 1060 1061Take care not to replace the *build* system's version of these libraries by 1062mistake, since that can render the *build* machine unusable. 1063 1064Make sure that the libraries you point to (ALSA, X11, etc) are for the 1065*target*, not the *build*, platform. 1066 1067#### ALSA 1068 1069You will need alsa libraries suitable for your *target* system. For most cases, 1070using Debian's pre-built libraries work fine. 1071 1072Note that alsa is needed even if you only want to build a headless JDK. 1073 1074 * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and 1075 search for the `libasound2` and `libasound2-dev` packages for your *target* 1076 system. Download them to /tmp. 1077 1078 * Install the libraries into the cross-compilation toolchain. For instance: 1079``` 1080cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc 1081dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb . 1082dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb . 1083``` 1084 1085 * If alsa is not properly detected by `configure`, you can point it out by 1086 `--with-alsa`. 1087 1088#### X11 1089 1090You will need X11 libraries suitable for your *target* system. For most cases, 1091using Debian's pre-built libraries work fine. 1092 1093Note that X11 is needed even if you only want to build a headless JDK. 1094 1095 * Go to [Debian Package Search](https://www.debian.org/distrib/packages), 1096 search for the following packages for your *target* system, and download them 1097 to /tmp/target-x11: 1098 * libxi 1099 * libxi-dev 1100 * x11proto-core-dev 1101 * x11proto-input-dev 1102 * x11proto-kb-dev 1103 * x11proto-render-dev 1104 * x11proto-xext-dev 1105 * libice-dev 1106 * libxrender 1107 * libxrender-dev 1108 * libxrandr-dev 1109 * libsm-dev 1110 * libxt-dev 1111 * libx11 1112 * libx11-dev 1113 * libxtst 1114 * libxtst-dev 1115 * libxext 1116 * libxext-dev 1117 1118 * Install the libraries into the cross-compilation toolchain. For instance: 1119 ``` 1120 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr 1121 mkdir X11R6 1122 cd X11R6 1123 for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done 1124 mv usr/* . 1125 cd lib 1126 cp arm-linux-gnueabihf/* . 1127 ``` 1128 1129 You can ignore the following messages. These libraries are not needed to 1130 successfully complete a full JDK build. 1131 ``` 1132 cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory 1133 cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory 1134 cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory 1135 ``` 1136 1137 * If the X11 libraries are not properly detected by `configure`, you can 1138 point them out by `--with-x`. 1139 1140### Creating And Using Sysroots With qemu-deboostrap 1141 1142Fortunately, you can create sysroots for foreign architectures with tools 1143provided by your OS. On Debian/Ubuntu systems, one could use `qemu-deboostrap` to 1144create the *target* system chroot, which would have the native libraries and headers 1145specific to that *target* system. After that, we can use the cross-compiler on the *build* 1146system, pointing into chroot to get the build dependencies right. This allows building 1147for foreign architectures with native compilation speed. 1148 1149For example, cross-compiling to AArch64 from x86_64 could be done like this: 1150 1151 * Install cross-compiler on the *build* system: 1152``` 1153apt install g++-aarch64-linux-gnu gcc-aarch64-linux-gnu 1154``` 1155 1156 * Create chroot on the *build* system, configuring it for *target* system: 1157``` 1158sudo qemu-debootstrap --arch=arm64 --verbose \ 1159 --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 \ 1160 --resolve-deps jessie /chroots/arm64 http://httpredir.debian.org/debian/ 1161``` 1162 1163 * Configure and build with newly created chroot as sysroot/toolchain-path: 1164``` 1165CC=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/ 1166make images 1167ls build/linux-aarch64-normal-server-release/ 1168``` 1169 1170The build does not create new files in that chroot, so it can be reused for multiple builds 1171without additional cleanup. 1172 1173Architectures that are known to successfully cross-compile like this are: 1174 1175 Target `CC` `CXX` `--arch=...` `--openjdk-target=...` 1176 ------------ ------------------------- --------------------------- ------------- ----------------------- 1177 x86 default default i386 i386-linux-gnu 1178 armhf gcc-arm-linux-gnueabihf g++-arm-linux-gnueabihf armhf arm-linux-gnueabihf 1179 aarch64 gcc-aarch64-linux-gnu g++-aarch64-linux-gnu arm64 aarch64-linux-gnu 1180 ppc64el gcc-powerpc64le-linux-gnu g++-powerpc64le-linux-gnu ppc64el powerpc64le-linux-gnu 1181 s390x gcc-s390x-linux-gnu g++-s390x-linux-gnu s390x s390x-linux-gnu 1182 1183Additional architectures might be supported by Debian/Ubuntu Ports. 1184 1185### Building for ARM/aarch64 1186 1187A common cross-compilation target is the ARM CPU. When building for ARM, it is 1188useful to set the ABI profile. A number of pre-defined ABI profiles are 1189available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt, 1190armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer 1191properly supported by the JDK. 1192 1193### Verifying the Build 1194 1195The build will end up in a directory named like 1196`build/linux-arm-normal-server-release`. 1197 1198Inside this build output directory, the `images/jdk` will contain the newly 1199built JDK, for your *target* system. 1200 1201Copy these folders to your *target* system. Then you can run e.g. 1202`images/jdk/bin/java -version`. 1203 1204## Build Performance 1205 1206Building the JDK requires a lot of horsepower. Some of the build tools can be 1207adjusted to utilize more or less of resources such as parallel threads and 1208memory. The `configure` script analyzes your system and selects reasonable 1209values for such options based on your hardware. If you encounter resource 1210problems, such as out of memory conditions, you can modify the detected values 1211with: 1212 1213 * `--with-num-cores` -- number of cores in the build system, e.g. 1214 `--with-num-cores=8`. 1215 1216 * `--with-memory-size` -- memory (in MB) available in the build system, e.g. 1217 `--with-memory-size=1024` 1218 1219You can also specify directly the number of build jobs to use with 1220`--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag 1221to `make`. In most cases it will be ignored by the makefiles, but it can cause 1222problems for some make targets. 1223 1224It might also be necessary to specify the JVM arguments passed to the Boot JDK, 1225using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the 1226default JVM arguments passed to the Boot JDK. 1227 1228At the end of a successful execution of `configure`, you will get a performance 1229summary, indicating how well the build will perform. Here you will also get 1230performance hints. If you want to build fast, pay attention to those! 1231 1232If you want to tweak build performance, run with `make LOG=info` to get a build 1233time summary at the end of the build process. 1234 1235### Disk Speed 1236 1237If you are using network shares, e.g. via NFS, for your source code, make sure 1238the build directory is situated on local disk (e.g. by `ln -s 1239/localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely 1240high for building on a network share; close to unusable. 1241 1242Also, make sure that your build tools (including Boot JDK and toolchain) is 1243located on a local disk and not a network share. 1244 1245As has been stressed elsewhere, do use SSD for source code and build directory, 1246as well as (if possible) the build tools. 1247 1248### Virus Checking 1249 1250The use of virus checking software, especially on Windows, can *significantly* 1251slow down building of the JDK. If possible, turn off such software, or exclude 1252the directory containing the JDK source code from on-the-fly checking. 1253 1254### Ccache 1255 1256The JDK build supports building with ccache when using gcc or clang. Using 1257ccache can radically speed up compilation of native code if you often rebuild 1258the same sources. Your milage may vary however, so we recommend evaluating it 1259for yourself. To enable it, make sure it's on the path and configure with 1260`--enable-ccache`. 1261 1262### Precompiled Headers 1263 1264By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains 1265were it is properly supported (clang, gcc, and Visual Studio). Normally, this 1266speeds up the build process, but in some circumstances, it can actually slow 1267things down. 1268 1269You can experiment by disabling precompiled headers using 1270`--disable-precompiled-headers`. 1271 1272### Icecc / icecream 1273 1274[icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a 1275distributed compiler network. If you have multiple machines available for 1276building the JDK, you can drastically cut individual build times by utilizing 1277it. 1278 1279To use, setup an icecc network, and install icecc on the build machine. Then 1280run `configure` using `--enable-icecc`. 1281 1282### Using sjavac 1283 1284To speed up Java compilation, especially incremental compilations, you can try 1285the experimental sjavac compiler by using `--enable-sjavac`. 1286 1287### Building the Right Target 1288 1289Selecting the proper target to build can have dramatic impact on build time. 1290For normal usage, `jdk` or the default target is just fine. You only need to 1291build `images` for shipping, or if your tests require it. 1292 1293See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on 1294how to build an even smaller subset of the product. 1295 1296## Troubleshooting 1297 1298If your build fails, it can sometimes be difficult to pinpoint the problem or 1299find a proper solution. 1300 1301### Locating the Source of the Error 1302 1303When a build fails, it can be hard to pinpoint the actual cause of the error. 1304In a typical build process, different parts of the product build in parallel, 1305with the output interlaced. 1306 1307#### Build Failure Summary 1308 1309To help you, the build system will print a failure summary at the end. It looks 1310like this: 1311 1312``` 1313ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2) 1314 1315=== Output from failing command(s) repeated here === 1316* For target hotspot_variant-server_libjvm_objs_psMemoryPool.o: 1317/localhome/git/jdk-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type 1318 ... (rest of output omitted) 1319 1320* All command lines available in /localhome/git/jdk-sandbox/build/linux-x64/make-support/failure-logs. 1321=== End of repeated output === 1322 1323=== Make failed targets repeated here === 1324lib/CompileJvm.gmk:207: recipe for target '/localhome/git/jdk-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed 1325make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed 1326=== End of repeated output === 1327 1328Hint: Try searching the build log for the name of the first failed target. 1329Hint: If caused by a warning, try configure --disable-warnings-as-errors. 1330``` 1331 1332Let's break it down! First, the selected configuration, and the top-level 1333target you entered on the command line that caused the failure is printed. 1334 1335Then, between the `Output from failing command(s) repeated here` and `End of 1336repeated output` the first lines of output (stdout and stderr) from the actual 1337failing command is repeated. In most cases, this is the error message that 1338caused the build to fail. If multiple commands were failing (this can happen in 1339a parallel build), output from all failed commands will be printed here. 1340 1341The path to the `failure-logs` directory is printed. In this file you will find 1342a `<target>.log` file that contains the output from this command in its 1343entirety, and also a `<target>.cmd`, which contain the complete command line 1344used for running this command. You can re-run the failing command by executing 1345`. <path to failure-logs>/<target>.cmd` in your shell. 1346 1347Another way to trace the failure is to follow the chain of make targets, from 1348top-level targets to individual file targets. Between `Make failed targets 1349repeated here` and `End of repeated output` the output from make showing this 1350chain is repeated. The first failed recipe will typically contain the full path 1351to the file in question that failed to compile. Following lines will show a 1352trace of make targets why we ended up trying to compile that file. 1353 1354Finally, some hints are given on how to locate the error in the complete log. 1355In this example, we would try searching the log file for "`psMemoryPool.o`". 1356Another way to quickly locate make errors in the log is to search for "`] 1357Error`" or "`***`". 1358 1359Note that the build failure summary will only help you if the issue was a 1360compilation failure or similar. If the problem is more esoteric, or is due to 1361errors in the build machinery, you will likely get empty output logs, and `No 1362indication of failed target found` instead of the make target chain. 1363 1364#### Checking the Build Log File 1365 1366The output (stdout and stderr) from the latest build is always stored in 1367`$BUILD/build.log`. The previous build log is stored as `build.log.old`. This 1368means that it is not necessary to redirect the build output yourself if you 1369want to process it. 1370 1371You can increase the verbosity of the log file, by the `LOG` control variable 1372to `make`. If you want to see the command lines used in compilations, use 1373`LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug` 1374or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g. 1375`LOG=info,cmdlines`. The `debug` log level will show most shell commands 1376executed by make, and `trace` will show all. Beware that both these log levels 1377will produce a massive build log! 1378 1379### Fixing Unexpected Build Failures 1380 1381Most of the time, the build will fail due to incorrect changes in the source 1382code. 1383 1384Sometimes the build can fail with no apparent changes that have caused the 1385failure. If this is the first time you are building the JDK on this particular 1386computer, and the build fails, the problem is likely with your build 1387environment. But even if you have previously built the JDK with success, and it 1388now fails, your build environment might have changed (perhaps due to OS 1389upgrades or similar). But most likely, such failures are due to problems with 1390the incremental rebuild. 1391 1392#### Problems with the Build Environment 1393 1394Make sure your configuration is correct. Re-run `configure`, and look for any 1395warnings. Warnings that appear in the middle of the `configure` output is also 1396repeated at the end, after the summary. The entire log is stored in 1397`$BUILD/configure.log`. 1398 1399Verify that the summary at the end looks correct. Are you indeed using the Boot 1400JDK and native toolchain that you expect? 1401 1402By default, the JDK has a strict approach where warnings from the compiler is 1403considered errors which fail the build. For very new or very old compiler 1404versions, this can trigger new classes of warnings, which thus fails the build. 1405Run `configure` with `--disable-warnings-as-errors` to turn of this behavior. 1406(The warnings will still show, but not make the build fail.) 1407 1408#### Problems with Incremental Rebuilds 1409 1410Incremental rebuilds mean that when you modify part of the product, only the 1411affected parts get rebuilt. While this works great in most cases, and 1412significantly speed up the development process, from time to time complex 1413interdependencies will result in an incorrect build result. This is the most 1414common cause for unexpected build problems. 1415 1416Here are a suggested list of things to try if you are having unexpected build 1417problems. Each step requires more time than the one before, so try them in 1418order. Most issues will be solved at step 1 or 2. 1419 1420 1. Make sure your repository is up-to-date 1421 1422 Run `git pull origin master` to make sure you have the latest changes. 1423 1424 2. Clean build results 1425 1426 The simplest way to fix incremental rebuild issues is to run `make clean`. 1427 This will remove all build results, but not the configuration or any build 1428 system support artifacts. In most cases, this will solve build errors 1429 resulting from incremental build mismatches. 1430 1431 3. Completely clean the build directory. 1432 1433 If this does not work, the next step is to run `make dist-clean`, or 1434 removing the build output directory (`$BUILD`). This will clean all 1435 generated output, including your configuration. You will need to re-run 1436 `configure` after this step. A good idea is to run `make 1437 print-configuration` before running `make dist-clean`, as this will print 1438 your current `configure` command line. Here's a way to do this: 1439 1440 ``` 1441 make print-configuration > current-configuration 1442 make dist-clean 1443 bash configure $(cat current-configuration) 1444 make 1445 ``` 1446 1447 4. Re-clone the Git repository 1448 1449 Sometimes the Git repository gets in a state that causes the product 1450 to be un-buildable. In such a case, the simplest solution is often the 1451 "sledgehammer approach": delete the entire repository, and re-clone it. 1452 If you have local changes, save them first to a different location using 1453 `git format-patch`. 1454 1455### Specific Build Issues 1456 1457#### Clock Skew 1458 1459If you get an error message like this: 1460``` 1461File 'xxx' has modification time in the future. 1462Clock skew detected. Your build may be incomplete. 1463``` 1464then the clock on your build machine is out of sync with the timestamps on the 1465source files. Other errors, apparently unrelated but in fact caused by the 1466clock skew, can occur along with the clock skew warnings. These secondary 1467errors may tend to obscure the fact that the true root cause of the problem is 1468an out-of-sync clock. 1469 1470If you see these warnings, reset the clock on the build machine, run `make 1471clean` and restart the build. 1472 1473#### Out of Memory Errors 1474 1475On Solaris, you might get an error message like this: 1476``` 1477Trouble writing out table to disk 1478``` 1479To solve this, increase the amount of swap space on your build machine. 1480 1481On Windows, you might get error messages like this: 1482``` 1483fatal error - couldn't allocate heap 1484cannot create ... Permission denied 1485spawn failed 1486``` 1487This can be a sign of a Cygwin problem. See the information about solving 1488problems in the [Cygwin](#cygwin) section. Rebooting the computer might help 1489temporarily. 1490 1491### Getting Help 1492 1493If none of the suggestions in this document helps you, or if you find what you 1494believe is a bug in the build system, please contact the Build Group by sending 1495a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net). 1496Please include the relevant parts of the configure and/or build log. 1497 1498If you need general help or advice about developing for the JDK, you can also 1499contact the Adoption Group. See the section on [Contributing to OpenJDK]( 1500#contributing-to-openjdk) for more information. 1501 1502## Hints and Suggestions for Advanced Users 1503 1504### Bash Completion 1505 1506The `configure` and `make` commands tries to play nice with bash command-line 1507completion (using `<tab>` or `<tab><tab>`). To use this functionality, make 1508sure you enable completion in your `~/.bashrc` (see instructions for bash in 1509your operating system). 1510 1511Make completion will work out of the box, and will complete valid make targets. 1512For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`. 1513 1514The `configure` script can get completion for options, but for this to work you 1515need to help `bash` on the way. The standard way of running the script, `bash 1516configure`, will not be understood by bash completion. You need `configure` to 1517be the command to run. One way to achieve this is to add a simple helper script 1518to your path: 1519 1520``` 1521cat << EOT > /tmp/configure 1522#!/bin/bash 1523if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then 1524 echo >&2 "Abort: Trying to call configure helper recursively" 1525 exit 1 1526fi 1527 1528bash \$PWD/configure "\$@" 1529EOT 1530chmod +x /tmp/configure 1531sudo mv /tmp/configure /usr/local/bin 1532``` 1533 1534Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`. 1535 1536### Using Multiple Configurations 1537 1538You can have multiple configurations for a single source repository. When you 1539create a new configuration, run `configure --with-conf-name=<name>` to create a 1540configuration with the name `<name>`. Alternatively, you can create a directory 1541under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd 1542build/<name> && bash ../../configure`. 1543 1544Then you can build that configuration using `make CONF_NAME=<name>` or `make 1545CONF=<pattern>`, where `<pattern>` is a substring matching one or several 1546configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will 1547match *all* available configuration, so `make CONF= hotspot` will build the 1548`hotspot` target for all configurations. Alternatively, you can execute `make` 1549in the configuration directory, e.g. `cd build/<name> && make`. 1550 1551### Handling Reconfigurations 1552 1553If you update the repository and part of the configure script has changed, the 1554build system will force you to re-run `configure`. 1555 1556Most of the time, you will be fine by running `configure` again with the same 1557arguments as the last time, which can easily be performed by `make 1558reconfigure`. To simplify this, you can use the `CONF_CHECK` make control 1559variable, either as `make CONF_CHECK=auto`, or by setting an environment 1560variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc` 1561file, `make` will always run `reconfigure` automatically whenever the configure 1562script has changed. 1563 1564You can also use `CONF_CHECK=ignore` to skip the check for a needed configure 1565update. This might speed up the build, but comes at the risk of an incorrect 1566build result. This is only recommended if you know what you're doing. 1567 1568From time to time, you will also need to modify the command line to `configure` 1569due to changes. Use `make print-configure` to show the command line used for 1570your current configuration. 1571 1572### Using Fine-Grained Make Targets 1573 1574The default behavior for make is to create consistent and correct output, at 1575the expense of build speed, if necessary. 1576 1577If you are prepared to take some risk of an incorrect build, and know enough of 1578the system to understand how things build and interact, you can speed up the 1579build process considerably by instructing make to only build a portion of the 1580product. 1581 1582#### Building Individual Modules 1583 1584The safe way to use fine-grained make targets is to use the module specific 1585make targets. All source code in the JDK is organized so it belongs to a 1586module, e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific 1587module, by giving it as make target: `make jdk.jdwp.agent`. If the specified 1588module depends on other modules (e.g. `java.base`), those modules will be built 1589first. 1590 1591You can also specify a set of modules, just as you can always specify a set of 1592make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi 1593jdk.crypto.ucrypto` 1594 1595#### Building Individual Module Phases 1596 1597The build process for each module is divided into separate phases. Not all 1598modules need all phases. Which are needed depends on what kind of source code 1599and other artifact the module consists of. The phases are: 1600 1601 * `gensrc` (Generate source code to compile) 1602 * `gendata` (Generate non-source code artifacts) 1603 * `copy` (Copy resource artifacts) 1604 * `java` (Compile Java code) 1605 * `launchers` (Compile native executables) 1606 * `libs` (Compile native libraries) 1607 * `rmic` (Run the `rmic` tool) 1608 1609You can build only a single phase for a module by using the notation 1610`$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`, 1611use `make java.base-gensrc`. 1612 1613Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if 1614present). Make will build all needed prerequisites before building the 1615requested phase. 1616 1617#### Skipping the Dependency Check 1618 1619When using an iterative development style with frequent quick rebuilds, the 1620dependency check made by make can take up a significant portion of the time 1621spent on the rebuild. In such cases, it can be useful to bypass the dependency 1622check in make. 1623 1624> **Note that if used incorrectly, this can lead to a broken build!** 1625 1626To achieve this, append `-only` to the build target. For instance, `make 1627jdk.jdwp.agent-java-only` will *only* build the `java` phase of the 1628`jdk.jdwp.agent` module. If the required dependencies are not present, the 1629build can fail. On the other hand, the execution time measures in milliseconds. 1630 1631A useful pattern is to build the first time normally (e.g. `make 1632jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target. 1633 1634#### Rebuilding Part of java.base (JDK\_FILTER) 1635 1636If you are modifying files in `java.base`, which is the by far largest module 1637in the JDK, then you need to rebuild all those files whenever a single file has 1638changed. (This inefficiency will hopefully be addressed in JDK 10.) 1639 1640As a hack, you can use the make control variable `JDK_FILTER` to specify a 1641pattern that will be used to limit the set of files being recompiled. For 1642instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods, 1643`make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation 1644to files in the `javax.crypto` package. 1645 1646## Understanding the Build System 1647 1648This section will give you a more technical description on the details of the 1649build system. 1650 1651### Configurations 1652 1653The build system expects to find one or more configuration. These are 1654technically defined by the `spec.gmk` in a subdirectory to the `build` 1655subdirectory. The `spec.gmk` file is generated by `configure`, and contains in 1656principle the configuration (directly or by files included by `spec.gmk`). 1657 1658You can, in fact, select a configuration to build by pointing to the `spec.gmk` 1659file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`. 1660While this is not the recommended way to call `make` as a user, it is what is 1661used under the hood by the build system. 1662 1663### Build Output Structure 1664 1665The build output for a configuration will end up in `build/<configuration 1666name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory 1667contains the following important directories: 1668 1669``` 1670buildtools/ 1671configure-support/ 1672hotspot/ 1673images/ 1674jdk/ 1675make-support/ 1676support/ 1677test-results/ 1678test-support/ 1679``` 1680 1681This is what they are used for: 1682 1683 * `images`: This is the directory were the output of the `*-image` make 1684 targets end up. For instance, `make jdk-image` ends up in `images/jdk`. 1685 1686 * `jdk`: This is the "exploded image". After `make jdk`, you will be able to 1687 launch the newly built JDK by running `$BUILD/jdk/bin/java`. 1688 1689 * `test-results`: This directory contains the results from running tests. 1690 1691 * `support`: This is an area for intermediate files needed during the build, 1692 e.g. generated source code, object files and class files. Some noteworthy 1693 directories in `support` is `gensrc`, which contains the generated source 1694 code, and the `modules_*` directories, which contains the files in a 1695 per-module hierarchy that will later be collapsed into the `jdk` directory 1696 of the exploded image. 1697 1698 * `buildtools`: This is an area for tools compiled for the build platform 1699 that are used during the rest of the build. 1700 1701 * `hotspot`: This is an area for intermediate files needed when building 1702 hotspot. 1703 1704 * `configure-support`, `make-support` and `test-support`: These directories 1705 contain files that are needed by the build system for `configure`, `make` 1706 and for running tests. 1707 1708### Fixpath 1709 1710Windows path typically look like `C:\User\foo`, while Unix paths look like 1711`/home/foo`. Tools with roots from Unix often experience issues related to this 1712mismatch when running on Windows. 1713 1714In the JDK build, we always use Unix paths internally, and only just before 1715calling a tool that does not understand Unix paths do we convert them to 1716Windows paths. 1717 1718This conversion is done by the `fixpath` tool, which is a small wrapper that 1719modifies unix-style paths to Windows-style paths in command lines. Fixpath is 1720compiled automatically by `configure`. 1721 1722### Native Debug Symbols 1723 1724Native libraries and executables can have debug symbol (and other debug 1725information) associated with them. How this works is very much platform 1726dependent, but a common problem is that debug symbol information takes a lot of 1727disk space, but is rarely needed by the end user. 1728 1729The JDK supports different methods on how to handle debug symbols. The 1730method used is selected by `--with-native-debug-symbols`, and available methods 1731are `none`, `internal`, `external`, `zipped`. 1732 1733 * `none` means that no debug symbols will be generated during the build. 1734 1735 * `internal` means that debug symbols will be generated during the build, and 1736 they will be stored in the generated binary. 1737 1738 * `external` means that debug symbols will be generated during the build, and 1739 after the compilation, they will be moved into a separate `.debuginfo` file. 1740 (This was previously known as FDS, Full Debug Symbols). 1741 1742 * `zipped` is like `external`, but the .debuginfo file will also be zipped 1743 into a `.diz` file. 1744 1745When building for distribution, `zipped` is a good solution. Binaries built 1746with `internal` is suitable for use by developers, since they facilitate 1747debugging, but should be stripped before distributed to end users. 1748 1749### Autoconf Details 1750 1751The `configure` script is based on the autoconf framework, but in some details 1752deviate from a normal autoconf `configure` script. 1753 1754The `configure` script in the top level directory of the JDK is just a thin 1755wrapper that calls `make/autoconf/configure`. This in turn will run `autoconf` 1756to create the runnable (generated) configure script, as 1757`.build/generated-configure.sh`. Apart from being responsible for the 1758generation of the runnable script, the `configure` script also provides 1759functionality that is not easily expressed in the normal Autoconf framework. As 1760part of this functionality, the generated script is called. 1761 1762The build system will detect if the Autoconf source files have changed, and 1763will trigger a regeneration of the generated script if needed. You can also 1764manually request such an update by `bash configure autogen`. 1765 1766In previous versions of the JDK, the generated script was checked in at 1767`make/autoconf/generated-configure.sh`. This is no longer the case. 1768 1769### Developing the Build System Itself 1770 1771This section contains a few remarks about how to develop for the build system 1772itself. It is not relevant if you are only making changes in the product source 1773code. 1774 1775While technically using `make`, the make source files of the JDK does not 1776resemble most other Makefiles. Instead of listing specific targets and actions 1777(perhaps using patterns), the basic modus operandi is to call a high-level 1778function (or properly, macro) from the API in `make/common`. For instance, to 1779compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module, 1780a call like this would be made: 1781 1782``` 1783$(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \ 1784 SETUP := GENERATE_OLDBYTECODE, \ 1785 SRC := $(TOPDIR)/src/jkd.foo/share/classes, \ 1786 INCLUDES := jdk/internal/foo, \ 1787 BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \ 1788)) 1789``` 1790 1791By encapsulating and expressing the high-level knowledge of *what* should be 1792done, rather than *how* it should be done (as is normal in Makefiles), we can 1793build a much more powerful and flexible build system. 1794 1795Correct dependency tracking is paramount. Sloppy dependency tracking will lead 1796to improper parallelization, or worse, race conditions. 1797 1798To test for/debug race conditions, try running `make JOBS=1` and `make 1799JOBS=100` and see if it makes any difference. (It shouldn't). 1800 1801To compare the output of two different builds and see if, and how, they differ, 1802run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two 1803builds you want to compare. 1804 1805To automatically build two consecutive versions and compare them, use 1806`COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value 1807assignments, like this: 1808``` 1809make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot 1810``` 1811See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`. 1812 1813To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`. 1814Use `JOBS=1` to avoid parallelism. 1815 1816Please check that you adhere to the [Code Conventions for the Build System]( 1817http://openjdk.java.net/groups/build/doc/code-conventions.html) before 1818submitting patches. 1819 1820## Contributing to the JDK 1821 1822So, now you've built your JDK, and made your first patch, and want to 1823contribute it back to the OpenJDK Community. 1824 1825First of all: Thank you! We gladly welcome your contribution. 1826However, please bear in mind that the JDK is a massive project, and we must ask 1827you to follow our rules and guidelines to be able to accept your contribution. 1828 1829The official place to start is the ['How to contribute' page]( 1830http://openjdk.java.net/contribute/). There is also an official (but somewhat 1831outdated and skimpy on details) [Developer's Guide]( 1832http://openjdk.java.net/guide/). 1833 1834If this seems overwhelming to you, the Adoption Group is there to help you! A 1835good place to start is their ['New Contributor' page]( 1836https://wiki.openjdk.java.net/display/Adoption/New+Contributor), or start 1837reading the comprehensive [Getting Started Kit]( 1838https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The 1839Adoption Group will also happily answer any questions you have about 1840contributing. Contact them by [mail]( 1841http://mail.openjdk.java.net/mailman/listinfo/adoption-discuss) or [IRC]( 1842http://openjdk.java.net/irc/). 1843 1844--- 1845# Override styles from the base CSS file that are not ideal for this document. 1846header-includes: 1847 - '<style type="text/css">pre, code, tt { color: #1d6ae5; }</style>' 1848--- 1849