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 8, it is recommended that you get the `jdk8u` forest, which contains 53incremental updates, instead of the `jdk8` forest, which was frozen at JDK 8 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, extra care must be taken to make sure the [Cygwin](#cygwin) 79 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 arm/aarch64 136 137This is not recommended. Instead, see the section on [Cross-compiling]( 138#cross-compiling). 139 140## Operating System Requirements 141 142The mainline JDK project supports Linux, Solaris, macOS, AIX and Windows. 143Support for other operating system, e.g. BSD, exists in separate "port" 144projects. 145 146In general, the JDK can be built on a wide range of versions of these operating 147systems, but the further you deviate from what is tested on a daily basis, the 148more likely you are to run into problems. 149 150This table lists the OS versions used by Oracle when building the JDK. Such 151information is always subject to change, but this table is up to date at the 152time of writing. 153 154 Operating system Vendor/version used 155 ----------------- ------------------------------------------------------- 156 Linux Oracle Enterprise Linux 6.4 / 7.1 (using kernel 3.8.13) 157 Solaris Solaris 11.1 SRU 21.4.1 / 11.2 SRU 5.5 158 macOS Mac OS X 10.9 (Mavericks) / 10.10 (Yosemite) 159 Windows Windows Server 2012 R2 160 161The double version numbers for Linux, Solaris and macOS is due to the hybrid 162model used at Oracle, where header files and external libraries from an older 163version are used when building on a more modern version of the OS. 164 165The Build Group has a wiki page with [Supported Build Platforms]( 166https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms). From 167time to time, this is updated by contributors to list successes or failures of 168building on different platforms. 169 170### Windows 171 172Windows XP is not a supported platform, but all newer Windows should be able to 173build the JDK. 174 175On Windows, it is important that you pay attention to the instructions in the 176[Special Considerations](#special-considerations). 177 178Windows is the only non-POSIX OS supported by the JDK, and as such, requires 179some extra care. A POSIX support layer is required to build on Windows. 180Currently, the only supported such layer is Cygwin. (Msys is no longer 181supported due to a too old bash; msys2 and the new Windows Subsystem for Linux 182(WSL) would likely be possible to support in a future version but that would 183require effort to implement.) 184 185Internally in the build system, all paths are represented as Unix-style paths, 186e.g. `/cygdrive/c/git/jdk/Makefile` rather than `C:\git\jdk\Makefile`. This 187rule also applies to input to the build system, e.g. in arguments to 188`configure`. So, use `--with-msvcr-dll=/cygdrive/c/msvcr100.dll` rather than 189`--with-msvcr-dll=c:\msvcr100.dll`. For details on this conversion, see the section 190on [Fixpath](#fixpath). 191 192#### Cygwin 193 194A functioning [Cygwin](http://www.cygwin.com/) environment is thus required for 195building the JDK on Windows. If you have a 64-bit OS, we strongly recommend 196using the 64-bit version of Cygwin. 197 198**Note:** Cygwin has a model of continuously updating all packages without any 199easy way to install or revert to a specific version of a package. This means 200that whenever you add or update a package in Cygwin, you might (inadvertently) 201update tools that are used by the JDK build process, and that can cause 202unexpected build problems. 203 204The JDK requires GNU Make 4.0 or greater on Windows. This is usually not a 205problem, since Cygwin currently only distributes GNU Make at a version above 2064.0. 207 208Apart from the basic Cygwin installation, the following packages must also be 209installed: 210 211 * `autoconf` 212 * `make` 213 * `zip` 214 * `unzip` 215 216Often, you can install these packages using the following command line: 217``` 218<path to Cygwin setup>/setup-x86_64 -q -P autoconf -P make -P unzip -P zip 219``` 220 221Unfortunately, Cygwin can be unreliable in certain circumstances. If you 222experience build tool crashes or strange issues when building on Windows, 223please check the Cygwin FAQ on the ["BLODA" list]( 224https://cygwin.com/faq/faq.html#faq.using.bloda) and the section on [fork() 225failures](https://cygwin.com/faq/faq.html#faq.using.fixing-fork-failures). 226 227### Solaris 228 229See `make/devkit/solaris11.1-package-list.txt` for a list of recommended 230packages to install when building on Solaris. The versions specified in this 231list is the versions used by the daily builds at Oracle, and is likely to work 232properly. 233 234Older versions of Solaris shipped a broken version of `objcopy`. At least 235version 2.21.1 is needed, which is provided by Solaris 11 Update 1. Objcopy is 236needed if you want to have external debug symbols. Please make sure you are 237using at least version 2.21.1 of objcopy, or that you disable external debug 238symbols. 239 240### macOS 241 242Apple is using a quite aggressive scheme of pushing OS updates, and coupling 243these updates with required updates of Xcode. Unfortunately, this makes it 244difficult for a project such as the JDK to keep pace with a continuously updated 245machine running macOS. See the section on [Apple Xcode](#apple-xcode) on some 246strategies to deal with this. 247 248It is recommended that you use at least Mac OS X 10.13 (High Sierra). At the time 249of writing, the JDK has been successfully compiled on macOS 10.12 (Sierra). 250 251The standard macOS environment contains the basic tooling needed to build, but 252for external libraries a package manager is recommended. The JDK uses 253[homebrew](https://brew.sh/) in the examples, but feel free to use whatever 254manager you want (or none). 255 256### Linux 257 258It is often not much problem to build the JDK on Linux. The only general advice 259is to try to use the compilers, external libraries and header files as provided 260by your distribution. 261 262The basic tooling is provided as part of the core operating system, but you 263will most likely need to install developer packages. 264 265For apt-based distributions (Debian, Ubuntu, etc), try this: 266``` 267sudo apt-get install build-essential 268``` 269 270For rpm-based distributions (Fedora, Red Hat, etc), try this: 271``` 272sudo yum groupinstall "Development Tools" 273``` 274 275### AIX 276 277The regular builds by SAP is using AIX version 7.1, but AIX 5.3 is also 278supported. See the [OpenJDK PowerPC Port Status Page]( 279http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details. 280 281## Native Compiler (Toolchain) Requirements 282 283Large portions of the JDK consists of native code, that needs to be compiled to 284be able to run on the target platform. In theory, toolchain and operating 285system should be independent factors, but in practice there's more or less a 286one-to-one correlation between target operating system and toolchain. 287 288 Operating system Supported toolchain 289 ------------------ ------------------------- 290 Linux gcc, clang 291 macOS Apple Xcode (using clang) 292 Solaris Oracle Solaris Studio 293 AIX IBM XL C/C++ 294 Windows Microsoft Visual Studio 295 296Please see the individual sections on the toolchains for version 297recommendations. As a reference, these versions of the toolchains are used, at 298the time of writing, by Oracle for the daily builds of the JDK. It should be 299possible to compile the JDK with both older and newer versions, but the closer 300you stay to this list, the more likely you are to compile successfully without 301issues. 302 303 Operating system Toolchain version 304 ------------------ ------------------------------------------------------- 305 Linux gcc 7.3.0 306 macOS Apple Xcode 9.4 (using clang 9.1.0) 307 Solaris Oracle Solaris Studio 12.4 (with compiler version 5.13) 308 Windows Microsoft Visual Studio 2017 update 15.9.16 309 310### gcc 311 312The minimum accepted version of gcc is 4.8. Older versions will generate a warning 313by `configure` and are unlikely to work. 314 315The JDK is currently known to be able to compile with at least version 7.4 of 316gcc. 317 318In general, any version between these two should be usable. 319 320### clang 321 322The minimum accepted version of clang is 3.2. Older versions will not be 323accepted by `configure`. 324 325To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`. 326 327### Apple Xcode 328 329The oldest supported version of Xcode is 8. 330 331You will need the Xcode command lines developers tools to be able to build 332the JDK. (Actually, *only* the command lines tools are needed, not the IDE.) 333The simplest way to install these is to run: 334``` 335xcode-select --install 336``` 337 338It is advisable to keep an older version of Xcode for building the JDK when 339updating Xcode. This [blog page]( 340http://iosdevelopertips.com/xcode/install-multiple-versions-of-xcode.html) has 341good suggestions on managing multiple Xcode versions. To use a specific version 342of Xcode, use `xcode-select -s` before running `configure`, or use 343`--with-toolchain-path` to point to the version of Xcode to use, e.g. 344`configure --with-toolchain-path=/Applications/Xcode8.app/Contents/Developer/usr/bin` 345 346If you have recently (inadvertently) updated your OS and/or Xcode version, and 347the JDK can no longer be built, please see the section on [Problems with the 348Build Environment](#problems-with-the-build-environment), and [Getting 349Help](#getting-help) to find out if there are any recent, non-merged patches 350available for this update. 351 352### Oracle Solaris Studio 353 354The minimum accepted version of the Solaris Studio compilers is 5.13 355(corresponding to Solaris Studio 12.4). Older versions will not be accepted by 356configure. 357 358The Solaris Studio installation should contain at least these packages: 359 360 Package Version 361 -------------------------------------------------- ------------- 362 developer/solarisstudio-124/backend 12.4-1.0.6.0 363 developer/solarisstudio-124/c++ 12.4-1.0.10.0 364 developer/solarisstudio-124/cc 12.4-1.0.4.0 365 developer/solarisstudio-124/library/c++-libs 12.4-1.0.10.0 366 developer/solarisstudio-124/library/math-libs 12.4-1.0.0.1 367 developer/solarisstudio-124/library/studio-gccrt 12.4-1.0.0.1 368 developer/solarisstudio-124/studio-common 12.4-1.0.0.1 369 developer/solarisstudio-124/studio-ja 12.4-1.0.0.1 370 developer/solarisstudio-124/studio-legal 12.4-1.0.0.1 371 developer/solarisstudio-124/studio-zhCN 12.4-1.0.0.1 372 373Compiling with Solaris Studio can sometimes be finicky. This is the exact 374version used by Oracle, which worked correctly at the time of writing: 375``` 376$ cc -V 377cc: Sun C 5.13 SunOS_i386 2014/10/20 378$ CC -V 379CC: Sun C++ 5.13 SunOS_i386 151846-10 2015/10/30 380``` 381 382### Microsoft Visual Studio 383 384The minimum accepted version of Visual Studio is 2010. Older versions will not 385be accepted by `configure`. The maximum accepted version of Visual Studio is 3862019. Versions older than 2017 are unlikely to continue working for long. 387 388If you have multiple versions of Visual Studio installed, `configure` will by 389default pick the latest. You can request a specific version to be used by 390setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2015`. 391 392If you get `LINK: fatal error LNK1123: failure during conversion to COFF: file 393invalid` when building using Visual Studio 2010, you have encountered 394[KB2757355](http://support.microsoft.com/kb/2757355), a bug triggered by a 395specific installation order. However, the solution suggested by the KB article 396does not always resolve the problem. See [this stackoverflow discussion]( 397https://stackoverflow.com/questions/10888391) for other suggestions. 398 399### IBM XL C/C++ 400 401The regular builds by SAP is using version 12.1, described as `IBM XL C/C++ for 402AIX, V12.1 (5765-J02, 5725-C72) Version: 12.01.0000.0017`. 403 404See the [OpenJDK PowerPC Port Status Page]( 405http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details. 406 407## Boot JDK Requirements 408 409Paradoxically, building the JDK requires a pre-existing JDK. This is called the 410"boot JDK". The boot JDK does not, however, have to be a JDK built directly from 411the source code available in the OpenJDK Community. If you are porting the JDK 412to a new platform, chances are that there already exists another JDK for that 413platform that is usable as boot JDK. 414 415The rule of thumb is that the boot JDK for building JDK major version *N* 416should be a JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be 417suitable as boot JDK. However, the JDK should be able to "build itself", so an 418up-to-date build of the current JDK source is an acceptable alternative. If 419you are following the *N-1* rule, make sure you've got the latest update 420version, since JDK 8 GA might not be able to build JDK 9 on all platforms. 421 422Early in the release cycle, version *N-1* may not yet have been released. In 423that case, the preferred boot JDK will be version *N-2* until version *N-1* 424is available. 425 426If the boot JDK is not automatically detected, or the wrong JDK is picked, use 427`--with-boot-jdk` to point to the JDK to use. 428 429### Getting JDK binaries 430 431JDK binaries for Linux, Windows and macOS can be downloaded from 432[jdk.java.net](http://jdk.java.net). An alternative is to download the 433[Oracle JDK](http://www.oracle.com/technetwork/java/javase/downloads). Another 434is the [Adopt OpenJDK Project](https://adoptopenjdk.net/), which publishes 435experimental prebuilt binaries for various platforms. 436 437On Linux you can also get a JDK from the Linux distribution. On apt-based 438distros (like Debian and Ubuntu), `sudo apt-get install openjdk-<VERSION>-jdk` 439is typically enough to install a JDK \<VERSION\>. On rpm-based distros (like 440Fedora and Red Hat), try `sudo yum install java-<VERSION>-openjdk-devel`. 441 442## External Library Requirements 443 444Different platforms require different external libraries. In general, libraries 445are not optional - that is, they are either required or not used. 446 447If a required library is not detected by `configure`, you need to provide the 448path to it. There are two forms of the `configure` arguments to point to an 449external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to 450include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise, 451but require the include files and library files to reside in a default 452hierarchy under this directory. In most cases, it works fine. 453 454As a fallback, the second version allows you to point to the include directory 455and the lib directory separately. 456 457### FreeType 458 459FreeType2 from [The FreeType Project](http://www.freetype.org/) is not required 460on any platform. The exception is on Unix-based platforms when configuring such 461that the build artifacts will reference a system installed library, 462rather than bundling the JDK's own copy. 463 464 * To install on an apt-based Linux, try running `sudo apt-get install 465 libfreetype6-dev`. 466 * To install on an rpm-based Linux, try running `sudo yum install 467 freetype-devel`. 468 * To install on Solaris, try running `pkg install system/library/freetype-2`. 469 470Use `--with-freetype-include=<path>` and `--with-freetype-lib=<path>` 471if `configure` does not automatically locate the platform FreeType files. 472 473### CUPS 474 475CUPS, [Common UNIX Printing System](http://www.cups.org) header files are 476required on all platforms, except Windows. Often these files are provided by 477your operating system. 478 479 * To install on an apt-based Linux, try running `sudo apt-get install 480 libcups2-dev`. 481 * To install on an rpm-based Linux, try running `sudo yum install 482 cups-devel`. 483 * To install on Solaris, try running `pkg install print/cups`. 484 485Use `--with-cups=<path>` if `configure` does not properly locate your CUPS 486files. 487 488### X11 489 490Certain [X11](http://www.x.org/) libraries and include files are required on 491Linux and Solaris. 492 493 * To install on an apt-based Linux, try running `sudo apt-get install 494 libx11-dev libxext-dev libxrender-dev libxtst-dev libxt-dev`. 495 * To install on an rpm-based Linux, try running `sudo yum install 496 libXtst-devel libXt-devel libXrender-devel libXi-devel`. 497 * To install on Solaris, try running `pkg install x11/header/x11-protocols 498 x11/library/libice x11/library/libpthread-stubs x11/library/libsm 499 x11/library/libx11 x11/library/libxau x11/library/libxcb 500 x11/library/libxdmcp x11/library/libxevie x11/library/libxext 501 x11/library/libxrender x11/library/libxscrnsaver x11/library/libxtst 502 x11/library/toolkit/libxt`. 503 504Use `--with-x=<path>` if `configure` does not properly locate your X11 files. 505 506### ALSA 507 508ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is 509required on Linux. At least version 0.9.1 of ALSA is required. 510 511 * To install on an apt-based Linux, try running `sudo apt-get install 512 libasound2-dev`. 513 * To install on an rpm-based Linux, try running `sudo yum install 514 alsa-lib-devel`. 515 516Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA 517files. 518 519### libffi 520 521libffi, the [Portable Foreign Function Interface Library]( 522http://sourceware.org/libffi) is required when building the Zero version of 523Hotspot. 524 525 * To install on an apt-based Linux, try running `sudo apt-get install 526 libffi-dev`. 527 * To install on an rpm-based Linux, try running `sudo yum install 528 libffi-devel`. 529 530Use `--with-libffi=<path>` if `configure` does not properly locate your libffi 531files. 532 533## Build Tools Requirements 534 535### Autoconf 536 537The JDK requires [Autoconf](http://www.gnu.org/software/autoconf) on all 538platforms. At least version 2.69 is required. 539 540 * To install on an apt-based Linux, try running `sudo apt-get install 541 autoconf`. 542 * To install on an rpm-based Linux, try running `sudo yum install 543 autoconf`. 544 * To install on macOS, try running `brew install autoconf`. 545 * To install on Windows, try running `<path to Cygwin setup>/setup-x86_64 -q 546 -P autoconf`. 547 548If `configure` has problems locating your installation of autoconf, you can 549specify it using the `AUTOCONF` environment variable, like this: 550 551``` 552AUTOCONF=<path to autoconf> configure ... 553``` 554 555### GNU Make 556 557The JDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors 558of make are supported. 559 560At least version 3.81 of GNU Make must be used. For distributions supporting 561GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful 562functionality to handle parallel building (supported by `--with-output-sync`) 563and speed and stability improvements. 564 565Note that `configure` locates and verifies a properly functioning version of 566`make` and stores the path to this `make` binary in the configuration. If you 567start a build using `make` on the command line, you will be using the version 568of make found first in your `PATH`, and not necessarily the one stored in the 569configuration. This initial make will be used as "bootstrap make", and in a 570second stage, the make located by `configure` will be called. Normally, this 571will present no issues, but if you have a very old `make`, or a non-GNU Make 572`make` in your path, this might cause issues. 573 574If you want to override the default make found by `configure`, use the `MAKE` 575configure variable, e.g. `configure MAKE=/opt/gnu/make`. 576 577On Solaris, it is common to call the GNU version of make by using `gmake`. 578 579### GNU Bash 580 581The JDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells 582are supported. 583 584At least version 3.2 of GNU Bash must be used. 585 586## Running Configure 587 588To build the JDK, you need a "configuration", which consists of a directory 589where to store the build output, coupled with information about the platform, 590the specific build machine, and choices that affect how the JDK is built. 591 592The configuration is created by the `configure` script. The basic invocation of 593the `configure` script looks like this: 594 595``` 596bash configure [options] 597``` 598 599This will create an output directory containing the configuration and setup an 600area for the build result. This directory typically looks like 601`build/linux-x64-server-release`, but the actual name depends on your specific 602configuration. (It can also be set directly, see [Using Multiple 603Configurations](#using-multiple-configurations)). This directory is referred to 604as `$BUILD` in this documentation. 605 606`configure` will try to figure out what system you are running on and where all 607necessary build components are. If you have all prerequisites for building 608installed, it should find everything. If it fails to detect any component 609automatically, it will exit and inform you about the problem. 610 611Some command line examples: 612 613 * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`: 614 ``` 615 bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32 616 ``` 617 618 * Create a debug build with the `server` JVM and DTrace enabled: 619 ``` 620 bash configure --enable-debug --with-jvm-variants=server --enable-dtrace 621 ``` 622 623### Common Configure Arguments 624 625Here follows some of the most common and important `configure` argument. 626 627To get up-to-date information on *all* available `configure` argument, please 628run: 629``` 630bash configure --help 631``` 632 633(Note that this help text also include general autoconf options, like 634`--dvidir`, that is not relevant to the JDK. To list only JDK-specific 635features, use `bash configure --help=short` instead.) 636 637#### Configure Arguments for Tailoring the Build 638 639 * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand 640 for `--with-debug-level=fastdebug`) 641 * `--with-debug-level=<level>` - Set the debug level, which can be `release`, 642 `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized` 643 is variant of `release` with additional Hotspot debug code. 644 * `--with-native-debug-symbols=<method>` - Specify if and how native debug 645 symbols should be built. Available methods are `none`, `internal`, 646 `external`, `zipped`. Default behavior depends on platform. See [Native 647 Debug Symbols](#native-debug-symbols) for more details. 648 * `--with-version-string=<string>` - Specify the version string this build 649 will be identified with. 650 * `--with-version-<part>=<value>` - A group of options, where `<part>` can be 651 any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use 652 these options to modify just the corresponding part of the version string 653 from the default, or the value provided by `--with-version-string`. 654 * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant 655 (or variants) of Hotspot. Valid variants are: `server`, `client`, 656 `minimal`, `core`, `zero`, `custom`. Note that not all 657 variants are possible to combine in a single build. 658 * `--with-jvm-features=<feature>[,<feature>...]` - Use the specified JVM 659 features when building Hotspot. The list of features will be enabled on top 660 of the default list. For the `custom` JVM variant, this default list is 661 empty. A complete list of available JVM features can be found using `bash 662 configure --help`. 663 * `--with-target-bits=<bits>` - Create a target binary suitable for running 664 on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build 665 platform, instead of doing a full cross-compile. (This is known as a 666 *reduced* build.) 667 668#### Configure Arguments for Native Compilation 669 670 * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources 671 * `--with-sysroot=<path>` - Use this directory as sysroot 672 * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the 673 default path when searching for all kinds of binaries 674 * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when 675 searching for toolchain binaries (compilers etc) 676 * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C 677 files 678 * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++ 679 files 680 * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK 681 libraries 682 683#### Configure Arguments for External Dependencies 684 685 * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK]( 686 #boot-jdk-requirements) 687 * `--with-freetype=<path>` - Set the path to [FreeType](#freetype) 688 * `--with-cups=<path>` - Set the path to [CUPS](#cups) 689 * `--with-x=<path>` - Set the path to [X11](#x11) 690 * `--with-alsa=<path>` - Set the path to [ALSA](#alsa) 691 * `--with-libffi=<path>` - Set the path to [libffi](#libffi) 692 * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests]( 693 #running-tests) 694 695Certain third-party libraries used by the JDK (libjpeg, giflib, libpng, lcms 696and zlib) are included in the JDK repository. The default behavior of the 697JDK build is to use this version of these libraries, but they might be 698replaced by an external version. To do so, specify `system` as the `<source>` 699option in these arguments. (The default is `bundled`). 700 701 * `--with-libjpeg=<source>` - Use the specified source for libjpeg 702 * `--with-giflib=<source>` - Use the specified source for giflib 703 * `--with-libpng=<source>` - Use the specified source for libpng 704 * `--with-lcms=<source>` - Use the specified source for lcms 705 * `--with-zlib=<source>` - Use the specified source for zlib 706 707On Linux, it is possible to select either static or dynamic linking of the C++ 708runtime. The default is static linking, with dynamic linking as fallback if the 709static library is not found. 710 711 * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic` 712 or `default`) for linking the C++ runtime. 713 714### Configure Control Variables 715 716It is possible to control certain aspects of `configure` by overriding the 717value of `configure` variables, either on the command line or in the 718environment. 719 720Normally, this is **not recommended**. If used improperly, it can lead to a 721broken configuration. Unless you're well versed in the build system, this is 722hard to use properly. Therefore, `configure` will print a warning if this is 723detected. 724 725However, there are a few `configure` variables, known as *control variables* 726that are supposed to be overriden on the command line. These are variables that 727describe the location of tools needed by the build, like `MAKE` or `GREP`. If 728any such variable is specified, `configure` will use that value instead of 729trying to autodetect the tool. For instance, `bash configure 730MAKE=/opt/gnumake4.0/bin/make`. 731 732If a configure argument exists, use that instead, e.g. use `--with-jtreg` 733instead of setting `JTREGEXE`. 734 735Also note that, despite what autoconf claims, setting `CFLAGS` will not 736accomplish anything. Instead use `--with-extra-cflags` (and similar for 737`cxxflags` and `ldflags`). 738 739## Running Make 740 741When you have a proper configuration, all you need to do to build the JDK is to 742run `make`. (But see the warning at [GNU Make](#gnu-make) about running the 743correct version of make.) 744 745When running `make` without any arguments, the default target is used, which is 746the same as running `make default` or `make jdk`. This will build a minimal (or 747roughly minimal) set of compiled output (known as an "exploded image") needed 748for a developer to actually execute the newly built JDK. The idea is that in an 749incremental development fashion, when doing a normal make, you should only 750spend time recompiling what's changed (making it purely incremental) and only 751do the work that's needed to actually run and test your code. 752 753The output of the exploded image resides in `$BUILD/jdk`. You can test the 754newly built JDK like this: `$BUILD/jdk/bin/java -version`. 755 756### Common Make Targets 757 758Apart from the default target, here are some common make targets: 759 760 * `hotspot` - Build all of hotspot (but only hotspot) 761 * `hotspot-<variant>` - Build just the specified jvm variant 762 * `images` or `product-images` - Build the JDK image 763 * `docs` or `docs-image` - Build the documentation image 764 * `test-image` - Build the test image 765 * `all` or `all-images` - Build all images (product, docs and test) 766 * `bootcycle-images` - Build images twice, second time with newly built JDK 767 (good for testing) 768 * `clean` - Remove all files generated by make, but not those generated by 769 configure 770 * `dist-clean` - Remove all files, including configuration 771 772Run `make help` to get an up-to-date list of important make targets and make 773control variables. 774 775It is possible to build just a single module, a single phase, or a single phase 776of a single module, by creating make targets according to these followin 777patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`, 778`launchers`, `libs` or `rmic`. See [Using Fine-Grained Make Targets]( 779#using-fine-grained-make-targets) for more details about this functionality. 780 781 * `<phase>` - Build the specified phase and everything it depends on 782 * `<module>` - Build the specified module and everything it depends on 783 * `<module>-<phase>` - Compile the specified phase for the specified module 784 and everything it depends on 785 786Similarly, it is possible to clean just a part of the build by creating make 787targets according to these patterns: 788 789 * `clean-<outputdir>` - Remove the subdir in the output dir with the name 790 * `clean-<phase>` - Remove all build results related to a certain build 791 phase 792 * `clean-<module>` - Remove all build results related to a certain module 793 * `clean-<module>-<phase>` - Remove all build results related to a certain 794 module and phase 795 796### Make Control Variables 797 798It is possible to control `make` behavior by overriding the value of `make` 799variables, either on the command line or in the environment. 800 801Normally, this is **not recommended**. If used improperly, it can lead to a 802broken build. Unless you're well versed in the build system, this is hard to 803use properly. Therefore, `make` will print a warning if this is detected. 804 805However, there are a few `make` variables, known as *control variables* that 806are supposed to be overriden on the command line. These make up the "make time" 807configuration, as opposed to the "configure time" configuration. 808 809#### General Make Control Variables 810 811 * `JOBS` - Specify the number of jobs to build with. See [Build 812 Performance](#build-performance). 813 * `LOG` - Specify the logging level and functionality. See [Checking the 814 Build Log File](#checking-the-build-log-file) 815 * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using 816 Multiple Configurations](#using-multiple-configurations) 817 818#### Test Make Control Variables 819 820These make control variables only make sense when running tests. Please see 821[Testing the JDK](testing.html) for details. 822 823 * `TEST` 824 * `TEST_JOBS` 825 * `JTREG` 826 * `GTEST` 827 828#### Advanced Make Control Variables 829 830These advanced make control variables can be potentially unsafe. See [Hints and 831Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and 832[Understanding the Build System](#understanding-the-build-system) for details. 833 834 * `SPEC` 835 * `CONF_CHECK` 836 * `COMPARE_BUILD` 837 * `JDK_FILTER` 838 839## Running Tests 840 841Most of the JDK tests are using the [JTReg](http://openjdk.java.net/jtreg) 842test framework. Make sure that your configuration knows where to find your 843installation of JTReg. If this is not picked up automatically, use the 844`--with-jtreg=<path to jtreg home>` option to point to the JTReg framework. 845Note that this option should point to the JTReg home, i.e. the top directory, 846containing `lib/jtreg.jar` etc. 847 848The [Adoption Group](https://wiki.openjdk.java.net/display/Adoption) provides 849recent builds of jtreg [here]( 850https://adopt-openjdk.ci.cloudbees.com/job/jtreg/lastSuccessfulBuild/artifact). 851Download the latest `.tar.gz` file, unpack it, and point `--with-jtreg` to the 852`jtreg` directory that you just unpacked. 853 854To execute the most basic tests (tier 1), use: 855``` 856make run-test-tier1 857``` 858 859For more details on how to run tests, please see the [Testing 860the JDK](testing.html) document. 861 862## Cross-compiling 863 864Cross-compiling means using one platform (the *build* platform) to generate 865output that can ran on another platform (the *target* platform). 866 867The typical reason for cross-compiling is that the build is performed on a more 868powerful desktop computer, but the resulting binaries will be able to run on a 869different, typically low-performing system. Most of the complications that 870arise when building for embedded is due to this separation of *build* and 871*target* systems. 872 873This requires a more complex setup and build procedure. This section assumes 874you are familiar with cross-compiling in general, and will only deal with the 875particularities of cross-compiling the JDK. If you are new to cross-compiling, 876please see the [external links at Wikipedia]( 877https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start 878on reading materials. 879 880Cross-compiling the JDK requires you to be able to build both for the build 881platform and for the target platform. The reason for the former is that we need 882to build and execute tools during the build process, both native tools and Java 883tools. 884 885If all you want to do is to compile a 32-bit version, for the same OS, on a 88664-bit machine, consider using `--with-target-bits=32` instead of doing a 887full-blown cross-compilation. (While this surely is possible, it's a lot more 888work and will take much longer to build.) 889 890### Cross compiling the easy way with OpenJDK devkits 891 892The OpenJDK build system provides out-of-the box support for creating and using 893so called devkits. A `devkit` is basically a collection of a cross-compiling 894toolchain and a sysroot environment which can easily be used together with the 895`--with-devkit` configure option to cross compile the OpenJDK. On Linux/x86_64, 896the following command: 897``` 898bash configure --with-devkit=<devkit-path> --openjdk-target=ppc64-linux-gnu && make 899``` 900 901will configure and build OpenJDK for Linux/ppc64 assuming that `<devkit-path>` 902points to a Linux/x86_64 to Linux/ppc64 devkit. 903 904Devkits can be created from the `make/devkit` directory by executing: 905``` 906make [ TARGETS="<TARGET_TRIPLET>+" ] [ BASE_OS=<OS> ] [ BASE_OS_VERSION=<VER> ] 907``` 908 909where `TARGETS` contains one or more `TARGET_TRIPLET`s of the form 910described in [section 3.4 of the GNU Autobook]( 911https://sourceware.org/autobook/autobook/autobook_17.html). If no 912targets are given, a native toolchain for the current platform will be 913created. Currently, at least the following targets are known to work: 914 915 Supported devkit targets 916 ------------------------ 917 x86_64-linux-gnu 918 aarch64-linux-gnu 919 arm-linux-gnueabihf 920 ppc64-linux-gnu 921 ppc64le-linux-gnu 922 s390x-linux-gnu 923 924`BASE_OS` must be one of "OEL6" for Oracle Enterprise Linux 6 or 925"Fedora" (if not specified "OEL6" will be the default). If the base OS 926is "Fedora" the corresponding Fedora release can be specified with the 927help of the `BASE_OS_VERSION` option (with "27" as default version). 928If the build is successful, the new devkits can be found in the 929`build/devkit/result` subdirectory: 930``` 931cd make/devkit 932make TARGETS="ppc64le-linux-gnu aarch64-linux-gnu" BASE_OS=Fedora BASE_OS_VERSION=21 933ls -1 ../../build/devkit/result/ 934x86_64-linux-gnu-to-aarch64-linux-gnu 935x86_64-linux-gnu-to-ppc64le-linux-gnu 936``` 937 938Notice that devkits are not only useful for targeting different build 939platforms. Because they contain the full build dependencies for a 940system (i.e. compiler and root file system), they can easily be used 941to build well-known, reliable and reproducible build environments. You 942can for example create and use a devkit with GCC 7.3 and a Fedora 12 943sysroot environment (with glibc 2.11) on Ubuntu 14.04 (which doesn't 944have GCC 7.3 by default) to produce OpenJDK binaries which will run on 945all Linux systems with runtime libraries newer than the ones from 946Fedora 12 (e.g. Ubuntu 16.04, SLES 11 or RHEL 6). 947 948### Boot JDK and Build JDK 949 950When cross-compiling, make sure you use a boot JDK that runs on the *build* 951system, and not on the *target* system. 952 953To be able to build, we need a "Build JDK", which is a JDK built from the 954current sources (that is, the same as the end result of the entire build 955process), but able to run on the *build* system, and not the *target* system. 956(In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when 957building JDK 9.) 958 959The build process will create a minimal Build JDK for you, as part of building. 960To speed up the build, you can use `--with-build-jdk` to `configure` to point 961to a pre-built Build JDK. Please note that the build result is unpredictable, 962and can possibly break in subtle ways, if the Build JDK does not **exactly** 963match the current sources. 964 965### Specifying the Target Platform 966 967You *must* specify the target platform when cross-compiling. Doing so will also 968automatically turn the build into a cross-compiling mode. The simplest way to 969do this is to use the `--openjdk-target` argument, e.g. 970`--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`. 971This will automatically set the `--build`, `--host` and `--target` options for 972autoconf, which can otherwise be confusing. (In autoconf terminology, the 973"target" is known as "host", and "target" is used for building a Canadian 974cross-compiler.) 975 976### Toolchain Considerations 977 978You will need two copies of your toolchain, one which generates output that can 979run on the target system (the normal, or *target*, toolchain), and one that 980generates output that can run on the build system (the *build* toolchain). Note 981that cross-compiling is only supported for gcc at the time being. The gcc 982standard is to prefix cross-compiling toolchains with the target denominator. 983If you follow this standard, `configure` is likely to pick up the toolchain 984correctly. 985 986The *build* toolchain will be autodetected just the same way the normal 987*build*/*target* toolchain will be autodetected when not cross-compiling. If 988this is not what you want, or if the autodetection fails, you can specify a 989devkit containing the *build* toolchain using `--with-build-devkit` to 990`configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments. 991 992It is often helpful to locate the cross-compilation tools, headers and 993libraries in a separate directory, outside the normal path, and point out that 994directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and 995appending the directory when searching for cross-compilations tools 996(`--with-toolchain-path`). As a compact form, you can also use `--with-devkit` 997to point to a single directory, if it is correctly setup. (See `basics.m4` for 998details.) 999 1000If you are unsure what toolchain and versions to use, these have been proved 1001working at the time of writing: 1002 1003 * [aarch64]( 1004https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-linux-gnu-4.8-2013.11_linux.tar.xz) 1005 * [arm 32-bit hardware floating point]( 1006https://launchpad.net/linaro-toolchain-unsupported/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux.tar.bz2) 1007 1008### Native Libraries 1009 1010You will need copies of external native libraries for the *target* system, 1011present on the *build* machine while building. 1012 1013Take care not to replace the *build* system's version of these libraries by 1014mistake, since that can render the *build* machine unusable. 1015 1016Make sure that the libraries you point to (ALSA, X11, etc) are for the 1017*target*, not the *build*, platform. 1018 1019#### ALSA 1020 1021You will need alsa libraries suitable for your *target* system. For most cases, 1022using Debian's pre-built libraries work fine. 1023 1024Note that alsa is needed even if you only want to build a headless JDK. 1025 1026 * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and 1027 search for the `libasound2` and `libasound2-dev` packages for your *target* 1028 system. Download them to /tmp. 1029 1030 * Install the libraries into the cross-compilation toolchain. For instance: 1031``` 1032cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc 1033dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb . 1034dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb . 1035``` 1036 1037 * If alsa is not properly detected by `configure`, you can point it out by 1038 `--with-alsa`. 1039 1040#### X11 1041 1042You will need X11 libraries suitable for your *target* system. For most cases, 1043using Debian's pre-built libraries work fine. 1044 1045Note that X11 is needed even if you only want to build a headless JDK. 1046 1047 * Go to [Debian Package Search](https://www.debian.org/distrib/packages), 1048 search for the following packages for your *target* system, and download them 1049 to /tmp/target-x11: 1050 * libxi 1051 * libxi-dev 1052 * x11proto-core-dev 1053 * x11proto-input-dev 1054 * x11proto-kb-dev 1055 * x11proto-render-dev 1056 * x11proto-xext-dev 1057 * libice-dev 1058 * libxrender 1059 * libxrender-dev 1060 * libsm-dev 1061 * libxt-dev 1062 * libx11 1063 * libx11-dev 1064 * libxtst 1065 * libxtst-dev 1066 * libxext 1067 * libxext-dev 1068 1069 * Install the libraries into the cross-compilation toolchain. For instance: 1070 ``` 1071 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr 1072 mkdir X11R6 1073 cd X11R6 1074 for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done 1075 mv usr/* . 1076 cd lib 1077 cp arm-linux-gnueabihf/* . 1078 ``` 1079 1080 You can ignore the following messages. These libraries are not needed to 1081 successfully complete a full JDK build. 1082 ``` 1083 cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory 1084 cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory 1085 cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory 1086 ``` 1087 1088 * If the X11 libraries are not properly detected by `configure`, you can 1089 point them out by `--with-x`. 1090 1091### Creating And Using Sysroots With qemu-deboostrap 1092 1093Fortunately, you can create sysroots for foreign architectures with tools 1094provided by your OS. On Debian/Ubuntu systems, one could use `qemu-deboostrap` to 1095create the *target* system chroot, which would have the native libraries and headers 1096specific to that *target* system. After that, we can use the cross-compiler on the *build* 1097system, pointing into chroot to get the build dependencies right. This allows building 1098for foreign architectures with native compilation speed. 1099 1100For example, cross-compiling to AArch64 from x86_64 could be done like this: 1101 1102 * Install cross-compiler on the *build* system: 1103``` 1104apt install g++-aarch64-linux-gnu gcc-aarch64-linux-gnu 1105``` 1106 1107 * Create chroot on the *build* system, configuring it for *target* system: 1108``` 1109sudo qemu-debootstrap --arch=arm64 --verbose \ 1110 --include=fakeroot,build-essential,libx11-dev,libxext-dev,libxrender-dev,libxtst-dev,libxt-dev,libcups2-dev,libfontconfig1-dev,libasound2-dev,libfreetype6-dev,libpng12-dev \ 1111 --resolve-deps jessie /chroots/arm64 http://httpredir.debian.org/debian/ 1112``` 1113 1114 * Configure and build with newly created chroot as sysroot/toolchain-path: 1115``` 1116CC=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/ 1117make images 1118ls build/linux-aarch64-normal-server-release/ 1119``` 1120 1121The build does not create new files in that chroot, so it can be reused for multiple builds 1122without additional cleanup. 1123 1124Architectures that are known to successfully cross-compile like this are: 1125 1126 Target `CC` `CXX` `--arch=...` `--openjdk-target=...` 1127 ------------ ------------------------- --------------------------- ------------ ---------------------- 1128 x86 default default i386 i386-linux-gnu 1129 armhf gcc-arm-linux-gnueabihf g++-arm-linux-gnueabihf armhf arm-linux-gnueabihf 1130 aarch64 gcc-aarch64-linux-gnu g++-aarch64-linux-gnu arm64 aarch64-linux-gnu 1131 ppc64el gcc-powerpc64le-linux-gnu g++-powerpc64le-linux-gnu ppc64el powerpc64le-linux-gnu 1132 s390x gcc-s390x-linux-gnu g++-s390x-linux-gnu s390x s390x-linux-gnu 1133 1134Additional architectures might be supported by Debian/Ubuntu Ports. 1135 1136### Building for ARM/aarch64 1137 1138A common cross-compilation target is the ARM CPU. When building for ARM, it is 1139useful to set the ABI profile. A number of pre-defined ABI profiles are 1140available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt, 1141armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer 1142properly supported by the JDK. 1143 1144The JDK contains two different ports for the aarch64 platform, one is the 1145original aarch64 port from the [AArch64 Port Project]( 1146http://openjdk.java.net/projects/aarch64-port) and one is a 64-bit version of 1147the Oracle contributed ARM port. When targeting aarch64, by the default the 1148original aarch64 port is used. To select the Oracle ARM 64 port, use 1149`--with-cpu-port=arm64`. Also set the corresponding value (`aarch64` or 1150`arm64`) to --with-abi-profile, to ensure a consistent build. 1151 1152### Verifying the Build 1153 1154The build will end up in a directory named like 1155`build/linux-arm-normal-server-release`. 1156 1157Inside this build output directory, the `images/jdk` will contain the newly 1158built JDK, for your *target* system. 1159 1160Copy these folders to your *target* system. Then you can run e.g. 1161`images/jdk/bin/java -version`. 1162 1163## Build Performance 1164 1165Building the JDK requires a lot of horsepower. Some of the build tools can be 1166adjusted to utilize more or less of resources such as parallel threads and 1167memory. The `configure` script analyzes your system and selects reasonable 1168values for such options based on your hardware. If you encounter resource 1169problems, such as out of memory conditions, you can modify the detected values 1170with: 1171 1172 * `--with-num-cores` -- number of cores in the build system, e.g. 1173 `--with-num-cores=8`. 1174 1175 * `--with-memory-size` -- memory (in MB) available in the build system, e.g. 1176 `--with-memory-size=1024` 1177 1178You can also specify directly the number of build jobs to use with 1179`--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag 1180to `make`. In most cases it will be ignored by the makefiles, but it can cause 1181problems for some make targets. 1182 1183It might also be necessary to specify the JVM arguments passed to the Boot JDK, 1184using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the 1185default JVM arguments passed to the Boot JDK. 1186 1187At the end of a successful execution of `configure`, you will get a performance 1188summary, indicating how well the build will perform. Here you will also get 1189performance hints. If you want to build fast, pay attention to those! 1190 1191If you want to tweak build performance, run with `make LOG=info` to get a build 1192time summary at the end of the build process. 1193 1194### Disk Speed 1195 1196If you are using network shares, e.g. via NFS, for your source code, make sure 1197the build directory is situated on local disk (e.g. by `ln -s 1198/localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely 1199high for building on a network share; close to unusable. 1200 1201Also, make sure that your build tools (including Boot JDK and toolchain) is 1202located on a local disk and not a network share. 1203 1204As has been stressed elsewhere, do use SSD for source code and build directory, 1205as well as (if possible) the build tools. 1206 1207### Virus Checking 1208 1209The use of virus checking software, especially on Windows, can *significantly* 1210slow down building of the JDK. If possible, turn off such software, or exclude 1211the directory containing the JDK source code from on-the-fly checking. 1212 1213### Ccache 1214 1215The JDK build supports building with ccache when using gcc or clang. Using 1216ccache can radically speed up compilation of native code if you often rebuild 1217the same sources. Your milage may vary however, so we recommend evaluating it 1218for yourself. To enable it, make sure it's on the path and configure with 1219`--enable-ccache`. 1220 1221### Precompiled Headers 1222 1223By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains 1224were it is properly supported (clang, gcc, and Visual Studio). Normally, this 1225speeds up the build process, but in some circumstances, it can actually slow 1226things down. 1227 1228You can experiment by disabling precompiled headers using 1229`--disable-precompiled-headers`. 1230 1231### Icecc / icecream 1232 1233[icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a 1234distributed compiler network. If you have multiple machines available for 1235building the JDK, you can drastically cut individual build times by utilizing 1236it. 1237 1238To use, setup an icecc network, and install icecc on the build machine. Then 1239run `configure` using `--enable-icecc`. 1240 1241### Using sjavac 1242 1243To speed up Java compilation, especially incremental compilations, you can try 1244the experimental sjavac compiler by using `--enable-sjavac`. 1245 1246### Building the Right Target 1247 1248Selecting the proper target to build can have dramatic impact on build time. 1249For normal usage, `jdk` or the default target is just fine. You only need to 1250build `images` for shipping, or if your tests require it. 1251 1252See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on 1253how to build an even smaller subset of the product. 1254 1255## Troubleshooting 1256 1257If your build fails, it can sometimes be difficult to pinpoint the problem or 1258find a proper solution. 1259 1260### Locating the Source of the Error 1261 1262When a build fails, it can be hard to pinpoint the actual cause of the error. 1263In a typical build process, different parts of the product build in parallel, 1264with the output interlaced. 1265 1266#### Build Failure Summary 1267 1268To help you, the build system will print a failure summary at the end. It looks 1269like this: 1270 1271``` 1272ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2) 1273 1274=== Output from failing command(s) repeated here === 1275* For target hotspot_variant-server_libjvm_objs_psMemoryPool.o: 1276/localhome/git/jdk-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type 1277 ... (rest of output omitted) 1278 1279* All command lines available in /localhome/git/jdk-sandbox/build/linux-x64/make-support/failure-logs. 1280=== End of repeated output === 1281 1282=== Make failed targets repeated here === 1283lib/CompileJvm.gmk:207: recipe for target '/localhome/git/jdk-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed 1284make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed 1285=== End of repeated output === 1286 1287Hint: Try searching the build log for the name of the first failed target. 1288Hint: If caused by a warning, try configure --disable-warnings-as-errors. 1289``` 1290 1291Let's break it down! First, the selected configuration, and the top-level 1292target you entered on the command line that caused the failure is printed. 1293 1294Then, between the `Output from failing command(s) repeated here` and `End of 1295repeated output` the first lines of output (stdout and stderr) from the actual 1296failing command is repeated. In most cases, this is the error message that 1297caused the build to fail. If multiple commands were failing (this can happen in 1298a parallel build), output from all failed commands will be printed here. 1299 1300The path to the `failure-logs` directory is printed. In this file you will find 1301a `<target>.log` file that contains the output from this command in its 1302entirety, and also a `<target>.cmd`, which contain the complete command line 1303used for running this command. You can re-run the failing command by executing 1304`. <path to failure-logs>/<target>.cmd` in your shell. 1305 1306Another way to trace the failure is to follow the chain of make targets, from 1307top-level targets to individual file targets. Between `Make failed targets 1308repeated here` and `End of repeated output` the output from make showing this 1309chain is repeated. The first failed recipe will typically contain the full path 1310to the file in question that failed to compile. Following lines will show a 1311trace of make targets why we ended up trying to compile that file. 1312 1313Finally, some hints are given on how to locate the error in the complete log. 1314In this example, we would try searching the log file for "`psMemoryPool.o`". 1315Another way to quickly locate make errors in the log is to search for "`] 1316Error`" or "`***`". 1317 1318Note that the build failure summary will only help you if the issue was a 1319compilation failure or similar. If the problem is more esoteric, or is due to 1320errors in the build machinery, you will likely get empty output logs, and `No 1321indication of failed target found` instead of the make target chain. 1322 1323#### Checking the Build Log File 1324 1325The output (stdout and stderr) from the latest build is always stored in 1326`$BUILD/build.log`. The previous build log is stored as `build.log.old`. This 1327means that it is not necessary to redirect the build output yourself if you 1328want to process it. 1329 1330You can increase the verbosity of the log file, by the `LOG` control variable 1331to `make`. If you want to see the command lines used in compilations, use 1332`LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug` 1333or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g. 1334`LOG=info,cmdlines`. The `debug` log level will show most shell commands 1335executed by make, and `trace` will show all. Beware that both these log levels 1336will produce a massive build log! 1337 1338### Fixing Unexpected Build Failures 1339 1340Most of the time, the build will fail due to incorrect changes in the source 1341code. 1342 1343Sometimes the build can fail with no apparent changes that have caused the 1344failure. If this is the first time you are building the JDK on this particular 1345computer, and the build fails, the problem is likely with your build 1346environment. But even if you have previously built the JDK with success, and it 1347now fails, your build environment might have changed (perhaps due to OS 1348upgrades or similar). But most likely, such failures are due to problems with 1349the incremental rebuild. 1350 1351#### Problems with the Build Environment 1352 1353Make sure your configuration is correct. Re-run `configure`, and look for any 1354warnings. Warnings that appear in the middle of the `configure` output is also 1355repeated at the end, after the summary. The entire log is stored in 1356`$BUILD/configure.log`. 1357 1358Verify that the summary at the end looks correct. Are you indeed using the Boot 1359JDK and native toolchain that you expect? 1360 1361By default, the JDK has a strict approach where warnings from the compiler is 1362considered errors which fail the build. For very new or very old compiler 1363versions, this can trigger new classes of warnings, which thus fails the build. 1364Run `configure` with `--disable-warnings-as-errors` to turn of this behavior. 1365(The warnings will still show, but not make the build fail.) 1366 1367#### Problems with Incremental Rebuilds 1368 1369Incremental rebuilds mean that when you modify part of the product, only the 1370affected parts get rebuilt. While this works great in most cases, and 1371significantly speed up the development process, from time to time complex 1372interdependencies will result in an incorrect build result. This is the most 1373common cause for unexpected build problems. 1374 1375Here are a suggested list of things to try if you are having unexpected build 1376problems. Each step requires more time than the one before, so try them in 1377order. Most issues will be solved at step 1 or 2. 1378 1379 1. Make sure your repository is up-to-date 1380 1381 Run `git pull origin master` to make sure you have the latest changes. 1382 1383 2. Clean build results 1384 1385 The simplest way to fix incremental rebuild issues is to run `make clean`. 1386 This will remove all build results, but not the configuration or any build 1387 system support artifacts. In most cases, this will solve build errors 1388 resulting from incremental build mismatches. 1389 1390 3. Completely clean the build directory. 1391 1392 If this does not work, the next step is to run `make dist-clean`, or 1393 removing the build output directory (`$BUILD`). This will clean all 1394 generated output, including your configuration. You will need to re-run 1395 `configure` after this step. A good idea is to run `make 1396 print-configuration` before running `make dist-clean`, as this will print 1397 your current `configure` command line. Here's a way to do this: 1398 1399 ``` 1400 make print-configuration > current-configuration 1401 make dist-clean 1402 bash configure $(cat current-configuration) 1403 make 1404 ``` 1405 1406 4. Re-clone the Git repository 1407 1408 Sometimes the Git repository gets in a state that causes the product 1409 to be un-buildable. In such a case, the simplest solution is often the 1410 "sledgehammer approach": delete the entire repository, and re-clone it. 1411 If you have local changes, save them first to a different location using 1412 `git format-patch`. 1413 1414### Specific Build Issues 1415 1416#### Clock Skew 1417 1418If you get an error message like this: 1419``` 1420File 'xxx' has modification time in the future. 1421Clock skew detected. Your build may be incomplete. 1422``` 1423then the clock on your build machine is out of sync with the timestamps on the 1424source files. Other errors, apparently unrelated but in fact caused by the 1425clock skew, can occur along with the clock skew warnings. These secondary 1426errors may tend to obscure the fact that the true root cause of the problem is 1427an out-of-sync clock. 1428 1429If you see these warnings, reset the clock on the build machine, run `make 1430clean` and restart the build. 1431 1432#### Out of Memory Errors 1433 1434On Solaris, you might get an error message like this: 1435``` 1436Trouble writing out table to disk 1437``` 1438To solve this, increase the amount of swap space on your build machine. 1439 1440On Windows, you might get error messages like this: 1441``` 1442fatal error - couldn't allocate heap 1443cannot create ... Permission denied 1444spawn failed 1445``` 1446This can be a sign of a Cygwin problem. See the information about solving 1447problems in the [Cygwin](#cygwin) section. Rebooting the computer might help 1448temporarily. 1449 1450### Getting Help 1451 1452If none of the suggestions in this document helps you, or if you find what you 1453believe is a bug in the build system, please contact the Build Group by sending 1454a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net). 1455Please include the relevant parts of the configure and/or build log. 1456 1457If you need general help or advice about developing for the JDK, you can also 1458contact the Adoption Group. See the section on [Contributing to OpenJDK]( 1459#contributing-to-openjdk) for more information. 1460 1461## Hints and Suggestions for Advanced Users 1462 1463### Bash Completion 1464 1465The `configure` and `make` commands tries to play nice with bash command-line 1466completion (using `<tab>` or `<tab><tab>`). To use this functionality, make 1467sure you enable completion in your `~/.bashrc` (see instructions for bash in 1468your operating system). 1469 1470Make completion will work out of the box, and will complete valid make targets. 1471For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`. 1472 1473The `configure` script can get completion for options, but for this to work you 1474need to help `bash` on the way. The standard way of running the script, `bash 1475configure`, will not be understood by bash completion. You need `configure` to 1476be the command to run. One way to achieve this is to add a simple helper script 1477to your path: 1478 1479``` 1480cat << EOT > /tmp/configure 1481#!/bin/bash 1482if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then 1483 echo >&2 "Abort: Trying to call configure helper recursively" 1484 exit 1 1485fi 1486 1487bash \$PWD/configure "\$@" 1488EOT 1489chmod +x /tmp/configure 1490sudo mv /tmp/configure /usr/local/bin 1491``` 1492 1493Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`. 1494 1495### Using Multiple Configurations 1496 1497You can have multiple configurations for a single source forest. When you 1498create a new configuration, run `configure --with-conf-name=<name>` to create a 1499configuration with the name `<name>`. Alternatively, you can create a directory 1500under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd 1501build/<name> && bash ../../configure`. 1502 1503Then you can build that configuration using `make CONF_NAME=<name>` or `make 1504CONF=<pattern>`, where `<pattern>` is a substring matching one or several 1505configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will 1506match *all* available configuration, so `make CONF= hotspot` will build the 1507`hotspot` target for all configurations. Alternatively, you can execute `make` 1508in the configuration directory, e.g. `cd build/<name> && make`. 1509 1510### Handling Reconfigurations 1511 1512If you update the forest and part of the configure script has changed, the 1513build system will force you to re-run `configure`. 1514 1515Most of the time, you will be fine by running `configure` again with the same 1516arguments as the last time, which can easily be performed by `make 1517reconfigure`. To simplify this, you can use the `CONF_CHECK` make control 1518variable, either as `make CONF_CHECK=auto`, or by setting an environment 1519variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc` 1520file, `make` will always run `reconfigure` automatically whenever the configure 1521script has changed. 1522 1523You can also use `CONF_CHECK=ignore` to skip the check for a needed configure 1524update. This might speed up the build, but comes at the risk of an incorrect 1525build result. This is only recommended if you know what you're doing. 1526 1527From time to time, you will also need to modify the command line to `configure` 1528due to changes. Use `make print-configure` to show the command line used for 1529your current configuration. 1530 1531### Using Fine-Grained Make Targets 1532 1533The default behavior for make is to create consistent and correct output, at 1534the expense of build speed, if necessary. 1535 1536If you are prepared to take some risk of an incorrect build, and know enough of 1537the system to understand how things build and interact, you can speed up the 1538build process considerably by instructing make to only build a portion of the 1539product. 1540 1541#### Building Individual Modules 1542 1543The safe way to use fine-grained make targets is to use the module specific 1544make targets. All source code in the JDK is organized so it belongs to a 1545module, e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific 1546module, by giving it as make target: `make jdk.jdwp.agent`. If the specified 1547module depends on other modules (e.g. `java.base`), those modules will be built 1548first. 1549 1550You can also specify a set of modules, just as you can always specify a set of 1551make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi 1552jdk.crypto.ucrypto` 1553 1554#### Building Individual Module Phases 1555 1556The build process for each module is divided into separate phases. Not all 1557modules need all phases. Which are needed depends on what kind of source code 1558and other artifact the module consists of. The phases are: 1559 1560 * `gensrc` (Generate source code to compile) 1561 * `gendata` (Generate non-source code artifacts) 1562 * `copy` (Copy resource artifacts) 1563 * `java` (Compile Java code) 1564 * `launchers` (Compile native executables) 1565 * `libs` (Compile native libraries) 1566 * `rmic` (Run the `rmic` tool) 1567 1568You can build only a single phase for a module by using the notation 1569`$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`, 1570use `make java.base-gensrc`. 1571 1572Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if 1573present). Make will build all needed prerequisites before building the 1574requested phase. 1575 1576#### Skipping the Dependency Check 1577 1578When using an iterative development style with frequent quick rebuilds, the 1579dependency check made by make can take up a significant portion of the time 1580spent on the rebuild. In such cases, it can be useful to bypass the dependency 1581check in make. 1582 1583> **Note that if used incorrectly, this can lead to a broken build!** 1584 1585To achieve this, append `-only` to the build target. For instance, `make 1586jdk.jdwp.agent-java-only` will *only* build the `java` phase of the 1587`jdk.jdwp.agent` module. If the required dependencies are not present, the 1588build can fail. On the other hand, the execution time measures in milliseconds. 1589 1590A useful pattern is to build the first time normally (e.g. `make 1591jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target. 1592 1593#### Rebuilding Part of java.base (JDK\_FILTER) 1594 1595If you are modifying files in `java.base`, which is the by far largest module 1596in the JDK, then you need to rebuild all those files whenever a single file has 1597changed. (This inefficiency will hopefully be addressed in JDK 10.) 1598 1599As a hack, you can use the make control variable `JDK_FILTER` to specify a 1600pattern that will be used to limit the set of files being recompiled. For 1601instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods, 1602`make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation 1603to files in the `javax.crypto` package. 1604 1605## Understanding the Build System 1606 1607This section will give you a more technical description on the details of the 1608build system. 1609 1610### Configurations 1611 1612The build system expects to find one or more configuration. These are 1613technically defined by the `spec.gmk` in a subdirectory to the `build` 1614subdirectory. The `spec.gmk` file is generated by `configure`, and contains in 1615principle the configuration (directly or by files included by `spec.gmk`). 1616 1617You can, in fact, select a configuration to build by pointing to the `spec.gmk` 1618file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`. 1619While this is not the recommended way to call `make` as a user, it is what is 1620used under the hood by the build system. 1621 1622### Build Output Structure 1623 1624The build output for a configuration will end up in `build/<configuration 1625name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory 1626contains the following important directories: 1627 1628``` 1629buildtools/ 1630configure-support/ 1631hotspot/ 1632images/ 1633jdk/ 1634make-support/ 1635support/ 1636test-results/ 1637test-support/ 1638``` 1639 1640This is what they are used for: 1641 1642 * `images`: This is the directory were the output of the `*-image` make 1643 targets end up. For instance, `make jdk-image` ends up in `images/jdk`. 1644 1645 * `jdk`: This is the "exploded image". After `make jdk`, you will be able to 1646 launch the newly built JDK by running `$BUILD/jdk/bin/java`. 1647 1648 * `test-results`: This directory contains the results from running tests. 1649 1650 * `support`: This is an area for intermediate files needed during the build, 1651 e.g. generated source code, object files and class files. Some noteworthy 1652 directories in `support` is `gensrc`, which contains the generated source 1653 code, and the `modules_*` directories, which contains the files in a 1654 per-module hierarchy that will later be collapsed into the `jdk` directory 1655 of the exploded image. 1656 1657 * `buildtools`: This is an area for tools compiled for the build platform 1658 that are used during the rest of the build. 1659 1660 * `hotspot`: This is an area for intermediate files needed when building 1661 hotspot. 1662 1663 * `configure-support`, `make-support` and `test-support`: These directories 1664 contain files that are needed by the build system for `configure`, `make` 1665 and for running tests. 1666 1667### Fixpath 1668 1669Windows path typically look like `C:\User\foo`, while Unix paths look like 1670`/home/foo`. Tools with roots from Unix often experience issues related to this 1671mismatch when running on Windows. 1672 1673In the JDK build, we always use Unix paths internally, and only just before 1674calling a tool that does not understand Unix paths do we convert them to 1675Windows paths. 1676 1677This conversion is done by the `fixpath` tool, which is a small wrapper that 1678modifies unix-style paths to Windows-style paths in command lines. Fixpath is 1679compiled automatically by `configure`. 1680 1681### Native Debug Symbols 1682 1683Native libraries and executables can have debug symbol (and other debug 1684information) associated with them. How this works is very much platform 1685dependent, but a common problem is that debug symbol information takes a lot of 1686disk space, but is rarely needed by the end user. 1687 1688The JDK supports different methods on how to handle debug symbols. The 1689method used is selected by `--with-native-debug-symbols`, and available methods 1690are `none`, `internal`, `external`, `zipped`. 1691 1692 * `none` means that no debug symbols will be generated during the build. 1693 1694 * `internal` means that debug symbols will be generated during the build, and 1695 they will be stored in the generated binary. 1696 1697 * `external` means that debug symbols will be generated during the build, and 1698 after the compilation, they will be moved into a separate `.debuginfo` file. 1699 (This was previously known as FDS, Full Debug Symbols). 1700 1701 * `zipped` is like `external`, but the .debuginfo file will also be zipped 1702 into a `.diz` file. 1703 1704When building for distribution, `zipped` is a good solution. Binaries built 1705with `internal` is suitable for use by developers, since they facilitate 1706debugging, but should be stripped before distributed to end users. 1707 1708### Autoconf Details 1709 1710The `configure` script is based on the autoconf framework, but in some details 1711deviate from a normal autoconf `configure` script. 1712 1713The `configure` script in the top level directory of the JDK is just a thin 1714wrapper that calls `make/autoconf/configure`. This in turn will run `autoconf` 1715to create the runnable (generated) configure script, as 1716`.build/generated-configure.sh`. Apart from being responsible for the 1717generation of the runnable script, the `configure` script also provides 1718functionality that is not easily expressed in the normal Autoconf framework. As 1719part of this functionality, the generated script is called. 1720 1721The build system will detect if the Autoconf source files have changed, and 1722will trigger a regeneration of the generated script if needed. You can also 1723manually request such an update by `bash configure autogen`. 1724 1725In previous versions of the JDK, the generated script was checked in at 1726`make/autoconf/generated-configure.sh`. This is no longer the case. 1727 1728### Developing the Build System Itself 1729 1730This section contains a few remarks about how to develop for the build system 1731itself. It is not relevant if you are only making changes in the product source 1732code. 1733 1734While technically using `make`, the make source files of the JDK does not 1735resemble most other Makefiles. Instead of listing specific targets and actions 1736(perhaps using patterns), the basic modus operandi is to call a high-level 1737function (or properly, macro) from the API in `make/common`. For instance, to 1738compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module, 1739a call like this would be made: 1740 1741``` 1742$(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \ 1743 SETUP := GENERATE_OLDBYTECODE, \ 1744 SRC := $(TOPDIR)/src/jkd.foo/share/classes, \ 1745 INCLUDES := jdk/internal/foo, \ 1746 BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \ 1747)) 1748``` 1749 1750By encapsulating and expressing the high-level knowledge of *what* should be 1751done, rather than *how* it should be done (as is normal in Makefiles), we can 1752build a much more powerful and flexible build system. 1753 1754Correct dependency tracking is paramount. Sloppy dependency tracking will lead 1755to improper parallelization, or worse, race conditions. 1756 1757To test for/debug race conditions, try running `make JOBS=1` and `make 1758JOBS=100` and see if it makes any difference. (It shouldn't). 1759 1760To compare the output of two different builds and see if, and how, they differ, 1761run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two 1762builds you want to compare. 1763 1764To automatically build two consecutive versions and compare them, use 1765`COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value 1766assignments, like this: 1767``` 1768make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot 1769``` 1770See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`. 1771 1772To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`. 1773Use `JOBS=1` to avoid parallelism. 1774 1775Please check that you adhere to the [Code Conventions for the Build System]( 1776http://openjdk.java.net/groups/build/doc/code-conventions.html) before 1777submitting patches. 1778 1779## Contributing to the JDK 1780 1781So, now you've built your JDK, and made your first patch, and want to 1782contribute it back to the OpenJDK Community. 1783 1784First of all: Thank you! We gladly welcome your contribution. 1785However, please bear in mind that the JDK is a massive project, and we must ask 1786you to follow our rules and guidelines to be able to accept your contribution. 1787 1788The official place to start is the ['How to contribute' page]( 1789http://openjdk.java.net/contribute/). There is also an official (but somewhat 1790outdated and skimpy on details) [Developer's Guide]( 1791http://openjdk.java.net/guide/). 1792 1793If this seems overwhelming to you, the Adoption Group is there to help you! A 1794good place to start is their ['New Contributor' page]( 1795https://wiki.openjdk.java.net/display/Adoption/New+Contributor), or start 1796reading the comprehensive [Getting Started Kit]( 1797https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The 1798Adoption Group will also happily answer any questions you have about 1799contributing. Contact them by [mail]( 1800http://mail.openjdk.java.net/mailman/listinfo/adoption-discuss) or [IRC]( 1801http://openjdk.java.net/irc/). 1802 1803--- 1804# Override styles from the base CSS file that are not ideal for this document. 1805header-includes: 1806 - '<style type="text/css">pre, code, tt { color: #1d6ae5; }</style>' 1807--- 1808