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 Mercurial (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 `hg clone http://hg.openjdk.java.net/jdk/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 Mercurial server](http://hg.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 Mercurial, a good place to start is the [Mercurial Beginner's 56Guide](http://www.mercurial-scm.org/guide). The rest of this document assumes a 57working knowledge of Mercurial. 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 * Clone the JDK repository using the Cygwin command line `hg` client 93 as instructed in this document. That is, do *not* use another Mercurial 94 client such as TortoiseHg. 95 96 Failure to follow this procedure might result in hard-to-debug build 97 problems. 98 99## Build Hardware Requirements 100 101The JDK is a massive project, and require machines ranging from decent to 102powerful to be able to build in a reasonable amount of time, or to be able to 103complete a build at all. 104 105We *strongly* recommend usage of an SSD disk for the build, since disk speed is 106one of the limiting factors for build performance. 107 108### Building on x86 109 110At a minimum, a machine with 2-4 cores is advisable, as well as 2-4 GB of RAM. 111(The more cores to use, the more memory you need.) At least 6 GB of free disk 112space is required (8 GB minimum for building on Solaris). 113 114Even for 32-bit builds, it is recommended to use a 64-bit build machine, and 115instead create a 32-bit target using `--with-target-bits=32`. 116 117### Building on sparc 118 119At a minimum, a machine with 4 cores is advisable, as well as 4 GB of RAM. (The 120more cores to use, the more memory you need.) At least 8 GB of free disk space 121is required. 122 123Note: The sparc port is deprecated. 124 125### Building on aarch64 126 127At a minimum, a machine with 8 cores is advisable, as well as 8 GB of RAM. 128(The more cores to use, the more memory you need.) At least 6 GB of free disk 129space is required. 130 131If you do not have access to sufficiently powerful hardware, it is also 132possible to use [cross-compiling](#cross-compiling). 133 134### Building on 32-bit arm 135 136This is not recommended. Instead, see the section on [Cross-compiling]( 137#cross-compiling). 138 139## Operating System Requirements 140 141The mainline JDK project supports Linux, Solaris, macOS, AIX and Windows. 142Support for other operating system, e.g. BSD, exists in separate "port" 143projects. 144 145In general, the JDK can be built on a wide range of versions of these operating 146systems, but the further you deviate from what is tested on a daily basis, the 147more likely you are to run into problems. 148 149This table lists the OS versions used by Oracle when building the JDK. Such 150information is always subject to change, but this table is up to date at the 151time of writing. 152 153 Operating system Vendor/version used 154 ----------------- ------------------------------------------------------- 155 Linux Oracle Enterprise Linux 6.4 / 7.6 156 Solaris Solaris 11.3 SRU 20 157 macOS Mac OS X 10.13 (High Sierra) 158 Windows Windows Server 2012 R2 159 160The double version numbers for Linux and Solaris are due to the hybrid model 161used at Oracle, where header files and external libraries from an older version 162are used when building on a more modern version of the OS. 163 164The Build Group has a wiki page with [Supported Build Platforms]( 165https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms). From 166time to time, this is updated by contributors to list successes or failures of 167building on different platforms. 168 169### Windows 170 171Windows XP is not a supported platform, but all newer Windows should be able to 172build the JDK. 173 174On Windows, it is important that you pay attention to the instructions in the 175[Special Considerations](#special-considerations). 176 177Windows is the only non-POSIX OS supported by the JDK, and as such, requires 178some extra care. A POSIX support layer is required to build on Windows. 179Currently, the only supported such layers are Cygwin and Windows Subsystem for 180Linux (WSL). (Msys is no longer supported due to a too old bash; msys2 would 181likely be possible to support in a future version but that would require effort 182to implement.) 183 184Internally in the build system, all paths are represented as Unix-style paths, 185e.g. `/cygdrive/c/hg/jdk9/Makefile` rather than `C:\hg\jdk9\Makefile`. This 186rule also applies to input to the build system, e.g. in arguments to 187`configure`. So, use `--with-msvcr-dll=/cygdrive/c/msvcr100.dll` rather than 188`--with-msvcr-dll=c:\msvcr100.dll`. For details on this conversion, see the section 189on [Fixpath](#fixpath). 190 191#### Cygwin 192 193A functioning [Cygwin](http://www.cygwin.com/) environment is required for 194building the JDK on Windows. If you have a 64-bit OS, we strongly recommend 195using the 64-bit version of Cygwin. 196 197**Note:** Cygwin has a model of continuously updating all packages without any 198easy way to install or revert to a specific version of a package. This means 199that whenever you add or update a package in Cygwin, you might (inadvertently) 200update tools that are used by the JDK build process, and that can cause 201unexpected build problems. 202 203The JDK requires GNU Make 4.0 or greater in Cygwin. This is usually not a 204problem, since Cygwin currently only distributes GNU Make at a version above 2054.0. 206 207Apart from the basic Cygwin installation, the following packages must also be 208installed: 209 210 * `autoconf` 211 * `make` 212 * `zip` 213 * `unzip` 214 215Often, you can install these packages using the following command line: 216``` 217<path to Cygwin setup>/setup-x86_64 -q -P autoconf -P make -P unzip -P zip 218``` 219 220Unfortunately, Cygwin can be unreliable in certain circumstances. If you 221experience build tool crashes or strange issues when building on Windows, 222please check the Cygwin FAQ on the ["BLODA" list]( 223https://cygwin.com/faq/faq.html#faq.using.bloda) and the section on [fork() 224failures](https://cygwin.com/faq/faq.html#faq.using.fixing-fork-failures). 225 226#### Windows Subsystem for Linux (WSL) 227 228Windows 10 1809 or newer is supported due to a dependency on the wslpath utility 229and support for environment variable sharing through WSLENV. Version 1803 can 230work but intermittent build failures have been observed. 231 232It's possible to build both Windows and Linux binaries from WSL. To build 233Windows binaries, you must use a Windows boot JDK (located in a 234Windows-accessible directory). To build Linux binaries, you must use a Linux 235boot JDK. The default behavior is to build for Windows. To build for Linux, pass 236`--build=x86_64-unknown-linux-gnu --host=x86_64-unknown-linux-gnu` to 237`configure`. 238 239If building Windows binaries, the source code must be located in a Windows- 240accessible directory. This is because Windows executables (such as Visual Studio 241and the boot JDK) must be able to access the source code. Also, the drive where 242the source is stored must be mounted as case-insensitive by changing either 243/etc/fstab or /etc/wsl.conf in WSL. Individual directories may be corrected 244using the fsutil tool in case the source was cloned before changing the mount 245options. 246 247Note that while it's possible to build on WSL, testing is still not fully 248supported. 249 250### Solaris 251 252See `make/devkit/solaris11.1-package-list.txt` for a list of recommended 253packages to install when building on Solaris. The versions specified in this 254list is the versions used by the daily builds at Oracle, and is likely to work 255properly. 256 257Older versions of Solaris shipped a broken version of `objcopy`. At least 258version 2.21.1 is needed, which is provided by Solaris 11 Update 1. Objcopy is 259needed if you want to have external debug symbols. Please make sure you are 260using at least version 2.21.1 of objcopy, or that you disable external debug 261symbols. 262 263Note: The Solaris port is deprecated. 264 265### macOS 266 267Apple is using a quite aggressive scheme of pushing OS updates, and coupling 268these updates with required updates of Xcode. Unfortunately, this makes it 269difficult for a project such as the JDK to keep pace with a continuously updated 270machine running macOS. See the section on [Apple Xcode](#apple-xcode) on some 271strategies to deal with this. 272 273It is recommended that you use at least Mac OS X 10.13 (High Sierra). At the time 274of writing, the JDK has been successfully compiled on macOS 10.12 (Sierra). 275 276The standard macOS environment contains the basic tooling needed to build, but 277for external libraries a package manager is recommended. The JDK uses 278[homebrew](https://brew.sh/) in the examples, but feel free to use whatever 279manager you want (or none). 280 281### Linux 282 283It is often not much problem to build the JDK on Linux. The only general advice 284is to try to use the compilers, external libraries and header files as provided 285by your distribution. 286 287The basic tooling is provided as part of the core operating system, but you 288will most likely need to install developer packages. 289 290For apt-based distributions (Debian, Ubuntu, etc), try this: 291``` 292sudo apt-get install build-essential 293``` 294 295For rpm-based distributions (Fedora, Red Hat, etc), try this: 296``` 297sudo yum groupinstall "Development Tools" 298``` 299 300### AIX 301 302Please consult the AIX section of the [Supported Build Platforms]( 303https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms) OpenJDK 304Build Wiki page for details about which versions of AIX are supported. 305 306## Native Compiler (Toolchain) Requirements 307 308Large portions of the JDK consists of native code, that needs to be compiled to 309be able to run on the target platform. In theory, toolchain and operating 310system should be independent factors, but in practice there's more or less a 311one-to-one correlation between target operating system and toolchain. 312 313 Operating system Supported toolchain 314 ------------------ ------------------------- 315 Linux gcc, clang 316 macOS Apple Xcode (using clang) 317 Solaris Oracle Solaris Studio 318 AIX IBM XL C/C++ 319 Windows Microsoft Visual Studio 320 321Please see the individual sections on the toolchains for version 322recommendations. As a reference, these versions of the toolchains are used, at 323the time of writing, by Oracle for the daily builds of the JDK. It should be 324possible to compile the JDK with both older and newer versions, but the closer 325you stay to this list, the more likely you are to compile successfully without 326issues. 327 328 Operating system Toolchain version 329 ------------------ ------------------------------------------------------- 330 Linux gcc 8.3.0 331 macOS Apple Xcode 10.1 (using clang 10.0.0) 332 Solaris Oracle Solaris Studio 12.6 (with compiler version 5.15) 333 Windows Microsoft Visual Studio 2017 update 15.9.16 334 335All compilers are expected to be able to compile to the C99 language standard, 336as some C99 features are used in the source code. Microsoft Visual Studio 337doesn't fully support C99 so in practice shared code is limited to using C99 338features that it does support. 339 340### gcc 341 342The minimum accepted version of gcc is 4.8. Older versions will generate a warning 343by `configure` and are unlikely to work. 344 345The JDK is currently known to be able to compile with at least version 8.3 of 346gcc. 347 348In general, any version between these two should be usable. 349 350### clang 351 352The minimum accepted version of clang is 3.2. Older versions will not be 353accepted by `configure`. 354 355To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`. 356 357### Apple Xcode 358 359The oldest supported version of Xcode is 8. 360 361You will need the Xcode command lines developers tools to be able to build 362the JDK. (Actually, *only* the command lines tools are needed, not the IDE.) 363The simplest way to install these is to run: 364``` 365xcode-select --install 366``` 367 368It is advisable to keep an older version of Xcode for building the JDK when 369updating Xcode. This [blog page]( 370http://iosdevelopertips.com/xcode/install-multiple-versions-of-xcode.html) has 371good suggestions on managing multiple Xcode versions. To use a specific version 372of Xcode, use `xcode-select -s` before running `configure`, or use 373`--with-toolchain-path` to point to the version of Xcode to use, e.g. 374`configure --with-toolchain-path=/Applications/Xcode8.app/Contents/Developer/usr/bin` 375 376If you have recently (inadvertently) updated your OS and/or Xcode version, and 377the JDK can no longer be built, please see the section on [Problems with the 378Build Environment](#problems-with-the-build-environment), and [Getting 379Help](#getting-help) to find out if there are any recent, non-merged patches 380available for this update. 381 382### Oracle Solaris Studio 383 384The minimum accepted version of the Solaris Studio compilers is 5.13 385(corresponding to Solaris Studio 12.4). Older versions will not be accepted by 386configure. 387 388The Solaris Studio installation should contain at least these packages: 389 390 Package Version 391 -------------------------------------------------- ------------- 392 developer/solarisstudio-124/backend 12.4-1.0.6.0 393 developer/solarisstudio-124/c++ 12.4-1.0.10.0 394 developer/solarisstudio-124/cc 12.4-1.0.4.0 395 developer/solarisstudio-124/library/c++-libs 12.4-1.0.10.0 396 developer/solarisstudio-124/library/math-libs 12.4-1.0.0.1 397 developer/solarisstudio-124/library/studio-gccrt 12.4-1.0.0.1 398 developer/solarisstudio-124/studio-common 12.4-1.0.0.1 399 developer/solarisstudio-124/studio-ja 12.4-1.0.0.1 400 developer/solarisstudio-124/studio-legal 12.4-1.0.0.1 401 developer/solarisstudio-124/studio-zhCN 12.4-1.0.0.1 402 403Compiling with Solaris Studio can sometimes be finicky. This is the exact 404version used by Oracle, which worked correctly at the time of writing: 405``` 406$ cc -V 407cc: Sun C 5.13 SunOS_i386 2014/10/20 408$ CC -V 409CC: Sun C++ 5.13 SunOS_i386 151846-10 2015/10/30 410``` 411 412### Microsoft Visual Studio 413 414The minimum accepted version of Visual Studio is 2010. Older versions will not 415be accepted by `configure`. The maximum accepted version of Visual Studio is 4162019. Versions older than 2017 are unlikely to continue working for long. 417 418If you have multiple versions of Visual Studio installed, `configure` will by 419default pick the latest. You can request a specific version to be used by 420setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2015`. 421 422If you get `LINK: fatal error LNK1123: failure during conversion to COFF: file 423invalid` when building using Visual Studio 2010, you have encountered 424[KB2757355](http://support.microsoft.com/kb/2757355), a bug triggered by a 425specific installation order. However, the solution suggested by the KB article 426does not always resolve the problem. See [this stackoverflow discussion]( 427https://stackoverflow.com/questions/10888391) for other suggestions. 428 429### IBM XL C/C++ 430 431Please consult the AIX section of the [Supported Build Platforms]( 432https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms) OpenJDK 433Build Wiki page for details about which versions of XLC are supported. 434 435 436## Boot JDK Requirements 437 438Paradoxically, building the JDK requires a pre-existing JDK. This is called the 439"boot JDK". The boot JDK does not, however, have to be a JDK built directly from 440the source code available in the OpenJDK Community. If you are porting the JDK 441to a new platform, chances are that there already exists another JDK for that 442platform that is usable as boot JDK. 443 444The rule of thumb is that the boot JDK for building JDK major version *N* 445should be a JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be 446suitable as boot JDK. However, the JDK should be able to "build itself", so an 447up-to-date build of the current JDK source is an acceptable alternative. If 448you are following the *N-1* rule, make sure you've got the latest update 449version, since JDK 8 GA might not be able to build JDK 9 on all platforms. 450 451Early in the release cycle, version *N-1* may not yet have been released. In 452that case, the preferred boot JDK will be version *N-2* until version *N-1* 453is available. 454 455If the boot JDK is not automatically detected, or the wrong JDK is picked, use 456`--with-boot-jdk` to point to the JDK to use. 457 458### Getting JDK binaries 459 460JDK binaries for Linux, Windows and macOS can be downloaded from 461[jdk.java.net](http://jdk.java.net). An alternative is to download the 462[Oracle JDK](http://www.oracle.com/technetwork/java/javase/downloads). Another 463is the [Adopt OpenJDK Project](https://adoptopenjdk.net/), which publishes 464experimental prebuilt binaries for various platforms. 465 466On Linux you can also get a JDK from the Linux distribution. On apt-based 467distros (like Debian and Ubuntu), `sudo apt-get install openjdk-<VERSION>-jdk` 468is typically enough to install a JDK \<VERSION\>. On rpm-based distros (like 469Fedora and Red Hat), try `sudo yum install java-<VERSION>-openjdk-devel`. 470 471## External Library Requirements 472 473Different platforms require different external libraries. In general, libraries 474are not optional - that is, they are either required or not used. 475 476If a required library is not detected by `configure`, you need to provide the 477path to it. There are two forms of the `configure` arguments to point to an 478external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to 479include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise, 480but require the include files and library files to reside in a default 481hierarchy under this directory. In most cases, it works fine. 482 483As a fallback, the second version allows you to point to the include directory 484and the lib directory separately. 485 486### FreeType 487 488FreeType2 from [The FreeType Project](http://www.freetype.org/) is not required 489on any platform. The exception is on Unix-based platforms when configuring such 490that the build artifacts will reference a system installed library, 491rather than bundling the JDK's own copy. 492 493 * To install on an apt-based Linux, try running `sudo apt-get install 494 libfreetype6-dev`. 495 * To install on an rpm-based Linux, try running `sudo yum install 496 freetype-devel`. 497 * To install on Solaris, try running `pkg install system/library/freetype-2`. 498 499Use `--with-freetype-include=<path>` and `--with-freetype-lib=<path>` 500if `configure` does not automatically locate the platform FreeType files. 501 502### CUPS 503 504CUPS, [Common UNIX Printing System](http://www.cups.org) header files are 505required on all platforms, except Windows. Often these files are provided by 506your operating system. 507 508 * To install on an apt-based Linux, try running `sudo apt-get install 509 libcups2-dev`. 510 * To install on an rpm-based Linux, try running `sudo yum install 511 cups-devel`. 512 * To install on Solaris, try running `pkg install print/cups`. 513 514Use `--with-cups=<path>` if `configure` does not properly locate your CUPS 515files. 516 517### X11 518 519Certain [X11](http://www.x.org/) libraries and include files are required on 520Linux and Solaris. 521 522 * To install on an apt-based Linux, try running `sudo apt-get install 523 libx11-dev libxext-dev libxrender-dev libxrandr-dev libxtst-dev libxt-dev`. 524 * To install on an rpm-based Linux, try running `sudo yum install 525 libXtst-devel libXt-devel libXrender-devel libXrandr-devel libXi-devel`. 526 * To install on Solaris, try running `pkg install x11/header/x11-protocols 527 x11/library/libice x11/library/libpthread-stubs x11/library/libsm 528 x11/library/libx11 x11/library/libxau x11/library/libxcb 529 x11/library/libxdmcp x11/library/libxevie x11/library/libxext 530 x11/library/libxrender x11/library/libxrandr x11/library/libxscrnsaver 531 x11/library/libxtst x11/library/toolkit/libxt`. 532 533Use `--with-x=<path>` if `configure` does not properly locate your X11 files. 534 535### ALSA 536 537ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is 538required on Linux. At least version 0.9.1 of ALSA is required. 539 540 * To install on an apt-based Linux, try running `sudo apt-get install 541 libasound2-dev`. 542 * To install on an rpm-based Linux, try running `sudo yum install 543 alsa-lib-devel`. 544 545Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA 546files. 547 548### libffi 549 550libffi, the [Portable Foreign Function Interface Library]( 551http://sourceware.org/libffi) is required when building the Zero version of 552Hotspot. 553 554 * To install on an apt-based Linux, try running `sudo apt-get install 555 libffi-dev`. 556 * To install on an rpm-based Linux, try running `sudo yum install 557 libffi-devel`. 558 559Use `--with-libffi=<path>` if `configure` does not properly locate your libffi 560files. 561 562## Build Tools Requirements 563 564### Autoconf 565 566The JDK requires [Autoconf](http://www.gnu.org/software/autoconf) on all 567platforms. At least version 2.69 is required. 568 569 * To install on an apt-based Linux, try running `sudo apt-get install 570 autoconf`. 571 * To install on an rpm-based Linux, try running `sudo yum install 572 autoconf`. 573 * To install on macOS, try running `brew install autoconf`. 574 * To install on Windows, try running `<path to Cygwin setup>/setup-x86_64 -q 575 -P autoconf`. 576 577If `configure` has problems locating your installation of autoconf, you can 578specify it using the `AUTOCONF` environment variable, like this: 579 580``` 581AUTOCONF=<path to autoconf> configure ... 582``` 583 584### GNU Make 585 586The JDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors 587of make are supported. 588 589At least version 3.81 of GNU Make must be used. For distributions supporting 590GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful 591functionality to handle parallel building (supported by `--with-output-sync`) 592and speed and stability improvements. 593 594Note that `configure` locates and verifies a properly functioning version of 595`make` and stores the path to this `make` binary in the configuration. If you 596start a build using `make` on the command line, you will be using the version 597of make found first in your `PATH`, and not necessarily the one stored in the 598configuration. This initial make will be used as "bootstrap make", and in a 599second stage, the make located by `configure` will be called. Normally, this 600will present no issues, but if you have a very old `make`, or a non-GNU Make 601`make` in your path, this might cause issues. 602 603If you want to override the default make found by `configure`, use the `MAKE` 604configure variable, e.g. `configure MAKE=/opt/gnu/make`. 605 606On Solaris, it is common to call the GNU version of make by using `gmake`. 607 608### GNU Bash 609 610The JDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells 611are supported. 612 613At least version 3.2 of GNU Bash must be used. 614 615## Running Configure 616 617To build the JDK, you need a "configuration", which consists of a directory 618where to store the build output, coupled with information about the platform, 619the specific build machine, and choices that affect how the JDK is built. 620 621The configuration is created by the `configure` script. The basic invocation of 622the `configure` script looks like this: 623 624``` 625bash configure [options] 626``` 627 628This will create an output directory containing the configuration and setup an 629area for the build result. This directory typically looks like 630`build/linux-x64-server-release`, but the actual name depends on your specific 631configuration. (It can also be set directly, see [Using Multiple 632Configurations](#using-multiple-configurations)). This directory is referred to 633as `$BUILD` in this documentation. 634 635`configure` will try to figure out what system you are running on and where all 636necessary build components are. If you have all prerequisites for building 637installed, it should find everything. If it fails to detect any component 638automatically, it will exit and inform you about the problem. 639 640Some command line examples: 641 642 * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`: 643 ``` 644 bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32 645 ``` 646 647 * Create a debug build with the `server` JVM and DTrace enabled: 648 ``` 649 bash configure --enable-debug --with-jvm-variants=server --enable-dtrace 650 ``` 651 652### Common Configure Arguments 653 654Here follows some of the most common and important `configure` argument. 655 656To get up-to-date information on *all* available `configure` argument, please 657run: 658``` 659bash configure --help 660``` 661 662(Note that this help text also include general autoconf options, like 663`--dvidir`, that is not relevant to the JDK. To list only JDK-specific 664features, use `bash configure --help=short` instead.) 665 666#### Configure Arguments for Tailoring the Build 667 668 * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand 669 for `--with-debug-level=fastdebug`) 670 * `--with-debug-level=<level>` - Set the debug level, which can be `release`, 671 `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized` 672 is variant of `release` with additional Hotspot debug code. 673 * `--with-native-debug-symbols=<method>` - Specify if and how native debug 674 symbols should be built. Available methods are `none`, `internal`, 675 `external`, `zipped`. Default behavior depends on platform. See [Native 676 Debug Symbols](#native-debug-symbols) for more details. 677 * `--with-version-string=<string>` - Specify the version string this build 678 will be identified with. 679 * `--with-version-<part>=<value>` - A group of options, where `<part>` can be 680 any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use 681 these options to modify just the corresponding part of the version string 682 from the default, or the value provided by `--with-version-string`. 683 * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant 684 (or variants) of Hotspot. Valid variants are: `server`, `client`, 685 `minimal`, `core`, `zero`, `custom`. Note that not all 686 variants are possible to combine in a single build. 687 * `--with-jvm-features=<feature>[,<feature>...]` - Use the specified JVM 688 features when building Hotspot. The list of features will be enabled on top 689 of the default list. For the `custom` JVM variant, this default list is 690 empty. A complete list of available JVM features can be found using `bash 691 configure --help`. 692 * `--with-target-bits=<bits>` - Create a target binary suitable for running 693 on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build 694 platform, instead of doing a full cross-compile. (This is known as a 695 *reduced* build.) 696 697On Linux, BSD and AIX, it is possible to override where Java by default 698searches for runtime/JNI libraries. This can be useful in situations where 699there is a special shared directory for system JNI libraries. This setting 700can in turn be overriden at runtime by setting the `java.library.path` property. 701 702 * `--with-jni-libpath=<path>` - Use the specified path as a default 703 when searching for runtime libraries. 704 705#### Configure Arguments for Native Compilation 706 707 * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources 708 * `--with-sysroot=<path>` - Use this directory as sysroot 709 * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the 710 default path when searching for all kinds of binaries 711 * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when 712 searching for toolchain binaries (compilers etc) 713 * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C 714 files 715 * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++ 716 files 717 * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK 718 libraries 719 720#### Configure Arguments for External Dependencies 721 722 * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK]( 723 #boot-jdk-requirements) 724 * `--with-freetype=<path>` - Set the path to [FreeType](#freetype) 725 * `--with-cups=<path>` - Set the path to [CUPS](#cups) 726 * `--with-x=<path>` - Set the path to [X11](#x11) 727 * `--with-alsa=<path>` - Set the path to [ALSA](#alsa) 728 * `--with-libffi=<path>` - Set the path to [libffi](#libffi) 729 * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests]( 730 #running-tests) 731 732Certain third-party libraries used by the JDK (libjpeg, giflib, libpng, lcms 733and zlib) are included in the JDK repository. The default behavior of the 734JDK build is to use the included ("bundled") versions of libjpeg, giflib, 735libpng and lcms. 736For zlib, the system lib (if present) is used except on Windows and AIX. 737However the bundled libraries may be replaced by an external version. 738To do so, specify `system` as the `<source>` option in these arguments. 739(The default is `bundled`). 740 741 * `--with-libjpeg=<source>` - Use the specified source for libjpeg 742 * `--with-giflib=<source>` - Use the specified source for giflib 743 * `--with-libpng=<source>` - Use the specified source for libpng 744 * `--with-lcms=<source>` - Use the specified source for lcms 745 * `--with-zlib=<source>` - Use the specified source for zlib 746 747On Linux, it is possible to select either static or dynamic linking of the C++ 748runtime. The default is static linking, with dynamic linking as fallback if the 749static library is not found. 750 751 * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic` 752 or `default`) for linking the C++ runtime. 753 754### Configure Control Variables 755 756It is possible to control certain aspects of `configure` by overriding the 757value of `configure` variables, either on the command line or in the 758environment. 759 760Normally, this is **not recommended**. If used improperly, it can lead to a 761broken configuration. Unless you're well versed in the build system, this is 762hard to use properly. Therefore, `configure` will print a warning if this is 763detected. 764 765However, there are a few `configure` variables, known as *control variables* 766that are supposed to be overriden on the command line. These are variables that 767describe the location of tools needed by the build, like `MAKE` or `GREP`. If 768any such variable is specified, `configure` will use that value instead of 769trying to autodetect the tool. For instance, `bash configure 770MAKE=/opt/gnumake4.0/bin/make`. 771 772If a configure argument exists, use that instead, e.g. use `--with-jtreg` 773instead of setting `JTREGEXE`. 774 775Also note that, despite what autoconf claims, setting `CFLAGS` will not 776accomplish anything. Instead use `--with-extra-cflags` (and similar for 777`cxxflags` and `ldflags`). 778 779## Running Make 780 781When you have a proper configuration, all you need to do to build the JDK is to 782run `make`. (But see the warning at [GNU Make](#gnu-make) about running the 783correct version of make.) 784 785When running `make` without any arguments, the default target is used, which is 786the same as running `make default` or `make jdk`. This will build a minimal (or 787roughly minimal) set of compiled output (known as an "exploded image") needed 788for a developer to actually execute the newly built JDK. The idea is that in an 789incremental development fashion, when doing a normal make, you should only 790spend time recompiling what's changed (making it purely incremental) and only 791do the work that's needed to actually run and test your code. 792 793The output of the exploded image resides in `$BUILD/jdk`. You can test the 794newly built JDK like this: `$BUILD/jdk/bin/java -version`. 795 796### Common Make Targets 797 798Apart from the default target, here are some common make targets: 799 800 * `hotspot` - Build all of hotspot (but only hotspot) 801 * `hotspot-<variant>` - Build just the specified jvm variant 802 * `images` or `product-images` - Build the JDK image 803 * `docs` or `docs-image` - Build the documentation image 804 * `test-image` - Build the test image 805 * `all` or `all-images` - Build all images (product, docs and test) 806 * `bootcycle-images` - Build images twice, second time with newly built JDK 807 (good for testing) 808 * `clean` - Remove all files generated by make, but not those generated by 809 configure 810 * `dist-clean` - Remove all files, including configuration 811 812Run `make help` to get an up-to-date list of important make targets and make 813control variables. 814 815It is possible to build just a single module, a single phase, or a single phase 816of a single module, by creating make targets according to these followin 817patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`, 818`launchers`, `libs` or `rmic`. See [Using Fine-Grained Make Targets]( 819#using-fine-grained-make-targets) for more details about this functionality. 820 821 * `<phase>` - Build the specified phase and everything it depends on 822 * `<module>` - Build the specified module and everything it depends on 823 * `<module>-<phase>` - Compile the specified phase for the specified module 824 and everything it depends on 825 826Similarly, it is possible to clean just a part of the build by creating make 827targets according to these patterns: 828 829 * `clean-<outputdir>` - Remove the subdir in the output dir with the name 830 * `clean-<phase>` - Remove all build results related to a certain build 831 phase 832 * `clean-<module>` - Remove all build results related to a certain module 833 * `clean-<module>-<phase>` - Remove all build results related to a certain 834 module and phase 835 836### Make Control Variables 837 838It is possible to control `make` behavior by overriding the value of `make` 839variables, either on the command line or in the environment. 840 841Normally, this is **not recommended**. If used improperly, it can lead to a 842broken build. Unless you're well versed in the build system, this is hard to 843use properly. Therefore, `make` will print a warning if this is detected. 844 845However, there are a few `make` variables, known as *control variables* that 846are supposed to be overriden on the command line. These make up the "make time" 847configuration, as opposed to the "configure time" configuration. 848 849#### General Make Control Variables 850 851 * `JOBS` - Specify the number of jobs to build with. See [Build 852 Performance](#build-performance). 853 * `LOG` - Specify the logging level and functionality. See [Checking the 854 Build Log File](#checking-the-build-log-file) 855 * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using 856 Multiple Configurations](#using-multiple-configurations) 857 858#### Test Make Control Variables 859 860These make control variables only make sense when running tests. Please see 861[Testing the JDK](testing.html) for details. 862 863 * `TEST` 864 * `TEST_JOBS` 865 * `JTREG` 866 * `GTEST` 867 868#### Advanced Make Control Variables 869 870These advanced make control variables can be potentially unsafe. See [Hints and 871Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and 872[Understanding the Build System](#understanding-the-build-system) for details. 873 874 * `SPEC` 875 * `CONF_CHECK` 876 * `COMPARE_BUILD` 877 * `JDK_FILTER` 878 * `SPEC_FILTER` 879 880## Running Tests 881 882Most of the JDK tests are using the [JTReg](http://openjdk.java.net/jtreg) 883test framework. Make sure that your configuration knows where to find your 884installation of JTReg. If this is not picked up automatically, use the 885`--with-jtreg=<path to jtreg home>` option to point to the JTReg framework. 886Note that this option should point to the JTReg home, i.e. the top directory, 887containing `lib/jtreg.jar` etc. 888 889The [Adoption Group](https://wiki.openjdk.java.net/display/Adoption) provides 890recent builds of jtreg [here]( 891https://adopt-openjdk.ci.cloudbees.com/job/jtreg/lastSuccessfulBuild/artifact). 892Download the latest `.tar.gz` file, unpack it, and point `--with-jtreg` to the 893`jtreg` directory that you just unpacked. 894 895To execute the most basic tests (tier 1), use: 896``` 897make run-test-tier1 898``` 899 900For more details on how to run tests, please see the [Testing 901the JDK](testing.html) document. 902 903## Cross-compiling 904 905Cross-compiling means using one platform (the *build* platform) to generate 906output that can ran on another platform (the *target* platform). 907 908The typical reason for cross-compiling is that the build is performed on a more 909powerful desktop computer, but the resulting binaries will be able to run on a 910different, typically low-performing system. Most of the complications that 911arise when building for embedded is due to this separation of *build* and 912*target* systems. 913 914This requires a more complex setup and build procedure. This section assumes 915you are familiar with cross-compiling in general, and will only deal with the 916particularities of cross-compiling the JDK. If you are new to cross-compiling, 917please see the [external links at Wikipedia]( 918https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start 919on reading materials. 920 921Cross-compiling the JDK requires you to be able to build both for the build 922platform and for the target platform. The reason for the former is that we need 923to build and execute tools during the build process, both native tools and Java 924tools. 925 926If all you want to do is to compile a 32-bit version, for the same OS, on a 92764-bit machine, consider using `--with-target-bits=32` instead of doing a 928full-blown cross-compilation. (While this surely is possible, it's a lot more 929work and will take much longer to build.) 930 931### Cross compiling the easy way with OpenJDK devkits 932 933The OpenJDK build system provides out-of-the box support for creating and using 934so called devkits. A `devkit` is basically a collection of a cross-compiling 935toolchain and a sysroot environment which can easily be used together with the 936`--with-devkit` configure option to cross compile the OpenJDK. On Linux/x86_64, 937the following command: 938``` 939bash configure --with-devkit=<devkit-path> --openjdk-target=ppc64-linux-gnu && make 940``` 941 942will configure and build OpenJDK for Linux/ppc64 assuming that `<devkit-path>` 943points to a Linux/x86_64 to Linux/ppc64 devkit. 944 945Devkits can be created from the `make/devkit` directory by executing: 946``` 947make [ TARGETS="<TARGET_TRIPLET>+" ] [ BASE_OS=<OS> ] [ BASE_OS_VERSION=<VER> ] 948``` 949 950where `TARGETS` contains one or more `TARGET_TRIPLET`s of the form 951described in [section 3.4 of the GNU Autobook]( 952https://sourceware.org/autobook/autobook/autobook_17.html). If no 953targets are given, a native toolchain for the current platform will be 954created. Currently, at least the following targets are known to work: 955 956 Supported devkit targets 957 ------------------------- 958 x86_64-linux-gnu 959 aarch64-linux-gnu 960 arm-linux-gnueabihf 961 ppc64-linux-gnu 962 ppc64le-linux-gnu 963 s390x-linux-gnu 964 965`BASE_OS` must be one of "OEL6" for Oracle Enterprise Linux 6 or 966"Fedora" (if not specified "OEL6" will be the default). If the base OS 967is "Fedora" the corresponding Fedora release can be specified with the 968help of the `BASE_OS_VERSION` option (with "27" as default version). 969If the build is successful, the new devkits can be found in the 970`build/devkit/result` subdirectory: 971``` 972cd make/devkit 973make TARGETS="ppc64le-linux-gnu aarch64-linux-gnu" BASE_OS=Fedora BASE_OS_VERSION=21 974ls -1 ../../build/devkit/result/ 975x86_64-linux-gnu-to-aarch64-linux-gnu 976x86_64-linux-gnu-to-ppc64le-linux-gnu 977``` 978 979Notice that devkits are not only useful for targeting different build 980platforms. Because they contain the full build dependencies for a 981system (i.e. compiler and root file system), they can easily be used 982to build well-known, reliable and reproducible build environments. You 983can for example create and use a devkit with GCC 7.3 and a Fedora 12 984sysroot environment (with glibc 2.11) on Ubuntu 14.04 (which doesn't 985have GCC 7.3 by default) to produce OpenJDK binaries which will run on 986all Linux systems with runtime libraries newer than the ones from 987Fedora 12 (e.g. Ubuntu 16.04, SLES 11 or RHEL 6). 988 989### Boot JDK and Build JDK 990 991When cross-compiling, make sure you use a boot JDK that runs on the *build* 992system, and not on the *target* system. 993 994To be able to build, we need a "Build JDK", which is a JDK built from the 995current sources (that is, the same as the end result of the entire build 996process), but able to run on the *build* system, and not the *target* system. 997(In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when 998building JDK 9.) 999 1000The build process will create a minimal Build JDK for you, as part of building. 1001To speed up the build, you can use `--with-build-jdk` to `configure` to point 1002to a pre-built Build JDK. Please note that the build result is unpredictable, 1003and can possibly break in subtle ways, if the Build JDK does not **exactly** 1004match the current sources. 1005 1006### Specifying the Target Platform 1007 1008You *must* specify the target platform when cross-compiling. Doing so will also 1009automatically turn the build into a cross-compiling mode. The simplest way to 1010do this is to use the `--openjdk-target` argument, e.g. 1011`--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`. 1012This will automatically set the `--build`, `--host` and `--target` options for 1013autoconf, which can otherwise be confusing. (In autoconf terminology, the 1014"target" is known as "host", and "target" is used for building a Canadian 1015cross-compiler.) 1016 1017### Toolchain Considerations 1018 1019You will need two copies of your toolchain, one which generates output that can 1020run on the target system (the normal, or *target*, toolchain), and one that 1021generates output that can run on the build system (the *build* toolchain). Note 1022that cross-compiling is only supported for gcc at the time being. The gcc 1023standard is to prefix cross-compiling toolchains with the target denominator. 1024If you follow this standard, `configure` is likely to pick up the toolchain 1025correctly. 1026 1027The *build* toolchain will be autodetected just the same way the normal 1028*build*/*target* toolchain will be autodetected when not cross-compiling. If 1029this is not what you want, or if the autodetection fails, you can specify a 1030devkit containing the *build* toolchain using `--with-build-devkit` to 1031`configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments. 1032 1033It is often helpful to locate the cross-compilation tools, headers and 1034libraries in a separate directory, outside the normal path, and point out that 1035directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and 1036appending the directory when searching for cross-compilations tools 1037(`--with-toolchain-path`). As a compact form, you can also use `--with-devkit` 1038to point to a single directory, if it is correctly setup. (See `basics.m4` for 1039details.) 1040 1041If you are unsure what toolchain and versions to use, these have been proved 1042working at the time of writing: 1043 1044 * [aarch64]( 1045https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-linux-gnu-4.8-2013.11_linux.tar.xz) 1046 * [arm 32-bit hardware floating point]( 1047https://launchpad.net/linaro-toolchain-unsupported/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux.tar.bz2) 1048 1049### Native Libraries 1050 1051You will need copies of external native libraries for the *target* system, 1052present on the *build* machine while building. 1053 1054Take care not to replace the *build* system's version of these libraries by 1055mistake, since that can render the *build* machine unusable. 1056 1057Make sure that the libraries you point to (ALSA, X11, etc) are for the 1058*target*, not the *build*, platform. 1059 1060#### ALSA 1061 1062You will need alsa libraries suitable for your *target* system. For most cases, 1063using Debian's pre-built libraries work fine. 1064 1065Note that alsa is needed even if you only want to build a headless JDK. 1066 1067 * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and 1068 search for the `libasound2` and `libasound2-dev` packages for your *target* 1069 system. Download them to /tmp. 1070 1071 * Install the libraries into the cross-compilation toolchain. For instance: 1072``` 1073cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc 1074dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb . 1075dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb . 1076``` 1077 1078 * If alsa is not properly detected by `configure`, you can point it out by 1079 `--with-alsa`. 1080 1081#### X11 1082 1083You will need X11 libraries suitable for your *target* system. For most cases, 1084using Debian's pre-built libraries work fine. 1085 1086Note that X11 is needed even if you only want to build a headless JDK. 1087 1088 * Go to [Debian Package Search](https://www.debian.org/distrib/packages), 1089 search for the following packages for your *target* system, and download them 1090 to /tmp/target-x11: 1091 * libxi 1092 * libxi-dev 1093 * x11proto-core-dev 1094 * x11proto-input-dev 1095 * x11proto-kb-dev 1096 * x11proto-render-dev 1097 * x11proto-xext-dev 1098 * libice-dev 1099 * libxrender 1100 * libxrender-dev 1101 * libxrandr-dev 1102 * libsm-dev 1103 * libxt-dev 1104 * libx11 1105 * libx11-dev 1106 * libxtst 1107 * libxtst-dev 1108 * libxext 1109 * libxext-dev 1110 1111 * Install the libraries into the cross-compilation toolchain. For instance: 1112 ``` 1113 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr 1114 mkdir X11R6 1115 cd X11R6 1116 for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done 1117 mv usr/* . 1118 cd lib 1119 cp arm-linux-gnueabihf/* . 1120 ``` 1121 1122 You can ignore the following messages. These libraries are not needed to 1123 successfully complete a full JDK build. 1124 ``` 1125 cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory 1126 cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory 1127 cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory 1128 ``` 1129 1130 * If the X11 libraries are not properly detected by `configure`, you can 1131 point them out by `--with-x`. 1132 1133### Creating And Using Sysroots With qemu-deboostrap 1134 1135Fortunately, you can create sysroots for foreign architectures with tools 1136provided by your OS. On Debian/Ubuntu systems, one could use `qemu-deboostrap` to 1137create the *target* system chroot, which would have the native libraries and headers 1138specific to that *target* system. After that, we can use the cross-compiler on the *build* 1139system, pointing into chroot to get the build dependencies right. This allows building 1140for foreign architectures with native compilation speed. 1141 1142For example, cross-compiling to AArch64 from x86_64 could be done like this: 1143 1144 * Install cross-compiler on the *build* system: 1145``` 1146apt install g++-aarch64-linux-gnu gcc-aarch64-linux-gnu 1147``` 1148 1149 * Create chroot on the *build* system, configuring it for *target* system: 1150``` 1151sudo qemu-debootstrap --arch=arm64 --verbose \ 1152 --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 \ 1153 --resolve-deps jessie /chroots/arm64 http://httpredir.debian.org/debian/ 1154``` 1155 1156 * Configure and build with newly created chroot as sysroot/toolchain-path: 1157``` 1158CC=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/ 1159make images 1160ls build/linux-aarch64-normal-server-release/ 1161``` 1162 1163The build does not create new files in that chroot, so it can be reused for multiple builds 1164without additional cleanup. 1165 1166Architectures that are known to successfully cross-compile like this are: 1167 1168 Target `CC` `CXX` `--arch=...` `--openjdk-target=...` 1169 ------------ ------------------------- --------------------------- ------------- ----------------------- 1170 x86 default default i386 i386-linux-gnu 1171 armhf gcc-arm-linux-gnueabihf g++-arm-linux-gnueabihf armhf arm-linux-gnueabihf 1172 aarch64 gcc-aarch64-linux-gnu g++-aarch64-linux-gnu arm64 aarch64-linux-gnu 1173 ppc64el gcc-powerpc64le-linux-gnu g++-powerpc64le-linux-gnu ppc64el powerpc64le-linux-gnu 1174 s390x gcc-s390x-linux-gnu g++-s390x-linux-gnu s390x s390x-linux-gnu 1175 1176Additional architectures might be supported by Debian/Ubuntu Ports. 1177 1178### Building for ARM/aarch64 1179 1180A common cross-compilation target is the ARM CPU. When building for ARM, it is 1181useful to set the ABI profile. A number of pre-defined ABI profiles are 1182available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt, 1183armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer 1184properly supported by the JDK. 1185 1186### Verifying the Build 1187 1188The build will end up in a directory named like 1189`build/linux-arm-normal-server-release`. 1190 1191Inside this build output directory, the `images/jdk` will contain the newly 1192built JDK, for your *target* system. 1193 1194Copy these folders to your *target* system. Then you can run e.g. 1195`images/jdk/bin/java -version`. 1196 1197## Build Performance 1198 1199Building the JDK requires a lot of horsepower. Some of the build tools can be 1200adjusted to utilize more or less of resources such as parallel threads and 1201memory. The `configure` script analyzes your system and selects reasonable 1202values for such options based on your hardware. If you encounter resource 1203problems, such as out of memory conditions, you can modify the detected values 1204with: 1205 1206 * `--with-num-cores` -- number of cores in the build system, e.g. 1207 `--with-num-cores=8`. 1208 1209 * `--with-memory-size` -- memory (in MB) available in the build system, e.g. 1210 `--with-memory-size=1024` 1211 1212You can also specify directly the number of build jobs to use with 1213`--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag 1214to `make`. In most cases it will be ignored by the makefiles, but it can cause 1215problems for some make targets. 1216 1217It might also be necessary to specify the JVM arguments passed to the Boot JDK, 1218using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the 1219default JVM arguments passed to the Boot JDK. 1220 1221At the end of a successful execution of `configure`, you will get a performance 1222summary, indicating how well the build will perform. Here you will also get 1223performance hints. If you want to build fast, pay attention to those! 1224 1225If you want to tweak build performance, run with `make LOG=info` to get a build 1226time summary at the end of the build process. 1227 1228### Disk Speed 1229 1230If you are using network shares, e.g. via NFS, for your source code, make sure 1231the build directory is situated on local disk (e.g. by `ln -s 1232/localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely 1233high for building on a network share; close to unusable. 1234 1235Also, make sure that your build tools (including Boot JDK and toolchain) is 1236located on a local disk and not a network share. 1237 1238As has been stressed elsewhere, do use SSD for source code and build directory, 1239as well as (if possible) the build tools. 1240 1241### Virus Checking 1242 1243The use of virus checking software, especially on Windows, can *significantly* 1244slow down building of the JDK. If possible, turn off such software, or exclude 1245the directory containing the JDK source code from on-the-fly checking. 1246 1247### Ccache 1248 1249The JDK build supports building with ccache when using gcc or clang. Using 1250ccache can radically speed up compilation of native code if you often rebuild 1251the same sources. Your milage may vary however, so we recommend evaluating it 1252for yourself. To enable it, make sure it's on the path and configure with 1253`--enable-ccache`. 1254 1255### Precompiled Headers 1256 1257By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains 1258were it is properly supported (clang, gcc, and Visual Studio). Normally, this 1259speeds up the build process, but in some circumstances, it can actually slow 1260things down. 1261 1262You can experiment by disabling precompiled headers using 1263`--disable-precompiled-headers`. 1264 1265### Icecc / icecream 1266 1267[icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a 1268distributed compiler network. If you have multiple machines available for 1269building the JDK, you can drastically cut individual build times by utilizing 1270it. 1271 1272To use, setup an icecc network, and install icecc on the build machine. Then 1273run `configure` using `--enable-icecc`. 1274 1275### Using sjavac 1276 1277To speed up Java compilation, especially incremental compilations, you can try 1278the experimental sjavac compiler by using `--enable-sjavac`. 1279 1280### Building the Right Target 1281 1282Selecting the proper target to build can have dramatic impact on build time. 1283For normal usage, `jdk` or the default target is just fine. You only need to 1284build `images` for shipping, or if your tests require it. 1285 1286See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on 1287how to build an even smaller subset of the product. 1288 1289## Troubleshooting 1290 1291If your build fails, it can sometimes be difficult to pinpoint the problem or 1292find a proper solution. 1293 1294### Locating the Source of the Error 1295 1296When a build fails, it can be hard to pinpoint the actual cause of the error. 1297In a typical build process, different parts of the product build in parallel, 1298with the output interlaced. 1299 1300#### Build Failure Summary 1301 1302To help you, the build system will print a failure summary at the end. It looks 1303like this: 1304 1305``` 1306ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2) 1307 1308=== Output from failing command(s) repeated here === 1309* For target hotspot_variant-server_libjvm_objs_psMemoryPool.o: 1310/localhome/hg/jdk9-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type 1311 ... (rest of output omitted) 1312 1313* All command lines available in /localhome/hg/jdk9-sandbox/build/linux-x64/make-support/failure-logs. 1314=== End of repeated output === 1315 1316=== Make failed targets repeated here === 1317lib/CompileJvm.gmk:207: recipe for target '/localhome/hg/jdk9-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed 1318make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed 1319=== End of repeated output === 1320 1321Hint: Try searching the build log for the name of the first failed target. 1322Hint: If caused by a warning, try configure --disable-warnings-as-errors. 1323``` 1324 1325Let's break it down! First, the selected configuration, and the top-level 1326target you entered on the command line that caused the failure is printed. 1327 1328Then, between the `Output from failing command(s) repeated here` and `End of 1329repeated output` the first lines of output (stdout and stderr) from the actual 1330failing command is repeated. In most cases, this is the error message that 1331caused the build to fail. If multiple commands were failing (this can happen in 1332a parallel build), output from all failed commands will be printed here. 1333 1334The path to the `failure-logs` directory is printed. In this file you will find 1335a `<target>.log` file that contains the output from this command in its 1336entirety, and also a `<target>.cmd`, which contain the complete command line 1337used for running this command. You can re-run the failing command by executing 1338`. <path to failure-logs>/<target>.cmd` in your shell. 1339 1340Another way to trace the failure is to follow the chain of make targets, from 1341top-level targets to individual file targets. Between `Make failed targets 1342repeated here` and `End of repeated output` the output from make showing this 1343chain is repeated. The first failed recipe will typically contain the full path 1344to the file in question that failed to compile. Following lines will show a 1345trace of make targets why we ended up trying to compile that file. 1346 1347Finally, some hints are given on how to locate the error in the complete log. 1348In this example, we would try searching the log file for "`psMemoryPool.o`". 1349Another way to quickly locate make errors in the log is to search for "`] 1350Error`" or "`***`". 1351 1352Note that the build failure summary will only help you if the issue was a 1353compilation failure or similar. If the problem is more esoteric, or is due to 1354errors in the build machinery, you will likely get empty output logs, and `No 1355indication of failed target found` instead of the make target chain. 1356 1357#### Checking the Build Log File 1358 1359The output (stdout and stderr) from the latest build is always stored in 1360`$BUILD/build.log`. The previous build log is stored as `build.log.old`. This 1361means that it is not necessary to redirect the build output yourself if you 1362want to process it. 1363 1364You can increase the verbosity of the log file, by the `LOG` control variable 1365to `make`. If you want to see the command lines used in compilations, use 1366`LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug` 1367or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g. 1368`LOG=info,cmdlines`. The `debug` log level will show most shell commands 1369executed by make, and `trace` will show all. Beware that both these log levels 1370will produce a massive build log! 1371 1372### Fixing Unexpected Build Failures 1373 1374Most of the time, the build will fail due to incorrect changes in the source 1375code. 1376 1377Sometimes the build can fail with no apparent changes that have caused the 1378failure. If this is the first time you are building the JDK on this particular 1379computer, and the build fails, the problem is likely with your build 1380environment. But even if you have previously built the JDK with success, and it 1381now fails, your build environment might have changed (perhaps due to OS 1382upgrades or similar). But most likely, such failures are due to problems with 1383the incremental rebuild. 1384 1385#### Problems with the Build Environment 1386 1387Make sure your configuration is correct. Re-run `configure`, and look for any 1388warnings. Warnings that appear in the middle of the `configure` output is also 1389repeated at the end, after the summary. The entire log is stored in 1390`$BUILD/configure.log`. 1391 1392Verify that the summary at the end looks correct. Are you indeed using the Boot 1393JDK and native toolchain that you expect? 1394 1395By default, the JDK has a strict approach where warnings from the compiler is 1396considered errors which fail the build. For very new or very old compiler 1397versions, this can trigger new classes of warnings, which thus fails the build. 1398Run `configure` with `--disable-warnings-as-errors` to turn of this behavior. 1399(The warnings will still show, but not make the build fail.) 1400 1401#### Problems with Incremental Rebuilds 1402 1403Incremental rebuilds mean that when you modify part of the product, only the 1404affected parts get rebuilt. While this works great in most cases, and 1405significantly speed up the development process, from time to time complex 1406interdependencies will result in an incorrect build result. This is the most 1407common cause for unexpected build problems. 1408 1409Here are a suggested list of things to try if you are having unexpected build 1410problems. Each step requires more time than the one before, so try them in 1411order. Most issues will be solved at step 1 or 2. 1412 1413 1. Make sure your repository is up-to-date 1414 1415 Run `hg pull -u` to make sure you have the latest changes. 1416 1417 2. Clean build results 1418 1419 The simplest way to fix incremental rebuild issues is to run `make clean`. 1420 This will remove all build results, but not the configuration or any build 1421 system support artifacts. In most cases, this will solve build errors 1422 resulting from incremental build mismatches. 1423 1424 3. Completely clean the build directory. 1425 1426 If this does not work, the next step is to run `make dist-clean`, or 1427 removing the build output directory (`$BUILD`). This will clean all 1428 generated output, including your configuration. You will need to re-run 1429 `configure` after this step. A good idea is to run `make 1430 print-configuration` before running `make dist-clean`, as this will print 1431 your current `configure` command line. Here's a way to do this: 1432 1433 ``` 1434 make print-configuration > current-configuration 1435 make dist-clean 1436 bash configure $(cat current-configuration) 1437 make 1438 ``` 1439 1440 4. Re-clone the Mercurial repository 1441 1442 Sometimes the Mercurial repository gets in a state that causes the product 1443 to be un-buildable. In such a case, the simplest solution is often the 1444 "sledgehammer approach": delete the entire repository, and re-clone it. 1445 If you have local changes, save them first to a different location using 1446 `hg export`. 1447 1448### Specific Build Issues 1449 1450#### Clock Skew 1451 1452If you get an error message like this: 1453``` 1454File 'xxx' has modification time in the future. 1455Clock skew detected. Your build may be incomplete. 1456``` 1457then the clock on your build machine is out of sync with the timestamps on the 1458source files. Other errors, apparently unrelated but in fact caused by the 1459clock skew, can occur along with the clock skew warnings. These secondary 1460errors may tend to obscure the fact that the true root cause of the problem is 1461an out-of-sync clock. 1462 1463If you see these warnings, reset the clock on the build machine, run `make 1464clean` and restart the build. 1465 1466#### Out of Memory Errors 1467 1468On Solaris, you might get an error message like this: 1469``` 1470Trouble writing out table to disk 1471``` 1472To solve this, increase the amount of swap space on your build machine. 1473 1474On Windows, you might get error messages like this: 1475``` 1476fatal error - couldn't allocate heap 1477cannot create ... Permission denied 1478spawn failed 1479``` 1480This can be a sign of a Cygwin problem. See the information about solving 1481problems in the [Cygwin](#cygwin) section. Rebooting the computer might help 1482temporarily. 1483 1484### Getting Help 1485 1486If none of the suggestions in this document helps you, or if you find what you 1487believe is a bug in the build system, please contact the Build Group by sending 1488a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net). 1489Please include the relevant parts of the configure and/or build log. 1490 1491If you need general help or advice about developing for the JDK, you can also 1492contact the Adoption Group. See the section on [Contributing to OpenJDK]( 1493#contributing-to-openjdk) for more information. 1494 1495## Hints and Suggestions for Advanced Users 1496 1497### Setting Up a Repository for Pushing Changes (defpath) 1498 1499To help you prepare a proper push path for a Mercurial repository, there exists 1500a useful tool known as [defpath]( 1501http://openjdk.java.net/projects/code-tools/defpath). It will help you setup a 1502proper push path for pushing changes to the JDK. 1503 1504Install the extension by cloning 1505`http://hg.openjdk.java.net/code-tools/defpath` and updating your `.hgrc` file. 1506Here's one way to do this: 1507 1508``` 1509cd ~ 1510mkdir hg-ext 1511cd hg-ext 1512hg clone http://hg.openjdk.java.net/code-tools/defpath 1513cat << EOT >> ~/.hgrc 1514[extensions] 1515defpath=~/hg-ext/defpath/defpath.py 1516EOT 1517``` 1518 1519You can now setup a proper push path using: 1520``` 1521hg defpath -d -u <your OpenJDK username> 1522``` 1523 1524### Bash Completion 1525 1526The `configure` and `make` commands tries to play nice with bash command-line 1527completion (using `<tab>` or `<tab><tab>`). To use this functionality, make 1528sure you enable completion in your `~/.bashrc` (see instructions for bash in 1529your operating system). 1530 1531Make completion will work out of the box, and will complete valid make targets. 1532For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`. 1533 1534The `configure` script can get completion for options, but for this to work you 1535need to help `bash` on the way. The standard way of running the script, `bash 1536configure`, will not be understood by bash completion. You need `configure` to 1537be the command to run. One way to achieve this is to add a simple helper script 1538to your path: 1539 1540``` 1541cat << EOT > /tmp/configure 1542#!/bin/bash 1543if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then 1544 echo >&2 "Abort: Trying to call configure helper recursively" 1545 exit 1 1546fi 1547 1548bash \$PWD/configure "\$@" 1549EOT 1550chmod +x /tmp/configure 1551sudo mv /tmp/configure /usr/local/bin 1552``` 1553 1554Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`. 1555 1556### Using Multiple Configurations 1557 1558You can have multiple configurations for a single source repository. When you 1559create a new configuration, run `configure --with-conf-name=<name>` to create a 1560configuration with the name `<name>`. Alternatively, you can create a directory 1561under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd 1562build/<name> && bash ../../configure`. 1563 1564Then you can build that configuration using `make CONF_NAME=<name>` or `make 1565CONF=<pattern>`, where `<pattern>` is a substring matching one or several 1566configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will 1567match *all* available configuration, so `make CONF= hotspot` will build the 1568`hotspot` target for all configurations. Alternatively, you can execute `make` 1569in the configuration directory, e.g. `cd build/<name> && make`. 1570 1571### Handling Reconfigurations 1572 1573If you update the repository and part of the configure script has changed, the 1574build system will force you to re-run `configure`. 1575 1576Most of the time, you will be fine by running `configure` again with the same 1577arguments as the last time, which can easily be performed by `make 1578reconfigure`. To simplify this, you can use the `CONF_CHECK` make control 1579variable, either as `make CONF_CHECK=auto`, or by setting an environment 1580variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc` 1581file, `make` will always run `reconfigure` automatically whenever the configure 1582script has changed. 1583 1584You can also use `CONF_CHECK=ignore` to skip the check for a needed configure 1585update. This might speed up the build, but comes at the risk of an incorrect 1586build result. This is only recommended if you know what you're doing. 1587 1588From time to time, you will also need to modify the command line to `configure` 1589due to changes. Use `make print-configure` to show the command line used for 1590your current configuration. 1591 1592### Using Fine-Grained Make Targets 1593 1594The default behavior for make is to create consistent and correct output, at 1595the expense of build speed, if necessary. 1596 1597If you are prepared to take some risk of an incorrect build, and know enough of 1598the system to understand how things build and interact, you can speed up the 1599build process considerably by instructing make to only build a portion of the 1600product. 1601 1602#### Building Individual Modules 1603 1604The safe way to use fine-grained make targets is to use the module specific 1605make targets. All source code in the JDK is organized so it belongs to a 1606module, e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific 1607module, by giving it as make target: `make jdk.jdwp.agent`. If the specified 1608module depends on other modules (e.g. `java.base`), those modules will be built 1609first. 1610 1611You can also specify a set of modules, just as you can always specify a set of 1612make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi 1613jdk.crypto.ucrypto` 1614 1615#### Building Individual Module Phases 1616 1617The build process for each module is divided into separate phases. Not all 1618modules need all phases. Which are needed depends on what kind of source code 1619and other artifact the module consists of. The phases are: 1620 1621 * `gensrc` (Generate source code to compile) 1622 * `gendata` (Generate non-source code artifacts) 1623 * `copy` (Copy resource artifacts) 1624 * `java` (Compile Java code) 1625 * `launchers` (Compile native executables) 1626 * `libs` (Compile native libraries) 1627 * `rmic` (Run the `rmic` tool) 1628 1629You can build only a single phase for a module by using the notation 1630`$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`, 1631use `make java.base-gensrc`. 1632 1633Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if 1634present). Make will build all needed prerequisites before building the 1635requested phase. 1636 1637#### Skipping the Dependency Check 1638 1639When using an iterative development style with frequent quick rebuilds, the 1640dependency check made by make can take up a significant portion of the time 1641spent on the rebuild. In such cases, it can be useful to bypass the dependency 1642check in make. 1643 1644> **Note that if used incorrectly, this can lead to a broken build!** 1645 1646To achieve this, append `-only` to the build target. For instance, `make 1647jdk.jdwp.agent-java-only` will *only* build the `java` phase of the 1648`jdk.jdwp.agent` module. If the required dependencies are not present, the 1649build can fail. On the other hand, the execution time measures in milliseconds. 1650 1651A useful pattern is to build the first time normally (e.g. `make 1652jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target. 1653 1654#### Rebuilding Part of java.base (JDK\_FILTER) 1655 1656If you are modifying files in `java.base`, which is the by far largest module 1657in the JDK, then you need to rebuild all those files whenever a single file has 1658changed. (This inefficiency will hopefully be addressed in JDK 10.) 1659 1660As a hack, you can use the make control variable `JDK_FILTER` to specify a 1661pattern that will be used to limit the set of files being recompiled. For 1662instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods, 1663`make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation 1664to files in the `javax.crypto` package. 1665 1666### Learn About Mercurial 1667 1668To become an efficient JDK developer, it is recommended that you invest in 1669learning Mercurial properly. Here are some links that can get you started: 1670 1671 * [Mercurial for git users](http://www.mercurial-scm.org/wiki/GitConcepts) 1672 * [The official Mercurial tutorial](http://www.mercurial-scm.org/wiki/Tutorial) 1673 * [hg init](http://hginit.com/) 1674 * [Mercurial: The Definitive Guide](http://hgbook.red-bean.com/read/) 1675 1676## Understanding the Build System 1677 1678This section will give you a more technical description on the details of the 1679build system. 1680 1681### Configurations 1682 1683The build system expects to find one or more configuration. These are 1684technically defined by the `spec.gmk` in a subdirectory to the `build` 1685subdirectory. The `spec.gmk` file is generated by `configure`, and contains in 1686principle the configuration (directly or by files included by `spec.gmk`). 1687 1688You can, in fact, select a configuration to build by pointing to the `spec.gmk` 1689file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`. 1690While this is not the recommended way to call `make` as a user, it is what is 1691used under the hood by the build system. 1692 1693### Build Output Structure 1694 1695The build output for a configuration will end up in `build/<configuration 1696name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory 1697contains the following important directories: 1698 1699``` 1700buildtools/ 1701configure-support/ 1702hotspot/ 1703images/ 1704jdk/ 1705make-support/ 1706support/ 1707test-results/ 1708test-support/ 1709``` 1710 1711This is what they are used for: 1712 1713 * `images`: This is the directory were the output of the `*-image` make 1714 targets end up. For instance, `make jdk-image` ends up in `images/jdk`. 1715 1716 * `jdk`: This is the "exploded image". After `make jdk`, you will be able to 1717 launch the newly built JDK by running `$BUILD/jdk/bin/java`. 1718 1719 * `test-results`: This directory contains the results from running tests. 1720 1721 * `support`: This is an area for intermediate files needed during the build, 1722 e.g. generated source code, object files and class files. Some noteworthy 1723 directories in `support` is `gensrc`, which contains the generated source 1724 code, and the `modules_*` directories, which contains the files in a 1725 per-module hierarchy that will later be collapsed into the `jdk` directory 1726 of the exploded image. 1727 1728 * `buildtools`: This is an area for tools compiled for the build platform 1729 that are used during the rest of the build. 1730 1731 * `hotspot`: This is an area for intermediate files needed when building 1732 hotspot. 1733 1734 * `configure-support`, `make-support` and `test-support`: These directories 1735 contain files that are needed by the build system for `configure`, `make` 1736 and for running tests. 1737 1738### Fixpath 1739 1740Windows path typically look like `C:\User\foo`, while Unix paths look like 1741`/home/foo`. Tools with roots from Unix often experience issues related to this 1742mismatch when running on Windows. 1743 1744In the JDK build, we always use Unix paths internally, and only just before 1745calling a tool that does not understand Unix paths do we convert them to 1746Windows paths. 1747 1748This conversion is done by the `fixpath` tool, which is a small wrapper that 1749modifies unix-style paths to Windows-style paths in command lines. Fixpath is 1750compiled automatically by `configure`. 1751 1752### Native Debug Symbols 1753 1754Native libraries and executables can have debug symbol (and other debug 1755information) associated with them. How this works is very much platform 1756dependent, but a common problem is that debug symbol information takes a lot of 1757disk space, but is rarely needed by the end user. 1758 1759The JDK supports different methods on how to handle debug symbols. The 1760method used is selected by `--with-native-debug-symbols`, and available methods 1761are `none`, `internal`, `external`, `zipped`. 1762 1763 * `none` means that no debug symbols will be generated during the build. 1764 1765 * `internal` means that debug symbols will be generated during the build, and 1766 they will be stored in the generated binary. 1767 1768 * `external` means that debug symbols will be generated during the build, and 1769 after the compilation, they will be moved into a separate `.debuginfo` file. 1770 (This was previously known as FDS, Full Debug Symbols). 1771 1772 * `zipped` is like `external`, but the .debuginfo file will also be zipped 1773 into a `.diz` file. 1774 1775When building for distribution, `zipped` is a good solution. Binaries built 1776with `internal` is suitable for use by developers, since they facilitate 1777debugging, but should be stripped before distributed to end users. 1778 1779### Autoconf Details 1780 1781The `configure` script is based on the autoconf framework, but in some details 1782deviate from a normal autoconf `configure` script. 1783 1784The `configure` script in the top level directory of the JDK is just a thin 1785wrapper that calls `make/autoconf/configure`. This in turn will run `autoconf` 1786to create the runnable (generated) configure script, as 1787`.build/generated-configure.sh`. Apart from being responsible for the 1788generation of the runnable script, the `configure` script also provides 1789functionality that is not easily expressed in the normal Autoconf framework. As 1790part of this functionality, the generated script is called. 1791 1792The build system will detect if the Autoconf source files have changed, and 1793will trigger a regeneration of the generated script if needed. You can also 1794manually request such an update by `bash configure autogen`. 1795 1796In previous versions of the JDK, the generated script was checked in at 1797`make/autoconf/generated-configure.sh`. This is no longer the case. 1798 1799### Developing the Build System Itself 1800 1801This section contains a few remarks about how to develop for the build system 1802itself. It is not relevant if you are only making changes in the product source 1803code. 1804 1805While technically using `make`, the make source files of the JDK does not 1806resemble most other Makefiles. Instead of listing specific targets and actions 1807(perhaps using patterns), the basic modus operandi is to call a high-level 1808function (or properly, macro) from the API in `make/common`. For instance, to 1809compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module, 1810a call like this would be made: 1811 1812``` 1813$(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \ 1814 SETUP := GENERATE_OLDBYTECODE, \ 1815 SRC := $(TOPDIR)/src/jkd.foo/share/classes, \ 1816 INCLUDES := jdk/internal/foo, \ 1817 BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \ 1818)) 1819``` 1820 1821By encapsulating and expressing the high-level knowledge of *what* should be 1822done, rather than *how* it should be done (as is normal in Makefiles), we can 1823build a much more powerful and flexible build system. 1824 1825Correct dependency tracking is paramount. Sloppy dependency tracking will lead 1826to improper parallelization, or worse, race conditions. 1827 1828To test for/debug race conditions, try running `make JOBS=1` and `make 1829JOBS=100` and see if it makes any difference. (It shouldn't). 1830 1831To compare the output of two different builds and see if, and how, they differ, 1832run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two 1833builds you want to compare. 1834 1835To automatically build two consecutive versions and compare them, use 1836`COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value 1837assignments, like this: 1838``` 1839make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot 1840``` 1841See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`. 1842 1843To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`. 1844Use `JOBS=1` to avoid parallelism. 1845 1846Please check that you adhere to the [Code Conventions for the Build System]( 1847http://openjdk.java.net/groups/build/doc/code-conventions.html) before 1848submitting patches. 1849 1850## Contributing to the JDK 1851 1852So, now you've built your JDK, and made your first patch, and want to 1853contribute it back to the OpenJDK Community. 1854 1855First of all: Thank you! We gladly welcome your contribution. 1856However, please bear in mind that the JDK is a massive project, and we must ask 1857you to follow our rules and guidelines to be able to accept your contribution. 1858 1859The official place to start is the ['How to contribute' page]( 1860http://openjdk.java.net/contribute/). There is also an official (but somewhat 1861outdated and skimpy on details) [Developer's Guide]( 1862http://openjdk.java.net/guide/). 1863 1864If this seems overwhelming to you, the Adoption Group is there to help you! A 1865good place to start is their ['New Contributor' page]( 1866https://wiki.openjdk.java.net/display/Adoption/New+Contributor), or start 1867reading the comprehensive [Getting Started Kit]( 1868https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The 1869Adoption Group will also happily answer any questions you have about 1870contributing. Contact them by [mail]( 1871http://mail.openjdk.java.net/mailman/listinfo/adoption-discuss) or [IRC]( 1872http://openjdk.java.net/irc/). 1873 1874--- 1875# Override styles from the base CSS file that are not ideal for this document. 1876header-includes: 1877 - '<style type="text/css">pre, code, tt { color: #1d6ae5; }</style>' 1878--- 1879