building.md revision 2696:49a15c503104
1% Building OpenJDK 2 3## TL;DR (Instructions for the Impatient) 4 5If you are eager to try out building OpenJDK, 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 OpenJDK repository that you want to build. 8 9 1. [Get the complete source code](#getting-the-source-code): \ 10 `bash get_source.sh` 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), [external libraries]( 17 #external-library-requirements) or the [boot JDK](#boot-jdk-requirements)), 18 most of the time it prints a suggestion on how to resolve the situation on 19 your platform. Follow the instructions, and try running `bash configure` 20 again. 21 22 3. [Run make](#running-make): \ 23 `make images` 24 25 4. Verify your newly built JDK: \ 26 `./build/*/images/jdk/bin/java -version` 27 28 5. [Run basic tests](##running-tests): \ 29 `make run-test-tier1` 30 31If any of these steps failed, or if you want to know more about build 32requirements or build functionality, please continue reading this document. 33 34## Introduction 35 36OpenJDK is a complex software project. Building it requires a certain amount of 37technical expertise, a fair number of dependencies on external software, and 38reasonably powerful hardware. 39 40If you just want to use OpenJDK and not build it yourself, this document is not 41for you. See for instance [OpenJDK installation]( 42http://openjdk.java.net/install) for some methods of installing a prebuilt 43OpenJDK. 44 45## Getting the Source Code 46 47OpenJDK uses [Mercurial](http://www.mercurial-scm.org) for source control. The 48source code is contained not in a single Mercurial repository, but in a tree 49("forest") of interrelated repositories. You will need to check out all of the 50repositories to be able to build OpenJDK. To assist you in dealing with this 51somewhat unusual arrangement, there are multiple tools available, which are 52explained below. 53 54In any case, make sure you are getting the correct version. At the [OpenJDK 55Mercurial server](http://hg.openjdk.java.net/) you can see a list of all 56available forests. If you want to build an older version, e.g. JDK 8, it is 57recommended that you get the `jdk8u` forest, which contains incremental 58updates, instead of the `jdk8` forest, which was frozen at JDK 8 GA. 59 60If you are new to Mercurial, a good place to start is the [Mercurial Beginner's 61Guide](http://www.mercurial-scm.org/guide). The rest of this document assumes a 62working knowledge of Mercurial. 63 64### Special Considerations 65 66For a smooth building experience, it is recommended that you follow these rules 67on where and how to check out the source code. 68 69 * Do not check out the source code in a path which contains spaces. Chances 70 are the build will not work. This is most likely to be an issue on Windows 71 systems. 72 73 * Do not check out the source code in a path which has a very long name or is 74 nested many levels deep. Chances are you will hit an OS limitation during 75 the build. 76 77 * Put the source code on a local disk, not a network share. If possible, use 78 an SSD. The build process is very disk intensive, and having slow disk 79 access will significantly increase build times. If you need to use a 80 network share for the source code, see below for suggestions on how to keep 81 the build artifacts on a local disk. 82 83 * On Windows, extra care must be taken to make sure the [Cygwin](#cygwin) 84 environment is consistent. It is recommended that you follow this 85 procedure: 86 87 * Create the directory that is going to contain the top directory of the 88 OpenJDK clone by using the `mkdir` command in the Cygwin bash shell. 89 That is, do *not* create it using Windows Explorer. This will ensure 90 that it will have proper Cygwin attributes, and that it's children will 91 inherit those attributes. 92 93 * Do not put the OpenJDK clone in a path under your Cygwin home 94 directory. This is especially important if your user name contains 95 spaces and/or mixed upper and lower case letters. 96 97 * Clone the OpenJDK repository using the Cygwin command line `hg` client 98 as instructed in this document. That is, do *not* use another Mercurial 99 client such as TortoiseHg. 100 101 Failure to follow this procedure might result in hard-to-debug build 102 problems. 103 104### Using get\_source.sh 105 106The simplest way to get the entire forest is probably to clone the top-level 107repository and then run the `get_source.sh` script, like this: 108 109``` 110hg clone http://hg.openjdk.java.net/jdk9/jdk9 111cd jdk9 112bash get_source.sh 113``` 114 115The first time this is run, it will clone all the sub-repositories. Any 116subsequent execution of the script will update all sub-repositories to the 117latest revision. 118 119### Using hgforest.sh 120 121The `hgforest.sh` script is more expressive than `get_source.sh`. It takes any 122number of arguments, and runs `hg` with those arguments on each sub-repository 123in the forest. The `get_source.sh` script is basically a simple wrapper that 124runs either `hgforest.sh clone` or `hgforest.sh pull -u`. 125 126 * Cloning the forest: 127 ``` 128 hg clone http://hg.openjdk.java.net/jdk9/jdk9 129 cd jdk9 130 bash common/bin/hgforest.sh clone 131 ``` 132 133 * Pulling and updating the forest: 134 ``` 135 bash common/bin/hgforest.sh pull -u 136 ``` 137 138 * Merging over the entire forest: 139 ``` 140 bash common/bin/hgforest.sh merge 141 ``` 142 143### Using the Trees Extension 144 145The trees extension is a Mercurial add-on that helps you deal with the forest. 146More information is available on the [Code Tools trees page]( 147http://openjdk.java.net/projects/code-tools/trees). 148 149#### Installing the Extension 150 151Install the extension by cloning `http://hg.openjdk.java.net/code-tools/trees` 152and updating your `.hgrc` file. Here's one way to do this: 153 154``` 155cd ~ 156mkdir hg-ext 157cd hg-ext 158hg clone http://hg.openjdk.java.net/code-tools/trees 159cat << EOT >> ~/.hgrc 160[extensions] 161trees=~/hg-ext/trees/trees.py 162EOT 163``` 164 165#### Initializing the Tree 166 167The trees extension needs to know the structure of the forest. If you have 168already cloned the entire forest using another method, you can initialize the 169forest like this: 170 171``` 172hg tconf --set --walk --depth 173``` 174 175Or you can clone the entire forest at once, if you substitute `clone` with 176`tclone` when cloning the top-level repository, e.g. like this: 177 178``` 179hg tclone http://hg.openjdk.java.net/jdk9/jdk9 180``` 181 182In this case, the forest will be properly initialized from the start. 183 184#### Other Operations 185 186The trees extensions supplement many common operations with a trees version by 187prefixing a `t` to the normal Mercurial command, e.g. `tcommit`, `tstatus` or 188`tmerge`. For instance, to update the entire forest: 189 190``` 191hg tpull -u 192``` 193 194## Build Hardware Requirements 195 196OpenJDK is a massive project, and require machines ranging from decent to 197powerful to be able to build in a reasonable amount of time, or to be able to 198complete a build at all. 199 200We *strongly* recommend usage of an SSD disk for the build, since disk speed is 201one of the limiting factors for build performance. 202 203### Building on x86 204 205At a minimum, a machine with 2-4 cores is advisable, as well as 2-4 GB of RAM. 206(The more cores to use, the more memory you need.) At least 6 GB of free disk 207space is required (8 GB minimum for building on Solaris). 208 209Even for 32-bit builds, it is recommended to use a 64-bit build machine, and 210instead create a 32-bit target using `--with-target-bits=32`. 211 212### Building on sparc 213 214At a minimum, a machine with 4 cores is advisable, as well as 4 GB of RAM. (The 215more cores to use, the more memory you need.) At least 8 GB of free disk space 216is required. 217 218### Building on arm/aarch64 219 220This is not recommended. Instead, see the section on [Cross-compiling]( 221#cross-compiling). 222 223## Operating System Requirements 224 225The mainline OpenJDK project supports Linux, Solaris, macOS, AIX and Windows. 226Support for other operating system, e.g. BSD, exists in separate "port" 227projects. 228 229In general, OpenJDK can be built on a wide range of versions of these operating 230systems, but the further you deviate from what is tested on a daily basis, the 231more likely you are to run into problems. 232 233This table lists the OS versions used by Oracle when building JDK 9. Such 234information is always subject to change, but this table is up to date at the 235time of writing. 236 237 Operating system Vendor/version used 238 ----------------- ------------------------------------------------------- 239 Linux Oracle Enterprise Linux 6.4 / 7.1 (using kernel 3.8.13) 240 Solaris Solaris 11.1 SRU 21.4.1 / 11.2 SRU 5.5 241 macOS Mac OS X 10.9 (Mavericks) / 10.10 (Yosemite) 242 Windows Windows Server 2012 R2 243 244The double version numbers for Linux, Solaris and macOS is due to the hybrid 245model used at Oracle, where header files and external libraries from an older 246version is used when building on a more modern version of the OS. 247 248The Build Group has a wiki page with [Supported Build Platforms]( 249https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms). From 250time to time, this is updated by the community to list successes or failures of 251building on different platforms. 252 253### Windows 254 255Windows XP is not a supported platform, but all newer Windows should be able to 256build OpenJDK. 257 258On Windows, it is important that you pay attention to the instructions in the 259[Special Considerations](#special-considerations). 260 261Windows is the only non-POSIX OS supported by OpenJDK, and as such, requires 262some extra care. A POSIX support layer is required to build on Windows. For 263OpenJDK 9, the only supported such layer is Cygwin. (Msys is no longer 264supported due to a too old bash; msys2 and the new Windows Subsystem for Linux 265(WSL) would likely be possible to support in a future version but that would 266require a community effort to implement.) 267 268Internally in the build system, all paths are represented as Unix-style paths, 269e.g. `/cygdrive/c/hg/jdk9/Makefile` rather than `C:\hg\jdk9\Makefile`. This 270rule also applies to input to the build system, e.g. in arguments to 271`configure`. So, use `--with-freetype=/cygdrive/c/freetype` rather than 272`--with-freetype=c:\freetype`. For details on this conversion, see the section 273on [Fixpath](#fixpath). 274 275#### Cygwin 276 277A functioning [Cygwin](http://www.cygwin.com/) environment is thus required for 278building OpenJDK on Windows. If you have a 64-bit OS, we strongly recommend 279using the 64-bit version of Cygwin. 280 281**Note:** Cygwin has a model of continuously updating all packages without any 282easy way to install or revert to a specific version of a package. This means 283that whenever you add or update a package in Cygwin, you might (inadvertently) 284update tools that are used by the OpenJDK build process, and that can cause 285unexpected build problems. 286 287OpenJDK requires GNU Make 4.0 or greater on Windows. This is usually not a 288problem, since Cygwin currently only distributes GNU Make at a version above 2894.0. 290 291Apart from the basic Cygwin installation, the following packages must also be 292installed: 293 294 * `make` 295 * `zip` 296 * `unzip` 297 298Often, you can install these packages using the following command line: 299``` 300<path to Cygwin setup>/setup-x86_64 -q -P make -P unzip -P zip 301``` 302 303Unfortunately, Cygwin can be unreliable in certain circumstances. If you 304experience build tool crashes or strange issues when building on Windows, 305please check the Cygwin FAQ on the ["BLODA" list]( 306https://cygwin.com/faq/faq.html#faq.using.bloda) and the section on [fork() 307failures](https://cygwin.com/faq/faq.html#faq.using.fixing-fork-failures). 308 309### Solaris 310 311See `make/devkit/solaris11.1-package-list.txt` for a list of recommended 312packages to install when building on Solaris. The versions specified in this 313list is the versions used by the daily builds at Oracle, and is likely to work 314properly. 315 316Older versions of Solaris shipped a broken version of `objcopy`. At least 317version 2.21.1 is needed, which is provided by Solaris 11 Update 1. Objcopy is 318needed if you want to have external debug symbols. Please make sure you are 319using at least version 2.21.1 of objcopy, or that you disable external debug 320symbols. 321 322### macOS 323 324Apple is using a quite aggressive scheme of pushing OS updates, and coupling 325these updates with required updates of Xcode. Unfortunately, this makes it 326difficult for a project like OpenJDK to keep pace with a continuously updated 327machine running macOS. See the section on [Apple Xcode](#apple-xcode) on some 328strategies to deal with this. 329 330It is recommended that you use at least Mac OS X 10.9 (Mavericks). At the time 331of writing, OpenJDK has been successfully compiled on macOS versions up to 33210.12.5 (Sierra), using XCode 8.3.2 and `--disable-warnings-as-errors`. 333 334The standard macOS environment contains the basic tooling needed to build, but 335for external libraries a package manager is recommended. OpenJDK uses 336[homebrew](https://brew.sh/) in the examples, but feel free to use whatever 337manager you want (or none). 338 339### Linux 340 341It is often not much problem to build OpenJDK on Linux. The only general advice 342is to try to use the compilers, external libraries and header files as provided 343by your distribution. 344 345The basic tooling is provided as part of the core operating system, but you 346will most likely need to install developer packages. 347 348For apt-based distributions (Debian, Ubuntu, etc), try this: 349``` 350sudo apt-get install build-essential 351``` 352 353For rpm-based distributions (Fedora, Red Hat, etc), try this: 354``` 355sudo yum groupinstall "Development Tools" 356``` 357 358### AIX 359 360The regular builds by SAP is using AIX version 7.1, but AIX 5.3 is also 361supported. See the [OpenJDK PowerPC Port Status Page]( 362http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details. 363 364## Native Compiler (Toolchain) Requirements 365 366Large portions of OpenJDK consists of native code, that needs to be compiled to 367be able to run on the target platform. In theory, toolchain and operating 368system should be independent factors, but in practice there's more or less a 369one-to-one correlation between target operating system and toolchain. 370 371 Operating system Supported toolchain 372 ------------------ ------------------------- 373 Linux gcc, clang 374 macOS Apple Xcode (using clang) 375 Solaris Oracle Solaris Studio 376 AIX IBM XL C/C++ 377 Windows Microsoft Visual Studio 378 379Please see the individual sections on the toolchains for version 380recommendations. As a reference, these versions of the toolchains are used, at 381the time of writing, by Oracle for the daily builds of OpenJDK. It should be 382possible to compile OpenJDK with both older and newer versions, but the closer 383you stay to this list, the more likely you are to compile successfully without 384issues. 385 386 Operating system Toolchain version 387 ------------------ ------------------------------------------------------- 388 Linux gcc 4.9.2 389 macOS Apple Xcode 6.3 (using clang 6.1.0) 390 Solaris Oracle Solaris Studio 12.4 (with compiler version 5.13) 391 Windows Microsoft Visual Studio 2013 update 4 392 393### gcc 394 395The minimum accepted version of gcc is 4.7. Older versions will generate a warning 396by `configure` and are unlikely to work. 397 398OpenJDK 9 includes patches that should allow gcc 6 to compile, but this should 399be considered experimental. 400 401In general, any version between these two should be usable. 402 403### clang 404 405The minimum accepted version of clang is 3.2. Older versions will not be 406accepted by `configure`. 407 408To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`. 409 410### Apple Xcode 411 412The oldest supported version of Xcode is 5. 413 414You will need the Xcode command lines developers tools to be able to build 415OpenJDK. (Actually, *only* the command lines tools are needed, not the IDE.) 416The simplest way to install these is to run: 417``` 418xcode-select --install 419``` 420 421It is advisable to keep an older version of Xcode for building OpenJDK when 422updating Xcode. This [blog page]( 423http://iosdevelopertips.com/xcode/install-multiple-versions-of-xcode.html) has 424good suggestions on managing multiple Xcode versions. To use a specific version 425of Xcode, use `xcode-select -s` before running `configure`, or use 426`--with-toolchain-path` to point to the version of Xcode to use, e.g. 427`configure --with-toolchain-path=/Applications/Xcode5.app/Contents/Developer/usr/bin` 428 429If you have recently (inadvertently) updated your OS and/or Xcode version, and 430OpenJDK can no longer be built, please see the section on [Problems with the 431Build Environment](#problems-with-the-build-environment), and [Getting 432Help](#getting-help) to find out if there are any recent, non-merged patches 433available for this update. 434 435### Oracle Solaris Studio 436 437The minimum accepted version of the Solaris Studio compilers is 5.13 438(corresponding to Solaris Studio 12.4). Older versions will not be accepted by 439configure. 440 441The Solaris Studio installation should contain at least these packages: 442 443 Package Version 444 -------------------------------------------------- ------------- 445 developer/solarisstudio-124/backend 12.4-1.0.6.0 446 developer/solarisstudio-124/c++ 12.4-1.0.10.0 447 developer/solarisstudio-124/cc 12.4-1.0.4.0 448 developer/solarisstudio-124/library/c++-libs 12.4-1.0.10.0 449 developer/solarisstudio-124/library/math-libs 12.4-1.0.0.1 450 developer/solarisstudio-124/library/studio-gccrt 12.4-1.0.0.1 451 developer/solarisstudio-124/studio-common 12.4-1.0.0.1 452 developer/solarisstudio-124/studio-ja 12.4-1.0.0.1 453 developer/solarisstudio-124/studio-legal 12.4-1.0.0.1 454 developer/solarisstudio-124/studio-zhCN 12.4-1.0.0.1 455 456Compiling with Solaris Studio can sometimes be finicky. This is the exact 457version used by Oracle, which worked correctly at the time of writing: 458``` 459$ cc -V 460cc: Sun C 5.13 SunOS_i386 2014/10/20 461$ CC -V 462CC: Sun C++ 5.13 SunOS_i386 151846-10 2015/10/30 463``` 464 465### Microsoft Visual Studio 466 467The minimum accepted version of Visual Studio is 2010. Older versions will not 468be accepted by `configure`. The maximum accepted version of Visual Studio is 4692013. 470 471If you have multiple versions of Visual Studio installed, `configure` will by 472default pick the latest. You can request a specific version to be used by 473setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2010`. 474 475If you get `LINK: fatal error LNK1123: failure during conversion to COFF: file 476invalid` when building using Visual Studio 2010, you have encountered 477[KB2757355](http://support.microsoft.com/kb/2757355), a bug triggered by a 478specific installation order. However, the solution suggested by the KB article 479does not always resolve the problem. See [this stackoverflow discussion]( 480https://stackoverflow.com/questions/10888391) for other suggestions. 481 482### IBM XL C/C++ 483 484The regular builds by SAP is using version 12.1, described as `IBM XL C/C++ for 485AIX, V12.1 (5765-J02, 5725-C72) Version: 12.01.0000.0017`. 486 487See the [OpenJDK PowerPC Port Status Page]( 488http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details. 489 490## Boot JDK Requirements 491 492Paradoxically, building OpenJDK requires a pre-existing JDK. This is called the 493"boot JDK". The boot JDK does not have to be OpenJDK, though. If you are 494porting OpenJDK to a new platform, chances are that there already exists 495another JDK for that platform that is usable as boot JDK. 496 497The rule of thumb is that the boot JDK for building JDK major version *N* 498should be an JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be 499suitable as boot JDK. However, OpenJDK should be able to "build itself", so an 500up-to-date build of the current OpenJDK source is an acceptable alternative. If 501you are following the *N-1* rule, make sure you got the latest update version, 502since JDK 8 GA might not be able to build JDK 9 on all platforms. 503 504If the Boot JDK is not automatically detected, or the wrong JDK is picked, use 505`--with-boot-jdk` to point to the JDK to use. 506 507### JDK 8 on Linux 508 509On apt-based distros (like Debian and Ubuntu), `sudo apt-get install 510openjdk-8-jdk` is typically enough to install OpenJDK 8. On rpm-based distros 511(like Fedora and Red Hat), try `sudo yum install java-1.8.0-openjdk-devel`. 512 513### JDK 8 on Windows 514 515No pre-compiled binaries of OpenJDK 8 are readily available for Windows at the 516time of writing. An alternative is to download the [Oracle JDK]( 517http://www.oracle.com/technetwork/java/javase/downloads). Another is the [Adopt 518OpenJDK Project](https://adoptopenjdk.net/), which publishes experimental 519prebuilt binaries for Windows. 520 521### JDK 8 on macOS 522 523No pre-compiled binaries of OpenJDK 8 are readily available for macOS at the 524time of writing. An alternative is to download the [Oracle JDK]( 525http://www.oracle.com/technetwork/java/javase/downloads), or to install it 526using `brew cask install java`. Another option is the [Adopt OpenJDK Project]( 527https://adoptopenjdk.net/), which publishes experimental prebuilt binaries for 528macOS. 529 530### JDK 8 on AIX 531 532No pre-compiled binaries of OpenJDK 8 are readily available for AIX at the 533time of writing. A starting point for working with OpenJDK on AIX is 534the [PowerPC/AIX Port Project](http://openjdk.java.net/projects/ppc-aix-port/). 535 536## External Library Requirements 537 538Different platforms require different external libraries. In general, libraries 539are not optional - that is, they are either required or not used. 540 541If a required library is not detected by `configure`, you need to provide the 542path to it. There are two forms of the `configure` arguments to point to an 543external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to 544include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise, 545but require the include files an library files to reside in a default hierarchy 546under this directory. In most cases, it works fine. 547 548As a fallback, the second version allows you to point to the include directory 549and the lib directory separately. 550 551### FreeType 552 553FreeType2 from [The FreeType Project](http://www.freetype.org/) is required on 554all platforms. At least version 2.3 is required. 555 556 * To install on an apt-based Linux, try running `sudo apt-get install 557 libcups2-dev`. 558 * To install on an rpm-based Linux, try running `sudo yum install 559 cups-devel`. 560 * To install on Solaris, try running `pkg install system/library/freetype-2`. 561 * To install on macOS, try running `brew install freetype`. 562 * To install on Windows, see [below](#building-freetype-on-windows). 563 564Use `--with-freetype=<path>` if `configure` does not properly locate your 565FreeType files. 566 567#### Building FreeType on Windows 568 569On Windows, there is no readily available compiled version of FreeType. OpenJDK 570can help you compile FreeType from source. Download the FreeType sources and 571unpack them into an arbitrary directory: 572 573``` 574wget http://download.savannah.gnu.org/releases/freetype/freetype-2.5.3.tar.gz 575tar -xzf freetype-2.5.3.tar.gz 576``` 577 578Then run `configure` with `--with-freetype-src=<freetype_src>`. This will 579automatically build the freetype library into `<freetype_src>/lib64` for 64-bit 580builds or into `<freetype_src>/lib32` for 32-bit builds. Afterwards you can 581always use `--with-freetype-include=<freetype_src>/include` and 582`--with-freetype-lib=<freetype_src>/lib[32|64]` for other builds. 583 584Alternatively you can unpack the sources like this to use the default 585directory: 586 587``` 588tar --one-top-level=$HOME/freetype --strip-components=1 -xzf freetype-2.5.3.tar.gz 589``` 590 591### CUPS 592 593CUPS, [Common UNIX Printing System](http://www.cups.org) header files are 594required on all platforms, except Windows. Often these files are provided by 595your operating system. 596 597 * To install on an apt-based Linux, try running `sudo apt-get install 598 libcups2-dev`. 599 * To install on an rpm-based Linux, try running `sudo yum install 600 cups-devel`. 601 * To install on Solaris, try running `pkg install print/cups`. 602 603Use `--with-cups=<path>` if `configure` does not properly locate your CUPS 604files. 605 606### X11 607 608Certain [X11](http://www.x.org/) libraries and include files are required on 609Linux and Solaris. 610 611 * To install on an apt-based Linux, try running `sudo apt-get install 612 libx11-dev libxext-dev libxrender-dev libxtst-dev libxt-dev`. 613 * To install on an rpm-based Linux, try running `sudo yum install 614 libXtst-devel libXt-devel libXrender-devel libXi-devel`. 615 * To install on Solaris, try running `pkg install x11/header/x11-protocols 616 x11/library/libice x11/library/libpthread-stubs x11/library/libsm 617 x11/library/libx11 x11/library/libxau x11/library/libxcb 618 x11/library/libxdmcp x11/library/libxevie x11/library/libxext 619 x11/library/libxrender x11/library/libxscrnsaver x11/library/libxtst 620 x11/library/toolkit/libxt`. 621 622Use `--with-x=<path>` if `configure` does not properly locate your X11 files. 623 624### ALSA 625 626ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is 627required on Linux. At least version 0.9.1 of ALSA is required. 628 629 * To install on an apt-based Linux, try running `sudo apt-get install 630 libasound2-dev`. 631 * To install on an rpm-based Linux, try running `sudo yum install 632 alsa-lib-devel`. 633 634Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA 635files. 636 637### libffi 638 639libffi, the [Portable Foreign Function Interface Library]( 640http://sourceware.org/libffi) is required when building the Zero version of 641Hotspot. 642 643 * To install on an apt-based Linux, try running `sudo apt-get install 644 libffi-dev`. 645 * To install on an rpm-based Linux, try running `sudo yum install 646 libffi-devel`. 647 648Use `--with-libffi=<path>` if `configure` does not properly locate your libffi 649files. 650 651### libelf 652 653libelf from the [elfutils project](http://sourceware.org/elfutils) is required 654when building the AOT feature of Hotspot. 655 656 * To install on an apt-based Linux, try running `sudo apt-get install 657 libelf-dev`. 658 * To install on an rpm-based Linux, try running `sudo yum install 659 elfutils-libelf-devel`. 660 661Use `--with-libelf=<path>` if `configure` does not properly locate your libelf 662files. 663 664## Other Tooling Requirements 665 666### GNU Make 667 668OpenJDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors 669of make are supported. 670 671At least version 3.81 of GNU Make must be used. For distributions supporting 672GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful 673functionality to handle parallel building (supported by `--with-output-sync`) 674and speed and stability improvements. 675 676Note that `configure` locates and verifies a properly functioning version of 677`make` and stores the path to this `make` binary in the configuration. If you 678start a build using `make` on the command line, you will be using the version 679of make found first in your `PATH`, and not necessarily the one stored in the 680configuration. This initial make will be used as "bootstrap make", and in a 681second stage, the make located by `configure` will be called. Normally, this 682will present no issues, but if you have a very old `make`, or a non-GNU Make 683`make` in your path, this might cause issues. 684 685If you want to override the default make found by `configure`, use the `MAKE` 686configure variable, e.g. `configure MAKE=/opt/gnu/make`. 687 688On Solaris, it is common to call the GNU version of make by using `gmake`. 689 690### GNU Bash 691 692OpenJDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells 693are supported. 694 695At least version 3.2 of GNU Bash must be used. 696 697### Autoconf 698 699If you want to modify the build system itself, you need to install [Autoconf]( 700http://www.gnu.org/software/autoconf). 701 702However, if you only need to build OpenJDK or if you only edit the actual 703OpenJDK source files, there is no dependency on autoconf, since the source 704distribution includes a pre-generated `configure` shell script. 705 706See the section on [Autoconf Details](#autoconf-details) for details on how 707OpenJDK uses autoconf. This is especially important if you plan to contribute 708changes to OpenJDK that modifies the build system. 709 710## Running Configure 711 712To build OpenJDK, you need a "configuration", which consists of a directory 713where to store the build output, coupled with information about the platform, 714the specific build machine, and choices that affect how OpenJDK is built. 715 716The configuration is created by the `configure` script. The basic invocation of 717the `configure` script looks like this: 718 719``` 720bash configure [options] 721``` 722 723This will create an output directory containing the configuration and setup an 724area for the build result. This directory typically looks like 725`build/linux-x64-normal-server-release`, but the actual name depends on your 726specific configuration. (It can also be set directly, see [Using Multiple 727Configurations](#using-multiple-configurations)). This directory is referred to 728as `$BUILD` in this documentation. 729 730`configure` will try to figure out what system you are running on and where all 731necessary build components are. If you have all prerequisites for building 732installed, it should find everything. If it fails to detect any component 733automatically, it will exit and inform you about the problem. 734 735Some command line examples: 736 737 * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`: 738 ``` 739 bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32 740 ``` 741 742 * Create a debug build with the `server` JVM and DTrace enabled: 743 ``` 744 bash configure --enable-debug --with-jvm-variants=server --enable-dtrace 745 ``` 746 747### Common Configure Arguments 748 749Here follows some of the most common and important `configure` argument. 750 751To get up-to-date information on *all* available `configure` argument, please 752run: 753``` 754bash configure --help 755``` 756 757(Note that this help text also include general autoconf options, like 758`--dvidir`, that is not relevant to OpenJDK. To list only OpenJDK specific 759features, use `bash configure --help=short` instead.) 760 761#### Configure Arguments for Tailoring the Build 762 763 * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand 764 for `--with-debug-level=fastdebug`) 765 * `--with-debug-level=<level>` - Set the debug level, which can be `release`, 766 `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized` 767 is variant of `release` with additional Hotspot debug code. 768 * `--with-native-debug-symbols=<method>` - Specify if and how native debug 769 symbols should be built. Available methods are `none`, `internal`, 770 `external`, `zipped`. Default behavior depends on platform. See [Native 771 Debug Symbols](#native-debug-symbols) for more details. 772 * `--with-version-string=<string>` - Specify the version string this build 773 will be identified with. 774 * `--with-version-<part>=<value>` - A group of options, where `<part>` can be 775 any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use 776 these options to modify just the corresponding part of the version string 777 from the default, or the value provided by `--with-version-string`. 778 * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant 779 (or variants) of Hotspot. Valid variants are: `server`, `client`, 780 `minimal`, `core`, `zero`, `zeroshark`, `custom`. Note that not all 781 variants are possible to combine in a single build. 782 * `--with-jvm-features=<feature>[,<feature>...]` - Use the specified JVM 783 features when building Hotspot. The list of features will be enabled on top 784 of the default list. For the `custom` JVM variant, this default list is 785 empty. A complete list of available JVM features can be found using `bash 786 configure --help`. 787 * `--with-target-bits=<bits>` - Create a target binary suitable for running 788 on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build 789 platform, instead of doing a full cross-compile. (This is known as a 790 *reduced* build.) 791 792#### Configure Arguments for Native Compilation 793 794 * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources 795 * `--with-sysroot=<path>` - Use this directory as sysroot 796 * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the 797 default path when searching for all kinds of binaries 798 * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when 799 searching for toolchain binaries (compilers etc) 800 * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C 801 files 802 * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++ 803 files 804 * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK 805 libraries 806 807#### Configure Arguments for External Dependencies 808 809 * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK]( 810 #boot-jdk-requirements) 811 * `--with-freetype=<path>` - Set the path to [FreeType](#freetype) 812 * `--with-cups=<path>` - Set the path to [CUPS](#cups) 813 * `--with-x=<path>` - Set the path to [X11](#x11) 814 * `--with-alsa=<path>` - Set the path to [ALSA](#alsa) 815 * `--with-libffi=<path>` - Set the path to [libffi](#libffi) 816 * `--with-libelf=<path>` - Set the path to [libelf](#libelf) 817 * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests]( 818 #running-tests) 819 820Certain third-party libraries used by OpenJDK (libjpeg, giflib, libpng, lcms 821and zlib) are included in the OpenJDK repository. The default behavior of the 822OpenJDK build is to use this version of these libraries, but they might be 823replaced by an external version. To do so, specify `system` as the `<source>` 824option in these arguments. (The default is `bundled`). 825 826 * `--with-libjpeg=<source>` - Use the specified source for libjpeg 827 * `--with-giflib=<source>` - Use the specified source for giflib 828 * `--with-libpng=<source>` - Use the specified source for libpng 829 * `--with-lcms=<source>` - Use the specified source for lcms 830 * `--with-zlib=<source>` - Use the specified source for zlib 831 832On Linux, it is possible to select either static or dynamic linking of the C++ 833runtime. The default is static linking, with dynamic linking as fallback if the 834static library is not found. 835 836 * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic` 837 or `default`) for linking the C++ runtime. 838 839### Configure Control Variables 840 841It is possible to control certain aspects of `configure` by overriding the 842value of `configure` variables, either on the command line or in the 843environment. 844 845Normally, this is **not recommended**. If used improperly, it can lead to a 846broken configuration. Unless you're well versed in the build system, this is 847hard to use properly. Therefore, `configure` will print a warning if this is 848detected. 849 850However, there are a few `configure` variables, known as *control variables* 851that are supposed to be overriden on the command line. These are variables that 852describe the location of tools needed by the build, like `MAKE` or `GREP`. If 853any such variable is specified, `configure` will use that value instead of 854trying to autodetect the tool. For instance, `bash configure 855MAKE=/opt/gnumake4.0/bin/make`. 856 857If a configure argument exists, use that instead, e.g. use `--with-jtreg` 858instead of setting `JTREGEXE`. 859 860Also note that, despite what autoconf claims, setting `CFLAGS` will not 861accomplish anything. Instead use `--with-extra-cflags` (and similar for 862`cxxflags` and `ldflags`). 863 864## Running Make 865 866When you have a proper configuration, all you need to do to build OpenJDK is to 867run `make`. (But see the warning at [GNU Make](#gnu-make) about running the 868correct version of make.) 869 870When running `make` without any arguments, the default target is used, which is 871the same as running `make default` or `make jdk`. This will build a minimal (or 872roughly minimal) set of compiled output (known as an "exploded image") needed 873for a developer to actually execute the newly built JDK. The idea is that in an 874incremental development fashion, when doing a normal make, you should only 875spend time recompiling what's changed (making it purely incremental) and only 876do the work that's needed to actually run and test your code. 877 878The output of the exploded image resides in `$BUILD/jdk`. You can test the 879newly built JDK like this: `$BUILD/jdk/bin/java -version`. 880 881### Common Make Targets 882 883Apart from the default target, here are some common make targets: 884 885 * `hotspot` - Build all of hotspot (but only hotspot) 886 * `hotspot-<variant>` - Build just the specified jvm variant 887 * `images` or `product-images` - Build the JRE and JDK images 888 * `docs` or `docs-image` - Build the documentation image 889 * `test-image` - Build the test image 890 * `all` or `all-images` - Build all images (product, docs and test) 891 * `bootcycle-images` - Build images twice, second time with newly built JDK 892 (good for testing) 893 * `clean` - Remove all files generated by make, but not those generated by 894 configure 895 * `dist-clean` - Remove all files, including configuration 896 897Run `make help` to get an up-to-date list of important make targets and make 898control variables. 899 900It is possible to build just a single module, a single phase, or a single phase 901of a single module, by creating make targets according to these followin 902patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`, 903`launchers`, `libs` or `rmic`. See [Using Fine-Grained Make Targets]( 904#using-fine-grained-make-targets) for more details about this functionality. 905 906 * `<phase>` - Build the specified phase and everything it depends on 907 * `<module>` - Build the specified module and everything it depends on 908 * `<module>-<phase>` - Compile the specified phase for the specified module 909 and everything it depends on 910 911Similarly, it is possible to clean just a part of the build by creating make 912targets according to these patterns: 913 914 * `clean-<outputdir>` - Remove the subdir in the output dir with the name 915 * `clean-<phase>` - Remove all build results related to a certain build 916 phase 917 * `clean-<module>` - Remove all build results related to a certain module 918 * `clean-<module>-<phase>` - Remove all build results related to a certain 919 module and phase 920 921### Make Control Variables 922 923It is possible to control `make` behavior by overriding the value of `make` 924variables, either on the command line or in the environment. 925 926Normally, this is **not recommended**. If used improperly, it can lead to a 927broken build. Unless you're well versed in the build system, this is hard to 928use properly. Therefore, `make` will print a warning if this is detected. 929 930However, there are a few `make` variables, known as *control variables* that 931are supposed to be overriden on the command line. These make up the "make time" 932configuration, as opposed to the "configure time" configuration. 933 934#### General Make Control Variables 935 936 * `JOBS` - Specify the number of jobs to build with. See [Build 937 Performance](#build-performance). 938 * `LOG` - Specify the logging level and functionality. See [Checking the 939 Build Log File](#checking-the-build-log-file) 940 * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using 941 Multiple Configurations](#using-multiple-configurations) 942 943#### Test Make Control Variables 944 945These make control variables only make sense when running tests. Please see 946[Testing OpenJDK](testing.html) for details. 947 948 * `TEST` 949 * `TEST_JOBS` 950 * `JTREG` 951 * `GTEST` 952 953#### Advanced Make Control Variables 954 955These advanced make control variables can be potentially unsafe. See [Hints and 956Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and 957[Understanding the Build System](#understanding-the-build-system) for details. 958 959 * `SPEC` 960 * `CONF_CHECK` 961 * `COMPARE_BUILD` 962 * `JDK_FILTER` 963 964## Running Tests 965 966Most of the OpenJDK tests are using the [JTReg](http://openjdk.java.net/jtreg) 967test framework. Make sure that your configuration knows where to find your 968installation of JTReg. If this is not picked up automatically, use the 969`--with-jtreg=<path to jtreg home>` option to point to the JTReg framework. 970Note that this option should point to the JTReg home, i.e. the top directory, 971containing `lib/jtreg.jar` etc. 972 973To execute the most basic tests (tier 1), use: 974``` 975make run-test-tier1 976``` 977 978For more details on how to run tests, please see the [Testing 979OpenJDK](testing.html) document. 980 981## Cross-compiling 982 983Cross-compiling means using one platform (the *build* platform) to generate 984output that can ran on another platform (the *target* platform). 985 986The typical reason for cross-compiling is that the build is performed on a more 987powerful desktop computer, but the resulting binaries will be able to run on a 988different, typically low-performing system. Most of the complications that 989arise when building for embedded is due to this separation of *build* and 990*target* systems. 991 992This requires a more complex setup and build procedure. This section assumes 993you are familiar with cross-compiling in general, and will only deal with the 994particularities of cross-compiling OpenJDK. If you are new to cross-compiling, 995please see the [external links at Wikipedia]( 996https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start 997on reading materials. 998 999Cross-compiling OpenJDK requires you to be able to build both for the build 1000platform and for the target platform. The reason for the former is that we need 1001to build and execute tools during the build process, both native tools and Java 1002tools. 1003 1004If all you want to do is to compile a 32-bit version, for the same OS, on a 100564-bit machine, consider using `--with-target-bits=32` instead of doing a 1006full-blown cross-compilation. (While this surely is possible, it's a lot more 1007work and will take much longer to build.) 1008 1009### Boot JDK and Build JDK 1010 1011When cross-compiling, make sure you use a boot JDK that runs on the *build* 1012system, and not on the *target* system. 1013 1014To be able to build, we need a "Build JDK", which is a JDK built from the 1015current sources (that is, the same as the end result of the entire build 1016process), but able to run on the *build* system, and not the *target* system. 1017(In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when 1018building JDK 9.) 1019 1020The build process will create a minimal Build JDK for you, as part of building. 1021To speed up the build, you can use `--with-build-jdk` to `configure` to point 1022to a pre-built Build JDK. Please note that the build result is unpredictable, 1023and can possibly break in subtle ways, if the Build JDK does not **exactly** 1024match the current sources. 1025 1026### Specifying the Target Platform 1027 1028You *must* specify the target platform when cross-compiling. Doing so will also 1029automatically turn the build into a cross-compiling mode. The simplest way to 1030do this is to use the `--openjdk-target` argument, e.g. 1031`--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`. 1032This will automatically set the `--build`, `--host` and `--target` options for 1033autoconf, which can otherwise be confusing. (In autoconf terminology, the 1034"target" is known as "host", and "target" is used for building a Canadian 1035cross-compiler.) 1036 1037### Toolchain Considerations 1038 1039You will need two copies of your toolchain, one which generates output that can 1040run on the target system (the normal, or *target*, toolchain), and one that 1041generates output that can run on the build system (the *build* toolchain). Note 1042that cross-compiling is only supported for gcc at the time being. The gcc 1043standard is to prefix cross-compiling toolchains with the target denominator. 1044If you follow this standard, `configure` is likely to pick up the toolchain 1045correctly. 1046 1047The *build* toolchain will be autodetected just the same way the normal 1048*build*/*target* toolchain will be autodetected when not cross-compiling. If 1049this is not what you want, or if the autodetection fails, you can specify a 1050devkit containing the *build* toolchain using `--with-build-devkit` to 1051`configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments. 1052 1053It is often helpful to locate the cross-compilation tools, headers and 1054libraries in a separate directory, outside the normal path, and point out that 1055directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and 1056appending the directory when searching for cross-compilations tools 1057(`--with-toolchain-path`). As a compact form, you can also use `--with-devkit` 1058to point to a single directory, if it is correctly setup. (See `basics.m4` for 1059details.) 1060 1061If you are unsure what toolchain and versions to use, these have been proved 1062working at the time of writing: 1063 1064 * [aarch64]( 1065https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-linux-gnu-4.8-2013.11_linux.tar.xz) 1066 * [arm 32-bit hardware floating point]( 1067https://launchpad.net/linaro-toolchain-unsupported/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux.tar.bz2) 1068 1069### Native Libraries 1070 1071You will need copies of external native libraries for the *target* system, 1072present on the *build* machine while building. 1073 1074Take care not to replace the *build* system's version of these libraries by 1075mistake, since that can render the *build* machine unusable. 1076 1077Make sure that the libraries you point to (ALSA, X11, etc) are for the 1078*target*, not the *build*, platform. 1079 1080#### ALSA 1081 1082You will need alsa libraries suitable for your *target* system. For most cases, 1083using Debian's pre-built libraries work fine. 1084 1085Note that alsa is needed even if you only want to build a headless JDK. 1086 1087 * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and 1088 search for the `libasound2` and `libasound2-dev` packages for your *target* 1089 system. Download them to /tmp. 1090 1091 * Install the libraries into the cross-compilation toolchain. For instance: 1092``` 1093cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc 1094dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb . 1095dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb . 1096``` 1097 1098 * If alsa is not properly detected by `configure`, you can point it out by 1099 `--with-alsa`. 1100 1101#### X11 1102 1103You will need X11 libraries suitable for your *target* system. For most cases, 1104using Debian's pre-built libraries work fine. 1105 1106Note that X11 is needed even if you only want to build a headless JDK. 1107 1108 * Go to [Debian Package Search](https://www.debian.org/distrib/packages), 1109 search for the following packages for your *target* system, and download them 1110 to /tmp/target-x11: 1111 * libxi 1112 * libxi-dev 1113 * x11proto-core-dev 1114 * x11proto-input-dev 1115 * x11proto-kb-dev 1116 * x11proto-render-dev 1117 * x11proto-xext-dev 1118 * libice-dev 1119 * libxrender 1120 * libxrender-dev 1121 * libsm-dev 1122 * libxt-dev 1123 * libx11 1124 * libx11-dev 1125 * libxtst 1126 * libxtst-dev 1127 * libxext 1128 * libxext-dev 1129 1130 * Install the libraries into the cross-compilation toolchain. For instance: 1131 ``` 1132 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr 1133 mkdir X11R6 1134 cd X11R6 1135 for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done 1136 mv usr/* . 1137 cd lib 1138 cp arm-linux-gnueabihf/* . 1139 ``` 1140 1141 You can ignore the following messages. These libraries are not needed to 1142 successfully complete a full JDK build. 1143 ``` 1144 cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory 1145 cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory 1146 cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory 1147 ``` 1148 1149 * If the X11 libraries are not properly detected by `configure`, you can 1150 point them out by `--with-x`. 1151 1152### Building for ARM/aarch64 1153 1154A common cross-compilation target is the ARM CPU. When building for ARM, it is 1155useful to set the ABI profile. A number of pre-defined ABI profiles are 1156available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt, 1157armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer 1158properly supported on OpenJDK. 1159 1160OpenJDK contains two different ports for the aarch64 platform, one is the 1161original aarch64 port from the [AArch64 Port Project]( 1162http://openjdk.java.net/projects/aarch64-port) and one is a 64-bit version of 1163the Oracle contributed ARM port. When targeting aarch64, by the default the 1164original aarch64 port is used. To select the Oracle ARM 64 port, use 1165`--with-cpu-port=arm64`. Also set the corresponding value (`aarch64` or 1166`arm64`) to --with-abi-profile, to ensure a consistent build. 1167 1168### Verifying the Build 1169 1170The build will end up in a directory named like 1171`build/linux-arm-normal-server-release`. 1172 1173Inside this build output directory, the `images/jdk` and `images/jre` will 1174contain the newly built JDK and JRE, respectively, for your *target* system. 1175 1176Copy these folders to your *target* system. Then you can run e.g. 1177`images/jdk/bin/java -version`. 1178 1179## Build Performance 1180 1181Building OpenJDK requires a lot of horsepower. Some of the build tools can be 1182adjusted to utilize more or less of resources such as parallel threads and 1183memory. The `configure` script analyzes your system and selects reasonable 1184values for such options based on your hardware. If you encounter resource 1185problems, such as out of memory conditions, you can modify the detected values 1186with: 1187 1188 * `--with-num-cores` -- number of cores in the build system, e.g. 1189 `--with-num-cores=8`. 1190 1191 * `--with-memory-size` -- memory (in MB) available in the build system, e.g. 1192 `--with-memory-size=1024` 1193 1194You can also specify directly the number of build jobs to use with 1195`--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag 1196to `make`. In most cases it will be ignored by the makefiles, but it can cause 1197problems for some make targets. 1198 1199It might also be necessary to specify the JVM arguments passed to the Boot JDK, 1200using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the 1201default JVM arguments passed to the Boot JDK. 1202 1203At the end of a successful execution of `configure`, you will get a performance 1204summary, indicating how well the build will perform. Here you will also get 1205performance hints. If you want to build fast, pay attention to those! 1206 1207If you want to tweak build performance, run with `make LOG=info` to get a build 1208time summary at the end of the build process. 1209 1210### Disk Speed 1211 1212If you are using network shares, e.g. via NFS, for your source code, make sure 1213the build directory is situated on local disk (e.g. by `ln -s 1214/localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely 1215high for building on a network share; close to unusable. 1216 1217Also, make sure that your build tools (including Boot JDK and toolchain) is 1218located on a local disk and not a network share. 1219 1220As has been stressed elsewhere, do use SSD for source code and build directory, 1221as well as (if possible) the build tools. 1222 1223### Virus Checking 1224 1225The use of virus checking software, especially on Windows, can *significantly* 1226slow down building of OpenJDK. If possible, turn off such software, or exclude 1227the directory containing the OpenJDK source code from on-the-fly checking. 1228 1229### Ccache 1230 1231The OpenJDK build supports building with ccache when using gcc or clang. Using 1232ccache can radically speed up compilation of native code if you often rebuild 1233the same sources. Your milage may vary however, so we recommend evaluating it 1234for yourself. To enable it, make sure it's on the path and configure with 1235`--enable-ccache`. 1236 1237### Precompiled Headers 1238 1239By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains 1240were it is properly supported (clang, gcc, and Visual Studio). Normally, this 1241speeds up the build process, but in some circumstances, it can actually slow 1242things down. 1243 1244You can experiment by disabling precompiled headers using 1245`--disable-precompiled-headers`. 1246 1247### Icecc / icecream 1248 1249[icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a 1250distributed compiler network. If you have multiple machines available for 1251building OpenJDK, you can drastically cut individual build times by utilizing 1252it. 1253 1254To use, setup an icecc network, and install icecc on the build machine. Then 1255run `configure` using `--enable-icecc`. 1256 1257### Using sjavac 1258 1259To speed up Java compilation, especially incremental compilations, you can try 1260the experimental sjavac compiler by using `--enable-sjavac`. 1261 1262### Building the Right Target 1263 1264Selecting the proper target to build can have dramatic impact on build time. 1265For normal usage, `jdk` or the default target is just fine. You only need to 1266build `images` for shipping, or if your tests require it. 1267 1268See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on 1269how to build an even smaller subset of the product. 1270 1271## Troubleshooting 1272 1273If your build fails, it can sometimes be difficult to pinpoint the problem or 1274find a proper solution. 1275 1276### Locating the Source of the Error 1277 1278When a build fails, it can be hard to pinpoint the actual cause of the error. 1279In a typical build process, different parts of the product build in parallel, 1280with the output interlaced. 1281 1282#### Build Failure Summary 1283 1284To help you, the build system will print a failure summary at the end. It looks 1285like this: 1286 1287``` 1288ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2) 1289 1290=== Output from failing command(s) repeated here === 1291* For target hotspot_variant-server_libjvm_objs_psMemoryPool.o: 1292/localhome/hg/jdk9-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type 1293 ... (rest of output omitted) 1294 1295* All command lines available in /localhome/hg/jdk9-sandbox/build/linux-x64/make-support/failure-logs. 1296=== End of repeated output === 1297 1298=== Make failed targets repeated here === 1299lib/CompileJvm.gmk:207: recipe for target '/localhome/hg/jdk9-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed 1300make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed 1301=== End of repeated output === 1302 1303Hint: Try searching the build log for the name of the first failed target. 1304Hint: If caused by a warning, try configure --disable-warnings-as-errors. 1305``` 1306 1307Let's break it down! First, the selected configuration, and the top-level 1308target you entered on the command line that caused the failure is printed. 1309 1310Then, between the `Output from failing command(s) repeated here` and `End of 1311repeated output` the first lines of output (stdout and stderr) from the actual 1312failing command is repeated. In most cases, this is the error message that 1313caused the build to fail. If multiple commands were failing (this can happen in 1314a parallel build), output from all failed commands will be printed here. 1315 1316The path to the `failure-logs` directory is printed. In this file you will find 1317a `<target>.log` file that contains the output from this command in its 1318entirety, and also a `<target>.cmd`, which contain the complete command line 1319used for running this command. You can re-run the failing command by executing 1320`. <path to failure-logs>/<target>.cmd` in your shell. 1321 1322Another way to trace the failure is to follow the chain of make targets, from 1323top-level targets to individual file targets. Between `Make failed targets 1324repeated here` and `End of repeated output` the output from make showing this 1325chain is repeated. The first failed recipe will typically contain the full path 1326to the file in question that failed to compile. Following lines will show a 1327trace of make targets why we ended up trying to compile that file. 1328 1329Finally, some hints are given on how to locate the error in the complete log. 1330In this example, we would try searching the log file for "`psMemoryPool.o`". 1331Another way to quickly locate make errors in the log is to search for "`] 1332Error`" or "`***`". 1333 1334Note that the build failure summary will only help you if the issue was a 1335compilation failure or similar. If the problem is more esoteric, or is due to 1336errors in the build machinery, you will likely get empty output logs, and `No 1337indication of failed target found` instead of the make target chain. 1338 1339#### Checking the Build Log File 1340 1341The output (stdout and stderr) from the latest build is always stored in 1342`$BUILD/build.log`. The previous build log is stored as `build.log.old`. This 1343means that it is not necessary to redirect the build output yourself if you 1344want to process it. 1345 1346You can increase the verbosity of the log file, by the `LOG` control variable 1347to `make`. If you want to see the command lines used in compilations, use 1348`LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug` 1349or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g. 1350`LOG=info,cmdlines`. The `debug` log level will show most shell commands 1351executed by make, and `trace` will show all. Beware that both these log levels 1352will produce a massive build log! 1353 1354### Fixing Unexpected Build Failures 1355 1356Most of the time, the build will fail due to incorrect changes in the source 1357code. 1358 1359Sometimes the build can fail with no apparent changes that have caused the 1360failure. If this is the first time you are building OpenJDK on this particular 1361computer, and the build fails, the problem is likely with your build 1362environment. But even if you have previously built OpenJDK with success, and it 1363now fails, your build environment might have changed (perhaps due to OS 1364upgrades or similar). But most likely, such failures are due to problems with 1365the incremental rebuild. 1366 1367#### Problems with the Build Environment 1368 1369Make sure your configuration is correct. Re-run `configure`, and look for any 1370warnings. Warnings that appear in the middle of the `configure` output is also 1371repeated at the end, after the summary. The entire log is stored in 1372`$BUILD/configure.log`. 1373 1374Verify that the summary at the end looks correct. Are you indeed using the Boot 1375JDK and native toolchain that you expect? 1376 1377By default, OpenJDK has a strict approach where warnings from the compiler is 1378considered errors which fail the build. For very new or very old compiler 1379versions, this can trigger new classes of warnings, which thus fails the build. 1380Run `configure` with `--disable-warnings-as-errors` to turn of this behavior. 1381(The warnings will still show, but not make the build fail.) 1382 1383#### Problems with Incremental Rebuilds 1384 1385Incremental rebuilds mean that when you modify part of the product, only the 1386affected parts get rebuilt. While this works great in most cases, and 1387significantly speed up the development process, from time to time complex 1388interdependencies will result in an incorrect build result. This is the most 1389common cause for unexpected build problems, together with inconsistencies 1390between the different Mercurial repositories in the forest. 1391 1392Here are a suggested list of things to try if you are having unexpected build 1393problems. Each step requires more time than the one before, so try them in 1394order. Most issues will be solved at step 1 or 2. 1395 1396 1. Make sure your forest is up-to-date 1397 1398 Run `bash get_source.sh` to make sure you have the latest version of all 1399 repositories. 1400 1401 2. Clean build results 1402 1403 The simplest way to fix incremental rebuild issues is to run `make clean`. 1404 This will remove all build results, but not the configuration or any build 1405 system support artifacts. In most cases, this will solve build errors 1406 resulting from incremental build mismatches. 1407 1408 3. Completely clean the build directory. 1409 1410 If this does not work, the next step is to run `make dist-clean`, or 1411 removing the build output directory (`$BUILD`). This will clean all 1412 generated output, including your configuration. You will need to re-run 1413 `configure` after this step. A good idea is to run `make 1414 print-configuration` before running `make dist-clean`, as this will print 1415 your current `configure` command line. Here's a way to do this: 1416 1417 ``` 1418 make print-configuration > current-configuration 1419 make dist-clean 1420 bash configure $(cat current-configuration) 1421 make 1422 ``` 1423 1424 4. Re-clone the Mercurial forest 1425 1426 Sometimes the Mercurial repositories themselves gets in a state that causes 1427 the product to be un-buildable. In such a case, the simplest solution is 1428 often the "sledgehammer approach": delete the entire forest, and re-clone 1429 it. If you have local changes, save them first to a different location 1430 using `hg export`. 1431 1432### Specific Build Issues 1433 1434#### Clock Skew 1435 1436If you get an error message like this: 1437``` 1438File 'xxx' has modification time in the future. 1439Clock skew detected. Your build may be incomplete. 1440``` 1441then the clock on your build machine is out of sync with the timestamps on the 1442source files. Other errors, apparently unrelated but in fact caused by the 1443clock skew, can occur along with the clock skew warnings. These secondary 1444errors may tend to obscure the fact that the true root cause of the problem is 1445an out-of-sync clock. 1446 1447If you see these warnings, reset the clock on the build machine, run `make 1448clean` and restart the build. 1449 1450#### Out of Memory Errors 1451 1452On Solaris, you might get an error message like this: 1453``` 1454Trouble writing out table to disk 1455``` 1456To solve this, increase the amount of swap space on your build machine. 1457 1458On Windows, you might get error messages like this: 1459``` 1460fatal error - couldn't allocate heap 1461cannot create ... Permission denied 1462spawn failed 1463``` 1464This can be a sign of a Cygwin problem. See the information about solving 1465problems in the [Cygwin](#cygwin) section. Rebooting the computer might help 1466temporarily. 1467 1468### Getting Help 1469 1470If none of the suggestions in this document helps you, or if you find what you 1471believe is a bug in the build system, please contact the Build Group by sending 1472a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net). 1473Please include the relevant parts of the configure and/or build log. 1474 1475If you need general help or advice about developing for OpenJDK, you can also 1476contact the Adoption Group. See the section on [Contributing to OpenJDK]( 1477#contributing-to-openjdk) for more information. 1478 1479## Hints and Suggestions for Advanced Users 1480 1481### Setting Up a Forest for Pushing Changes (defpath) 1482 1483To help you prepare a proper push path for a Mercurial repository, there exists 1484a useful tool known as [defpath]( 1485http://openjdk.java.net/projects/code-tools/defpath). It will help you setup a 1486proper push path for pushing changes to OpenJDK. 1487 1488Install the extension by cloning 1489`http://hg.openjdk.java.net/code-tools/defpath` and updating your `.hgrc` file. 1490Here's one way to do this: 1491 1492``` 1493cd ~ 1494mkdir hg-ext 1495cd hg-ext 1496hg clone http://hg.openjdk.java.net/code-tools/defpath 1497cat << EOT >> ~/.hgrc 1498[extensions] 1499defpath=~/hg-ext/defpath/defpath.py 1500EOT 1501``` 1502 1503You can now setup a proper push path using: 1504``` 1505hg defpath -d -u <your OpenJDK username> 1506``` 1507 1508If you also have the `trees` extension installed in Mercurial, you will 1509automatically get a `tdefpath` command, which is even more useful. By running 1510`hg tdefpath -du <username>` in the top repository of your forest, all repos 1511will get setup automatically. This is the recommended usage. 1512 1513### Bash Completion 1514 1515The `configure` and `make` commands tries to play nice with bash command-line 1516completion (using `<tab>` or `<tab><tab>`). To use this functionality, make 1517sure you enable completion in your `~/.bashrc` (see instructions for bash in 1518your operating system). 1519 1520Make completion will work out of the box, and will complete valid make targets. 1521For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`. 1522 1523The `configure` script can get completion for options, but for this to work you 1524need to help `bash` on the way. The standard way of running the script, `bash 1525configure`, will not be understood by bash completion. You need `configure` to 1526be the command to run. One way to achieve this is to add a simple helper script 1527to your path: 1528 1529``` 1530cat << EOT > /tmp/configure 1531#!/bin/bash 1532if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then 1533 echo >&2 "Abort: Trying to call configure helper recursively" 1534 exit 1 1535fi 1536 1537bash \$PWD/configure "\$@" 1538EOT 1539chmod +x /tmp/configure 1540sudo mv /tmp/configure /usr/local/bin 1541``` 1542 1543Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`. 1544 1545### Using Multiple Configurations 1546 1547You can have multiple configurations for a single source forest. When you 1548create a new configuration, run `configure --with-conf-name=<name>` to create a 1549configuration with the name `<name>`. Alternatively, you can create a directory 1550under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd 1551build/<name> && bash ../../configure`. 1552 1553Then you can build that configuration using `make CONF_NAME=<name>` or `make 1554CONF=<pattern>`, where `<pattern>` is a substring matching one or several 1555configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will 1556match *all* available configuration, so `make CONF= hotspot` will build the 1557`hotspot` target for all configurations. Alternatively, you can execute `make` 1558in the configuration directory, e.g. `cd build/<name> && make`. 1559 1560### Handling Reconfigurations 1561 1562If you update the forest and part of the configure script has changed, the 1563build system will force you to re-run `configure`. 1564 1565Most of the time, you will be fine by running `configure` again with the same 1566arguments as the last time, which can easily be performed by `make 1567reconfigure`. To simplify this, you can use the `CONF_CHECK` make control 1568variable, either as `make CONF_CHECK=auto`, or by setting an environment 1569variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc` 1570file, `make` will always run `reconfigure` automatically whenever the configure 1571script has changed. 1572 1573You can also use `CONF_CHECK=ignore` to skip the check for a needed configure 1574update. This might speed up the build, but comes at the risk of an incorrect 1575build result. This is only recommended if you know what you're doing. 1576 1577From time to time, you will also need to modify the command line to `configure` 1578due to changes. Use `make print-configure` to show the command line used for 1579your current configuration. 1580 1581### Using Fine-Grained Make Targets 1582 1583The default behavior for make is to create consistent and correct output, at 1584the expense of build speed, if necessary. 1585 1586If you are prepared to take some risk of an incorrect build, and know enough of 1587the system to understand how things build and interact, you can speed up the 1588build process considerably by instructing make to only build a portion of the 1589product. 1590 1591#### Building Individual Modules 1592 1593The safe way to use fine-grained make targets is to use the module specific 1594make targets. All source code in JDK 9 is organized so it belongs to a module, 1595e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific module, by 1596giving it as make target: `make jdk.jdwp.agent`. If the specified module 1597depends on other modules (e.g. `java.base`), those modules will be built first. 1598 1599You can also specify a set of modules, just as you can always specify a set of 1600make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi 1601jdk.crypto.ucrypto` 1602 1603#### Building Individual Module Phases 1604 1605The build process for each module is divided into separate phases. Not all 1606modules need all phases. Which are needed depends on what kind of source code 1607and other artifact the module consists of. The phases are: 1608 1609 * `gensrc` (Generate source code to compile) 1610 * `gendata` (Generate non-source code artifacts) 1611 * `copy` (Copy resource artifacts) 1612 * `java` (Compile Java code) 1613 * `launchers` (Compile native executables) 1614 * `libs` (Compile native libraries) 1615 * `rmic` (Run the `rmic` tool) 1616 1617You can build only a single phase for a module by using the notation 1618`$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`, 1619use `make java.base-gensrc`. 1620 1621Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if 1622present). Make will build all needed prerequisites before building the 1623requested phase. 1624 1625#### Skipping the Dependency Check 1626 1627When using an iterative development style with frequent quick rebuilds, the 1628dependency check made by make can take up a significant portion of the time 1629spent on the rebuild. In such cases, it can be useful to bypass the dependency 1630check in make. 1631 1632> **Note that if used incorrectly, this can lead to a broken build!** 1633 1634To achieve this, append `-only` to the build target. For instance, `make 1635jdk.jdwp.agent-java-only` will *only* build the `java` phase of the 1636`jdk.jdwp.agent` module. If the required dependencies are not present, the 1637build can fail. On the other hand, the execution time measures in milliseconds. 1638 1639A useful pattern is to build the first time normally (e.g. `make 1640jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target. 1641 1642#### Rebuilding Part of java.base (JDK\_FILTER) 1643 1644If you are modifying files in `java.base`, which is the by far largest module 1645in OpenJDK, then you need to rebuild all those files whenever a single file has 1646changed. (This inefficiency will hopefully be addressed in JDK 10.) 1647 1648As a hack, you can use the make control variable `JDK_FILTER` to specify a 1649pattern that will be used to limit the set of files being recompiled. For 1650instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods, 1651`make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation 1652to files in the `javax.crypto` package. 1653 1654### Learn About Mercurial 1655 1656To become an efficient OpenJDK developer, it is recommended that you invest in 1657learning Mercurial properly. Here are some links that can get you started: 1658 1659 * [Mercurial for git users](http://www.mercurial-scm.org/wiki/GitConcepts) 1660 * [The official Mercurial tutorial](http://www.mercurial-scm.org/wiki/Tutorial) 1661 * [hg init](http://hginit.com/) 1662 * [Mercurial: The Definitive Guide](http://hgbook.red-bean.com/read/) 1663 1664## Understanding the Build System 1665 1666This section will give you a more technical description on the details of the 1667build system. 1668 1669### Configurations 1670 1671The build system expects to find one or more configuration. These are 1672technically defined by the `spec.gmk` in a subdirectory to the `build` 1673subdirectory. The `spec.gmk` file is generated by `configure`, and contains in 1674principle the configuration (directly or by files included by `spec.gmk`). 1675 1676You can, in fact, select a configuration to build by pointing to the `spec.gmk` 1677file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`. 1678While this is not the recommended way to call `make` as a user, it is what is 1679used under the hood by the build system. 1680 1681### Build Output Structure 1682 1683The build output for a configuration will end up in `build/<configuration 1684name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory 1685contains the following important directories: 1686 1687``` 1688buildtools/ 1689configure-support/ 1690hotspot/ 1691images/ 1692jdk/ 1693make-support/ 1694support/ 1695test-results/ 1696test-support/ 1697``` 1698 1699This is what they are used for: 1700 1701 * `images`: This is the directory were the output of the `*-image` make 1702 targets end up. For instance, `make jdk-image` ends up in `images/jdk`. 1703 1704 * `jdk`: This is the "exploded image". After `make jdk`, you will be able to 1705 launch the newly built JDK by running `$BUILD/jdk/bin/java`. 1706 1707 * `test-results`: This directory contains the results from running tests. 1708 1709 * `support`: This is an area for intermediate files needed during the build, 1710 e.g. generated source code, object files and class files. Some noteworthy 1711 directories in `support` is `gensrc`, which contains the generated source 1712 code, and the `modules_*` directories, which contains the files in a 1713 per-module hierarchy that will later be collapsed into the `jdk` directory 1714 of the exploded image. 1715 1716 * `buildtools`: This is an area for tools compiled for the build platform 1717 that are used during the rest of the build. 1718 1719 * `hotspot`: This is an area for intermediate files needed when building 1720 hotspot. 1721 1722 * `configure-support`, `make-support` and `test-support`: These directories 1723 contain files that are needed by the build system for `configure`, `make` 1724 and for running tests. 1725 1726### Fixpath 1727 1728Windows path typically look like `C:\User\foo`, while Unix paths look like 1729`/home/foo`. Tools with roots from Unix often experience issues related to this 1730mismatch when running on Windows. 1731 1732In the OpenJDK build, we always use Unix paths internally, and only just before 1733calling a tool that does not understand Unix paths do we convert them to 1734Windows paths. 1735 1736This conversion is done by the `fixpath` tool, which is a small wrapper that 1737modifies unix-style paths to Windows-style paths in command lines. Fixpath is 1738compiled automatically by `configure`. 1739 1740### Native Debug Symbols 1741 1742Native libraries and executables can have debug symbol (and other debug 1743information) associated with them. How this works is very much platform 1744dependent, but a common problem is that debug symbol information takes a lot of 1745disk space, but is rarely needed by the end user. 1746 1747The OpenJDK supports different methods on how to handle debug symbols. The 1748method used is selected by `--with-native-debug-symbols`, and available methods 1749are `none`, `internal`, `external`, `zipped`. 1750 1751 * `none` means that no debug symbols will be generated during the build. 1752 1753 * `internal` means that debug symbols will be generated during the build, and 1754 they will be stored in the generated binary. 1755 1756 * `external` means that debug symbols will be generated during the build, and 1757 after the compilation, they will be moved into a separate `.debuginfo` file. 1758 (This was previously known as FDS, Full Debug Symbols). 1759 1760 * `zipped` is like `external`, but the .debuginfo file will also be zipped 1761 into a `.diz` file. 1762 1763When building for distribution, `zipped` is a good solution. Binaries built 1764with `internal` is suitable for use by developers, since they facilitate 1765debugging, but should be stripped before distributed to end users. 1766 1767### Autoconf Details 1768 1769The `configure` script is based on the autoconf framework, but in some details 1770deviate from a normal autoconf `configure` script. 1771 1772The `configure` script in the top level directory of OpenJDK is just a thin 1773wrapper that calls `common/autoconf/configure`. This in turn provides 1774functionality that is not easily expressed in the normal Autoconf framework, 1775and then calls into the core of the `configure` script, which is the 1776`common/autoconf/generated-configure.sh` file. 1777 1778As the name implies, this file is generated by Autoconf. It is checked in after 1779regeneration, to alleviate the common user to have to install Autoconf. 1780 1781The build system will detect if the Autoconf source files have changed, and 1782will trigger a regeneration of `common/autoconf/generated-configure.sh` if 1783needed. You can also manually request such an update by `bash 1784common/autoconf/autogen.sh`. 1785 1786If you make changes to the build system that requires a re-generation, note the 1787following: 1788 1789 * You must use *exactly* version 2.69 of autoconf for your patch to be 1790 accepted. This is to avoid spurious changes in the generated file. Note 1791 that Ubuntu 16.04 ships a patched version of autoconf which claims to be 1792 2.69, but is not. 1793 1794 * You do not need to include the generated file in reviews. 1795 1796 * If the generated file needs updating, the Oracle JDK closed counter-part 1797 will also need to be updated. It is very much appreciated if you ask for an 1798 Oracle engineer to sponsor your push so this can be made in tandem. 1799 1800### Developing the Build System Itself 1801 1802This section contains a few remarks about how to develop for the build system 1803itself. It is not relevant if you are only making changes in the product source 1804code. 1805 1806While technically using `make`, the make source files of the OpenJDK does not 1807resemble most other Makefiles. Instead of listing specific targets and actions 1808(perhaps using patterns), the basic modus operandi is to call a high-level 1809function (or properly, macro) from the API in `make/common`. For instance, to 1810compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module, 1811a call like this would be made: 1812 1813``` 1814$(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \ 1815 SETUP := GENERATE_OLDBYTECODE, \ 1816 SRC := $(JDK_TOPDIR)/src/jkd.foo/share/classes, \ 1817 INCLUDES := jdk/internal/foo, \ 1818 BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \ 1819)) 1820``` 1821 1822By encapsulating and expressing the high-level knowledge of *what* should be 1823done, rather than *how* it should be done (as is normal in Makefiles), we can 1824build a much more powerful and flexible build system. 1825 1826Correct dependency tracking is paramount. Sloppy dependency tracking will lead 1827to improper parallelization, or worse, race conditions. 1828 1829To test for/debug race conditions, try running `make JOBS=1` and `make 1830JOBS=100` and see if it makes any difference. (It shouldn't). 1831 1832To compare the output of two different builds and see if, and how, they differ, 1833run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two 1834builds you want to compare. 1835 1836To automatically build two consecutive versions and compare them, use 1837`COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value 1838assignments, like this: 1839``` 1840make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot 1841``` 1842See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`. 1843 1844To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`. 1845Use `JOBS=1` to avoid parallelism. 1846 1847Please check that you adhere to the [Code Conventions for the Build System]( 1848http://openjdk.java.net/groups/build/doc/code-conventions.html) before 1849submitting patches. Also see the section in [Autoconf Details]( 1850#autoconf-details) about the generated configure script. 1851 1852## Contributing to OpenJDK 1853 1854So, now you've build your OpenJDK, and made your first patch, and want to 1855contribute it back to the OpenJDK community. 1856 1857First of all: Thank you! We gladly welcome your contribution to the OpenJDK. 1858However, please bear in mind that OpenJDK is a massive project, and we must ask 1859you to follow our rules and guidelines to be able to accept your contribution. 1860 1861The official place to start is the ['How to contribute' page]( 1862http://openjdk.java.net/contribute/). There is also an official (but somewhat 1863outdated and skimpy on details) [Developer's Guide]( 1864http://openjdk.java.net/guide/). 1865 1866If this seems overwhelming to you, the Adoption Group is there to help you! A 1867good place to start is their ['New Contributor' page]( 1868https://wiki.openjdk.java.net/display/Adoption/New+Contributor), or start 1869reading the comprehensive [Getting Started Kit]( 1870https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The 1871Adoption Group will also happily answer any questions you have about 1872contributing. Contact them by [mail]( 1873http://mail.openjdk.java.net/mailman/listinfo/adoption-discuss) or [IRC]( 1874http://openjdk.java.net/irc/). 1875 1876--- 1877# Override styles from the base CSS file that are not ideal for this document. 1878header-includes: 1879 - '<style type="text/css">pre, code, tt { color: #1d6ae5; }</style>' 1880--- 1881