building.md revision 2684:99918cff846d
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 4.3. Older versions will not be accepted 396by `configure`. 397 398However, gcc 4.3 is quite old and OpenJDK is not regularly tested on this 399version, so it is recommended to use a more modern gcc. 400 401OpenJDK 9 includes patches that should allow gcc 6 to compile, but this should 402be considered experimental. 403 404In general, any version between these two should be usable. 405 406### clang 407 408The minimum accepted version of clang is 3.2. Older versions will not be 409accepted by `configure`. 410 411To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`. 412 413### Apple Xcode 414 415The oldest supported version of Xcode is 5. 416 417You will need the Xcode command lines developers tools to be able to build 418OpenJDK. (Actually, *only* the command lines tools are needed, not the IDE.) 419The simplest way to install these is to run: 420``` 421xcode-select --install 422``` 423 424It is advisable to keep an older version of Xcode for building OpenJDK when 425updating Xcode. This [blog page]( 426http://iosdevelopertips.com/xcode/install-multiple-versions-of-xcode.html) has 427good suggestions on managing multiple Xcode versions. To use a specific version 428of Xcode, use `xcode-select -s` before running `configure`, or use 429`--with-toolchain-path` to point to the version of Xcode to use, e.g. 430`configure --with-toolchain-path=/Applications/Xcode5.app/Contents/Developer/usr/bin` 431 432If you have recently (inadvertently) updated your OS and/or Xcode version, and 433OpenJDK can no longer be built, please see the section on [Problems with the 434Build Environment](#problems-with-the-build-environment), and [Getting 435Help](#getting-help) to find out if there are any recent, non-merged patches 436available for this update. 437 438### Oracle Solaris Studio 439 440The minimum accepted version of the Solaris Studio compilers is 5.13 441(corresponding to Solaris Studio 12.4). Older versions will not be accepted by 442configure. 443 444The Solaris Studio installation should contain at least these packages: 445 446 Package Version 447 -------------------------------------------------- ------------- 448 developer/solarisstudio-124/backend 12.4-1.0.6.0 449 developer/solarisstudio-124/c++ 12.4-1.0.10.0 450 developer/solarisstudio-124/cc 12.4-1.0.4.0 451 developer/solarisstudio-124/library/c++-libs 12.4-1.0.10.0 452 developer/solarisstudio-124/library/math-libs 12.4-1.0.0.1 453 developer/solarisstudio-124/library/studio-gccrt 12.4-1.0.0.1 454 developer/solarisstudio-124/studio-common 12.4-1.0.0.1 455 developer/solarisstudio-124/studio-ja 12.4-1.0.0.1 456 developer/solarisstudio-124/studio-legal 12.4-1.0.0.1 457 developer/solarisstudio-124/studio-zhCN 12.4-1.0.0.1 458 459Compiling with Solaris Studio can sometimes be finicky. This is the exact 460version used by Oracle, which worked correctly at the time of writing: 461``` 462$ cc -V 463cc: Sun C 5.13 SunOS_i386 2014/10/20 464$ CC -V 465CC: Sun C++ 5.13 SunOS_i386 151846-10 2015/10/30 466``` 467 468### Microsoft Visual Studio 469 470The minimum accepted version of Visual Studio is 2010. Older versions will not 471be accepted by `configure`. The maximum accepted version of Visual Studio is 4722013. 473 474If you have multiple versions of Visual Studio installed, `configure` will by 475default pick the latest. You can request a specific version to be used by 476setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2010`. 477 478If you get `LINK: fatal error LNK1123: failure during conversion to COFF: file 479invalid` when building using Visual Studio 2010, you have encountered 480[KB2757355](http://support.microsoft.com/kb/2757355), a bug triggered by a 481specific installation order. However, the solution suggested by the KB article 482does not always resolve the problem. See [this stackoverflow discussion]( 483https://stackoverflow.com/questions/10888391) for other suggestions. 484 485### IBM XL C/C++ 486 487The regular builds by SAP is using version 12.1, described as `IBM XL C/C++ for 488AIX, V12.1 (5765-J02, 5725-C72) Version: 12.01.0000.0017`. 489 490See the [OpenJDK PowerPC Port Status Page]( 491http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details. 492 493## Boot JDK Requirements 494 495Paradoxically, building OpenJDK requires a pre-existing JDK. This is called the 496"boot JDK". The boot JDK does not have to be OpenJDK, though. If you are 497porting OpenJDK to a new platform, chances are that there already exists 498another JDK for that platform that is usable as boot JDK. 499 500The rule of thumb is that the boot JDK for building JDK major version *N* 501should be an JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be 502suitable as boot JDK. However, OpenJDK should be able to "build itself", so an 503up-to-date build of the current OpenJDK source is an acceptable alternative. If 504you are following the *N-1* rule, make sure you got the latest update version, 505since JDK 8 GA might not be able to build JDK 9 on all platforms. 506 507If the Boot JDK is not automatically detected, or the wrong JDK is picked, use 508`--with-boot-jdk` to point to the JDK to use. 509 510### JDK 8 on Linux 511 512On apt-based distros (like Debian and Ubuntu), `sudo apt-get install 513openjdk-8-jdk` is typically enough to install OpenJDK 8. On rpm-based distros 514(like Fedora and Red Hat), try `sudo yum install java-1.8.0-openjdk-devel`. 515 516### JDK 8 on Windows 517 518No pre-compiled binaries of OpenJDK 8 are readily available for Windows at the 519time of writing. An alternative is to download the [Oracle JDK]( 520http://www.oracle.com/technetwork/java/javase/downloads). Another is the [Adopt 521OpenJDK Project](https://adoptopenjdk.net/), which publishes experimental 522prebuilt binaries for Windows. 523 524### JDK 8 on macOS 525 526No pre-compiled binaries of OpenJDK 8 are readily available for macOS at the 527time of writing. An alternative is to download the [Oracle JDK]( 528http://www.oracle.com/technetwork/java/javase/downloads), or to install it 529using `brew cask install java`. Another option is the [Adopt OpenJDK Project]( 530https://adoptopenjdk.net/), which publishes experimental prebuilt binaries for 531macOS. 532 533### JDK 8 on AIX 534 535No pre-compiled binaries of OpenJDK 8 are readily available for AIX at the 536time of writing. A starting point for working with OpenJDK on AIX is 537the [PowerPC/AIX Port Project](http://openjdk.java.net/projects/ppc-aix-port/). 538 539## External Library Requirements 540 541Different platforms require different external libraries. In general, libraries 542are not optional - that is, they are either required or not used. 543 544If a required library is not detected by `configure`, you need to provide the 545path to it. There are two forms of the `configure` arguments to point to an 546external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to 547include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise, 548but require the include files an library files to reside in a default hierarchy 549under this directory. In most cases, it works fine. 550 551As a fallback, the second version allows you to point to the include directory 552and the lib directory separately. 553 554### FreeType 555 556FreeType2 from [The FreeType Project](http://www.freetype.org/) is required on 557all platforms. At least version 2.3 is required. 558 559 * To install on an apt-based Linux, try running `sudo apt-get install 560 libcups2-dev`. 561 * To install on an rpm-based Linux, try running `sudo yum install 562 cups-devel`. 563 * To install on Solaris, try running `pkg install system/library/freetype-2`. 564 * To install on macOS, try running `brew install freetype`. 565 * To install on Windows, see [below](#building-freetype-on-windows). 566 567Use `--with-freetype=<path>` if `configure` does not properly locate your 568FreeType files. 569 570#### Building FreeType on Windows 571 572On Windows, there is no readily available compiled version of FreeType. OpenJDK 573can help you compile FreeType from source. Download the FreeType sources and 574unpack them into an arbitrary directory: 575 576``` 577wget http://download.savannah.gnu.org/releases/freetype/freetype-2.5.3.tar.gz 578tar -xzf freetype-2.5.3.tar.gz 579``` 580 581Then run `configure` with `--with-freetype-src=<freetype_src>`. This will 582automatically build the freetype library into `<freetype_src>/lib64` for 64-bit 583builds or into `<freetype_src>/lib32` for 32-bit builds. Afterwards you can 584always use `--with-freetype-include=<freetype_src>/include` and 585`--with-freetype-lib=<freetype_src>/lib[32|64]` for other builds. 586 587Alternatively you can unpack the sources like this to use the default 588directory: 589 590``` 591tar --one-top-level=$HOME/freetype --strip-components=1 -xzf freetype-2.5.3.tar.gz 592``` 593 594### CUPS 595 596CUPS, [Common UNIX Printing System](http://www.cups.org) header files are 597required on all platforms, except Windows. Often these files are provided by 598your operating system. 599 600 * To install on an apt-based Linux, try running `sudo apt-get install 601 libcups2-dev`. 602 * To install on an rpm-based Linux, try running `sudo yum install 603 cups-devel`. 604 * To install on Solaris, try running `pkg install print/cups`. 605 606Use `--with-cups=<path>` if `configure` does not properly locate your CUPS 607files. 608 609### X11 610 611Certain [X11](http://www.x.org/) libraries and include files are required on 612Linux and Solaris. 613 614 * To install on an apt-based Linux, try running `sudo apt-get install 615 libx11-dev libxext-dev libxrender-dev libxtst-dev libxt-dev`. 616 * To install on an rpm-based Linux, try running `sudo yum install 617 libXtst-devel libXt-devel libXrender-devel libXi-devel`. 618 * To install on Solaris, try running `pkg install x11/header/x11-protocols 619 x11/library/libice x11/library/libpthread-stubs x11/library/libsm 620 x11/library/libx11 x11/library/libxau x11/library/libxcb 621 x11/library/libxdmcp x11/library/libxevie x11/library/libxext 622 x11/library/libxrender x11/library/libxscrnsaver x11/library/libxtst 623 x11/library/toolkit/libxt`. 624 625Use `--with-x=<path>` if `configure` does not properly locate your X11 files. 626 627### ALSA 628 629ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is 630required on Linux. At least version 0.9.1 of ALSA is required. 631 632 * To install on an apt-based Linux, try running `sudo apt-get install 633 libasound2-dev`. 634 * To install on an rpm-based Linux, try running `sudo yum install 635 alsa-lib-devel`. 636 637Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA 638files. 639 640### libffi 641 642libffi, the [Portable Foreign Function Interface Library]( 643http://sourceware.org/libffi) is required when building the Zero version of 644Hotspot. 645 646 * To install on an apt-based Linux, try running `sudo apt-get install 647 libffi-dev`. 648 * To install on an rpm-based Linux, try running `sudo yum install 649 libffi-devel`. 650 651Use `--with-libffi=<path>` if `configure` does not properly locate your libffi 652files. 653 654### libelf 655 656libelf from the [elfutils project](http://sourceware.org/elfutils) is required 657when building the AOT feature of Hotspot. 658 659 * To install on an apt-based Linux, try running `sudo apt-get install 660 libelf-dev`. 661 * To install on an rpm-based Linux, try running `sudo yum install 662 elfutils-libelf-devel`. 663 664Use `--with-libelf=<path>` if `configure` does not properly locate your libelf 665files. 666 667## Other Tooling Requirements 668 669### GNU Make 670 671OpenJDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors 672of make are supported. 673 674At least version 3.81 of GNU Make must be used. For distributions supporting 675GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful 676functionality to handle parallel building (supported by `--with-output-sync`) 677and speed and stability improvements. 678 679Note that `configure` locates and verifies a properly functioning version of 680`make` and stores the path to this `make` binary in the configuration. If you 681start a build using `make` on the command line, you will be using the version 682of make found first in your `PATH`, and not necessarily the one stored in the 683configuration. This initial make will be used as "bootstrap make", and in a 684second stage, the make located by `configure` will be called. Normally, this 685will present no issues, but if you have a very old `make`, or a non-GNU Make 686`make` in your path, this might cause issues. 687 688If you want to override the default make found by `configure`, use the `MAKE` 689configure variable, e.g. `configure MAKE=/opt/gnu/make`. 690 691On Solaris, it is common to call the GNU version of make by using `gmake`. 692 693### GNU Bash 694 695OpenJDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells 696are supported. 697 698At least version 3.2 of GNU Bash must be used. 699 700### Autoconf 701 702If you want to modify the build system itself, you need to install [Autoconf]( 703http://www.gnu.org/software/autoconf). 704 705However, if you only need to build OpenJDK or if you only edit the actual 706OpenJDK source files, there is no dependency on autoconf, since the source 707distribution includes a pre-generated `configure` shell script. 708 709See the section on [Autoconf Details](#autoconf-details) for details on how 710OpenJDK uses autoconf. This is especially important if you plan to contribute 711changes to OpenJDK that modifies the build system. 712 713## Running Configure 714 715To build OpenJDK, you need a "configuration", which consists of a directory 716where to store the build output, coupled with information about the platform, 717the specific build machine, and choices that affect how OpenJDK is built. 718 719The configuration is created by the `configure` script. The basic invocation of 720the `configure` script looks like this: 721 722``` 723bash configure [options] 724``` 725 726This will create an output directory containing the configuration and setup an 727area for the build result. This directory typically looks like 728`build/linux-x64-normal-server-release`, but the actual name depends on your 729specific configuration. (It can also be set directly, see [Using Multiple 730Configurations](#using-multiple-configurations)). This directory is referred to 731as `$BUILD` in this documentation. 732 733`configure` will try to figure out what system you are running on and where all 734necessary build components are. If you have all prerequisites for building 735installed, it should find everything. If it fails to detect any component 736automatically, it will exit and inform you about the problem. 737 738Some command line examples: 739 740 * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`: 741 ``` 742 bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32 743 ``` 744 745 * Create a debug build with the `server` JVM and DTrace enabled: 746 ``` 747 bash configure --enable-debug --with-jvm-variants=server --enable-dtrace 748 ``` 749 750### Common Configure Arguments 751 752Here follows some of the most common and important `configure` argument. 753 754To get up-to-date information on *all* available `configure` argument, please 755run: 756``` 757bash configure --help 758``` 759 760(Note that this help text also include general autoconf options, like 761`--dvidir`, that is not relevant to OpenJDK. To list only OpenJDK specific 762features, use `bash configure --help=short` instead.) 763 764#### Configure Arguments for Tailoring the Build 765 766 * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand 767 for `--with-debug-level=fastdebug`) 768 * `--with-debug-level=<level>` - Set the debug level, which can be `release`, 769 `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized` 770 is variant of `release` with additional Hotspot debug code. 771 * `--with-native-debug-symbols=<method>` - Specify if and how native debug 772 symbols should be built. Available methods are `none`, `internal`, 773 `external`, `zipped`. Default behavior depends on platform. See [Native 774 Debug Symbols](#native-debug-symbols) for more details. 775 * `--with-version-string=<string>` - Specify the version string this build 776 will be identified with. 777 * `--with-version-<part>=<value>` - A group of options, where `<part>` can be 778 any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use 779 these options to modify just the corresponding part of the version string 780 from the default, or the value provided by `--with-version-string`. 781 * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant 782 (or variants) of Hotspot. Valid variants are: `server`, `client`, 783 `minimal`, `core`, `zero`, `zeroshark`, `custom`. Note that not all 784 variants are possible to combine in a single build. 785 * `--with-jvm-features=<feature>[,<feature>...]` - Use the specified JVM 786 features when building Hotspot. The list of features will be enabled on top 787 of the default list. For the `custom` JVM variant, this default list is 788 empty. A complete list of available JVM features can be found using `bash 789 configure --help`. 790 * `--with-target-bits=<bits>` - Create a target binary suitable for running 791 on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build 792 platform, instead of doing a full cross-compile. (This is known as a 793 *reduced* build.) 794 795#### Configure Arguments for Native Compilation 796 797 * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources 798 * `--with-sysroot=<path>` - Use this directory as sysroot 799 * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the 800 default path when searching for all kinds of binaries 801 * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when 802 searching for toolchain binaries (compilers etc) 803 * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C 804 files 805 * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++ 806 files 807 * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK 808 libraries 809 810#### Configure Arguments for External Dependencies 811 812 * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK]( 813 #boot-jdk-requirements) 814 * `--with-freetype=<path>` - Set the path to [FreeType](#freetype) 815 * `--with-cups=<path>` - Set the path to [CUPS](#cups) 816 * `--with-x=<path>` - Set the path to [X11](#x11) 817 * `--with-alsa=<path>` - Set the path to [ALSA](#alsa) 818 * `--with-libffi=<path>` - Set the path to [libffi](#libffi) 819 * `--with-libelf=<path>` - Set the path to [libelf](#libelf) 820 * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests]( 821 #running-tests) 822 823Certain third-party libraries used by OpenJDK (libjpeg, giflib, libpng, lcms 824and zlib) are included in the OpenJDK repository. The default behavior of the 825OpenJDK build is to use this version of these libraries, but they might be 826replaced by an external version. To do so, specify `system` as the `<source>` 827option in these arguments. (The default is `bundled`). 828 829 * `--with-libjpeg=<source>` - Use the specified source for libjpeg 830 * `--with-giflib=<source>` - Use the specified source for giflib 831 * `--with-libpng=<source>` - Use the specified source for libpng 832 * `--with-lcms=<source>` - Use the specified source for lcms 833 * `--with-zlib=<source>` - Use the specified source for zlib 834 835On Linux, it is possible to select either static or dynamic linking of the C++ 836runtime. The default is static linking, with dynamic linking as fallback if the 837static library is not found. 838 839 * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic` 840 or `default`) for linking the C++ runtime. 841 842### Configure Control Variables 843 844It is possible to control certain aspects of `configure` by overriding the 845value of `configure` variables, either on the command line or in the 846environment. 847 848Normally, this is **not recommended**. If used improperly, it can lead to a 849broken configuration. Unless you're well versed in the build system, this is 850hard to use properly. Therefore, `configure` will print a warning if this is 851detected. 852 853However, there are a few `configure` variables, known as *control variables* 854that are supposed to be overriden on the command line. These are variables that 855describe the location of tools needed by the build, like `MAKE` or `GREP`. If 856any such variable is specified, `configure` will use that value instead of 857trying to autodetect the tool. For instance, `bash configure 858MAKE=/opt/gnumake4.0/bin/make`. 859 860If a configure argument exists, use that instead, e.g. use `--with-jtreg` 861instead of setting `JTREGEXE`. 862 863Also note that, despite what autoconf claims, setting `CFLAGS` will not 864accomplish anything. Instead use `--with-extra-cflags` (and similar for 865`cxxflags` and `ldflags`). 866 867## Running Make 868 869When you have a proper configuration, all you need to do to build OpenJDK is to 870run `make`. (But see the warning at [GNU Make](#gnu-make) about running the 871correct version of make.) 872 873When running `make` without any arguments, the default target is used, which is 874the same as running `make default` or `make jdk`. This will build a minimal (or 875roughly minimal) set of compiled output (known as an "exploded image") needed 876for a developer to actually execute the newly built JDK. The idea is that in an 877incremental development fashion, when doing a normal make, you should only 878spend time recompiling what's changed (making it purely incremental) and only 879do the work that's needed to actually run and test your code. 880 881The output of the exploded image resides in `$BUILD/jdk`. You can test the 882newly built JDK like this: `$BUILD/jdk/bin/java -version`. 883 884### Common Make Targets 885 886Apart from the default target, here are some common make targets: 887 888 * `hotspot` - Build all of hotspot (but only hotspot) 889 * `hotspot-<variant>` - Build just the specified jvm variant 890 * `images` or `product-images` - Build the JRE and JDK images 891 * `docs` or `docs-image` - Build the documentation image 892 * `test-image` - Build the test image 893 * `all` or `all-images` - Build all images (product, docs and test) 894 * `bootcycle-images` - Build images twice, second time with newly built JDK 895 (good for testing) 896 * `clean` - Remove all files generated by make, but not those generated by 897 configure 898 * `dist-clean` - Remove all files, including configuration 899 900Run `make help` to get an up-to-date list of important make targets and make 901control variables. 902 903It is possible to build just a single module, a single phase, or a single phase 904of a single module, by creating make targets according to these followin 905patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`, 906`launchers`, `libs` or `rmic`. See [Using Fine-Grained Make Targets]( 907#using-fine-grained-make-targets) for more details about this functionality. 908 909 * `<phase>` - Build the specified phase and everything it depends on 910 * `<module>` - Build the specified module and everything it depends on 911 * `<module>-<phase>` - Compile the specified phase for the specified module 912 and everything it depends on 913 914Similarly, it is possible to clean just a part of the build by creating make 915targets according to these patterns: 916 917 * `clean-<outputdir>` - Remove the subdir in the output dir with the name 918 * `clean-<phase>` - Remove all build results related to a certain build 919 phase 920 * `clean-<module>` - Remove all build results related to a certain module 921 * `clean-<module>-<phase>` - Remove all build results related to a certain 922 module and phase 923 924### Make Control Variables 925 926It is possible to control `make` behavior by overriding the value of `make` 927variables, either on the command line or in the environment. 928 929Normally, this is **not recommended**. If used improperly, it can lead to a 930broken build. Unless you're well versed in the build system, this is hard to 931use properly. Therefore, `make` will print a warning if this is detected. 932 933However, there are a few `make` variables, known as *control variables* that 934are supposed to be overriden on the command line. These make up the "make time" 935configuration, as opposed to the "configure time" configuration. 936 937#### General Make Control Variables 938 939 * `JOBS` - Specify the number of jobs to build with. See [Build 940 Performance](#build-performance). 941 * `LOG` - Specify the logging level and functionality. See [Checking the 942 Build Log File](#checking-the-build-log-file) 943 * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using 944 Multiple Configurations](#using-multiple-configurations) 945 946#### Test Make Control Variables 947 948These make control variables only make sense when running tests. Please see 949[Testing OpenJDK](testing.html) for details. 950 951 * `TEST` 952 * `TEST_JOBS` 953 * `JTREG` 954 * `GTEST` 955 956#### Advanced Make Control Variables 957 958These advanced make control variables can be potentially unsafe. See [Hints and 959Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and 960[Understanding the Build System](#understanding-the-build-system) for details. 961 962 * `SPEC` 963 * `CONF_CHECK` 964 * `COMPARE_BUILD` 965 * `JDK_FILTER` 966 967## Running Tests 968 969Most of the OpenJDK tests are using the [JTReg](http://openjdk.java.net/jtreg) 970test framework. Make sure that your configuration knows where to find your 971installation of JTReg. If this is not picked up automatically, use the 972`--with-jtreg=<path to jtreg home>` option to point to the JTReg framework. 973Note that this option should point to the JTReg home, i.e. the top directory, 974containing `lib/jtreg.jar` etc. 975 976To execute the most basic tests (tier 1), use: 977``` 978make run-test-tier1 979``` 980 981For more details on how to run tests, please see the [Testing 982OpenJDK](testing.html) document. 983 984## Cross-compiling 985 986Cross-compiling means using one platform (the *build* platform) to generate 987output that can ran on another platform (the *target* platform). 988 989The typical reason for cross-compiling is that the build is performed on a more 990powerful desktop computer, but the resulting binaries will be able to run on a 991different, typically low-performing system. Most of the complications that 992arise when building for embedded is due to this separation of *build* and 993*target* systems. 994 995This requires a more complex setup and build procedure. This section assumes 996you are familiar with cross-compiling in general, and will only deal with the 997particularities of cross-compiling OpenJDK. If you are new to cross-compiling, 998please see the [external links at Wikipedia]( 999https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start 1000on reading materials. 1001 1002Cross-compiling OpenJDK requires you to be able to build both for the build 1003platform and for the target platform. The reason for the former is that we need 1004to build and execute tools during the build process, both native tools and Java 1005tools. 1006 1007If all you want to do is to compile a 32-bit version, for the same OS, on a 100864-bit machine, consider using `--with-target-bits=32` instead of doing a 1009full-blown cross-compilation. (While this surely is possible, it's a lot more 1010work and will take much longer to build.) 1011 1012### Boot JDK and Build JDK 1013 1014When cross-compiling, make sure you use a boot JDK that runs on the *build* 1015system, and not on the *target* system. 1016 1017To be able to build, we need a "Build JDK", which is a JDK built from the 1018current sources (that is, the same as the end result of the entire build 1019process), but able to run on the *build* system, and not the *target* system. 1020(In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when 1021building JDK 9.) 1022 1023The build process will create a minimal Build JDK for you, as part of building. 1024To speed up the build, you can use `--with-build-jdk` to `configure` to point 1025to a pre-built Build JDK. Please note that the build result is unpredictable, 1026and can possibly break in subtle ways, if the Build JDK does not **exactly** 1027match the current sources. 1028 1029### Specifying the Target Platform 1030 1031You *must* specify the target platform when cross-compiling. Doing so will also 1032automatically turn the build into a cross-compiling mode. The simplest way to 1033do this is to use the `--openjdk-target` argument, e.g. 1034`--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`. 1035This will automatically set the `--build`, `--host` and `--target` options for 1036autoconf, which can otherwise be confusing. (In autoconf terminology, the 1037"target" is known as "host", and "target" is used for building a Canadian 1038cross-compiler.) 1039 1040### Toolchain Considerations 1041 1042You will need two copies of your toolchain, one which generates output that can 1043run on the target system (the normal, or *target*, toolchain), and one that 1044generates output that can run on the build system (the *build* toolchain). Note 1045that cross-compiling is only supported for gcc at the time being. The gcc 1046standard is to prefix cross-compiling toolchains with the target denominator. 1047If you follow this standard, `configure` is likely to pick up the toolchain 1048correctly. 1049 1050The *build* toolchain will be autodetected just the same way the normal 1051*build*/*target* toolchain will be autodetected when not cross-compiling. If 1052this is not what you want, or if the autodetection fails, you can specify a 1053devkit containing the *build* toolchain using `--with-build-devkit` to 1054`configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments. 1055 1056It is often helpful to locate the cross-compilation tools, headers and 1057libraries in a separate directory, outside the normal path, and point out that 1058directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and 1059appending the directory when searching for cross-compilations tools 1060(`--with-toolchain-path`). As a compact form, you can also use `--with-devkit` 1061to point to a single directory, if it is correctly setup. (See `basics.m4` for 1062details.) 1063 1064If you are unsure what toolchain and versions to use, these have been proved 1065working at the time of writing: 1066 1067 * [aarch64]( 1068https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-linux-gnu-4.8-2013.11_linux.tar.xz) 1069 * [arm 32-bit hardware floating point]( 1070https://launchpad.net/linaro-toolchain-unsupported/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux.tar.bz2) 1071 1072### Native Libraries 1073 1074You will need copies of external native libraries for the *target* system, 1075present on the *build* machine while building. 1076 1077Take care not to replace the *build* system's version of these libraries by 1078mistake, since that can render the *build* machine unusable. 1079 1080Make sure that the libraries you point to (ALSA, X11, etc) are for the 1081*target*, not the *build*, platform. 1082 1083#### ALSA 1084 1085You will need alsa libraries suitable for your *target* system. For most cases, 1086using Debian's pre-built libraries work fine. 1087 1088Note that alsa is needed even if you only want to build a headless JDK. 1089 1090 * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and 1091 search for the `libasound2` and `libasound2-dev` packages for your *target* 1092 system. Download them to /tmp. 1093 1094 * Install the libraries into the cross-compilation toolchain. For instance: 1095``` 1096cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc 1097dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb . 1098dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb . 1099``` 1100 1101 * If alsa is not properly detected by `configure`, you can point it out by 1102 `--with-alsa`. 1103 1104#### X11 1105 1106You will need X11 libraries suitable for your *target* system. For most cases, 1107using Debian's pre-built libraries work fine. 1108 1109Note that X11 is needed even if you only want to build a headless JDK. 1110 1111 * Go to [Debian Package Search](https://www.debian.org/distrib/packages), 1112 search for the following packages for your *target* system, and download them 1113 to /tmp/target-x11: 1114 * libxi 1115 * libxi-dev 1116 * x11proto-core-dev 1117 * x11proto-input-dev 1118 * x11proto-kb-dev 1119 * x11proto-render-dev 1120 * x11proto-xext-dev 1121 * libice-dev 1122 * libxrender 1123 * libxrender-dev 1124 * libsm-dev 1125 * libxt-dev 1126 * libx11 1127 * libx11-dev 1128 * libxtst 1129 * libxtst-dev 1130 * libxext 1131 * libxext-dev 1132 1133 * Install the libraries into the cross-compilation toolchain. For instance: 1134 ``` 1135 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr 1136 mkdir X11R6 1137 cd X11R6 1138 for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done 1139 mv usr/* . 1140 cd lib 1141 cp arm-linux-gnueabihf/* . 1142 ``` 1143 1144 You can ignore the following messages. These libraries are not needed to 1145 successfully complete a full JDK build. 1146 ``` 1147 cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory 1148 cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory 1149 cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory 1150 ``` 1151 1152 * If the X11 libraries are not properly detected by `configure`, you can 1153 point them out by `--with-x`. 1154 1155### Building for ARM/aarch64 1156 1157A common cross-compilation target is the ARM CPU. When building for ARM, it is 1158useful to set the ABI profile. A number of pre-defined ABI profiles are 1159available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt, 1160armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer 1161properly supported on OpenJDK. 1162 1163OpenJDK contains two different ports for the aarch64 platform, one is the 1164original aarch64 port from the [AArch64 Port Project]( 1165http://openjdk.java.net/projects/aarch64-port) and one is a 64-bit version of 1166the Oracle contributed ARM port. When targeting aarch64, by the default the 1167original aarch64 port is used. To select the Oracle ARM 64 port, use 1168`--with-cpu-port=arm64`. Also set the corresponding value (`aarch64` or 1169`arm64`) to --with-abi-profile, to ensure a consistent build. 1170 1171### Verifying the Build 1172 1173The build will end up in a directory named like 1174`build/linux-arm-normal-server-release`. 1175 1176Inside this build output directory, the `images/jdk` and `images/jre` will 1177contain the newly built JDK and JRE, respectively, for your *target* system. 1178 1179Copy these folders to your *target* system. Then you can run e.g. 1180`images/jdk/bin/java -version`. 1181 1182## Build Performance 1183 1184Building OpenJDK requires a lot of horsepower. Some of the build tools can be 1185adjusted to utilize more or less of resources such as parallel threads and 1186memory. The `configure` script analyzes your system and selects reasonable 1187values for such options based on your hardware. If you encounter resource 1188problems, such as out of memory conditions, you can modify the detected values 1189with: 1190 1191 * `--with-num-cores` -- number of cores in the build system, e.g. 1192 `--with-num-cores=8`. 1193 1194 * `--with-memory-size` -- memory (in MB) available in the build system, e.g. 1195 `--with-memory-size=1024` 1196 1197You can also specify directly the number of build jobs to use with 1198`--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag 1199to `make`. In most cases it will be ignored by the makefiles, but it can cause 1200problems for some make targets. 1201 1202It might also be necessary to specify the JVM arguments passed to the Boot JDK, 1203using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the 1204default JVM arguments passed to the Boot JDK. 1205 1206At the end of a successful execution of `configure`, you will get a performance 1207summary, indicating how well the build will perform. Here you will also get 1208performance hints. If you want to build fast, pay attention to those! 1209 1210If you want to tweak build performance, run with `make LOG=info` to get a build 1211time summary at the end of the build process. 1212 1213### Disk Speed 1214 1215If you are using network shares, e.g. via NFS, for your source code, make sure 1216the build directory is situated on local disk (e.g. by `ln -s 1217/localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely 1218high for building on a network share; close to unusable. 1219 1220Also, make sure that your build tools (including Boot JDK and toolchain) is 1221located on a local disk and not a network share. 1222 1223As has been stressed elsewhere, do use SSD for source code and build directory, 1224as well as (if possible) the build tools. 1225 1226### Virus Checking 1227 1228The use of virus checking software, especially on Windows, can *significantly* 1229slow down building of OpenJDK. If possible, turn off such software, or exclude 1230the directory containing the OpenJDK source code from on-the-fly checking. 1231 1232### Ccache 1233 1234The OpenJDK build supports building with ccache when using gcc or clang. Using 1235ccache can radically speed up compilation of native code if you often rebuild 1236the same sources. Your milage may vary however, so we recommend evaluating it 1237for yourself. To enable it, make sure it's on the path and configure with 1238`--enable-ccache`. 1239 1240### Precompiled Headers 1241 1242By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains 1243were it is properly supported (clang, gcc, and Visual Studio). Normally, this 1244speeds up the build process, but in some circumstances, it can actually slow 1245things down. 1246 1247You can experiment by disabling precompiled headers using 1248`--disable-precompiled-headers`. 1249 1250### Icecc / icecream 1251 1252[icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a 1253distributed compiler network. If you have multiple machines available for 1254building OpenJDK, you can drastically cut individual build times by utilizing 1255it. 1256 1257To use, setup an icecc network, and install icecc on the build machine. Then 1258run `configure` using `--enable-icecc`. 1259 1260### Using sjavac 1261 1262To speed up Java compilation, especially incremental compilations, you can try 1263the experimental sjavac compiler by using `--enable-sjavac`. 1264 1265### Building the Right Target 1266 1267Selecting the proper target to build can have dramatic impact on build time. 1268For normal usage, `jdk` or the default target is just fine. You only need to 1269build `images` for shipping, or if your tests require it. 1270 1271See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on 1272how to build an even smaller subset of the product. 1273 1274## Troubleshooting 1275 1276If your build fails, it can sometimes be difficult to pinpoint the problem or 1277find a proper solution. 1278 1279### Locating the Source of the Error 1280 1281When a build fails, it can be hard to pinpoint the actual cause of the error. 1282In a typical build process, different parts of the product build in parallel, 1283with the output interlaced. 1284 1285#### Build Failure Summary 1286 1287To help you, the build system will print a failure summary at the end. It looks 1288like this: 1289 1290``` 1291ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2) 1292 1293=== Output from failing command(s) repeated here === 1294* For target hotspot_variant-server_libjvm_objs_psMemoryPool.o: 1295/localhome/hg/jdk9-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type 1296 ... (rest of output omitted) 1297 1298* All command lines available in /localhome/hg/jdk9-sandbox/build/linux-x64/make-support/failure-logs. 1299=== End of repeated output === 1300 1301=== Make failed targets repeated here === 1302lib/CompileJvm.gmk:207: recipe for target '/localhome/hg/jdk9-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed 1303make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed 1304=== End of repeated output === 1305 1306Hint: Try searching the build log for the name of the first failed target. 1307Hint: If caused by a warning, try configure --disable-warnings-as-errors. 1308``` 1309 1310Let's break it down! First, the selected configuration, and the top-level 1311target you entered on the command line that caused the failure is printed. 1312 1313Then, between the `Output from failing command(s) repeated here` and `End of 1314repeated output` the first lines of output (stdout and stderr) from the actual 1315failing command is repeated. In most cases, this is the error message that 1316caused the build to fail. If multiple commands were failing (this can happen in 1317a parallel build), output from all failed commands will be printed here. 1318 1319The path to the `failure-logs` directory is printed. In this file you will find 1320a `<target>.log` file that contains the output from this command in its 1321entirety, and also a `<target>.cmd`, which contain the complete command line 1322used for running this command. You can re-run the failing command by executing 1323`. <path to failure-logs>/<target>.cmd` in your shell. 1324 1325Another way to trace the failure is to follow the chain of make targets, from 1326top-level targets to individual file targets. Between `Make failed targets 1327repeated here` and `End of repeated output` the output from make showing this 1328chain is repeated. The first failed recipe will typically contain the full path 1329to the file in question that failed to compile. Following lines will show a 1330trace of make targets why we ended up trying to compile that file. 1331 1332Finally, some hints are given on how to locate the error in the complete log. 1333In this example, we would try searching the log file for "`psMemoryPool.o`". 1334Another way to quickly locate make errors in the log is to search for "`] 1335Error`" or "`***`". 1336 1337Note that the build failure summary will only help you if the issue was a 1338compilation failure or similar. If the problem is more esoteric, or is due to 1339errors in the build machinery, you will likely get empty output logs, and `No 1340indication of failed target found` instead of the make target chain. 1341 1342#### Checking the Build Log File 1343 1344The output (stdout and stderr) from the latest build is always stored in 1345`$BUILD/build.log`. The previous build log is stored as `build.log.old`. This 1346means that it is not necessary to redirect the build output yourself if you 1347want to process it. 1348 1349You can increase the verbosity of the log file, by the `LOG` control variable 1350to `make`. If you want to see the command lines used in compilations, use 1351`LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug` 1352or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g. 1353`LOG=info,cmdlines`. The `debug` log level will show most shell commands 1354executed by make, and `trace` will show all. Beware that both these log levels 1355will produce a massive build log! 1356 1357### Fixing Unexpected Build Failures 1358 1359Most of the time, the build will fail due to incorrect changes in the source 1360code. 1361 1362Sometimes the build can fail with no apparent changes that have caused the 1363failure. If this is the first time you are building OpenJDK on this particular 1364computer, and the build fails, the problem is likely with your build 1365environment. But even if you have previously built OpenJDK with success, and it 1366now fails, your build environment might have changed (perhaps due to OS 1367upgrades or similar). But most likely, such failures are due to problems with 1368the incremental rebuild. 1369 1370#### Problems with the Build Environment 1371 1372Make sure your configuration is correct. Re-run `configure`, and look for any 1373warnings. Warnings that appear in the middle of the `configure` output is also 1374repeated at the end, after the summary. The entire log is stored in 1375`$BUILD/configure.log`. 1376 1377Verify that the summary at the end looks correct. Are you indeed using the Boot 1378JDK and native toolchain that you expect? 1379 1380By default, OpenJDK has a strict approach where warnings from the compiler is 1381considered errors which fail the build. For very new or very old compiler 1382versions, this can trigger new classes of warnings, which thus fails the build. 1383Run `configure` with `--disable-warnings-as-errors` to turn of this behavior. 1384(The warnings will still show, but not make the build fail.) 1385 1386#### Problems with Incremental Rebuilds 1387 1388Incremental rebuilds mean that when you modify part of the product, only the 1389affected parts get rebuilt. While this works great in most cases, and 1390significantly speed up the development process, from time to time complex 1391interdependencies will result in an incorrect build result. This is the most 1392common cause for unexpected build problems, together with inconsistencies 1393between the different Mercurial repositories in the forest. 1394 1395Here are a suggested list of things to try if you are having unexpected build 1396problems. Each step requires more time than the one before, so try them in 1397order. Most issues will be solved at step 1 or 2. 1398 1399 1. Make sure your forest is up-to-date 1400 1401 Run `bash get_source.sh` to make sure you have the latest version of all 1402 repositories. 1403 1404 2. Clean build results 1405 1406 The simplest way to fix incremental rebuild issues is to run `make clean`. 1407 This will remove all build results, but not the configuration or any build 1408 system support artifacts. In most cases, this will solve build errors 1409 resulting from incremental build mismatches. 1410 1411 3. Completely clean the build directory. 1412 1413 If this does not work, the next step is to run `make dist-clean`, or 1414 removing the build output directory (`$BUILD`). This will clean all 1415 generated output, including your configuration. You will need to re-run 1416 `configure` after this step. A good idea is to run `make 1417 print-configuration` before running `make dist-clean`, as this will print 1418 your current `configure` command line. Here's a way to do this: 1419 1420 ``` 1421 make print-configuration > current-configuration 1422 make dist-clean 1423 bash configure $(cat current-configuration) 1424 make 1425 ``` 1426 1427 4. Re-clone the Mercurial forest 1428 1429 Sometimes the Mercurial repositories themselves gets in a state that causes 1430 the product to be un-buildable. In such a case, the simplest solution is 1431 often the "sledgehammer approach": delete the entire forest, and re-clone 1432 it. If you have local changes, save them first to a different location 1433 using `hg export`. 1434 1435### Specific Build Issues 1436 1437#### Clock Skew 1438 1439If you get an error message like this: 1440``` 1441File 'xxx' has modification time in the future. 1442Clock skew detected. Your build may be incomplete. 1443``` 1444then the clock on your build machine is out of sync with the timestamps on the 1445source files. Other errors, apparently unrelated but in fact caused by the 1446clock skew, can occur along with the clock skew warnings. These secondary 1447errors may tend to obscure the fact that the true root cause of the problem is 1448an out-of-sync clock. 1449 1450If you see these warnings, reset the clock on the build machine, run `make 1451clean` and restart the build. 1452 1453#### Out of Memory Errors 1454 1455On Solaris, you might get an error message like this: 1456``` 1457Trouble writing out table to disk 1458``` 1459To solve this, increase the amount of swap space on your build machine. 1460 1461On Windows, you might get error messages like this: 1462``` 1463fatal error - couldn't allocate heap 1464cannot create ... Permission denied 1465spawn failed 1466``` 1467This can be a sign of a Cygwin problem. See the information about solving 1468problems in the [Cygwin](#cygwin) section. Rebooting the computer might help 1469temporarily. 1470 1471### Getting Help 1472 1473If none of the suggestions in this document helps you, or if you find what you 1474believe is a bug in the build system, please contact the Build Group by sending 1475a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net). 1476Please include the relevant parts of the configure and/or build log. 1477 1478If you need general help or advice about developing for OpenJDK, you can also 1479contact the Adoption Group. See the section on [Contributing to OpenJDK]( 1480#contributing-to-openjdk) for more information. 1481 1482## Hints and Suggestions for Advanced Users 1483 1484### Setting Up a Forest for Pushing Changes (defpath) 1485 1486To help you prepare a proper push path for a Mercurial repository, there exists 1487a useful tool known as [defpath]( 1488http://openjdk.java.net/projects/code-tools/defpath). It will help you setup a 1489proper push path for pushing changes to OpenJDK. 1490 1491Install the extension by cloning 1492`http://hg.openjdk.java.net/code-tools/defpath` and updating your `.hgrc` file. 1493Here's one way to do this: 1494 1495``` 1496cd ~ 1497mkdir hg-ext 1498cd hg-ext 1499hg clone http://hg.openjdk.java.net/code-tools/defpath 1500cat << EOT >> ~/.hgrc 1501[extensions] 1502defpath=~/hg-ext/defpath/defpath.py 1503EOT 1504``` 1505 1506You can now setup a proper push path using: 1507``` 1508hg defpath -d -u <your OpenJDK username> 1509``` 1510 1511If you also have the `trees` extension installed in Mercurial, you will 1512automatically get a `tdefpath` command, which is even more useful. By running 1513`hg tdefpath -du <username>` in the top repository of your forest, all repos 1514will get setup automatically. This is the recommended usage. 1515 1516### Bash Completion 1517 1518The `configure` and `make` commands tries to play nice with bash command-line 1519completion (using `<tab>` or `<tab><tab>`). To use this functionality, make 1520sure you enable completion in your `~/.bashrc` (see instructions for bash in 1521your operating system). 1522 1523Make completion will work out of the box, and will complete valid make targets. 1524For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`. 1525 1526The `configure` script can get completion for options, but for this to work you 1527need to help `bash` on the way. The standard way of running the script, `bash 1528configure`, will not be understood by bash completion. You need `configure` to 1529be the command to run. One way to achieve this is to add a simple helper script 1530to your path: 1531 1532``` 1533cat << EOT > /tmp/configure 1534#!/bin/bash 1535if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then 1536 echo >&2 "Abort: Trying to call configure helper recursively" 1537 exit 1 1538fi 1539 1540bash \$PWD/configure "\$@" 1541EOT 1542chmod +x /tmp/configure 1543sudo mv /tmp/configure /usr/local/bin 1544``` 1545 1546Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`. 1547 1548### Using Multiple Configurations 1549 1550You can have multiple configurations for a single source forest. When you 1551create a new configuration, run `configure --with-conf-name=<name>` to create a 1552configuration with the name `<name>`. Alternatively, you can create a directory 1553under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd 1554build/<name> && bash ../../configure`. 1555 1556Then you can build that configuration using `make CONF_NAME=<name>` or `make 1557CONF=<pattern>`, where `<pattern>` is a substring matching one or several 1558configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will 1559match *all* available configuration, so `make CONF= hotspot` will build the 1560`hotspot` target for all configurations. Alternatively, you can execute `make` 1561in the configuration directory, e.g. `cd build/<name> && make`. 1562 1563### Handling Reconfigurations 1564 1565If you update the forest and part of the configure script has changed, the 1566build system will force you to re-run `configure`. 1567 1568Most of the time, you will be fine by running `configure` again with the same 1569arguments as the last time, which can easily be performed by `make 1570reconfigure`. To simplify this, you can use the `CONF_CHECK` make control 1571variable, either as `make CONF_CHECK=auto`, or by setting an environment 1572variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc` 1573file, `make` will always run `reconfigure` automatically whenever the configure 1574script has changed. 1575 1576You can also use `CONF_CHECK=ignore` to skip the check for a needed configure 1577update. This might speed up the build, but comes at the risk of an incorrect 1578build result. This is only recommended if you know what you're doing. 1579 1580From time to time, you will also need to modify the command line to `configure` 1581due to changes. Use `make print-configure` to show the command line used for 1582your current configuration. 1583 1584### Using Fine-Grained Make Targets 1585 1586The default behavior for make is to create consistent and correct output, at 1587the expense of build speed, if necessary. 1588 1589If you are prepared to take some risk of an incorrect build, and know enough of 1590the system to understand how things build and interact, you can speed up the 1591build process considerably by instructing make to only build a portion of the 1592product. 1593 1594#### Building Individual Modules 1595 1596The safe way to use fine-grained make targets is to use the module specific 1597make targets. All source code in JDK 9 is organized so it belongs to a module, 1598e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific module, by 1599giving it as make target: `make jdk.jdwp.agent`. If the specified module 1600depends on other modules (e.g. `java.base`), those modules will be built first. 1601 1602You can also specify a set of modules, just as you can always specify a set of 1603make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi 1604jdk.crypto.ucrypto` 1605 1606#### Building Individual Module Phases 1607 1608The build process for each module is divided into separate phases. Not all 1609modules need all phases. Which are needed depends on what kind of source code 1610and other artifact the module consists of. The phases are: 1611 1612 * `gensrc` (Generate source code to compile) 1613 * `gendata` (Generate non-source code artifacts) 1614 * `copy` (Copy resource artifacts) 1615 * `java` (Compile Java code) 1616 * `launchers` (Compile native executables) 1617 * `libs` (Compile native libraries) 1618 * `rmic` (Run the `rmic` tool) 1619 1620You can build only a single phase for a module by using the notation 1621`$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`, 1622use `make java.base-gensrc`. 1623 1624Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if 1625present). Make will build all needed prerequisites before building the 1626requested phase. 1627 1628#### Skipping the Dependency Check 1629 1630When using an iterative development style with frequent quick rebuilds, the 1631dependency check made by make can take up a significant portion of the time 1632spent on the rebuild. In such cases, it can be useful to bypass the dependency 1633check in make. 1634 1635> **Note that if used incorrectly, this can lead to a broken build!** 1636 1637To achieve this, append `-only` to the build target. For instance, `make 1638jdk.jdwp.agent-java-only` will *only* build the `java` phase of the 1639`jdk.jdwp.agent` module. If the required dependencies are not present, the 1640build can fail. On the other hand, the execution time measures in milliseconds. 1641 1642A useful pattern is to build the first time normally (e.g. `make 1643jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target. 1644 1645#### Rebuilding Part of java.base (JDK\_FILTER) 1646 1647If you are modifying files in `java.base`, which is the by far largest module 1648in OpenJDK, then you need to rebuild all those files whenever a single file has 1649changed. (This inefficiency will hopefully be addressed in JDK 10.) 1650 1651As a hack, you can use the make control variable `JDK_FILTER` to specify a 1652pattern that will be used to limit the set of files being recompiled. For 1653instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods, 1654`make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation 1655to files in the `javax.crypto` package. 1656 1657### Learn About Mercurial 1658 1659To become an efficient OpenJDK developer, it is recommended that you invest in 1660learning Mercurial properly. Here are some links that can get you started: 1661 1662 * [Mercurial for git users](http://www.mercurial-scm.org/wiki/GitConcepts) 1663 * [The official Mercurial tutorial](http://www.mercurial-scm.org/wiki/Tutorial) 1664 * [hg init](http://hginit.com/) 1665 * [Mercurial: The Definitive Guide](http://hgbook.red-bean.com/read/) 1666 1667## Understanding the Build System 1668 1669This section will give you a more technical description on the details of the 1670build system. 1671 1672### Configurations 1673 1674The build system expects to find one or more configuration. These are 1675technically defined by the `spec.gmk` in a subdirectory to the `build` 1676subdirectory. The `spec.gmk` file is generated by `configure`, and contains in 1677principle the configuration (directly or by files included by `spec.gmk`). 1678 1679You can, in fact, select a configuration to build by pointing to the `spec.gmk` 1680file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`. 1681While this is not the recommended way to call `make` as a user, it is what is 1682used under the hood by the build system. 1683 1684### Build Output Structure 1685 1686The build output for a configuration will end up in `build/<configuration 1687name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory 1688contains the following important directories: 1689 1690``` 1691buildtools/ 1692configure-support/ 1693hotspot/ 1694images/ 1695jdk/ 1696make-support/ 1697support/ 1698test-results/ 1699test-support/ 1700``` 1701 1702This is what they are used for: 1703 1704 * `images`: This is the directory were the output of the `*-image` make 1705 targets end up. For instance, `make jdk-image` ends up in `images/jdk`. 1706 1707 * `jdk`: This is the "exploded image". After `make jdk`, you will be able to 1708 launch the newly built JDK by running `$BUILD/jdk/bin/java`. 1709 1710 * `test-results`: This directory contains the results from running tests. 1711 1712 * `support`: This is an area for intermediate files needed during the build, 1713 e.g. generated source code, object files and class files. Some noteworthy 1714 directories in `support` is `gensrc`, which contains the generated source 1715 code, and the `modules_*` directories, which contains the files in a 1716 per-module hierarchy that will later be collapsed into the `jdk` directory 1717 of the exploded image. 1718 1719 * `buildtools`: This is an area for tools compiled for the build platform 1720 that are used during the rest of the build. 1721 1722 * `hotspot`: This is an area for intermediate files needed when building 1723 hotspot. 1724 1725 * `configure-support`, `make-support` and `test-support`: These directories 1726 contain files that are needed by the build system for `configure`, `make` 1727 and for running tests. 1728 1729### Fixpath 1730 1731Windows path typically look like `C:\User\foo`, while Unix paths look like 1732`/home/foo`. Tools with roots from Unix often experience issues related to this 1733mismatch when running on Windows. 1734 1735In the OpenJDK build, we always use Unix paths internally, and only just before 1736calling a tool that does not understand Unix paths do we convert them to 1737Windows paths. 1738 1739This conversion is done by the `fixpath` tool, which is a small wrapper that 1740modifies unix-style paths to Windows-style paths in command lines. Fixpath is 1741compiled automatically by `configure`. 1742 1743### Native Debug Symbols 1744 1745Native libraries and executables can have debug symbol (and other debug 1746information) associated with them. How this works is very much platform 1747dependent, but a common problem is that debug symbol information takes a lot of 1748disk space, but is rarely needed by the end user. 1749 1750The OpenJDK supports different methods on how to handle debug symbols. The 1751method used is selected by `--with-native-debug-symbols`, and available methods 1752are `none`, `internal`, `external`, `zipped`. 1753 1754 * `none` means that no debug symbols will be generated during the build. 1755 1756 * `internal` means that debug symbols will be generated during the build, and 1757 they will be stored in the generated binary. 1758 1759 * `external` means that debug symbols will be generated during the build, and 1760 after the compilation, they will be moved into a separate `.debuginfo` file. 1761 (This was previously known as FDS, Full Debug Symbols). 1762 1763 * `zipped` is like `external`, but the .debuginfo file will also be zipped 1764 into a `.diz` file. 1765 1766When building for distribution, `zipped` is a good solution. Binaries built 1767with `internal` is suitable for use by developers, since they facilitate 1768debugging, but should be stripped before distributed to end users. 1769 1770### Autoconf Details 1771 1772The `configure` script is based on the autoconf framework, but in some details 1773deviate from a normal autoconf `configure` script. 1774 1775The `configure` script in the top level directory of OpenJDK is just a thin 1776wrapper that calls `common/autoconf/configure`. This in turn provides 1777functionality that is not easily expressed in the normal Autoconf framework, 1778and then calls into the core of the `configure` script, which is the 1779`common/autoconf/generated-configure.sh` file. 1780 1781As the name implies, this file is generated by Autoconf. It is checked in after 1782regeneration, to alleviate the common user to have to install Autoconf. 1783 1784The build system will detect if the Autoconf source files have changed, and 1785will trigger a regeneration of `common/autoconf/generated-configure.sh` if 1786needed. You can also manually request such an update by `bash 1787common/autoconf/autogen.sh`. 1788 1789If you make changes to the build system that requires a re-generation, note the 1790following: 1791 1792 * You must use *exactly* version 2.69 of autoconf for your patch to be 1793 accepted. This is to avoid spurious changes in the generated file. Note 1794 that Ubuntu 16.04 ships a patched version of autoconf which claims to be 1795 2.69, but is not. 1796 1797 * You do not need to include the generated file in reviews. 1798 1799 * If the generated file needs updating, the Oracle JDK closed counter-part 1800 will also need to be updated. It is very much appreciated if you ask for an 1801 Oracle engineer to sponsor your push so this can be made in tandem. 1802 1803### Developing the Build System Itself 1804 1805This section contains a few remarks about how to develop for the build system 1806itself. It is not relevant if you are only making changes in the product source 1807code. 1808 1809While technically using `make`, the make source files of the OpenJDK does not 1810resemble most other Makefiles. Instead of listing specific targets and actions 1811(perhaps using patterns), the basic modus operandi is to call a high-level 1812function (or properly, macro) from the API in `make/common`. For instance, to 1813compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module, 1814a call like this would be made: 1815 1816``` 1817$(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \ 1818 SETUP := GENERATE_OLDBYTECODE, \ 1819 SRC := $(JDK_TOPDIR)/src/jkd.foo/share/classes, \ 1820 INCLUDES := jdk/internal/foo, \ 1821 BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \ 1822)) 1823``` 1824 1825By encapsulating and expressing the high-level knowledge of *what* should be 1826done, rather than *how* it should be done (as is normal in Makefiles), we can 1827build a much more powerful and flexible build system. 1828 1829Correct dependency tracking is paramount. Sloppy dependency tracking will lead 1830to improper parallelization, or worse, race conditions. 1831 1832To test for/debug race conditions, try running `make JOBS=1` and `make 1833JOBS=100` and see if it makes any difference. (It shouldn't). 1834 1835To compare the output of two different builds and see if, and how, they differ, 1836run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two 1837builds you want to compare. 1838 1839To automatically build two consecutive versions and compare them, use 1840`COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value 1841assignments, like this: 1842``` 1843make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot 1844``` 1845See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`. 1846 1847To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`. 1848Use `JOBS=1` to avoid parallelism. 1849 1850Please check that you adhere to the [Code Conventions for the Build System]( 1851http://openjdk.java.net/groups/build/doc/code-conventions.html) before 1852submitting patches. Also see the section in [Autoconf Details]( 1853#autoconf-details) about the generated configure script. 1854 1855## Contributing to OpenJDK 1856 1857So, now you've build your OpenJDK, and made your first patch, and want to 1858contribute it back to the OpenJDK community. 1859 1860First of all: Thank you! We gladly welcome your contribution to the OpenJDK. 1861However, please bear in mind that OpenJDK is a massive project, and we must ask 1862you to follow our rules and guidelines to be able to accept your contribution. 1863 1864The official place to start is the ['How to contribute' page]( 1865http://openjdk.java.net/contribute/). There is also an official (but somewhat 1866outdated and skimpy on details) [Developer's Guide]( 1867http://openjdk.java.net/guide/). 1868 1869If this seems overwhelming to you, the Adoption Group is there to help you! A 1870good place to start is their ['New Contributor' page]( 1871https://wiki.openjdk.java.net/display/Adoption/New+Contributor), or start 1872reading the comprehensive [Getting Started Kit]( 1873https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The 1874Adoption Group will also happily answer any questions you have about 1875contributing. Contact them by [mail]( 1876http://mail.openjdk.java.net/mailman/listinfo/adoption-discuss) or [IRC]( 1877http://openjdk.java.net/irc/). 1878 1879--- 1880# Override styles from the base CSS file that are not ideal for this document. 1881header-includes: 1882 - '<style type="text/css">pre, code, tt { color: #1d6ae5; }</style>' 1883--- 1884