1 % Building OpenJDK
2
3 ## TL;DR (Instructions for the Impatient)
4
5 If you are eager to try out building OpenJDK, these simple steps works most of
6 the time. They assume that you have installed Mercurial (and Cygwin if running
7 on 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 `hg clone http://hg.openjdk.java.net/jdk10/master`
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
31 If any of these steps failed, or if you want to know more about build
32 requirements or build functionality, please continue reading this document.
33
34 ## Introduction
35
36 OpenJDK is a complex software project. Building it requires a certain amount of
37 technical expertise, a fair number of dependencies on external software, and
38 reasonably powerful hardware.
39
40 If you just want to use OpenJDK and not build it yourself, this document is not
41 for you. See for instance [OpenJDK installation](
42 http://openjdk.java.net/install) for some methods of installing a prebuilt
43 OpenJDK.
44
45 ## Getting the Source Code
46
47 Make sure you are getting the correct version. As of JDK 10, the source is no
48 longer split into separate repositories so you only need to clone one single
49 repository. At the [OpenJDK Mercurial server](http://hg.openjdk.java.net/) you
50 can see a list of all available forests. If you want to build an older version,
51 e.g. JDK 8, it is recommended that you get the `jdk8u` forest, which contains
52 incremental updates, instead of the `jdk8` forest, which was frozen at JDK 8 GA.
53
54 If you are new to Mercurial, a good place to start is the [Mercurial Beginner's
55 Guide](http://www.mercurial-scm.org/guide). The rest of this document assumes a
56 working knowledge of Mercurial.
57
58 ### Special Considerations
59
60 For a smooth building experience, it is recommended that you follow these rules
61 on where and how to check out the source code.
62
63 * Do not check out the source code in a path which contains spaces. Chances
64 are the build will not work. This is most likely to be an issue on Windows
65 systems.
66
67 * Do not check out the source code in a path which has a very long name or is
68 nested many levels deep. Chances are you will hit an OS limitation during
69 the build.
70
71 * Put the source code on a local disk, not a network share. If possible, use
72 an SSD. The build process is very disk intensive, and having slow disk
73 access will significantly increase build times. If you need to use a
74 network share for the source code, see below for suggestions on how to keep
75 the build artifacts on a local disk.
76
77 * On Windows, extra care must be taken to make sure the [Cygwin](#cygwin)
78 environment is consistent. It is recommended that you follow this
79 procedure:
80
81 * Create the directory that is going to contain the top directory of the
82 OpenJDK clone by using the `mkdir` command in the Cygwin bash shell.
83 That is, do *not* create it using Windows Explorer. This will ensure
84 that it will have proper Cygwin attributes, and that it's children will
85 inherit those attributes.
86
87 * Do not put the OpenJDK clone in a path under your Cygwin home
88 directory. This is especially important if your user name contains
89 spaces and/or mixed upper and lower case letters.
90
91 * Clone the OpenJDK repository using the Cygwin command line `hg` client
92 as instructed in this document. That is, do *not* use another Mercurial
93 client such as TortoiseHg.
94
95 Failure to follow this procedure might result in hard-to-debug build
96 problems.
97
98 ## Build Hardware Requirements
99
100 OpenJDK is a massive project, and require machines ranging from decent to
101 powerful to be able to build in a reasonable amount of time, or to be able to
102 complete a build at all.
103
104 We *strongly* recommend usage of an SSD disk for the build, since disk speed is
105 one of the limiting factors for build performance.
106
107 ### Building on x86
108
109 At a minimum, a machine with 2-4 cores is advisable, as well as 2-4 GB of RAM.
110 (The more cores to use, the more memory you need.) At least 6 GB of free disk
111 space is required (8 GB minimum for building on Solaris).
112
113 Even for 32-bit builds, it is recommended to use a 64-bit build machine, and
114 instead create a 32-bit target using `--with-target-bits=32`.
115
116 ### Building on sparc
117
118 At a minimum, a machine with 4 cores is advisable, as well as 4 GB of RAM. (The
119 more cores to use, the more memory you need.) At least 8 GB of free disk space
120 is required.
121
122 ### Building on arm/aarch64
123
124 This is not recommended. Instead, see the section on [Cross-compiling](
125 #cross-compiling).
126
127 ## Operating System Requirements
128
129 The mainline OpenJDK project supports Linux, Solaris, macOS, AIX and Windows.
130 Support for other operating system, e.g. BSD, exists in separate "port"
131 projects.
132
133 In general, OpenJDK can be built on a wide range of versions of these operating
134 systems, but the further you deviate from what is tested on a daily basis, the
135 more likely you are to run into problems.
136
137 This table lists the OS versions used by Oracle when building JDK 9. Such
138 information is always subject to change, but this table is up to date at the
139 time of writing.
140
141 Operating system Vendor/version used
142 ----------------- -------------------------------------------------------
143 Linux Oracle Enterprise Linux 6.4 / 7.1 (using kernel 3.8.13)
144 Solaris Solaris 11.1 SRU 21.4.1 / 11.2 SRU 5.5
145 macOS Mac OS X 10.9 (Mavericks) / 10.10 (Yosemite)
146 Windows Windows Server 2012 R2
147
148 The double version numbers for Linux, Solaris and macOS is due to the hybrid
149 model used at Oracle, where header files and external libraries from an older
150 version is used when building on a more modern version of the OS.
151
152 The Build Group has a wiki page with [Supported Build Platforms](
153 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms). From
154 time to time, this is updated by the community to list successes or failures of
155 building on different platforms.
156
157 ### Windows
158
159 Windows XP is not a supported platform, but all newer Windows should be able to
160 build OpenJDK.
161
162 On Windows, it is important that you pay attention to the instructions in the
163 [Special Considerations](#special-considerations).
164
165 Windows is the only non-POSIX OS supported by OpenJDK, and as such, requires
166 some extra care. A POSIX support layer is required to build on Windows. For
167 OpenJDK 9, the only supported such layer is Cygwin. (Msys is no longer
168 supported due to a too old bash; msys2 and the new Windows Subsystem for Linux
169 (WSL) would likely be possible to support in a future version but that would
170 require a community effort to implement.)
171
172 Internally in the build system, all paths are represented as Unix-style paths,
173 e.g. `/cygdrive/c/hg/jdk9/Makefile` rather than `C:\hg\jdk9\Makefile`. This
174 rule also applies to input to the build system, e.g. in arguments to
175 `configure`. So, use `--with-freetype=/cygdrive/c/freetype` rather than
176 `--with-freetype=c:\freetype`. For details on this conversion, see the section
177 on [Fixpath](#fixpath).
178
179 #### Cygwin
180
181 A functioning [Cygwin](http://www.cygwin.com/) environment is thus required for
182 building OpenJDK on Windows. If you have a 64-bit OS, we strongly recommend
183 using the 64-bit version of Cygwin.
184
185 **Note:** Cygwin has a model of continuously updating all packages without any
186 easy way to install or revert to a specific version of a package. This means
187 that whenever you add or update a package in Cygwin, you might (inadvertently)
188 update tools that are used by the OpenJDK build process, and that can cause
189 unexpected build problems.
190
191 OpenJDK requires GNU Make 4.0 or greater on Windows. This is usually not a
192 problem, since Cygwin currently only distributes GNU Make at a version above
193 4.0.
194
195 Apart from the basic Cygwin installation, the following packages must also be
196 installed:
197
198 * `make`
199 * `zip`
200 * `unzip`
201
202 Often, you can install these packages using the following command line:
203 ```
204 <path to Cygwin setup>/setup-x86_64 -q -P make -P unzip -P zip
205 ```
206
207 Unfortunately, Cygwin can be unreliable in certain circumstances. If you
208 experience build tool crashes or strange issues when building on Windows,
209 please check the Cygwin FAQ on the ["BLODA" list](
210 https://cygwin.com/faq/faq.html#faq.using.bloda) and the section on [fork()
211 failures](https://cygwin.com/faq/faq.html#faq.using.fixing-fork-failures).
212
213 ### Solaris
214
215 See `make/devkit/solaris11.1-package-list.txt` for a list of recommended
216 packages to install when building on Solaris. The versions specified in this
217 list is the versions used by the daily builds at Oracle, and is likely to work
218 properly.
219
220 Older versions of Solaris shipped a broken version of `objcopy`. At least
221 version 2.21.1 is needed, which is provided by Solaris 11 Update 1. Objcopy is
222 needed if you want to have external debug symbols. Please make sure you are
223 using at least version 2.21.1 of objcopy, or that you disable external debug
224 symbols.
225
226 ### macOS
227
228 Apple is using a quite aggressive scheme of pushing OS updates, and coupling
229 these updates with required updates of Xcode. Unfortunately, this makes it
230 difficult for a project like OpenJDK to keep pace with a continuously updated
231 machine running macOS. See the section on [Apple Xcode](#apple-xcode) on some
232 strategies to deal with this.
233
234 It is recommended that you use at least Mac OS X 10.9 (Mavericks). At the time
235 of writing, OpenJDK has been successfully compiled on macOS versions up to
236 10.12.5 (Sierra), using XCode 8.3.2 and `--disable-warnings-as-errors`.
237
238 The standard macOS environment contains the basic tooling needed to build, but
239 for external libraries a package manager is recommended. OpenJDK uses
240 [homebrew](https://brew.sh/) in the examples, but feel free to use whatever
241 manager you want (or none).
242
243 ### Linux
244
245 It is often not much problem to build OpenJDK on Linux. The only general advice
246 is to try to use the compilers, external libraries and header files as provided
247 by your distribution.
248
249 The basic tooling is provided as part of the core operating system, but you
250 will most likely need to install developer packages.
251
252 For apt-based distributions (Debian, Ubuntu, etc), try this:
253 ```
254 sudo apt-get install build-essential
255 ```
256
257 For rpm-based distributions (Fedora, Red Hat, etc), try this:
258 ```
259 sudo yum groupinstall "Development Tools"
260 ```
261
262 ### AIX
263
264 The regular builds by SAP is using AIX version 7.1, but AIX 5.3 is also
265 supported. See the [OpenJDK PowerPC Port Status Page](
266 http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details.
267
268 ## Native Compiler (Toolchain) Requirements
269
270 Large portions of OpenJDK consists of native code, that needs to be compiled to
271 be able to run on the target platform. In theory, toolchain and operating
272 system should be independent factors, but in practice there's more or less a
273 one-to-one correlation between target operating system and toolchain.
274
275 Operating system Supported toolchain
276 ------------------ -------------------------
277 Linux gcc, clang
278 macOS Apple Xcode (using clang)
279 Solaris Oracle Solaris Studio
280 AIX IBM XL C/C++
281 Windows Microsoft Visual Studio
282
283 Please see the individual sections on the toolchains for version
284 recommendations. As a reference, these versions of the toolchains are used, at
285 the time of writing, by Oracle for the daily builds of OpenJDK. It should be
286 possible to compile OpenJDK with both older and newer versions, but the closer
287 you stay to this list, the more likely you are to compile successfully without
288 issues.
289
290 Operating system Toolchain version
291 ------------------ -------------------------------------------------------
292 Linux gcc 4.9.2
293 macOS Apple Xcode 6.3 (using clang 6.1.0)
294 Solaris Oracle Solaris Studio 12.4 (with compiler version 5.13)
295 Windows Microsoft Visual Studio 2013 update 4
296
297 ### gcc
298
299 The minimum accepted version of gcc is 4.7. Older versions will generate a warning
300 by `configure` and are unlikely to work.
301
302 OpenJDK 9 includes patches that should allow gcc 6 to compile, but this should
303 be considered experimental.
304
305 In general, any version between these two should be usable.
306
307 ### clang
308
309 The minimum accepted version of clang is 3.2. Older versions will not be
310 accepted by `configure`.
311
312 To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`.
313
314 ### Apple Xcode
315
316 The oldest supported version of Xcode is 5.
317
318 You will need the Xcode command lines developers tools to be able to build
319 OpenJDK. (Actually, *only* the command lines tools are needed, not the IDE.)
320 The simplest way to install these is to run:
321 ```
322 xcode-select --install
323 ```
324
325 It is advisable to keep an older version of Xcode for building OpenJDK when
326 updating Xcode. This [blog page](
327 http://iosdevelopertips.com/xcode/install-multiple-versions-of-xcode.html) has
328 good suggestions on managing multiple Xcode versions. To use a specific version
329 of Xcode, use `xcode-select -s` before running `configure`, or use
330 `--with-toolchain-path` to point to the version of Xcode to use, e.g.
331 `configure --with-toolchain-path=/Applications/Xcode5.app/Contents/Developer/usr/bin`
332
333 If you have recently (inadvertently) updated your OS and/or Xcode version, and
334 OpenJDK can no longer be built, please see the section on [Problems with the
335 Build Environment](#problems-with-the-build-environment), and [Getting
336 Help](#getting-help) to find out if there are any recent, non-merged patches
337 available for this update.
338
339 ### Oracle Solaris Studio
340
341 The minimum accepted version of the Solaris Studio compilers is 5.13
342 (corresponding to Solaris Studio 12.4). Older versions will not be accepted by
343 configure.
344
345 The Solaris Studio installation should contain at least these packages:
346
347 Package Version
348 -------------------------------------------------- -------------
349 developer/solarisstudio-124/backend 12.4-1.0.6.0
350 developer/solarisstudio-124/c++ 12.4-1.0.10.0
351 developer/solarisstudio-124/cc 12.4-1.0.4.0
352 developer/solarisstudio-124/library/c++-libs 12.4-1.0.10.0
353 developer/solarisstudio-124/library/math-libs 12.4-1.0.0.1
354 developer/solarisstudio-124/library/studio-gccrt 12.4-1.0.0.1
355 developer/solarisstudio-124/studio-common 12.4-1.0.0.1
356 developer/solarisstudio-124/studio-ja 12.4-1.0.0.1
357 developer/solarisstudio-124/studio-legal 12.4-1.0.0.1
358 developer/solarisstudio-124/studio-zhCN 12.4-1.0.0.1
359
360 Compiling with Solaris Studio can sometimes be finicky. This is the exact
361 version used by Oracle, which worked correctly at the time of writing:
362 ```
363 $ cc -V
364 cc: Sun C 5.13 SunOS_i386 2014/10/20
365 $ CC -V
366 CC: Sun C++ 5.13 SunOS_i386 151846-10 2015/10/30
367 ```
368
369 ### Microsoft Visual Studio
370
371 The minimum accepted version of Visual Studio is 2010. Older versions will not
372 be accepted by `configure`. The maximum accepted version of Visual Studio is
373 2013.
374
375 If you have multiple versions of Visual Studio installed, `configure` will by
376 default pick the latest. You can request a specific version to be used by
377 setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2010`.
378
379 If you get `LINK: fatal error LNK1123: failure during conversion to COFF: file
380 invalid` when building using Visual Studio 2010, you have encountered
381 [KB2757355](http://support.microsoft.com/kb/2757355), a bug triggered by a
382 specific installation order. However, the solution suggested by the KB article
383 does not always resolve the problem. See [this stackoverflow discussion](
384 https://stackoverflow.com/questions/10888391) for other suggestions.
385
386 ### IBM XL C/C++
387
388 The regular builds by SAP is using version 12.1, described as `IBM XL C/C++ for
389 AIX, V12.1 (5765-J02, 5725-C72) Version: 12.01.0000.0017`.
390
391 See the [OpenJDK PowerPC Port Status Page](
392 http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details.
393
394 ## Boot JDK Requirements
395
396 Paradoxically, building OpenJDK requires a pre-existing JDK. This is called the
397 "boot JDK". The boot JDK does not have to be OpenJDK, though. If you are
398 porting OpenJDK to a new platform, chances are that there already exists
399 another JDK for that platform that is usable as boot JDK.
400
401 The rule of thumb is that the boot JDK for building JDK major version *N*
402 should be an JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be
403 suitable as boot JDK. However, OpenJDK should be able to "build itself", so an
404 up-to-date build of the current OpenJDK source is an acceptable alternative. If
405 you are following the *N-1* rule, make sure you got the latest update version,
406 since JDK 8 GA might not be able to build JDK 9 on all platforms.
407
408 If the Boot JDK is not automatically detected, or the wrong JDK is picked, use
409 `--with-boot-jdk` to point to the JDK to use.
410
411 ### JDK 8 on Linux
412
413 On apt-based distros (like Debian and Ubuntu), `sudo apt-get install
414 openjdk-8-jdk` is typically enough to install OpenJDK 8. On rpm-based distros
415 (like Fedora and Red Hat), try `sudo yum install java-1.8.0-openjdk-devel`.
416
417 ### JDK 8 on Windows
418
419 No pre-compiled binaries of OpenJDK 8 are readily available for Windows at the
420 time of writing. An alternative is to download the [Oracle JDK](
421 http://www.oracle.com/technetwork/java/javase/downloads). Another is the [Adopt
422 OpenJDK Project](https://adoptopenjdk.net/), which publishes experimental
423 prebuilt binaries for Windows.
424
425 ### JDK 8 on macOS
426
427 No pre-compiled binaries of OpenJDK 8 are readily available for macOS at the
428 time of writing. An alternative is to download the [Oracle JDK](
429 http://www.oracle.com/technetwork/java/javase/downloads), or to install it
430 using `brew cask install java`. Another option is the [Adopt OpenJDK Project](
431 https://adoptopenjdk.net/), which publishes experimental prebuilt binaries for
432 macOS.
433
434 ### JDK 8 on AIX
435
436 No pre-compiled binaries of OpenJDK 8 are readily available for AIX at the
437 time of writing. A starting point for working with OpenJDK on AIX is
438 the [PowerPC/AIX Port Project](http://openjdk.java.net/projects/ppc-aix-port/).
439
440 ## External Library Requirements
441
442 Different platforms require different external libraries. In general, libraries
443 are not optional - that is, they are either required or not used.
444
445 If a required library is not detected by `configure`, you need to provide the
446 path to it. There are two forms of the `configure` arguments to point to an
447 external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to
448 include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise,
449 but require the include files an library files to reside in a default hierarchy
450 under this directory. In most cases, it works fine.
451
452 As a fallback, the second version allows you to point to the include directory
453 and the lib directory separately.
454
455 ### FreeType
456
457 FreeType2 from [The FreeType Project](http://www.freetype.org/) is required on
458 all platforms. At least version 2.3 is required.
459
460 * To install on an apt-based Linux, try running `sudo apt-get install
461 libcups2-dev`.
462 * To install on an rpm-based Linux, try running `sudo yum install
463 cups-devel`.
464 * To install on Solaris, try running `pkg install system/library/freetype-2`.
465 * To install on macOS, try running `brew install freetype`.
466 * To install on Windows, see [below](#building-freetype-on-windows).
467
468 Use `--with-freetype=<path>` if `configure` does not properly locate your
469 FreeType files.
470
471 #### Building FreeType on Windows
472
473 On Windows, there is no readily available compiled version of FreeType. OpenJDK
474 can help you compile FreeType from source. Download the FreeType sources and
475 unpack them into an arbitrary directory:
476
477 ```
478 wget http://download.savannah.gnu.org/releases/freetype/freetype-2.5.3.tar.gz
479 tar -xzf freetype-2.5.3.tar.gz
480 ```
481
482 Then run `configure` with `--with-freetype-src=<freetype_src>`. This will
483 automatically build the freetype library into `<freetype_src>/lib64` for 64-bit
484 builds or into `<freetype_src>/lib32` for 32-bit builds. Afterwards you can
485 always use `--with-freetype-include=<freetype_src>/include` and
486 `--with-freetype-lib=<freetype_src>/lib[32|64]` for other builds.
487
488 Alternatively you can unpack the sources like this to use the default
489 directory:
490
491 ```
492 tar --one-top-level=$HOME/freetype --strip-components=1 -xzf freetype-2.5.3.tar.gz
493 ```
494
495 ### CUPS
496
497 CUPS, [Common UNIX Printing System](http://www.cups.org) header files are
498 required on all platforms, except Windows. Often these files are provided by
499 your operating system.
500
501 * To install on an apt-based Linux, try running `sudo apt-get install
502 libcups2-dev`.
503 * To install on an rpm-based Linux, try running `sudo yum install
504 cups-devel`.
505 * To install on Solaris, try running `pkg install print/cups`.
506
507 Use `--with-cups=<path>` if `configure` does not properly locate your CUPS
508 files.
509
510 ### X11
511
512 Certain [X11](http://www.x.org/) libraries and include files are required on
513 Linux and Solaris.
514
515 * To install on an apt-based Linux, try running `sudo apt-get install
516 libx11-dev libxext-dev libxrender-dev libxtst-dev libxt-dev`.
517 * To install on an rpm-based Linux, try running `sudo yum install
518 libXtst-devel libXt-devel libXrender-devel libXi-devel`.
519 * To install on Solaris, try running `pkg install x11/header/x11-protocols
520 x11/library/libice x11/library/libpthread-stubs x11/library/libsm
521 x11/library/libx11 x11/library/libxau x11/library/libxcb
522 x11/library/libxdmcp x11/library/libxevie x11/library/libxext
523 x11/library/libxrender x11/library/libxscrnsaver x11/library/libxtst
524 x11/library/toolkit/libxt`.
525
526 Use `--with-x=<path>` if `configure` does not properly locate your X11 files.
527
528 ### ALSA
529
530 ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is
531 required on Linux. At least version 0.9.1 of ALSA is required.
532
533 * To install on an apt-based Linux, try running `sudo apt-get install
534 libasound2-dev`.
535 * To install on an rpm-based Linux, try running `sudo yum install
536 alsa-lib-devel`.
537
538 Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA
539 files.
540
541 ### libffi
542
543 libffi, the [Portable Foreign Function Interface Library](
544 http://sourceware.org/libffi) is required when building the Zero version of
545 Hotspot.
546
547 * To install on an apt-based Linux, try running `sudo apt-get install
548 libffi-dev`.
549 * To install on an rpm-based Linux, try running `sudo yum install
550 libffi-devel`.
551
552 Use `--with-libffi=<path>` if `configure` does not properly locate your libffi
553 files.
554
555 ## Other Tooling Requirements
556
557 ### GNU Make
558
559 OpenJDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors
560 of make are supported.
561
562 At least version 3.81 of GNU Make must be used. For distributions supporting
563 GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful
564 functionality to handle parallel building (supported by `--with-output-sync`)
565 and speed and stability improvements.
566
567 Note that `configure` locates and verifies a properly functioning version of
568 `make` and stores the path to this `make` binary in the configuration. If you
569 start a build using `make` on the command line, you will be using the version
570 of make found first in your `PATH`, and not necessarily the one stored in the
571 configuration. This initial make will be used as "bootstrap make", and in a
572 second stage, the make located by `configure` will be called. Normally, this
573 will present no issues, but if you have a very old `make`, or a non-GNU Make
574 `make` in your path, this might cause issues.
575
576 If you want to override the default make found by `configure`, use the `MAKE`
577 configure variable, e.g. `configure MAKE=/opt/gnu/make`.
578
579 On Solaris, it is common to call the GNU version of make by using `gmake`.
580
581 ### GNU Bash
582
583 OpenJDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells
584 are supported.
585
586 At least version 3.2 of GNU Bash must be used.
587
588 ### Autoconf
589
590 If you want to modify the build system itself, you need to install [Autoconf](
591 http://www.gnu.org/software/autoconf).
592
593 However, if you only need to build OpenJDK or if you only edit the actual
594 OpenJDK source files, there is no dependency on autoconf, since the source
595 distribution includes a pre-generated `configure` shell script.
596
597 See the section on [Autoconf Details](#autoconf-details) for details on how
598 OpenJDK uses autoconf. This is especially important if you plan to contribute
599 changes to OpenJDK that modifies the build system.
600
601 ## Running Configure
602
603 To build OpenJDK, you need a "configuration", which consists of a directory
604 where to store the build output, coupled with information about the platform,
605 the specific build machine, and choices that affect how OpenJDK is built.
606
607 The configuration is created by the `configure` script. The basic invocation of
608 the `configure` script looks like this:
609
610 ```
611 bash configure [options]
612 ```
613
614 This will create an output directory containing the configuration and setup an
615 area for the build result. This directory typically looks like
616 `build/linux-x64-normal-server-release`, but the actual name depends on your
617 specific configuration. (It can also be set directly, see [Using Multiple
618 Configurations](#using-multiple-configurations)). This directory is referred to
619 as `$BUILD` in this documentation.
620
621 `configure` will try to figure out what system you are running on and where all
622 necessary build components are. If you have all prerequisites for building
623 installed, it should find everything. If it fails to detect any component
624 automatically, it will exit and inform you about the problem.
625
626 Some command line examples:
627
628 * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`:
629 ```
630 bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32
631 ```
632
633 * Create a debug build with the `server` JVM and DTrace enabled:
634 ```
635 bash configure --enable-debug --with-jvm-variants=server --enable-dtrace
636 ```
637
638 ### Common Configure Arguments
639
640 Here follows some of the most common and important `configure` argument.
641
642 To get up-to-date information on *all* available `configure` argument, please
643 run:
644 ```
645 bash configure --help
646 ```
647
648 (Note that this help text also include general autoconf options, like
649 `--dvidir`, that is not relevant to OpenJDK. To list only OpenJDK specific
650 features, use `bash configure --help=short` instead.)
651
652 #### Configure Arguments for Tailoring the Build
653
654 * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand
655 for `--with-debug-level=fastdebug`)
656 * `--with-debug-level=<level>` - Set the debug level, which can be `release`,
657 `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized`
658 is variant of `release` with additional Hotspot debug code.
659 * `--with-native-debug-symbols=<method>` - Specify if and how native debug
660 symbols should be built. Available methods are `none`, `internal`,
661 `external`, `zipped`. Default behavior depends on platform. See [Native
662 Debug Symbols](#native-debug-symbols) for more details.
663 * `--with-version-string=<string>` - Specify the version string this build
664 will be identified with.
665 * `--with-version-<part>=<value>` - A group of options, where `<part>` can be
666 any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use
667 these options to modify just the corresponding part of the version string
668 from the default, or the value provided by `--with-version-string`.
669 * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant
670 (or variants) of Hotspot. Valid variants are: `server`, `client`,
671 `minimal`, `core`, `zero`, `custom`. Note that not all
672 variants are possible to combine in a single build.
673 * `--with-jvm-features=<feature>[,<feature>...]` - Use the specified JVM
674 features when building Hotspot. The list of features will be enabled on top
675 of the default list. For the `custom` JVM variant, this default list is
676 empty. A complete list of available JVM features can be found using `bash
677 configure --help`.
678 * `--with-target-bits=<bits>` - Create a target binary suitable for running
679 on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build
680 platform, instead of doing a full cross-compile. (This is known as a
681 *reduced* build.)
682
683 #### Configure Arguments for Native Compilation
684
685 * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources
686 * `--with-sysroot=<path>` - Use this directory as sysroot
687 * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the
688 default path when searching for all kinds of binaries
689 * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when
690 searching for toolchain binaries (compilers etc)
691 * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C
692 files
693 * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++
694 files
695 * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK
696 libraries
697
698 #### Configure Arguments for External Dependencies
699
700 * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK](
701 #boot-jdk-requirements)
702 * `--with-freetype=<path>` - Set the path to [FreeType](#freetype)
703 * `--with-cups=<path>` - Set the path to [CUPS](#cups)
704 * `--with-x=<path>` - Set the path to [X11](#x11)
705 * `--with-alsa=<path>` - Set the path to [ALSA](#alsa)
706 * `--with-libffi=<path>` - Set the path to [libffi](#libffi)
707 * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests](
708 #running-tests)
709
710 Certain third-party libraries used by OpenJDK (libjpeg, giflib, libpng, lcms
711 and zlib) are included in the OpenJDK repository. The default behavior of the
712 OpenJDK build is to use this version of these libraries, but they might be
713 replaced by an external version. To do so, specify `system` as the `<source>`
714 option in these arguments. (The default is `bundled`).
715
716 * `--with-libjpeg=<source>` - Use the specified source for libjpeg
717 * `--with-giflib=<source>` - Use the specified source for giflib
718 * `--with-libpng=<source>` - Use the specified source for libpng
719 * `--with-lcms=<source>` - Use the specified source for lcms
720 * `--with-zlib=<source>` - Use the specified source for zlib
721
722 On Linux, it is possible to select either static or dynamic linking of the C++
723 runtime. The default is static linking, with dynamic linking as fallback if the
724 static library is not found.
725
726 * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic`
727 or `default`) for linking the C++ runtime.
728
729 ### Configure Control Variables
730
731 It is possible to control certain aspects of `configure` by overriding the
732 value of `configure` variables, either on the command line or in the
733 environment.
734
735 Normally, this is **not recommended**. If used improperly, it can lead to a
736 broken configuration. Unless you're well versed in the build system, this is
737 hard to use properly. Therefore, `configure` will print a warning if this is
738 detected.
739
740 However, there are a few `configure` variables, known as *control variables*
741 that are supposed to be overriden on the command line. These are variables that
742 describe the location of tools needed by the build, like `MAKE` or `GREP`. If
743 any such variable is specified, `configure` will use that value instead of
744 trying to autodetect the tool. For instance, `bash configure
745 MAKE=/opt/gnumake4.0/bin/make`.
746
747 If a configure argument exists, use that instead, e.g. use `--with-jtreg`
748 instead of setting `JTREGEXE`.
749
750 Also note that, despite what autoconf claims, setting `CFLAGS` will not
751 accomplish anything. Instead use `--with-extra-cflags` (and similar for
752 `cxxflags` and `ldflags`).
753
754 ## Running Make
755
756 When you have a proper configuration, all you need to do to build OpenJDK is to
757 run `make`. (But see the warning at [GNU Make](#gnu-make) about running the
758 correct version of make.)
759
760 When running `make` without any arguments, the default target is used, which is
761 the same as running `make default` or `make jdk`. This will build a minimal (or
762 roughly minimal) set of compiled output (known as an "exploded image") needed
763 for a developer to actually execute the newly built JDK. The idea is that in an
764 incremental development fashion, when doing a normal make, you should only
765 spend time recompiling what's changed (making it purely incremental) and only
766 do the work that's needed to actually run and test your code.
767
768 The output of the exploded image resides in `$BUILD/jdk`. You can test the
769 newly built JDK like this: `$BUILD/jdk/bin/java -version`.
770
771 ### Common Make Targets
772
773 Apart from the default target, here are some common make targets:
774
775 * `hotspot` - Build all of hotspot (but only hotspot)
776 * `hotspot-<variant>` - Build just the specified jvm variant
777 * `images` or `product-images` - Build the JRE and JDK images
778 * `docs` or `docs-image` - Build the documentation image
779 * `test-image` - Build the test image
780 * `all` or `all-images` - Build all images (product, docs and test)
781 * `bootcycle-images` - Build images twice, second time with newly built JDK
782 (good for testing)
783 * `clean` - Remove all files generated by make, but not those generated by
784 configure
785 * `dist-clean` - Remove all files, including configuration
786
787 Run `make help` to get an up-to-date list of important make targets and make
788 control variables.
789
790 It is possible to build just a single module, a single phase, or a single phase
791 of a single module, by creating make targets according to these followin
792 patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`,
793 `launchers`, `libs` or `rmic`. See [Using Fine-Grained Make Targets](
794 #using-fine-grained-make-targets) for more details about this functionality.
795
796 * `<phase>` - Build the specified phase and everything it depends on
797 * `<module>` - Build the specified module and everything it depends on
798 * `<module>-<phase>` - Compile the specified phase for the specified module
799 and everything it depends on
800
801 Similarly, it is possible to clean just a part of the build by creating make
802 targets according to these patterns:
803
804 * `clean-<outputdir>` - Remove the subdir in the output dir with the name
805 * `clean-<phase>` - Remove all build results related to a certain build
806 phase
807 * `clean-<module>` - Remove all build results related to a certain module
808 * `clean-<module>-<phase>` - Remove all build results related to a certain
809 module and phase
810
811 ### Make Control Variables
812
813 It is possible to control `make` behavior by overriding the value of `make`
814 variables, either on the command line or in the environment.
815
816 Normally, this is **not recommended**. If used improperly, it can lead to a
817 broken build. Unless you're well versed in the build system, this is hard to
818 use properly. Therefore, `make` will print a warning if this is detected.
819
820 However, there are a few `make` variables, known as *control variables* that
821 are supposed to be overriden on the command line. These make up the "make time"
822 configuration, as opposed to the "configure time" configuration.
823
824 #### General Make Control Variables
825
826 * `JOBS` - Specify the number of jobs to build with. See [Build
827 Performance](#build-performance).
828 * `LOG` - Specify the logging level and functionality. See [Checking the
829 Build Log File](#checking-the-build-log-file)
830 * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using
831 Multiple Configurations](#using-multiple-configurations)
832
833 #### Test Make Control Variables
834
835 These make control variables only make sense when running tests. Please see
836 [Testing OpenJDK](testing.html) for details.
837
838 * `TEST`
839 * `TEST_JOBS`
840 * `JTREG`
841 * `GTEST`
842
843 #### Advanced Make Control Variables
844
845 These advanced make control variables can be potentially unsafe. See [Hints and
846 Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and
847 [Understanding the Build System](#understanding-the-build-system) for details.
848
849 * `SPEC`
850 * `CONF_CHECK`
851 * `COMPARE_BUILD`
852 * `JDK_FILTER`
853
854 ## Running Tests
855
856 Most of the OpenJDK tests are using the [JTReg](http://openjdk.java.net/jtreg)
857 test framework. Make sure that your configuration knows where to find your
858 installation of JTReg. If this is not picked up automatically, use the
859 `--with-jtreg=<path to jtreg home>` option to point to the JTReg framework.
860 Note that this option should point to the JTReg home, i.e. the top directory,
861 containing `lib/jtreg.jar` etc.
862
863 To execute the most basic tests (tier 1), use:
864 ```
865 make run-test-tier1
866 ```
867
868 For more details on how to run tests, please see the [Testing
869 OpenJDK](testing.html) document.
870
871 ## Cross-compiling
872
873 Cross-compiling means using one platform (the *build* platform) to generate
874 output that can ran on another platform (the *target* platform).
875
876 The typical reason for cross-compiling is that the build is performed on a more
877 powerful desktop computer, but the resulting binaries will be able to run on a
878 different, typically low-performing system. Most of the complications that
879 arise when building for embedded is due to this separation of *build* and
880 *target* systems.
881
882 This requires a more complex setup and build procedure. This section assumes
883 you are familiar with cross-compiling in general, and will only deal with the
884 particularities of cross-compiling OpenJDK. If you are new to cross-compiling,
885 please see the [external links at Wikipedia](
886 https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start
887 on reading materials.
888
889 Cross-compiling OpenJDK requires you to be able to build both for the build
890 platform and for the target platform. The reason for the former is that we need
891 to build and execute tools during the build process, both native tools and Java
892 tools.
893
894 If all you want to do is to compile a 32-bit version, for the same OS, on a
895 64-bit machine, consider using `--with-target-bits=32` instead of doing a
896 full-blown cross-compilation. (While this surely is possible, it's a lot more
897 work and will take much longer to build.)
898
899 ### Boot JDK and Build JDK
900
901 When cross-compiling, make sure you use a boot JDK that runs on the *build*
902 system, and not on the *target* system.
903
904 To be able to build, we need a "Build JDK", which is a JDK built from the
905 current sources (that is, the same as the end result of the entire build
906 process), but able to run on the *build* system, and not the *target* system.
907 (In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when
908 building JDK 9.)
909
910 The build process will create a minimal Build JDK for you, as part of building.
911 To speed up the build, you can use `--with-build-jdk` to `configure` to point
912 to a pre-built Build JDK. Please note that the build result is unpredictable,
913 and can possibly break in subtle ways, if the Build JDK does not **exactly**
914 match the current sources.
915
916 ### Specifying the Target Platform
917
918 You *must* specify the target platform when cross-compiling. Doing so will also
919 automatically turn the build into a cross-compiling mode. The simplest way to
920 do this is to use the `--openjdk-target` argument, e.g.
921 `--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`.
922 This will automatically set the `--build`, `--host` and `--target` options for
923 autoconf, which can otherwise be confusing. (In autoconf terminology, the
924 "target" is known as "host", and "target" is used for building a Canadian
925 cross-compiler.)
926
927 ### Toolchain Considerations
928
929 You will need two copies of your toolchain, one which generates output that can
930 run on the target system (the normal, or *target*, toolchain), and one that
931 generates output that can run on the build system (the *build* toolchain). Note
932 that cross-compiling is only supported for gcc at the time being. The gcc
933 standard is to prefix cross-compiling toolchains with the target denominator.
934 If you follow this standard, `configure` is likely to pick up the toolchain
935 correctly.
936
937 The *build* toolchain will be autodetected just the same way the normal
938 *build*/*target* toolchain will be autodetected when not cross-compiling. If
939 this is not what you want, or if the autodetection fails, you can specify a
940 devkit containing the *build* toolchain using `--with-build-devkit` to
941 `configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments.
942
943 It is often helpful to locate the cross-compilation tools, headers and
944 libraries in a separate directory, outside the normal path, and point out that
945 directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and
946 appending the directory when searching for cross-compilations tools
947 (`--with-toolchain-path`). As a compact form, you can also use `--with-devkit`
948 to point to a single directory, if it is correctly setup. (See `basics.m4` for
949 details.)
950
951 If you are unsure what toolchain and versions to use, these have been proved
952 working at the time of writing:
953
954 * [aarch64](
955 https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-linux-gnu-4.8-2013.11_linux.tar.xz)
956 * [arm 32-bit hardware floating point](
957 https://launchpad.net/linaro-toolchain-unsupported/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux.tar.bz2)
958
959 ### Native Libraries
960
961 You will need copies of external native libraries for the *target* system,
962 present on the *build* machine while building.
963
964 Take care not to replace the *build* system's version of these libraries by
965 mistake, since that can render the *build* machine unusable.
966
967 Make sure that the libraries you point to (ALSA, X11, etc) are for the
968 *target*, not the *build*, platform.
969
970 #### ALSA
971
972 You will need alsa libraries suitable for your *target* system. For most cases,
973 using Debian's pre-built libraries work fine.
974
975 Note that alsa is needed even if you only want to build a headless JDK.
976
977 * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and
978 search for the `libasound2` and `libasound2-dev` packages for your *target*
979 system. Download them to /tmp.
980
981 * Install the libraries into the cross-compilation toolchain. For instance:
982 ```
983 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc
984 dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb .
985 dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb .
986 ```
987
988 * If alsa is not properly detected by `configure`, you can point it out by
989 `--with-alsa`.
990
991 #### X11
992
993 You will need X11 libraries suitable for your *target* system. For most cases,
994 using Debian's pre-built libraries work fine.
995
996 Note that X11 is needed even if you only want to build a headless JDK.
997
998 * Go to [Debian Package Search](https://www.debian.org/distrib/packages),
999 search for the following packages for your *target* system, and download them
1000 to /tmp/target-x11:
1001 * libxi
1002 * libxi-dev
1003 * x11proto-core-dev
1004 * x11proto-input-dev
1005 * x11proto-kb-dev
1006 * x11proto-render-dev
1007 * x11proto-xext-dev
1008 * libice-dev
1009 * libxrender
1010 * libxrender-dev
1011 * libsm-dev
1012 * libxt-dev
1013 * libx11
1014 * libx11-dev
1015 * libxtst
1016 * libxtst-dev
1017 * libxext
1018 * libxext-dev
1019
1020 * Install the libraries into the cross-compilation toolchain. For instance:
1021 ```
1022 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr
1023 mkdir X11R6
1024 cd X11R6
1025 for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done
1026 mv usr/* .
1027 cd lib
1028 cp arm-linux-gnueabihf/* .
1029 ```
1030
1031 You can ignore the following messages. These libraries are not needed to
1032 successfully complete a full JDK build.
1033 ```
1034 cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory
1035 cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory
1036 cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory
1037 ```
1038
1039 * If the X11 libraries are not properly detected by `configure`, you can
1040 point them out by `--with-x`.
1041
1042 ### Building for ARM/aarch64
1043
1044 A common cross-compilation target is the ARM CPU. When building for ARM, it is
1045 useful to set the ABI profile. A number of pre-defined ABI profiles are
1046 available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt,
1047 armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer
1048 properly supported on OpenJDK.
1049
1050 OpenJDK contains two different ports for the aarch64 platform, one is the
1051 original aarch64 port from the [AArch64 Port Project](
1052 http://openjdk.java.net/projects/aarch64-port) and one is a 64-bit version of
1053 the Oracle contributed ARM port. When targeting aarch64, by the default the
1054 original aarch64 port is used. To select the Oracle ARM 64 port, use
1055 `--with-cpu-port=arm64`. Also set the corresponding value (`aarch64` or
1056 `arm64`) to --with-abi-profile, to ensure a consistent build.
1057
1058 ### Verifying the Build
1059
1060 The build will end up in a directory named like
1061 `build/linux-arm-normal-server-release`.
1062
1063 Inside this build output directory, the `images/jdk` and `images/jre` will
1064 contain the newly built JDK and JRE, respectively, for your *target* system.
1065
1066 Copy these folders to your *target* system. Then you can run e.g.
1067 `images/jdk/bin/java -version`.
1068
1069 ## Build Performance
1070
1071 Building OpenJDK requires a lot of horsepower. Some of the build tools can be
1072 adjusted to utilize more or less of resources such as parallel threads and
1073 memory. The `configure` script analyzes your system and selects reasonable
1074 values for such options based on your hardware. If you encounter resource
1075 problems, such as out of memory conditions, you can modify the detected values
1076 with:
1077
1078 * `--with-num-cores` -- number of cores in the build system, e.g.
1079 `--with-num-cores=8`.
1080
1081 * `--with-memory-size` -- memory (in MB) available in the build system, e.g.
1082 `--with-memory-size=1024`
1083
1084 You can also specify directly the number of build jobs to use with
1085 `--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag
1086 to `make`. In most cases it will be ignored by the makefiles, but it can cause
1087 problems for some make targets.
1088
1089 It might also be necessary to specify the JVM arguments passed to the Boot JDK,
1090 using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the
1091 default JVM arguments passed to the Boot JDK.
1092
1093 At the end of a successful execution of `configure`, you will get a performance
1094 summary, indicating how well the build will perform. Here you will also get
1095 performance hints. If you want to build fast, pay attention to those!
1096
1097 If you want to tweak build performance, run with `make LOG=info` to get a build
1098 time summary at the end of the build process.
1099
1100 ### Disk Speed
1101
1102 If you are using network shares, e.g. via NFS, for your source code, make sure
1103 the build directory is situated on local disk (e.g. by `ln -s
1104 /localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely
1105 high for building on a network share; close to unusable.
1106
1107 Also, make sure that your build tools (including Boot JDK and toolchain) is
1108 located on a local disk and not a network share.
1109
1110 As has been stressed elsewhere, do use SSD for source code and build directory,
1111 as well as (if possible) the build tools.
1112
1113 ### Virus Checking
1114
1115 The use of virus checking software, especially on Windows, can *significantly*
1116 slow down building of OpenJDK. If possible, turn off such software, or exclude
1117 the directory containing the OpenJDK source code from on-the-fly checking.
1118
1119 ### Ccache
1120
1121 The OpenJDK build supports building with ccache when using gcc or clang. Using
1122 ccache can radically speed up compilation of native code if you often rebuild
1123 the same sources. Your milage may vary however, so we recommend evaluating it
1124 for yourself. To enable it, make sure it's on the path and configure with
1125 `--enable-ccache`.
1126
1127 ### Precompiled Headers
1128
1129 By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains
1130 were it is properly supported (clang, gcc, and Visual Studio). Normally, this
1131 speeds up the build process, but in some circumstances, it can actually slow
1132 things down.
1133
1134 You can experiment by disabling precompiled headers using
1135 `--disable-precompiled-headers`.
1136
1137 ### Icecc / icecream
1138
1139 [icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a
1140 distributed compiler network. If you have multiple machines available for
1141 building OpenJDK, you can drastically cut individual build times by utilizing
1142 it.
1143
1144 To use, setup an icecc network, and install icecc on the build machine. Then
1145 run `configure` using `--enable-icecc`.
1146
1147 ### Using sjavac
1148
1149 To speed up Java compilation, especially incremental compilations, you can try
1150 the experimental sjavac compiler by using `--enable-sjavac`.
1151
1152 ### Building the Right Target
1153
1154 Selecting the proper target to build can have dramatic impact on build time.
1155 For normal usage, `jdk` or the default target is just fine. You only need to
1156 build `images` for shipping, or if your tests require it.
1157
1158 See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on
1159 how to build an even smaller subset of the product.
1160
1161 ## Troubleshooting
1162
1163 If your build fails, it can sometimes be difficult to pinpoint the problem or
1164 find a proper solution.
1165
1166 ### Locating the Source of the Error
1167
1168 When a build fails, it can be hard to pinpoint the actual cause of the error.
1169 In a typical build process, different parts of the product build in parallel,
1170 with the output interlaced.
1171
1172 #### Build Failure Summary
1173
1174 To help you, the build system will print a failure summary at the end. It looks
1175 like this:
1176
1177 ```
1178 ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2)
1179
1180 === Output from failing command(s) repeated here ===
1181 * For target hotspot_variant-server_libjvm_objs_psMemoryPool.o:
1182 /localhome/hg/jdk9-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type
1183 ... (rest of output omitted)
1184
1185 * All command lines available in /localhome/hg/jdk9-sandbox/build/linux-x64/make-support/failure-logs.
1186 === End of repeated output ===
1187
1188 === Make failed targets repeated here ===
1189 lib/CompileJvm.gmk:207: recipe for target '/localhome/hg/jdk9-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed
1190 make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed
1191 === End of repeated output ===
1192
1193 Hint: Try searching the build log for the name of the first failed target.
1194 Hint: If caused by a warning, try configure --disable-warnings-as-errors.
1195 ```
1196
1197 Let's break it down! First, the selected configuration, and the top-level
1198 target you entered on the command line that caused the failure is printed.
1199
1200 Then, between the `Output from failing command(s) repeated here` and `End of
1201 repeated output` the first lines of output (stdout and stderr) from the actual
1202 failing command is repeated. In most cases, this is the error message that
1203 caused the build to fail. If multiple commands were failing (this can happen in
1204 a parallel build), output from all failed commands will be printed here.
1205
1206 The path to the `failure-logs` directory is printed. In this file you will find
1207 a `<target>.log` file that contains the output from this command in its
1208 entirety, and also a `<target>.cmd`, which contain the complete command line
1209 used for running this command. You can re-run the failing command by executing
1210 `. <path to failure-logs>/<target>.cmd` in your shell.
1211
1212 Another way to trace the failure is to follow the chain of make targets, from
1213 top-level targets to individual file targets. Between `Make failed targets
1214 repeated here` and `End of repeated output` the output from make showing this
1215 chain is repeated. The first failed recipe will typically contain the full path
1216 to the file in question that failed to compile. Following lines will show a
1217 trace of make targets why we ended up trying to compile that file.
1218
1219 Finally, some hints are given on how to locate the error in the complete log.
1220 In this example, we would try searching the log file for "`psMemoryPool.o`".
1221 Another way to quickly locate make errors in the log is to search for "`]
1222 Error`" or "`***`".
1223
1224 Note that the build failure summary will only help you if the issue was a
1225 compilation failure or similar. If the problem is more esoteric, or is due to
1226 errors in the build machinery, you will likely get empty output logs, and `No
1227 indication of failed target found` instead of the make target chain.
1228
1229 #### Checking the Build Log File
1230
1231 The output (stdout and stderr) from the latest build is always stored in
1232 `$BUILD/build.log`. The previous build log is stored as `build.log.old`. This
1233 means that it is not necessary to redirect the build output yourself if you
1234 want to process it.
1235
1236 You can increase the verbosity of the log file, by the `LOG` control variable
1237 to `make`. If you want to see the command lines used in compilations, use
1238 `LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug`
1239 or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g.
1240 `LOG=info,cmdlines`. The `debug` log level will show most shell commands
1241 executed by make, and `trace` will show all. Beware that both these log levels
1242 will produce a massive build log!
1243
1244 ### Fixing Unexpected Build Failures
1245
1246 Most of the time, the build will fail due to incorrect changes in the source
1247 code.
1248
1249 Sometimes the build can fail with no apparent changes that have caused the
1250 failure. If this is the first time you are building OpenJDK on this particular
1251 computer, and the build fails, the problem is likely with your build
1252 environment. But even if you have previously built OpenJDK with success, and it
1253 now fails, your build environment might have changed (perhaps due to OS
1254 upgrades or similar). But most likely, such failures are due to problems with
1255 the incremental rebuild.
1256
1257 #### Problems with the Build Environment
1258
1259 Make sure your configuration is correct. Re-run `configure`, and look for any
1260 warnings. Warnings that appear in the middle of the `configure` output is also
1261 repeated at the end, after the summary. The entire log is stored in
1262 `$BUILD/configure.log`.
1263
1264 Verify that the summary at the end looks correct. Are you indeed using the Boot
1265 JDK and native toolchain that you expect?
1266
1267 By default, OpenJDK has a strict approach where warnings from the compiler is
1268 considered errors which fail the build. For very new or very old compiler
1269 versions, this can trigger new classes of warnings, which thus fails the build.
1270 Run `configure` with `--disable-warnings-as-errors` to turn of this behavior.
1271 (The warnings will still show, but not make the build fail.)
1272
1273 #### Problems with Incremental Rebuilds
1274
1275 Incremental rebuilds mean that when you modify part of the product, only the
1276 affected parts get rebuilt. While this works great in most cases, and
1277 significantly speed up the development process, from time to time complex
1278 interdependencies will result in an incorrect build result. This is the most
1279 common cause for unexpected build problems, together with inconsistencies
1280 between the different Mercurial repositories in the forest.
1281
1282 Here are a suggested list of things to try if you are having unexpected build
1283 problems. Each step requires more time than the one before, so try them in
1284 order. Most issues will be solved at step 1 or 2.
1285
1286 1. Make sure your forest is up-to-date
1287
1288 Run `bash get_source.sh` to make sure you have the latest version of all
1289 repositories.
1290
1291 2. Clean build results
1292
1293 The simplest way to fix incremental rebuild issues is to run `make clean`.
1294 This will remove all build results, but not the configuration or any build
1295 system support artifacts. In most cases, this will solve build errors
1296 resulting from incremental build mismatches.
1297
1298 3. Completely clean the build directory.
1299
1300 If this does not work, the next step is to run `make dist-clean`, or
1301 removing the build output directory (`$BUILD`). This will clean all
1302 generated output, including your configuration. You will need to re-run
1303 `configure` after this step. A good idea is to run `make
1304 print-configuration` before running `make dist-clean`, as this will print
1305 your current `configure` command line. Here's a way to do this:
1306
1307 ```
1308 make print-configuration > current-configuration
1309 make dist-clean
1310 bash configure $(cat current-configuration)
1311 make
1312 ```
1313
1314 4. Re-clone the Mercurial forest
1315
1316 Sometimes the Mercurial repositories themselves gets in a state that causes
1317 the product to be un-buildable. In such a case, the simplest solution is
1318 often the "sledgehammer approach": delete the entire forest, and re-clone
1319 it. If you have local changes, save them first to a different location
1320 using `hg export`.
1321
1322 ### Specific Build Issues
1323
1324 #### Clock Skew
1325
1326 If you get an error message like this:
1327 ```
1328 File 'xxx' has modification time in the future.
1329 Clock skew detected. Your build may be incomplete.
1330 ```
1331 then the clock on your build machine is out of sync with the timestamps on the
1332 source files. Other errors, apparently unrelated but in fact caused by the
1333 clock skew, can occur along with the clock skew warnings. These secondary
1334 errors may tend to obscure the fact that the true root cause of the problem is
1335 an out-of-sync clock.
1336
1337 If you see these warnings, reset the clock on the build machine, run `make
1338 clean` and restart the build.
1339
1340 #### Out of Memory Errors
1341
1342 On Solaris, you might get an error message like this:
1343 ```
1344 Trouble writing out table to disk
1345 ```
1346 To solve this, increase the amount of swap space on your build machine.
1347
1348 On Windows, you might get error messages like this:
1349 ```
1350 fatal error - couldn't allocate heap
1351 cannot create ... Permission denied
1352 spawn failed
1353 ```
1354 This can be a sign of a Cygwin problem. See the information about solving
1355 problems in the [Cygwin](#cygwin) section. Rebooting the computer might help
1356 temporarily.
1357
1358 ### Getting Help
1359
1360 If none of the suggestions in this document helps you, or if you find what you
1361 believe is a bug in the build system, please contact the Build Group by sending
1362 a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net).
1363 Please include the relevant parts of the configure and/or build log.
1364
1365 If you need general help or advice about developing for OpenJDK, you can also
1366 contact the Adoption Group. See the section on [Contributing to OpenJDK](
1367 #contributing-to-openjdk) for more information.
1368
1369 ## Hints and Suggestions for Advanced Users
1370
1371 ### Setting Up a Forest for Pushing Changes (defpath)
1372
1373 To help you prepare a proper push path for a Mercurial repository, there exists
1374 a useful tool known as [defpath](
1375 http://openjdk.java.net/projects/code-tools/defpath). It will help you setup a
1376 proper push path for pushing changes to OpenJDK.
1377
1378 Install the extension by cloning
1379 `http://hg.openjdk.java.net/code-tools/defpath` and updating your `.hgrc` file.
1380 Here's one way to do this:
1381
1382 ```
1383 cd ~
1384 mkdir hg-ext
1385 cd hg-ext
1386 hg clone http://hg.openjdk.java.net/code-tools/defpath
1387 cat << EOT >> ~/.hgrc
1388 [extensions]
1389 defpath=~/hg-ext/defpath/defpath.py
1390 EOT
1391 ```
1392
1393 You can now setup a proper push path using:
1394 ```
1395 hg defpath -d -u <your OpenJDK username>
1396 ```
1397
1398 If you also have the `trees` extension installed in Mercurial, you will
1399 automatically get a `tdefpath` command, which is even more useful. By running
1400 `hg tdefpath -du <username>` in the top repository of your forest, all repos
1401 will get setup automatically. This is the recommended usage.
1402
1403 ### Bash Completion
1404
1405 The `configure` and `make` commands tries to play nice with bash command-line
1406 completion (using `<tab>` or `<tab><tab>`). To use this functionality, make
1407 sure you enable completion in your `~/.bashrc` (see instructions for bash in
1408 your operating system).
1409
1410 Make completion will work out of the box, and will complete valid make targets.
1411 For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`.
1412
1413 The `configure` script can get completion for options, but for this to work you
1414 need to help `bash` on the way. The standard way of running the script, `bash
1415 configure`, will not be understood by bash completion. You need `configure` to
1416 be the command to run. One way to achieve this is to add a simple helper script
1417 to your path:
1418
1419 ```
1420 cat << EOT > /tmp/configure
1421 #!/bin/bash
1422 if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then
1423 echo >&2 "Abort: Trying to call configure helper recursively"
1424 exit 1
1425 fi
1426
1427 bash \$PWD/configure "\$@"
1428 EOT
1429 chmod +x /tmp/configure
1430 sudo mv /tmp/configure /usr/local/bin
1431 ```
1432
1433 Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`.
1434
1435 ### Using Multiple Configurations
1436
1437 You can have multiple configurations for a single source forest. When you
1438 create a new configuration, run `configure --with-conf-name=<name>` to create a
1439 configuration with the name `<name>`. Alternatively, you can create a directory
1440 under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd
1441 build/<name> && bash ../../configure`.
1442
1443 Then you can build that configuration using `make CONF_NAME=<name>` or `make
1444 CONF=<pattern>`, where `<pattern>` is a substring matching one or several
1445 configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will
1446 match *all* available configuration, so `make CONF= hotspot` will build the
1447 `hotspot` target for all configurations. Alternatively, you can execute `make`
1448 in the configuration directory, e.g. `cd build/<name> && make`.
1449
1450 ### Handling Reconfigurations
1451
1452 If you update the forest and part of the configure script has changed, the
1453 build system will force you to re-run `configure`.
1454
1455 Most of the time, you will be fine by running `configure` again with the same
1456 arguments as the last time, which can easily be performed by `make
1457 reconfigure`. To simplify this, you can use the `CONF_CHECK` make control
1458 variable, either as `make CONF_CHECK=auto`, or by setting an environment
1459 variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc`
1460 file, `make` will always run `reconfigure` automatically whenever the configure
1461 script has changed.
1462
1463 You can also use `CONF_CHECK=ignore` to skip the check for a needed configure
1464 update. This might speed up the build, but comes at the risk of an incorrect
1465 build result. This is only recommended if you know what you're doing.
1466
1467 From time to time, you will also need to modify the command line to `configure`
1468 due to changes. Use `make print-configure` to show the command line used for
1469 your current configuration.
1470
1471 ### Using Fine-Grained Make Targets
1472
1473 The default behavior for make is to create consistent and correct output, at
1474 the expense of build speed, if necessary.
1475
1476 If you are prepared to take some risk of an incorrect build, and know enough of
1477 the system to understand how things build and interact, you can speed up the
1478 build process considerably by instructing make to only build a portion of the
1479 product.
1480
1481 #### Building Individual Modules
1482
1483 The safe way to use fine-grained make targets is to use the module specific
1484 make targets. All source code in JDK 9 is organized so it belongs to a module,
1485 e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific module, by
1486 giving it as make target: `make jdk.jdwp.agent`. If the specified module
1487 depends on other modules (e.g. `java.base`), those modules will be built first.
1488
1489 You can also specify a set of modules, just as you can always specify a set of
1490 make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi
1491 jdk.crypto.ucrypto`
1492
1493 #### Building Individual Module Phases
1494
1495 The build process for each module is divided into separate phases. Not all
1496 modules need all phases. Which are needed depends on what kind of source code
1497 and other artifact the module consists of. The phases are:
1498
1499 * `gensrc` (Generate source code to compile)
1500 * `gendata` (Generate non-source code artifacts)
1501 * `copy` (Copy resource artifacts)
1502 * `java` (Compile Java code)
1503 * `launchers` (Compile native executables)
1504 * `libs` (Compile native libraries)
1505 * `rmic` (Run the `rmic` tool)
1506
1507 You can build only a single phase for a module by using the notation
1508 `$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`,
1509 use `make java.base-gensrc`.
1510
1511 Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if
1512 present). Make will build all needed prerequisites before building the
1513 requested phase.
1514
1515 #### Skipping the Dependency Check
1516
1517 When using an iterative development style with frequent quick rebuilds, the
1518 dependency check made by make can take up a significant portion of the time
1519 spent on the rebuild. In such cases, it can be useful to bypass the dependency
1520 check in make.
1521
1522 > **Note that if used incorrectly, this can lead to a broken build!**
1523
1524 To achieve this, append `-only` to the build target. For instance, `make
1525 jdk.jdwp.agent-java-only` will *only* build the `java` phase of the
1526 `jdk.jdwp.agent` module. If the required dependencies are not present, the
1527 build can fail. On the other hand, the execution time measures in milliseconds.
1528
1529 A useful pattern is to build the first time normally (e.g. `make
1530 jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target.
1531
1532 #### Rebuilding Part of java.base (JDK\_FILTER)
1533
1534 If you are modifying files in `java.base`, which is the by far largest module
1535 in OpenJDK, then you need to rebuild all those files whenever a single file has
1536 changed. (This inefficiency will hopefully be addressed in JDK 10.)
1537
1538 As a hack, you can use the make control variable `JDK_FILTER` to specify a
1539 pattern that will be used to limit the set of files being recompiled. For
1540 instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods,
1541 `make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation
1542 to files in the `javax.crypto` package.
1543
1544 ### Learn About Mercurial
1545
1546 To become an efficient OpenJDK developer, it is recommended that you invest in
1547 learning Mercurial properly. Here are some links that can get you started:
1548
1549 * [Mercurial for git users](http://www.mercurial-scm.org/wiki/GitConcepts)
1550 * [The official Mercurial tutorial](http://www.mercurial-scm.org/wiki/Tutorial)
1551 * [hg init](http://hginit.com/)
1552 * [Mercurial: The Definitive Guide](http://hgbook.red-bean.com/read/)
1553
1554 ## Understanding the Build System
1555
1556 This section will give you a more technical description on the details of the
1557 build system.
1558
1559 ### Configurations
1560
1561 The build system expects to find one or more configuration. These are
1562 technically defined by the `spec.gmk` in a subdirectory to the `build`
1563 subdirectory. The `spec.gmk` file is generated by `configure`, and contains in
1564 principle the configuration (directly or by files included by `spec.gmk`).
1565
1566 You can, in fact, select a configuration to build by pointing to the `spec.gmk`
1567 file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`.
1568 While this is not the recommended way to call `make` as a user, it is what is
1569 used under the hood by the build system.
1570
1571 ### Build Output Structure
1572
1573 The build output for a configuration will end up in `build/<configuration
1574 name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory
1575 contains the following important directories:
1576
1577 ```
1578 buildtools/
1579 configure-support/
1580 hotspot/
1581 images/
1582 jdk/
1583 make-support/
1584 support/
1585 test-results/
1586 test-support/
1587 ```
1588
1589 This is what they are used for:
1590
1591 * `images`: This is the directory were the output of the `*-image` make
1592 targets end up. For instance, `make jdk-image` ends up in `images/jdk`.
1593
1594 * `jdk`: This is the "exploded image". After `make jdk`, you will be able to
1595 launch the newly built JDK by running `$BUILD/jdk/bin/java`.
1596
1597 * `test-results`: This directory contains the results from running tests.
1598
1599 * `support`: This is an area for intermediate files needed during the build,
1600 e.g. generated source code, object files and class files. Some noteworthy
1601 directories in `support` is `gensrc`, which contains the generated source
1602 code, and the `modules_*` directories, which contains the files in a
1603 per-module hierarchy that will later be collapsed into the `jdk` directory
1604 of the exploded image.
1605
1606 * `buildtools`: This is an area for tools compiled for the build platform
1607 that are used during the rest of the build.
1608
1609 * `hotspot`: This is an area for intermediate files needed when building
1610 hotspot.
1611
1612 * `configure-support`, `make-support` and `test-support`: These directories
1613 contain files that are needed by the build system for `configure`, `make`
1614 and for running tests.
1615
1616 ### Fixpath
1617
1618 Windows path typically look like `C:\User\foo`, while Unix paths look like
1619 `/home/foo`. Tools with roots from Unix often experience issues related to this
1620 mismatch when running on Windows.
1621
1622 In the OpenJDK build, we always use Unix paths internally, and only just before
1623 calling a tool that does not understand Unix paths do we convert them to
1624 Windows paths.
1625
1626 This conversion is done by the `fixpath` tool, which is a small wrapper that
1627 modifies unix-style paths to Windows-style paths in command lines. Fixpath is
1628 compiled automatically by `configure`.
1629
1630 ### Native Debug Symbols
1631
1632 Native libraries and executables can have debug symbol (and other debug
1633 information) associated with them. How this works is very much platform
1634 dependent, but a common problem is that debug symbol information takes a lot of
1635 disk space, but is rarely needed by the end user.
1636
1637 The OpenJDK supports different methods on how to handle debug symbols. The
1638 method used is selected by `--with-native-debug-symbols`, and available methods
1639 are `none`, `internal`, `external`, `zipped`.
1640
1641 * `none` means that no debug symbols will be generated during the build.
1642
1643 * `internal` means that debug symbols will be generated during the build, and
1644 they will be stored in the generated binary.
1645
1646 * `external` means that debug symbols will be generated during the build, and
1647 after the compilation, they will be moved into a separate `.debuginfo` file.
1648 (This was previously known as FDS, Full Debug Symbols).
1649
1650 * `zipped` is like `external`, but the .debuginfo file will also be zipped
1651 into a `.diz` file.
1652
1653 When building for distribution, `zipped` is a good solution. Binaries built
1654 with `internal` is suitable for use by developers, since they facilitate
1655 debugging, but should be stripped before distributed to end users.
1656
1657 ### Autoconf Details
1658
1659 The `configure` script is based on the autoconf framework, but in some details
1660 deviate from a normal autoconf `configure` script.
1661
1662 The `configure` script in the top level directory of OpenJDK is just a thin
1663 wrapper that calls `common/autoconf/configure`. This in turn provides
1664 functionality that is not easily expressed in the normal Autoconf framework,
1665 and then calls into the core of the `configure` script, which is the
1666 `common/autoconf/generated-configure.sh` file.
1667
1668 As the name implies, this file is generated by Autoconf. It is checked in after
1669 regeneration, to alleviate the common user to have to install Autoconf.
1670
1671 The build system will detect if the Autoconf source files have changed, and
1672 will trigger a regeneration of `common/autoconf/generated-configure.sh` if
1673 needed. You can also manually request such an update by `bash
1674 common/autoconf/autogen.sh`.
1675
1676 If you make changes to the build system that requires a re-generation, note the
1677 following:
1678
1679 * You must use *exactly* version 2.69 of autoconf for your patch to be
1680 accepted. This is to avoid spurious changes in the generated file. Note
1681 that Ubuntu 16.04 ships a patched version of autoconf which claims to be
1682 2.69, but is not.
1683
1684 * You do not need to include the generated file in reviews.
1685
1686 * If the generated file needs updating, the Oracle JDK closed counter-part
1687 will also need to be updated. It is very much appreciated if you ask for an
1688 Oracle engineer to sponsor your push so this can be made in tandem.
1689
1690 ### Developing the Build System Itself
1691
1692 This section contains a few remarks about how to develop for the build system
1693 itself. It is not relevant if you are only making changes in the product source
1694 code.
1695
1696 While technically using `make`, the make source files of the OpenJDK does not
1697 resemble most other Makefiles. Instead of listing specific targets and actions
1698 (perhaps using patterns), the basic modus operandi is to call a high-level
1699 function (or properly, macro) from the API in `make/common`. For instance, to
1700 compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module,
1701 a call like this would be made:
1702
1703 ```
1704 $(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \
1705 SETUP := GENERATE_OLDBYTECODE, \
1706 SRC := $(TOPDIR)/src/jkd.foo/share/classes, \
1707 INCLUDES := jdk/internal/foo, \
1708 BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \
1709 ))
1710 ```
1711
1712 By encapsulating and expressing the high-level knowledge of *what* should be
1713 done, rather than *how* it should be done (as is normal in Makefiles), we can
1714 build a much more powerful and flexible build system.
1715
1716 Correct dependency tracking is paramount. Sloppy dependency tracking will lead
1717 to improper parallelization, or worse, race conditions.
1718
1719 To test for/debug race conditions, try running `make JOBS=1` and `make
1720 JOBS=100` and see if it makes any difference. (It shouldn't).
1721
1722 To compare the output of two different builds and see if, and how, they differ,
1723 run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two
1724 builds you want to compare.
1725
1726 To automatically build two consecutive versions and compare them, use
1727 `COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value
1728 assignments, like this:
1729 ```
1730 make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot
1731 ```
1732 See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`.
1733
1734 To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`.
1735 Use `JOBS=1` to avoid parallelism.
1736
1737 Please check that you adhere to the [Code Conventions for the Build System](
1738 http://openjdk.java.net/groups/build/doc/code-conventions.html) before
1739 submitting patches. Also see the section in [Autoconf Details](
1740 #autoconf-details) about the generated configure script.
1741
1742 ## Contributing to OpenJDK
1743
1744 So, now you've build your OpenJDK, and made your first patch, and want to
1745 contribute it back to the OpenJDK community.
1746
1747 First of all: Thank you! We gladly welcome your contribution to the OpenJDK.
1748 However, please bear in mind that OpenJDK is a massive project, and we must ask
1749 you to follow our rules and guidelines to be able to accept your contribution.
1750
1751 The official place to start is the ['How to contribute' page](
1752 http://openjdk.java.net/contribute/). There is also an official (but somewhat
1753 outdated and skimpy on details) [Developer's Guide](
1754 http://openjdk.java.net/guide/).
1755
1756 If this seems overwhelming to you, the Adoption Group is there to help you! A
1757 good place to start is their ['New Contributor' page](
1758 https://wiki.openjdk.java.net/display/Adoption/New+Contributor), or start
1759 reading the comprehensive [Getting Started Kit](
1760 https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The
1761 Adoption Group will also happily answer any questions you have about
1762 contributing. Contact them by [mail](
1763 http://mail.openjdk.java.net/mailman/listinfo/adoption-discuss) or [IRC](
1764 http://openjdk.java.net/irc/).
1765
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