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 `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
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 OpenJDK uses [Mercurial](http://www.mercurial-scm.org) for source control. The
48 source 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
50 repositories to be able to build OpenJDK. To assist you in dealing with this
51 somewhat unusual arrangement, there are multiple tools available, which are
52 explained below.
53
54 In any case, make sure you are getting the correct version. At the [OpenJDK
55 Mercurial server](http://hg.openjdk.java.net/) you can see a list of all
56 available forests. If you want to build an older version, e.g. JDK 8, it is
57 recommended that you get the `jdk8u` forest, which contains incremental
58 updates, instead of the `jdk8` forest, which was frozen at JDK 8 GA.
59
60 If you are new to Mercurial, a good place to start is the [Mercurial Beginner's
61 Guide](http://www.mercurial-scm.org/guide). The rest of this document assumes a
62 working knowledge of Mercurial.
63
64 ### Special Considerations
65
66 For a smooth building experience, it is recommended that you follow these rules
67 on 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
106 The simplest way to get the entire forest is probably to clone the top-level
107 repository and then run the `get_source.sh` script, like this:
108
109 ```
110 hg clone http://hg.openjdk.java.net/jdk9/jdk9
111 cd jdk9
112 bash get_source.sh
113 ```
114
115 The first time this is run, it will clone all the sub-repositories. Any
116 subsequent execution of the script will update all sub-repositories to the
117 latest revision.
118
119 ### Using hgforest.sh
120
121 The `hgforest.sh` script is more expressive than `get_source.sh`. It takes any
122 number of arguments, and runs `hg` with those arguments on each sub-repository
123 in the forest. The `get_source.sh` script is basically a simple wrapper that
124 runs 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
145 The trees extension is a Mercurial add-on that helps you deal with the forest.
146 More information is available on the [Code Tools trees page](
147 http://openjdk.java.net/projects/code-tools/trees).
148
149 #### Installing the Extension
150
151 Install the extension by cloning `http://hg.openjdk.java.net/code-tools/trees`
152 and updating your `.hgrc` file. Here's one way to do this:
153
154 ```
155 cd ~
156 mkdir hg-ext
157 cd hg-ext
158 hg clone http://hg.openjdk.java.net/code-tools/trees
159 cat << EOT >> ~/.hgrc
160 [extensions]
161 trees=~/hg-ext/trees/trees.py
162 EOT
163 ```
164
165 #### Initializing the Tree
166
167 The trees extension needs to know the structure of the forest. If you have
168 already cloned the entire forest using another method, you can initialize the
169 forest like this:
170
171 ```
172 hg tconf --set --walk --depth
173 ```
174
175 Or 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 ```
179 hg tclone http://hg.openjdk.java.net/jdk9/jdk9
180 ```
181
182 In this case, the forest will be properly initialized from the start.
183
184 #### Other Operations
185
186 The trees extensions supplement many common operations with a trees version by
187 prefixing a `t` to the normal Mercurial command, e.g. `tcommit`, `tstatus` or
188 `tmerge`. For instance, to update the entire forest:
189
190 ```
191 hg tpull -u
192 ```
193
194 ## Build Hardware Requirements
195
196 OpenJDK is a massive project, and require machines ranging from decent to
197 powerful to be able to build in a reasonable amount of time, or to be able to
198 complete a build at all.
199
200 We *strongly* recommend usage of an SSD disk for the build, since disk speed is
201 one of the limiting factors for build performance.
202
203 ### Building on x86
204
205 At 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
207 space is required (8 GB minimum for building on Solaris).
208
209 Even for 32-bit builds, it is recommended to use a 64-bit build machine, and
210 instead create a 32-bit target using `--with-target-bits=32`.
211
212 ### Building on sparc
213
214 At a minimum, a machine with 4 cores is advisable, as well as 4 GB of RAM. (The
215 more cores to use, the more memory you need.) At least 8 GB of free disk space
216 is required.
217
218 ### Building on arm/aarch64
219
220 This is not recommended. Instead, see the section on [Cross-compiling](
221 #cross-compiling).
222
223 ## Operating System Requirements
224
225 The mainline OpenJDK project supports Linux, Solaris, macOS, AIX and Windows.
226 Support for other operating system, e.g. BSD, exists in separate "port"
227 projects.
228
229 In general, OpenJDK can be built on a wide range of versions of these operating
230 systems, but the further you deviate from what is tested on a daily basis, the
231 more likely you are to run into problems.
232
233 This table lists the OS versions used by Oracle when building JDK 9. Such
234 information is always subject to change, but this table is up to date at the
235 time 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
244 The double version numbers for Linux, Solaris and macOS is due to the hybrid
245 model used at Oracle, where header files and external libraries from an older
246 version is used when building on a more modern version of the OS.
247
248 The Build Group has a wiki page with [Supported Build Platforms](
249 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms). From
250 time to time, this is updated by the community to list successes or failures of
251 building on different platforms.
252
253 ### Windows
254
255 Windows XP is not a supported platform, but all newer Windows should be able to
256 build OpenJDK.
257
258 On Windows, it is important that you pay attention to the instructions in the
259 [Special Considerations](#special-considerations).
260
261 Windows is the only non-POSIX OS supported by OpenJDK, and as such, requires
262 some extra care. A POSIX support layer is required to build on Windows. For
263 OpenJDK 9, the only supported such layer is Cygwin. (Msys is no longer
264 supported 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
266 require a community effort to implement.)
267
268 Internally in the build system, all paths are represented as Unix-style paths,
269 e.g. `/cygdrive/c/hg/jdk9/Makefile` rather than `C:\hg\jdk9\Makefile`. This
270 rule 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
273 on [Fixpath](#fixpath).
274
275 #### Cygwin
276
277 A functioning [Cygwin](http://www.cygwin.com/) environment is thus required for
278 building OpenJDK on Windows. If you have a 64-bit OS, we strongly recommend
279 using the 64-bit version of Cygwin.
280
281 **Note:** Cygwin has a model of continuously updating all packages without any
282 easy way to install or revert to a specific version of a package. This means
283 that whenever you add or update a package in Cygwin, you might (inadvertently)
284 update tools that are used by the OpenJDK build process, and that can cause
285 unexpected build problems.
286
287 OpenJDK requires GNU Make 4.0 or greater on Windows. This is usually not a
288 problem, since Cygwin currently only distributes GNU Make at a version above
289 4.0.
290
291 Apart from the basic Cygwin installation, the following packages must also be
292 installed:
293
294 * `make`
295 * `zip`
296 * `unzip`
297
298 Often, 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
303 Unfortunately, Cygwin can be unreliable in certain circumstances. If you
304 experience build tool crashes or strange issues when building on Windows,
305 please check the Cygwin FAQ on the ["BLODA" list](
306 https://cygwin.com/faq/faq.html#faq.using.bloda) and the section on [fork()
307 failures](https://cygwin.com/faq/faq.html#faq.using.fixing-fork-failures).
308
309 ### Solaris
310
311 See `make/devkit/solaris11.1-package-list.txt` for a list of recommended
312 packages to install when building on Solaris. The versions specified in this
313 list is the versions used by the daily builds at Oracle, and is likely to work
314 properly.
315
316 Older versions of Solaris shipped a broken version of `objcopy`. At least
317 version 2.21.1 is needed, which is provided by Solaris 11 Update 1. Objcopy is
318 needed if you want to have external debug symbols. Please make sure you are
319 using at least version 2.21.1 of objcopy, or that you disable external debug
320 symbols.
321
322 ### macOS
323
324 Apple is using a quite aggressive scheme of pushing OS updates, and coupling
325 these updates with required updates of Xcode. Unfortunately, this makes it
326 difficult for a project like OpenJDK to keep pace with a continuously updated
327 machine running macOS. See the section on [Apple Xcode](#apple-xcode) on some
328 strategies to deal with this.
329
330 It is recommended that you use at least Mac OS X 10.9 (Mavericks). At the time
331 of writing, OpenJDK has been successfully compiled on macOS versions up to
332 10.12.5 (Sierra), using XCode 8.3.2 and `--disable-warnings-as-errors`.
333
334 The standard macOS environment contains the basic tooling needed to build, but
335 for external libraries a package manager is recommended. OpenJDK uses
336 [homebrew](https://brew.sh/) in the examples, but feel free to use whatever
337 manager you want (or none).
338
339 ### Linux
340
341 It is often not much problem to build OpenJDK on Linux. The only general advice
342 is to try to use the compilers, external libraries and header files as provided
343 by your distribution.
344
345 The basic tooling is provided as part of the core operating system, but you
346 will most likely need to install developer packages.
347
348 For apt-based distributions (Debian, Ubuntu, etc), try this:
349 ```
350 sudo apt-get install build-essential
351 ```
352
353 For rpm-based distributions (Fedora, Red Hat, etc), try this:
354 ```
355 sudo yum groupinstall "Development Tools"
356 ```
357
358 ### AIX
359
360 The regular builds by SAP is using AIX version 7.1, but AIX 5.3 is also
361 supported. See the [OpenJDK PowerPC Port Status Page](
362 http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details.
363
364 ## Native Compiler (Toolchain) Requirements
365
366 Large portions of OpenJDK consists of native code, that needs to be compiled to
367 be able to run on the target platform. In theory, toolchain and operating
368 system should be independent factors, but in practice there's more or less a
369 one-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
379 Please see the individual sections on the toolchains for version
380 recommendations. As a reference, these versions of the toolchains are used, at
381 the time of writing, by Oracle for the daily builds of OpenJDK. It should be
382 possible to compile OpenJDK with both older and newer versions, but the closer
383 you stay to this list, the more likely you are to compile successfully without
384 issues.
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
395 The minimum accepted version of gcc is 4.7. Older versions will generate a warning
396 by `configure` and are unlikely to work.
397
398 OpenJDK 9 includes patches that should allow gcc 6 to compile, but this should
399 be considered experimental.
400
401 In general, any version between these two should be usable.
402
403 ### clang
404
405 The minimum accepted version of clang is 3.2. Older versions will not be
406 accepted by `configure`.
407
408 To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`.
409
410 ### Apple Xcode
411
412 The oldest supported version of Xcode is 5.
413
414 You will need the Xcode command lines developers tools to be able to build
415 OpenJDK. (Actually, *only* the command lines tools are needed, not the IDE.)
416 The simplest way to install these is to run:
417 ```
418 xcode-select --install
419 ```
420
421 It is advisable to keep an older version of Xcode for building OpenJDK when
422 updating Xcode. This [blog page](
423 http://iosdevelopertips.com/xcode/install-multiple-versions-of-xcode.html) has
424 good suggestions on managing multiple Xcode versions. To use a specific version
425 of Xcode, use `xcode-select -s` before running `configure`, or use
426 `--with-toolchain-path` to point to the version of Xcode to use, e.g.
427 `configure --with-toolchain-path=/Applications/Xcode5.app/Contents/Developer/usr/bin`
428
429 If you have recently (inadvertently) updated your OS and/or Xcode version, and
430 OpenJDK can no longer be built, please see the section on [Problems with the
431 Build Environment](#problems-with-the-build-environment), and [Getting
432 Help](#getting-help) to find out if there are any recent, non-merged patches
433 available for this update.
434
435 ### Oracle Solaris Studio
436
437 The minimum accepted version of the Solaris Studio compilers is 5.13
438 (corresponding to Solaris Studio 12.4). Older versions will not be accepted by
439 configure.
440
441 The Solaris Studio installation should contain at least these packages:
442
443 Package Version
444 -------------------------------------------------- -------------
445 developer/solarisstudio-124/backend 12.4-1.0.6.0
446 developer/solarisstudio-124/c++ 12.4-1.0.10.0
447 developer/solarisstudio-124/cc 12.4-1.0.4.0
448 developer/solarisstudio-124/library/c++-libs 12.4-1.0.10.0
449 developer/solarisstudio-124/library/math-libs 12.4-1.0.0.1
450 developer/solarisstudio-124/library/studio-gccrt 12.4-1.0.0.1
451 developer/solarisstudio-124/studio-common 12.4-1.0.0.1
452 developer/solarisstudio-124/studio-ja 12.4-1.0.0.1
453 developer/solarisstudio-124/studio-legal 12.4-1.0.0.1
454 developer/solarisstudio-124/studio-zhCN 12.4-1.0.0.1
455
456 Compiling with Solaris Studio can sometimes be finicky. This is the exact
457 version used by Oracle, which worked correctly at the time of writing:
458 ```
459 $ cc -V
460 cc: Sun C 5.13 SunOS_i386 2014/10/20
461 $ CC -V
462 CC: Sun C++ 5.13 SunOS_i386 151846-10 2015/10/30
463 ```
464
465 ### Microsoft Visual Studio
466
467 The minimum accepted version of Visual Studio is 2010. Older versions will not
468 be accepted by `configure`. The maximum accepted version of Visual Studio is
469 2013.
470
471 If you have multiple versions of Visual Studio installed, `configure` will by
472 default pick the latest. You can request a specific version to be used by
473 setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2010`.
474
475 If you get `LINK: fatal error LNK1123: failure during conversion to COFF: file
476 invalid` when building using Visual Studio 2010, you have encountered
477 [KB2757355](http://support.microsoft.com/kb/2757355), a bug triggered by a
478 specific installation order. However, the solution suggested by the KB article
479 does not always resolve the problem. See [this stackoverflow discussion](
480 https://stackoverflow.com/questions/10888391) for other suggestions.
481
482 ### IBM XL C/C++
483
484 The regular builds by SAP is using version 12.1, described as `IBM XL C/C++ for
485 AIX, V12.1 (5765-J02, 5725-C72) Version: 12.01.0000.0017`.
486
487 See the [OpenJDK PowerPC Port Status Page](
488 http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details.
489
490 ## Boot JDK Requirements
491
492 Paradoxically, building OpenJDK requires a pre-existing JDK. This is called the
493 "boot JDK". The boot JDK does not have to be OpenJDK, though. If you are
494 porting OpenJDK to a new platform, chances are that there already exists
495 another JDK for that platform that is usable as boot JDK.
496
497 The rule of thumb is that the boot JDK for building JDK major version *N*
498 should be an JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be
499 suitable as boot JDK. However, OpenJDK should be able to "build itself", so an
500 up-to-date build of the current OpenJDK source is an acceptable alternative. If
501 you are following the *N-1* rule, make sure you got the latest update version,
502 since JDK 8 GA might not be able to build JDK 9 on all platforms.
503
504 If the Boot JDK is not automatically detected, or the wrong JDK is picked, use
505 `--with-boot-jdk` to point to the JDK to use.
506
507 ### JDK 8 on Linux
508
509 On apt-based distros (like Debian and Ubuntu), `sudo apt-get install
510 openjdk-8-jdk` is typically enough to install OpenJDK 8. On rpm-based distros
511 (like Fedora and Red Hat), try `sudo yum install java-1.8.0-openjdk-devel`.
512
513 ### JDK 8 on Windows
514
515 No pre-compiled binaries of OpenJDK 8 are readily available for Windows at the
516 time of writing. An alternative is to download the [Oracle JDK](
517 http://www.oracle.com/technetwork/java/javase/downloads). Another is the [Adopt
518 OpenJDK Project](https://adoptopenjdk.net/), which publishes experimental
519 prebuilt binaries for Windows.
520
521 ### JDK 8 on macOS
522
523 No pre-compiled binaries of OpenJDK 8 are readily available for macOS at the
524 time of writing. An alternative is to download the [Oracle JDK](
525 http://www.oracle.com/technetwork/java/javase/downloads), or to install it
526 using `brew cask install java`. Another option is the [Adopt OpenJDK Project](
527 https://adoptopenjdk.net/), which publishes experimental prebuilt binaries for
528 macOS.
529
530 ### JDK 8 on AIX
531
532 No pre-compiled binaries of OpenJDK 8 are readily available for AIX at the
533 time of writing. A starting point for working with OpenJDK on AIX is
534 the [PowerPC/AIX Port Project](http://openjdk.java.net/projects/ppc-aix-port/).
535
536 ## External Library Requirements
537
538 Different platforms require different external libraries. In general, libraries
539 are not optional - that is, they are either required or not used.
540
541 If a required library is not detected by `configure`, you need to provide the
542 path to it. There are two forms of the `configure` arguments to point to an
543 external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to
544 include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise,
545 but require the include files an library files to reside in a default hierarchy
546 under this directory. In most cases, it works fine.
547
548 As a fallback, the second version allows you to point to the include directory
549 and the lib directory separately.
550
551 ### FreeType
552
553 FreeType2 from [The FreeType Project](http://www.freetype.org/) is required on
554 all platforms. At least version 2.3 is required.
555
556 * To install on an apt-based Linux, try running `sudo apt-get install
557 libcups2-dev`.
558 * To install on an rpm-based Linux, try running `sudo yum install
559 cups-devel`.
560 * To install on Solaris, try running `pkg install system/library/freetype-2`.
561 * To install on macOS, try running `brew install freetype`.
562 * To install on Windows, see [below](#building-freetype-on-windows).
563
564 Use `--with-freetype=<path>` if `configure` does not properly locate your
565 FreeType files.
566
567 #### Building FreeType on Windows
568
569 On Windows, there is no readily available compiled version of FreeType. OpenJDK
570 can help you compile FreeType from source. Download the FreeType sources and
571 unpack them into an arbitrary directory:
572
573 ```
574 wget http://download.savannah.gnu.org/releases/freetype/freetype-2.5.3.tar.gz
575 tar -xzf freetype-2.5.3.tar.gz
576 ```
577
578 Then run `configure` with `--with-freetype-src=<freetype_src>`. This will
579 automatically build the freetype library into `<freetype_src>/lib64` for 64-bit
580 builds or into `<freetype_src>/lib32` for 32-bit builds. Afterwards you can
581 always use `--with-freetype-include=<freetype_src>/include` and
582 `--with-freetype-lib=<freetype_src>/lib[32|64]` for other builds.
583
584 Alternatively you can unpack the sources like this to use the default
585 directory:
586
587 ```
588 tar --one-top-level=$HOME/freetype --strip-components=1 -xzf freetype-2.5.3.tar.gz
589 ```
590
591 ### CUPS
592
593 CUPS, [Common UNIX Printing System](http://www.cups.org) header files are
594 required on all platforms, except Windows. Often these files are provided by
595 your operating system.
596
597 * To install on an apt-based Linux, try running `sudo apt-get install
598 libcups2-dev`.
599 * To install on an rpm-based Linux, try running `sudo yum install
600 cups-devel`.
601 * To install on Solaris, try running `pkg install print/cups`.
602
603 Use `--with-cups=<path>` if `configure` does not properly locate your CUPS
604 files.
605
606 ### X11
607
608 Certain [X11](http://www.x.org/) libraries and include files are required on
609 Linux and Solaris.
610
611 * To install on an apt-based Linux, try running `sudo apt-get install
612 libx11-dev libxext-dev libxrender-dev libxtst-dev libxt-dev`.
613 * To install on an rpm-based Linux, try running `sudo yum install
614 libXtst-devel libXt-devel libXrender-devel libXi-devel`.
615 * To install on Solaris, try running `pkg install x11/header/x11-protocols
616 x11/library/libice x11/library/libpthread-stubs x11/library/libsm
617 x11/library/libx11 x11/library/libxau x11/library/libxcb
618 x11/library/libxdmcp x11/library/libxevie x11/library/libxext
619 x11/library/libxrender x11/library/libxscrnsaver x11/library/libxtst
620 x11/library/toolkit/libxt`.
621
622 Use `--with-x=<path>` if `configure` does not properly locate your X11 files.
623
624 ### ALSA
625
626 ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is
627 required on Linux. At least version 0.9.1 of ALSA is required.
628
629 * To install on an apt-based Linux, try running `sudo apt-get install
630 libasound2-dev`.
631 * To install on an rpm-based Linux, try running `sudo yum install
632 alsa-lib-devel`.
633
634 Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA
635 files.
636
637 ### libffi
638
639 libffi, the [Portable Foreign Function Interface Library](
640 http://sourceware.org/libffi) is required when building the Zero version of
641 Hotspot.
642
643 * To install on an apt-based Linux, try running `sudo apt-get install
644 libffi-dev`.
645 * To install on an rpm-based Linux, try running `sudo yum install
646 libffi-devel`.
647
648 Use `--with-libffi=<path>` if `configure` does not properly locate your libffi
649 files.
650
651 ## Other Tooling Requirements
652
653 ### GNU Make
654
655 OpenJDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors
656 of make are supported.
657
658 At least version 3.81 of GNU Make must be used. For distributions supporting
659 GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful
660 functionality to handle parallel building (supported by `--with-output-sync`)
661 and speed and stability improvements.
662
663 Note that `configure` locates and verifies a properly functioning version of
664 `make` and stores the path to this `make` binary in the configuration. If you
665 start a build using `make` on the command line, you will be using the version
666 of make found first in your `PATH`, and not necessarily the one stored in the
667 configuration. This initial make will be used as "bootstrap make", and in a
668 second stage, the make located by `configure` will be called. Normally, this
669 will present no issues, but if you have a very old `make`, or a non-GNU Make
670 `make` in your path, this might cause issues.
671
672 If you want to override the default make found by `configure`, use the `MAKE`
673 configure variable, e.g. `configure MAKE=/opt/gnu/make`.
674
675 On Solaris, it is common to call the GNU version of make by using `gmake`.
676
677 ### GNU Bash
678
679 OpenJDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells
680 are supported.
681
682 At least version 3.2 of GNU Bash must be used.
683
684 ### Autoconf
685
686 If you want to modify the build system itself, you need to install [Autoconf](
687 http://www.gnu.org/software/autoconf).
688
689 However, if you only need to build OpenJDK or if you only edit the actual
690 OpenJDK source files, there is no dependency on autoconf, since the source
691 distribution includes a pre-generated `configure` shell script.
692
693 See the section on [Autoconf Details](#autoconf-details) for details on how
694 OpenJDK uses autoconf. This is especially important if you plan to contribute
695 changes to OpenJDK that modifies the build system.
696
697 ## Running Configure
698
699 To build OpenJDK, you need a "configuration", which consists of a directory
700 where to store the build output, coupled with information about the platform,
701 the specific build machine, and choices that affect how OpenJDK is built.
702
703 The configuration is created by the `configure` script. The basic invocation of
704 the `configure` script looks like this:
705
706 ```
707 bash configure [options]
708 ```
709
710 This will create an output directory containing the configuration and setup an
711 area for the build result. This directory typically looks like
712 `build/linux-x64-normal-server-release`, but the actual name depends on your
713 specific configuration. (It can also be set directly, see [Using Multiple
714 Configurations](#using-multiple-configurations)). This directory is referred to
715 as `$BUILD` in this documentation.
716
717 `configure` will try to figure out what system you are running on and where all
718 necessary build components are. If you have all prerequisites for building
719 installed, it should find everything. If it fails to detect any component
720 automatically, it will exit and inform you about the problem.
721
722 Some command line examples:
723
724 * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`:
725 ```
726 bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32
727 ```
728
729 * Create a debug build with the `server` JVM and DTrace enabled:
730 ```
731 bash configure --enable-debug --with-jvm-variants=server --enable-dtrace
732 ```
733
734 ### Common Configure Arguments
735
736 Here follows some of the most common and important `configure` argument.
737
738 To get up-to-date information on *all* available `configure` argument, please
739 run:
740 ```
741 bash configure --help
742 ```
743
744 (Note that this help text also include general autoconf options, like
745 `--dvidir`, that is not relevant to OpenJDK. To list only OpenJDK specific
746 features, use `bash configure --help=short` instead.)
747
748 #### Configure Arguments for Tailoring the Build
749
750 * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand
751 for `--with-debug-level=fastdebug`)
752 * `--with-debug-level=<level>` - Set the debug level, which can be `release`,
753 `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized`
754 is variant of `release` with additional Hotspot debug code.
755 * `--with-native-debug-symbols=<method>` - Specify if and how native debug
756 symbols should be built. Available methods are `none`, `internal`,
757 `external`, `zipped`. Default behavior depends on platform. See [Native
758 Debug Symbols](#native-debug-symbols) for more details.
759 * `--with-version-string=<string>` - Specify the version string this build
760 will be identified with.
761 * `--with-version-<part>=<value>` - A group of options, where `<part>` can be
762 any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use
763 these options to modify just the corresponding part of the version string
764 from the default, or the value provided by `--with-version-string`.
765 * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant
766 (or variants) of Hotspot. Valid variants are: `server`, `client`,
767 `minimal`, `core`, `zero`, `zeroshark`, `custom`. Note that not all
768 variants are possible to combine in a single build.
769 * `--with-jvm-features=<feature>[,<feature>...]` - Use the specified JVM
770 features when building Hotspot. The list of features will be enabled on top
771 of the default list. For the `custom` JVM variant, this default list is
772 empty. A complete list of available JVM features can be found using `bash
773 configure --help`.
774 * `--with-target-bits=<bits>` - Create a target binary suitable for running
775 on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build
776 platform, instead of doing a full cross-compile. (This is known as a
777 *reduced* build.)
778
779 #### Configure Arguments for Native Compilation
780
781 * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources
782 * `--with-sysroot=<path>` - Use this directory as sysroot
783 * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the
784 default path when searching for all kinds of binaries
785 * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when
786 searching for toolchain binaries (compilers etc)
787 * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C
788 files
789 * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++
790 files
791 * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK
792 libraries
793
794 #### Configure Arguments for External Dependencies
795
796 * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK](
797 #boot-jdk-requirements)
798 * `--with-freetype=<path>` - Set the path to [FreeType](#freetype)
799 * `--with-cups=<path>` - Set the path to [CUPS](#cups)
800 * `--with-x=<path>` - Set the path to [X11](#x11)
801 * `--with-alsa=<path>` - Set the path to [ALSA](#alsa)
802 * `--with-libffi=<path>` - Set the path to [libffi](#libffi)
803 * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests](
804 #running-tests)
805
806 Certain third-party libraries used by OpenJDK (libjpeg, giflib, libpng, lcms
807 and zlib) are included in the OpenJDK repository. The default behavior of the
808 OpenJDK build is to use this version of these libraries, but they might be
809 replaced by an external version. To do so, specify `system` as the `<source>`
810 option in these arguments. (The default is `bundled`).
811
812 * `--with-libjpeg=<source>` - Use the specified source for libjpeg
813 * `--with-giflib=<source>` - Use the specified source for giflib
814 * `--with-libpng=<source>` - Use the specified source for libpng
815 * `--with-lcms=<source>` - Use the specified source for lcms
816 * `--with-zlib=<source>` - Use the specified source for zlib
817
818 On Linux, it is possible to select either static or dynamic linking of the C++
819 runtime. The default is static linking, with dynamic linking as fallback if the
820 static library is not found.
821
822 * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic`
823 or `default`) for linking the C++ runtime.
824
825 ### Configure Control Variables
826
827 It is possible to control certain aspects of `configure` by overriding the
828 value of `configure` variables, either on the command line or in the
829 environment.
830
831 Normally, this is **not recommended**. If used improperly, it can lead to a
832 broken configuration. Unless you're well versed in the build system, this is
833 hard to use properly. Therefore, `configure` will print a warning if this is
834 detected.
835
836 However, there are a few `configure` variables, known as *control variables*
837 that are supposed to be overriden on the command line. These are variables that
838 describe the location of tools needed by the build, like `MAKE` or `GREP`. If
839 any such variable is specified, `configure` will use that value instead of
840 trying to autodetect the tool. For instance, `bash configure
841 MAKE=/opt/gnumake4.0/bin/make`.
842
843 If a configure argument exists, use that instead, e.g. use `--with-jtreg`
844 instead of setting `JTREGEXE`.
845
846 Also note that, despite what autoconf claims, setting `CFLAGS` will not
847 accomplish anything. Instead use `--with-extra-cflags` (and similar for
848 `cxxflags` and `ldflags`).
849
850 ## Running Make
851
852 When you have a proper configuration, all you need to do to build OpenJDK is to
853 run `make`. (But see the warning at [GNU Make](#gnu-make) about running the
854 correct version of make.)
855
856 When running `make` without any arguments, the default target is used, which is
857 the same as running `make default` or `make jdk`. This will build a minimal (or
858 roughly minimal) set of compiled output (known as an "exploded image") needed
859 for a developer to actually execute the newly built JDK. The idea is that in an
860 incremental development fashion, when doing a normal make, you should only
861 spend time recompiling what's changed (making it purely incremental) and only
862 do the work that's needed to actually run and test your code.
863
864 The output of the exploded image resides in `$BUILD/jdk`. You can test the
865 newly built JDK like this: `$BUILD/jdk/bin/java -version`.
866
867 ### Common Make Targets
868
869 Apart from the default target, here are some common make targets:
870
871 * `hotspot` - Build all of hotspot (but only hotspot)
872 * `hotspot-<variant>` - Build just the specified jvm variant
873 * `images` or `product-images` - Build the JRE and JDK images
874 * `docs` or `docs-image` - Build the documentation image
875 * `test-image` - Build the test image
876 * `all` or `all-images` - Build all images (product, docs and test)
877 * `bootcycle-images` - Build images twice, second time with newly built JDK
878 (good for testing)
879 * `clean` - Remove all files generated by make, but not those generated by
880 configure
881 * `dist-clean` - Remove all files, including configuration
882
883 Run `make help` to get an up-to-date list of important make targets and make
884 control variables.
885
886 It is possible to build just a single module, a single phase, or a single phase
887 of a single module, by creating make targets according to these followin
888 patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`,
889 `launchers`, `libs` or `rmic`. See [Using Fine-Grained Make Targets](
890 #using-fine-grained-make-targets) for more details about this functionality.
891
892 * `<phase>` - Build the specified phase and everything it depends on
893 * `<module>` - Build the specified module and everything it depends on
894 * `<module>-<phase>` - Compile the specified phase for the specified module
895 and everything it depends on
896
897 Similarly, it is possible to clean just a part of the build by creating make
898 targets according to these patterns:
899
900 * `clean-<outputdir>` - Remove the subdir in the output dir with the name
901 * `clean-<phase>` - Remove all build results related to a certain build
902 phase
903 * `clean-<module>` - Remove all build results related to a certain module
904 * `clean-<module>-<phase>` - Remove all build results related to a certain
905 module and phase
906
907 ### Make Control Variables
908
909 It is possible to control `make` behavior by overriding the value of `make`
910 variables, either on the command line or in the environment.
911
912 Normally, this is **not recommended**. If used improperly, it can lead to a
913 broken build. Unless you're well versed in the build system, this is hard to
914 use properly. Therefore, `make` will print a warning if this is detected.
915
916 However, there are a few `make` variables, known as *control variables* that
917 are supposed to be overriden on the command line. These make up the "make time"
918 configuration, as opposed to the "configure time" configuration.
919
920 #### General Make Control Variables
921
922 * `JOBS` - Specify the number of jobs to build with. See [Build
923 Performance](#build-performance).
924 * `LOG` - Specify the logging level and functionality. See [Checking the
925 Build Log File](#checking-the-build-log-file)
926 * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using
927 Multiple Configurations](#using-multiple-configurations)
928
929 #### Test Make Control Variables
930
931 These make control variables only make sense when running tests. Please see
932 [Testing OpenJDK](testing.html) for details.
933
934 * `TEST`
935 * `TEST_JOBS`
936 * `JTREG`
937 * `GTEST`
938
939 #### Advanced Make Control Variables
940
941 These advanced make control variables can be potentially unsafe. See [Hints and
942 Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and
943 [Understanding the Build System](#understanding-the-build-system) for details.
944
945 * `SPEC`
946 * `CONF_CHECK`
947 * `COMPARE_BUILD`
948 * `JDK_FILTER`
949
950 ## Running Tests
951
952 Most of the OpenJDK tests are using the [JTReg](http://openjdk.java.net/jtreg)
953 test framework. Make sure that your configuration knows where to find your
954 installation of JTReg. If this is not picked up automatically, use the
955 `--with-jtreg=<path to jtreg home>` option to point to the JTReg framework.
956 Note that this option should point to the JTReg home, i.e. the top directory,
957 containing `lib/jtreg.jar` etc.
958
959 To execute the most basic tests (tier 1), use:
960 ```
961 make run-test-tier1
962 ```
963
964 For more details on how to run tests, please see the [Testing
965 OpenJDK](testing.html) document.
966
967 ## Cross-compiling
968
969 Cross-compiling means using one platform (the *build* platform) to generate
970 output that can ran on another platform (the *target* platform).
971
972 The typical reason for cross-compiling is that the build is performed on a more
973 powerful desktop computer, but the resulting binaries will be able to run on a
974 different, typically low-performing system. Most of the complications that
975 arise when building for embedded is due to this separation of *build* and
976 *target* systems.
977
978 This requires a more complex setup and build procedure. This section assumes
979 you are familiar with cross-compiling in general, and will only deal with the
980 particularities of cross-compiling OpenJDK. If you are new to cross-compiling,
981 please see the [external links at Wikipedia](
982 https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start
983 on reading materials.
984
985 Cross-compiling OpenJDK requires you to be able to build both for the build
986 platform and for the target platform. The reason for the former is that we need
987 to build and execute tools during the build process, both native tools and Java
988 tools.
989
990 If all you want to do is to compile a 32-bit version, for the same OS, on a
991 64-bit machine, consider using `--with-target-bits=32` instead of doing a
992 full-blown cross-compilation. (While this surely is possible, it's a lot more
993 work and will take much longer to build.)
994
995 ### Boot JDK and Build JDK
996
997 When cross-compiling, make sure you use a boot JDK that runs on the *build*
998 system, and not on the *target* system.
999
1000 To be able to build, we need a "Build JDK", which is a JDK built from the
1001 current sources (that is, the same as the end result of the entire build
1002 process), but able to run on the *build* system, and not the *target* system.
1003 (In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when
1004 building JDK 9.)
1005
1006 The build process will create a minimal Build JDK for you, as part of building.
1007 To speed up the build, you can use `--with-build-jdk` to `configure` to point
1008 to a pre-built Build JDK. Please note that the build result is unpredictable,
1009 and can possibly break in subtle ways, if the Build JDK does not **exactly**
1010 match the current sources.
1011
1012 ### Specifying the Target Platform
1013
1014 You *must* specify the target platform when cross-compiling. Doing so will also
1015 automatically turn the build into a cross-compiling mode. The simplest way to
1016 do this is to use the `--openjdk-target` argument, e.g.
1017 `--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`.
1018 This will automatically set the `--build`, `--host` and `--target` options for
1019 autoconf, which can otherwise be confusing. (In autoconf terminology, the
1020 "target" is known as "host", and "target" is used for building a Canadian
1021 cross-compiler.)
1022
1023 ### Toolchain Considerations
1024
1025 You will need two copies of your toolchain, one which generates output that can
1026 run on the target system (the normal, or *target*, toolchain), and one that
1027 generates output that can run on the build system (the *build* toolchain). Note
1028 that cross-compiling is only supported for gcc at the time being. The gcc
1029 standard is to prefix cross-compiling toolchains with the target denominator.
1030 If you follow this standard, `configure` is likely to pick up the toolchain
1031 correctly.
1032
1033 The *build* toolchain will be autodetected just the same way the normal
1034 *build*/*target* toolchain will be autodetected when not cross-compiling. If
1035 this is not what you want, or if the autodetection fails, you can specify a
1036 devkit containing the *build* toolchain using `--with-build-devkit` to
1037 `configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments.
1038
1039 It is often helpful to locate the cross-compilation tools, headers and
1040 libraries in a separate directory, outside the normal path, and point out that
1041 directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and
1042 appending the directory when searching for cross-compilations tools
1043 (`--with-toolchain-path`). As a compact form, you can also use `--with-devkit`
1044 to point to a single directory, if it is correctly setup. (See `basics.m4` for
1045 details.)
1046
1047 If you are unsure what toolchain and versions to use, these have been proved
1048 working at the time of writing:
1049
1050 * [aarch64](
1051 https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-linux-gnu-4.8-2013.11_linux.tar.xz)
1052 * [arm 32-bit hardware floating point](
1053 https://launchpad.net/linaro-toolchain-unsupported/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux.tar.bz2)
1054
1055 ### Native Libraries
1056
1057 You will need copies of external native libraries for the *target* system,
1058 present on the *build* machine while building.
1059
1060 Take care not to replace the *build* system's version of these libraries by
1061 mistake, since that can render the *build* machine unusable.
1062
1063 Make sure that the libraries you point to (ALSA, X11, etc) are for the
1064 *target*, not the *build*, platform.
1065
1066 #### ALSA
1067
1068 You will need alsa libraries suitable for your *target* system. For most cases,
1069 using Debian's pre-built libraries work fine.
1070
1071 Note that alsa is needed even if you only want to build a headless JDK.
1072
1073 * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and
1074 search for the `libasound2` and `libasound2-dev` packages for your *target*
1075 system. Download them to /tmp.
1076
1077 * Install the libraries into the cross-compilation toolchain. For instance:
1078 ```
1079 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc
1080 dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb .
1081 dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb .
1082 ```
1083
1084 * If alsa is not properly detected by `configure`, you can point it out by
1085 `--with-alsa`.
1086
1087 #### X11
1088
1089 You will need X11 libraries suitable for your *target* system. For most cases,
1090 using Debian's pre-built libraries work fine.
1091
1092 Note that X11 is needed even if you only want to build a headless JDK.
1093
1094 * Go to [Debian Package Search](https://www.debian.org/distrib/packages),
1095 search for the following packages for your *target* system, and download them
1096 to /tmp/target-x11:
1097 * libxi
1098 * libxi-dev
1099 * x11proto-core-dev
1100 * x11proto-input-dev
1101 * x11proto-kb-dev
1102 * x11proto-render-dev
1103 * x11proto-xext-dev
1104 * libice-dev
1105 * libxrender
1106 * libxrender-dev
1107 * libsm-dev
1108 * libxt-dev
1109 * libx11
1110 * libx11-dev
1111 * libxtst
1112 * libxtst-dev
1113 * libxext
1114 * libxext-dev
1115
1116 * Install the libraries into the cross-compilation toolchain. For instance:
1117 ```
1118 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr
1119 mkdir X11R6
1120 cd X11R6
1121 for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done
1122 mv usr/* .
1123 cd lib
1124 cp arm-linux-gnueabihf/* .
1125 ```
1126
1127 You can ignore the following messages. These libraries are not needed to
1128 successfully complete a full JDK build.
1129 ```
1130 cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory
1131 cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory
1132 cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory
1133 ```
1134
1135 * If the X11 libraries are not properly detected by `configure`, you can
1136 point them out by `--with-x`.
1137
1138 ### Building for ARM/aarch64
1139
1140 A common cross-compilation target is the ARM CPU. When building for ARM, it is
1141 useful to set the ABI profile. A number of pre-defined ABI profiles are
1142 available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt,
1143 armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer
1144 properly supported on OpenJDK.
1145
1146 OpenJDK contains two different ports for the aarch64 platform, one is the
1147 original aarch64 port from the [AArch64 Port Project](
1148 http://openjdk.java.net/projects/aarch64-port) and one is a 64-bit version of
1149 the Oracle contributed ARM port. When targeting aarch64, by the default the
1150 original aarch64 port is used. To select the Oracle ARM 64 port, use
1151 `--with-cpu-port=arm64`. Also set the corresponding value (`aarch64` or
1152 `arm64`) to --with-abi-profile, to ensure a consistent build.
1153
1154 ### Verifying the Build
1155
1156 The build will end up in a directory named like
1157 `build/linux-arm-normal-server-release`.
1158
1159 Inside this build output directory, the `images/jdk` and `images/jre` will
1160 contain the newly built JDK and JRE, respectively, for your *target* system.
1161
1162 Copy these folders to your *target* system. Then you can run e.g.
1163 `images/jdk/bin/java -version`.
1164
1165 ## Build Performance
1166
1167 Building OpenJDK requires a lot of horsepower. Some of the build tools can be
1168 adjusted to utilize more or less of resources such as parallel threads and
1169 memory. The `configure` script analyzes your system and selects reasonable
1170 values for such options based on your hardware. If you encounter resource
1171 problems, such as out of memory conditions, you can modify the detected values
1172 with:
1173
1174 * `--with-num-cores` -- number of cores in the build system, e.g.
1175 `--with-num-cores=8`.
1176
1177 * `--with-memory-size` -- memory (in MB) available in the build system, e.g.
1178 `--with-memory-size=1024`
1179
1180 You can also specify directly the number of build jobs to use with
1181 `--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag
1182 to `make`. In most cases it will be ignored by the makefiles, but it can cause
1183 problems for some make targets.
1184
1185 It might also be necessary to specify the JVM arguments passed to the Boot JDK,
1186 using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the
1187 default JVM arguments passed to the Boot JDK.
1188
1189 At the end of a successful execution of `configure`, you will get a performance
1190 summary, indicating how well the build will perform. Here you will also get
1191 performance hints. If you want to build fast, pay attention to those!
1192
1193 If you want to tweak build performance, run with `make LOG=info` to get a build
1194 time summary at the end of the build process.
1195
1196 ### Disk Speed
1197
1198 If you are using network shares, e.g. via NFS, for your source code, make sure
1199 the build directory is situated on local disk (e.g. by `ln -s
1200 /localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely
1201 high for building on a network share; close to unusable.
1202
1203 Also, make sure that your build tools (including Boot JDK and toolchain) is
1204 located on a local disk and not a network share.
1205
1206 As has been stressed elsewhere, do use SSD for source code and build directory,
1207 as well as (if possible) the build tools.
1208
1209 ### Virus Checking
1210
1211 The use of virus checking software, especially on Windows, can *significantly*
1212 slow down building of OpenJDK. If possible, turn off such software, or exclude
1213 the directory containing the OpenJDK source code from on-the-fly checking.
1214
1215 ### Ccache
1216
1217 The OpenJDK build supports building with ccache when using gcc or clang. Using
1218 ccache can radically speed up compilation of native code if you often rebuild
1219 the same sources. Your milage may vary however, so we recommend evaluating it
1220 for yourself. To enable it, make sure it's on the path and configure with
1221 `--enable-ccache`.
1222
1223 ### Precompiled Headers
1224
1225 By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains
1226 were it is properly supported (clang, gcc, and Visual Studio). Normally, this
1227 speeds up the build process, but in some circumstances, it can actually slow
1228 things down.
1229
1230 You can experiment by disabling precompiled headers using
1231 `--disable-precompiled-headers`.
1232
1233 ### Icecc / icecream
1234
1235 [icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a
1236 distributed compiler network. If you have multiple machines available for
1237 building OpenJDK, you can drastically cut individual build times by utilizing
1238 it.
1239
1240 To use, setup an icecc network, and install icecc on the build machine. Then
1241 run `configure` using `--enable-icecc`.
1242
1243 ### Using sjavac
1244
1245 To speed up Java compilation, especially incremental compilations, you can try
1246 the experimental sjavac compiler by using `--enable-sjavac`.
1247
1248 ### Building the Right Target
1249
1250 Selecting the proper target to build can have dramatic impact on build time.
1251 For normal usage, `jdk` or the default target is just fine. You only need to
1252 build `images` for shipping, or if your tests require it.
1253
1254 See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on
1255 how to build an even smaller subset of the product.
1256
1257 ## Troubleshooting
1258
1259 If your build fails, it can sometimes be difficult to pinpoint the problem or
1260 find a proper solution.
1261
1262 ### Locating the Source of the Error
1263
1264 When a build fails, it can be hard to pinpoint the actual cause of the error.
1265 In a typical build process, different parts of the product build in parallel,
1266 with the output interlaced.
1267
1268 #### Build Failure Summary
1269
1270 To help you, the build system will print a failure summary at the end. It looks
1271 like this:
1272
1273 ```
1274 ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2)
1275
1276 === Output from failing command(s) repeated here ===
1277 * For target hotspot_variant-server_libjvm_objs_psMemoryPool.o:
1278 /localhome/hg/jdk9-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type
1279 ... (rest of output omitted)
1280
1281 * All command lines available in /localhome/hg/jdk9-sandbox/build/linux-x64/make-support/failure-logs.
1282 === End of repeated output ===
1283
1284 === Make failed targets repeated here ===
1285 lib/CompileJvm.gmk:207: recipe for target '/localhome/hg/jdk9-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed
1286 make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed
1287 === End of repeated output ===
1288
1289 Hint: Try searching the build log for the name of the first failed target.
1290 Hint: If caused by a warning, try configure --disable-warnings-as-errors.
1291 ```
1292
1293 Let's break it down! First, the selected configuration, and the top-level
1294 target you entered on the command line that caused the failure is printed.
1295
1296 Then, between the `Output from failing command(s) repeated here` and `End of
1297 repeated output` the first lines of output (stdout and stderr) from the actual
1298 failing command is repeated. In most cases, this is the error message that
1299 caused the build to fail. If multiple commands were failing (this can happen in
1300 a parallel build), output from all failed commands will be printed here.
1301
1302 The path to the `failure-logs` directory is printed. In this file you will find
1303 a `<target>.log` file that contains the output from this command in its
1304 entirety, and also a `<target>.cmd`, which contain the complete command line
1305 used for running this command. You can re-run the failing command by executing
1306 `. <path to failure-logs>/<target>.cmd` in your shell.
1307
1308 Another way to trace the failure is to follow the chain of make targets, from
1309 top-level targets to individual file targets. Between `Make failed targets
1310 repeated here` and `End of repeated output` the output from make showing this
1311 chain is repeated. The first failed recipe will typically contain the full path
1312 to the file in question that failed to compile. Following lines will show a
1313 trace of make targets why we ended up trying to compile that file.
1314
1315 Finally, some hints are given on how to locate the error in the complete log.
1316 In this example, we would try searching the log file for "`psMemoryPool.o`".
1317 Another way to quickly locate make errors in the log is to search for "`]
1318 Error`" or "`***`".
1319
1320 Note that the build failure summary will only help you if the issue was a
1321 compilation failure or similar. If the problem is more esoteric, or is due to
1322 errors in the build machinery, you will likely get empty output logs, and `No
1323 indication of failed target found` instead of the make target chain.
1324
1325 #### Checking the Build Log File
1326
1327 The output (stdout and stderr) from the latest build is always stored in
1328 `$BUILD/build.log`. The previous build log is stored as `build.log.old`. This
1329 means that it is not necessary to redirect the build output yourself if you
1330 want to process it.
1331
1332 You can increase the verbosity of the log file, by the `LOG` control variable
1333 to `make`. If you want to see the command lines used in compilations, use
1334 `LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug`
1335 or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g.
1336 `LOG=info,cmdlines`. The `debug` log level will show most shell commands
1337 executed by make, and `trace` will show all. Beware that both these log levels
1338 will produce a massive build log!
1339
1340 ### Fixing Unexpected Build Failures
1341
1342 Most of the time, the build will fail due to incorrect changes in the source
1343 code.
1344
1345 Sometimes the build can fail with no apparent changes that have caused the
1346 failure. If this is the first time you are building OpenJDK on this particular
1347 computer, and the build fails, the problem is likely with your build
1348 environment. But even if you have previously built OpenJDK with success, and it
1349 now fails, your build environment might have changed (perhaps due to OS
1350 upgrades or similar). But most likely, such failures are due to problems with
1351 the incremental rebuild.
1352
1353 #### Problems with the Build Environment
1354
1355 Make sure your configuration is correct. Re-run `configure`, and look for any
1356 warnings. Warnings that appear in the middle of the `configure` output is also
1357 repeated at the end, after the summary. The entire log is stored in
1358 `$BUILD/configure.log`.
1359
1360 Verify that the summary at the end looks correct. Are you indeed using the Boot
1361 JDK and native toolchain that you expect?
1362
1363 By default, OpenJDK has a strict approach where warnings from the compiler is
1364 considered errors which fail the build. For very new or very old compiler
1365 versions, this can trigger new classes of warnings, which thus fails the build.
1366 Run `configure` with `--disable-warnings-as-errors` to turn of this behavior.
1367 (The warnings will still show, but not make the build fail.)
1368
1369 #### Problems with Incremental Rebuilds
1370
1371 Incremental rebuilds mean that when you modify part of the product, only the
1372 affected parts get rebuilt. While this works great in most cases, and
1373 significantly speed up the development process, from time to time complex
1374 interdependencies will result in an incorrect build result. This is the most
1375 common cause for unexpected build problems, together with inconsistencies
1376 between the different Mercurial repositories in the forest.
1377
1378 Here are a suggested list of things to try if you are having unexpected build
1379 problems. Each step requires more time than the one before, so try them in
1380 order. Most issues will be solved at step 1 or 2.
1381
1382 1. Make sure your forest is up-to-date
1383
1384 Run `bash get_source.sh` to make sure you have the latest version of all
1385 repositories.
1386
1387 2. Clean build results
1388
1389 The simplest way to fix incremental rebuild issues is to run `make clean`.
1390 This will remove all build results, but not the configuration or any build
1391 system support artifacts. In most cases, this will solve build errors
1392 resulting from incremental build mismatches.
1393
1394 3. Completely clean the build directory.
1395
1396 If this does not work, the next step is to run `make dist-clean`, or
1397 removing the build output directory (`$BUILD`). This will clean all
1398 generated output, including your configuration. You will need to re-run
1399 `configure` after this step. A good idea is to run `make
1400 print-configuration` before running `make dist-clean`, as this will print
1401 your current `configure` command line. Here's a way to do this:
1402
1403 ```
1404 make print-configuration > current-configuration
1405 make dist-clean
1406 bash configure $(cat current-configuration)
1407 make
1408 ```
1409
1410 4. Re-clone the Mercurial forest
1411
1412 Sometimes the Mercurial repositories themselves gets in a state that causes
1413 the product to be un-buildable. In such a case, the simplest solution is
1414 often the "sledgehammer approach": delete the entire forest, and re-clone
1415 it. If you have local changes, save them first to a different location
1416 using `hg export`.
1417
1418 ### Specific Build Issues
1419
1420 #### Clock Skew
1421
1422 If you get an error message like this:
1423 ```
1424 File 'xxx' has modification time in the future.
1425 Clock skew detected. Your build may be incomplete.
1426 ```
1427 then the clock on your build machine is out of sync with the timestamps on the
1428 source files. Other errors, apparently unrelated but in fact caused by the
1429 clock skew, can occur along with the clock skew warnings. These secondary
1430 errors may tend to obscure the fact that the true root cause of the problem is
1431 an out-of-sync clock.
1432
1433 If you see these warnings, reset the clock on the build machine, run `make
1434 clean` and restart the build.
1435
1436 #### Out of Memory Errors
1437
1438 On Solaris, you might get an error message like this:
1439 ```
1440 Trouble writing out table to disk
1441 ```
1442 To solve this, increase the amount of swap space on your build machine.
1443
1444 On Windows, you might get error messages like this:
1445 ```
1446 fatal error - couldn't allocate heap
1447 cannot create ... Permission denied
1448 spawn failed
1449 ```
1450 This can be a sign of a Cygwin problem. See the information about solving
1451 problems in the [Cygwin](#cygwin) section. Rebooting the computer might help
1452 temporarily.
1453
1454 ### Getting Help
1455
1456 If none of the suggestions in this document helps you, or if you find what you
1457 believe is a bug in the build system, please contact the Build Group by sending
1458 a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net).
1459 Please include the relevant parts of the configure and/or build log.
1460
1461 If you need general help or advice about developing for OpenJDK, you can also
1462 contact the Adoption Group. See the section on [Contributing to OpenJDK](
1463 #contributing-to-openjdk) for more information.
1464
1465 ## Hints and Suggestions for Advanced Users
1466
1467 ### Setting Up a Forest for Pushing Changes (defpath)
1468
1469 To help you prepare a proper push path for a Mercurial repository, there exists
1470 a useful tool known as [defpath](
1471 http://openjdk.java.net/projects/code-tools/defpath). It will help you setup a
1472 proper push path for pushing changes to OpenJDK.
1473
1474 Install the extension by cloning
1475 `http://hg.openjdk.java.net/code-tools/defpath` and updating your `.hgrc` file.
1476 Here's one way to do this:
1477
1478 ```
1479 cd ~
1480 mkdir hg-ext
1481 cd hg-ext
1482 hg clone http://hg.openjdk.java.net/code-tools/defpath
1483 cat << EOT >> ~/.hgrc
1484 [extensions]
1485 defpath=~/hg-ext/defpath/defpath.py
1486 EOT
1487 ```
1488
1489 You can now setup a proper push path using:
1490 ```
1491 hg defpath -d -u <your OpenJDK username>
1492 ```
1493
1494 If you also have the `trees` extension installed in Mercurial, you will
1495 automatically get a `tdefpath` command, which is even more useful. By running
1496 `hg tdefpath -du <username>` in the top repository of your forest, all repos
1497 will get setup automatically. This is the recommended usage.
1498
1499 ### Bash Completion
1500
1501 The `configure` and `make` commands tries to play nice with bash command-line
1502 completion (using `<tab>` or `<tab><tab>`). To use this functionality, make
1503 sure you enable completion in your `~/.bashrc` (see instructions for bash in
1504 your operating system).
1505
1506 Make completion will work out of the box, and will complete valid make targets.
1507 For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`.
1508
1509 The `configure` script can get completion for options, but for this to work you
1510 need to help `bash` on the way. The standard way of running the script, `bash
1511 configure`, will not be understood by bash completion. You need `configure` to
1512 be the command to run. One way to achieve this is to add a simple helper script
1513 to your path:
1514
1515 ```
1516 cat << EOT > /tmp/configure
1517 #!/bin/bash
1518 if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then
1519 echo >&2 "Abort: Trying to call configure helper recursively"
1520 exit 1
1521 fi
1522
1523 bash \$PWD/configure "\$@"
1524 EOT
1525 chmod +x /tmp/configure
1526 sudo mv /tmp/configure /usr/local/bin
1527 ```
1528
1529 Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`.
1530
1531 ### Using Multiple Configurations
1532
1533 You can have multiple configurations for a single source forest. When you
1534 create a new configuration, run `configure --with-conf-name=<name>` to create a
1535 configuration with the name `<name>`. Alternatively, you can create a directory
1536 under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd
1537 build/<name> && bash ../../configure`.
1538
1539 Then you can build that configuration using `make CONF_NAME=<name>` or `make
1540 CONF=<pattern>`, where `<pattern>` is a substring matching one or several
1541 configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will
1542 match *all* available configuration, so `make CONF= hotspot` will build the
1543 `hotspot` target for all configurations. Alternatively, you can execute `make`
1544 in the configuration directory, e.g. `cd build/<name> && make`.
1545
1546 ### Handling Reconfigurations
1547
1548 If you update the forest and part of the configure script has changed, the
1549 build system will force you to re-run `configure`.
1550
1551 Most of the time, you will be fine by running `configure` again with the same
1552 arguments as the last time, which can easily be performed by `make
1553 reconfigure`. To simplify this, you can use the `CONF_CHECK` make control
1554 variable, either as `make CONF_CHECK=auto`, or by setting an environment
1555 variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc`
1556 file, `make` will always run `reconfigure` automatically whenever the configure
1557 script has changed.
1558
1559 You can also use `CONF_CHECK=ignore` to skip the check for a needed configure
1560 update. This might speed up the build, but comes at the risk of an incorrect
1561 build result. This is only recommended if you know what you're doing.
1562
1563 From time to time, you will also need to modify the command line to `configure`
1564 due to changes. Use `make print-configure` to show the command line used for
1565 your current configuration.
1566
1567 ### Using Fine-Grained Make Targets
1568
1569 The default behavior for make is to create consistent and correct output, at
1570 the expense of build speed, if necessary.
1571
1572 If you are prepared to take some risk of an incorrect build, and know enough of
1573 the system to understand how things build and interact, you can speed up the
1574 build process considerably by instructing make to only build a portion of the
1575 product.
1576
1577 #### Building Individual Modules
1578
1579 The safe way to use fine-grained make targets is to use the module specific
1580 make targets. All source code in JDK 9 is organized so it belongs to a module,
1581 e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific module, by
1582 giving it as make target: `make jdk.jdwp.agent`. If the specified module
1583 depends on other modules (e.g. `java.base`), those modules will be built first.
1584
1585 You can also specify a set of modules, just as you can always specify a set of
1586 make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi
1587 jdk.crypto.ucrypto`
1588
1589 #### Building Individual Module Phases
1590
1591 The build process for each module is divided into separate phases. Not all
1592 modules need all phases. Which are needed depends on what kind of source code
1593 and other artifact the module consists of. The phases are:
1594
1595 * `gensrc` (Generate source code to compile)
1596 * `gendata` (Generate non-source code artifacts)
1597 * `copy` (Copy resource artifacts)
1598 * `java` (Compile Java code)
1599 * `launchers` (Compile native executables)
1600 * `libs` (Compile native libraries)
1601 * `rmic` (Run the `rmic` tool)
1602
1603 You can build only a single phase for a module by using the notation
1604 `$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`,
1605 use `make java.base-gensrc`.
1606
1607 Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if
1608 present). Make will build all needed prerequisites before building the
1609 requested phase.
1610
1611 #### Skipping the Dependency Check
1612
1613 When using an iterative development style with frequent quick rebuilds, the
1614 dependency check made by make can take up a significant portion of the time
1615 spent on the rebuild. In such cases, it can be useful to bypass the dependency
1616 check in make.
1617
1618 > **Note that if used incorrectly, this can lead to a broken build!**
1619
1620 To achieve this, append `-only` to the build target. For instance, `make
1621 jdk.jdwp.agent-java-only` will *only* build the `java` phase of the
1622 `jdk.jdwp.agent` module. If the required dependencies are not present, the
1623 build can fail. On the other hand, the execution time measures in milliseconds.
1624
1625 A useful pattern is to build the first time normally (e.g. `make
1626 jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target.
1627
1628 #### Rebuilding Part of java.base (JDK\_FILTER)
1629
1630 If you are modifying files in `java.base`, which is the by far largest module
1631 in OpenJDK, then you need to rebuild all those files whenever a single file has
1632 changed. (This inefficiency will hopefully be addressed in JDK 10.)
1633
1634 As a hack, you can use the make control variable `JDK_FILTER` to specify a
1635 pattern that will be used to limit the set of files being recompiled. For
1636 instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods,
1637 `make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation
1638 to files in the `javax.crypto` package.
1639
1640 ### Learn About Mercurial
1641
1642 To become an efficient OpenJDK developer, it is recommended that you invest in
1643 learning Mercurial properly. Here are some links that can get you started:
1644
1645 * [Mercurial for git users](http://www.mercurial-scm.org/wiki/GitConcepts)
1646 * [The official Mercurial tutorial](http://www.mercurial-scm.org/wiki/Tutorial)
1647 * [hg init](http://hginit.com/)
1648 * [Mercurial: The Definitive Guide](http://hgbook.red-bean.com/read/)
1649
1650 ## Understanding the Build System
1651
1652 This section will give you a more technical description on the details of the
1653 build system.
1654
1655 ### Configurations
1656
1657 The build system expects to find one or more configuration. These are
1658 technically defined by the `spec.gmk` in a subdirectory to the `build`
1659 subdirectory. The `spec.gmk` file is generated by `configure`, and contains in
1660 principle the configuration (directly or by files included by `spec.gmk`).
1661
1662 You can, in fact, select a configuration to build by pointing to the `spec.gmk`
1663 file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`.
1664 While this is not the recommended way to call `make` as a user, it is what is
1665 used under the hood by the build system.
1666
1667 ### Build Output Structure
1668
1669 The build output for a configuration will end up in `build/<configuration
1670 name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory
1671 contains the following important directories:
1672
1673 ```
1674 buildtools/
1675 configure-support/
1676 hotspot/
1677 images/
1678 jdk/
1679 make-support/
1680 support/
1681 test-results/
1682 test-support/
1683 ```
1684
1685 This is what they are used for:
1686
1687 * `images`: This is the directory were the output of the `*-image` make
1688 targets end up. For instance, `make jdk-image` ends up in `images/jdk`.
1689
1690 * `jdk`: This is the "exploded image". After `make jdk`, you will be able to
1691 launch the newly built JDK by running `$BUILD/jdk/bin/java`.
1692
1693 * `test-results`: This directory contains the results from running tests.
1694
1695 * `support`: This is an area for intermediate files needed during the build,
1696 e.g. generated source code, object files and class files. Some noteworthy
1697 directories in `support` is `gensrc`, which contains the generated source
1698 code, and the `modules_*` directories, which contains the files in a
1699 per-module hierarchy that will later be collapsed into the `jdk` directory
1700 of the exploded image.
1701
1702 * `buildtools`: This is an area for tools compiled for the build platform
1703 that are used during the rest of the build.
1704
1705 * `hotspot`: This is an area for intermediate files needed when building
1706 hotspot.
1707
1708 * `configure-support`, `make-support` and `test-support`: These directories
1709 contain files that are needed by the build system for `configure`, `make`
1710 and for running tests.
1711
1712 ### Fixpath
1713
1714 Windows path typically look like `C:\User\foo`, while Unix paths look like
1715 `/home/foo`. Tools with roots from Unix often experience issues related to this
1716 mismatch when running on Windows.
1717
1718 In the OpenJDK build, we always use Unix paths internally, and only just before
1719 calling a tool that does not understand Unix paths do we convert them to
1720 Windows paths.
1721
1722 This conversion is done by the `fixpath` tool, which is a small wrapper that
1723 modifies unix-style paths to Windows-style paths in command lines. Fixpath is
1724 compiled automatically by `configure`.
1725
1726 ### Native Debug Symbols
1727
1728 Native libraries and executables can have debug symbol (and other debug
1729 information) associated with them. How this works is very much platform
1730 dependent, but a common problem is that debug symbol information takes a lot of
1731 disk space, but is rarely needed by the end user.
1732
1733 The OpenJDK supports different methods on how to handle debug symbols. The
1734 method used is selected by `--with-native-debug-symbols`, and available methods
1735 are `none`, `internal`, `external`, `zipped`.
1736
1737 * `none` means that no debug symbols will be generated during the build.
1738
1739 * `internal` means that debug symbols will be generated during the build, and
1740 they will be stored in the generated binary.
1741
1742 * `external` means that debug symbols will be generated during the build, and
1743 after the compilation, they will be moved into a separate `.debuginfo` file.
1744 (This was previously known as FDS, Full Debug Symbols).
1745
1746 * `zipped` is like `external`, but the .debuginfo file will also be zipped
1747 into a `.diz` file.
1748
1749 When building for distribution, `zipped` is a good solution. Binaries built
1750 with `internal` is suitable for use by developers, since they facilitate
1751 debugging, but should be stripped before distributed to end users.
1752
1753 ### Autoconf Details
1754
1755 The `configure` script is based on the autoconf framework, but in some details
1756 deviate from a normal autoconf `configure` script.
1757
1758 The `configure` script in the top level directory of OpenJDK is just a thin
1759 wrapper that calls `common/autoconf/configure`. This in turn provides
1760 functionality that is not easily expressed in the normal Autoconf framework,
1761 and then calls into the core of the `configure` script, which is the
1762 `common/autoconf/generated-configure.sh` file.
1763
1764 As the name implies, this file is generated by Autoconf. It is checked in after
1765 regeneration, to alleviate the common user to have to install Autoconf.
1766
1767 The build system will detect if the Autoconf source files have changed, and
1768 will trigger a regeneration of `common/autoconf/generated-configure.sh` if
1769 needed. You can also manually request such an update by `bash
1770 common/autoconf/autogen.sh`.
1771
1772 If you make changes to the build system that requires a re-generation, note the
1773 following:
1774
1775 * You must use *exactly* version 2.69 of autoconf for your patch to be
1776 accepted. This is to avoid spurious changes in the generated file. Note
1777 that Ubuntu 16.04 ships a patched version of autoconf which claims to be
1778 2.69, but is not.
1779
1780 * You do not need to include the generated file in reviews.
1781
1782 * If the generated file needs updating, the Oracle JDK closed counter-part
1783 will also need to be updated. It is very much appreciated if you ask for an
1784 Oracle engineer to sponsor your push so this can be made in tandem.
1785
1786 ### Developing the Build System Itself
1787
1788 This section contains a few remarks about how to develop for the build system
1789 itself. It is not relevant if you are only making changes in the product source
1790 code.
1791
1792 While technically using `make`, the make source files of the OpenJDK does not
1793 resemble most other Makefiles. Instead of listing specific targets and actions
1794 (perhaps using patterns), the basic modus operandi is to call a high-level
1795 function (or properly, macro) from the API in `make/common`. For instance, to
1796 compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module,
1797 a call like this would be made:
1798
1799 ```
1800 $(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \
1801 SETUP := GENERATE_OLDBYTECODE, \
1802 SRC := $(JDK_TOPDIR)/src/jkd.foo/share/classes, \
1803 INCLUDES := jdk/internal/foo, \
1804 BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \
1805 ))
1806 ```
1807
1808 By encapsulating and expressing the high-level knowledge of *what* should be
1809 done, rather than *how* it should be done (as is normal in Makefiles), we can
1810 build a much more powerful and flexible build system.
1811
1812 Correct dependency tracking is paramount. Sloppy dependency tracking will lead
1813 to improper parallelization, or worse, race conditions.
1814
1815 To test for/debug race conditions, try running `make JOBS=1` and `make
1816 JOBS=100` and see if it makes any difference. (It shouldn't).
1817
1818 To compare the output of two different builds and see if, and how, they differ,
1819 run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two
1820 builds you want to compare.
1821
1822 To automatically build two consecutive versions and compare them, use
1823 `COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value
1824 assignments, like this:
1825 ```
1826 make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot
1827 ```
1828 See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`.
1829
1830 To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`.
1831 Use `JOBS=1` to avoid parallelism.
1832
1833 Please check that you adhere to the [Code Conventions for the Build System](
1834 http://openjdk.java.net/groups/build/doc/code-conventions.html) before
1835 submitting patches. Also see the section in [Autoconf Details](
1836 #autoconf-details) about the generated configure script.
1837
1838 ## Contributing to OpenJDK
1839
1840 So, now you've build your OpenJDK, and made your first patch, and want to
1841 contribute it back to the OpenJDK community.
1842
1843 First of all: Thank you! We gladly welcome your contribution to the OpenJDK.
1844 However, please bear in mind that OpenJDK is a massive project, and we must ask
1845 you to follow our rules and guidelines to be able to accept your contribution.
1846
1847 The official place to start is the ['How to contribute' page](
1848 http://openjdk.java.net/contribute/). There is also an official (but somewhat
1849 outdated and skimpy on details) [Developer's Guide](
1850 http://openjdk.java.net/guide/).
1851
1852 If this seems overwhelming to you, the Adoption Group is there to help you! A
1853 good place to start is their ['New Contributor' page](
1854 https://wiki.openjdk.java.net/display/Adoption/New+Contributor), or start
1855 reading the comprehensive [Getting Started Kit](
1856 https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The
1857 Adoption Group will also happily answer any questions you have about
1858 contributing. Contact them by [mail](
1859 http://mail.openjdk.java.net/mailman/listinfo/adoption-discuss) or [IRC](
1860 http://openjdk.java.net/irc/).
1861
1862 ---
1863 # Override styles from the base CSS file that are not ideal for this document.
1864 header-includes:
1865 - '<style type="text/css">pre, code, tt { color: #1d6ae5; }</style>'
1866 ---