1 % Building the JDK
2
3 ## TL;DR (Instructions for the Impatient)
4
5 If you are eager to try out building the JDK, 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 JDK repository that you want to build.
8
9 1. [Get the complete source code](#getting-the-source-code): \
10 `hg clone http://hg.openjdk.java.net/jdk/jdk`
11
12 2. [Run configure](#running-configure): \
13 `bash configure`
14
15 If `configure` fails due to missing dependencies (to either the
16 [toolchain](#native-compiler-toolchain-requirements), [build tools](
17 #build-tools-requirements), [external libraries](
18 #external-library-requirements) or the [boot JDK](#boot-jdk-requirements)),
19 most of the time it prints a suggestion on how to resolve the situation on
20 your platform. Follow the instructions, and try running `bash configure`
21 again.
22
23 3. [Run make](#running-make): \
24 `make images`
25
26 4. Verify your newly built JDK: \
27 `./build/*/images/jdk/bin/java -version`
28
29 5. [Run basic tests](##running-tests): \
30 `make run-test-tier1`
31
32 If any of these steps failed, or if you want to know more about build
33 requirements or build functionality, please continue reading this document.
34
35 ## Introduction
36
37 The JDK is a complex software project. Building it requires a certain amount of
38 technical expertise, a fair number of dependencies on external software, and
39 reasonably powerful hardware.
40
41 If you just want to use the JDK and not build it yourself, this document is not
42 for you. See for instance [OpenJDK installation](
43 http://openjdk.java.net/install) for some methods of installing a prebuilt
44 JDK.
45
46 ## Getting the Source Code
47
48 Make sure you are getting the correct version. As of JDK 10, the source is no
49 longer split into separate repositories so you only need to clone one single
50 repository. At the [OpenJDK Mercurial server](http://hg.openjdk.java.net/) you
51 can see a list of all available repositories. If you want to build an older version,
52 e.g. JDK 8, it is recommended that you get the `jdk8u` forest, which contains
53 incremental updates, instead of the `jdk8` forest, which was frozen at JDK 8 GA.
54
55 If you are new to Mercurial, a good place to start is the [Mercurial Beginner's
56 Guide](http://www.mercurial-scm.org/guide). The rest of this document assumes a
57 working knowledge of Mercurial.
58
59 ### Special Considerations
60
61 For a smooth building experience, it is recommended that you follow these rules
62 on where and how to check out the source code.
63
64 * Do not check out the source code in a path which contains spaces. Chances
65 are the build will not work. This is most likely to be an issue on Windows
66 systems.
67
68 * Do not check out the source code in a path which has a very long name or is
69 nested many levels deep. Chances are you will hit an OS limitation during
70 the build.
71
72 * Put the source code on a local disk, not a network share. If possible, use
73 an SSD. The build process is very disk intensive, and having slow disk
74 access will significantly increase build times. If you need to use a
75 network share for the source code, see below for suggestions on how to keep
76 the build artifacts on a local disk.
77
78 * On Windows, extra care must be taken to make sure the [Cygwin](#cygwin)
79 environment is consistent. It is recommended that you follow this
80 procedure:
81
82 * Create the directory that is going to contain the top directory of the
83 JDK clone by using the `mkdir` command in the Cygwin bash shell.
84 That is, do *not* create it using Windows Explorer. This will ensure
85 that it will have proper Cygwin attributes, and that it's children will
86 inherit those attributes.
87
88 * Do not put the JDK clone in a path under your Cygwin home
89 directory. This is especially important if your user name contains
90 spaces and/or mixed upper and lower case letters.
91
92 * Clone the JDK repository using the Cygwin command line `hg` client
93 as instructed in this document. That is, do *not* use another Mercurial
94 client such as TortoiseHg.
95
96 Failure to follow this procedure might result in hard-to-debug build
97 problems.
98
99 ## Build Hardware Requirements
100
101 The JDK is a massive project, and require machines ranging from decent to
102 powerful to be able to build in a reasonable amount of time, or to be able to
103 complete a build at all.
104
105 We *strongly* recommend usage of an SSD disk for the build, since disk speed is
106 one of the limiting factors for build performance.
107
108 ### Building on x86
109
110 At a minimum, a machine with 2-4 cores is advisable, as well as 2-4 GB of RAM.
111 (The more cores to use, the more memory you need.) At least 6 GB of free disk
112 space is required (8 GB minimum for building on Solaris).
113
114 Even for 32-bit builds, it is recommended to use a 64-bit build machine, and
115 instead create a 32-bit target using `--with-target-bits=32`.
116
117 ### Building on sparc
118
119 At a minimum, a machine with 4 cores is advisable, as well as 4 GB of RAM. (The
120 more cores to use, the more memory you need.) At least 8 GB of free disk space
121 is required.
122
123 ### Building on aarch64
124
125 At a minimum, a machine with 8 cores is advisable, as well as 8 GB of RAM.
126 (The more cores to use, the more memory you need.) At least 6 GB of free disk
127 space is required.
128
129 If you do not have access to sufficiently powerful hardware, it is also
130 possible to use [cross-compiling](#cross-compiling).
131
132 ### Building on 32-bit arm
133
134 This is not recommended. Instead, see the section on [Cross-compiling](
135 #cross-compiling).
136
137 ## Operating System Requirements
138
139 The mainline JDK project supports Linux, Solaris, macOS, AIX and Windows.
140 Support for other operating system, e.g. BSD, exists in separate "port"
141 projects.
142
143 In general, the JDK can be built on a wide range of versions of these operating
144 systems, but the further you deviate from what is tested on a daily basis, the
145 more likely you are to run into problems.
146
147 This table lists the OS versions used by Oracle when building the JDK. Such
148 information is always subject to change, but this table is up to date at the
149 time of writing.
150
151 Operating system Vendor/version used
152 ----------------- -------------------------------------------------------
153 Linux Oracle Enterprise Linux 6.4 / 7.1 (using kernel 3.8.13)
154 Solaris Solaris 11.1 SRU 21.4.1 / 11.2 SRU 5.5
155 macOS Mac OS X 10.9 (Mavericks) / 10.10 (Yosemite)
156 Windows Windows Server 2012 R2
157
158 The double version numbers for Linux, Solaris and macOS is due to the hybrid
159 model used at Oracle, where header files and external libraries from an older
160 version are used when building on a more modern version of the OS.
161
162 The Build Group has a wiki page with [Supported Build Platforms](
163 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms). From
164 time to time, this is updated by contributors to list successes or failures of
165 building on different platforms.
166
167 ### Windows
168
169 Windows XP is not a supported platform, but all newer Windows should be able to
170 build the JDK.
171
172 On Windows, it is important that you pay attention to the instructions in the
173 [Special Considerations](#special-considerations).
174
175 Windows is the only non-POSIX OS supported by the JDK, and as such, requires
176 some extra care. A POSIX support layer is required to build on Windows.
177 Currently, the only supported such layer is Cygwin. (Msys is no longer
178 supported due to a too old bash; msys2 and the new Windows Subsystem for Linux
179 (WSL) would likely be possible to support in a future version but that would
180 require effort to implement.)
181
182 Internally in the build system, all paths are represented as Unix-style paths,
183 e.g. `/cygdrive/c/hg/jdk9/Makefile` rather than `C:\hg\jdk9\Makefile`. This
184 rule also applies to input to the build system, e.g. in arguments to
185 `configure`. So, use `--with-msvcr-dll=/cygdrive/c/msvcr100.dll` rather than
186 `--with-msvcr-dll=c:\msvcr100.dll`. For details on this conversion, see the section
187 on [Fixpath](#fixpath).
188
189 #### Cygwin
190
191 A functioning [Cygwin](http://www.cygwin.com/) environment is thus required for
192 building the JDK on Windows. If you have a 64-bit OS, we strongly recommend
193 using the 64-bit version of Cygwin.
194
195 **Note:** Cygwin has a model of continuously updating all packages without any
196 easy way to install or revert to a specific version of a package. This means
197 that whenever you add or update a package in Cygwin, you might (inadvertently)
198 update tools that are used by the JDK build process, and that can cause
199 unexpected build problems.
200
201 The JDK requires GNU Make 4.0 or greater on Windows. This is usually not a
202 problem, since Cygwin currently only distributes GNU Make at a version above
203 4.0.
204
205 Apart from the basic Cygwin installation, the following packages must also be
206 installed:
207
208 * `autoconf`
209 * `make`
210 * `zip`
211 * `unzip`
212
213 Often, you can install these packages using the following command line:
214 ```
215 <path to Cygwin setup>/setup-x86_64 -q -P autoconf -P make -P unzip -P zip
216 ```
217
218 Unfortunately, Cygwin can be unreliable in certain circumstances. If you
219 experience build tool crashes or strange issues when building on Windows,
220 please check the Cygwin FAQ on the ["BLODA" list](
221 https://cygwin.com/faq/faq.html#faq.using.bloda) and the section on [fork()
222 failures](https://cygwin.com/faq/faq.html#faq.using.fixing-fork-failures).
223
224 ### Solaris
225
226 See `make/devkit/solaris11.1-package-list.txt` for a list of recommended
227 packages to install when building on Solaris. The versions specified in this
228 list is the versions used by the daily builds at Oracle, and is likely to work
229 properly.
230
231 Older versions of Solaris shipped a broken version of `objcopy`. At least
232 version 2.21.1 is needed, which is provided by Solaris 11 Update 1. Objcopy is
233 needed if you want to have external debug symbols. Please make sure you are
234 using at least version 2.21.1 of objcopy, or that you disable external debug
235 symbols.
236
237 ### macOS
238
239 Apple is using a quite aggressive scheme of pushing OS updates, and coupling
240 these updates with required updates of Xcode. Unfortunately, this makes it
241 difficult for a project such as the JDK to keep pace with a continuously updated
242 machine running macOS. See the section on [Apple Xcode](#apple-xcode) on some
243 strategies to deal with this.
244
245 It is recommended that you use at least Mac OS X 10.13 (High Sierra). At the time
246 of writing, the JDK has been successfully compiled on macOS 10.12 (Sierra).
247
248 The standard macOS environment contains the basic tooling needed to build, but
249 for external libraries a package manager is recommended. The JDK uses
250 [homebrew](https://brew.sh/) in the examples, but feel free to use whatever
251 manager you want (or none).
252
253 ### Linux
254
255 It is often not much problem to build the JDK on Linux. The only general advice
256 is to try to use the compilers, external libraries and header files as provided
257 by your distribution.
258
259 The basic tooling is provided as part of the core operating system, but you
260 will most likely need to install developer packages.
261
262 For apt-based distributions (Debian, Ubuntu, etc), try this:
263 ```
264 sudo apt-get install build-essential
265 ```
266
267 For rpm-based distributions (Fedora, Red Hat, etc), try this:
268 ```
269 sudo yum groupinstall "Development Tools"
270 ```
271
272 ### AIX
273
274 The regular builds by SAP is using AIX version 7.1, but AIX 5.3 is also
275 supported. See the [OpenJDK PowerPC Port Status Page](
276 http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details.
277
278 ## Native Compiler (Toolchain) Requirements
279
280 Large portions of the JDK consists of native code, that needs to be compiled to
281 be able to run on the target platform. In theory, toolchain and operating
282 system should be independent factors, but in practice there's more or less a
283 one-to-one correlation between target operating system and toolchain.
284
285 Operating system Supported toolchain
286 ------------------ -------------------------
287 Linux gcc, clang
288 macOS Apple Xcode (using clang)
289 Solaris Oracle Solaris Studio
290 AIX IBM XL C/C++
291 Windows Microsoft Visual Studio
292
293 Please see the individual sections on the toolchains for version
294 recommendations. As a reference, these versions of the toolchains are used, at
295 the time of writing, by Oracle for the daily builds of the JDK. It should be
296 possible to compile the JDK with both older and newer versions, but the closer
297 you stay to this list, the more likely you are to compile successfully without
298 issues.
299
300 Operating system Toolchain version
301 ------------------ -------------------------------------------------------
302 Linux gcc 7.3.0
303 macOS Apple Xcode 9.4 (using clang 9.1.0)
304 Solaris Oracle Solaris Studio 12.4 (with compiler version 5.13)
305 Windows Microsoft Visual Studio 2017 update 15.5.5
306
307 ### gcc
308
309 The minimum accepted version of gcc is 4.8. Older versions will generate a warning
310 by `configure` and are unlikely to work.
311
312 The JDK is currently known to be able to compile with at least version 7.4 of
313 gcc.
314
315 In general, any version between these two should be usable.
316
317 ### clang
318
319 The minimum accepted version of clang is 3.2. Older versions will not be
320 accepted by `configure`.
321
322 To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`.
323
324 ### Apple Xcode
325
326 The oldest supported version of Xcode is 8.
327
328 You will need the Xcode command lines developers tools to be able to build
329 the JDK. (Actually, *only* the command lines tools are needed, not the IDE.)
330 The simplest way to install these is to run:
331 ```
332 xcode-select --install
333 ```
334
335 It is advisable to keep an older version of Xcode for building the JDK when
336 updating Xcode. This [blog page](
337 http://iosdevelopertips.com/xcode/install-multiple-versions-of-xcode.html) has
338 good suggestions on managing multiple Xcode versions. To use a specific version
339 of Xcode, use `xcode-select -s` before running `configure`, or use
340 `--with-toolchain-path` to point to the version of Xcode to use, e.g.
341 `configure --with-toolchain-path=/Applications/Xcode8.app/Contents/Developer/usr/bin`
342
343 If you have recently (inadvertently) updated your OS and/or Xcode version, and
344 the JDK can no longer be built, please see the section on [Problems with the
345 Build Environment](#problems-with-the-build-environment), and [Getting
346 Help](#getting-help) to find out if there are any recent, non-merged patches
347 available for this update.
348
349 ### Oracle Solaris Studio
350
351 The minimum accepted version of the Solaris Studio compilers is 5.13
352 (corresponding to Solaris Studio 12.4). Older versions will not be accepted by
353 configure.
354
355 The Solaris Studio installation should contain at least these packages:
356
357 Package Version
358 -------------------------------------------------- -------------
359 developer/solarisstudio-124/backend 12.4-1.0.6.0
360 developer/solarisstudio-124/c++ 12.4-1.0.10.0
361 developer/solarisstudio-124/cc 12.4-1.0.4.0
362 developer/solarisstudio-124/library/c++-libs 12.4-1.0.10.0
363 developer/solarisstudio-124/library/math-libs 12.4-1.0.0.1
364 developer/solarisstudio-124/library/studio-gccrt 12.4-1.0.0.1
365 developer/solarisstudio-124/studio-common 12.4-1.0.0.1
366 developer/solarisstudio-124/studio-ja 12.4-1.0.0.1
367 developer/solarisstudio-124/studio-legal 12.4-1.0.0.1
368 developer/solarisstudio-124/studio-zhCN 12.4-1.0.0.1
369
370 Compiling with Solaris Studio can sometimes be finicky. This is the exact
371 version used by Oracle, which worked correctly at the time of writing:
372 ```
373 $ cc -V
374 cc: Sun C 5.13 SunOS_i386 2014/10/20
375 $ CC -V
376 CC: Sun C++ 5.13 SunOS_i386 151846-10 2015/10/30
377 ```
378
379 ### Microsoft Visual Studio
380
381 The minimum accepted version of Visual Studio is 2010. Older versions will not
382 be accepted by `configure`. The maximum accepted version of Visual Studio is
383 2017. Versions older than 2017 are unlikely to continue working for long.
384
385 If you have multiple versions of Visual Studio installed, `configure` will by
386 default pick the latest. You can request a specific version to be used by
387 setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2015`.
388
389 If you get `LINK: fatal error LNK1123: failure during conversion to COFF: file
390 invalid` when building using Visual Studio 2010, you have encountered
391 [KB2757355](http://support.microsoft.com/kb/2757355), a bug triggered by a
392 specific installation order. However, the solution suggested by the KB article
393 does not always resolve the problem. See [this stackoverflow discussion](
394 https://stackoverflow.com/questions/10888391) for other suggestions.
395
396 ### IBM XL C/C++
397
398 The regular builds by SAP is using version 12.1, described as `IBM XL C/C++ for
399 AIX, V12.1 (5765-J02, 5725-C72) Version: 12.01.0000.0017`.
400
401 See the [OpenJDK PowerPC Port Status Page](
402 http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details.
403
404 ## Boot JDK Requirements
405
406 Paradoxically, building the JDK requires a pre-existing JDK. This is called the
407 "boot JDK". The boot JDK does not, however, have to be a JDK built directly from
408 the source code available in the OpenJDK Community. If you are porting the JDK
409 to a new platform, chances are that there already exists another JDK for that
410 platform that is usable as boot JDK.
411
412 The rule of thumb is that the boot JDK for building JDK major version *N*
413 should be a JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be
414 suitable as boot JDK. However, the JDK should be able to "build itself", so an
415 up-to-date build of the current JDK source is an acceptable alternative. If
416 you are following the *N-1* rule, make sure you've got the latest update
417 version, since JDK 8 GA might not be able to build JDK 9 on all platforms.
418
419 Early in the release cycle, version *N-1* may not yet have been released. In
420 that case, the preferred boot JDK will be version *N-2* until version *N-1*
421 is available.
422
423 If the boot JDK is not automatically detected, or the wrong JDK is picked, use
424 `--with-boot-jdk` to point to the JDK to use.
425
426 ### Getting JDK binaries
427
428 JDK binaries for Linux, Windows and macOS can be downloaded from
429 [jdk.java.net](http://jdk.java.net). An alternative is to download the
430 [Oracle JDK](http://www.oracle.com/technetwork/java/javase/downloads). Another
431 is the [Adopt OpenJDK Project](https://adoptopenjdk.net/), which publishes
432 experimental prebuilt binaries for various platforms.
433
434 On Linux you can also get a JDK from the Linux distribution. On apt-based
435 distros (like Debian and Ubuntu), `sudo apt-get install openjdk-<VERSION>-jdk`
436 is typically enough to install a JDK \<VERSION\>. On rpm-based distros (like
437 Fedora and Red Hat), try `sudo yum install java-<VERSION>-openjdk-devel`.
438
439 ## External Library Requirements
440
441 Different platforms require different external libraries. In general, libraries
442 are not optional - that is, they are either required or not used.
443
444 If a required library is not detected by `configure`, you need to provide the
445 path to it. There are two forms of the `configure` arguments to point to an
446 external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to
447 include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise,
448 but require the include files an library files to reside in a default hierarchy
449 under this directory. In most cases, it works fine.
450
451 As a fallback, the second version allows you to point to the include directory
452 and the lib directory separately.
453
454 ### FreeType
455
456 FreeType2 from [The FreeType Project](http://www.freetype.org/) is not required
457 on any platform. The exception is on Unix-based platforms when configuring such
458 that the build artifacts will reference a system installed library,
459 rather than bundling the JDK’s own copy.
460
461 * To install on an apt-based Linux, try running `sudo apt-get install
462 libfreetype6-dev`.
463 * To install on an rpm-based Linux, try running `sudo yum install
464 freetype-devel`.
465 * To install on Solaris, try running `pkg install system/library/freetype-2`.
466
467 Use `--with-freetype-include=<path>` and `--with-freetype-lib=<path>`
468 if `configure` does not automatically locate the platform FreeType files.
469
470 ### CUPS
471
472 CUPS, [Common UNIX Printing System](http://www.cups.org) header files are
473 required on all platforms, except Windows. Often these files are provided by
474 your operating system.
475
476 * To install on an apt-based Linux, try running `sudo apt-get install
477 libcups2-dev`.
478 * To install on an rpm-based Linux, try running `sudo yum install
479 cups-devel`.
480 * To install on Solaris, try running `pkg install print/cups`.
481
482 Use `--with-cups=<path>` if `configure` does not properly locate your CUPS
483 files.
484
485 ### X11
486
487 Certain [X11](http://www.x.org/) libraries and include files are required on
488 Linux and Solaris.
489
490 * To install on an apt-based Linux, try running `sudo apt-get install
491 libx11-dev libxext-dev libxrender-dev libxrandr-dev libxtst-dev libxt-dev`.
492 * To install on an rpm-based Linux, try running `sudo yum install
493 libXtst-devel libXt-devel libXrender-devel libXrandr-devel libXi-devel`.
494 * To install on Solaris, try running `pkg install x11/header/x11-protocols
495 x11/library/libice x11/library/libpthread-stubs x11/library/libsm
496 x11/library/libx11 x11/library/libxau x11/library/libxcb
497 x11/library/libxdmcp x11/library/libxevie x11/library/libxext
498 x11/library/libxrender x11/library/libxrandr x11/library/libxscrnsaver
499 x11/library/libxtst x11/library/toolkit/libxt`.
500
501 Use `--with-x=<path>` if `configure` does not properly locate your X11 files.
502
503 ### ALSA
504
505 ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is
506 required on Linux. At least version 0.9.1 of ALSA is required.
507
508 * To install on an apt-based Linux, try running `sudo apt-get install
509 libasound2-dev`.
510 * To install on an rpm-based Linux, try running `sudo yum install
511 alsa-lib-devel`.
512
513 Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA
514 files.
515
516 ### libffi
517
518 libffi, the [Portable Foreign Function Interface Library](
519 http://sourceware.org/libffi) is required when building the Zero version of
520 Hotspot.
521
522 * To install on an apt-based Linux, try running `sudo apt-get install
523 libffi-dev`.
524 * To install on an rpm-based Linux, try running `sudo yum install
525 libffi-devel`.
526
527 Use `--with-libffi=<path>` if `configure` does not properly locate your libffi
528 files.
529
530 ## Build Tools Requirements
531
532 ### Autoconf
533
534 The JDK requires [Autoconf](http://www.gnu.org/software/autoconf) on all
535 platforms. At least version 2.69 is required.
536
537 * To install on an apt-based Linux, try running `sudo apt-get install
538 autoconf`.
539 * To install on an rpm-based Linux, try running `sudo yum install
540 autoconf`.
541 * To install on macOS, try running `brew install autoconf`.
542 * To install on Windows, try running `<path to Cygwin setup>/setup-x86_64 -q
543 -P autoconf`.
544
545 If `configure` has problems locating your installation of autoconf, you can
546 specify it using the `AUTOCONF` environment variable, like this:
547
548 ```
549 AUTOCONF=<path to autoconf> configure ...
550 ```
551
552 ### GNU Make
553
554 The JDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors
555 of make are supported.
556
557 At least version 3.81 of GNU Make must be used. For distributions supporting
558 GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful
559 functionality to handle parallel building (supported by `--with-output-sync`)
560 and speed and stability improvements.
561
562 Note that `configure` locates and verifies a properly functioning version of
563 `make` and stores the path to this `make` binary in the configuration. If you
564 start a build using `make` on the command line, you will be using the version
565 of make found first in your `PATH`, and not necessarily the one stored in the
566 configuration. This initial make will be used as "bootstrap make", and in a
567 second stage, the make located by `configure` will be called. Normally, this
568 will present no issues, but if you have a very old `make`, or a non-GNU Make
569 `make` in your path, this might cause issues.
570
571 If you want to override the default make found by `configure`, use the `MAKE`
572 configure variable, e.g. `configure MAKE=/opt/gnu/make`.
573
574 On Solaris, it is common to call the GNU version of make by using `gmake`.
575
576 ### GNU Bash
577
578 The JDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells
579 are supported.
580
581 At least version 3.2 of GNU Bash must be used.
582
583 ## Running Configure
584
585 To build the JDK, you need a "configuration", which consists of a directory
586 where to store the build output, coupled with information about the platform,
587 the specific build machine, and choices that affect how the JDK is built.
588
589 The configuration is created by the `configure` script. The basic invocation of
590 the `configure` script looks like this:
591
592 ```
593 bash configure [options]
594 ```
595
596 This will create an output directory containing the configuration and setup an
597 area for the build result. This directory typically looks like
598 `build/linux-x64-normal-server-release`, but the actual name depends on your
599 specific configuration. (It can also be set directly, see [Using Multiple
600 Configurations](#using-multiple-configurations)). This directory is referred to
601 as `$BUILD` in this documentation.
602
603 `configure` will try to figure out what system you are running on and where all
604 necessary build components are. If you have all prerequisites for building
605 installed, it should find everything. If it fails to detect any component
606 automatically, it will exit and inform you about the problem.
607
608 Some command line examples:
609
610 * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`:
611 ```
612 bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32
613 ```
614
615 * Create a debug build with the `server` JVM and DTrace enabled:
616 ```
617 bash configure --enable-debug --with-jvm-variants=server --enable-dtrace
618 ```
619
620 ### Common Configure Arguments
621
622 Here follows some of the most common and important `configure` argument.
623
624 To get up-to-date information on *all* available `configure` argument, please
625 run:
626 ```
627 bash configure --help
628 ```
629
630 (Note that this help text also include general autoconf options, like
631 `--dvidir`, that is not relevant to the JDK. To list only JDK-specific
632 features, use `bash configure --help=short` instead.)
633
634 #### Configure Arguments for Tailoring the Build
635
636 * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand
637 for `--with-debug-level=fastdebug`)
638 * `--with-debug-level=<level>` - Set the debug level, which can be `release`,
639 `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized`
640 is variant of `release` with additional Hotspot debug code.
641 * `--with-native-debug-symbols=<method>` - Specify if and how native debug
642 symbols should be built. Available methods are `none`, `internal`,
643 `external`, `zipped`. Default behavior depends on platform. See [Native
644 Debug Symbols](#native-debug-symbols) for more details.
645 * `--with-version-string=<string>` - Specify the version string this build
646 will be identified with.
647 * `--with-version-<part>=<value>` - A group of options, where `<part>` can be
648 any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use
649 these options to modify just the corresponding part of the version string
650 from the default, or the value provided by `--with-version-string`.
651 * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant
652 (or variants) of Hotspot. Valid variants are: `server`, `client`,
653 `minimal`, `core`, `zero`, `custom`. Note that not all
654 variants are possible to combine in a single build.
655 * `--with-jvm-features=<feature>[,<feature>...]` - Use the specified JVM
656 features when building Hotspot. The list of features will be enabled on top
657 of the default list. For the `custom` JVM variant, this default list is
658 empty. A complete list of available JVM features can be found using `bash
659 configure --help`.
660 * `--with-target-bits=<bits>` - Create a target binary suitable for running
661 on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build
662 platform, instead of doing a full cross-compile. (This is known as a
663 *reduced* build.)
664
665 On Linux, BSD and AIX, it is possible to override where Java by default
666 searches for runtime/JNI libraries. This can be useful in situations where
667 there is a special shared directory for system JNI libraries. This setting
668 can in turn be overriden at runtime by setting the `java.library.path` property.
669
670 * `--with-jni-libpath=<path>` - Use the specified path as a default
671 when searching for runtime libraries.
672
673 #### Configure Arguments for Native Compilation
674
675 * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources
676 * `--with-sysroot=<path>` - Use this directory as sysroot
677 * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the
678 default path when searching for all kinds of binaries
679 * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when
680 searching for toolchain binaries (compilers etc)
681 * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C
682 files
683 * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++
684 files
685 * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK
686 libraries
687
688 #### Configure Arguments for External Dependencies
689
690 * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK](
691 #boot-jdk-requirements)
692 * `--with-freetype=<path>` - Set the path to [FreeType](#freetype)
693 * `--with-cups=<path>` - Set the path to [CUPS](#cups)
694 * `--with-x=<path>` - Set the path to [X11](#x11)
695 * `--with-alsa=<path>` - Set the path to [ALSA](#alsa)
696 * `--with-libffi=<path>` - Set the path to [libffi](#libffi)
697 * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests](
698 #running-tests)
699
700 Certain third-party libraries used by the JDK (libjpeg, giflib, libpng, lcms
701 and zlib) are included in the JDK repository. The default behavior of the
702 JDK build is to use this version of these libraries, but they might be
703 replaced by an external version. To do so, specify `system` as the `<source>`
704 option in these arguments. (The default is `bundled`).
705
706 * `--with-libjpeg=<source>` - Use the specified source for libjpeg
707 * `--with-giflib=<source>` - Use the specified source for giflib
708 * `--with-libpng=<source>` - Use the specified source for libpng
709 * `--with-lcms=<source>` - Use the specified source for lcms
710 * `--with-zlib=<source>` - Use the specified source for zlib
711
712 On Linux, it is possible to select either static or dynamic linking of the C++
713 runtime. The default is static linking, with dynamic linking as fallback if the
714 static library is not found.
715
716 * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic`
717 or `default`) for linking the C++ runtime.
718
719 ### Configure Control Variables
720
721 It is possible to control certain aspects of `configure` by overriding the
722 value of `configure` variables, either on the command line or in the
723 environment.
724
725 Normally, this is **not recommended**. If used improperly, it can lead to a
726 broken configuration. Unless you're well versed in the build system, this is
727 hard to use properly. Therefore, `configure` will print a warning if this is
728 detected.
729
730 However, there are a few `configure` variables, known as *control variables*
731 that are supposed to be overriden on the command line. These are variables that
732 describe the location of tools needed by the build, like `MAKE` or `GREP`. If
733 any such variable is specified, `configure` will use that value instead of
734 trying to autodetect the tool. For instance, `bash configure
735 MAKE=/opt/gnumake4.0/bin/make`.
736
737 If a configure argument exists, use that instead, e.g. use `--with-jtreg`
738 instead of setting `JTREGEXE`.
739
740 Also note that, despite what autoconf claims, setting `CFLAGS` will not
741 accomplish anything. Instead use `--with-extra-cflags` (and similar for
742 `cxxflags` and `ldflags`).
743
744 ## Running Make
745
746 When you have a proper configuration, all you need to do to build the JDK is to
747 run `make`. (But see the warning at [GNU Make](#gnu-make) about running the
748 correct version of make.)
749
750 When running `make` without any arguments, the default target is used, which is
751 the same as running `make default` or `make jdk`. This will build a minimal (or
752 roughly minimal) set of compiled output (known as an "exploded image") needed
753 for a developer to actually execute the newly built JDK. The idea is that in an
754 incremental development fashion, when doing a normal make, you should only
755 spend time recompiling what's changed (making it purely incremental) and only
756 do the work that's needed to actually run and test your code.
757
758 The output of the exploded image resides in `$BUILD/jdk`. You can test the
759 newly built JDK like this: `$BUILD/jdk/bin/java -version`.
760
761 ### Common Make Targets
762
763 Apart from the default target, here are some common make targets:
764
765 * `hotspot` - Build all of hotspot (but only hotspot)
766 * `hotspot-<variant>` - Build just the specified jvm variant
767 * `images` or `product-images` - Build the JDK image
768 * `docs` or `docs-image` - Build the documentation image
769 * `test-image` - Build the test image
770 * `all` or `all-images` - Build all images (product, docs and test)
771 * `bootcycle-images` - Build images twice, second time with newly built JDK
772 (good for testing)
773 * `clean` - Remove all files generated by make, but not those generated by
774 configure
775 * `dist-clean` - Remove all files, including configuration
776
777 Run `make help` to get an up-to-date list of important make targets and make
778 control variables.
779
780 It is possible to build just a single module, a single phase, or a single phase
781 of a single module, by creating make targets according to these followin
782 patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`,
783 `launchers`, `libs` or `rmic`. See [Using Fine-Grained Make Targets](
784 #using-fine-grained-make-targets) for more details about this functionality.
785
786 * `<phase>` - Build the specified phase and everything it depends on
787 * `<module>` - Build the specified module and everything it depends on
788 * `<module>-<phase>` - Compile the specified phase for the specified module
789 and everything it depends on
790
791 Similarly, it is possible to clean just a part of the build by creating make
792 targets according to these patterns:
793
794 * `clean-<outputdir>` - Remove the subdir in the output dir with the name
795 * `clean-<phase>` - Remove all build results related to a certain build
796 phase
797 * `clean-<module>` - Remove all build results related to a certain module
798 * `clean-<module>-<phase>` - Remove all build results related to a certain
799 module and phase
800
801 ### Make Control Variables
802
803 It is possible to control `make` behavior by overriding the value of `make`
804 variables, either on the command line or in the environment.
805
806 Normally, this is **not recommended**. If used improperly, it can lead to a
807 broken build. Unless you're well versed in the build system, this is hard to
808 use properly. Therefore, `make` will print a warning if this is detected.
809
810 However, there are a few `make` variables, known as *control variables* that
811 are supposed to be overriden on the command line. These make up the "make time"
812 configuration, as opposed to the "configure time" configuration.
813
814 #### General Make Control Variables
815
816 * `JOBS` - Specify the number of jobs to build with. See [Build
817 Performance](#build-performance).
818 * `LOG` - Specify the logging level and functionality. See [Checking the
819 Build Log File](#checking-the-build-log-file)
820 * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using
821 Multiple Configurations](#using-multiple-configurations)
822
823 #### Test Make Control Variables
824
825 These make control variables only make sense when running tests. Please see
826 [Testing the JDK](testing.html) for details.
827
828 * `TEST`
829 * `TEST_JOBS`
830 * `JTREG`
831 * `GTEST`
832
833 #### Advanced Make Control Variables
834
835 These advanced make control variables can be potentially unsafe. See [Hints and
836 Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and
837 [Understanding the Build System](#understanding-the-build-system) for details.
838
839 * `SPEC`
840 * `CONF_CHECK`
841 * `COMPARE_BUILD`
842 * `JDK_FILTER`
843
844 ## Running Tests
845
846 Most of the JDK tests are using the [JTReg](http://openjdk.java.net/jtreg)
847 test framework. Make sure that your configuration knows where to find your
848 installation of JTReg. If this is not picked up automatically, use the
849 `--with-jtreg=<path to jtreg home>` option to point to the JTReg framework.
850 Note that this option should point to the JTReg home, i.e. the top directory,
851 containing `lib/jtreg.jar` etc.
852
853 The [Adoption Group](https://wiki.openjdk.java.net/display/Adoption) provides
854 recent builds of jtreg [here](
855 https://adopt-openjdk.ci.cloudbees.com/job/jtreg/lastSuccessfulBuild/artifact).
856 Download the latest `.tar.gz` file, unpack it, and point `--with-jtreg` to the
857 `jtreg` directory that you just unpacked.
858
859 To execute the most basic tests (tier 1), use:
860 ```
861 make run-test-tier1
862 ```
863
864 For more details on how to run tests, please see the [Testing
865 the JDK](testing.html) document.
866
867 ## Cross-compiling
868
869 Cross-compiling means using one platform (the *build* platform) to generate
870 output that can ran on another platform (the *target* platform).
871
872 The typical reason for cross-compiling is that the build is performed on a more
873 powerful desktop computer, but the resulting binaries will be able to run on a
874 different, typically low-performing system. Most of the complications that
875 arise when building for embedded is due to this separation of *build* and
876 *target* systems.
877
878 This requires a more complex setup and build procedure. This section assumes
879 you are familiar with cross-compiling in general, and will only deal with the
880 particularities of cross-compiling the JDK. If you are new to cross-compiling,
881 please see the [external links at Wikipedia](
882 https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start
883 on reading materials.
884
885 Cross-compiling the JDK requires you to be able to build both for the build
886 platform and for the target platform. The reason for the former is that we need
887 to build and execute tools during the build process, both native tools and Java
888 tools.
889
890 If all you want to do is to compile a 32-bit version, for the same OS, on a
891 64-bit machine, consider using `--with-target-bits=32` instead of doing a
892 full-blown cross-compilation. (While this surely is possible, it's a lot more
893 work and will take much longer to build.)
894
895 ### Cross compiling the easy way with OpenJDK devkits
896
897 The OpenJDK build system provides out-of-the box support for creating and using
898 so called devkits. A `devkit` is basically a collection of a cross-compiling
899 toolchain and a sysroot environment which can easily be used together with the
900 `--with-devkit` configure option to cross compile the OpenJDK. On Linux/x86_64,
901 the following command:
902 ```
903 bash configure --with-devkit=<devkit-path> --openjdk-target=ppc64-linux-gnu && make
904 ```
905
906 will configure and build OpenJDK for Linux/ppc64 assuming that `<devkit-path>`
907 points to a Linux/x86_64 to Linux/ppc64 devkit.
908
909 Devkits can be created from the `make/devkit` directory by executing:
910 ```
911 make [ TARGETS="<TARGET_TRIPLET>+" ] [ BASE_OS=<OS> ] [ BASE_OS_VERSION=<VER> ]
912 ```
913
914 where `TARGETS` contains one or more `TARGET_TRIPLET`s of the form
915 described in [section 3.4 of the GNU Autobook](
916 https://sourceware.org/autobook/autobook/autobook_17.html). If no
917 targets are given, a native toolchain for the current platform will be
918 created. Currently, at least the following targets are known to work:
919
920 Supported devkit targets
921 -------------------------
922 x86_64-linux-gnu
923 aarch64-linux-gnu
924 arm-linux-gnueabihf
925 ppc64-linux-gnu
926 ppc64le-linux-gnu
927 s390x-linux-gnu
928
929 `BASE_OS` must be one of "OEL6" for Oracle Enterprise Linux 6 or
930 "Fedora" (if not specified "OEL6" will be the default). If the base OS
931 is "Fedora" the corresponding Fedora release can be specified with the
932 help of the `BASE_OS_VERSION` option (with "27" as default version).
933 If the build is successful, the new devkits can be found in the
934 `build/devkit/result` subdirectory:
935 ```
936 cd make/devkit
937 make TARGETS="ppc64le-linux-gnu aarch64-linux-gnu" BASE_OS=Fedora BASE_OS_VERSION=21
938 ls -1 ../../build/devkit/result/
939 x86_64-linux-gnu-to-aarch64-linux-gnu
940 x86_64-linux-gnu-to-ppc64le-linux-gnu
941 ```
942
943 Notice that devkits are not only useful for targeting different build
944 platforms. Because they contain the full build dependencies for a
945 system (i.e. compiler and root file system), they can easily be used
946 to build well-known, reliable and reproducible build environments. You
947 can for example create and use a devkit with GCC 7.3 and a Fedora 12
948 sysroot environment (with glibc 2.11) on Ubuntu 14.04 (which doesn't
949 have GCC 7.3 by default) to produce OpenJDK binaries which will run on
950 all Linux systems with runtime libraries newer than the ones from
951 Fedora 12 (e.g. Ubuntu 16.04, SLES 11 or RHEL 6).
952
953 ### Boot JDK and Build JDK
954
955 When cross-compiling, make sure you use a boot JDK that runs on the *build*
956 system, and not on the *target* system.
957
958 To be able to build, we need a "Build JDK", which is a JDK built from the
959 current sources (that is, the same as the end result of the entire build
960 process), but able to run on the *build* system, and not the *target* system.
961 (In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when
962 building JDK 9.)
963
964 The build process will create a minimal Build JDK for you, as part of building.
965 To speed up the build, you can use `--with-build-jdk` to `configure` to point
966 to a pre-built Build JDK. Please note that the build result is unpredictable,
967 and can possibly break in subtle ways, if the Build JDK does not **exactly**
968 match the current sources.
969
970 ### Specifying the Target Platform
971
972 You *must* specify the target platform when cross-compiling. Doing so will also
973 automatically turn the build into a cross-compiling mode. The simplest way to
974 do this is to use the `--openjdk-target` argument, e.g.
975 `--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`.
976 This will automatically set the `--build`, `--host` and `--target` options for
977 autoconf, which can otherwise be confusing. (In autoconf terminology, the
978 "target" is known as "host", and "target" is used for building a Canadian
979 cross-compiler.)
980
981 ### Toolchain Considerations
982
983 You will need two copies of your toolchain, one which generates output that can
984 run on the target system (the normal, or *target*, toolchain), and one that
985 generates output that can run on the build system (the *build* toolchain). Note
986 that cross-compiling is only supported for gcc at the time being. The gcc
987 standard is to prefix cross-compiling toolchains with the target denominator.
988 If you follow this standard, `configure` is likely to pick up the toolchain
989 correctly.
990
991 The *build* toolchain will be autodetected just the same way the normal
992 *build*/*target* toolchain will be autodetected when not cross-compiling. If
993 this is not what you want, or if the autodetection fails, you can specify a
994 devkit containing the *build* toolchain using `--with-build-devkit` to
995 `configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments.
996
997 It is often helpful to locate the cross-compilation tools, headers and
998 libraries in a separate directory, outside the normal path, and point out that
999 directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and
1000 appending the directory when searching for cross-compilations tools
1001 (`--with-toolchain-path`). As a compact form, you can also use `--with-devkit`
1002 to point to a single directory, if it is correctly setup. (See `basics.m4` for
1003 details.)
1004
1005 If you are unsure what toolchain and versions to use, these have been proved
1006 working at the time of writing:
1007
1008 * [aarch64](
1009 https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-linux-gnu-4.8-2013.11_linux.tar.xz)
1010 * [arm 32-bit hardware floating point](
1011 https://launchpad.net/linaro-toolchain-unsupported/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux.tar.bz2)
1012
1013 ### Native Libraries
1014
1015 You will need copies of external native libraries for the *target* system,
1016 present on the *build* machine while building.
1017
1018 Take care not to replace the *build* system's version of these libraries by
1019 mistake, since that can render the *build* machine unusable.
1020
1021 Make sure that the libraries you point to (ALSA, X11, etc) are for the
1022 *target*, not the *build*, platform.
1023
1024 #### ALSA
1025
1026 You will need alsa libraries suitable for your *target* system. For most cases,
1027 using Debian's pre-built libraries work fine.
1028
1029 Note that alsa is needed even if you only want to build a headless JDK.
1030
1031 * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and
1032 search for the `libasound2` and `libasound2-dev` packages for your *target*
1033 system. Download them to /tmp.
1034
1035 * Install the libraries into the cross-compilation toolchain. For instance:
1036 ```
1037 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc
1038 dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb .
1039 dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb .
1040 ```
1041
1042 * If alsa is not properly detected by `configure`, you can point it out by
1043 `--with-alsa`.
1044
1045 #### X11
1046
1047 You will need X11 libraries suitable for your *target* system. For most cases,
1048 using Debian's pre-built libraries work fine.
1049
1050 Note that X11 is needed even if you only want to build a headless JDK.
1051
1052 * Go to [Debian Package Search](https://www.debian.org/distrib/packages),
1053 search for the following packages for your *target* system, and download them
1054 to /tmp/target-x11:
1055 * libxi
1056 * libxi-dev
1057 * x11proto-core-dev
1058 * x11proto-input-dev
1059 * x11proto-kb-dev
1060 * x11proto-render-dev
1061 * x11proto-xext-dev
1062 * libice-dev
1063 * libxrender
1064 * libxrender-dev
1065 * libxrandr-dev
1066 * libsm-dev
1067 * libxt-dev
1068 * libx11
1069 * libx11-dev
1070 * libxtst
1071 * libxtst-dev
1072 * libxext
1073 * libxext-dev
1074
1075 * Install the libraries into the cross-compilation toolchain. For instance:
1076 ```
1077 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr
1078 mkdir X11R6
1079 cd X11R6
1080 for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done
1081 mv usr/* .
1082 cd lib
1083 cp arm-linux-gnueabihf/* .
1084 ```
1085
1086 You can ignore the following messages. These libraries are not needed to
1087 successfully complete a full JDK build.
1088 ```
1089 cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory
1090 cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory
1091 cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory
1092 ```
1093
1094 * If the X11 libraries are not properly detected by `configure`, you can
1095 point them out by `--with-x`.
1096
1097 ### Creating And Using Sysroots With qemu-deboostrap
1098
1099 Fortunately, you can create sysroots for foreign architectures with tools
1100 provided by your OS. On Debian/Ubuntu systems, one could use `qemu-deboostrap` to
1101 create the *target* system chroot, which would have the native libraries and headers
1102 specific to that *target* system. After that, we can use the cross-compiler on the *build*
1103 system, pointing into chroot to get the build dependencies right. This allows building
1104 for foreign architectures with native compilation speed.
1105
1106 For example, cross-compiling to AArch64 from x86_64 could be done like this:
1107
1108 * Install cross-compiler on the *build* system:
1109 ```
1110 apt install g++-aarch64-linux-gnu gcc-aarch64-linux-gnu
1111 ```
1112
1113 * Create chroot on the *build* system, configuring it for *target* system:
1114 ```
1115 sudo qemu-debootstrap --arch=arm64 --verbose \
1116 --include=fakeroot,build-essential,libx11-dev,libxext-dev,libxrender-dev,libxrandr-dev,libxtst-dev,libxt-dev,libcups2-dev,libfontconfig1-dev,libasound2-dev,libfreetype6-dev,libpng12-dev \
1117 --resolve-deps jessie /chroots/arm64 http://httpredir.debian.org/debian/
1118 ```
1119
1120 * Configure and build with newly created chroot as sysroot/toolchain-path:
1121 ```
1122 CC=aarch64-linux-gnu-gcc CXX=aarch64-linux-gnu-g++ sh ./configure --openjdk-target=aarch64-linux-gnu --with-sysroot=/chroots/arm64/ --with-toolchain-path=/chroots/arm64/
1123 make images
1124 ls build/linux-aarch64-normal-server-release/
1125 ```
1126
1127 The build does not create new files in that chroot, so it can be reused for multiple builds
1128 without additional cleanup.
1129
1130 Architectures that are known to successfully cross-compile like this are:
1131
1132 Target `CC` `CXX` `--arch=...` `--openjdk-target=...`
1133 ------------ ------------------------- --------------------------- ------------- -----------------------
1134 x86 default default i386 i386-linux-gnu
1135 armhf gcc-arm-linux-gnueabihf g++-arm-linux-gnueabihf armhf arm-linux-gnueabihf
1136 aarch64 gcc-aarch64-linux-gnu g++-aarch64-linux-gnu arm64 aarch64-linux-gnu
1137 ppc64el gcc-powerpc64le-linux-gnu g++-powerpc64le-linux-gnu ppc64el powerpc64le-linux-gnu
1138 s390x gcc-s390x-linux-gnu g++-s390x-linux-gnu s390x s390x-linux-gnu
1139
1140 Additional architectures might be supported by Debian/Ubuntu Ports.
1141
1142 ### Building for ARM/aarch64
1143
1144 A common cross-compilation target is the ARM CPU. When building for ARM, it is
1145 useful to set the ABI profile. A number of pre-defined ABI profiles are
1146 available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt,
1147 armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer
1148 properly supported by the JDK.
1149
1150 ### Verifying the Build
1151
1152 The build will end up in a directory named like
1153 `build/linux-arm-normal-server-release`.
1154
1155 Inside this build output directory, the `images/jdk` will contain the newly
1156 built JDK, for your *target* system.
1157
1158 Copy these folders to your *target* system. Then you can run e.g.
1159 `images/jdk/bin/java -version`.
1160
1161 ## Build Performance
1162
1163 Building the JDK requires a lot of horsepower. Some of the build tools can be
1164 adjusted to utilize more or less of resources such as parallel threads and
1165 memory. The `configure` script analyzes your system and selects reasonable
1166 values for such options based on your hardware. If you encounter resource
1167 problems, such as out of memory conditions, you can modify the detected values
1168 with:
1169
1170 * `--with-num-cores` -- number of cores in the build system, e.g.
1171 `--with-num-cores=8`.
1172
1173 * `--with-memory-size` -- memory (in MB) available in the build system, e.g.
1174 `--with-memory-size=1024`
1175
1176 You can also specify directly the number of build jobs to use with
1177 `--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag
1178 to `make`. In most cases it will be ignored by the makefiles, but it can cause
1179 problems for some make targets.
1180
1181 It might also be necessary to specify the JVM arguments passed to the Boot JDK,
1182 using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the
1183 default JVM arguments passed to the Boot JDK.
1184
1185 At the end of a successful execution of `configure`, you will get a performance
1186 summary, indicating how well the build will perform. Here you will also get
1187 performance hints. If you want to build fast, pay attention to those!
1188
1189 If you want to tweak build performance, run with `make LOG=info` to get a build
1190 time summary at the end of the build process.
1191
1192 ### Disk Speed
1193
1194 If you are using network shares, e.g. via NFS, for your source code, make sure
1195 the build directory is situated on local disk (e.g. by `ln -s
1196 /localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely
1197 high for building on a network share; close to unusable.
1198
1199 Also, make sure that your build tools (including Boot JDK and toolchain) is
1200 located on a local disk and not a network share.
1201
1202 As has been stressed elsewhere, do use SSD for source code and build directory,
1203 as well as (if possible) the build tools.
1204
1205 ### Virus Checking
1206
1207 The use of virus checking software, especially on Windows, can *significantly*
1208 slow down building of the JDK. If possible, turn off such software, or exclude
1209 the directory containing the JDK source code from on-the-fly checking.
1210
1211 ### Ccache
1212
1213 The JDK build supports building with ccache when using gcc or clang. Using
1214 ccache can radically speed up compilation of native code if you often rebuild
1215 the same sources. Your milage may vary however, so we recommend evaluating it
1216 for yourself. To enable it, make sure it's on the path and configure with
1217 `--enable-ccache`.
1218
1219 ### Precompiled Headers
1220
1221 By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains
1222 were it is properly supported (clang, gcc, and Visual Studio). Normally, this
1223 speeds up the build process, but in some circumstances, it can actually slow
1224 things down.
1225
1226 You can experiment by disabling precompiled headers using
1227 `--disable-precompiled-headers`.
1228
1229 ### Icecc / icecream
1230
1231 [icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a
1232 distributed compiler network. If you have multiple machines available for
1233 building the JDK, you can drastically cut individual build times by utilizing
1234 it.
1235
1236 To use, setup an icecc network, and install icecc on the build machine. Then
1237 run `configure` using `--enable-icecc`.
1238
1239 ### Using sjavac
1240
1241 To speed up Java compilation, especially incremental compilations, you can try
1242 the experimental sjavac compiler by using `--enable-sjavac`.
1243
1244 ### Building the Right Target
1245
1246 Selecting the proper target to build can have dramatic impact on build time.
1247 For normal usage, `jdk` or the default target is just fine. You only need to
1248 build `images` for shipping, or if your tests require it.
1249
1250 See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on
1251 how to build an even smaller subset of the product.
1252
1253 ## Troubleshooting
1254
1255 If your build fails, it can sometimes be difficult to pinpoint the problem or
1256 find a proper solution.
1257
1258 ### Locating the Source of the Error
1259
1260 When a build fails, it can be hard to pinpoint the actual cause of the error.
1261 In a typical build process, different parts of the product build in parallel,
1262 with the output interlaced.
1263
1264 #### Build Failure Summary
1265
1266 To help you, the build system will print a failure summary at the end. It looks
1267 like this:
1268
1269 ```
1270 ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2)
1271
1272 === Output from failing command(s) repeated here ===
1273 * For target hotspot_variant-server_libjvm_objs_psMemoryPool.o:
1274 /localhome/hg/jdk9-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type
1275 ... (rest of output omitted)
1276
1277 * All command lines available in /localhome/hg/jdk9-sandbox/build/linux-x64/make-support/failure-logs.
1278 === End of repeated output ===
1279
1280 === Make failed targets repeated here ===
1281 lib/CompileJvm.gmk:207: recipe for target '/localhome/hg/jdk9-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed
1282 make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed
1283 === End of repeated output ===
1284
1285 Hint: Try searching the build log for the name of the first failed target.
1286 Hint: If caused by a warning, try configure --disable-warnings-as-errors.
1287 ```
1288
1289 Let's break it down! First, the selected configuration, and the top-level
1290 target you entered on the command line that caused the failure is printed.
1291
1292 Then, between the `Output from failing command(s) repeated here` and `End of
1293 repeated output` the first lines of output (stdout and stderr) from the actual
1294 failing command is repeated. In most cases, this is the error message that
1295 caused the build to fail. If multiple commands were failing (this can happen in
1296 a parallel build), output from all failed commands will be printed here.
1297
1298 The path to the `failure-logs` directory is printed. In this file you will find
1299 a `<target>.log` file that contains the output from this command in its
1300 entirety, and also a `<target>.cmd`, which contain the complete command line
1301 used for running this command. You can re-run the failing command by executing
1302 `. <path to failure-logs>/<target>.cmd` in your shell.
1303
1304 Another way to trace the failure is to follow the chain of make targets, from
1305 top-level targets to individual file targets. Between `Make failed targets
1306 repeated here` and `End of repeated output` the output from make showing this
1307 chain is repeated. The first failed recipe will typically contain the full path
1308 to the file in question that failed to compile. Following lines will show a
1309 trace of make targets why we ended up trying to compile that file.
1310
1311 Finally, some hints are given on how to locate the error in the complete log.
1312 In this example, we would try searching the log file for "`psMemoryPool.o`".
1313 Another way to quickly locate make errors in the log is to search for "`]
1314 Error`" or "`***`".
1315
1316 Note that the build failure summary will only help you if the issue was a
1317 compilation failure or similar. If the problem is more esoteric, or is due to
1318 errors in the build machinery, you will likely get empty output logs, and `No
1319 indication of failed target found` instead of the make target chain.
1320
1321 #### Checking the Build Log File
1322
1323 The output (stdout and stderr) from the latest build is always stored in
1324 `$BUILD/build.log`. The previous build log is stored as `build.log.old`. This
1325 means that it is not necessary to redirect the build output yourself if you
1326 want to process it.
1327
1328 You can increase the verbosity of the log file, by the `LOG` control variable
1329 to `make`. If you want to see the command lines used in compilations, use
1330 `LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug`
1331 or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g.
1332 `LOG=info,cmdlines`. The `debug` log level will show most shell commands
1333 executed by make, and `trace` will show all. Beware that both these log levels
1334 will produce a massive build log!
1335
1336 ### Fixing Unexpected Build Failures
1337
1338 Most of the time, the build will fail due to incorrect changes in the source
1339 code.
1340
1341 Sometimes the build can fail with no apparent changes that have caused the
1342 failure. If this is the first time you are building the JDK on this particular
1343 computer, and the build fails, the problem is likely with your build
1344 environment. But even if you have previously built the JDK with success, and it
1345 now fails, your build environment might have changed (perhaps due to OS
1346 upgrades or similar). But most likely, such failures are due to problems with
1347 the incremental rebuild.
1348
1349 #### Problems with the Build Environment
1350
1351 Make sure your configuration is correct. Re-run `configure`, and look for any
1352 warnings. Warnings that appear in the middle of the `configure` output is also
1353 repeated at the end, after the summary. The entire log is stored in
1354 `$BUILD/configure.log`.
1355
1356 Verify that the summary at the end looks correct. Are you indeed using the Boot
1357 JDK and native toolchain that you expect?
1358
1359 By default, the JDK has a strict approach where warnings from the compiler is
1360 considered errors which fail the build. For very new or very old compiler
1361 versions, this can trigger new classes of warnings, which thus fails the build.
1362 Run `configure` with `--disable-warnings-as-errors` to turn of this behavior.
1363 (The warnings will still show, but not make the build fail.)
1364
1365 #### Problems with Incremental Rebuilds
1366
1367 Incremental rebuilds mean that when you modify part of the product, only the
1368 affected parts get rebuilt. While this works great in most cases, and
1369 significantly speed up the development process, from time to time complex
1370 interdependencies will result in an incorrect build result. This is the most
1371 common cause for unexpected build problems.
1372
1373 Here are a suggested list of things to try if you are having unexpected build
1374 problems. Each step requires more time than the one before, so try them in
1375 order. Most issues will be solved at step 1 or 2.
1376
1377 1. Make sure your repository is up-to-date
1378
1379 Run `hg pull -u` to make sure you have the latest changes.
1380
1381 2. Clean build results
1382
1383 The simplest way to fix incremental rebuild issues is to run `make clean`.
1384 This will remove all build results, but not the configuration or any build
1385 system support artifacts. In most cases, this will solve build errors
1386 resulting from incremental build mismatches.
1387
1388 3. Completely clean the build directory.
1389
1390 If this does not work, the next step is to run `make dist-clean`, or
1391 removing the build output directory (`$BUILD`). This will clean all
1392 generated output, including your configuration. You will need to re-run
1393 `configure` after this step. A good idea is to run `make
1394 print-configuration` before running `make dist-clean`, as this will print
1395 your current `configure` command line. Here's a way to do this:
1396
1397 ```
1398 make print-configuration > current-configuration
1399 make dist-clean
1400 bash configure $(cat current-configuration)
1401 make
1402 ```
1403
1404 4. Re-clone the Mercurial repository
1405
1406 Sometimes the Mercurial repository gets in a state that causes the product
1407 to be un-buildable. In such a case, the simplest solution is often the
1408 "sledgehammer approach": delete the entire repository, and re-clone it.
1409 If you have local changes, save them first to a different location using
1410 `hg export`.
1411
1412 ### Specific Build Issues
1413
1414 #### Clock Skew
1415
1416 If you get an error message like this:
1417 ```
1418 File 'xxx' has modification time in the future.
1419 Clock skew detected. Your build may be incomplete.
1420 ```
1421 then the clock on your build machine is out of sync with the timestamps on the
1422 source files. Other errors, apparently unrelated but in fact caused by the
1423 clock skew, can occur along with the clock skew warnings. These secondary
1424 errors may tend to obscure the fact that the true root cause of the problem is
1425 an out-of-sync clock.
1426
1427 If you see these warnings, reset the clock on the build machine, run `make
1428 clean` and restart the build.
1429
1430 #### Out of Memory Errors
1431
1432 On Solaris, you might get an error message like this:
1433 ```
1434 Trouble writing out table to disk
1435 ```
1436 To solve this, increase the amount of swap space on your build machine.
1437
1438 On Windows, you might get error messages like this:
1439 ```
1440 fatal error - couldn't allocate heap
1441 cannot create ... Permission denied
1442 spawn failed
1443 ```
1444 This can be a sign of a Cygwin problem. See the information about solving
1445 problems in the [Cygwin](#cygwin) section. Rebooting the computer might help
1446 temporarily.
1447
1448 ### Getting Help
1449
1450 If none of the suggestions in this document helps you, or if you find what you
1451 believe is a bug in the build system, please contact the Build Group by sending
1452 a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net).
1453 Please include the relevant parts of the configure and/or build log.
1454
1455 If you need general help or advice about developing for the JDK, you can also
1456 contact the Adoption Group. See the section on [Contributing to OpenJDK](
1457 #contributing-to-openjdk) for more information.
1458
1459 ## Hints and Suggestions for Advanced Users
1460
1461 ### Setting Up a Repository for Pushing Changes (defpath)
1462
1463 To help you prepare a proper push path for a Mercurial repository, there exists
1464 a useful tool known as [defpath](
1465 http://openjdk.java.net/projects/code-tools/defpath). It will help you setup a
1466 proper push path for pushing changes to the JDK.
1467
1468 Install the extension by cloning
1469 `http://hg.openjdk.java.net/code-tools/defpath` and updating your `.hgrc` file.
1470 Here's one way to do this:
1471
1472 ```
1473 cd ~
1474 mkdir hg-ext
1475 cd hg-ext
1476 hg clone http://hg.openjdk.java.net/code-tools/defpath
1477 cat << EOT >> ~/.hgrc
1478 [extensions]
1479 defpath=~/hg-ext/defpath/defpath.py
1480 EOT
1481 ```
1482
1483 You can now setup a proper push path using:
1484 ```
1485 hg defpath -d -u <your OpenJDK username>
1486 ```
1487
1488 ### Bash Completion
1489
1490 The `configure` and `make` commands tries to play nice with bash command-line
1491 completion (using `<tab>` or `<tab><tab>`). To use this functionality, make
1492 sure you enable completion in your `~/.bashrc` (see instructions for bash in
1493 your operating system).
1494
1495 Make completion will work out of the box, and will complete valid make targets.
1496 For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`.
1497
1498 The `configure` script can get completion for options, but for this to work you
1499 need to help `bash` on the way. The standard way of running the script, `bash
1500 configure`, will not be understood by bash completion. You need `configure` to
1501 be the command to run. One way to achieve this is to add a simple helper script
1502 to your path:
1503
1504 ```
1505 cat << EOT > /tmp/configure
1506 #!/bin/bash
1507 if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then
1508 echo >&2 "Abort: Trying to call configure helper recursively"
1509 exit 1
1510 fi
1511
1512 bash \$PWD/configure "\$@"
1513 EOT
1514 chmod +x /tmp/configure
1515 sudo mv /tmp/configure /usr/local/bin
1516 ```
1517
1518 Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`.
1519
1520 ### Using Multiple Configurations
1521
1522 You can have multiple configurations for a single source repository. When you
1523 create a new configuration, run `configure --with-conf-name=<name>` to create a
1524 configuration with the name `<name>`. Alternatively, you can create a directory
1525 under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd
1526 build/<name> && bash ../../configure`.
1527
1528 Then you can build that configuration using `make CONF_NAME=<name>` or `make
1529 CONF=<pattern>`, where `<pattern>` is a substring matching one or several
1530 configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will
1531 match *all* available configuration, so `make CONF= hotspot` will build the
1532 `hotspot` target for all configurations. Alternatively, you can execute `make`
1533 in the configuration directory, e.g. `cd build/<name> && make`.
1534
1535 ### Handling Reconfigurations
1536
1537 If you update the repository and part of the configure script has changed, the
1538 build system will force you to re-run `configure`.
1539
1540 Most of the time, you will be fine by running `configure` again with the same
1541 arguments as the last time, which can easily be performed by `make
1542 reconfigure`. To simplify this, you can use the `CONF_CHECK` make control
1543 variable, either as `make CONF_CHECK=auto`, or by setting an environment
1544 variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc`
1545 file, `make` will always run `reconfigure` automatically whenever the configure
1546 script has changed.
1547
1548 You can also use `CONF_CHECK=ignore` to skip the check for a needed configure
1549 update. This might speed up the build, but comes at the risk of an incorrect
1550 build result. This is only recommended if you know what you're doing.
1551
1552 From time to time, you will also need to modify the command line to `configure`
1553 due to changes. Use `make print-configure` to show the command line used for
1554 your current configuration.
1555
1556 ### Using Fine-Grained Make Targets
1557
1558 The default behavior for make is to create consistent and correct output, at
1559 the expense of build speed, if necessary.
1560
1561 If you are prepared to take some risk of an incorrect build, and know enough of
1562 the system to understand how things build and interact, you can speed up the
1563 build process considerably by instructing make to only build a portion of the
1564 product.
1565
1566 #### Building Individual Modules
1567
1568 The safe way to use fine-grained make targets is to use the module specific
1569 make targets. All source code in the JDK is organized so it belongs to a
1570 module, e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific
1571 module, by giving it as make target: `make jdk.jdwp.agent`. If the specified
1572 module depends on other modules (e.g. `java.base`), those modules will be built
1573 first.
1574
1575 You can also specify a set of modules, just as you can always specify a set of
1576 make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi
1577 jdk.crypto.ucrypto`
1578
1579 #### Building Individual Module Phases
1580
1581 The build process for each module is divided into separate phases. Not all
1582 modules need all phases. Which are needed depends on what kind of source code
1583 and other artifact the module consists of. The phases are:
1584
1585 * `gensrc` (Generate source code to compile)
1586 * `gendata` (Generate non-source code artifacts)
1587 * `copy` (Copy resource artifacts)
1588 * `java` (Compile Java code)
1589 * `launchers` (Compile native executables)
1590 * `libs` (Compile native libraries)
1591 * `rmic` (Run the `rmic` tool)
1592
1593 You can build only a single phase for a module by using the notation
1594 `$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`,
1595 use `make java.base-gensrc`.
1596
1597 Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if
1598 present). Make will build all needed prerequisites before building the
1599 requested phase.
1600
1601 #### Skipping the Dependency Check
1602
1603 When using an iterative development style with frequent quick rebuilds, the
1604 dependency check made by make can take up a significant portion of the time
1605 spent on the rebuild. In such cases, it can be useful to bypass the dependency
1606 check in make.
1607
1608 > **Note that if used incorrectly, this can lead to a broken build!**
1609
1610 To achieve this, append `-only` to the build target. For instance, `make
1611 jdk.jdwp.agent-java-only` will *only* build the `java` phase of the
1612 `jdk.jdwp.agent` module. If the required dependencies are not present, the
1613 build can fail. On the other hand, the execution time measures in milliseconds.
1614
1615 A useful pattern is to build the first time normally (e.g. `make
1616 jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target.
1617
1618 #### Rebuilding Part of java.base (JDK\_FILTER)
1619
1620 If you are modifying files in `java.base`, which is the by far largest module
1621 in the JDK, then you need to rebuild all those files whenever a single file has
1622 changed. (This inefficiency will hopefully be addressed in JDK 10.)
1623
1624 As a hack, you can use the make control variable `JDK_FILTER` to specify a
1625 pattern that will be used to limit the set of files being recompiled. For
1626 instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods,
1627 `make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation
1628 to files in the `javax.crypto` package.
1629
1630 ### Learn About Mercurial
1631
1632 To become an efficient JDK developer, it is recommended that you invest in
1633 learning Mercurial properly. Here are some links that can get you started:
1634
1635 * [Mercurial for git users](http://www.mercurial-scm.org/wiki/GitConcepts)
1636 * [The official Mercurial tutorial](http://www.mercurial-scm.org/wiki/Tutorial)
1637 * [hg init](http://hginit.com/)
1638 * [Mercurial: The Definitive Guide](http://hgbook.red-bean.com/read/)
1639
1640 ## Understanding the Build System
1641
1642 This section will give you a more technical description on the details of the
1643 build system.
1644
1645 ### Configurations
1646
1647 The build system expects to find one or more configuration. These are
1648 technically defined by the `spec.gmk` in a subdirectory to the `build`
1649 subdirectory. The `spec.gmk` file is generated by `configure`, and contains in
1650 principle the configuration (directly or by files included by `spec.gmk`).
1651
1652 You can, in fact, select a configuration to build by pointing to the `spec.gmk`
1653 file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`.
1654 While this is not the recommended way to call `make` as a user, it is what is
1655 used under the hood by the build system.
1656
1657 ### Build Output Structure
1658
1659 The build output for a configuration will end up in `build/<configuration
1660 name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory
1661 contains the following important directories:
1662
1663 ```
1664 buildtools/
1665 configure-support/
1666 hotspot/
1667 images/
1668 jdk/
1669 make-support/
1670 support/
1671 test-results/
1672 test-support/
1673 ```
1674
1675 This is what they are used for:
1676
1677 * `images`: This is the directory were the output of the `*-image` make
1678 targets end up. For instance, `make jdk-image` ends up in `images/jdk`.
1679
1680 * `jdk`: This is the "exploded image". After `make jdk`, you will be able to
1681 launch the newly built JDK by running `$BUILD/jdk/bin/java`.
1682
1683 * `test-results`: This directory contains the results from running tests.
1684
1685 * `support`: This is an area for intermediate files needed during the build,
1686 e.g. generated source code, object files and class files. Some noteworthy
1687 directories in `support` is `gensrc`, which contains the generated source
1688 code, and the `modules_*` directories, which contains the files in a
1689 per-module hierarchy that will later be collapsed into the `jdk` directory
1690 of the exploded image.
1691
1692 * `buildtools`: This is an area for tools compiled for the build platform
1693 that are used during the rest of the build.
1694
1695 * `hotspot`: This is an area for intermediate files needed when building
1696 hotspot.
1697
1698 * `configure-support`, `make-support` and `test-support`: These directories
1699 contain files that are needed by the build system for `configure`, `make`
1700 and for running tests.
1701
1702 ### Fixpath
1703
1704 Windows path typically look like `C:\User\foo`, while Unix paths look like
1705 `/home/foo`. Tools with roots from Unix often experience issues related to this
1706 mismatch when running on Windows.
1707
1708 In the JDK build, we always use Unix paths internally, and only just before
1709 calling a tool that does not understand Unix paths do we convert them to
1710 Windows paths.
1711
1712 This conversion is done by the `fixpath` tool, which is a small wrapper that
1713 modifies unix-style paths to Windows-style paths in command lines. Fixpath is
1714 compiled automatically by `configure`.
1715
1716 ### Native Debug Symbols
1717
1718 Native libraries and executables can have debug symbol (and other debug
1719 information) associated with them. How this works is very much platform
1720 dependent, but a common problem is that debug symbol information takes a lot of
1721 disk space, but is rarely needed by the end user.
1722
1723 The JDK supports different methods on how to handle debug symbols. The
1724 method used is selected by `--with-native-debug-symbols`, and available methods
1725 are `none`, `internal`, `external`, `zipped`.
1726
1727 * `none` means that no debug symbols will be generated during the build.
1728
1729 * `internal` means that debug symbols will be generated during the build, and
1730 they will be stored in the generated binary.
1731
1732 * `external` means that debug symbols will be generated during the build, and
1733 after the compilation, they will be moved into a separate `.debuginfo` file.
1734 (This was previously known as FDS, Full Debug Symbols).
1735
1736 * `zipped` is like `external`, but the .debuginfo file will also be zipped
1737 into a `.diz` file.
1738
1739 When building for distribution, `zipped` is a good solution. Binaries built
1740 with `internal` is suitable for use by developers, since they facilitate
1741 debugging, but should be stripped before distributed to end users.
1742
1743 ### Autoconf Details
1744
1745 The `configure` script is based on the autoconf framework, but in some details
1746 deviate from a normal autoconf `configure` script.
1747
1748 The `configure` script in the top level directory of the JDK is just a thin
1749 wrapper that calls `make/autoconf/configure`. This in turn will run `autoconf`
1750 to create the runnable (generated) configure script, as
1751 `.build/generated-configure.sh`. Apart from being responsible for the
1752 generation of the runnable script, the `configure` script also provides
1753 functionality that is not easily expressed in the normal Autoconf framework. As
1754 part of this functionality, the generated script is called.
1755
1756 The build system will detect if the Autoconf source files have changed, and
1757 will trigger a regeneration of the generated script if needed. You can also
1758 manually request such an update by `bash configure autogen`.
1759
1760 In previous versions of the JDK, the generated script was checked in at
1761 `make/autoconf/generated-configure.sh`. This is no longer the case.
1762
1763 ### Developing the Build System Itself
1764
1765 This section contains a few remarks about how to develop for the build system
1766 itself. It is not relevant if you are only making changes in the product source
1767 code.
1768
1769 While technically using `make`, the make source files of the JDK does not
1770 resemble most other Makefiles. Instead of listing specific targets and actions
1771 (perhaps using patterns), the basic modus operandi is to call a high-level
1772 function (or properly, macro) from the API in `make/common`. For instance, to
1773 compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module,
1774 a call like this would be made:
1775
1776 ```
1777 $(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \
1778 SETUP := GENERATE_OLDBYTECODE, \
1779 SRC := $(TOPDIR)/src/jkd.foo/share/classes, \
1780 INCLUDES := jdk/internal/foo, \
1781 BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \
1782 ))
1783 ```
1784
1785 By encapsulating and expressing the high-level knowledge of *what* should be
1786 done, rather than *how* it should be done (as is normal in Makefiles), we can
1787 build a much more powerful and flexible build system.
1788
1789 Correct dependency tracking is paramount. Sloppy dependency tracking will lead
1790 to improper parallelization, or worse, race conditions.
1791
1792 To test for/debug race conditions, try running `make JOBS=1` and `make
1793 JOBS=100` and see if it makes any difference. (It shouldn't).
1794
1795 To compare the output of two different builds and see if, and how, they differ,
1796 run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two
1797 builds you want to compare.
1798
1799 To automatically build two consecutive versions and compare them, use
1800 `COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value
1801 assignments, like this:
1802 ```
1803 make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot
1804 ```
1805 See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`.
1806
1807 To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`.
1808 Use `JOBS=1` to avoid parallelism.
1809
1810 Please check that you adhere to the [Code Conventions for the Build System](
1811 http://openjdk.java.net/groups/build/doc/code-conventions.html) before
1812 submitting patches.
1813
1814 ## Contributing to the JDK
1815
1816 So, now you've built your JDK, and made your first patch, and want to
1817 contribute it back to the OpenJDK Community.
1818
1819 First of all: Thank you! We gladly welcome your contribution.
1820 However, please bear in mind that the JDK is a massive project, and we must ask
1821 you to follow our rules and guidelines to be able to accept your contribution.
1822
1823 The official place to start is the ['How to contribute' page](
1824 http://openjdk.java.net/contribute/). There is also an official (but somewhat
1825 outdated and skimpy on details) [Developer's Guide](
1826 http://openjdk.java.net/guide/).
1827
1828 If this seems overwhelming to you, the Adoption Group is there to help you! A
1829 good place to start is their ['New Contributor' page](
1830 https://wiki.openjdk.java.net/display/Adoption/New+Contributor), or start
1831 reading the comprehensive [Getting Started Kit](
1832 https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The
1833 Adoption Group will also happily answer any questions you have about
1834 contributing. Contact them by [mail](
1835 http://mail.openjdk.java.net/mailman/listinfo/adoption-discuss) or [IRC](
1836 http://openjdk.java.net/irc/).
1837
1838 ---
1839 # Override styles from the base CSS file that are not ideal for this document.
1840 header-includes:
1841 - '<style type="text/css">pre, code, tt { color: #1d6ae5; }</style>'
1842 ---