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 ### SoftFloat
531
532 [Berkeley SoftFloat-3](http://www.jhauser.us/arithmetic/SoftFloat.html)
533 can be used on ARM processors without FPU to slightly enhance
534 the arithmetic precision of some floating point operations. It is not
535 required, system softfp routines can be used without any problems.
536 The precision loss is extremely small, but [the JCK detects it](
537 http://mail.openjdk.java.net/pipermail/aarch32-port-dev/2016-November/000611.html).
538
539 * To build the library, you will have to download its source and build it
540 for the target platform. To do so, take a look in its
541 `build/Linux-ARM-VFPv2-GCC` subdirectory.
542
543 You can enable this library by specifying a library prefix
544 via `--with-sflt=<path>` or by specifying path to softfloat.a
545 via `--with-sflt-lib=<path>` and path to directory
546 containing softfloat.h via `--with-sflt-include=<path>`. You
547 will also need to specify path to the SoftFloat license file with
548 `--with-sflt-license=<path>`. If you want to use the prefix option, ensure that
549 `<prefix>/lib/softfloat.a`, `<prefix>/include/softfloat.h` and
550 `<prefix>/share/softfloat/softfloat.md` exist. However you can override
551 the defaults by using the options above.
552
553 If you do not enable this library, standard system libraries
554 will be used instead.
555
556 ## Build Tools Requirements
557
558 ### Autoconf
559
560 The JDK requires [Autoconf](http://www.gnu.org/software/autoconf) on all
561 platforms. At least version 2.69 is required.
562
563 * To install on an apt-based Linux, try running `sudo apt-get install
564 autoconf`.
565 * To install on an rpm-based Linux, try running `sudo yum install
566 autoconf`.
567 * To install on macOS, try running `brew install autoconf`.
568 * To install on Windows, try running `<path to Cygwin setup>/setup-x86_64 -q
569 -P autoconf`.
570
571 If `configure` has problems locating your installation of autoconf, you can
572 specify it using the `AUTOCONF` environment variable, like this:
573
574 ```
575 AUTOCONF=<path to autoconf> configure ...
576 ```
577
578 ### GNU Make
579
580 The JDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors
581 of make are supported.
582
583 At least version 3.81 of GNU Make must be used. For distributions supporting
584 GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful
585 functionality to handle parallel building (supported by `--with-output-sync`)
586 and speed and stability improvements.
587
588 Note that `configure` locates and verifies a properly functioning version of
589 `make` and stores the path to this `make` binary in the configuration. If you
590 start a build using `make` on the command line, you will be using the version
591 of make found first in your `PATH`, and not necessarily the one stored in the
592 configuration. This initial make will be used as "bootstrap make", and in a
593 second stage, the make located by `configure` will be called. Normally, this
594 will present no issues, but if you have a very old `make`, or a non-GNU Make
595 `make` in your path, this might cause issues.
596
597 If you want to override the default make found by `configure`, use the `MAKE`
598 configure variable, e.g. `configure MAKE=/opt/gnu/make`.
599
600 On Solaris, it is common to call the GNU version of make by using `gmake`.
601
602 ### GNU Bash
603
604 The JDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells
605 are supported.
606
607 At least version 3.2 of GNU Bash must be used.
608
609 ## Running Configure
610
611 To build the JDK, you need a "configuration", which consists of a directory
612 where to store the build output, coupled with information about the platform,
613 the specific build machine, and choices that affect how the JDK is built.
614
615 The configuration is created by the `configure` script. The basic invocation of
616 the `configure` script looks like this:
617
618 ```
619 bash configure [options]
620 ```
621
622 This will create an output directory containing the configuration and setup an
623 area for the build result. This directory typically looks like
624 `build/linux-x64-normal-server-release`, but the actual name depends on your
625 specific configuration. (It can also be set directly, see [Using Multiple
626 Configurations](#using-multiple-configurations)). This directory is referred to
627 as `$BUILD` in this documentation.
628
629 `configure` will try to figure out what system you are running on and where all
630 necessary build components are. If you have all prerequisites for building
631 installed, it should find everything. If it fails to detect any component
632 automatically, it will exit and inform you about the problem.
633
634 Some command line examples:
635
636 * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`:
637 ```
638 bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32
639 ```
640
641 * Create a debug build with the `server` JVM and DTrace enabled:
642 ```
643 bash configure --enable-debug --with-jvm-variants=server --enable-dtrace
644 ```
645
646 ### Common Configure Arguments
647
648 Here follows some of the most common and important `configure` argument.
649
650 To get up-to-date information on *all* available `configure` argument, please
651 run:
652 ```
653 bash configure --help
654 ```
655
656 (Note that this help text also include general autoconf options, like
657 `--dvidir`, that is not relevant to the JDK. To list only JDK-specific
658 features, use `bash configure --help=short` instead.)
659
660 #### Configure Arguments for Tailoring the Build
661
662 * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand
663 for `--with-debug-level=fastdebug`)
664 * `--with-debug-level=<level>` - Set the debug level, which can be `release`,
665 `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized`
666 is variant of `release` with additional Hotspot debug code.
667 * `--with-native-debug-symbols=<method>` - Specify if and how native debug
668 symbols should be built. Available methods are `none`, `internal`,
669 `external`, `zipped`. Default behavior depends on platform. See [Native
670 Debug Symbols](#native-debug-symbols) for more details.
671 * `--with-version-string=<string>` - Specify the version string this build
672 will be identified with.
673 * `--with-version-<part>=<value>` - A group of options, where `<part>` can be
674 any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use
675 these options to modify just the corresponding part of the version string
676 from the default, or the value provided by `--with-version-string`.
677 * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant
678 (or variants) of Hotspot. Valid variants are: `server`, `client`,
679 `minimal`, `core`, `zero`, `custom`. Note that not all
680 variants are possible to combine in a single build.
681 * `--with-jvm-features=<feature>[,<feature>...]` - Use the specified JVM
682 features when building Hotspot. The list of features will be enabled on top
683 of the default list. For the `custom` JVM variant, this default list is
684 empty. A complete list of available JVM features can be found using `bash
685 configure --help`.
686 * `--with-target-bits=<bits>` - Create a target binary suitable for running
687 on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build
688 platform, instead of doing a full cross-compile. (This is known as a
689 *reduced* build.)
690
691 On Linux, BSD and AIX, it is possible to override where Java by default
692 searches for runtime/JNI libraries. This can be useful in situations where
693 there is a special shared directory for system JNI libraries. This setting
694 can in turn be overriden at runtime by setting the `java.library.path` property.
695
696 * `--with-jni-libpath=<path>` - Use the specified path as a default
697 when searching for runtime libraries.
698
699 #### Configure Arguments for Native Compilation
700
701 * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources
702 * `--with-sysroot=<path>` - Use this directory as sysroot
703 * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the
704 default path when searching for all kinds of binaries
705 * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when
706 searching for toolchain binaries (compilers etc)
707 * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C
708 files
709 * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++
710 files
711 * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK
712 libraries
713
714 #### Configure Arguments for External Dependencies
715
716 * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK](
717 #boot-jdk-requirements)
718 * `--with-freetype=<path>` - Set the path to [FreeType](#freetype)
719 * `--with-cups=<path>` - Set the path to [CUPS](#cups)
720 * `--with-x=<path>` - Set the path to [X11](#x11)
721 * `--with-alsa=<path>` - Set the path to [ALSA](#alsa)
722 * `--with-libffi=<path>` - Set the path to [libffi](#libffi)
723 * `--with-sflt=<path>` - Enable and set the path to [SoftFloat](#softfloat)
724 library.
725 * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests](
726 #running-tests)
727
728 Certain third-party libraries used by the JDK (libjpeg, giflib, libpng, lcms
729 and zlib) are included in the JDK repository. The default behavior of the
730 JDK build is to use this version of these libraries, but they might be
731 replaced by an external version. To do so, specify `system` as the `<source>`
732 option in these arguments. (The default is `bundled`).
733
734 * `--with-libjpeg=<source>` - Use the specified source for libjpeg
735 * `--with-giflib=<source>` - Use the specified source for giflib
736 * `--with-libpng=<source>` - Use the specified source for libpng
737 * `--with-lcms=<source>` - Use the specified source for lcms
738 * `--with-zlib=<source>` - Use the specified source for zlib
739
740 On Linux, it is possible to select either static or dynamic linking of the C++
741 runtime. The default is static linking, with dynamic linking as fallback if the
742 static library is not found.
743
744 * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic`
745 or `default`) for linking the C++ runtime.
746
747 ### Configure Control Variables
748
749 It is possible to control certain aspects of `configure` by overriding the
750 value of `configure` variables, either on the command line or in the
751 environment.
752
753 Normally, this is **not recommended**. If used improperly, it can lead to a
754 broken configuration. Unless you're well versed in the build system, this is
755 hard to use properly. Therefore, `configure` will print a warning if this is
756 detected.
757
758 However, there are a few `configure` variables, known as *control variables*
759 that are supposed to be overriden on the command line. These are variables that
760 describe the location of tools needed by the build, like `MAKE` or `GREP`. If
761 any such variable is specified, `configure` will use that value instead of
762 trying to autodetect the tool. For instance, `bash configure
763 MAKE=/opt/gnumake4.0/bin/make`.
764
765 If a configure argument exists, use that instead, e.g. use `--with-jtreg`
766 instead of setting `JTREGEXE`.
767
768 Also note that, despite what autoconf claims, setting `CFLAGS` will not
769 accomplish anything. Instead use `--with-extra-cflags` (and similar for
770 `cxxflags` and `ldflags`).
771
772 ## Running Make
773
774 When you have a proper configuration, all you need to do to build the JDK is to
775 run `make`. (But see the warning at [GNU Make](#gnu-make) about running the
776 correct version of make.)
777
778 When running `make` without any arguments, the default target is used, which is
779 the same as running `make default` or `make jdk`. This will build a minimal (or
780 roughly minimal) set of compiled output (known as an "exploded image") needed
781 for a developer to actually execute the newly built JDK. The idea is that in an
782 incremental development fashion, when doing a normal make, you should only
783 spend time recompiling what's changed (making it purely incremental) and only
784 do the work that's needed to actually run and test your code.
785
786 The output of the exploded image resides in `$BUILD/jdk`. You can test the
787 newly built JDK like this: `$BUILD/jdk/bin/java -version`.
788
789 ### Common Make Targets
790
791 Apart from the default target, here are some common make targets:
792
793 * `hotspot` - Build all of hotspot (but only hotspot)
794 * `hotspot-<variant>` - Build just the specified jvm variant
795 * `images` or `product-images` - Build the JDK image
796 * `docs` or `docs-image` - Build the documentation image
797 * `test-image` - Build the test image
798 * `all` or `all-images` - Build all images (product, docs and test)
799 * `bootcycle-images` - Build images twice, second time with newly built JDK
800 (good for testing)
801 * `clean` - Remove all files generated by make, but not those generated by
802 configure
803 * `dist-clean` - Remove all files, including configuration
804
805 Run `make help` to get an up-to-date list of important make targets and make
806 control variables.
807
808 It is possible to build just a single module, a single phase, or a single phase
809 of a single module, by creating make targets according to these followin
810 patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`,
811 `launchers`, `libs` or `rmic`. See [Using Fine-Grained Make Targets](
812 #using-fine-grained-make-targets) for more details about this functionality.
813
814 * `<phase>` - Build the specified phase and everything it depends on
815 * `<module>` - Build the specified module and everything it depends on
816 * `<module>-<phase>` - Compile the specified phase for the specified module
817 and everything it depends on
818
819 Similarly, it is possible to clean just a part of the build by creating make
820 targets according to these patterns:
821
822 * `clean-<outputdir>` - Remove the subdir in the output dir with the name
823 * `clean-<phase>` - Remove all build results related to a certain build
824 phase
825 * `clean-<module>` - Remove all build results related to a certain module
826 * `clean-<module>-<phase>` - Remove all build results related to a certain
827 module and phase
828
829 ### Make Control Variables
830
831 It is possible to control `make` behavior by overriding the value of `make`
832 variables, either on the command line or in the environment.
833
834 Normally, this is **not recommended**. If used improperly, it can lead to a
835 broken build. Unless you're well versed in the build system, this is hard to
836 use properly. Therefore, `make` will print a warning if this is detected.
837
838 However, there are a few `make` variables, known as *control variables* that
839 are supposed to be overriden on the command line. These make up the "make time"
840 configuration, as opposed to the "configure time" configuration.
841
842 #### General Make Control Variables
843
844 * `JOBS` - Specify the number of jobs to build with. See [Build
845 Performance](#build-performance).
846 * `LOG` - Specify the logging level and functionality. See [Checking the
847 Build Log File](#checking-the-build-log-file)
848 * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using
849 Multiple Configurations](#using-multiple-configurations)
850
851 #### Test Make Control Variables
852
853 These make control variables only make sense when running tests. Please see
854 [Testing the JDK](testing.html) for details.
855
856 * `TEST`
857 * `TEST_JOBS`
858 * `JTREG`
859 * `GTEST`
860
861 #### Advanced Make Control Variables
862
863 These advanced make control variables can be potentially unsafe. See [Hints and
864 Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and
865 [Understanding the Build System](#understanding-the-build-system) for details.
866
867 * `SPEC`
868 * `CONF_CHECK`
869 * `COMPARE_BUILD`
870 * `JDK_FILTER`
871
872 ## Running Tests
873
874 Most of the JDK tests are using the [JTReg](http://openjdk.java.net/jtreg)
875 test framework. Make sure that your configuration knows where to find your
876 installation of JTReg. If this is not picked up automatically, use the
877 `--with-jtreg=<path to jtreg home>` option to point to the JTReg framework.
878 Note that this option should point to the JTReg home, i.e. the top directory,
879 containing `lib/jtreg.jar` etc.
880
881 The [Adoption Group](https://wiki.openjdk.java.net/display/Adoption) provides
882 recent builds of jtreg [here](
883 https://adopt-openjdk.ci.cloudbees.com/job/jtreg/lastSuccessfulBuild/artifact).
884 Download the latest `.tar.gz` file, unpack it, and point `--with-jtreg` to the
885 `jtreg` directory that you just unpacked.
886
887 To execute the most basic tests (tier 1), use:
888 ```
889 make run-test-tier1
890 ```
891
892 For more details on how to run tests, please see the [Testing
893 the JDK](testing.html) document.
894
895 ## Cross-compiling
896
897 Cross-compiling means using one platform (the *build* platform) to generate
898 output that can ran on another platform (the *target* platform).
899
900 The typical reason for cross-compiling is that the build is performed on a more
901 powerful desktop computer, but the resulting binaries will be able to run on a
902 different, typically low-performing system. Most of the complications that
903 arise when building for embedded is due to this separation of *build* and
904 *target* systems.
905
906 This requires a more complex setup and build procedure. This section assumes
907 you are familiar with cross-compiling in general, and will only deal with the
908 particularities of cross-compiling the JDK. If you are new to cross-compiling,
909 please see the [external links at Wikipedia](
910 https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start
911 on reading materials.
912
913 Cross-compiling the JDK requires you to be able to build both for the build
914 platform and for the target platform. The reason for the former is that we need
915 to build and execute tools during the build process, both native tools and Java
916 tools.
917
918 If all you want to do is to compile a 32-bit version, for the same OS, on a
919 64-bit machine, consider using `--with-target-bits=32` instead of doing a
920 full-blown cross-compilation. (While this surely is possible, it's a lot more
921 work and will take much longer to build.)
922
923 ### Cross compiling the easy way with OpenJDK devkits
924
925 The OpenJDK build system provides out-of-the box support for creating and using
926 so called devkits. A `devkit` is basically a collection of a cross-compiling
927 toolchain and a sysroot environment which can easily be used together with the
928 `--with-devkit` configure option to cross compile the OpenJDK. On Linux/x86_64,
929 the following command:
930 ```
931 bash configure --with-devkit=<devkit-path> --openjdk-target=ppc64-linux-gnu && make
932 ```
933
934 will configure and build OpenJDK for Linux/ppc64 assuming that `<devkit-path>`
935 points to a Linux/x86_64 to Linux/ppc64 devkit.
936
937 Devkits can be created from the `make/devkit` directory by executing:
938 ```
939 make [ TARGETS="<TARGET_TRIPLET>+" ] [ BASE_OS=<OS> ] [ BASE_OS_VERSION=<VER> ]
940 ```
941
942 where `TARGETS` contains one or more `TARGET_TRIPLET`s of the form
943 described in [section 3.4 of the GNU Autobook](
944 https://sourceware.org/autobook/autobook/autobook_17.html). If no
945 targets are given, a native toolchain for the current platform will be
946 created. Currently, at least the following targets are known to work:
947
948 Supported devkit targets
949 -------------------------
950 x86_64-linux-gnu
951 aarch64-linux-gnu
952 arm-linux-gnueabihf
953 ppc64-linux-gnu
954 ppc64le-linux-gnu
955 s390x-linux-gnu
956
957 `BASE_OS` must be one of "OEL6" for Oracle Enterprise Linux 6 or
958 "Fedora" (if not specified "OEL6" will be the default). If the base OS
959 is "Fedora" the corresponding Fedora release can be specified with the
960 help of the `BASE_OS_VERSION` option (with "27" as default version).
961 If the build is successful, the new devkits can be found in the
962 `build/devkit/result` subdirectory:
963 ```
964 cd make/devkit
965 make TARGETS="ppc64le-linux-gnu aarch64-linux-gnu" BASE_OS=Fedora BASE_OS_VERSION=21
966 ls -1 ../../build/devkit/result/
967 x86_64-linux-gnu-to-aarch64-linux-gnu
968 x86_64-linux-gnu-to-ppc64le-linux-gnu
969 ```
970
971 Notice that devkits are not only useful for targeting different build
972 platforms. Because they contain the full build dependencies for a
973 system (i.e. compiler and root file system), they can easily be used
974 to build well-known, reliable and reproducible build environments. You
975 can for example create and use a devkit with GCC 7.3 and a Fedora 12
976 sysroot environment (with glibc 2.11) on Ubuntu 14.04 (which doesn't
977 have GCC 7.3 by default) to produce OpenJDK binaries which will run on
978 all Linux systems with runtime libraries newer than the ones from
979 Fedora 12 (e.g. Ubuntu 16.04, SLES 11 or RHEL 6).
980
981 ### Boot JDK and Build JDK
982
983 When cross-compiling, make sure you use a boot JDK that runs on the *build*
984 system, and not on the *target* system.
985
986 To be able to build, we need a "Build JDK", which is a JDK built from the
987 current sources (that is, the same as the end result of the entire build
988 process), but able to run on the *build* system, and not the *target* system.
989 (In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when
990 building JDK 9.)
991
992 The build process will create a minimal Build JDK for you, as part of building.
993 To speed up the build, you can use `--with-build-jdk` to `configure` to point
994 to a pre-built Build JDK. Please note that the build result is unpredictable,
995 and can possibly break in subtle ways, if the Build JDK does not **exactly**
996 match the current sources.
997
998 ### Specifying the Target Platform
999
1000 You *must* specify the target platform when cross-compiling. Doing so will also
1001 automatically turn the build into a cross-compiling mode. The simplest way to
1002 do this is to use the `--openjdk-target` argument, e.g.
1003 `--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`.
1004 This will automatically set the `--build`, `--host` and `--target` options for
1005 autoconf, which can otherwise be confusing. (In autoconf terminology, the
1006 "target" is known as "host", and "target" is used for building a Canadian
1007 cross-compiler.)
1008
1009 ### Toolchain Considerations
1010
1011 You will need two copies of your toolchain, one which generates output that can
1012 run on the target system (the normal, or *target*, toolchain), and one that
1013 generates output that can run on the build system (the *build* toolchain). Note
1014 that cross-compiling is only supported for gcc at the time being. The gcc
1015 standard is to prefix cross-compiling toolchains with the target denominator.
1016 If you follow this standard, `configure` is likely to pick up the toolchain
1017 correctly.
1018
1019 The *build* toolchain will be autodetected just the same way the normal
1020 *build*/*target* toolchain will be autodetected when not cross-compiling. If
1021 this is not what you want, or if the autodetection fails, you can specify a
1022 devkit containing the *build* toolchain using `--with-build-devkit` to
1023 `configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments.
1024
1025 It is often helpful to locate the cross-compilation tools, headers and
1026 libraries in a separate directory, outside the normal path, and point out that
1027 directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and
1028 appending the directory when searching for cross-compilations tools
1029 (`--with-toolchain-path`). As a compact form, you can also use `--with-devkit`
1030 to point to a single directory, if it is correctly setup. (See `basics.m4` for
1031 details.)
1032
1033 If you are unsure what toolchain and versions to use, these have been proved
1034 working at the time of writing:
1035
1036 * [aarch64](
1037 https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-linux-gnu-4.8-2013.11_linux.tar.xz)
1038 * [arm 32-bit hardware floating point](
1039 https://launchpad.net/linaro-toolchain-unsupported/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux.tar.bz2)
1040
1041 ### Native Libraries
1042
1043 You will need copies of external native libraries for the *target* system,
1044 present on the *build* machine while building.
1045
1046 Take care not to replace the *build* system's version of these libraries by
1047 mistake, since that can render the *build* machine unusable.
1048
1049 Make sure that the libraries you point to (ALSA, X11, etc) are for the
1050 *target*, not the *build*, platform.
1051
1052 #### ALSA
1053
1054 You will need alsa libraries suitable for your *target* system. For most cases,
1055 using Debian's pre-built libraries work fine.
1056
1057 Note that alsa is needed even if you only want to build a headless JDK.
1058
1059 * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and
1060 search for the `libasound2` and `libasound2-dev` packages for your *target*
1061 system. Download them to /tmp.
1062
1063 * Install the libraries into the cross-compilation toolchain. For instance:
1064 ```
1065 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc
1066 dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb .
1067 dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb .
1068 ```
1069
1070 * If alsa is not properly detected by `configure`, you can point it out by
1071 `--with-alsa`.
1072
1073 #### X11
1074
1075 You will need X11 libraries suitable for your *target* system. For most cases,
1076 using Debian's pre-built libraries work fine.
1077
1078 Note that X11 is needed even if you only want to build a headless JDK.
1079
1080 * Go to [Debian Package Search](https://www.debian.org/distrib/packages),
1081 search for the following packages for your *target* system, and download them
1082 to /tmp/target-x11:
1083 * libxi
1084 * libxi-dev
1085 * x11proto-core-dev
1086 * x11proto-input-dev
1087 * x11proto-kb-dev
1088 * x11proto-render-dev
1089 * x11proto-xext-dev
1090 * libice-dev
1091 * libxrender
1092 * libxrender-dev
1093 * libxrandr-dev
1094 * libsm-dev
1095 * libxt-dev
1096 * libx11
1097 * libx11-dev
1098 * libxtst
1099 * libxtst-dev
1100 * libxext
1101 * libxext-dev
1102
1103 * Install the libraries into the cross-compilation toolchain. For instance:
1104 ```
1105 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr
1106 mkdir X11R6
1107 cd X11R6
1108 for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done
1109 mv usr/* .
1110 cd lib
1111 cp arm-linux-gnueabihf/* .
1112 ```
1113
1114 You can ignore the following messages. These libraries are not needed to
1115 successfully complete a full JDK build.
1116 ```
1117 cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory
1118 cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory
1119 cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory
1120 ```
1121
1122 * If the X11 libraries are not properly detected by `configure`, you can
1123 point them out by `--with-x`.
1124
1125 ### Creating And Using Sysroots With qemu-deboostrap
1126
1127 Fortunately, you can create sysroots for foreign architectures with tools
1128 provided by your OS. On Debian/Ubuntu systems, one could use `qemu-deboostrap` to
1129 create the *target* system chroot, which would have the native libraries and headers
1130 specific to that *target* system. After that, we can use the cross-compiler on the *build*
1131 system, pointing into chroot to get the build dependencies right. This allows building
1132 for foreign architectures with native compilation speed.
1133
1134 For example, cross-compiling to AArch64 from x86_64 could be done like this:
1135
1136 * Install cross-compiler on the *build* system:
1137 ```
1138 apt install g++-aarch64-linux-gnu gcc-aarch64-linux-gnu
1139 ```
1140
1141 * Create chroot on the *build* system, configuring it for *target* system:
1142 ```
1143 sudo qemu-debootstrap --arch=arm64 --verbose \
1144 --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 \
1145 --resolve-deps jessie /chroots/arm64 http://httpredir.debian.org/debian/
1146 ```
1147
1148 * Configure and build with newly created chroot as sysroot/toolchain-path:
1149 ```
1150 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/
1151 make images
1152 ls build/linux-aarch64-normal-server-release/
1153 ```
1154
1155 The build does not create new files in that chroot, so it can be reused for multiple builds
1156 without additional cleanup.
1157
1158 Architectures that are known to successfully cross-compile like this are:
1159
1160 Target `CC` `CXX` `--arch=...` `--openjdk-target=...`
1161 ------------ ------------------------- --------------------------- ------------- -----------------------
1162 x86 default default i386 i386-linux-gnu
1163 armhf gcc-arm-linux-gnueabihf g++-arm-linux-gnueabihf armhf arm-linux-gnueabihf
1164 aarch64 gcc-aarch64-linux-gnu g++-aarch64-linux-gnu arm64 aarch64-linux-gnu
1165 ppc64el gcc-powerpc64le-linux-gnu g++-powerpc64le-linux-gnu ppc64el powerpc64le-linux-gnu
1166 s390x gcc-s390x-linux-gnu g++-s390x-linux-gnu s390x s390x-linux-gnu
1167
1168 Additional architectures might be supported by Debian/Ubuntu Ports.
1169
1170 ### Building for ARM/aarch64
1171
1172 A common cross-compilation target is the ARM CPU. When building for ARM, it is
1173 useful to set the ABI profile. A number of pre-defined ABI profiles are
1174 available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt,
1175 armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer
1176 properly supported by the JDK.
1177
1178 ### Verifying the Build
1179
1180 The build will end up in a directory named like
1181 `build/linux-arm-normal-server-release`.
1182
1183 Inside this build output directory, the `images/jdk` will contain the newly
1184 built JDK, for your *target* system.
1185
1186 Copy these folders to your *target* system. Then you can run e.g.
1187 `images/jdk/bin/java -version`.
1188
1189 ## Build Performance
1190
1191 Building the JDK requires a lot of horsepower. Some of the build tools can be
1192 adjusted to utilize more or less of resources such as parallel threads and
1193 memory. The `configure` script analyzes your system and selects reasonable
1194 values for such options based on your hardware. If you encounter resource
1195 problems, such as out of memory conditions, you can modify the detected values
1196 with:
1197
1198 * `--with-num-cores` -- number of cores in the build system, e.g.
1199 `--with-num-cores=8`.
1200
1201 * `--with-memory-size` -- memory (in MB) available in the build system, e.g.
1202 `--with-memory-size=1024`
1203
1204 You can also specify directly the number of build jobs to use with
1205 `--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag
1206 to `make`. In most cases it will be ignored by the makefiles, but it can cause
1207 problems for some make targets.
1208
1209 It might also be necessary to specify the JVM arguments passed to the Boot JDK,
1210 using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the
1211 default JVM arguments passed to the Boot JDK.
1212
1213 At the end of a successful execution of `configure`, you will get a performance
1214 summary, indicating how well the build will perform. Here you will also get
1215 performance hints. If you want to build fast, pay attention to those!
1216
1217 If you want to tweak build performance, run with `make LOG=info` to get a build
1218 time summary at the end of the build process.
1219
1220 ### Disk Speed
1221
1222 If you are using network shares, e.g. via NFS, for your source code, make sure
1223 the build directory is situated on local disk (e.g. by `ln -s
1224 /localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely
1225 high for building on a network share; close to unusable.
1226
1227 Also, make sure that your build tools (including Boot JDK and toolchain) is
1228 located on a local disk and not a network share.
1229
1230 As has been stressed elsewhere, do use SSD for source code and build directory,
1231 as well as (if possible) the build tools.
1232
1233 ### Virus Checking
1234
1235 The use of virus checking software, especially on Windows, can *significantly*
1236 slow down building of the JDK. If possible, turn off such software, or exclude
1237 the directory containing the JDK source code from on-the-fly checking.
1238
1239 ### Ccache
1240
1241 The JDK build supports building with ccache when using gcc or clang. Using
1242 ccache can radically speed up compilation of native code if you often rebuild
1243 the same sources. Your milage may vary however, so we recommend evaluating it
1244 for yourself. To enable it, make sure it's on the path and configure with
1245 `--enable-ccache`.
1246
1247 ### Precompiled Headers
1248
1249 By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains
1250 were it is properly supported (clang, gcc, and Visual Studio). Normally, this
1251 speeds up the build process, but in some circumstances, it can actually slow
1252 things down.
1253
1254 You can experiment by disabling precompiled headers using
1255 `--disable-precompiled-headers`.
1256
1257 ### Icecc / icecream
1258
1259 [icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a
1260 distributed compiler network. If you have multiple machines available for
1261 building the JDK, you can drastically cut individual build times by utilizing
1262 it.
1263
1264 To use, setup an icecc network, and install icecc on the build machine. Then
1265 run `configure` using `--enable-icecc`.
1266
1267 ### Using sjavac
1268
1269 To speed up Java compilation, especially incremental compilations, you can try
1270 the experimental sjavac compiler by using `--enable-sjavac`.
1271
1272 ### Building the Right Target
1273
1274 Selecting the proper target to build can have dramatic impact on build time.
1275 For normal usage, `jdk` or the default target is just fine. You only need to
1276 build `images` for shipping, or if your tests require it.
1277
1278 See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on
1279 how to build an even smaller subset of the product.
1280
1281 ## Troubleshooting
1282
1283 If your build fails, it can sometimes be difficult to pinpoint the problem or
1284 find a proper solution.
1285
1286 ### Locating the Source of the Error
1287
1288 When a build fails, it can be hard to pinpoint the actual cause of the error.
1289 In a typical build process, different parts of the product build in parallel,
1290 with the output interlaced.
1291
1292 #### Build Failure Summary
1293
1294 To help you, the build system will print a failure summary at the end. It looks
1295 like this:
1296
1297 ```
1298 ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2)
1299
1300 === Output from failing command(s) repeated here ===
1301 * For target hotspot_variant-server_libjvm_objs_psMemoryPool.o:
1302 /localhome/hg/jdk9-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type
1303 ... (rest of output omitted)
1304
1305 * All command lines available in /localhome/hg/jdk9-sandbox/build/linux-x64/make-support/failure-logs.
1306 === End of repeated output ===
1307
1308 === Make failed targets repeated here ===
1309 lib/CompileJvm.gmk:207: recipe for target '/localhome/hg/jdk9-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed
1310 make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed
1311 === End of repeated output ===
1312
1313 Hint: Try searching the build log for the name of the first failed target.
1314 Hint: If caused by a warning, try configure --disable-warnings-as-errors.
1315 ```
1316
1317 Let's break it down! First, the selected configuration, and the top-level
1318 target you entered on the command line that caused the failure is printed.
1319
1320 Then, between the `Output from failing command(s) repeated here` and `End of
1321 repeated output` the first lines of output (stdout and stderr) from the actual
1322 failing command is repeated. In most cases, this is the error message that
1323 caused the build to fail. If multiple commands were failing (this can happen in
1324 a parallel build), output from all failed commands will be printed here.
1325
1326 The path to the `failure-logs` directory is printed. In this file you will find
1327 a `<target>.log` file that contains the output from this command in its
1328 entirety, and also a `<target>.cmd`, which contain the complete command line
1329 used for running this command. You can re-run the failing command by executing
1330 `. <path to failure-logs>/<target>.cmd` in your shell.
1331
1332 Another way to trace the failure is to follow the chain of make targets, from
1333 top-level targets to individual file targets. Between `Make failed targets
1334 repeated here` and `End of repeated output` the output from make showing this
1335 chain is repeated. The first failed recipe will typically contain the full path
1336 to the file in question that failed to compile. Following lines will show a
1337 trace of make targets why we ended up trying to compile that file.
1338
1339 Finally, some hints are given on how to locate the error in the complete log.
1340 In this example, we would try searching the log file for "`psMemoryPool.o`".
1341 Another way to quickly locate make errors in the log is to search for "`]
1342 Error`" or "`***`".
1343
1344 Note that the build failure summary will only help you if the issue was a
1345 compilation failure or similar. If the problem is more esoteric, or is due to
1346 errors in the build machinery, you will likely get empty output logs, and `No
1347 indication of failed target found` instead of the make target chain.
1348
1349 #### Checking the Build Log File
1350
1351 The output (stdout and stderr) from the latest build is always stored in
1352 `$BUILD/build.log`. The previous build log is stored as `build.log.old`. This
1353 means that it is not necessary to redirect the build output yourself if you
1354 want to process it.
1355
1356 You can increase the verbosity of the log file, by the `LOG` control variable
1357 to `make`. If you want to see the command lines used in compilations, use
1358 `LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug`
1359 or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g.
1360 `LOG=info,cmdlines`. The `debug` log level will show most shell commands
1361 executed by make, and `trace` will show all. Beware that both these log levels
1362 will produce a massive build log!
1363
1364 ### Fixing Unexpected Build Failures
1365
1366 Most of the time, the build will fail due to incorrect changes in the source
1367 code.
1368
1369 Sometimes the build can fail with no apparent changes that have caused the
1370 failure. If this is the first time you are building the JDK on this particular
1371 computer, and the build fails, the problem is likely with your build
1372 environment. But even if you have previously built the JDK with success, and it
1373 now fails, your build environment might have changed (perhaps due to OS
1374 upgrades or similar). But most likely, such failures are due to problems with
1375 the incremental rebuild.
1376
1377 #### Problems with the Build Environment
1378
1379 Make sure your configuration is correct. Re-run `configure`, and look for any
1380 warnings. Warnings that appear in the middle of the `configure` output is also
1381 repeated at the end, after the summary. The entire log is stored in
1382 `$BUILD/configure.log`.
1383
1384 Verify that the summary at the end looks correct. Are you indeed using the Boot
1385 JDK and native toolchain that you expect?
1386
1387 By default, the JDK has a strict approach where warnings from the compiler is
1388 considered errors which fail the build. For very new or very old compiler
1389 versions, this can trigger new classes of warnings, which thus fails the build.
1390 Run `configure` with `--disable-warnings-as-errors` to turn of this behavior.
1391 (The warnings will still show, but not make the build fail.)
1392
1393 #### Problems with Incremental Rebuilds
1394
1395 Incremental rebuilds mean that when you modify part of the product, only the
1396 affected parts get rebuilt. While this works great in most cases, and
1397 significantly speed up the development process, from time to time complex
1398 interdependencies will result in an incorrect build result. This is the most
1399 common cause for unexpected build problems.
1400
1401 Here are a suggested list of things to try if you are having unexpected build
1402 problems. Each step requires more time than the one before, so try them in
1403 order. Most issues will be solved at step 1 or 2.
1404
1405 1. Make sure your repository is up-to-date
1406
1407 Run `hg pull -u` to make sure you have the latest changes.
1408
1409 2. Clean build results
1410
1411 The simplest way to fix incremental rebuild issues is to run `make clean`.
1412 This will remove all build results, but not the configuration or any build
1413 system support artifacts. In most cases, this will solve build errors
1414 resulting from incremental build mismatches.
1415
1416 3. Completely clean the build directory.
1417
1418 If this does not work, the next step is to run `make dist-clean`, or
1419 removing the build output directory (`$BUILD`). This will clean all
1420 generated output, including your configuration. You will need to re-run
1421 `configure` after this step. A good idea is to run `make
1422 print-configuration` before running `make dist-clean`, as this will print
1423 your current `configure` command line. Here's a way to do this:
1424
1425 ```
1426 make print-configuration > current-configuration
1427 make dist-clean
1428 bash configure $(cat current-configuration)
1429 make
1430 ```
1431
1432 4. Re-clone the Mercurial repository
1433
1434 Sometimes the Mercurial repository gets in a state that causes the product
1435 to be un-buildable. In such a case, the simplest solution is often the
1436 "sledgehammer approach": delete the entire repository, and re-clone it.
1437 If you have local changes, save them first to a different location using
1438 `hg export`.
1439
1440 ### Specific Build Issues
1441
1442 #### Clock Skew
1443
1444 If you get an error message like this:
1445 ```
1446 File 'xxx' has modification time in the future.
1447 Clock skew detected. Your build may be incomplete.
1448 ```
1449 then the clock on your build machine is out of sync with the timestamps on the
1450 source files. Other errors, apparently unrelated but in fact caused by the
1451 clock skew, can occur along with the clock skew warnings. These secondary
1452 errors may tend to obscure the fact that the true root cause of the problem is
1453 an out-of-sync clock.
1454
1455 If you see these warnings, reset the clock on the build machine, run `make
1456 clean` and restart the build.
1457
1458 #### Out of Memory Errors
1459
1460 On Solaris, you might get an error message like this:
1461 ```
1462 Trouble writing out table to disk
1463 ```
1464 To solve this, increase the amount of swap space on your build machine.
1465
1466 On Windows, you might get error messages like this:
1467 ```
1468 fatal error - couldn't allocate heap
1469 cannot create ... Permission denied
1470 spawn failed
1471 ```
1472 This can be a sign of a Cygwin problem. See the information about solving
1473 problems in the [Cygwin](#cygwin) section. Rebooting the computer might help
1474 temporarily.
1475
1476 ### Getting Help
1477
1478 If none of the suggestions in this document helps you, or if you find what you
1479 believe is a bug in the build system, please contact the Build Group by sending
1480 a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net).
1481 Please include the relevant parts of the configure and/or build log.
1482
1483 If you need general help or advice about developing for the JDK, you can also
1484 contact the Adoption Group. See the section on [Contributing to OpenJDK](
1485 #contributing-to-openjdk) for more information.
1486
1487 ## Hints and Suggestions for Advanced Users
1488
1489 ### Setting Up a Repository for Pushing Changes (defpath)
1490
1491 To help you prepare a proper push path for a Mercurial repository, there exists
1492 a useful tool known as [defpath](
1493 http://openjdk.java.net/projects/code-tools/defpath). It will help you setup a
1494 proper push path for pushing changes to the JDK.
1495
1496 Install the extension by cloning
1497 `http://hg.openjdk.java.net/code-tools/defpath` and updating your `.hgrc` file.
1498 Here's one way to do this:
1499
1500 ```
1501 cd ~
1502 mkdir hg-ext
1503 cd hg-ext
1504 hg clone http://hg.openjdk.java.net/code-tools/defpath
1505 cat << EOT >> ~/.hgrc
1506 [extensions]
1507 defpath=~/hg-ext/defpath/defpath.py
1508 EOT
1509 ```
1510
1511 You can now setup a proper push path using:
1512 ```
1513 hg defpath -d -u <your OpenJDK username>
1514 ```
1515
1516 ### Bash Completion
1517
1518 The `configure` and `make` commands tries to play nice with bash command-line
1519 completion (using `<tab>` or `<tab><tab>`). To use this functionality, make
1520 sure you enable completion in your `~/.bashrc` (see instructions for bash in
1521 your operating system).
1522
1523 Make completion will work out of the box, and will complete valid make targets.
1524 For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`.
1525
1526 The `configure` script can get completion for options, but for this to work you
1527 need to help `bash` on the way. The standard way of running the script, `bash
1528 configure`, will not be understood by bash completion. You need `configure` to
1529 be the command to run. One way to achieve this is to add a simple helper script
1530 to your path:
1531
1532 ```
1533 cat << EOT > /tmp/configure
1534 #!/bin/bash
1535 if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then
1536 echo >&2 "Abort: Trying to call configure helper recursively"
1537 exit 1
1538 fi
1539
1540 bash \$PWD/configure "\$@"
1541 EOT
1542 chmod +x /tmp/configure
1543 sudo mv /tmp/configure /usr/local/bin
1544 ```
1545
1546 Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`.
1547
1548 ### Using Multiple Configurations
1549
1550 You can have multiple configurations for a single source repository. When you
1551 create a new configuration, run `configure --with-conf-name=<name>` to create a
1552 configuration with the name `<name>`. Alternatively, you can create a directory
1553 under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd
1554 build/<name> && bash ../../configure`.
1555
1556 Then you can build that configuration using `make CONF_NAME=<name>` or `make
1557 CONF=<pattern>`, where `<pattern>` is a substring matching one or several
1558 configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will
1559 match *all* available configuration, so `make CONF= hotspot` will build the
1560 `hotspot` target for all configurations. Alternatively, you can execute `make`
1561 in the configuration directory, e.g. `cd build/<name> && make`.
1562
1563 ### Handling Reconfigurations
1564
1565 If you update the repository and part of the configure script has changed, the
1566 build system will force you to re-run `configure`.
1567
1568 Most of the time, you will be fine by running `configure` again with the same
1569 arguments as the last time, which can easily be performed by `make
1570 reconfigure`. To simplify this, you can use the `CONF_CHECK` make control
1571 variable, either as `make CONF_CHECK=auto`, or by setting an environment
1572 variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc`
1573 file, `make` will always run `reconfigure` automatically whenever the configure
1574 script has changed.
1575
1576 You can also use `CONF_CHECK=ignore` to skip the check for a needed configure
1577 update. This might speed up the build, but comes at the risk of an incorrect
1578 build result. This is only recommended if you know what you're doing.
1579
1580 From time to time, you will also need to modify the command line to `configure`
1581 due to changes. Use `make print-configure` to show the command line used for
1582 your current configuration.
1583
1584 ### Using Fine-Grained Make Targets
1585
1586 The default behavior for make is to create consistent and correct output, at
1587 the expense of build speed, if necessary.
1588
1589 If you are prepared to take some risk of an incorrect build, and know enough of
1590 the system to understand how things build and interact, you can speed up the
1591 build process considerably by instructing make to only build a portion of the
1592 product.
1593
1594 #### Building Individual Modules
1595
1596 The safe way to use fine-grained make targets is to use the module specific
1597 make targets. All source code in the JDK is organized so it belongs to a
1598 module, e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific
1599 module, by giving it as make target: `make jdk.jdwp.agent`. If the specified
1600 module depends on other modules (e.g. `java.base`), those modules will be built
1601 first.
1602
1603 You can also specify a set of modules, just as you can always specify a set of
1604 make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi
1605 jdk.crypto.ucrypto`
1606
1607 #### Building Individual Module Phases
1608
1609 The build process for each module is divided into separate phases. Not all
1610 modules need all phases. Which are needed depends on what kind of source code
1611 and other artifact the module consists of. The phases are:
1612
1613 * `gensrc` (Generate source code to compile)
1614 * `gendata` (Generate non-source code artifacts)
1615 * `copy` (Copy resource artifacts)
1616 * `java` (Compile Java code)
1617 * `launchers` (Compile native executables)
1618 * `libs` (Compile native libraries)
1619 * `rmic` (Run the `rmic` tool)
1620
1621 You can build only a single phase for a module by using the notation
1622 `$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`,
1623 use `make java.base-gensrc`.
1624
1625 Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if
1626 present). Make will build all needed prerequisites before building the
1627 requested phase.
1628
1629 #### Skipping the Dependency Check
1630
1631 When using an iterative development style with frequent quick rebuilds, the
1632 dependency check made by make can take up a significant portion of the time
1633 spent on the rebuild. In such cases, it can be useful to bypass the dependency
1634 check in make.
1635
1636 > **Note that if used incorrectly, this can lead to a broken build!**
1637
1638 To achieve this, append `-only` to the build target. For instance, `make
1639 jdk.jdwp.agent-java-only` will *only* build the `java` phase of the
1640 `jdk.jdwp.agent` module. If the required dependencies are not present, the
1641 build can fail. On the other hand, the execution time measures in milliseconds.
1642
1643 A useful pattern is to build the first time normally (e.g. `make
1644 jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target.
1645
1646 #### Rebuilding Part of java.base (JDK\_FILTER)
1647
1648 If you are modifying files in `java.base`, which is the by far largest module
1649 in the JDK, then you need to rebuild all those files whenever a single file has
1650 changed. (This inefficiency will hopefully be addressed in JDK 10.)
1651
1652 As a hack, you can use the make control variable `JDK_FILTER` to specify a
1653 pattern that will be used to limit the set of files being recompiled. For
1654 instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods,
1655 `make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation
1656 to files in the `javax.crypto` package.
1657
1658 ### Learn About Mercurial
1659
1660 To become an efficient JDK developer, it is recommended that you invest in
1661 learning Mercurial properly. Here are some links that can get you started:
1662
1663 * [Mercurial for git users](http://www.mercurial-scm.org/wiki/GitConcepts)
1664 * [The official Mercurial tutorial](http://www.mercurial-scm.org/wiki/Tutorial)
1665 * [hg init](http://hginit.com/)
1666 * [Mercurial: The Definitive Guide](http://hgbook.red-bean.com/read/)
1667
1668 ## Understanding the Build System
1669
1670 This section will give you a more technical description on the details of the
1671 build system.
1672
1673 ### Configurations
1674
1675 The build system expects to find one or more configuration. These are
1676 technically defined by the `spec.gmk` in a subdirectory to the `build`
1677 subdirectory. The `spec.gmk` file is generated by `configure`, and contains in
1678 principle the configuration (directly or by files included by `spec.gmk`).
1679
1680 You can, in fact, select a configuration to build by pointing to the `spec.gmk`
1681 file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`.
1682 While this is not the recommended way to call `make` as a user, it is what is
1683 used under the hood by the build system.
1684
1685 ### Build Output Structure
1686
1687 The build output for a configuration will end up in `build/<configuration
1688 name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory
1689 contains the following important directories:
1690
1691 ```
1692 buildtools/
1693 configure-support/
1694 hotspot/
1695 images/
1696 jdk/
1697 make-support/
1698 support/
1699 test-results/
1700 test-support/
1701 ```
1702
1703 This is what they are used for:
1704
1705 * `images`: This is the directory were the output of the `*-image` make
1706 targets end up. For instance, `make jdk-image` ends up in `images/jdk`.
1707
1708 * `jdk`: This is the "exploded image". After `make jdk`, you will be able to
1709 launch the newly built JDK by running `$BUILD/jdk/bin/java`.
1710
1711 * `test-results`: This directory contains the results from running tests.
1712
1713 * `support`: This is an area for intermediate files needed during the build,
1714 e.g. generated source code, object files and class files. Some noteworthy
1715 directories in `support` is `gensrc`, which contains the generated source
1716 code, and the `modules_*` directories, which contains the files in a
1717 per-module hierarchy that will later be collapsed into the `jdk` directory
1718 of the exploded image.
1719
1720 * `buildtools`: This is an area for tools compiled for the build platform
1721 that are used during the rest of the build.
1722
1723 * `hotspot`: This is an area for intermediate files needed when building
1724 hotspot.
1725
1726 * `configure-support`, `make-support` and `test-support`: These directories
1727 contain files that are needed by the build system for `configure`, `make`
1728 and for running tests.
1729
1730 ### Fixpath
1731
1732 Windows path typically look like `C:\User\foo`, while Unix paths look like
1733 `/home/foo`. Tools with roots from Unix often experience issues related to this
1734 mismatch when running on Windows.
1735
1736 In the JDK build, we always use Unix paths internally, and only just before
1737 calling a tool that does not understand Unix paths do we convert them to
1738 Windows paths.
1739
1740 This conversion is done by the `fixpath` tool, which is a small wrapper that
1741 modifies unix-style paths to Windows-style paths in command lines. Fixpath is
1742 compiled automatically by `configure`.
1743
1744 ### Native Debug Symbols
1745
1746 Native libraries and executables can have debug symbol (and other debug
1747 information) associated with them. How this works is very much platform
1748 dependent, but a common problem is that debug symbol information takes a lot of
1749 disk space, but is rarely needed by the end user.
1750
1751 The JDK supports different methods on how to handle debug symbols. The
1752 method used is selected by `--with-native-debug-symbols`, and available methods
1753 are `none`, `internal`, `external`, `zipped`.
1754
1755 * `none` means that no debug symbols will be generated during the build.
1756
1757 * `internal` means that debug symbols will be generated during the build, and
1758 they will be stored in the generated binary.
1759
1760 * `external` means that debug symbols will be generated during the build, and
1761 after the compilation, they will be moved into a separate `.debuginfo` file.
1762 (This was previously known as FDS, Full Debug Symbols).
1763
1764 * `zipped` is like `external`, but the .debuginfo file will also be zipped
1765 into a `.diz` file.
1766
1767 When building for distribution, `zipped` is a good solution. Binaries built
1768 with `internal` is suitable for use by developers, since they facilitate
1769 debugging, but should be stripped before distributed to end users.
1770
1771 ### Autoconf Details
1772
1773 The `configure` script is based on the autoconf framework, but in some details
1774 deviate from a normal autoconf `configure` script.
1775
1776 The `configure` script in the top level directory of the JDK is just a thin
1777 wrapper that calls `make/autoconf/configure`. This in turn will run `autoconf`
1778 to create the runnable (generated) configure script, as
1779 `.build/generated-configure.sh`. Apart from being responsible for the
1780 generation of the runnable script, the `configure` script also provides
1781 functionality that is not easily expressed in the normal Autoconf framework. As
1782 part of this functionality, the generated script is called.
1783
1784 The build system will detect if the Autoconf source files have changed, and
1785 will trigger a regeneration of the generated script if needed. You can also
1786 manually request such an update by `bash configure autogen`.
1787
1788 In previous versions of the JDK, the generated script was checked in at
1789 `make/autoconf/generated-configure.sh`. This is no longer the case.
1790
1791 ### Developing the Build System Itself
1792
1793 This section contains a few remarks about how to develop for the build system
1794 itself. It is not relevant if you are only making changes in the product source
1795 code.
1796
1797 While technically using `make`, the make source files of the JDK does not
1798 resemble most other Makefiles. Instead of listing specific targets and actions
1799 (perhaps using patterns), the basic modus operandi is to call a high-level
1800 function (or properly, macro) from the API in `make/common`. For instance, to
1801 compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module,
1802 a call like this would be made:
1803
1804 ```
1805 $(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \
1806 SETUP := GENERATE_OLDBYTECODE, \
1807 SRC := $(TOPDIR)/src/jkd.foo/share/classes, \
1808 INCLUDES := jdk/internal/foo, \
1809 BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \
1810 ))
1811 ```
1812
1813 By encapsulating and expressing the high-level knowledge of *what* should be
1814 done, rather than *how* it should be done (as is normal in Makefiles), we can
1815 build a much more powerful and flexible build system.
1816
1817 Correct dependency tracking is paramount. Sloppy dependency tracking will lead
1818 to improper parallelization, or worse, race conditions.
1819
1820 To test for/debug race conditions, try running `make JOBS=1` and `make
1821 JOBS=100` and see if it makes any difference. (It shouldn't).
1822
1823 To compare the output of two different builds and see if, and how, they differ,
1824 run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two
1825 builds you want to compare.
1826
1827 To automatically build two consecutive versions and compare them, use
1828 `COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value
1829 assignments, like this:
1830 ```
1831 make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot
1832 ```
1833 See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`.
1834
1835 To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`.
1836 Use `JOBS=1` to avoid parallelism.
1837
1838 Please check that you adhere to the [Code Conventions for the Build System](
1839 http://openjdk.java.net/groups/build/doc/code-conventions.html) before
1840 submitting patches.
1841
1842 ## Contributing to the JDK
1843
1844 So, now you've built your JDK, and made your first patch, and want to
1845 contribute it back to the OpenJDK Community.
1846
1847 First of all: Thank you! We gladly welcome your contribution.
1848 However, please bear in mind that the JDK is a massive project, and we must ask
1849 you to follow our rules and guidelines to be able to accept your contribution.
1850
1851 The official place to start is the ['How to contribute' page](
1852 http://openjdk.java.net/contribute/). There is also an official (but somewhat
1853 outdated and skimpy on details) [Developer's Guide](
1854 http://openjdk.java.net/guide/).
1855
1856 If this seems overwhelming to you, the Adoption Group is there to help you! A
1857 good place to start is their ['New Contributor' page](
1858 https://wiki.openjdk.java.net/display/Adoption/New+Contributor), or start
1859 reading the comprehensive [Getting Started Kit](
1860 https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The
1861 Adoption Group will also happily answer any questions you have about
1862 contributing. Contact them by [mail](
1863 http://mail.openjdk.java.net/mailman/listinfo/adoption-discuss) or [IRC](
1864 http://openjdk.java.net/irc/).
1865
1866 ---
1867 # Override styles from the base CSS file that are not ideal for this document.
1868 header-includes:
1869 - '<style type="text/css">pre, code, tt { color: #1d6ae5; }</style>'
1870 ---