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 Git (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 `git clone https://git.openjdk.org/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.org/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 Git site](https://git.openjdk.org/) you
51 can see a list of all available repositories. If you want to build an older version,
52 e.g. JDK 11, it is recommended that you get the `jdk11u` repo, which contains
53 incremental updates, instead of the `jdk11` repo, which was frozen at JDK 11 GA.
54
55 If you are new to Git, a good place to start is the book [Pro
56 Git](https://git-scm.com/book/en/v2). The rest of this document
57 assumes a working knowledge of Git.
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, if using [Cygwin](#cygwin), extra care must be taken to make sure
79 the 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 * You need to install a git client. You have two choices, Cygwin git or
93 Git for Windows. Unfortunately there are pros and cons with each choice.
94
95 * The Cygwin `git` client has no line ending issues and understands
96 Cygwin paths (which are used throughout the JDK build system).
97 However, it does not currently work well with the Skara CLI tooling.
98 Please see the [Skara wiki on Git clients](
99 https://wiki.openjdk.org/display/SKARA/Skara#Skara-Git) for
100 up-to-date information about the Skara git client support.
101
102 * The [Git for Windows](https://gitforwindows.org) client has issues
103 with line endings, and do not understand Cygwin paths. It does work
104 well with the Skara CLI tooling, however. To alleviate the line ending
105 problems, make sure you set `core.autocrlf` to `false` (this is asked
106 during installation).
107
108 Failure to follow this procedure might result in hard-to-debug build
109 problems.
110
111 ## Build Hardware Requirements
112
113 The JDK is a massive project, and require machines ranging from decent to
114 powerful to be able to build in a reasonable amount of time, or to be able to
115 complete a build at all.
116
117 We *strongly* recommend usage of an SSD disk for the build, since disk speed is
118 one of the limiting factors for build performance.
119
120 ### Building on x86
121
122 At a minimum, a machine with 2-4 cores is advisable, as well as 2-4 GB of RAM.
123 (The more cores to use, the more memory you need.) At least 6 GB of free disk
124 space is required.
125
126 Even for 32-bit builds, it is recommended to use a 64-bit build machine, and
127 instead create a 32-bit target using `--with-target-bits=32`.
128
129 Note: The Widows x86 port is deprecated.
130
131 ### Building on aarch64
132
133 At a minimum, a machine with 8 cores is advisable, as well as 8 GB of RAM.
134 (The more cores to use, the more memory you need.) At least 6 GB of free disk
135 space is required.
136
137 If you do not have access to sufficiently powerful hardware, it is also
138 possible to use [cross-compiling](#cross-compiling).
139
140 #### Branch Protection
141
142 In order to use Branch Protection features in the VM, `--enable-branch-protection`
143 must be used. This option requires C++ compiler support (GCC 9.1.0+ or Clang
144 10+). The resulting build can be run on both machines with and without support
145 for branch protection in hardware. Branch Protection is only supported for
146 Linux targets.
147
148 ### Building on 32-bit arm
149
150 This is not recommended. Instead, see the section on [Cross-compiling](
151 #cross-compiling).
152
153 ## Operating System Requirements
154
155 The mainline JDK project supports Linux, macOS, AIX and Windows.
156 Support for other operating system, e.g. BSD, exists in separate "port"
157 projects.
158
159 In general, the JDK can be built on a wide range of versions of these operating
160 systems, but the further you deviate from what is tested on a daily basis, the
161 more likely you are to run into problems.
162
163 This table lists the OS versions used by Oracle when building the JDK. Such
164 information is always subject to change, but this table is up to date at the
165 time of writing.
166
167 Operating system Vendor/version used
168 ----------------- -------------------------------------------------------
169 Linux Oracle Enterprise Linux 6.4 / 7.6
170 macOS Mac OS X 10.13 (High Sierra)
171 Windows Windows Server 2012 R2
172
173 The double version numbers for Linux are due to the hybrid model
174 used at Oracle, where header files and external libraries from an older version
175 are used when building on a more modern version of the OS.
176
177 The Build Group has a wiki page with [Supported Build Platforms](
178 https://wiki.openjdk.org/display/Build/Supported+Build+Platforms). From
179 time to time, this is updated by contributors to list successes or failures of
180 building on different platforms.
181
182 ### Windows
183
184 Windows XP is not a supported platform, but all newer Windows should be able to
185 build the JDK.
186
187 On Windows, it is important that you pay attention to the instructions in the
188 [Special Considerations](#special-considerations).
189
190 Windows is the only non-POSIX OS supported by the JDK, and as such, requires
191 some extra care. A POSIX support layer is required to build on Windows.
192 Currently, the only supported such layers are Cygwin, Windows Subsystem for
193 Linux (WSL), and MSYS2. (MSYS is no longer supported due to an outdated bash;
194 While OpenJDK can be built with MSYS2, support for it is still experimental, so
195 build failures and unusual errors are not uncommon.)
196
197 Internally in the build system, all paths are represented as Unix-style paths,
198 e.g. `/cygdrive/c/git/jdk/Makefile` rather than `C:\git\jdk\Makefile`. This
199 rule also applies to input to the build system, e.g. in arguments to
200 `configure`. So, use `--with-msvcr-dll=/cygdrive/c/msvcr100.dll` rather than
201 `--with-msvcr-dll=c:\msvcr100.dll`. For details on this conversion, see the section
202 on [Fixpath](#fixpath).
203
204 Note: The Widows x86 port is deprecated.
205
206 #### Cygwin
207
208 A functioning [Cygwin](http://www.cygwin.com/) environment is required for
209 building the JDK on Windows. If you have a 64-bit OS, we strongly recommend
210 using the 64-bit version of Cygwin.
211
212 **Note:** Cygwin has a model of continuously updating all packages without any
213 easy way to install or revert to a specific version of a package. This means
214 that whenever you add or update a package in Cygwin, you might (inadvertently)
215 update tools that are used by the JDK build process, and that can cause
216 unexpected build problems.
217
218 The JDK requires GNU Make 4.0 or greater in Cygwin. This is usually not a
219 problem, since Cygwin currently only distributes GNU Make at a version above
220 4.0.
221
222 Apart from the basic Cygwin installation, the following packages must also be
223 installed:
224
225 * `autoconf`
226 * `make`
227 * `zip`
228 * `unzip`
229
230 Often, you can install these packages using the following command line:
231 ```
232 <path to Cygwin setup>/setup-x86_64 -q -P autoconf -P make -P unzip -P zip
233 ```
234
235 Unfortunately, Cygwin can be unreliable in certain circumstances. If you
236 experience build tool crashes or strange issues when building on Windows,
237 please check the Cygwin FAQ on the ["BLODA" list](
238 https://cygwin.com/faq/faq.html#faq.using.bloda) and the section on [fork()
239 failures](https://cygwin.com/faq/faq.html#faq.using.fixing-fork-failures).
240
241 #### Windows Subsystem for Linux (WSL)
242
243 Windows 10 1809 or newer is supported due to a dependency on the wslpath utility
244 and support for environment variable sharing through WSLENV. Version 1803 can
245 work but intermittent build failures have been observed.
246
247 It's possible to build both Windows and Linux binaries from WSL. To build
248 Windows binaries, you must use a Windows boot JDK (located in a
249 Windows-accessible directory). To build Linux binaries, you must use a Linux
250 boot JDK. The default behavior is to build for Windows. To build for Linux, pass
251 `--build=x86_64-unknown-linux-gnu --openjdk-target=x86_64-unknown-linux-gnu`
252 to `configure`.
253
254 If building Windows binaries, the source code must be located in a Windows-
255 accessible directory. This is because Windows executables (such as Visual Studio
256 and the boot JDK) must be able to access the source code. Also, the drive where
257 the source is stored must be mounted as case-insensitive by changing either
258 /etc/fstab or /etc/wsl.conf in WSL. Individual directories may be corrected
259 using the fsutil tool in case the source was cloned before changing the mount
260 options.
261
262 Note that while it's possible to build on WSL, testing is still not fully
263 supported.
264
265 ### macOS
266
267 Apple is using a quite aggressive scheme of pushing OS updates, and coupling
268 these updates with required updates of Xcode. Unfortunately, this makes it
269 difficult for a project such as the JDK to keep pace with a continuously updated
270 machine running macOS. See the section on [Apple Xcode](#apple-xcode) on some
271 strategies to deal with this.
272
273 It is recommended that you use at least Mac OS X 10.13 (High Sierra). At the time
274 of writing, the JDK has been successfully compiled on macOS 10.12 (Sierra).
275
276 The standard macOS environment contains the basic tooling needed to build, but
277 for external libraries a package manager is recommended. The JDK uses
278 [homebrew](https://brew.sh/) in the examples, but feel free to use whatever
279 manager you want (or none).
280
281 ### Linux
282
283 It is often not much problem to build the JDK on Linux. The only general advice
284 is to try to use the compilers, external libraries and header files as provided
285 by your distribution.
286
287 The basic tooling is provided as part of the core operating system, but you
288 will most likely need to install developer packages.
289
290 For apt-based distributions (Debian, Ubuntu, etc), try this:
291 ```
292 sudo apt-get install build-essential
293 ```
294
295 For rpm-based distributions (Fedora, Red Hat, etc), try this:
296 ```
297 sudo yum groupinstall "Development Tools"
298 ```
299
300 For Alpine Linux, aside from basic tooling, install the GNU versions of some
301 programs:
302
303 ```
304 sudo apk add build-base bash grep zip
305 ```
306
307 ### AIX
308
309 Please consult the AIX section of the [Supported Build Platforms](
310 https://wiki.openjdk.org/display/Build/Supported+Build+Platforms) OpenJDK
311 Build Wiki page for details about which versions of AIX are supported.
312
313 ## Native Compiler (Toolchain) Requirements
314
315 Large portions of the JDK consists of native code, that needs to be compiled to
316 be able to run on the target platform. In theory, toolchain and operating
317 system should be independent factors, but in practice there's more or less a
318 one-to-one correlation between target operating system and toolchain. There are
319 ongoing efforts to loosen this strict coupling between compiler and operating
320 system (see [JDK-8288293](https://bugs.openjdk.org/browse/JDK-8288293)) but it
321 will likely be a very long time before this goal can be realized.
322
323 | Operating system | Supported toolchain |
324 | ------------------ | ------------------------- |
325 | Linux | gcc, clang |
326 | macOS | Apple Xcode (using clang) |
327 | AIX | IBM XL C/C++ |
328 | Windows | Microsoft Visual Studio |
329
330 Please see the individual sections on the toolchains for version
331 recommendations. As a reference, these versions of the toolchains are used, at
332 the time of writing, by Oracle for the daily builds of the JDK. It should be
333 possible to compile the JDK with both older and newer versions, but the closer
334 you stay to this list, the more likely you are to compile successfully without
335 issues.
336
337 | Operating system | Toolchain version |
338 | ------------------ | ------------------------------------------ |
339 | Linux | gcc 11.2.0 |
340 | macOS | Apple Xcode 10.1 (using clang 10.0.0) |
341 | Windows | Microsoft Visual Studio 2022 update 17.1.0 |
342
343 All compilers are expected to be able to compile to the C99 language standard,
344 as some C99 features are used in the source code. Microsoft Visual Studio
345 doesn't fully support C99 so in practice shared code is limited to using C99
346 features that it does support.
347
348 ### gcc
349
350 The minimum accepted version of gcc is 5.0. Older versions will generate a warning
351 by `configure` and are unlikely to work.
352
353 The JDK is currently known to be able to compile with at least version 11.2 of
354 gcc.
355
356 In general, any version between these two should be usable.
357
358 ### clang
359
360 The minimum accepted version of clang is 3.5. Older versions will not be
361 accepted by `configure`.
362
363 To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`.
364
365 ### Apple Xcode
366
367 The oldest supported version of Xcode is 8.
368
369 You will need the Xcode command line developer tools to be able to build
370 the JDK. (Actually, *only* the command line tools are needed, not the IDE.)
371 The simplest way to install these is to run:
372 ```
373 xcode-select --install
374 ```
375
376 When updating Xcode, it is advisable to keep an older version for building the JDK.
377 To use a specific version of Xcode you have multiple options:
378
379 * Use `xcode-select -s` before running `configure`, e.g. `xcode-select -s /Applications/Xcode13.1.app`. The drawback is that the setting
380 is system wide and you may have to revert it after an OpenJDK build.
381 * Use configure option `--with-xcode-path`, e.g. `configure --with-xcode-path=/Applications/Xcode13.1.app`
382 This allows using a specific Xcode version for an OpenJDK build, independently of the active Xcode version by `xcode-select`.
383
384 If you have recently (inadvertently) updated your OS and/or Xcode version, and
385 the JDK can no longer be built, please see the section on [Problems with the
386 Build Environment](#problems-with-the-build-environment), and [Getting
387 Help](#getting-help) to find out if there are any recent, non-merged patches
388 available for this update.
389
390 ### Microsoft Visual Studio
391
392 The minimum accepted version is Visual Studio 2019 version 16.8. (Note that this
393 version is often presented as "MSVC 14.28", and reported by cl.exe as 19.28.)
394 Older versions will not be accepted by `configure` and will not work. The
395 maximum accepted version of Visual Studio is 2022.
396
397 If you have multiple versions of Visual Studio installed, `configure` will by
398 default pick the latest. You can request a specific version to be used by
399 setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2022`.
400
401 If you have Visual Studio installed but `configure` fails to detect it, it may
402 be because of [spaces in path](#spaces-in-path).
403
404 ### IBM XL C/C++
405
406 Please consult the AIX section of the [Supported Build Platforms](
407 https://wiki.openjdk.org/display/Build/Supported+Build+Platforms) OpenJDK
408 Build Wiki page for details about which versions of XLC are supported.
409
410
411 ## Boot JDK Requirements
412
413 Paradoxically, building the JDK requires a pre-existing JDK. This is called the
414 "boot JDK". The boot JDK does not, however, have to be a JDK built directly from
415 the source code available in the OpenJDK Community. If you are porting the JDK
416 to a new platform, chances are that there already exists another JDK for that
417 platform that is usable as boot JDK.
418
419 The rule of thumb is that the boot JDK for building JDK major version *N*
420 should be a JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be
421 suitable as boot JDK. However, the JDK should be able to "build itself", so an
422 up-to-date build of the current JDK source is an acceptable alternative. If
423 you are following the *N-1* rule, make sure you've got the latest update
424 version, since JDK 8 GA might not be able to build JDK 9 on all platforms.
425
426 Early in the release cycle, version *N-1* may not yet have been released. In
427 that case, the preferred boot JDK will be version *N-2* until version *N-1*
428 is available.
429
430 If the boot JDK is not automatically detected, or the wrong JDK is picked, use
431 `--with-boot-jdk` to point to the JDK to use.
432
433 ### Getting JDK binaries
434
435 JDK binaries for Linux, Windows and macOS can be downloaded from
436 [jdk.java.net](http://jdk.java.net). An alternative is to download the
437 [Oracle JDK](http://www.oracle.com/technetwork/java/javase/downloads). Another
438 is the [Adopt OpenJDK Project](https://adoptopenjdk.net/), which publishes
439 experimental prebuilt binaries for various platforms.
440
441 On Linux you can also get a JDK from the Linux distribution. On apt-based
442 distros (like Debian and Ubuntu), `sudo apt-get install openjdk-<VERSION>-jdk`
443 is typically enough to install a JDK \<VERSION\>. On rpm-based distros (like
444 Fedora and Red Hat), try `sudo yum install java-<VERSION>-openjdk-devel`.
445
446 ## External Library Requirements
447
448 Different platforms require different external libraries. In general, libraries
449 are not optional - that is, they are either required or not used.
450
451 If a required library is not detected by `configure`, you need to provide the
452 path to it. There are two forms of the `configure` arguments to point to an
453 external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to
454 include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise,
455 but require the include files and library files to reside in a default
456 hierarchy under this directory. In most cases, it works fine.
457
458 As a fallback, the second version allows you to point to the include directory
459 and the lib directory separately.
460
461 ### FreeType
462
463 FreeType2 from [The FreeType Project](http://www.freetype.org/) is not required
464 on any platform. The exception is on Unix-based platforms when configuring such
465 that the build artifacts will reference a system installed library,
466 rather than bundling the JDK's own copy.
467
468 * To install on an apt-based Linux, try running `sudo apt-get install
469 libfreetype6-dev`.
470 * To install on an rpm-based Linux, try running `sudo yum install
471 freetype-devel`.
472 * To install on Alpine Linux, try running `sudo apk add freetype-dev`.
473 * To install on macOS, try running `brew install freetype`.
474
475 Use `--with-freetype-include=<path>` and `--with-freetype-lib=<path>`
476 if `configure` does not automatically locate the platform FreeType files.
477
478 ### CUPS
479
480 CUPS, [Common UNIX Printing System](http://www.cups.org) header files are
481 required on all platforms, except Windows. Often these files are provided by
482 your operating system.
483
484 * To install on an apt-based Linux, try running `sudo apt-get install
485 libcups2-dev`.
486 * To install on an rpm-based Linux, try running `sudo yum install
487 cups-devel`.
488 * To install on Alpine Linux, try running `sudo apk add cups-dev`.
489
490 Use `--with-cups=<path>` if `configure` does not properly locate your CUPS
491 files.
492
493 ### X11
494
495 Certain [X11](http://www.x.org/) libraries and include files are required on
496 Linux.
497
498 * To install on an apt-based Linux, try running `sudo apt-get install
499 libx11-dev libxext-dev libxrender-dev libxrandr-dev libxtst-dev libxt-dev`.
500 * To install on an rpm-based Linux, try running `sudo yum install
501 libXtst-devel libXt-devel libXrender-devel libXrandr-devel libXi-devel`.
502 * To install on Alpine Linux, try running `sudo apk add libx11-dev
503 libxext-dev libxrender-dev libxrandr-dev libxtst-dev libxt-dev`.
504
505 Use `--with-x=<path>` if `configure` does not properly locate your X11 files.
506
507 ### ALSA
508
509 ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is
510 required on Linux. At least version 0.9.1 of ALSA is required.
511
512 * To install on an apt-based Linux, try running `sudo apt-get install
513 libasound2-dev`.
514 * To install on an rpm-based Linux, try running `sudo yum install
515 alsa-lib-devel`.
516 * To install on Alpine Linux, try running `sudo apk add alsa-lib-dev`.
517
518 Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA
519 files.
520
521 ### libffi
522
523 libffi, the [Portable Foreign Function Interface Library](
524 http://sourceware.org/libffi) is required when building the Zero version of
525 Hotspot.
526
527 * To install on an apt-based Linux, try running `sudo apt-get install
528 libffi-dev`.
529 * To install on an rpm-based Linux, try running `sudo yum install
530 libffi-devel`.
531 * To install on Alpine Linux, try running `sudo apk add libffi-dev`.
532
533 Use `--with-libffi=<path>` if `configure` does not properly locate your libffi
534 files.
535
536 ## Build Tools Requirements
537
538 ### Autoconf
539
540 The JDK requires [Autoconf](http://www.gnu.org/software/autoconf) on all
541 platforms. At least version 2.69 is required.
542
543 * To install on an apt-based Linux, try running `sudo apt-get install
544 autoconf`.
545 * To install on an rpm-based Linux, try running `sudo yum install
546 autoconf`.
547 * To install on Alpine Linux, try running `sudo apk add autoconf`.
548 * To install on macOS, try running `brew install autoconf`.
549 * To install on Windows, try running `<path to Cygwin setup>/setup-x86_64 -q
550 -P autoconf`.
551
552 If `configure` has problems locating your installation of autoconf, you can
553 specify it using the `AUTOCONF` environment variable, like this:
554
555 ```
556 AUTOCONF=<path to autoconf> configure ...
557 ```
558
559 ### GNU Make
560
561 The JDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors
562 of make are supported.
563
564 At least version 3.81 of GNU Make must be used. For distributions supporting
565 GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful
566 functionality to handle parallel building (supported by `--with-output-sync`)
567 and speed and stability improvements.
568
569 Note that `configure` locates and verifies a properly functioning version of
570 `make` and stores the path to this `make` binary in the configuration. If you
571 start a build using `make` on the command line, you will be using the version
572 of make found first in your `PATH`, and not necessarily the one stored in the
573 configuration. This initial make will be used as "bootstrap make", and in a
574 second stage, the make located by `configure` will be called. Normally, this
575 will present no issues, but if you have a very old `make`, or a non-GNU Make
576 `make` in your path, this might cause issues.
577
578 If you want to override the default make found by `configure`, use the `MAKE`
579 configure variable, e.g. `configure MAKE=/opt/gnu/make`.
580
581 ### GNU Bash
582
583 The JDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells
584 are supported.
585
586 At least version 3.2 of GNU Bash must be used.
587
588 ## Running Configure
589
590 To build the JDK, you need a "configuration", which consists of a directory
591 where to store the build output, coupled with information about the platform,
592 the specific build machine, and choices that affect how the JDK is built.
593
594 The configuration is created by the `configure` script. The basic invocation of
595 the `configure` script looks like this:
596
597 ```
598 bash configure [options]
599 ```
600
601 This will create an output directory containing the configuration and setup an
602 area for the build result. This directory typically looks like
603 `build/linux-x64-server-release`, but the actual name depends on your specific
604 configuration. (It can also be set directly, see [Using Multiple
605 Configurations](#using-multiple-configurations)). This directory is referred to
606 as `$BUILD` in this documentation.
607
608 `configure` will try to figure out what system you are running on and where all
609 necessary build components are. If you have all prerequisites for building
610 installed, it should find everything. If it fails to detect any component
611 automatically, it will exit and inform you about the problem.
612
613 Some command line examples:
614
615 * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`:
616 ```
617 bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32
618 ```
619
620 * Create a debug build with the `server` JVM and DTrace enabled:
621 ```
622 bash configure --enable-debug --with-jvm-variants=server --enable-dtrace
623 ```
624
625 ### Common Configure Arguments
626
627 Here follows some of the most common and important `configure` argument.
628
629 To get up-to-date information on *all* available `configure` argument, please
630 run:
631 ```
632 bash configure --help
633 ```
634
635 (Note that this help text also include general autoconf options, like
636 `--dvidir`, that is not relevant to the JDK. To list only JDK-specific
637 features, use `bash configure --help=short` instead.)
638
639 #### Configure Arguments for Tailoring the Build
640
641 * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand
642 for `--with-debug-level=fastdebug`)
643 * `--with-debug-level=<level>` - Set the debug level, which can be `release`,
644 `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized`
645 is variant of `release` with additional Hotspot debug code.
646 * `--with-native-debug-symbols=<method>` - Specify if and how native debug
647 symbols should be built. Available methods are `none`, `internal`,
648 `external`, `zipped`. Default behavior depends on platform. See [Native
649 Debug Symbols](#native-debug-symbols) for more details.
650 * `--with-version-string=<string>` - Specify the version string this build
651 will be identified with.
652 * `--with-version-<part>=<value>` - A group of options, where `<part>` can be
653 any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use
654 these options to modify just the corresponding part of the version string
655 from the default, or the value provided by `--with-version-string`.
656 * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant
657 (or variants) of Hotspot. Valid variants are: `server`, `client`,
658 `minimal`, `core`, `zero`, `custom`. Note that not all
659 variants are possible to combine in a single build.
660 * `--enable-jvm-feature-<feature>` or `--disable-jvm-feature-<feature>` -
661 Include (or exclude) `<feature>` as a JVM feature in Hotspot. You can also
662 specify a list of features to be enabled, separated by space or comma, as
663 `--with-jvm-features=<feature>[,<feature>...]`. If you prefix `<feature>`
664 with a `-`, it will be disabled. These options will modify the default list
665 of features for the JVM variant(s) you are building. For the `custom` JVM
666 variant, the default list is empty. A complete list of valid JVM features
667 can be found using `bash configure --help`.
668 * `--with-target-bits=<bits>` - Create a target binary suitable for running
669 on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build
670 platform, instead of doing a full cross-compile. (This is known as a
671 *reduced* build.)
672
673 On Linux, BSD and AIX, it is possible to override where Java by default
674 searches for runtime/JNI libraries. This can be useful in situations where
675 there is a special shared directory for system JNI libraries. This setting
676 can in turn be overridden at runtime by setting the `java.library.path` property.
677
678 * `--with-jni-libpath=<path>` - Use the specified path as a default
679 when searching for runtime libraries.
680
681 #### Configure Arguments for Native Compilation
682
683 * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources
684 * `--with-sysroot=<path>` - Use this directory as sysroot
685 * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the
686 default path when searching for all kinds of binaries
687 * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when
688 searching for toolchain binaries (compilers etc)
689 * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C
690 files
691 * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++
692 files
693 * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK
694 libraries
695
696 #### Configure Arguments for External Dependencies
697
698 * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK](
699 #boot-jdk-requirements)
700 * `--with-freetype=<path>` - Set the path to [FreeType](#freetype)
701 * `--with-cups=<path>` - Set the path to [CUPS](#cups)
702 * `--with-x=<path>` - Set the path to [X11](#x11)
703 * `--with-alsa=<path>` - Set the path to [ALSA](#alsa)
704 * `--with-libffi=<path>` - Set the path to [libffi](#libffi)
705 * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests](
706 #running-tests)
707
708 Certain third-party libraries used by the JDK (libjpeg, giflib, libpng, lcms
709 and zlib) are included in the JDK repository. The default behavior of the
710 JDK build is to use the included ("bundled") versions of libjpeg, giflib,
711 libpng and lcms.
712 For zlib, the system lib (if present) is used except on Windows and AIX.
713 However the bundled libraries may be replaced by an external version.
714 To do so, specify `system` as the `<source>` option in these arguments.
715 (The default is `bundled`).
716
717 * `--with-libjpeg=<source>` - Use the specified source for libjpeg
718 * `--with-giflib=<source>` - Use the specified source for giflib
719 * `--with-libpng=<source>` - Use the specified source for libpng
720 * `--with-lcms=<source>` - Use the specified source for lcms
721 * `--with-zlib=<source>` - Use the specified source for zlib
722
723 On Linux, it is possible to select either static or dynamic linking of the C++
724 runtime. The default is static linking, with dynamic linking as fallback if the
725 static library is not found.
726
727 * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic`
728 or `default`) for linking the C++ runtime.
729
730 ### Configure Control Variables
731
732 It is possible to control certain aspects of `configure` by overriding the
733 value of `configure` variables, either on the command line or in the
734 environment.
735
736 Normally, this is **not recommended**. If used improperly, it can lead to a
737 broken configuration. Unless you're well versed in the build system, this is
738 hard to use properly. Therefore, `configure` will print a warning if this is
739 detected.
740
741 However, there are a few `configure` variables, known as *control variables*
742 that are supposed to be overridden on the command line. These are variables that
743 describe the location of tools needed by the build, like `MAKE` or `GREP`. If
744 any such variable is specified, `configure` will use that value instead of
745 trying to autodetect the tool. For instance, `bash configure
746 MAKE=/opt/gnumake4.0/bin/make`.
747
748 If a configure argument exists, use that instead, e.g. use `--with-jtreg`
749 instead of setting `JTREGEXE`.
750
751 Also note that, despite what autoconf claims, setting `CFLAGS` will not
752 accomplish anything. Instead use `--with-extra-cflags` (and similar for
753 `cxxflags` and `ldflags`).
754
755 ## Running Make
756
757 When you have a proper configuration, all you need to do to build the JDK is to
758 run `make`. (But see the warning at [GNU Make](#gnu-make) about running the
759 correct version of make.)
760
761 When running `make` without any arguments, the default target is used, which is
762 the same as running `make default` or `make jdk`. This will build a minimal (or
763 roughly minimal) set of compiled output (known as an "exploded image") needed
764 for a developer to actually execute the newly built JDK. The idea is that in an
765 incremental development fashion, when doing a normal make, you should only
766 spend time recompiling what's changed (making it purely incremental) and only
767 do the work that's needed to actually run and test your code.
768
769 The output of the exploded image resides in `$BUILD/jdk`. You can test the
770 newly built JDK like this: `$BUILD/jdk/bin/java -version`.
771
772 ### Common Make Targets
773
774 Apart from the default target, here are some common make targets:
775
776 * `hotspot` - Build all of hotspot (but only hotspot)
777 * `hotspot-<variant>` - Build just the specified jvm variant
778 * `images` or `product-images` - Build the JDK image
779 * `docs` or `docs-image` - Build the documentation image
780 * `test-image` - Build the test image
781 * `all` or `all-images` - Build all images (product, docs and test)
782 * `bootcycle-images` - Build images twice, second time with newly built JDK
783 (good for testing)
784 * `clean` - Remove all files generated by make, but not those generated by
785 configure
786 * `dist-clean` - Remove all files, including configuration
787
788 Run `make help` to get an up-to-date list of important make targets and make
789 control variables.
790
791 It is possible to build just a single module, a single phase, or a single phase
792 of a single module, by creating make targets according to these followin
793 patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`,
794 `launchers`, or `libs`. See [Using Fine-Grained Make Targets](
795 #using-fine-grained-make-targets) for more details about this functionality.
796
797 * `<phase>` - Build the specified phase and everything it depends on
798 * `<module>` - Build the specified module and everything it depends on
799 * `<module>-<phase>` - Compile the specified phase for the specified module
800 and everything it depends on
801
802 Similarly, it is possible to clean just a part of the build by creating make
803 targets according to these patterns:
804
805 * `clean-<outputdir>` - Remove the subdir in the output dir with the name
806 * `clean-<phase>` - Remove all build results related to a certain build
807 phase
808 * `clean-<module>` - Remove all build results related to a certain module
809 * `clean-<module>-<phase>` - Remove all build results related to a certain
810 module and phase
811
812 ### Make Control Variables
813
814 It is possible to control `make` behavior by overriding the value of `make`
815 variables, either on the command line or in the environment.
816
817 Normally, this is **not recommended**. If used improperly, it can lead to a
818 broken build. Unless you're well versed in the build system, this is hard to
819 use properly. Therefore, `make` will print a warning if this is detected.
820
821 However, there are a few `make` variables, known as *control variables* that
822 are supposed to be overridden on the command line. These make up the "make time"
823 configuration, as opposed to the "configure time" configuration.
824
825 #### General Make Control Variables
826
827 * `JOBS` - Specify the number of jobs to build with. See [Build
828 Performance](#build-performance).
829 * `LOG` - Specify the logging level and functionality. See [Checking the
830 Build Log File](#checking-the-build-log-file)
831 * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using
832 Multiple Configurations](#using-multiple-configurations)
833
834 #### Test Make Control Variables
835
836 These make control variables only make sense when running tests. Please see
837 **Testing the JDK** ([html](testing.html), [markdown](testing.md)) for details.
838
839 * `TEST`
840 * `TEST_JOBS`
841 * `JTREG`
842 * `GTEST`
843
844 #### Advanced Make Control Variables
845
846 These advanced make control variables can be potentially unsafe. See [Hints and
847 Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and
848 [Understanding the Build System](#understanding-the-build-system) for details.
849
850 * `SPEC`
851 * `CONF_CHECK`
852 * `COMPARE_BUILD`
853 * `JDK_FILTER`
854 * `SPEC_FILTER`
855
856 ## Running Tests
857
858 Most of the JDK tests are using the [JTReg](http://openjdk.org/jtreg)
859 test framework. Make sure that your configuration knows where to find your
860 installation of JTReg. If this is not picked up automatically, use the
861 `--with-jtreg=<path to jtreg home>` option to point to the JTReg framework.
862 Note that this option should point to the JTReg home, i.e. the top directory,
863 containing `lib/jtreg.jar` etc.
864
865 The [Adoption Group](https://wiki.openjdk.org/display/Adoption) provides
866 recent builds of jtreg [here](
867 https://ci.adoptopenjdk.net/view/Dependencies/job/dependency_pipeline/lastSuccessfulBuild/artifact/jtreg/).
868 Download the latest `.tar.gz` file, unpack it, and point `--with-jtreg` to the
869 `jtreg` directory that you just unpacked.
870
871 Building of Hotspot Gtest suite requires the source code of Google
872 Test framework. The top directory, which contains both `googletest`
873 and `googlemock` directories, should be specified via `--with-gtest`.
874 The minimum supported version of Google Test is 1.13.0, whose source
875 code can be obtained:
876
877 * by downloading and unpacking the source bundle from [here](https://github.com/google/googletest/releases/tag/v1.13.0)
878 * or by checking out `v1.13.0` tag of `googletest` project: `git clone -b v1.13.0 https://github.com/google/googletest`
879
880 To execute the most basic tests (tier 1), use:
881 ```
882 make run-test-tier1
883 ```
884
885 For more details on how to run tests, please see **Testing the JDK**
886 ([html](testing.html), [markdown](testing.md)).
887
888 ## Signing
889
890 ### macOS
891
892 Modern versions of macOS require applications to be signed and notarizied before
893 distribution. See Apple's documentation for more background on what this means
894 and how it works. To help support this, the JDK build can be configured to
895 automatically sign all native binaries, and the JDK bundle, with all the options
896 needed for successful notarization, as well as all the entitlements required by
897 the JDK. To enable `hardened` signing, use configure parameter
898 `--with-macosx-codesign=hardened` and configure the signing identity you wish to
899 use with `--with-macosx-codesign-identity=<identity>`. The identity refers to a
900 signing identity from Apple that needs to be preinstalled on the build host.
901
902 When not signing for distribution with the hardened option, the JDK build will
903 still attempt to perform `adhoc` signing to add the special entitlement
904 `com.apple.security.get-task-allow` to each binary. This entitlement is required
905 to be able to dump core files from a process. Note that adding this entitlement
906 makes the build invalid for notarization, so it is only added when signing in
907 `debug` mode. To explicitly enable this kind of adhoc signing, use configure
908 parameter `--with-macosx-codesign=debug`. It will be enabled by default in most
909 cases.
910
911 It's also possible to completely disable any explicit codesign operations done
912 by the JDK build using the configure parameter `--without-macosx-codesign`.
913 The exact behavior then depends on the architecture. For macOS on x64, it (at
914 least at the time of this writing) results in completely unsigned binaries that
915 should still work fine for development and debugging purposes. On aarch64, the
916 Xcode linker will apply a default "adhoc" signing, without any entitlements.
917 Such a build does not allow dumping core files.
918
919 The default mode "auto" will try for `hardened` signing if the debug level is
920 `release` and either the default identity or the specified identity is valid.
921 If hardened isn't possible, then `debug` signing is chosen if it works. If
922 nothing works, the codesign build step is disabled.
923
924 ## Cross-compiling
925
926 Cross-compiling means using one platform (the *build* platform) to generate
927 output that can ran on another platform (the *target* platform).
928
929 The typical reason for cross-compiling is that the build is performed on a more
930 powerful desktop computer, but the resulting binaries will be able to run on a
931 different, typically low-performing system. Most of the complications that
932 arise when building for embedded is due to this separation of *build* and
933 *target* systems.
934
935 This requires a more complex setup and build procedure. This section assumes
936 you are familiar with cross-compiling in general, and will only deal with the
937 particularities of cross-compiling the JDK. If you are new to cross-compiling,
938 please see the [external links at Wikipedia](
939 https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start
940 on reading materials.
941
942 Cross-compiling the JDK requires you to be able to build both for the build
943 platform and for the target platform. The reason for the former is that we need
944 to build and execute tools during the build process, both native tools and Java
945 tools.
946
947 If all you want to do is to compile a 32-bit version, for the same OS, on a
948 64-bit machine, consider using `--with-target-bits=32` instead of doing a
949 full-blown cross-compilation. (While this surely is possible, it's a lot more
950 work and will take much longer to build.)
951
952 ### Cross compiling the easy way with OpenJDK devkits
953
954 The OpenJDK build system provides out-of-the box support for creating and using
955 so called devkits. A `devkit` is basically a collection of a cross-compiling
956 toolchain and a sysroot environment which can easily be used together with the
957 `--with-devkit` configure option to cross compile the OpenJDK. On Linux/x86_64,
958 the following command:
959 ```
960 bash configure --with-devkit=<devkit-path> --openjdk-target=ppc64-linux-gnu && make
961 ```
962
963 will configure and build OpenJDK for Linux/ppc64 assuming that `<devkit-path>`
964 points to a Linux/x86_64 to Linux/ppc64 devkit.
965
966 Devkits can be created from the `make/devkit` directory by executing:
967 ```
968 make [ TARGETS="<TARGET_TRIPLET>+" ] [ BASE_OS=<OS> ] [ BASE_OS_VERSION=<VER> ]
969 ```
970
971 where `TARGETS` contains one or more `TARGET_TRIPLET`s of the form
972 described in [section 3.4 of the GNU Autobook](
973 https://sourceware.org/autobook/autobook/autobook_17.html). If no
974 targets are given, a native toolchain for the current platform will be
975 created. Currently, at least the following targets are known to work:
976
977 Supported devkit targets
978 -------------------------
979 x86_64-linux-gnu
980 aarch64-linux-gnu
981 arm-linux-gnueabihf
982 ppc64-linux-gnu
983 ppc64le-linux-gnu
984 s390x-linux-gnu
985
986 `BASE_OS` must be one of "OEL6" for Oracle Enterprise Linux 6 or
987 "Fedora" (if not specified "OEL6" will be the default). If the base OS
988 is "Fedora" the corresponding Fedora release can be specified with the
989 help of the `BASE_OS_VERSION` option (with "27" as default version).
990 If the build is successful, the new devkits can be found in the
991 `build/devkit/result` subdirectory:
992 ```
993 cd make/devkit
994 make TARGETS="ppc64le-linux-gnu aarch64-linux-gnu" BASE_OS=Fedora BASE_OS_VERSION=21
995 ls -1 ../../build/devkit/result/
996 x86_64-linux-gnu-to-aarch64-linux-gnu
997 x86_64-linux-gnu-to-ppc64le-linux-gnu
998 ```
999
1000 Notice that devkits are not only useful for targeting different build
1001 platforms. Because they contain the full build dependencies for a
1002 system (i.e. compiler and root file system), they can easily be used
1003 to build well-known, reliable and reproducible build environments. You
1004 can for example create and use a devkit with GCC 7.3 and a Fedora 12
1005 sysroot environment (with glibc 2.11) on Ubuntu 14.04 (which doesn't
1006 have GCC 7.3 by default) to produce OpenJDK binaries which will run on
1007 all Linux systems with runtime libraries newer than the ones from
1008 Fedora 12 (e.g. Ubuntu 16.04, SLES 11 or RHEL 6).
1009
1010 ### Boot JDK and Build JDK
1011
1012 When cross-compiling, make sure you use a boot JDK that runs on the *build*
1013 system, and not on the *target* system.
1014
1015 To be able to build, we need a "Build JDK", which is a JDK built from the
1016 current sources (that is, the same as the end result of the entire build
1017 process), but able to run on the *build* system, and not the *target* system.
1018 (In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when
1019 building JDK 9.)
1020
1021 The build process will create a minimal Build JDK for you, as part of building.
1022 To speed up the build, you can use `--with-build-jdk` to `configure` to point
1023 to a pre-built Build JDK. Please note that the build result is unpredictable,
1024 and can possibly break in subtle ways, if the Build JDK does not **exactly**
1025 match the current sources.
1026
1027 ### Specifying the Target Platform
1028
1029 You *must* specify the target platform when cross-compiling. Doing so will also
1030 automatically turn the build into a cross-compiling mode. The simplest way to
1031 do this is to use the `--openjdk-target` argument, e.g.
1032 `--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`.
1033 This will automatically set the `--host` and `--target` options for
1034 autoconf, which can otherwise be confusing. (In autoconf terminology, the
1035 "target" is known as "host", and "target" is used for building a Canadian
1036 cross-compiler.)
1037
1038 If `--build` has not been explicitly passed to configure, `--openjdk-target`
1039 will autodetect the build platform and internally set the flag automatically,
1040 otherwise the platform that was explicitly passed to `--build` will be used
1041 instead.
1042
1043 ### Toolchain Considerations
1044
1045 You will need two copies of your toolchain, one which generates output that can
1046 run on the target system (the normal, or *target*, toolchain), and one that
1047 generates output that can run on the build system (the *build* toolchain). Note
1048 that cross-compiling is only supported for gcc at the time being. The gcc
1049 standard is to prefix cross-compiling toolchains with the target denominator.
1050 If you follow this standard, `configure` is likely to pick up the toolchain
1051 correctly.
1052
1053 The *build* toolchain will be autodetected just the same way the normal
1054 *build*/*target* toolchain will be autodetected when not cross-compiling. If
1055 this is not what you want, or if the autodetection fails, you can specify a
1056 devkit containing the *build* toolchain using `--with-build-devkit` to
1057 `configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments.
1058
1059 It is often helpful to locate the cross-compilation tools, headers and
1060 libraries in a separate directory, outside the normal path, and point out that
1061 directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and
1062 appending the directory when searching for cross-compilations tools
1063 (`--with-toolchain-path`). As a compact form, you can also use `--with-devkit`
1064 to point to a single directory, if it is correctly setup. (See `basics.m4` for
1065 details.)
1066
1067 ### Native Libraries
1068
1069 You will need copies of external native libraries for the *target* system,
1070 present on the *build* machine while building.
1071
1072 Take care not to replace the *build* system's version of these libraries by
1073 mistake, since that can render the *build* machine unusable.
1074
1075 Make sure that the libraries you point to (ALSA, X11, etc) are for the
1076 *target*, not the *build*, platform.
1077
1078 #### ALSA
1079
1080 You will need alsa libraries suitable for your *target* system. For most cases,
1081 using Debian's pre-built libraries work fine.
1082
1083 Note that alsa is needed even if you only want to build a headless JDK.
1084
1085 * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and
1086 search for the `libasound2` and `libasound2-dev` packages for your *target*
1087 system. Download them to /tmp.
1088
1089 * Install the libraries into the cross-compilation toolchain. For instance:
1090 ```
1091 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc
1092 dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb .
1093 dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb .
1094 ```
1095
1096 * If alsa is not properly detected by `configure`, you can point it out by
1097 `--with-alsa`.
1098
1099 #### X11
1100
1101 You will need X11 libraries suitable for your *target* system. For most cases,
1102 using Debian's pre-built libraries work fine.
1103
1104 Note that X11 is needed even if you only want to build a headless JDK.
1105
1106 * Go to [Debian Package Search](https://www.debian.org/distrib/packages),
1107 search for the following packages for your *target* system, and download them
1108 to /tmp/target-x11:
1109 * libxi
1110 * libxi-dev
1111 * x11proto-core-dev
1112 * x11proto-input-dev
1113 * x11proto-kb-dev
1114 * x11proto-render-dev
1115 * x11proto-xext-dev
1116 * libice-dev
1117 * libxrender
1118 * libxrender-dev
1119 * libxrandr-dev
1120 * libsm-dev
1121 * libxt-dev
1122 * libx11
1123 * libx11-dev
1124 * libxtst
1125 * libxtst-dev
1126 * libxext
1127 * libxext-dev
1128
1129 * Install the libraries into the cross-compilation toolchain. For instance:
1130 ```
1131 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr
1132 mkdir X11R6
1133 cd X11R6
1134 for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done
1135 mv usr/* .
1136 cd lib
1137 cp arm-linux-gnueabihf/* .
1138 ```
1139
1140 You can ignore the following messages. These libraries are not needed to
1141 successfully complete a full JDK build.
1142 ```
1143 cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory
1144 cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory
1145 cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory
1146 ```
1147
1148 * If the X11 libraries are not properly detected by `configure`, you can
1149 point them out by `--with-x`.
1150
1151 ### Cross compiling with Debian sysroots
1152
1153 Fortunately, you can create sysroots for foreign architectures with tools
1154 provided by your OS. On Debian/Ubuntu systems, one could use `qemu-deboostrap` to
1155 create the *target* system chroot, which would have the native libraries and headers
1156 specific to that *target* system. After that, we can use the cross-compiler on the *build*
1157 system, pointing into chroot to get the build dependencies right. This allows building
1158 for foreign architectures with native compilation speed.
1159
1160 For example, cross-compiling to AArch64 from x86_64 could be done like this:
1161
1162 * Install cross-compiler on the *build* system:
1163 ```
1164 apt install g++-aarch64-linux-gnu gcc-aarch64-linux-gnu
1165 ```
1166
1167 * Create chroot on the *build* system, configuring it for *target* system:
1168 ```
1169 sudo qemu-debootstrap \
1170 --arch=arm64 \
1171 --verbose \
1172 --include=fakeroot,symlinks,build-essential,libx11-dev,libxext-dev,libxrender-dev,libxrandr-dev,libxtst-dev,libxt-dev,libcups2-dev,libfontconfig1-dev,libasound2-dev,libfreetype6-dev,libpng-dev,libffi-dev \
1173 --resolve-deps \
1174 buster \
1175 ~/sysroot-arm64 \
1176 http://httpredir.debian.org/debian/
1177 ```
1178
1179 * Make sure the symlinks inside the newly created chroot point to proper locations:
1180 ```
1181 sudo chroot ~/sysroot-arm64 symlinks -cr .
1182 ```
1183
1184 * Configure and build with newly created chroot as sysroot/toolchain-path:
1185 ```
1186 sh ./configure \
1187 --openjdk-target=aarch64-linux-gnu \
1188 --with-sysroot=~/sysroot-arm64
1189 make images
1190 ls build/linux-aarch64-server-release/
1191 ```
1192
1193 The build does not create new files in that chroot, so it can be reused for multiple builds
1194 without additional cleanup.
1195
1196 The build system should automatically detect the toolchain paths and dependencies, but sometimes
1197 it might require a little nudge with:
1198
1199 * Native compilers: override `CC` or `CXX` for `./configure`
1200
1201 * Freetype lib location: override `--with-freetype-lib`, for example `${sysroot}/usr/lib/${target}/`
1202
1203 * Freetype includes location: override `--with-freetype-include` for example `${sysroot}/usr/include/freetype2/`
1204
1205 * X11 libraries location: override `--x-libraries`, for example `${sysroot}/usr/lib/${target}/`
1206
1207 Architectures that are known to successfully cross-compile like this are:
1208
1209 Target Debian tree Debian arch `--openjdk-target=...` `--with-jvm-variants=...`
1210 ------------ ------------ ------------- ------------------------ --------------
1211 x86 buster i386 i386-linux-gnu (all)
1212 arm buster armhf arm-linux-gnueabihf (all)
1213 aarch64 buster arm64 aarch64-linux-gnu (all)
1214 ppc64le buster ppc64el powerpc64le-linux-gnu (all)
1215 s390x buster s390x s390x-linux-gnu (all)
1216 mipsle buster mipsel mipsel-linux-gnu zero
1217 mips64le buster mips64el mips64el-linux-gnueabi64 zero
1218 armel buster arm arm-linux-gnueabi zero
1219 ppc sid powerpc powerpc-linux-gnu zero
1220 ppc64be sid ppc64 powerpc64-linux-gnu (all)
1221 m68k sid m68k m68k-linux-gnu zero
1222 alpha sid alpha alpha-linux-gnu zero
1223 sh4 sid sh4 sh4-linux-gnu zero
1224
1225 ### Building for ARM/aarch64
1226
1227 A common cross-compilation target is the ARM CPU. When building for ARM, it is
1228 useful to set the ABI profile. A number of pre-defined ABI profiles are
1229 available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt,
1230 armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer
1231 properly supported by the JDK.
1232
1233 ### Building for musl
1234
1235 Just like it's possible to cross-compile for a different CPU, it's possible to
1236 cross-compile for musl libc on a glibc-based *build* system.
1237 A devkit suitable for most target CPU architectures can be obtained from
1238 [musl.cc](https://musl.cc). After installing the required packages in the
1239 sysroot, configure the build with `--openjdk-target`:
1240
1241 ```
1242 sh ./configure --with-jvm-variants=server \
1243 --with-boot-jdk=$BOOT_JDK \
1244 --with-build-jdk=$BUILD_JDK \
1245 --openjdk-target=x86_64-unknown-linux-musl \
1246 --with-devkit=$DEVKIT \
1247 --with-sysroot=$SYSROOT
1248 ```
1249
1250 and run `make` normally.
1251
1252 ### Verifying the Build
1253
1254 The build will end up in a directory named like
1255 `build/linux-arm-normal-server-release`.
1256
1257 Inside this build output directory, the `images/jdk` will contain the newly
1258 built JDK, for your *target* system.
1259
1260 Copy these folders to your *target* system. Then you can run e.g.
1261 `images/jdk/bin/java -version`.
1262
1263 ## Build Performance
1264
1265 Building the JDK requires a lot of horsepower. Some of the build tools can be
1266 adjusted to utilize more or less of resources such as parallel threads and
1267 memory. The `configure` script analyzes your system and selects reasonable
1268 values for such options based on your hardware. If you encounter resource
1269 problems, such as out of memory conditions, you can modify the detected values
1270 with:
1271
1272 * `--with-num-cores` -- number of cores in the build system, e.g.
1273 `--with-num-cores=8`.
1274
1275 * `--with-memory-size` -- memory (in MB) available in the build system, e.g.
1276 `--with-memory-size=1024`
1277
1278 You can also specify directly the number of build jobs to use with
1279 `--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag
1280 to `make`. In most cases it will be ignored by the makefiles, but it can cause
1281 problems for some make targets.
1282
1283 It might also be necessary to specify the JVM arguments passed to the Boot JDK,
1284 using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the
1285 default JVM arguments passed to the Boot JDK.
1286
1287 At the end of a successful execution of `configure`, you will get a performance
1288 summary, indicating how well the build will perform. Here you will also get
1289 performance hints. If you want to build fast, pay attention to those!
1290
1291 If you want to tweak build performance, run with `make LOG=info` to get a build
1292 time summary at the end of the build process.
1293
1294 ### Disk Speed
1295
1296 If you are using network shares, e.g. via NFS, for your source code, make sure
1297 the build directory is situated on local disk (e.g. by `ln -s
1298 /localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely
1299 high for building on a network share; close to unusable.
1300
1301 Also, make sure that your build tools (including Boot JDK and toolchain) is
1302 located on a local disk and not a network share.
1303
1304 As has been stressed elsewhere, do use SSD for source code and build directory,
1305 as well as (if possible) the build tools.
1306
1307 ### Virus Checking
1308
1309 The use of virus checking software, especially on Windows, can *significantly*
1310 slow down building of the JDK. If possible, turn off such software, or exclude
1311 the directory containing the JDK source code from on-the-fly checking.
1312
1313 ### Ccache
1314
1315 The JDK build supports building with ccache when using gcc or clang. Using
1316 ccache can radically speed up compilation of native code if you often rebuild
1317 the same sources. Your milage may vary however, so we recommend evaluating it
1318 for yourself. To enable it, make sure it's on the path and configure with
1319 `--enable-ccache`.
1320
1321 ### Precompiled Headers
1322
1323 By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains
1324 were it is properly supported (clang, gcc, and Visual Studio). Normally, this
1325 speeds up the build process, but in some circumstances, it can actually slow
1326 things down.
1327
1328 You can experiment by disabling precompiled headers using
1329 `--disable-precompiled-headers`.
1330
1331 ### Icecc / icecream
1332
1333 [icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a
1334 distributed compiler network. If you have multiple machines available for
1335 building the JDK, you can drastically cut individual build times by utilizing
1336 it.
1337
1338 To use, setup an icecc network, and install icecc on the build machine. Then
1339 run `configure` using `--enable-icecc`.
1340
1341 ### Using the javac server
1342
1343 To speed up compilation of Java code, especially during incremental
1344 compilations, the javac server is automatically enabled in the configuration
1345 step by default. To explicitly enable or disable the javac server, use either
1346 `--enable-javac-server` or `--disable-javac-server`.
1347
1348 ### Building the Right Target
1349
1350 Selecting the proper target to build can have dramatic impact on build time.
1351 For normal usage, `jdk` or the default target is just fine. You only need to
1352 build `images` for shipping, or if your tests require it.
1353
1354 See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on
1355 how to build an even smaller subset of the product.
1356
1357 ## Troubleshooting
1358
1359 If your build fails, it can sometimes be difficult to pinpoint the problem or
1360 find a proper solution.
1361
1362 ### Locating the Source of the Error
1363
1364 When a build fails, it can be hard to pinpoint the actual cause of the error.
1365 In a typical build process, different parts of the product build in parallel,
1366 with the output interlaced.
1367
1368 #### Build Failure Summary
1369
1370 To help you, the build system will print a failure summary at the end. It looks
1371 like this:
1372
1373 ```
1374 ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2)
1375
1376 === Output from failing command(s) repeated here ===
1377 * For target hotspot_variant-server_libjvm_objs_psMemoryPool.o:
1378 /localhome/git/jdk-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type
1379 ... (rest of output omitted)
1380
1381 * All command lines available in /localhome/git/jdk-sandbox/build/linux-x64/make-support/failure-logs.
1382 === End of repeated output ===
1383
1384 === Make failed targets repeated here ===
1385 lib/CompileJvm.gmk:207: recipe for target '/localhome/git/jdk-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed
1386 make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed
1387 === End of repeated output ===
1388
1389 Hint: Try searching the build log for the name of the first failed target.
1390 Hint: If caused by a warning, try configure --disable-warnings-as-errors.
1391 ```
1392
1393 Let's break it down! First, the selected configuration, and the top-level
1394 target you entered on the command line that caused the failure is printed.
1395
1396 Then, between the `Output from failing command(s) repeated here` and `End of
1397 repeated output` the first lines of output (stdout and stderr) from the actual
1398 failing command is repeated. In most cases, this is the error message that
1399 caused the build to fail. If multiple commands were failing (this can happen in
1400 a parallel build), output from all failed commands will be printed here.
1401
1402 The path to the `failure-logs` directory is printed. In this file you will find
1403 a `<target>.log` file that contains the output from this command in its
1404 entirety, and also a `<target>.cmd`, which contain the complete command line
1405 used for running this command. You can re-run the failing command by executing
1406 `. <path to failure-logs>/<target>.cmd` in your shell.
1407
1408 Another way to trace the failure is to follow the chain of make targets, from
1409 top-level targets to individual file targets. Between `Make failed targets
1410 repeated here` and `End of repeated output` the output from make showing this
1411 chain is repeated. The first failed recipe will typically contain the full path
1412 to the file in question that failed to compile. Following lines will show a
1413 trace of make targets why we ended up trying to compile that file.
1414
1415 Finally, some hints are given on how to locate the error in the complete log.
1416 In this example, we would try searching the log file for "`psMemoryPool.o`".
1417 Another way to quickly locate make errors in the log is to search for "`]
1418 Error`" or "`***`".
1419
1420 Note that the build failure summary will only help you if the issue was a
1421 compilation failure or similar. If the problem is more esoteric, or is due to
1422 errors in the build machinery, you will likely get empty output logs, and `No
1423 indication of failed target found` instead of the make target chain.
1424
1425 #### Checking the Build Log File
1426
1427 The output (stdout and stderr) from the latest build is always stored in
1428 `$BUILD/build.log`. The previous build log is stored as `build.log.old`. This
1429 means that it is not necessary to redirect the build output yourself if you
1430 want to process it.
1431
1432 You can increase the verbosity of the log file, by the `LOG` control variable
1433 to `make`. If you want to see the command lines used in compilations, use
1434 `LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug`
1435 or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g.
1436 `LOG=info,cmdlines`. The `debug` log level will show most shell commands
1437 executed by make, and `trace` will show all. Beware that both these log levels
1438 will produce a massive build log!
1439
1440 ### Fixing Unexpected Build Failures
1441
1442 Most of the time, the build will fail due to incorrect changes in the source
1443 code.
1444
1445 Sometimes the build can fail with no apparent changes that have caused the
1446 failure. If this is the first time you are building the JDK on this particular
1447 computer, and the build fails, the problem is likely with your build
1448 environment. But even if you have previously built the JDK with success, and it
1449 now fails, your build environment might have changed (perhaps due to OS
1450 upgrades or similar). But most likely, such failures are due to problems with
1451 the incremental rebuild.
1452
1453 #### Problems with the Build Environment
1454
1455 Make sure your configuration is correct. Re-run `configure`, and look for any
1456 warnings. Warnings that appear in the middle of the `configure` output is also
1457 repeated at the end, after the summary. The entire log is stored in
1458 `$BUILD/configure.log`.
1459
1460 Verify that the summary at the end looks correct. Are you indeed using the Boot
1461 JDK and native toolchain that you expect?
1462
1463 By default, the JDK has a strict approach where warnings from the compiler is
1464 considered errors which fail the build. For very new or very old compiler
1465 versions, this can trigger new classes of warnings, which thus fails the build.
1466 Run `configure` with `--disable-warnings-as-errors` to turn of this behavior.
1467 (The warnings will still show, but not make the build fail.)
1468
1469 #### Problems with Incremental Rebuilds
1470
1471 Incremental rebuilds mean that when you modify part of the product, only the
1472 affected parts get rebuilt. While this works great in most cases, and
1473 significantly speed up the development process, from time to time complex
1474 interdependencies will result in an incorrect build result. This is the most
1475 common cause for unexpected build problems.
1476
1477 Here are a suggested list of things to try if you are having unexpected build
1478 problems. Each step requires more time than the one before, so try them in
1479 order. Most issues will be solved at step 1 or 2.
1480
1481 1. Make sure your repository is up-to-date
1482
1483 Run `git pull origin master` to make sure you have the latest changes.
1484
1485 2. Clean build results
1486
1487 The simplest way to fix incremental rebuild issues is to run `make clean`.
1488 This will remove all build results, but not the configuration or any build
1489 system support artifacts. In most cases, this will solve build errors
1490 resulting from incremental build mismatches.
1491
1492 3. Completely clean the build directory.
1493
1494 If this does not work, the next step is to run `make dist-clean`, or
1495 removing the build output directory (`$BUILD`). This will clean all
1496 generated output, including your configuration. You will need to re-run
1497 `configure` after this step. A good idea is to run `make
1498 print-configuration` before running `make dist-clean`, as this will print
1499 your current `configure` command line. Here's a way to do this:
1500
1501 ```
1502 make print-configuration > current-configuration
1503 make dist-clean
1504 bash configure $(cat current-configuration)
1505 make
1506 ```
1507
1508 4. Re-clone the Git repository
1509
1510 Sometimes the Git repository gets in a state that causes the product
1511 to be un-buildable. In such a case, the simplest solution is often the
1512 "sledgehammer approach": delete the entire repository, and re-clone it.
1513 If you have local changes, save them first to a different location using
1514 `git format-patch`.
1515
1516 ### Specific Build Issues
1517
1518 #### Clock Skew
1519
1520 If you get an error message like this:
1521 ```
1522 File 'xxx' has modification time in the future.
1523 Clock skew detected. Your build may be incomplete.
1524 ```
1525 then the clock on your build machine is out of sync with the timestamps on the
1526 source files. Other errors, apparently unrelated but in fact caused by the
1527 clock skew, can occur along with the clock skew warnings. These secondary
1528 errors may tend to obscure the fact that the true root cause of the problem is
1529 an out-of-sync clock.
1530
1531 If you see these warnings, reset the clock on the build machine, run `make
1532 clean` and restart the build.
1533
1534 #### Out of Memory Errors
1535
1536 On Windows, you might get error messages like this:
1537 ```
1538 fatal error - couldn't allocate heap
1539 cannot create ... Permission denied
1540 spawn failed
1541 ```
1542 This can be a sign of a Cygwin problem. See the information about solving
1543 problems in the [Cygwin](#cygwin) section. Rebooting the computer might help
1544 temporarily.
1545
1546 #### Spaces in Path
1547
1548 On Windows, when configuring, `fixpath.sh` may report that some directory
1549 names have spaces. Usually, it assumes those directories have
1550 [short paths](https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/fsutil-8dot3name).
1551 You can run `fsutil file setshortname` in `cmd` on certain directories, such as
1552 `Microsoft Visual Studio` or `Windows Kits`, to assign arbitrary short paths so
1553 `configure` can access them.
1554
1555 ### Getting Help
1556
1557 If none of the suggestions in this document helps you, or if you find what you
1558 believe is a bug in the build system, please contact the Build Group by sending
1559 a mail to [build-dev@openjdk.org](mailto:build-dev@openjdk.org).
1560 Please include the relevant parts of the configure and/or build log.
1561
1562 If you need general help or advice about developing for the JDK, you can also
1563 contact the Adoption Group. See the section on [Contributing to OpenJDK](
1564 #contributing-to-openjdk) for more information.
1565
1566 ## Reproducible Builds
1567
1568 Build reproducibility is the property of getting exactly the same bits out when
1569 building, every time, independent on who builds the product, or where. This is
1570 for many reasons a harder goal than it initially appears, but it is an important
1571 goal, for security reasons and others. Please see [Reproducible Builds](
1572 https://reproducible-builds.org) for more information about the background and
1573 reasons for reproducible builds.
1574
1575 Currently, it is not possible to build OpenJDK fully reproducibly, but getting
1576 there is an ongoing effort.
1577
1578 An absolute prerequisite for building reproducible is to speficy a fixed build
1579 time, since time stamps are embedded in many file formats. This is done by
1580 setting the `SOURCE_DATE_EPOCH` environment variable, which is an [industry
1581 standard]( https://reproducible-builds.org/docs/source-date-epoch/), that many
1582 tools, such as gcc, recognize, and use in place of the current time when
1583 generating output.
1584
1585 To generate reproducible builds, you must set `SOURCE_DATE_EPOCH` before running
1586 `configure`. The value in `SOURCE_DATE_EPOCH` will be stored in the
1587 configuration, and used by `make`. Setting `SOURCE_DATE_EPOCH` before running
1588 `make` will have no effect on the build.
1589
1590 You must also make sure your build does not rely on `configure`'s default adhoc
1591 version strings. Default adhoc version strings `OPT` segment include user name
1592 and source directory. You can either override just the `OPT` segment using
1593 `--with-version-opt=<any fixed string>`, or you can specify the entire version
1594 string using `--with-version-string=<your version>`.
1595
1596 This is a typical example of how to build the JDK in a reproducible way:
1597
1598 ```
1599 export SOURCE_DATE_EPOCH=946684800
1600 bash configure --with-version-opt=adhoc
1601 make
1602 ```
1603
1604 Note that regardless if you specify a source date for `configure` or not, the
1605 JDK build system will set `SOURCE_DATE_EPOCH` for all build tools when building.
1606 If `--with-source-date` has the value `current` (which is the default unless
1607 `SOURCE_DATE_EPOCH` is found by in the environment by `configure`), the source
1608 date value will be determined at configure time.
1609
1610 There are several aspects of reproducible builds that can be individually
1611 adjusted by `configure` arguments. If any of these are given, they will override
1612 the value derived from `SOURCE_DATE_EPOCH`. These arguments are:
1613
1614 * `--with-source-date`
1615
1616 This option controls how the JDK build sets `SOURCE_DATE_EPOCH` when
1617 building. It can be set to a value describing a date, either an epoch based
1618 timestamp as an integer, or a valid ISO-8601 date.
1619
1620 It can also be set to one of the special values `current`, `updated` or
1621 `version`. `current` means that the time of running `configure` will be
1622 used. `version` will use the nominal release date for the current JDK
1623 version. `updated`, which means that `SOURCE_DATE_EPOCH` will be set to the
1624 current time each time you are running `make`. All choices, except for
1625 `updated`, will set a fixed value for the source date timestamp.
1626
1627 When `SOURCE_DATE_EPOCH` is set, the default value for `--with-source-date`
1628 will be the value given by `SOURCE_DATE_EPOCH`. Otherwise, the default value
1629 is `current`.
1630
1631 * `--with-hotspot-build-time`
1632
1633 This option controls the build time string that will be included in the
1634 hotspot library (`libjvm.so` or `jvm.dll`). When the source date is fixed
1635 (e.g. by setting `SOURCE_DATE_EPOCH`), the default value for
1636 `--with-hotspot-build-time` will be an ISO 8601 representation of that time
1637 stamp. Otherwise the default value will be the current time when building
1638 hotspot.
1639
1640 * `--with-copyright-year`
1641
1642 This option controls the copyright year in some generated text files. When
1643 the source date is fixed (e.g. by setting `SOURCE_DATE_EPOCH`), the default
1644 value for `--with-copyright-year` will be the year of that time stamp.
1645 Otherwise the default is the current year at the time of running configure.
1646 This can be overridden by `--with-copyright-year=<year>`.
1647
1648 * `--enable-reproducible-build`
1649
1650 This option controls some additional behavior needed to make the build
1651 reproducible. When the source date is fixed (e.g. by setting
1652 `SOURCE_DATE_EPOCH`), this flag will be turned on by default. Otherwise, the
1653 value is determined by heuristics. If it is explicitly turned off, the build
1654 might not be reproducible.
1655
1656 ## Hints and Suggestions for Advanced Users
1657
1658 ### Bash Completion
1659
1660 The `configure` and `make` commands tries to play nice with bash command-line
1661 completion (using `<tab>` or `<tab><tab>`). To use this functionality, make
1662 sure you enable completion in your `~/.bashrc` (see instructions for bash in
1663 your operating system).
1664
1665 Make completion will work out of the box, and will complete valid make targets.
1666 For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`.
1667
1668 The `configure` script can get completion for options, but for this to work you
1669 need to help `bash` on the way. The standard way of running the script, `bash
1670 configure`, will not be understood by bash completion. You need `configure` to
1671 be the command to run. One way to achieve this is to add a simple helper script
1672 to your path:
1673
1674 ```
1675 cat << EOT > /tmp/configure
1676 #!/bin/bash
1677 if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then
1678 echo >&2 "Abort: Trying to call configure helper recursively"
1679 exit 1
1680 fi
1681
1682 bash \$PWD/configure "\$@"
1683 EOT
1684 chmod +x /tmp/configure
1685 sudo mv /tmp/configure /usr/local/bin
1686 ```
1687
1688 Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`.
1689
1690 ### Using Multiple Configurations
1691
1692 You can have multiple configurations for a single source repository. When you
1693 create a new configuration, run `configure --with-conf-name=<name>` to create a
1694 configuration with the name `<name>`. Alternatively, you can create a directory
1695 under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd
1696 build/<name> && bash ../../configure`.
1697
1698 Then you can build that configuration using `make CONF_NAME=<name>` or `make
1699 CONF=<pattern>`, where `<pattern>` is a substring matching one or several
1700 configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will
1701 match *all* available configuration, so `make CONF= hotspot` will build the
1702 `hotspot` target for all configurations. Alternatively, you can execute `make`
1703 in the configuration directory, e.g. `cd build/<name> && make`.
1704
1705 ### Handling Reconfigurations
1706
1707 If you update the repository and part of the configure script has changed, the
1708 build system will force you to re-run `configure`.
1709
1710 Most of the time, you will be fine by running `configure` again with the same
1711 arguments as the last time, which can easily be performed by `make
1712 reconfigure`. To simplify this, you can use the `CONF_CHECK` make control
1713 variable, either as `make CONF_CHECK=auto`, or by setting an environment
1714 variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc`
1715 file, `make` will always run `reconfigure` automatically whenever the configure
1716 script has changed.
1717
1718 You can also use `CONF_CHECK=ignore` to skip the check for a needed configure
1719 update. This might speed up the build, but comes at the risk of an incorrect
1720 build result. This is only recommended if you know what you're doing.
1721
1722 From time to time, you will also need to modify the command line to `configure`
1723 due to changes. Use `make print-configuration` to show the command line used
1724 for your current configuration.
1725
1726 ### Using Fine-Grained Make Targets
1727
1728 The default behavior for make is to create consistent and correct output, at
1729 the expense of build speed, if necessary.
1730
1731 If you are prepared to take some risk of an incorrect build, and know enough of
1732 the system to understand how things build and interact, you can speed up the
1733 build process considerably by instructing make to only build a portion of the
1734 product.
1735
1736 #### Building Individual Modules
1737
1738 The safe way to use fine-grained make targets is to use the module specific
1739 make targets. All source code in the JDK is organized so it belongs to a
1740 module, e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific
1741 module, by giving it as make target: `make jdk.jdwp.agent`. If the specified
1742 module depends on other modules (e.g. `java.base`), those modules will be built
1743 first.
1744
1745 You can also specify a set of modules, just as you can always specify a set of
1746 make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi`
1747
1748 #### Building Individual Module Phases
1749
1750 The build process for each module is divided into separate phases. Not all
1751 modules need all phases. Which are needed depends on what kind of source code
1752 and other artifact the module consists of. The phases are:
1753
1754 * `gensrc` (Generate source code to compile)
1755 * `gendata` (Generate non-source code artifacts)
1756 * `copy` (Copy resource artifacts)
1757 * `java` (Compile Java code)
1758 * `launchers` (Compile native executables)
1759 * `libs` (Compile native libraries)
1760
1761 You can build only a single phase for a module by using the notation
1762 `$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`,
1763 use `make java.base-gensrc`.
1764
1765 Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if
1766 present). Make will build all needed prerequisites before building the
1767 requested phase.
1768
1769 #### Skipping the Dependency Check
1770
1771 When using an iterative development style with frequent quick rebuilds, the
1772 dependency check made by make can take up a significant portion of the time
1773 spent on the rebuild. In such cases, it can be useful to bypass the dependency
1774 check in make.
1775
1776 > **Note that if used incorrectly, this can lead to a broken build!**
1777
1778 To achieve this, append `-only` to the build target. For instance, `make
1779 jdk.jdwp.agent-java-only` will *only* build the `java` phase of the
1780 `jdk.jdwp.agent` module. If the required dependencies are not present, the
1781 build can fail. On the other hand, the execution time measures in milliseconds.
1782
1783 A useful pattern is to build the first time normally (e.g. `make
1784 jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target.
1785
1786 #### Rebuilding Part of java.base (JDK\_FILTER)
1787
1788 If you are modifying files in `java.base`, which is the by far largest module
1789 in the JDK, then you need to rebuild all those files whenever a single file has
1790 changed. (This inefficiency will hopefully be addressed in JDK 10.)
1791
1792 As a hack, you can use the make control variable `JDK_FILTER` to specify a
1793 pattern that will be used to limit the set of files being recompiled. For
1794 instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods,
1795 `make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation
1796 to files in the `javax.crypto` package.
1797
1798 ## Understanding the Build System
1799
1800 This section will give you a more technical description on the details of the
1801 build system.
1802
1803 ### Configurations
1804
1805 The build system expects to find one or more configuration. These are
1806 technically defined by the `spec.gmk` in a subdirectory to the `build`
1807 subdirectory. The `spec.gmk` file is generated by `configure`, and contains in
1808 principle the configuration (directly or by files included by `spec.gmk`).
1809
1810 You can, in fact, select a configuration to build by pointing to the `spec.gmk`
1811 file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`.
1812 While this is not the recommended way to call `make` as a user, it is what is
1813 used under the hood by the build system.
1814
1815 ### Build Output Structure
1816
1817 The build output for a configuration will end up in `build/<configuration
1818 name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory
1819 contains the following important directories:
1820
1821 ```
1822 buildtools/
1823 configure-support/
1824 hotspot/
1825 images/
1826 jdk/
1827 make-support/
1828 support/
1829 test-results/
1830 test-support/
1831 ```
1832
1833 This is what they are used for:
1834
1835 * `images`: This is the directory were the output of the `*-image` make
1836 targets end up. For instance, `make jdk-image` ends up in `images/jdk`.
1837
1838 * `jdk`: This is the "exploded image". After `make jdk`, you will be able to
1839 launch the newly built JDK by running `$BUILD/jdk/bin/java`.
1840
1841 * `test-results`: This directory contains the results from running tests.
1842
1843 * `support`: This is an area for intermediate files needed during the build,
1844 e.g. generated source code, object files and class files. Some noteworthy
1845 directories in `support` is `gensrc`, which contains the generated source
1846 code, and the `modules_*` directories, which contains the files in a
1847 per-module hierarchy that will later be collapsed into the `jdk` directory
1848 of the exploded image.
1849
1850 * `buildtools`: This is an area for tools compiled for the build platform
1851 that are used during the rest of the build.
1852
1853 * `hotspot`: This is an area for intermediate files needed when building
1854 hotspot.
1855
1856 * `configure-support`, `make-support` and `test-support`: These directories
1857 contain files that are needed by the build system for `configure`, `make`
1858 and for running tests.
1859
1860 ### Fixpath
1861
1862 Windows path typically look like `C:\User\foo`, while Unix paths look like
1863 `/home/foo`. Tools with roots from Unix often experience issues related to this
1864 mismatch when running on Windows.
1865
1866 In the JDK build, we always use Unix paths internally, and only just before
1867 calling a tool that does not understand Unix paths do we convert them to
1868 Windows paths.
1869
1870 This conversion is done by the `fixpath` tool, which is a small wrapper that
1871 modifies unix-style paths to Windows-style paths in command lines. Fixpath is
1872 compiled automatically by `configure`.
1873
1874 ### Native Debug Symbols
1875
1876 Native libraries and executables can have debug symbol (and other debug
1877 information) associated with them. How this works is very much platform
1878 dependent, but a common problem is that debug symbol information takes a lot of
1879 disk space, but is rarely needed by the end user.
1880
1881 The JDK supports different methods on how to handle debug symbols. The
1882 method used is selected by `--with-native-debug-symbols`, and available methods
1883 are `none`, `internal`, `external`, `zipped`.
1884
1885 * `none` means that no debug symbols will be generated during the build.
1886
1887 * `internal` means that debug symbols will be generated during the build, and
1888 they will be stored in the generated binary.
1889
1890 * `external` means that debug symbols will be generated during the build, and
1891 after the compilation, they will be moved into a separate `.debuginfo` file.
1892 (This was previously known as FDS, Full Debug Symbols).
1893
1894 * `zipped` is like `external`, but the .debuginfo file will also be zipped
1895 into a `.diz` file.
1896
1897 When building for distribution, `zipped` is a good solution. Binaries built
1898 with `internal` is suitable for use by developers, since they facilitate
1899 debugging, but should be stripped before distributed to end users.
1900
1901 ### Autoconf Details
1902
1903 The `configure` script is based on the autoconf framework, but in some details
1904 deviate from a normal autoconf `configure` script.
1905
1906 The `configure` script in the top level directory of the JDK is just a thin
1907 wrapper that calls `make/autoconf/configure`. This in turn will run `autoconf`
1908 to create the runnable (generated) configure script, as
1909 `.build/generated-configure.sh`. Apart from being responsible for the
1910 generation of the runnable script, the `configure` script also provides
1911 functionality that is not easily expressed in the normal Autoconf framework. As
1912 part of this functionality, the generated script is called.
1913
1914 The build system will detect if the Autoconf source files have changed, and
1915 will trigger a regeneration of the generated script if needed. You can also
1916 manually request such an update by `bash configure autogen`.
1917
1918 In previous versions of the JDK, the generated script was checked in at
1919 `make/autoconf/generated-configure.sh`. This is no longer the case.
1920
1921 ### Developing the Build System Itself
1922
1923 This section contains a few remarks about how to develop for the build system
1924 itself. It is not relevant if you are only making changes in the product source
1925 code.
1926
1927 While technically using `make`, the make source files of the JDK does not
1928 resemble most other Makefiles. Instead of listing specific targets and actions
1929 (perhaps using patterns), the basic modus operandi is to call a high-level
1930 function (or properly, macro) from the API in `make/common`. For instance, to
1931 compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module,
1932 a call like this would be made:
1933
1934 ```
1935 $(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \
1936 SETUP := GENERATE_OLDBYTECODE, \
1937 SRC := $(TOPDIR)/src/jkd.foo/share/classes, \
1938 INCLUDES := jdk/internal/foo, \
1939 BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \
1940 ))
1941 ```
1942
1943 By encapsulating and expressing the high-level knowledge of *what* should be
1944 done, rather than *how* it should be done (as is normal in Makefiles), we can
1945 build a much more powerful and flexible build system.
1946
1947 Correct dependency tracking is paramount. Sloppy dependency tracking will lead
1948 to improper parallelization, or worse, race conditions.
1949
1950 To test for/debug race conditions, try running `make JOBS=1` and `make
1951 JOBS=100` and see if it makes any difference. (It shouldn't).
1952
1953 To compare the output of two different builds and see if, and how, they differ,
1954 run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two
1955 builds you want to compare.
1956
1957 To automatically build two consecutive versions and compare them, use
1958 `COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value
1959 assignments, like this:
1960 ```
1961 make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot
1962 ```
1963 See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`.
1964
1965 To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`.
1966 Use `JOBS=1` to avoid parallelism.
1967
1968 Please check that you adhere to the [Code Conventions for the Build System](
1969 http://openjdk.org/groups/build/doc/code-conventions.html) before
1970 submitting patches.
1971
1972 ## Contributing to the JDK
1973
1974 So, now you've built your JDK, and made your first patch, and want to
1975 contribute it back to the OpenJDK Community.
1976
1977 First of all: Thank you! We gladly welcome your contribution.
1978 However, please bear in mind that the JDK is a massive project, and we must ask
1979 you to follow our rules and guidelines to be able to accept your contribution.
1980
1981 The official place to start is the ['How to contribute' page](
1982 http://openjdk.org/contribute/). There is also an official (but somewhat
1983 outdated and skimpy on details) [Developer's Guide](
1984 http://openjdk.org/guide/).
1985
1986 If this seems overwhelming to you, the Adoption Group is there to help you! A
1987 good place to start is their ['New Contributor' page](
1988 https://wiki.openjdk.org/display/Adoption/New+Contributor), or start
1989 reading the comprehensive [Getting Started Kit](
1990 https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The
1991 Adoption Group will also happily answer any questions you have about
1992 contributing. Contact them by [mail](
1993 http://mail.openjdk.org/mailman/listinfo/adoption-discuss) or [IRC](
1994 http://openjdk.org/irc/).
1995
1996 ## Editing this document
1997
1998 If you want to contribute changes to this document, edit `doc/building.md` and
1999 then run `make update-build-docs` to generate the same changes in
2000 `doc/building.html`.
2001
2002 ---
2003 # Override styles from the base CSS file that are not ideal for this document.
2004 header-includes:
2005 - '<style type="text/css">pre, code, tt { color: #1d6ae5; }</style>'
2006 ---