1 % Building the JDK
2
3 ## TL;DR (Instructions for the Impatient)
4
5 If you are eager to try out building the JDK, these simple steps works most of
6 the time. They assume that you have installed Mercurial (and Cygwin if running
7 on Windows) and cloned the top-level JDK repository that you want to build.
8
9 1. [Get the complete source code](#getting-the-source-code): \
10 `hg clone http://hg.openjdk.java.net/jdk/jdk`
11
12 2. [Run configure](#running-configure): \
13 `bash configure`
14
15 If `configure` fails due to missing dependencies (to either the
16 [toolchain](#native-compiler-toolchain-requirements), [build tools](
17 #build-tools-requirements), [external libraries](
18 #external-library-requirements) or the [boot JDK](#boot-jdk-requirements)),
19 most of the time it prints a suggestion on how to resolve the situation on
20 your platform. Follow the instructions, and try running `bash configure`
21 again.
22
23 3. [Run make](#running-make): \
24 `make images`
25
26 4. Verify your newly built JDK: \
27 `./build/*/images/jdk/bin/java -version`
28
29 5. [Run basic tests](##running-tests): \
30 `make run-test-tier1`
31
32 If any of these steps failed, or if you want to know more about build
33 requirements or build functionality, please continue reading this document.
34
35 ## Introduction
36
37 The JDK is a complex software project. Building it requires a certain amount of
38 technical expertise, a fair number of dependencies on external software, and
39 reasonably powerful hardware.
40
41 If you just want to use the JDK and not build it yourself, this document is not
42 for you. See for instance [OpenJDK installation](
43 http://openjdk.java.net/install) for some methods of installing a prebuilt
44 JDK.
45
46 ## Getting the Source Code
47
48 Make sure you are getting the correct version. As of JDK 10, the source is no
49 longer split into separate repositories so you only need to clone one single
50 repository. At the [OpenJDK Mercurial server](http://hg.openjdk.java.net/) you
51 can see a list of all available repositories. If you want to build an older version,
52 e.g. JDK 8, it is recommended that you get the `jdk8u` forest, which contains
53 incremental updates, instead of the `jdk8` forest, which was frozen at JDK 8 GA.
54
55 If you are new to Mercurial, a good place to start is the [Mercurial Beginner's
56 Guide](http://www.mercurial-scm.org/guide). The rest of this document assumes a
57 working knowledge of Mercurial.
58
59 ### Special Considerations
60
61 For a smooth building experience, it is recommended that you follow these rules
62 on where and how to check out the source code.
63
64 * Do not check out the source code in a path which contains spaces. Chances
65 are the build will not work. This is most likely to be an issue on Windows
66 systems.
67
68 * Do not check out the source code in a path which has a very long name or is
69 nested many levels deep. Chances are you will hit an OS limitation during
70 the build.
71
72 * Put the source code on a local disk, not a network share. If possible, use
73 an SSD. The build process is very disk intensive, and having slow disk
74 access will significantly increase build times. If you need to use a
75 network share for the source code, see below for suggestions on how to keep
76 the build artifacts on a local disk.
77
78 * On Windows, 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 * Clone the JDK repository using the Cygwin command line `hg` client
93 as instructed in this document. That is, do *not* use another Mercurial
94 client such as TortoiseHg.
95
96 Failure to follow this procedure might result in hard-to-debug build
97 problems.
98
99 ## Build Hardware Requirements
100
101 The JDK is a massive project, and require machines ranging from decent to
102 powerful to be able to build in a reasonable amount of time, or to be able to
103 complete a build at all.
104
105 We *strongly* recommend usage of an SSD disk for the build, since disk speed is
106 one of the limiting factors for build performance.
107
108 ### Building on x86
109
110 At a minimum, a machine with 2-4 cores is advisable, as well as 2-4 GB of RAM.
111 (The more cores to use, the more memory you need.) At least 6 GB of free disk
112 space is required (8 GB minimum for building on Solaris).
113
114 Even for 32-bit builds, it is recommended to use a 64-bit build machine, and
115 instead create a 32-bit target using `--with-target-bits=32`.
116
117 ### Building on sparc
118
119 At a minimum, a machine with 4 cores is advisable, as well as 4 GB of RAM. (The
120 more cores to use, the more memory you need.) At least 8 GB of free disk space
121 is required.
122
123 ### Building on aarch64
124
125 At a minimum, a machine with 8 cores is advisable, as well as 8 GB of RAM.
126 (The more cores to use, the more memory you need.) At least 6 GB of free disk
127 space is required.
128
129 If you do not have access to sufficiently powerful hardware, it is also
130 possible to use [cross-compiling](#cross-compiling).
131
132 ### Building on 32-bit arm
133
134 This is not recommended. Instead, see the section on [Cross-compiling](
135 #cross-compiling).
136
137 ## Operating System Requirements
138
139 The mainline JDK project supports Linux, Solaris, macOS, AIX and Windows.
140 Support for other operating system, e.g. BSD, exists in separate "port"
141 projects.
142
143 In general, the JDK can be built on a wide range of versions of these operating
144 systems, but the further you deviate from what is tested on a daily basis, the
145 more likely you are to run into problems.
146
147 This table lists the OS versions used by Oracle when building the JDK. Such
148 information is always subject to change, but this table is up to date at the
149 time of writing.
150
151 Operating system Vendor/version used
152 ----------------- -------------------------------------------------------
153 Linux Oracle Enterprise Linux 6.4 / 7.1 (using kernel 3.8.13)
154 Solaris Solaris 11.1 SRU 21.4.1 / 11.2 SRU 5.5
155 macOS Mac OS X 10.9 (Mavericks) / 10.10 (Yosemite)
156 Windows Windows Server 2012 R2
157
158 The double version numbers for Linux, Solaris and macOS is due to the hybrid
159 model used at Oracle, where header files and external libraries from an older
160 version are used when building on a more modern version of the OS.
161
162 The Build Group has a wiki page with [Supported Build Platforms](
163 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms). From
164 time to time, this is updated by contributors to list successes or failures of
165 building on different platforms.
166
167 ### Windows
168
169 Windows XP is not a supported platform, but all newer Windows should be able to
170 build the JDK.
171
172 On Windows, it is important that you pay attention to the instructions in the
173 [Special Considerations](#special-considerations).
174
175 Windows is the only non-POSIX OS supported by the JDK, and as such, requires
176 some extra care. A POSIX support layer is required to build on Windows.
177 Currently, the only supported such layers are Cygwin and Windows Subsystem for
178 Linux (WSL). (Msys is no longer supported due to a too old bash; msys2 would
179 likely be possible to support in a future version but that would require effort
180 to implement.)
181
182 Internally in the build system, all paths are represented as Unix-style paths,
183 e.g. `/cygdrive/c/hg/jdk9/Makefile` rather than `C:\hg\jdk9\Makefile`. This
184 rule also applies to input to the build system, e.g. in arguments to
185 `configure`. So, use `--with-msvcr-dll=/cygdrive/c/msvcr100.dll` rather than
186 `--with-msvcr-dll=c:\msvcr100.dll`. For details on this conversion, see the section
187 on [Fixpath](#fixpath).
188
189 #### Cygwin
190
191 A functioning [Cygwin](http://www.cygwin.com/) environment is required for
192 building the JDK on Windows. If you have a 64-bit OS, we strongly recommend
193 using the 64-bit version of Cygwin.
194
195 **Note:** Cygwin has a model of continuously updating all packages without any
196 easy way to install or revert to a specific version of a package. This means
197 that whenever you add or update a package in Cygwin, you might (inadvertently)
198 update tools that are used by the JDK build process, and that can cause
199 unexpected build problems.
200
201 The JDK requires GNU Make 4.0 or greater in Cygwin. This is usually not a
202 problem, since Cygwin currently only distributes GNU Make at a version above
203 4.0.
204
205 Apart from the basic Cygwin installation, the following packages must also be
206 installed:
207
208 * `autoconf`
209 * `make`
210 * `zip`
211 * `unzip`
212
213 Often, you can install these packages using the following command line:
214 ```
215 <path to Cygwin setup>/setup-x86_64 -q -P autoconf -P make -P unzip -P zip
216 ```
217
218 Unfortunately, Cygwin can be unreliable in certain circumstances. If you
219 experience build tool crashes or strange issues when building on Windows,
220 please check the Cygwin FAQ on the ["BLODA" list](
221 https://cygwin.com/faq/faq.html#faq.using.bloda) and the section on [fork()
222 failures](https://cygwin.com/faq/faq.html#faq.using.fixing-fork-failures).
223
224 #### Windows Subsystem for Linux (WSL)
225
226 Windows 10 1809 or newer is supported due to a dependency on the wslpath utility
227 and support for environment variable sharing through WSLENV. Version 1803 can
228 work but intermittent build failures have been observed.
229
230 It's possible to build both Windows and Linux binaries from WSL. To build
231 Windows binaries, you must use a Windows boot JDK (located in a
232 Windows-accessible directory). To build Linux binaries, you must use a Linux
233 boot JDK. The default behavior is to build for Windows. To build for Linux, pass
234 `--build=x86_64-unknown-linux-gnu --host=x86_64-unknown-linux-gnu` to
235 `configure`.
236
237 If building Windows binaries, the source code must be located in a Windows-
238 accessible directory. This is because Windows executables (such as Visual Studio
239 and the boot JDK) must be able to access the source code. Also, the drive where
240 the source is stored must be mounted as case-insensitive by changing either
241 /etc/fstab or /etc/wsl.conf in WSL. Individual directories may be corrected
242 using the fsutil tool in case the source was cloned before changing the mount
243 options.
244
245 Note that while it's possible to build on WSL, testing is still not fully
246 supported.
247
248 ### Solaris
249
250 See `make/devkit/solaris11.1-package-list.txt` for a list of recommended
251 packages to install when building on Solaris. The versions specified in this
252 list is the versions used by the daily builds at Oracle, and is likely to work
253 properly.
254
255 Older versions of Solaris shipped a broken version of `objcopy`. At least
256 version 2.21.1 is needed, which is provided by Solaris 11 Update 1. Objcopy is
257 needed if you want to have external debug symbols. Please make sure you are
258 using at least version 2.21.1 of objcopy, or that you disable external debug
259 symbols.
260
261 ### macOS
262
263 Apple is using a quite aggressive scheme of pushing OS updates, and coupling
264 these updates with required updates of Xcode. Unfortunately, this makes it
265 difficult for a project such as the JDK to keep pace with a continuously updated
266 machine running macOS. See the section on [Apple Xcode](#apple-xcode) on some
267 strategies to deal with this.
268
269 It is recommended that you use at least Mac OS X 10.13 (High Sierra). At the time
270 of writing, the JDK has been successfully compiled on macOS 10.12 (Sierra).
271
272 The standard macOS environment contains the basic tooling needed to build, but
273 for external libraries a package manager is recommended. The JDK uses
274 [homebrew](https://brew.sh/) in the examples, but feel free to use whatever
275 manager you want (or none).
276
277 ### Linux
278
279 It is often not much problem to build the JDK on Linux. The only general advice
280 is to try to use the compilers, external libraries and header files as provided
281 by your distribution.
282
283 The basic tooling is provided as part of the core operating system, but you
284 will most likely need to install developer packages.
285
286 For apt-based distributions (Debian, Ubuntu, etc), try this:
287 ```
288 sudo apt-get install build-essential
289 ```
290
291 For rpm-based distributions (Fedora, Red Hat, etc), try this:
292 ```
293 sudo yum groupinstall "Development Tools"
294 ```
295
296 ### AIX
297
298 Please consult the AIX section of the [Supported Build Platforms](
299 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms) OpenJDK
300 Build Wiki page for details about which versions of AIX are supported.
301
302 ## Native Compiler (Toolchain) Requirements
303
304 Large portions of the JDK consists of native code, that needs to be compiled to
305 be able to run on the target platform. In theory, toolchain and operating
306 system should be independent factors, but in practice there's more or less a
307 one-to-one correlation between target operating system and toolchain.
308
309 Operating system Supported toolchain
310 ------------------ -------------------------
311 Linux gcc, clang
312 macOS Apple Xcode (using clang)
313 Solaris Oracle Solaris Studio
314 AIX IBM XL C/C++
315 Windows Microsoft Visual Studio
316
317 Please see the individual sections on the toolchains for version
318 recommendations. As a reference, these versions of the toolchains are used, at
319 the time of writing, by Oracle for the daily builds of the JDK. It should be
320 possible to compile the JDK with both older and newer versions, but the closer
321 you stay to this list, the more likely you are to compile successfully without
322 issues.
323
324 Operating system Toolchain version
325 ------------------ -------------------------------------------------------
326 Linux gcc 7.3.0
327 macOS Apple Xcode 9.4 (using clang 9.1.0)
328 Solaris Oracle Solaris Studio 12.4 (with compiler version 5.13)
329 Windows Microsoft Visual Studio 2017 update 15.5.5
330
331 ### gcc
332
333 The minimum accepted version of gcc is 4.8. Older versions will generate a warning
334 by `configure` and are unlikely to work.
335
336 The JDK is currently known to be able to compile with at least version 7.4 of
337 gcc.
338
339 In general, any version between these two should be usable.
340
341 ### clang
342
343 The minimum accepted version of clang is 3.2. Older versions will not be
344 accepted by `configure`.
345
346 To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`.
347
348 ### Apple Xcode
349
350 The oldest supported version of Xcode is 8.
351
352 You will need the Xcode command lines developers tools to be able to build
353 the JDK. (Actually, *only* the command lines tools are needed, not the IDE.)
354 The simplest way to install these is to run:
355 ```
356 xcode-select --install
357 ```
358
359 It is advisable to keep an older version of Xcode for building the JDK when
360 updating Xcode. This [blog page](
361 http://iosdevelopertips.com/xcode/install-multiple-versions-of-xcode.html) has
362 good suggestions on managing multiple Xcode versions. To use a specific version
363 of Xcode, use `xcode-select -s` before running `configure`, or use
364 `--with-toolchain-path` to point to the version of Xcode to use, e.g.
365 `configure --with-toolchain-path=/Applications/Xcode8.app/Contents/Developer/usr/bin`
366
367 If you have recently (inadvertently) updated your OS and/or Xcode version, and
368 the JDK can no longer be built, please see the section on [Problems with the
369 Build Environment](#problems-with-the-build-environment), and [Getting
370 Help](#getting-help) to find out if there are any recent, non-merged patches
371 available for this update.
372
373 ### Oracle Solaris Studio
374
375 The minimum accepted version of the Solaris Studio compilers is 5.13
376 (corresponding to Solaris Studio 12.4). Older versions will not be accepted by
377 configure.
378
379 The Solaris Studio installation should contain at least these packages:
380
381 Package Version
382 -------------------------------------------------- -------------
383 developer/solarisstudio-124/backend 12.4-1.0.6.0
384 developer/solarisstudio-124/c++ 12.4-1.0.10.0
385 developer/solarisstudio-124/cc 12.4-1.0.4.0
386 developer/solarisstudio-124/library/c++-libs 12.4-1.0.10.0
387 developer/solarisstudio-124/library/math-libs 12.4-1.0.0.1
388 developer/solarisstudio-124/library/studio-gccrt 12.4-1.0.0.1
389 developer/solarisstudio-124/studio-common 12.4-1.0.0.1
390 developer/solarisstudio-124/studio-ja 12.4-1.0.0.1
391 developer/solarisstudio-124/studio-legal 12.4-1.0.0.1
392 developer/solarisstudio-124/studio-zhCN 12.4-1.0.0.1
393
394 Compiling with Solaris Studio can sometimes be finicky. This is the exact
395 version used by Oracle, which worked correctly at the time of writing:
396 ```
397 $ cc -V
398 cc: Sun C 5.13 SunOS_i386 2014/10/20
399 $ CC -V
400 CC: Sun C++ 5.13 SunOS_i386 151846-10 2015/10/30
401 ```
402
403 ### Microsoft Visual Studio
404
405 The minimum accepted version of Visual Studio is 2010. Older versions will not
406 be accepted by `configure`. The maximum accepted version of Visual Studio is
407 2017. Versions older than 2017 are unlikely to continue working for long.
408
409 If you have multiple versions of Visual Studio installed, `configure` will by
410 default pick the latest. You can request a specific version to be used by
411 setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2015`.
412
413 If you get `LINK: fatal error LNK1123: failure during conversion to COFF: file
414 invalid` when building using Visual Studio 2010, you have encountered
415 [KB2757355](http://support.microsoft.com/kb/2757355), a bug triggered by a
416 specific installation order. However, the solution suggested by the KB article
417 does not always resolve the problem. See [this stackoverflow discussion](
418 https://stackoverflow.com/questions/10888391) for other suggestions.
419
420 ### IBM XL C/C++
421
422 Please consult the AIX section of the [Supported Build Platforms](
423 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms) OpenJDK
424 Build Wiki page for details about which versions of XLC are supported.
425
426
427 ## Boot JDK Requirements
428
429 Paradoxically, building the JDK requires a pre-existing JDK. This is called the
430 "boot JDK". The boot JDK does not, however, have to be a JDK built directly from
431 the source code available in the OpenJDK Community. If you are porting the JDK
432 to a new platform, chances are that there already exists another JDK for that
433 platform that is usable as boot JDK.
434
435 The rule of thumb is that the boot JDK for building JDK major version *N*
436 should be a JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be
437 suitable as boot JDK. However, the JDK should be able to "build itself", so an
438 up-to-date build of the current JDK source is an acceptable alternative. If
439 you are following the *N-1* rule, make sure you've got the latest update
440 version, since JDK 8 GA might not be able to build JDK 9 on all platforms.
441
442 Early in the release cycle, version *N-1* may not yet have been released. In
443 that case, the preferred boot JDK will be version *N-2* until version *N-1*
444 is available.
445
446 If the boot JDK is not automatically detected, or the wrong JDK is picked, use
447 `--with-boot-jdk` to point to the JDK to use.
448
449 ### Getting JDK binaries
450
451 JDK binaries for Linux, Windows and macOS can be downloaded from
452 [jdk.java.net](http://jdk.java.net). An alternative is to download the
453 [Oracle JDK](http://www.oracle.com/technetwork/java/javase/downloads). Another
454 is the [Adopt OpenJDK Project](https://adoptopenjdk.net/), which publishes
455 experimental prebuilt binaries for various platforms.
456
457 On Linux you can also get a JDK from the Linux distribution. On apt-based
458 distros (like Debian and Ubuntu), `sudo apt-get install openjdk-<VERSION>-jdk`
459 is typically enough to install a JDK \<VERSION\>. On rpm-based distros (like
460 Fedora and Red Hat), try `sudo yum install java-<VERSION>-openjdk-devel`.
461
462 ## External Library Requirements
463
464 Different platforms require different external libraries. In general, libraries
465 are not optional - that is, they are either required or not used.
466
467 If a required library is not detected by `configure`, you need to provide the
468 path to it. There are two forms of the `configure` arguments to point to an
469 external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to
470 include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise,
471 but require the include files an library files to reside in a default hierarchy
472 under this directory. In most cases, it works fine.
473
474 As a fallback, the second version allows you to point to the include directory
475 and the lib directory separately.
476
477 ### FreeType
478
479 FreeType2 from [The FreeType Project](http://www.freetype.org/) is not required
480 on any platform. The exception is on Unix-based platforms when configuring such
481 that the build artifacts will reference a system installed library,
482 rather than bundling the JDK’s own copy.
483
484 * To install on an apt-based Linux, try running `sudo apt-get install
485 libfreetype6-dev`.
486 * To install on an rpm-based Linux, try running `sudo yum install
487 freetype-devel`.
488 * To install on Solaris, try running `pkg install system/library/freetype-2`.
489
490 Use `--with-freetype-include=<path>` and `--with-freetype-lib=<path>`
491 if `configure` does not automatically locate the platform FreeType files.
492
493 ### CUPS
494
495 CUPS, [Common UNIX Printing System](http://www.cups.org) header files are
496 required on all platforms, except Windows. Often these files are provided by
497 your operating system.
498
499 * To install on an apt-based Linux, try running `sudo apt-get install
500 libcups2-dev`.
501 * To install on an rpm-based Linux, try running `sudo yum install
502 cups-devel`.
503 * To install on Solaris, try running `pkg install print/cups`.
504
505 Use `--with-cups=<path>` if `configure` does not properly locate your CUPS
506 files.
507
508 ### X11
509
510 Certain [X11](http://www.x.org/) libraries and include files are required on
511 Linux and Solaris.
512
513 * To install on an apt-based Linux, try running `sudo apt-get install
514 libx11-dev libxext-dev libxrender-dev libxrandr-dev libxtst-dev libxt-dev`.
515 * To install on an rpm-based Linux, try running `sudo yum install
516 libXtst-devel libXt-devel libXrender-devel libXrandr-devel libXi-devel`.
517 * To install on Solaris, try running `pkg install x11/header/x11-protocols
518 x11/library/libice x11/library/libpthread-stubs x11/library/libsm
519 x11/library/libx11 x11/library/libxau x11/library/libxcb
520 x11/library/libxdmcp x11/library/libxevie x11/library/libxext
521 x11/library/libxrender x11/library/libxrandr x11/library/libxscrnsaver
522 x11/library/libxtst x11/library/toolkit/libxt`.
523
524 Use `--with-x=<path>` if `configure` does not properly locate your X11 files.
525
526 ### ALSA
527
528 ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is
529 required on Linux. At least version 0.9.1 of ALSA is required.
530
531 * To install on an apt-based Linux, try running `sudo apt-get install
532 libasound2-dev`.
533 * To install on an rpm-based Linux, try running `sudo yum install
534 alsa-lib-devel`.
535
536 Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA
537 files.
538
539 ### libffi
540
541 libffi, the [Portable Foreign Function Interface Library](
542 http://sourceware.org/libffi) is required when building the Zero version of
543 Hotspot.
544
545 * To install on an apt-based Linux, try running `sudo apt-get install
546 libffi-dev`.
547 * To install on an rpm-based Linux, try running `sudo yum install
548 libffi-devel`.
549
550 Use `--with-libffi=<path>` if `configure` does not properly locate your libffi
551 files.
552
553 ## Build Tools Requirements
554
555 ### Autoconf
556
557 The JDK requires [Autoconf](http://www.gnu.org/software/autoconf) on all
558 platforms. At least version 2.69 is required.
559
560 * To install on an apt-based Linux, try running `sudo apt-get install
561 autoconf`.
562 * To install on an rpm-based Linux, try running `sudo yum install
563 autoconf`.
564 * To install on macOS, try running `brew install autoconf`.
565 * To install on Windows, try running `<path to Cygwin setup>/setup-x86_64 -q
566 -P autoconf`.
567
568 If `configure` has problems locating your installation of autoconf, you can
569 specify it using the `AUTOCONF` environment variable, like this:
570
571 ```
572 AUTOCONF=<path to autoconf> configure ...
573 ```
574
575 ### GNU Make
576
577 The JDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors
578 of make are supported.
579
580 At least version 3.81 of GNU Make must be used. For distributions supporting
581 GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful
582 functionality to handle parallel building (supported by `--with-output-sync`)
583 and speed and stability improvements.
584
585 Note that `configure` locates and verifies a properly functioning version of
586 `make` and stores the path to this `make` binary in the configuration. If you
587 start a build using `make` on the command line, you will be using the version
588 of make found first in your `PATH`, and not necessarily the one stored in the
589 configuration. This initial make will be used as "bootstrap make", and in a
590 second stage, the make located by `configure` will be called. Normally, this
591 will present no issues, but if you have a very old `make`, or a non-GNU Make
592 `make` in your path, this might cause issues.
593
594 If you want to override the default make found by `configure`, use the `MAKE`
595 configure variable, e.g. `configure MAKE=/opt/gnu/make`.
596
597 On Solaris, it is common to call the GNU version of make by using `gmake`.
598
599 ### GNU Bash
600
601 The JDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells
602 are supported.
603
604 At least version 3.2 of GNU Bash must be used.
605
606 ## Running Configure
607
608 To build the JDK, you need a "configuration", which consists of a directory
609 where to store the build output, coupled with information about the platform,
610 the specific build machine, and choices that affect how the JDK is built.
611
612 The configuration is created by the `configure` script. The basic invocation of
613 the `configure` script looks like this:
614
615 ```
616 bash configure [options]
617 ```
618
619 This will create an output directory containing the configuration and setup an
620 area for the build result. This directory typically looks like
621 `build/linux-x64-normal-server-release`, but the actual name depends on your
622 specific configuration. (It can also be set directly, see [Using Multiple
623 Configurations](#using-multiple-configurations)). This directory is referred to
624 as `$BUILD` in this documentation.
625
626 `configure` will try to figure out what system you are running on and where all
627 necessary build components are. If you have all prerequisites for building
628 installed, it should find everything. If it fails to detect any component
629 automatically, it will exit and inform you about the problem.
630
631 Some command line examples:
632
633 * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`:
634 ```
635 bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32
636 ```
637
638 * Create a debug build with the `server` JVM and DTrace enabled:
639 ```
640 bash configure --enable-debug --with-jvm-variants=server --enable-dtrace
641 ```
642
643 ### Common Configure Arguments
644
645 Here follows some of the most common and important `configure` argument.
646
647 To get up-to-date information on *all* available `configure` argument, please
648 run:
649 ```
650 bash configure --help
651 ```
652
653 (Note that this help text also include general autoconf options, like
654 `--dvidir`, that is not relevant to the JDK. To list only JDK-specific
655 features, use `bash configure --help=short` instead.)
656
657 #### Configure Arguments for Tailoring the Build
658
659 * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand
660 for `--with-debug-level=fastdebug`)
661 * `--with-debug-level=<level>` - Set the debug level, which can be `release`,
662 `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized`
663 is variant of `release` with additional Hotspot debug code.
664 * `--with-native-debug-symbols=<method>` - Specify if and how native debug
665 symbols should be built. Available methods are `none`, `internal`,
666 `external`, `zipped`. Default behavior depends on platform. See [Native
667 Debug Symbols](#native-debug-symbols) for more details.
668 * `--with-version-string=<string>` - Specify the version string this build
669 will be identified with.
670 * `--with-version-<part>=<value>` - A group of options, where `<part>` can be
671 any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use
672 these options to modify just the corresponding part of the version string
673 from the default, or the value provided by `--with-version-string`.
674 * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant
675 (or variants) of Hotspot. Valid variants are: `server`, `client`,
676 `minimal`, `core`, `zero`, `custom`. Note that not all
677 variants are possible to combine in a single build.
678 * `--with-jvm-features=<feature>[,<feature>...]` - Use the specified JVM
679 features when building Hotspot. The list of features will be enabled on top
680 of the default list. For the `custom` JVM variant, this default list is
681 empty. A complete list of available JVM features can be found using `bash
682 configure --help`.
683 * `--with-target-bits=<bits>` - Create a target binary suitable for running
684 on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build
685 platform, instead of doing a full cross-compile. (This is known as a
686 *reduced* build.)
687
688 On Linux, BSD and AIX, it is possible to override where Java by default
689 searches for runtime/JNI libraries. This can be useful in situations where
690 there is a special shared directory for system JNI libraries. This setting
691 can in turn be overriden at runtime by setting the `java.library.path` property.
692
693 * `--with-jni-libpath=<path>` - Use the specified path as a default
694 when searching for runtime libraries.
695
696 #### Configure Arguments for Native Compilation
697
698 * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources
699 * `--with-sysroot=<path>` - Use this directory as sysroot
700 * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the
701 default path when searching for all kinds of binaries
702 * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when
703 searching for toolchain binaries (compilers etc)
704 * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C
705 files
706 * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++
707 files
708 * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK
709 libraries
710
711 #### Configure Arguments for External Dependencies
712
713 * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK](
714 #boot-jdk-requirements)
715 * `--with-freetype=<path>` - Set the path to [FreeType](#freetype)
716 * `--with-cups=<path>` - Set the path to [CUPS](#cups)
717 * `--with-x=<path>` - Set the path to [X11](#x11)
718 * `--with-alsa=<path>` - Set the path to [ALSA](#alsa)
719 * `--with-libffi=<path>` - Set the path to [libffi](#libffi)
720 * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests](
721 #running-tests)
722
723 Certain third-party libraries used by the JDK (libjpeg, giflib, libpng, lcms
724 and zlib) are included in the JDK repository. The default behavior of the
725 JDK build is to use this version of these libraries, but they might be
726 replaced by an external version. To do so, specify `system` as the `<source>`
727 option in these arguments. (The default is `bundled`).
728
729 * `--with-libjpeg=<source>` - Use the specified source for libjpeg
730 * `--with-giflib=<source>` - Use the specified source for giflib
731 * `--with-libpng=<source>` - Use the specified source for libpng
732 * `--with-lcms=<source>` - Use the specified source for lcms
733 * `--with-zlib=<source>` - Use the specified source for zlib
734
735 On Linux, it is possible to select either static or dynamic linking of the C++
736 runtime. The default is static linking, with dynamic linking as fallback if the
737 static library is not found.
738
739 * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic`
740 or `default`) for linking the C++ runtime.
741
742 ### Configure Control Variables
743
744 It is possible to control certain aspects of `configure` by overriding the
745 value of `configure` variables, either on the command line or in the
746 environment.
747
748 Normally, this is **not recommended**. If used improperly, it can lead to a
749 broken configuration. Unless you're well versed in the build system, this is
750 hard to use properly. Therefore, `configure` will print a warning if this is
751 detected.
752
753 However, there are a few `configure` variables, known as *control variables*
754 that are supposed to be overriden on the command line. These are variables that
755 describe the location of tools needed by the build, like `MAKE` or `GREP`. If
756 any such variable is specified, `configure` will use that value instead of
757 trying to autodetect the tool. For instance, `bash configure
758 MAKE=/opt/gnumake4.0/bin/make`.
759
760 If a configure argument exists, use that instead, e.g. use `--with-jtreg`
761 instead of setting `JTREGEXE`.
762
763 Also note that, despite what autoconf claims, setting `CFLAGS` will not
764 accomplish anything. Instead use `--with-extra-cflags` (and similar for
765 `cxxflags` and `ldflags`).
766
767 ## Running Make
768
769 When you have a proper configuration, all you need to do to build the JDK is to
770 run `make`. (But see the warning at [GNU Make](#gnu-make) about running the
771 correct version of make.)
772
773 When running `make` without any arguments, the default target is used, which is
774 the same as running `make default` or `make jdk`. This will build a minimal (or
775 roughly minimal) set of compiled output (known as an "exploded image") needed
776 for a developer to actually execute the newly built JDK. The idea is that in an
777 incremental development fashion, when doing a normal make, you should only
778 spend time recompiling what's changed (making it purely incremental) and only
779 do the work that's needed to actually run and test your code.
780
781 The output of the exploded image resides in `$BUILD/jdk`. You can test the
782 newly built JDK like this: `$BUILD/jdk/bin/java -version`.
783
784 ### Common Make Targets
785
786 Apart from the default target, here are some common make targets:
787
788 * `hotspot` - Build all of hotspot (but only hotspot)
789 * `hotspot-<variant>` - Build just the specified jvm variant
790 * `images` or `product-images` - Build the JDK image
791 * `docs` or `docs-image` - Build the documentation image
792 * `test-image` - Build the test image
793 * `all` or `all-images` - Build all images (product, docs and test)
794 * `bootcycle-images` - Build images twice, second time with newly built JDK
795 (good for testing)
796 * `clean` - Remove all files generated by make, but not those generated by
797 configure
798 * `dist-clean` - Remove all files, including configuration
799
800 Run `make help` to get an up-to-date list of important make targets and make
801 control variables.
802
803 It is possible to build just a single module, a single phase, or a single phase
804 of a single module, by creating make targets according to these followin
805 patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`,
806 `launchers`, `libs` or `rmic`. See [Using Fine-Grained Make Targets](
807 #using-fine-grained-make-targets) for more details about this functionality.
808
809 * `<phase>` - Build the specified phase and everything it depends on
810 * `<module>` - Build the specified module and everything it depends on
811 * `<module>-<phase>` - Compile the specified phase for the specified module
812 and everything it depends on
813
814 Similarly, it is possible to clean just a part of the build by creating make
815 targets according to these patterns:
816
817 * `clean-<outputdir>` - Remove the subdir in the output dir with the name
818 * `clean-<phase>` - Remove all build results related to a certain build
819 phase
820 * `clean-<module>` - Remove all build results related to a certain module
821 * `clean-<module>-<phase>` - Remove all build results related to a certain
822 module and phase
823
824 ### Make Control Variables
825
826 It is possible to control `make` behavior by overriding the value of `make`
827 variables, either on the command line or in the environment.
828
829 Normally, this is **not recommended**. If used improperly, it can lead to a
830 broken build. Unless you're well versed in the build system, this is hard to
831 use properly. Therefore, `make` will print a warning if this is detected.
832
833 However, there are a few `make` variables, known as *control variables* that
834 are supposed to be overriden on the command line. These make up the "make time"
835 configuration, as opposed to the "configure time" configuration.
836
837 #### General Make Control Variables
838
839 * `JOBS` - Specify the number of jobs to build with. See [Build
840 Performance](#build-performance).
841 * `LOG` - Specify the logging level and functionality. See [Checking the
842 Build Log File](#checking-the-build-log-file)
843 * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using
844 Multiple Configurations](#using-multiple-configurations)
845
846 #### Test Make Control Variables
847
848 These make control variables only make sense when running tests. Please see
849 [Testing the JDK](testing.html) for details.
850
851 * `TEST`
852 * `TEST_JOBS`
853 * `JTREG`
854 * `GTEST`
855
856 #### Advanced Make Control Variables
857
858 These advanced make control variables can be potentially unsafe. See [Hints and
859 Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and
860 [Understanding the Build System](#understanding-the-build-system) for details.
861
862 * `SPEC`
863 * `CONF_CHECK`
864 * `COMPARE_BUILD`
865 * `JDK_FILTER`
866
867 ## Running Tests
868
869 Most of the JDK tests are using the [JTReg](http://openjdk.java.net/jtreg)
870 test framework. Make sure that your configuration knows where to find your
871 installation of JTReg. If this is not picked up automatically, use the
872 `--with-jtreg=<path to jtreg home>` option to point to the JTReg framework.
873 Note that this option should point to the JTReg home, i.e. the top directory,
874 containing `lib/jtreg.jar` etc.
875
876 The [Adoption Group](https://wiki.openjdk.java.net/display/Adoption) provides
877 recent builds of jtreg [here](
878 https://adopt-openjdk.ci.cloudbees.com/job/jtreg/lastSuccessfulBuild/artifact).
879 Download the latest `.tar.gz` file, unpack it, and point `--with-jtreg` to the
880 `jtreg` directory that you just unpacked.
881
882 To execute the most basic tests (tier 1), use:
883 ```
884 make run-test-tier1
885 ```
886
887 For more details on how to run tests, please see the [Testing
888 the JDK](testing.html) document.
889
890 ## Cross-compiling
891
892 Cross-compiling means using one platform (the *build* platform) to generate
893 output that can ran on another platform (the *target* platform).
894
895 The typical reason for cross-compiling is that the build is performed on a more
896 powerful desktop computer, but the resulting binaries will be able to run on a
897 different, typically low-performing system. Most of the complications that
898 arise when building for embedded is due to this separation of *build* and
899 *target* systems.
900
901 This requires a more complex setup and build procedure. This section assumes
902 you are familiar with cross-compiling in general, and will only deal with the
903 particularities of cross-compiling the JDK. If you are new to cross-compiling,
904 please see the [external links at Wikipedia](
905 https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start
906 on reading materials.
907
908 Cross-compiling the JDK requires you to be able to build both for the build
909 platform and for the target platform. The reason for the former is that we need
910 to build and execute tools during the build process, both native tools and Java
911 tools.
912
913 If all you want to do is to compile a 32-bit version, for the same OS, on a
914 64-bit machine, consider using `--with-target-bits=32` instead of doing a
915 full-blown cross-compilation. (While this surely is possible, it's a lot more
916 work and will take much longer to build.)
917
918 ### Cross compiling the easy way with OpenJDK devkits
919
920 The OpenJDK build system provides out-of-the box support for creating and using
921 so called devkits. A `devkit` is basically a collection of a cross-compiling
922 toolchain and a sysroot environment which can easily be used together with the
923 `--with-devkit` configure option to cross compile the OpenJDK. On Linux/x86_64,
924 the following command:
925 ```
926 bash configure --with-devkit=<devkit-path> --openjdk-target=ppc64-linux-gnu && make
927 ```
928
929 will configure and build OpenJDK for Linux/ppc64 assuming that `<devkit-path>`
930 points to a Linux/x86_64 to Linux/ppc64 devkit.
931
932 Devkits can be created from the `make/devkit` directory by executing:
933 ```
934 make [ TARGETS="<TARGET_TRIPLET>+" ] [ BASE_OS=<OS> ] [ BASE_OS_VERSION=<VER> ]
935 ```
936
937 where `TARGETS` contains one or more `TARGET_TRIPLET`s of the form
938 described in [section 3.4 of the GNU Autobook](
939 https://sourceware.org/autobook/autobook/autobook_17.html). If no
940 targets are given, a native toolchain for the current platform will be
941 created. Currently, at least the following targets are known to work:
942
943 Supported devkit targets
944 -------------------------
945 x86_64-linux-gnu
946 aarch64-linux-gnu
947 arm-linux-gnueabihf
948 ppc64-linux-gnu
949 ppc64le-linux-gnu
950 s390x-linux-gnu
951
952 `BASE_OS` must be one of "OEL6" for Oracle Enterprise Linux 6 or
953 "Fedora" (if not specified "OEL6" will be the default). If the base OS
954 is "Fedora" the corresponding Fedora release can be specified with the
955 help of the `BASE_OS_VERSION` option (with "27" as default version).
956 If the build is successful, the new devkits can be found in the
957 `build/devkit/result` subdirectory:
958 ```
959 cd make/devkit
960 make TARGETS="ppc64le-linux-gnu aarch64-linux-gnu" BASE_OS=Fedora BASE_OS_VERSION=21
961 ls -1 ../../build/devkit/result/
962 x86_64-linux-gnu-to-aarch64-linux-gnu
963 x86_64-linux-gnu-to-ppc64le-linux-gnu
964 ```
965
966 Notice that devkits are not only useful for targeting different build
967 platforms. Because they contain the full build dependencies for a
968 system (i.e. compiler and root file system), they can easily be used
969 to build well-known, reliable and reproducible build environments. You
970 can for example create and use a devkit with GCC 7.3 and a Fedora 12
971 sysroot environment (with glibc 2.11) on Ubuntu 14.04 (which doesn't
972 have GCC 7.3 by default) to produce OpenJDK binaries which will run on
973 all Linux systems with runtime libraries newer than the ones from
974 Fedora 12 (e.g. Ubuntu 16.04, SLES 11 or RHEL 6).
975
976 ### Boot JDK and Build JDK
977
978 When cross-compiling, make sure you use a boot JDK that runs on the *build*
979 system, and not on the *target* system.
980
981 To be able to build, we need a "Build JDK", which is a JDK built from the
982 current sources (that is, the same as the end result of the entire build
983 process), but able to run on the *build* system, and not the *target* system.
984 (In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when
985 building JDK 9.)
986
987 The build process will create a minimal Build JDK for you, as part of building.
988 To speed up the build, you can use `--with-build-jdk` to `configure` to point
989 to a pre-built Build JDK. Please note that the build result is unpredictable,
990 and can possibly break in subtle ways, if the Build JDK does not **exactly**
991 match the current sources.
992
993 ### Specifying the Target Platform
994
995 You *must* specify the target platform when cross-compiling. Doing so will also
996 automatically turn the build into a cross-compiling mode. The simplest way to
997 do this is to use the `--openjdk-target` argument, e.g.
998 `--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`.
999 This will automatically set the `--build`, `--host` and `--target` options for
1000 autoconf, which can otherwise be confusing. (In autoconf terminology, the
1001 "target" is known as "host", and "target" is used for building a Canadian
1002 cross-compiler.)
1003
1004 ### Toolchain Considerations
1005
1006 You will need two copies of your toolchain, one which generates output that can
1007 run on the target system (the normal, or *target*, toolchain), and one that
1008 generates output that can run on the build system (the *build* toolchain). Note
1009 that cross-compiling is only supported for gcc at the time being. The gcc
1010 standard is to prefix cross-compiling toolchains with the target denominator.
1011 If you follow this standard, `configure` is likely to pick up the toolchain
1012 correctly.
1013
1014 The *build* toolchain will be autodetected just the same way the normal
1015 *build*/*target* toolchain will be autodetected when not cross-compiling. If
1016 this is not what you want, or if the autodetection fails, you can specify a
1017 devkit containing the *build* toolchain using `--with-build-devkit` to
1018 `configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments.
1019
1020 It is often helpful to locate the cross-compilation tools, headers and
1021 libraries in a separate directory, outside the normal path, and point out that
1022 directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and
1023 appending the directory when searching for cross-compilations tools
1024 (`--with-toolchain-path`). As a compact form, you can also use `--with-devkit`
1025 to point to a single directory, if it is correctly setup. (See `basics.m4` for
1026 details.)
1027
1028 If you are unsure what toolchain and versions to use, these have been proved
1029 working at the time of writing:
1030
1031 * [aarch64](
1032 https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-linux-gnu-4.8-2013.11_linux.tar.xz)
1033 * [arm 32-bit hardware floating point](
1034 https://launchpad.net/linaro-toolchain-unsupported/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux.tar.bz2)
1035
1036 ### Native Libraries
1037
1038 You will need copies of external native libraries for the *target* system,
1039 present on the *build* machine while building.
1040
1041 Take care not to replace the *build* system's version of these libraries by
1042 mistake, since that can render the *build* machine unusable.
1043
1044 Make sure that the libraries you point to (ALSA, X11, etc) are for the
1045 *target*, not the *build*, platform.
1046
1047 #### ALSA
1048
1049 You will need alsa libraries suitable for your *target* system. For most cases,
1050 using Debian's pre-built libraries work fine.
1051
1052 Note that alsa is needed even if you only want to build a headless JDK.
1053
1054 * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and
1055 search for the `libasound2` and `libasound2-dev` packages for your *target*
1056 system. Download them to /tmp.
1057
1058 * Install the libraries into the cross-compilation toolchain. For instance:
1059 ```
1060 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc
1061 dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb .
1062 dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb .
1063 ```
1064
1065 * If alsa is not properly detected by `configure`, you can point it out by
1066 `--with-alsa`.
1067
1068 #### X11
1069
1070 You will need X11 libraries suitable for your *target* system. For most cases,
1071 using Debian's pre-built libraries work fine.
1072
1073 Note that X11 is needed even if you only want to build a headless JDK.
1074
1075 * Go to [Debian Package Search](https://www.debian.org/distrib/packages),
1076 search for the following packages for your *target* system, and download them
1077 to /tmp/target-x11:
1078 * libxi
1079 * libxi-dev
1080 * x11proto-core-dev
1081 * x11proto-input-dev
1082 * x11proto-kb-dev
1083 * x11proto-render-dev
1084 * x11proto-xext-dev
1085 * libice-dev
1086 * libxrender
1087 * libxrender-dev
1088 * libxrandr-dev
1089 * libsm-dev
1090 * libxt-dev
1091 * libx11
1092 * libx11-dev
1093 * libxtst
1094 * libxtst-dev
1095 * libxext
1096 * libxext-dev
1097
1098 * Install the libraries into the cross-compilation toolchain. For instance:
1099 ```
1100 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr
1101 mkdir X11R6
1102 cd X11R6
1103 for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done
1104 mv usr/* .
1105 cd lib
1106 cp arm-linux-gnueabihf/* .
1107 ```
1108
1109 You can ignore the following messages. These libraries are not needed to
1110 successfully complete a full JDK build.
1111 ```
1112 cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory
1113 cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory
1114 cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory
1115 ```
1116
1117 * If the X11 libraries are not properly detected by `configure`, you can
1118 point them out by `--with-x`.
1119
1120 ### Creating And Using Sysroots With qemu-deboostrap
1121
1122 Fortunately, you can create sysroots for foreign architectures with tools
1123 provided by your OS. On Debian/Ubuntu systems, one could use `qemu-deboostrap` to
1124 create the *target* system chroot, which would have the native libraries and headers
1125 specific to that *target* system. After that, we can use the cross-compiler on the *build*
1126 system, pointing into chroot to get the build dependencies right. This allows building
1127 for foreign architectures with native compilation speed.
1128
1129 For example, cross-compiling to AArch64 from x86_64 could be done like this:
1130
1131 * Install cross-compiler on the *build* system:
1132 ```
1133 apt install g++-aarch64-linux-gnu gcc-aarch64-linux-gnu
1134 ```
1135
1136 * Create chroot on the *build* system, configuring it for *target* system:
1137 ```
1138 sudo qemu-debootstrap --arch=arm64 --verbose \
1139 --include=fakeroot,build-essential,libx11-dev,libxext-dev,libxrender-dev,libxrandr-dev,libxtst-dev,libxt-dev,libcups2-dev,libfontconfig1-dev,libasound2-dev,libfreetype6-dev,libpng12-dev \
1140 --resolve-deps jessie /chroots/arm64 http://httpredir.debian.org/debian/
1141 ```
1142
1143 * Configure and build with newly created chroot as sysroot/toolchain-path:
1144 ```
1145 CC=aarch64-linux-gnu-gcc CXX=aarch64-linux-gnu-g++ sh ./configure --openjdk-target=aarch64-linux-gnu --with-sysroot=/chroots/arm64/ --with-toolchain-path=/chroots/arm64/
1146 make images
1147 ls build/linux-aarch64-normal-server-release/
1148 ```
1149
1150 The build does not create new files in that chroot, so it can be reused for multiple builds
1151 without additional cleanup.
1152
1153 Architectures that are known to successfully cross-compile like this are:
1154
1155 Target `CC` `CXX` `--arch=...` `--openjdk-target=...`
1156 ------------ ------------------------- --------------------------- ------------- -----------------------
1157 x86 default default i386 i386-linux-gnu
1158 armhf gcc-arm-linux-gnueabihf g++-arm-linux-gnueabihf armhf arm-linux-gnueabihf
1159 aarch64 gcc-aarch64-linux-gnu g++-aarch64-linux-gnu arm64 aarch64-linux-gnu
1160 ppc64el gcc-powerpc64le-linux-gnu g++-powerpc64le-linux-gnu ppc64el powerpc64le-linux-gnu
1161 s390x gcc-s390x-linux-gnu g++-s390x-linux-gnu s390x s390x-linux-gnu
1162
1163 Additional architectures might be supported by Debian/Ubuntu Ports.
1164
1165 ### Building for ARM/aarch64
1166
1167 A common cross-compilation target is the ARM CPU. When building for ARM, it is
1168 useful to set the ABI profile. A number of pre-defined ABI profiles are
1169 available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt,
1170 armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer
1171 properly supported by the JDK.
1172
1173 ### Verifying the Build
1174
1175 The build will end up in a directory named like
1176 `build/linux-arm-normal-server-release`.
1177
1178 Inside this build output directory, the `images/jdk` will contain the newly
1179 built JDK, for your *target* system.
1180
1181 Copy these folders to your *target* system. Then you can run e.g.
1182 `images/jdk/bin/java -version`.
1183
1184 ## Build Performance
1185
1186 Building the JDK requires a lot of horsepower. Some of the build tools can be
1187 adjusted to utilize more or less of resources such as parallel threads and
1188 memory. The `configure` script analyzes your system and selects reasonable
1189 values for such options based on your hardware. If you encounter resource
1190 problems, such as out of memory conditions, you can modify the detected values
1191 with:
1192
1193 * `--with-num-cores` -- number of cores in the build system, e.g.
1194 `--with-num-cores=8`.
1195
1196 * `--with-memory-size` -- memory (in MB) available in the build system, e.g.
1197 `--with-memory-size=1024`
1198
1199 You can also specify directly the number of build jobs to use with
1200 `--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag
1201 to `make`. In most cases it will be ignored by the makefiles, but it can cause
1202 problems for some make targets.
1203
1204 It might also be necessary to specify the JVM arguments passed to the Boot JDK,
1205 using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the
1206 default JVM arguments passed to the Boot JDK.
1207
1208 At the end of a successful execution of `configure`, you will get a performance
1209 summary, indicating how well the build will perform. Here you will also get
1210 performance hints. If you want to build fast, pay attention to those!
1211
1212 If you want to tweak build performance, run with `make LOG=info` to get a build
1213 time summary at the end of the build process.
1214
1215 ### Disk Speed
1216
1217 If you are using network shares, e.g. via NFS, for your source code, make sure
1218 the build directory is situated on local disk (e.g. by `ln -s
1219 /localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely
1220 high for building on a network share; close to unusable.
1221
1222 Also, make sure that your build tools (including Boot JDK and toolchain) is
1223 located on a local disk and not a network share.
1224
1225 As has been stressed elsewhere, do use SSD for source code and build directory,
1226 as well as (if possible) the build tools.
1227
1228 ### Virus Checking
1229
1230 The use of virus checking software, especially on Windows, can *significantly*
1231 slow down building of the JDK. If possible, turn off such software, or exclude
1232 the directory containing the JDK source code from on-the-fly checking.
1233
1234 ### Ccache
1235
1236 The JDK build supports building with ccache when using gcc or clang. Using
1237 ccache can radically speed up compilation of native code if you often rebuild
1238 the same sources. Your milage may vary however, so we recommend evaluating it
1239 for yourself. To enable it, make sure it's on the path and configure with
1240 `--enable-ccache`.
1241
1242 ### Precompiled Headers
1243
1244 By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains
1245 were it is properly supported (clang, gcc, and Visual Studio). Normally, this
1246 speeds up the build process, but in some circumstances, it can actually slow
1247 things down.
1248
1249 You can experiment by disabling precompiled headers using
1250 `--disable-precompiled-headers`.
1251
1252 ### Icecc / icecream
1253
1254 [icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a
1255 distributed compiler network. If you have multiple machines available for
1256 building the JDK, you can drastically cut individual build times by utilizing
1257 it.
1258
1259 To use, setup an icecc network, and install icecc on the build machine. Then
1260 run `configure` using `--enable-icecc`.
1261
1262 ### Using sjavac
1263
1264 To speed up Java compilation, especially incremental compilations, you can try
1265 the experimental sjavac compiler by using `--enable-sjavac`.
1266
1267 ### Building the Right Target
1268
1269 Selecting the proper target to build can have dramatic impact on build time.
1270 For normal usage, `jdk` or the default target is just fine. You only need to
1271 build `images` for shipping, or if your tests require it.
1272
1273 See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on
1274 how to build an even smaller subset of the product.
1275
1276 ## Troubleshooting
1277
1278 If your build fails, it can sometimes be difficult to pinpoint the problem or
1279 find a proper solution.
1280
1281 ### Locating the Source of the Error
1282
1283 When a build fails, it can be hard to pinpoint the actual cause of the error.
1284 In a typical build process, different parts of the product build in parallel,
1285 with the output interlaced.
1286
1287 #### Build Failure Summary
1288
1289 To help you, the build system will print a failure summary at the end. It looks
1290 like this:
1291
1292 ```
1293 ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2)
1294
1295 === Output from failing command(s) repeated here ===
1296 * For target hotspot_variant-server_libjvm_objs_psMemoryPool.o:
1297 /localhome/hg/jdk9-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type
1298 ... (rest of output omitted)
1299
1300 * All command lines available in /localhome/hg/jdk9-sandbox/build/linux-x64/make-support/failure-logs.
1301 === End of repeated output ===
1302
1303 === Make failed targets repeated here ===
1304 lib/CompileJvm.gmk:207: recipe for target '/localhome/hg/jdk9-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed
1305 make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed
1306 === End of repeated output ===
1307
1308 Hint: Try searching the build log for the name of the first failed target.
1309 Hint: If caused by a warning, try configure --disable-warnings-as-errors.
1310 ```
1311
1312 Let's break it down! First, the selected configuration, and the top-level
1313 target you entered on the command line that caused the failure is printed.
1314
1315 Then, between the `Output from failing command(s) repeated here` and `End of
1316 repeated output` the first lines of output (stdout and stderr) from the actual
1317 failing command is repeated. In most cases, this is the error message that
1318 caused the build to fail. If multiple commands were failing (this can happen in
1319 a parallel build), output from all failed commands will be printed here.
1320
1321 The path to the `failure-logs` directory is printed. In this file you will find
1322 a `<target>.log` file that contains the output from this command in its
1323 entirety, and also a `<target>.cmd`, which contain the complete command line
1324 used for running this command. You can re-run the failing command by executing
1325 `. <path to failure-logs>/<target>.cmd` in your shell.
1326
1327 Another way to trace the failure is to follow the chain of make targets, from
1328 top-level targets to individual file targets. Between `Make failed targets
1329 repeated here` and `End of repeated output` the output from make showing this
1330 chain is repeated. The first failed recipe will typically contain the full path
1331 to the file in question that failed to compile. Following lines will show a
1332 trace of make targets why we ended up trying to compile that file.
1333
1334 Finally, some hints are given on how to locate the error in the complete log.
1335 In this example, we would try searching the log file for "`psMemoryPool.o`".
1336 Another way to quickly locate make errors in the log is to search for "`]
1337 Error`" or "`***`".
1338
1339 Note that the build failure summary will only help you if the issue was a
1340 compilation failure or similar. If the problem is more esoteric, or is due to
1341 errors in the build machinery, you will likely get empty output logs, and `No
1342 indication of failed target found` instead of the make target chain.
1343
1344 #### Checking the Build Log File
1345
1346 The output (stdout and stderr) from the latest build is always stored in
1347 `$BUILD/build.log`. The previous build log is stored as `build.log.old`. This
1348 means that it is not necessary to redirect the build output yourself if you
1349 want to process it.
1350
1351 You can increase the verbosity of the log file, by the `LOG` control variable
1352 to `make`. If you want to see the command lines used in compilations, use
1353 `LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug`
1354 or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g.
1355 `LOG=info,cmdlines`. The `debug` log level will show most shell commands
1356 executed by make, and `trace` will show all. Beware that both these log levels
1357 will produce a massive build log!
1358
1359 ### Fixing Unexpected Build Failures
1360
1361 Most of the time, the build will fail due to incorrect changes in the source
1362 code.
1363
1364 Sometimes the build can fail with no apparent changes that have caused the
1365 failure. If this is the first time you are building the JDK on this particular
1366 computer, and the build fails, the problem is likely with your build
1367 environment. But even if you have previously built the JDK with success, and it
1368 now fails, your build environment might have changed (perhaps due to OS
1369 upgrades or similar). But most likely, such failures are due to problems with
1370 the incremental rebuild.
1371
1372 #### Problems with the Build Environment
1373
1374 Make sure your configuration is correct. Re-run `configure`, and look for any
1375 warnings. Warnings that appear in the middle of the `configure` output is also
1376 repeated at the end, after the summary. The entire log is stored in
1377 `$BUILD/configure.log`.
1378
1379 Verify that the summary at the end looks correct. Are you indeed using the Boot
1380 JDK and native toolchain that you expect?
1381
1382 By default, the JDK has a strict approach where warnings from the compiler is
1383 considered errors which fail the build. For very new or very old compiler
1384 versions, this can trigger new classes of warnings, which thus fails the build.
1385 Run `configure` with `--disable-warnings-as-errors` to turn of this behavior.
1386 (The warnings will still show, but not make the build fail.)
1387
1388 #### Problems with Incremental Rebuilds
1389
1390 Incremental rebuilds mean that when you modify part of the product, only the
1391 affected parts get rebuilt. While this works great in most cases, and
1392 significantly speed up the development process, from time to time complex
1393 interdependencies will result in an incorrect build result. This is the most
1394 common cause for unexpected build problems.
1395
1396 Here are a suggested list of things to try if you are having unexpected build
1397 problems. Each step requires more time than the one before, so try them in
1398 order. Most issues will be solved at step 1 or 2.
1399
1400 1. Make sure your repository is up-to-date
1401
1402 Run `hg pull -u` to make sure you have the latest changes.
1403
1404 2. Clean build results
1405
1406 The simplest way to fix incremental rebuild issues is to run `make clean`.
1407 This will remove all build results, but not the configuration or any build
1408 system support artifacts. In most cases, this will solve build errors
1409 resulting from incremental build mismatches.
1410
1411 3. Completely clean the build directory.
1412
1413 If this does not work, the next step is to run `make dist-clean`, or
1414 removing the build output directory (`$BUILD`). This will clean all
1415 generated output, including your configuration. You will need to re-run
1416 `configure` after this step. A good idea is to run `make
1417 print-configuration` before running `make dist-clean`, as this will print
1418 your current `configure` command line. Here's a way to do this:
1419
1420 ```
1421 make print-configuration > current-configuration
1422 make dist-clean
1423 bash configure $(cat current-configuration)
1424 make
1425 ```
1426
1427 4. Re-clone the Mercurial repository
1428
1429 Sometimes the Mercurial repository gets in a state that causes the product
1430 to be un-buildable. In such a case, the simplest solution is often the
1431 "sledgehammer approach": delete the entire repository, and re-clone it.
1432 If you have local changes, save them first to a different location using
1433 `hg export`.
1434
1435 ### Specific Build Issues
1436
1437 #### Clock Skew
1438
1439 If you get an error message like this:
1440 ```
1441 File 'xxx' has modification time in the future.
1442 Clock skew detected. Your build may be incomplete.
1443 ```
1444 then the clock on your build machine is out of sync with the timestamps on the
1445 source files. Other errors, apparently unrelated but in fact caused by the
1446 clock skew, can occur along with the clock skew warnings. These secondary
1447 errors may tend to obscure the fact that the true root cause of the problem is
1448 an out-of-sync clock.
1449
1450 If you see these warnings, reset the clock on the build machine, run `make
1451 clean` and restart the build.
1452
1453 #### Out of Memory Errors
1454
1455 On Solaris, you might get an error message like this:
1456 ```
1457 Trouble writing out table to disk
1458 ```
1459 To solve this, increase the amount of swap space on your build machine.
1460
1461 On Windows, you might get error messages like this:
1462 ```
1463 fatal error - couldn't allocate heap
1464 cannot create ... Permission denied
1465 spawn failed
1466 ```
1467 This can be a sign of a Cygwin problem. See the information about solving
1468 problems in the [Cygwin](#cygwin) section. Rebooting the computer might help
1469 temporarily.
1470
1471 ### Getting Help
1472
1473 If none of the suggestions in this document helps you, or if you find what you
1474 believe is a bug in the build system, please contact the Build Group by sending
1475 a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net).
1476 Please include the relevant parts of the configure and/or build log.
1477
1478 If you need general help or advice about developing for the JDK, you can also
1479 contact the Adoption Group. See the section on [Contributing to OpenJDK](
1480 #contributing-to-openjdk) for more information.
1481
1482 ## Hints and Suggestions for Advanced Users
1483
1484 ### Setting Up a Repository for Pushing Changes (defpath)
1485
1486 To help you prepare a proper push path for a Mercurial repository, there exists
1487 a useful tool known as [defpath](
1488 http://openjdk.java.net/projects/code-tools/defpath). It will help you setup a
1489 proper push path for pushing changes to the JDK.
1490
1491 Install the extension by cloning
1492 `http://hg.openjdk.java.net/code-tools/defpath` and updating your `.hgrc` file.
1493 Here's one way to do this:
1494
1495 ```
1496 cd ~
1497 mkdir hg-ext
1498 cd hg-ext
1499 hg clone http://hg.openjdk.java.net/code-tools/defpath
1500 cat << EOT >> ~/.hgrc
1501 [extensions]
1502 defpath=~/hg-ext/defpath/defpath.py
1503 EOT
1504 ```
1505
1506 You can now setup a proper push path using:
1507 ```
1508 hg defpath -d -u <your OpenJDK username>
1509 ```
1510
1511 ### Bash Completion
1512
1513 The `configure` and `make` commands tries to play nice with bash command-line
1514 completion (using `<tab>` or `<tab><tab>`). To use this functionality, make
1515 sure you enable completion in your `~/.bashrc` (see instructions for bash in
1516 your operating system).
1517
1518 Make completion will work out of the box, and will complete valid make targets.
1519 For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`.
1520
1521 The `configure` script can get completion for options, but for this to work you
1522 need to help `bash` on the way. The standard way of running the script, `bash
1523 configure`, will not be understood by bash completion. You need `configure` to
1524 be the command to run. One way to achieve this is to add a simple helper script
1525 to your path:
1526
1527 ```
1528 cat << EOT > /tmp/configure
1529 #!/bin/bash
1530 if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then
1531 echo >&2 "Abort: Trying to call configure helper recursively"
1532 exit 1
1533 fi
1534
1535 bash \$PWD/configure "\$@"
1536 EOT
1537 chmod +x /tmp/configure
1538 sudo mv /tmp/configure /usr/local/bin
1539 ```
1540
1541 Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`.
1542
1543 ### Using Multiple Configurations
1544
1545 You can have multiple configurations for a single source repository. When you
1546 create a new configuration, run `configure --with-conf-name=<name>` to create a
1547 configuration with the name `<name>`. Alternatively, you can create a directory
1548 under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd
1549 build/<name> && bash ../../configure`.
1550
1551 Then you can build that configuration using `make CONF_NAME=<name>` or `make
1552 CONF=<pattern>`, where `<pattern>` is a substring matching one or several
1553 configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will
1554 match *all* available configuration, so `make CONF= hotspot` will build the
1555 `hotspot` target for all configurations. Alternatively, you can execute `make`
1556 in the configuration directory, e.g. `cd build/<name> && make`.
1557
1558 ### Handling Reconfigurations
1559
1560 If you update the repository and part of the configure script has changed, the
1561 build system will force you to re-run `configure`.
1562
1563 Most of the time, you will be fine by running `configure` again with the same
1564 arguments as the last time, which can easily be performed by `make
1565 reconfigure`. To simplify this, you can use the `CONF_CHECK` make control
1566 variable, either as `make CONF_CHECK=auto`, or by setting an environment
1567 variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc`
1568 file, `make` will always run `reconfigure` automatically whenever the configure
1569 script has changed.
1570
1571 You can also use `CONF_CHECK=ignore` to skip the check for a needed configure
1572 update. This might speed up the build, but comes at the risk of an incorrect
1573 build result. This is only recommended if you know what you're doing.
1574
1575 From time to time, you will also need to modify the command line to `configure`
1576 due to changes. Use `make print-configure` to show the command line used for
1577 your current configuration.
1578
1579 ### Using Fine-Grained Make Targets
1580
1581 The default behavior for make is to create consistent and correct output, at
1582 the expense of build speed, if necessary.
1583
1584 If you are prepared to take some risk of an incorrect build, and know enough of
1585 the system to understand how things build and interact, you can speed up the
1586 build process considerably by instructing make to only build a portion of the
1587 product.
1588
1589 #### Building Individual Modules
1590
1591 The safe way to use fine-grained make targets is to use the module specific
1592 make targets. All source code in the JDK is organized so it belongs to a
1593 module, e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific
1594 module, by giving it as make target: `make jdk.jdwp.agent`. If the specified
1595 module depends on other modules (e.g. `java.base`), those modules will be built
1596 first.
1597
1598 You can also specify a set of modules, just as you can always specify a set of
1599 make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi
1600 jdk.crypto.ucrypto`
1601
1602 #### Building Individual Module Phases
1603
1604 The build process for each module is divided into separate phases. Not all
1605 modules need all phases. Which are needed depends on what kind of source code
1606 and other artifact the module consists of. The phases are:
1607
1608 * `gensrc` (Generate source code to compile)
1609 * `gendata` (Generate non-source code artifacts)
1610 * `copy` (Copy resource artifacts)
1611 * `java` (Compile Java code)
1612 * `launchers` (Compile native executables)
1613 * `libs` (Compile native libraries)
1614 * `rmic` (Run the `rmic` tool)
1615
1616 You can build only a single phase for a module by using the notation
1617 `$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`,
1618 use `make java.base-gensrc`.
1619
1620 Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if
1621 present). Make will build all needed prerequisites before building the
1622 requested phase.
1623
1624 #### Skipping the Dependency Check
1625
1626 When using an iterative development style with frequent quick rebuilds, the
1627 dependency check made by make can take up a significant portion of the time
1628 spent on the rebuild. In such cases, it can be useful to bypass the dependency
1629 check in make.
1630
1631 > **Note that if used incorrectly, this can lead to a broken build!**
1632
1633 To achieve this, append `-only` to the build target. For instance, `make
1634 jdk.jdwp.agent-java-only` will *only* build the `java` phase of the
1635 `jdk.jdwp.agent` module. If the required dependencies are not present, the
1636 build can fail. On the other hand, the execution time measures in milliseconds.
1637
1638 A useful pattern is to build the first time normally (e.g. `make
1639 jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target.
1640
1641 #### Rebuilding Part of java.base (JDK\_FILTER)
1642
1643 If you are modifying files in `java.base`, which is the by far largest module
1644 in the JDK, then you need to rebuild all those files whenever a single file has
1645 changed. (This inefficiency will hopefully be addressed in JDK 10.)
1646
1647 As a hack, you can use the make control variable `JDK_FILTER` to specify a
1648 pattern that will be used to limit the set of files being recompiled. For
1649 instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods,
1650 `make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation
1651 to files in the `javax.crypto` package.
1652
1653 ### Learn About Mercurial
1654
1655 To become an efficient JDK developer, it is recommended that you invest in
1656 learning Mercurial properly. Here are some links that can get you started:
1657
1658 * [Mercurial for git users](http://www.mercurial-scm.org/wiki/GitConcepts)
1659 * [The official Mercurial tutorial](http://www.mercurial-scm.org/wiki/Tutorial)
1660 * [hg init](http://hginit.com/)
1661 * [Mercurial: The Definitive Guide](http://hgbook.red-bean.com/read/)
1662
1663 ## Understanding the Build System
1664
1665 This section will give you a more technical description on the details of the
1666 build system.
1667
1668 ### Configurations
1669
1670 The build system expects to find one or more configuration. These are
1671 technically defined by the `spec.gmk` in a subdirectory to the `build`
1672 subdirectory. The `spec.gmk` file is generated by `configure`, and contains in
1673 principle the configuration (directly or by files included by `spec.gmk`).
1674
1675 You can, in fact, select a configuration to build by pointing to the `spec.gmk`
1676 file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`.
1677 While this is not the recommended way to call `make` as a user, it is what is
1678 used under the hood by the build system.
1679
1680 ### Build Output Structure
1681
1682 The build output for a configuration will end up in `build/<configuration
1683 name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory
1684 contains the following important directories:
1685
1686 ```
1687 buildtools/
1688 configure-support/
1689 hotspot/
1690 images/
1691 jdk/
1692 make-support/
1693 support/
1694 test-results/
1695 test-support/
1696 ```
1697
1698 This is what they are used for:
1699
1700 * `images`: This is the directory were the output of the `*-image` make
1701 targets end up. For instance, `make jdk-image` ends up in `images/jdk`.
1702
1703 * `jdk`: This is the "exploded image". After `make jdk`, you will be able to
1704 launch the newly built JDK by running `$BUILD/jdk/bin/java`.
1705
1706 * `test-results`: This directory contains the results from running tests.
1707
1708 * `support`: This is an area for intermediate files needed during the build,
1709 e.g. generated source code, object files and class files. Some noteworthy
1710 directories in `support` is `gensrc`, which contains the generated source
1711 code, and the `modules_*` directories, which contains the files in a
1712 per-module hierarchy that will later be collapsed into the `jdk` directory
1713 of the exploded image.
1714
1715 * `buildtools`: This is an area for tools compiled for the build platform
1716 that are used during the rest of the build.
1717
1718 * `hotspot`: This is an area for intermediate files needed when building
1719 hotspot.
1720
1721 * `configure-support`, `make-support` and `test-support`: These directories
1722 contain files that are needed by the build system for `configure`, `make`
1723 and for running tests.
1724
1725 ### Fixpath
1726
1727 Windows path typically look like `C:\User\foo`, while Unix paths look like
1728 `/home/foo`. Tools with roots from Unix often experience issues related to this
1729 mismatch when running on Windows.
1730
1731 In the JDK build, we always use Unix paths internally, and only just before
1732 calling a tool that does not understand Unix paths do we convert them to
1733 Windows paths.
1734
1735 This conversion is done by the `fixpath` tool, which is a small wrapper that
1736 modifies unix-style paths to Windows-style paths in command lines. Fixpath is
1737 compiled automatically by `configure`.
1738
1739 ### Native Debug Symbols
1740
1741 Native libraries and executables can have debug symbol (and other debug
1742 information) associated with them. How this works is very much platform
1743 dependent, but a common problem is that debug symbol information takes a lot of
1744 disk space, but is rarely needed by the end user.
1745
1746 The JDK supports different methods on how to handle debug symbols. The
1747 method used is selected by `--with-native-debug-symbols`, and available methods
1748 are `none`, `internal`, `external`, `zipped`.
1749
1750 * `none` means that no debug symbols will be generated during the build.
1751
1752 * `internal` means that debug symbols will be generated during the build, and
1753 they will be stored in the generated binary.
1754
1755 * `external` means that debug symbols will be generated during the build, and
1756 after the compilation, they will be moved into a separate `.debuginfo` file.
1757 (This was previously known as FDS, Full Debug Symbols).
1758
1759 * `zipped` is like `external`, but the .debuginfo file will also be zipped
1760 into a `.diz` file.
1761
1762 When building for distribution, `zipped` is a good solution. Binaries built
1763 with `internal` is suitable for use by developers, since they facilitate
1764 debugging, but should be stripped before distributed to end users.
1765
1766 ### Autoconf Details
1767
1768 The `configure` script is based on the autoconf framework, but in some details
1769 deviate from a normal autoconf `configure` script.
1770
1771 The `configure` script in the top level directory of the JDK is just a thin
1772 wrapper that calls `make/autoconf/configure`. This in turn will run `autoconf`
1773 to create the runnable (generated) configure script, as
1774 `.build/generated-configure.sh`. Apart from being responsible for the
1775 generation of the runnable script, the `configure` script also provides
1776 functionality that is not easily expressed in the normal Autoconf framework. As
1777 part of this functionality, the generated script is called.
1778
1779 The build system will detect if the Autoconf source files have changed, and
1780 will trigger a regeneration of the generated script if needed. You can also
1781 manually request such an update by `bash configure autogen`.
1782
1783 In previous versions of the JDK, the generated script was checked in at
1784 `make/autoconf/generated-configure.sh`. This is no longer the case.
1785
1786 ### Developing the Build System Itself
1787
1788 This section contains a few remarks about how to develop for the build system
1789 itself. It is not relevant if you are only making changes in the product source
1790 code.
1791
1792 While technically using `make`, the make source files of the JDK does not
1793 resemble most other Makefiles. Instead of listing specific targets and actions
1794 (perhaps using patterns), the basic modus operandi is to call a high-level
1795 function (or properly, macro) from the API in `make/common`. For instance, to
1796 compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module,
1797 a call like this would be made:
1798
1799 ```
1800 $(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \
1801 SETUP := GENERATE_OLDBYTECODE, \
1802 SRC := $(TOPDIR)/src/jkd.foo/share/classes, \
1803 INCLUDES := jdk/internal/foo, \
1804 BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \
1805 ))
1806 ```
1807
1808 By encapsulating and expressing the high-level knowledge of *what* should be
1809 done, rather than *how* it should be done (as is normal in Makefiles), we can
1810 build a much more powerful and flexible build system.
1811
1812 Correct dependency tracking is paramount. Sloppy dependency tracking will lead
1813 to improper parallelization, or worse, race conditions.
1814
1815 To test for/debug race conditions, try running `make JOBS=1` and `make
1816 JOBS=100` and see if it makes any difference. (It shouldn't).
1817
1818 To compare the output of two different builds and see if, and how, they differ,
1819 run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two
1820 builds you want to compare.
1821
1822 To automatically build two consecutive versions and compare them, use
1823 `COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value
1824 assignments, like this:
1825 ```
1826 make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot
1827 ```
1828 See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`.
1829
1830 To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`.
1831 Use `JOBS=1` to avoid parallelism.
1832
1833 Please check that you adhere to the [Code Conventions for the Build System](
1834 http://openjdk.java.net/groups/build/doc/code-conventions.html) before
1835 submitting patches.
1836
1837 ## Contributing to the JDK
1838
1839 So, now you've built your JDK, and made your first patch, and want to
1840 contribute it back to the OpenJDK Community.
1841
1842 First of all: Thank you! We gladly welcome your contribution.
1843 However, please bear in mind that the JDK is a massive project, and we must ask
1844 you to follow our rules and guidelines to be able to accept your contribution.
1845
1846 The official place to start is the ['How to contribute' page](
1847 http://openjdk.java.net/contribute/). There is also an official (but somewhat
1848 outdated and skimpy on details) [Developer's Guide](
1849 http://openjdk.java.net/guide/).
1850
1851 If this seems overwhelming to you, the Adoption Group is there to help you! A
1852 good place to start is their ['New Contributor' page](
1853 https://wiki.openjdk.java.net/display/Adoption/New+Contributor), or start
1854 reading the comprehensive [Getting Started Kit](
1855 https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The
1856 Adoption Group will also happily answer any questions you have about
1857 contributing. Contact them by [mail](
1858 http://mail.openjdk.java.net/mailman/listinfo/adoption-discuss) or [IRC](
1859 http://openjdk.java.net/irc/).
1860
1861 ---
1862 # Override styles from the base CSS file that are not ideal for this document.
1863 header-includes:
1864 - '<style type="text/css">pre, code, tt { color: #1d6ae5; }</style>'
1865 ---