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 Note: The sparc port is deprecated.
124
125 ### Building on aarch64
126
127 At a minimum, a machine with 8 cores is advisable, as well as 8 GB of RAM.
128 (The more cores to use, the more memory you need.) At least 6 GB of free disk
129 space is required.
130
131 If you do not have access to sufficiently powerful hardware, it is also
132 possible to use [cross-compiling](#cross-compiling).
133
134 ### Building on 32-bit arm
135
136 This is not recommended. Instead, see the section on [Cross-compiling](
137 #cross-compiling).
138
139 ## Operating System Requirements
140
141 The mainline JDK project supports Linux, Solaris, macOS, AIX and Windows.
142 Support for other operating system, e.g. BSD, exists in separate "port"
143 projects.
144
145 In general, the JDK can be built on a wide range of versions of these operating
146 systems, but the further you deviate from what is tested on a daily basis, the
147 more likely you are to run into problems.
148
149 This table lists the OS versions used by Oracle when building the JDK. Such
150 information is always subject to change, but this table is up to date at the
151 time of writing.
152
153 Operating system Vendor/version used
154 ----------------- -------------------------------------------------------
155 Linux Oracle Enterprise Linux 6.4 / 7.6
156 Solaris Solaris 11.3 SRU 20
157 macOS Mac OS X 10.13 (High Sierra)
158 Windows Windows Server 2012 R2
159
160 The double version numbers for Linux and Solaris are due to the hybrid model
161 used at Oracle, where header files and external libraries from an older version
162 are used when building on a more modern version of the OS.
163
164 The Build Group has a wiki page with [Supported Build Platforms](
165 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms). From
166 time to time, this is updated by contributors to list successes or failures of
167 building on different platforms.
168
169 ### Windows
170
171 Windows XP is not a supported platform, but all newer Windows should be able to
172 build the JDK.
173
174 On Windows, it is important that you pay attention to the instructions in the
175 [Special Considerations](#special-considerations).
176
177 Windows is the only non-POSIX OS supported by the JDK, and as such, requires
178 some extra care. A POSIX support layer is required to build on Windows.
179 Currently, the only supported such layers are Cygwin and Windows Subsystem for
180 Linux (WSL). (Msys is no longer supported due to a too old bash; msys2 would
181 likely be possible to support in a future version but that would require effort
182 to implement.)
183
184 Internally in the build system, all paths are represented as Unix-style paths,
185 e.g. `/cygdrive/c/hg/jdk9/Makefile` rather than `C:\hg\jdk9\Makefile`. This
186 rule also applies to input to the build system, e.g. in arguments to
187 `configure`. So, use `--with-msvcr-dll=/cygdrive/c/msvcr100.dll` rather than
188 `--with-msvcr-dll=c:\msvcr100.dll`. For details on this conversion, see the section
189 on [Fixpath](#fixpath).
190
191 #### Cygwin
192
193 A functioning [Cygwin](http://www.cygwin.com/) environment is required for
194 building the JDK on Windows. If you have a 64-bit OS, we strongly recommend
195 using the 64-bit version of Cygwin.
196
197 **Note:** Cygwin has a model of continuously updating all packages without any
198 easy way to install or revert to a specific version of a package. This means
199 that whenever you add or update a package in Cygwin, you might (inadvertently)
200 update tools that are used by the JDK build process, and that can cause
201 unexpected build problems.
202
203 The JDK requires GNU Make 4.0 or greater in Cygwin. This is usually not a
204 problem, since Cygwin currently only distributes GNU Make at a version above
205 4.0.
206
207 Apart from the basic Cygwin installation, the following packages must also be
208 installed:
209
210 * `autoconf`
211 * `make`
212 * `zip`
213 * `unzip`
214
215 Often, you can install these packages using the following command line:
216 ```
217 <path to Cygwin setup>/setup-x86_64 -q -P autoconf -P make -P unzip -P zip
218 ```
219
220 Unfortunately, Cygwin can be unreliable in certain circumstances. If you
221 experience build tool crashes or strange issues when building on Windows,
222 please check the Cygwin FAQ on the ["BLODA" list](
223 https://cygwin.com/faq/faq.html#faq.using.bloda) and the section on [fork()
224 failures](https://cygwin.com/faq/faq.html#faq.using.fixing-fork-failures).
225
226 #### Windows Subsystem for Linux (WSL)
227
228 Windows 10 1809 or newer is supported due to a dependency on the wslpath utility
229 and support for environment variable sharing through WSLENV. Version 1803 can
230 work but intermittent build failures have been observed.
231
232 It's possible to build both Windows and Linux binaries from WSL. To build
233 Windows binaries, you must use a Windows boot JDK (located in a
234 Windows-accessible directory). To build Linux binaries, you must use a Linux
235 boot JDK. The default behavior is to build for Windows. To build for Linux, pass
236 `--build=x86_64-unknown-linux-gnu --host=x86_64-unknown-linux-gnu` to
237 `configure`.
238
239 If building Windows binaries, the source code must be located in a Windows-
240 accessible directory. This is because Windows executables (such as Visual Studio
241 and the boot JDK) must be able to access the source code. Also, the drive where
242 the source is stored must be mounted as case-insensitive by changing either
243 /etc/fstab or /etc/wsl.conf in WSL. Individual directories may be corrected
244 using the fsutil tool in case the source was cloned before changing the mount
245 options.
246
247 Note that while it's possible to build on WSL, testing is still not fully
248 supported.
249
250 ### Solaris
251
252 See `make/devkit/solaris11.1-package-list.txt` for a list of recommended
253 packages to install when building on Solaris. The versions specified in this
254 list is the versions used by the daily builds at Oracle, and is likely to work
255 properly.
256
257 Older versions of Solaris shipped a broken version of `objcopy`. At least
258 version 2.21.1 is needed, which is provided by Solaris 11 Update 1. Objcopy is
259 needed if you want to have external debug symbols. Please make sure you are
260 using at least version 2.21.1 of objcopy, or that you disable external debug
261 symbols.
262
263 Note: The Solaris port is deprecated.
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 ### AIX
301
302 Please consult the AIX section of the [Supported Build Platforms](
303 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms) OpenJDK
304 Build Wiki page for details about which versions of AIX are supported.
305
306 ## Native Compiler (Toolchain) Requirements
307
308 Large portions of the JDK consists of native code, that needs to be compiled to
309 be able to run on the target platform. In theory, toolchain and operating
310 system should be independent factors, but in practice there's more or less a
311 one-to-one correlation between target operating system and toolchain.
312
313 Operating system Supported toolchain
314 ------------------ -------------------------
315 Linux gcc, clang
316 macOS Apple Xcode (using clang)
317 Solaris Oracle Solaris Studio
318 AIX IBM XL C/C++
319 Windows Microsoft Visual Studio
320
321 Please see the individual sections on the toolchains for version
322 recommendations. As a reference, these versions of the toolchains are used, at
323 the time of writing, by Oracle for the daily builds of the JDK. It should be
324 possible to compile the JDK with both older and newer versions, but the closer
325 you stay to this list, the more likely you are to compile successfully without
326 issues.
327
328 Operating system Toolchain version
329 ------------------ -------------------------------------------------------
330 Linux gcc 9.2.0
331 macOS Apple Xcode 10.1 (using clang 10.0.0)
332 Solaris Oracle Solaris Studio 12.6 (with compiler version 5.15)
333 Windows Microsoft Visual Studio 2017 update 15.9.16
334
335 All compilers are expected to be able to compile to the C99 language standard,
336 as some C99 features are used in the source code. Microsoft Visual Studio
337 doesn't fully support C99 so in practice shared code is limited to using C99
338 features that it does support.
339
340 ### gcc
341
342 The minimum accepted version of gcc is 5.0. Older versions will generate a warning
343 by `configure` and are unlikely to work.
344
345 The JDK is currently known to be able to compile with at least version 9.2 of
346 gcc.
347
348 In general, any version between these two should be usable.
349
350 ### clang
351
352 The minimum accepted version of clang is 3.2. Older versions will not be
353 accepted by `configure`.
354
355 To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`.
356
357 ### Apple Xcode
358
359 The oldest supported version of Xcode is 8.
360
361 You will need the Xcode command lines developers tools to be able to build
362 the JDK. (Actually, *only* the command lines tools are needed, not the IDE.)
363 The simplest way to install these is to run:
364 ```
365 xcode-select --install
366 ```
367
368 It is advisable to keep an older version of Xcode for building the JDK when
369 updating Xcode. This [blog page](
370 http://iosdevelopertips.com/xcode/install-multiple-versions-of-xcode.html) has
371 good suggestions on managing multiple Xcode versions. To use a specific version
372 of Xcode, use `xcode-select -s` before running `configure`, or use
373 `--with-toolchain-path` to point to the version of Xcode to use, e.g.
374 `configure --with-toolchain-path=/Applications/Xcode8.app/Contents/Developer/usr/bin`
375
376 If you have recently (inadvertently) updated your OS and/or Xcode version, and
377 the JDK can no longer be built, please see the section on [Problems with the
378 Build Environment](#problems-with-the-build-environment), and [Getting
379 Help](#getting-help) to find out if there are any recent, non-merged patches
380 available for this update.
381
382 ### Oracle Solaris Studio
383
384 The minimum accepted version of the Solaris Studio compilers is 5.13
385 (corresponding to Solaris Studio 12.4). Older versions will not be accepted by
386 configure.
387
388 The Solaris Studio installation should contain at least these packages:
389
390 Package Version
391 -------------------------------------------------- -------------
392 developer/solarisstudio-124/backend 12.4-1.0.6.0
393 developer/solarisstudio-124/c++ 12.4-1.0.10.0
394 developer/solarisstudio-124/cc 12.4-1.0.4.0
395 developer/solarisstudio-124/library/c++-libs 12.4-1.0.10.0
396 developer/solarisstudio-124/library/math-libs 12.4-1.0.0.1
397 developer/solarisstudio-124/library/studio-gccrt 12.4-1.0.0.1
398 developer/solarisstudio-124/studio-common 12.4-1.0.0.1
399 developer/solarisstudio-124/studio-ja 12.4-1.0.0.1
400 developer/solarisstudio-124/studio-legal 12.4-1.0.0.1
401 developer/solarisstudio-124/studio-zhCN 12.4-1.0.0.1
402
403 Compiling with Solaris Studio can sometimes be finicky. This is the exact
404 version used by Oracle, which worked correctly at the time of writing:
405 ```
406 $ cc -V
407 cc: Sun C 5.13 SunOS_i386 2014/10/20
408 $ CC -V
409 CC: Sun C++ 5.13 SunOS_i386 151846-10 2015/10/30
410 ```
411
412 ### Microsoft Visual Studio
413
414 The minimum accepted version of Visual Studio is 2010. Older versions will not
415 be accepted by `configure`. The maximum accepted version of Visual Studio is
416 2019. Versions older than 2017 are unlikely to continue working for long.
417
418 If you have multiple versions of Visual Studio installed, `configure` will by
419 default pick the latest. You can request a specific version to be used by
420 setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2015`.
421
422 If you get `LINK: fatal error LNK1123: failure during conversion to COFF: file
423 invalid` when building using Visual Studio 2010, you have encountered
424 [KB2757355](http://support.microsoft.com/kb/2757355), a bug triggered by a
425 specific installation order. However, the solution suggested by the KB article
426 does not always resolve the problem. See [this stackoverflow discussion](
427 https://stackoverflow.com/questions/10888391) for other suggestions.
428
429 ### IBM XL C/C++
430
431 Please consult the AIX section of the [Supported Build Platforms](
432 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms) OpenJDK
433 Build Wiki page for details about which versions of XLC are supported.
434
435
436 ## Boot JDK Requirements
437
438 Paradoxically, building the JDK requires a pre-existing JDK. This is called the
439 "boot JDK". The boot JDK does not, however, have to be a JDK built directly from
440 the source code available in the OpenJDK Community. If you are porting the JDK
441 to a new platform, chances are that there already exists another JDK for that
442 platform that is usable as boot JDK.
443
444 The rule of thumb is that the boot JDK for building JDK major version *N*
445 should be a JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be
446 suitable as boot JDK. However, the JDK should be able to "build itself", so an
447 up-to-date build of the current JDK source is an acceptable alternative. If
448 you are following the *N-1* rule, make sure you've got the latest update
449 version, since JDK 8 GA might not be able to build JDK 9 on all platforms.
450
451 Early in the release cycle, version *N-1* may not yet have been released. In
452 that case, the preferred boot JDK will be version *N-2* until version *N-1*
453 is available.
454
455 If the boot JDK is not automatically detected, or the wrong JDK is picked, use
456 `--with-boot-jdk` to point to the JDK to use.
457
458 ### Getting JDK binaries
459
460 JDK binaries for Linux, Windows and macOS can be downloaded from
461 [jdk.java.net](http://jdk.java.net). An alternative is to download the
462 [Oracle JDK](http://www.oracle.com/technetwork/java/javase/downloads). Another
463 is the [Adopt OpenJDK Project](https://adoptopenjdk.net/), which publishes
464 experimental prebuilt binaries for various platforms.
465
466 On Linux you can also get a JDK from the Linux distribution. On apt-based
467 distros (like Debian and Ubuntu), `sudo apt-get install openjdk-<VERSION>-jdk`
468 is typically enough to install a JDK \<VERSION\>. On rpm-based distros (like
469 Fedora and Red Hat), try `sudo yum install java-<VERSION>-openjdk-devel`.
470
471 ## External Library Requirements
472
473 Different platforms require different external libraries. In general, libraries
474 are not optional - that is, they are either required or not used.
475
476 If a required library is not detected by `configure`, you need to provide the
477 path to it. There are two forms of the `configure` arguments to point to an
478 external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to
479 include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise,
480 but require the include files and library files to reside in a default
481 hierarchy under this directory. In most cases, it works fine.
482
483 As a fallback, the second version allows you to point to the include directory
484 and the lib directory separately.
485
486 ### FreeType
487
488 FreeType2 from [The FreeType Project](http://www.freetype.org/) is not required
489 on any platform. The exception is on Unix-based platforms when configuring such
490 that the build artifacts will reference a system installed library,
491 rather than bundling the JDK's own copy.
492
493 * To install on an apt-based Linux, try running `sudo apt-get install
494 libfreetype6-dev`.
495 * To install on an rpm-based Linux, try running `sudo yum install
496 freetype-devel`.
497 * To install on Solaris, try running `pkg install system/library/freetype-2`.
498
499 Use `--with-freetype-include=<path>` and `--with-freetype-lib=<path>`
500 if `configure` does not automatically locate the platform FreeType files.
501
502 ### CUPS
503
504 CUPS, [Common UNIX Printing System](http://www.cups.org) header files are
505 required on all platforms, except Windows. Often these files are provided by
506 your operating system.
507
508 * To install on an apt-based Linux, try running `sudo apt-get install
509 libcups2-dev`.
510 * To install on an rpm-based Linux, try running `sudo yum install
511 cups-devel`.
512 * To install on Solaris, try running `pkg install print/cups`.
513
514 Use `--with-cups=<path>` if `configure` does not properly locate your CUPS
515 files.
516
517 ### X11
518
519 Certain [X11](http://www.x.org/) libraries and include files are required on
520 Linux and Solaris.
521
522 * To install on an apt-based Linux, try running `sudo apt-get install
523 libx11-dev libxext-dev libxrender-dev libxrandr-dev libxtst-dev libxt-dev`.
524 * To install on an rpm-based Linux, try running `sudo yum install
525 libXtst-devel libXt-devel libXrender-devel libXrandr-devel libXi-devel`.
526 * To install on Solaris, try running `pkg install x11/header/x11-protocols
527 x11/library/libice x11/library/libpthread-stubs x11/library/libsm
528 x11/library/libx11 x11/library/libxau x11/library/libxcb
529 x11/library/libxdmcp x11/library/libxevie x11/library/libxext
530 x11/library/libxrender x11/library/libxrandr x11/library/libxscrnsaver
531 x11/library/libxtst x11/library/toolkit/libxt`.
532
533 Use `--with-x=<path>` if `configure` does not properly locate your X11 files.
534
535 ### ALSA
536
537 ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is
538 required on Linux. At least version 0.9.1 of ALSA is required.
539
540 * To install on an apt-based Linux, try running `sudo apt-get install
541 libasound2-dev`.
542 * To install on an rpm-based Linux, try running `sudo yum install
543 alsa-lib-devel`.
544
545 Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA
546 files.
547
548 ### libffi
549
550 libffi, the [Portable Foreign Function Interface Library](
551 http://sourceware.org/libffi) is required when building the Zero version of
552 Hotspot.
553
554 * To install on an apt-based Linux, try running `sudo apt-get install
555 libffi-dev`.
556 * To install on an rpm-based Linux, try running `sudo yum install
557 libffi-devel`.
558
559 Use `--with-libffi=<path>` if `configure` does not properly locate your libffi
560 files.
561
562 ## Build Tools Requirements
563
564 ### Autoconf
565
566 The JDK requires [Autoconf](http://www.gnu.org/software/autoconf) on all
567 platforms. At least version 2.69 is required.
568
569 * To install on an apt-based Linux, try running `sudo apt-get install
570 autoconf`.
571 * To install on an rpm-based Linux, try running `sudo yum install
572 autoconf`.
573 * To install on macOS, try running `brew install autoconf`.
574 * To install on Windows, try running `<path to Cygwin setup>/setup-x86_64 -q
575 -P autoconf`.
576
577 If `configure` has problems locating your installation of autoconf, you can
578 specify it using the `AUTOCONF` environment variable, like this:
579
580 ```
581 AUTOCONF=<path to autoconf> configure ...
582 ```
583
584 ### GNU Make
585
586 The JDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors
587 of make are supported.
588
589 At least version 3.81 of GNU Make must be used. For distributions supporting
590 GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful
591 functionality to handle parallel building (supported by `--with-output-sync`)
592 and speed and stability improvements.
593
594 Note that `configure` locates and verifies a properly functioning version of
595 `make` and stores the path to this `make` binary in the configuration. If you
596 start a build using `make` on the command line, you will be using the version
597 of make found first in your `PATH`, and not necessarily the one stored in the
598 configuration. This initial make will be used as "bootstrap make", and in a
599 second stage, the make located by `configure` will be called. Normally, this
600 will present no issues, but if you have a very old `make`, or a non-GNU Make
601 `make` in your path, this might cause issues.
602
603 If you want to override the default make found by `configure`, use the `MAKE`
604 configure variable, e.g. `configure MAKE=/opt/gnu/make`.
605
606 On Solaris, it is common to call the GNU version of make by using `gmake`.
607
608 ### GNU Bash
609
610 The JDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells
611 are supported.
612
613 At least version 3.2 of GNU Bash must be used.
614
615 ## Running Configure
616
617 To build the JDK, you need a "configuration", which consists of a directory
618 where to store the build output, coupled with information about the platform,
619 the specific build machine, and choices that affect how the JDK is built.
620
621 The configuration is created by the `configure` script. The basic invocation of
622 the `configure` script looks like this:
623
624 ```
625 bash configure [options]
626 ```
627
628 This will create an output directory containing the configuration and setup an
629 area for the build result. This directory typically looks like
630 `build/linux-x64-server-release`, but the actual name depends on your specific
631 configuration. (It can also be set directly, see [Using Multiple
632 Configurations](#using-multiple-configurations)). This directory is referred to
633 as `$BUILD` in this documentation.
634
635 `configure` will try to figure out what system you are running on and where all
636 necessary build components are. If you have all prerequisites for building
637 installed, it should find everything. If it fails to detect any component
638 automatically, it will exit and inform you about the problem.
639
640 Some command line examples:
641
642 * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`:
643 ```
644 bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32
645 ```
646
647 * Create a debug build with the `server` JVM and DTrace enabled:
648 ```
649 bash configure --enable-debug --with-jvm-variants=server --enable-dtrace
650 ```
651
652 ### Common Configure Arguments
653
654 Here follows some of the most common and important `configure` argument.
655
656 To get up-to-date information on *all* available `configure` argument, please
657 run:
658 ```
659 bash configure --help
660 ```
661
662 (Note that this help text also include general autoconf options, like
663 `--dvidir`, that is not relevant to the JDK. To list only JDK-specific
664 features, use `bash configure --help=short` instead.)
665
666 #### Configure Arguments for Tailoring the Build
667
668 * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand
669 for `--with-debug-level=fastdebug`)
670 * `--with-debug-level=<level>` - Set the debug level, which can be `release`,
671 `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized`
672 is variant of `release` with additional Hotspot debug code.
673 * `--with-native-debug-symbols=<method>` - Specify if and how native debug
674 symbols should be built. Available methods are `none`, `internal`,
675 `external`, `zipped`. Default behavior depends on platform. See [Native
676 Debug Symbols](#native-debug-symbols) for more details.
677 * `--with-version-string=<string>` - Specify the version string this build
678 will be identified with.
679 * `--with-version-<part>=<value>` - A group of options, where `<part>` can be
680 any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use
681 these options to modify just the corresponding part of the version string
682 from the default, or the value provided by `--with-version-string`.
683 * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant
684 (or variants) of Hotspot. Valid variants are: `server`, `client`,
685 `minimal`, `core`, `zero`, `custom`. Note that not all
686 variants are possible to combine in a single build.
687 * `--enable-jvm-feature-<feature>` or `--disable-jvm-feature-<feature>` -
688 Include (or exclude) `<feature>` as a JVM feature in Hotspot. You can also
689 specify a list of features to be enabled, separated by space or comma, as
690 `--with-jvm-features=<feature>[,<feature>...]`. If you prefix `<feature>`
691 with a `-`, it will be disabled. These options will modify the default list
692 of features for the JVM variant(s) you are building. For the `custom` JVM
693 variant, the default list is empty. A complete list of valid JVM features
694 can be found using `bash configure --help`.
695 * `--with-target-bits=<bits>` - Create a target binary suitable for running
696 on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build
697 platform, instead of doing a full cross-compile. (This is known as a
698 *reduced* build.)
699
700 On Linux, BSD and AIX, it is possible to override where Java by default
701 searches for runtime/JNI libraries. This can be useful in situations where
702 there is a special shared directory for system JNI libraries. This setting
703 can in turn be overriden at runtime by setting the `java.library.path` property.
704
705 * `--with-jni-libpath=<path>` - Use the specified path as a default
706 when searching for runtime libraries.
707
708 #### Configure Arguments for Native Compilation
709
710 * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources
711 * `--with-sysroot=<path>` - Use this directory as sysroot
712 * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the
713 default path when searching for all kinds of binaries
714 * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when
715 searching for toolchain binaries (compilers etc)
716 * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C
717 files
718 * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++
719 files
720 * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK
721 libraries
722
723 #### Configure Arguments for External Dependencies
724
725 * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK](
726 #boot-jdk-requirements)
727 * `--with-freetype=<path>` - Set the path to [FreeType](#freetype)
728 * `--with-cups=<path>` - Set the path to [CUPS](#cups)
729 * `--with-x=<path>` - Set the path to [X11](#x11)
730 * `--with-alsa=<path>` - Set the path to [ALSA](#alsa)
731 * `--with-libffi=<path>` - Set the path to [libffi](#libffi)
732 * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests](
733 #running-tests)
734
735 Certain third-party libraries used by the JDK (libjpeg, giflib, libpng, lcms
736 and zlib) are included in the JDK repository. The default behavior of the
737 JDK build is to use the included ("bundled") versions of libjpeg, giflib,
738 libpng and lcms.
739 For zlib, the system lib (if present) is used except on Windows and AIX.
740 However the bundled libraries may be replaced by an external version.
741 To do so, specify `system` as the `<source>` option in these arguments.
742 (The default is `bundled`).
743
744 * `--with-libjpeg=<source>` - Use the specified source for libjpeg
745 * `--with-giflib=<source>` - Use the specified source for giflib
746 * `--with-libpng=<source>` - Use the specified source for libpng
747 * `--with-lcms=<source>` - Use the specified source for lcms
748 * `--with-zlib=<source>` - Use the specified source for zlib
749
750 On Linux, it is possible to select either static or dynamic linking of the C++
751 runtime. The default is static linking, with dynamic linking as fallback if the
752 static library is not found.
753
754 * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic`
755 or `default`) for linking the C++ runtime.
756
757 ### Configure Control Variables
758
759 It is possible to control certain aspects of `configure` by overriding the
760 value of `configure` variables, either on the command line or in the
761 environment.
762
763 Normally, this is **not recommended**. If used improperly, it can lead to a
764 broken configuration. Unless you're well versed in the build system, this is
765 hard to use properly. Therefore, `configure` will print a warning if this is
766 detected.
767
768 However, there are a few `configure` variables, known as *control variables*
769 that are supposed to be overriden on the command line. These are variables that
770 describe the location of tools needed by the build, like `MAKE` or `GREP`. If
771 any such variable is specified, `configure` will use that value instead of
772 trying to autodetect the tool. For instance, `bash configure
773 MAKE=/opt/gnumake4.0/bin/make`.
774
775 If a configure argument exists, use that instead, e.g. use `--with-jtreg`
776 instead of setting `JTREGEXE`.
777
778 Also note that, despite what autoconf claims, setting `CFLAGS` will not
779 accomplish anything. Instead use `--with-extra-cflags` (and similar for
780 `cxxflags` and `ldflags`).
781
782 ## Running Make
783
784 When you have a proper configuration, all you need to do to build the JDK is to
785 run `make`. (But see the warning at [GNU Make](#gnu-make) about running the
786 correct version of make.)
787
788 When running `make` without any arguments, the default target is used, which is
789 the same as running `make default` or `make jdk`. This will build a minimal (or
790 roughly minimal) set of compiled output (known as an "exploded image") needed
791 for a developer to actually execute the newly built JDK. The idea is that in an
792 incremental development fashion, when doing a normal make, you should only
793 spend time recompiling what's changed (making it purely incremental) and only
794 do the work that's needed to actually run and test your code.
795
796 The output of the exploded image resides in `$BUILD/jdk`. You can test the
797 newly built JDK like this: `$BUILD/jdk/bin/java -version`.
798
799 ### Common Make Targets
800
801 Apart from the default target, here are some common make targets:
802
803 * `hotspot` - Build all of hotspot (but only hotspot)
804 * `hotspot-<variant>` - Build just the specified jvm variant
805 * `images` or `product-images` - Build the JDK image
806 * `docs` or `docs-image` - Build the documentation image
807 * `test-image` - Build the test image
808 * `all` or `all-images` - Build all images (product, docs and test)
809 * `bootcycle-images` - Build images twice, second time with newly built JDK
810 (good for testing)
811 * `clean` - Remove all files generated by make, but not those generated by
812 configure
813 * `dist-clean` - Remove all files, including configuration
814
815 Run `make help` to get an up-to-date list of important make targets and make
816 control variables.
817
818 It is possible to build just a single module, a single phase, or a single phase
819 of a single module, by creating make targets according to these followin
820 patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`,
821 `launchers`, or `libs`. See [Using Fine-Grained Make Targets](
822 #using-fine-grained-make-targets) for more details about this functionality.
823
824 * `<phase>` - Build the specified phase and everything it depends on
825 * `<module>` - Build the specified module and everything it depends on
826 * `<module>-<phase>` - Compile the specified phase for the specified module
827 and everything it depends on
828
829 Similarly, it is possible to clean just a part of the build by creating make
830 targets according to these patterns:
831
832 * `clean-<outputdir>` - Remove the subdir in the output dir with the name
833 * `clean-<phase>` - Remove all build results related to a certain build
834 phase
835 * `clean-<module>` - Remove all build results related to a certain module
836 * `clean-<module>-<phase>` - Remove all build results related to a certain
837 module and phase
838
839 ### Make Control Variables
840
841 It is possible to control `make` behavior by overriding the value of `make`
842 variables, either on the command line or in the environment.
843
844 Normally, this is **not recommended**. If used improperly, it can lead to a
845 broken build. Unless you're well versed in the build system, this is hard to
846 use properly. Therefore, `make` will print a warning if this is detected.
847
848 However, there are a few `make` variables, known as *control variables* that
849 are supposed to be overriden on the command line. These make up the "make time"
850 configuration, as opposed to the "configure time" configuration.
851
852 #### General Make Control Variables
853
854 * `JOBS` - Specify the number of jobs to build with. See [Build
855 Performance](#build-performance).
856 * `LOG` - Specify the logging level and functionality. See [Checking the
857 Build Log File](#checking-the-build-log-file)
858 * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using
859 Multiple Configurations](#using-multiple-configurations)
860
861 #### Test Make Control Variables
862
863 These make control variables only make sense when running tests. Please see
864 [Testing the JDK](testing.html) for details.
865
866 * `TEST`
867 * `TEST_JOBS`
868 * `JTREG`
869 * `GTEST`
870
871 #### Advanced Make Control Variables
872
873 These advanced make control variables can be potentially unsafe. See [Hints and
874 Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and
875 [Understanding the Build System](#understanding-the-build-system) for details.
876
877 * `SPEC`
878 * `CONF_CHECK`
879 * `COMPARE_BUILD`
880 * `JDK_FILTER`
881 * `SPEC_FILTER`
882
883 ## Running Tests
884
885 Most of the JDK tests are using the [JTReg](http://openjdk.java.net/jtreg)
886 test framework. Make sure that your configuration knows where to find your
887 installation of JTReg. If this is not picked up automatically, use the
888 `--with-jtreg=<path to jtreg home>` option to point to the JTReg framework.
889 Note that this option should point to the JTReg home, i.e. the top directory,
890 containing `lib/jtreg.jar` etc.
891
892 The [Adoption Group](https://wiki.openjdk.java.net/display/Adoption) provides
893 recent builds of jtreg [here](
894 https://ci.adoptopenjdk.net/view/Dependencies/job/jtreg/lastSuccessfulBuild/artifact).
895 Download the latest `.tar.gz` file, unpack it, and point `--with-jtreg` to the
896 `jtreg` directory that you just unpacked.
897
898 To execute the most basic tests (tier 1), use:
899 ```
900 make run-test-tier1
901 ```
902
903 For more details on how to run tests, please see the [Testing
904 the JDK](testing.html) document.
905
906 ## Cross-compiling
907
908 Cross-compiling means using one platform (the *build* platform) to generate
909 output that can ran on another platform (the *target* platform).
910
911 The typical reason for cross-compiling is that the build is performed on a more
912 powerful desktop computer, but the resulting binaries will be able to run on a
913 different, typically low-performing system. Most of the complications that
914 arise when building for embedded is due to this separation of *build* and
915 *target* systems.
916
917 This requires a more complex setup and build procedure. This section assumes
918 you are familiar with cross-compiling in general, and will only deal with the
919 particularities of cross-compiling the JDK. If you are new to cross-compiling,
920 please see the [external links at Wikipedia](
921 https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start
922 on reading materials.
923
924 Cross-compiling the JDK requires you to be able to build both for the build
925 platform and for the target platform. The reason for the former is that we need
926 to build and execute tools during the build process, both native tools and Java
927 tools.
928
929 If all you want to do is to compile a 32-bit version, for the same OS, on a
930 64-bit machine, consider using `--with-target-bits=32` instead of doing a
931 full-blown cross-compilation. (While this surely is possible, it's a lot more
932 work and will take much longer to build.)
933
934 ### Cross compiling the easy way with OpenJDK devkits
935
936 The OpenJDK build system provides out-of-the box support for creating and using
937 so called devkits. A `devkit` is basically a collection of a cross-compiling
938 toolchain and a sysroot environment which can easily be used together with the
939 `--with-devkit` configure option to cross compile the OpenJDK. On Linux/x86_64,
940 the following command:
941 ```
942 bash configure --with-devkit=<devkit-path> --openjdk-target=ppc64-linux-gnu && make
943 ```
944
945 will configure and build OpenJDK for Linux/ppc64 assuming that `<devkit-path>`
946 points to a Linux/x86_64 to Linux/ppc64 devkit.
947
948 Devkits can be created from the `make/devkit` directory by executing:
949 ```
950 make [ TARGETS="<TARGET_TRIPLET>+" ] [ BASE_OS=<OS> ] [ BASE_OS_VERSION=<VER> ]
951 ```
952
953 where `TARGETS` contains one or more `TARGET_TRIPLET`s of the form
954 described in [section 3.4 of the GNU Autobook](
955 https://sourceware.org/autobook/autobook/autobook_17.html). If no
956 targets are given, a native toolchain for the current platform will be
957 created. Currently, at least the following targets are known to work:
958
959 Supported devkit targets
960 -------------------------
961 x86_64-linux-gnu
962 aarch64-linux-gnu
963 arm-linux-gnueabihf
964 ppc64-linux-gnu
965 ppc64le-linux-gnu
966 s390x-linux-gnu
967
968 `BASE_OS` must be one of "OEL6" for Oracle Enterprise Linux 6 or
969 "Fedora" (if not specified "OEL6" will be the default). If the base OS
970 is "Fedora" the corresponding Fedora release can be specified with the
971 help of the `BASE_OS_VERSION` option (with "27" as default version).
972 If the build is successful, the new devkits can be found in the
973 `build/devkit/result` subdirectory:
974 ```
975 cd make/devkit
976 make TARGETS="ppc64le-linux-gnu aarch64-linux-gnu" BASE_OS=Fedora BASE_OS_VERSION=21
977 ls -1 ../../build/devkit/result/
978 x86_64-linux-gnu-to-aarch64-linux-gnu
979 x86_64-linux-gnu-to-ppc64le-linux-gnu
980 ```
981
982 Notice that devkits are not only useful for targeting different build
983 platforms. Because they contain the full build dependencies for a
984 system (i.e. compiler and root file system), they can easily be used
985 to build well-known, reliable and reproducible build environments. You
986 can for example create and use a devkit with GCC 7.3 and a Fedora 12
987 sysroot environment (with glibc 2.11) on Ubuntu 14.04 (which doesn't
988 have GCC 7.3 by default) to produce OpenJDK binaries which will run on
989 all Linux systems with runtime libraries newer than the ones from
990 Fedora 12 (e.g. Ubuntu 16.04, SLES 11 or RHEL 6).
991
992 ### Boot JDK and Build JDK
993
994 When cross-compiling, make sure you use a boot JDK that runs on the *build*
995 system, and not on the *target* system.
996
997 To be able to build, we need a "Build JDK", which is a JDK built from the
998 current sources (that is, the same as the end result of the entire build
999 process), but able to run on the *build* system, and not the *target* system.
1000 (In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when
1001 building JDK 9.)
1002
1003 The build process will create a minimal Build JDK for you, as part of building.
1004 To speed up the build, you can use `--with-build-jdk` to `configure` to point
1005 to a pre-built Build JDK. Please note that the build result is unpredictable,
1006 and can possibly break in subtle ways, if the Build JDK does not **exactly**
1007 match the current sources.
1008
1009 ### Specifying the Target Platform
1010
1011 You *must* specify the target platform when cross-compiling. Doing so will also
1012 automatically turn the build into a cross-compiling mode. The simplest way to
1013 do this is to use the `--openjdk-target` argument, e.g.
1014 `--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`.
1015 This will automatically set the `--build`, `--host` and `--target` options for
1016 autoconf, which can otherwise be confusing. (In autoconf terminology, the
1017 "target" is known as "host", and "target" is used for building a Canadian
1018 cross-compiler.)
1019
1020 ### Toolchain Considerations
1021
1022 You will need two copies of your toolchain, one which generates output that can
1023 run on the target system (the normal, or *target*, toolchain), and one that
1024 generates output that can run on the build system (the *build* toolchain). Note
1025 that cross-compiling is only supported for gcc at the time being. The gcc
1026 standard is to prefix cross-compiling toolchains with the target denominator.
1027 If you follow this standard, `configure` is likely to pick up the toolchain
1028 correctly.
1029
1030 The *build* toolchain will be autodetected just the same way the normal
1031 *build*/*target* toolchain will be autodetected when not cross-compiling. If
1032 this is not what you want, or if the autodetection fails, you can specify a
1033 devkit containing the *build* toolchain using `--with-build-devkit` to
1034 `configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments.
1035
1036 It is often helpful to locate the cross-compilation tools, headers and
1037 libraries in a separate directory, outside the normal path, and point out that
1038 directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and
1039 appending the directory when searching for cross-compilations tools
1040 (`--with-toolchain-path`). As a compact form, you can also use `--with-devkit`
1041 to point to a single directory, if it is correctly setup. (See `basics.m4` for
1042 details.)
1043
1044 ### Native Libraries
1045
1046 You will need copies of external native libraries for the *target* system,
1047 present on the *build* machine while building.
1048
1049 Take care not to replace the *build* system's version of these libraries by
1050 mistake, since that can render the *build* machine unusable.
1051
1052 Make sure that the libraries you point to (ALSA, X11, etc) are for the
1053 *target*, not the *build*, platform.
1054
1055 #### ALSA
1056
1057 You will need alsa libraries suitable for your *target* system. For most cases,
1058 using Debian's pre-built libraries work fine.
1059
1060 Note that alsa is needed even if you only want to build a headless JDK.
1061
1062 * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and
1063 search for the `libasound2` and `libasound2-dev` packages for your *target*
1064 system. Download them to /tmp.
1065
1066 * Install the libraries into the cross-compilation toolchain. For instance:
1067 ```
1068 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc
1069 dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb .
1070 dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb .
1071 ```
1072
1073 * If alsa is not properly detected by `configure`, you can point it out by
1074 `--with-alsa`.
1075
1076 #### X11
1077
1078 You will need X11 libraries suitable for your *target* system. For most cases,
1079 using Debian's pre-built libraries work fine.
1080
1081 Note that X11 is needed even if you only want to build a headless JDK.
1082
1083 * Go to [Debian Package Search](https://www.debian.org/distrib/packages),
1084 search for the following packages for your *target* system, and download them
1085 to /tmp/target-x11:
1086 * libxi
1087 * libxi-dev
1088 * x11proto-core-dev
1089 * x11proto-input-dev
1090 * x11proto-kb-dev
1091 * x11proto-render-dev
1092 * x11proto-xext-dev
1093 * libice-dev
1094 * libxrender
1095 * libxrender-dev
1096 * libxrandr-dev
1097 * libsm-dev
1098 * libxt-dev
1099 * libx11
1100 * libx11-dev
1101 * libxtst
1102 * libxtst-dev
1103 * libxext
1104 * libxext-dev
1105
1106 * Install the libraries into the cross-compilation toolchain. For instance:
1107 ```
1108 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr
1109 mkdir X11R6
1110 cd X11R6
1111 for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done
1112 mv usr/* .
1113 cd lib
1114 cp arm-linux-gnueabihf/* .
1115 ```
1116
1117 You can ignore the following messages. These libraries are not needed to
1118 successfully complete a full JDK build.
1119 ```
1120 cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory
1121 cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory
1122 cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory
1123 ```
1124
1125 * If the X11 libraries are not properly detected by `configure`, you can
1126 point them out by `--with-x`.
1127
1128 ### Creating And Using Sysroots With qemu-deboostrap
1129
1130 Fortunately, you can create sysroots for foreign architectures with tools
1131 provided by your OS. On Debian/Ubuntu systems, one could use `qemu-deboostrap` to
1132 create the *target* system chroot, which would have the native libraries and headers
1133 specific to that *target* system. After that, we can use the cross-compiler on the *build*
1134 system, pointing into chroot to get the build dependencies right. This allows building
1135 for foreign architectures with native compilation speed.
1136
1137 For example, cross-compiling to AArch64 from x86_64 could be done like this:
1138
1139 * Install cross-compiler on the *build* system:
1140 ```
1141 apt install g++-aarch64-linux-gnu gcc-aarch64-linux-gnu
1142 ```
1143
1144 * Create chroot on the *build* system, configuring it for *target* system:
1145 ```
1146 sudo qemu-debootstrap --arch=arm64 --verbose \
1147 --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 \
1148 --resolve-deps jessie /chroots/arm64 http://httpredir.debian.org/debian/
1149 ```
1150
1151 * Configure and build with newly created chroot as sysroot/toolchain-path:
1152 ```
1153 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/
1154 make images
1155 ls build/linux-aarch64-normal-server-release/
1156 ```
1157
1158 The build does not create new files in that chroot, so it can be reused for multiple builds
1159 without additional cleanup.
1160
1161 Architectures that are known to successfully cross-compile like this are:
1162
1163 Target `CC` `CXX` `--arch=...` `--openjdk-target=...`
1164 ------------ ------------------------- --------------------------- ------------- -----------------------
1165 x86 default default i386 i386-linux-gnu
1166 armhf gcc-arm-linux-gnueabihf g++-arm-linux-gnueabihf armhf arm-linux-gnueabihf
1167 aarch64 gcc-aarch64-linux-gnu g++-aarch64-linux-gnu arm64 aarch64-linux-gnu
1168 ppc64el gcc-powerpc64le-linux-gnu g++-powerpc64le-linux-gnu ppc64el powerpc64le-linux-gnu
1169 s390x gcc-s390x-linux-gnu g++-s390x-linux-gnu s390x s390x-linux-gnu
1170
1171 Additional architectures might be supported by Debian/Ubuntu Ports.
1172
1173 ### Building for ARM/aarch64
1174
1175 A common cross-compilation target is the ARM CPU. When building for ARM, it is
1176 useful to set the ABI profile. A number of pre-defined ABI profiles are
1177 available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt,
1178 armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer
1179 properly supported by the JDK.
1180
1181 ### Verifying the Build
1182
1183 The build will end up in a directory named like
1184 `build/linux-arm-normal-server-release`.
1185
1186 Inside this build output directory, the `images/jdk` will contain the newly
1187 built JDK, for your *target* system.
1188
1189 Copy these folders to your *target* system. Then you can run e.g.
1190 `images/jdk/bin/java -version`.
1191
1192 ## Build Performance
1193
1194 Building the JDK requires a lot of horsepower. Some of the build tools can be
1195 adjusted to utilize more or less of resources such as parallel threads and
1196 memory. The `configure` script analyzes your system and selects reasonable
1197 values for such options based on your hardware. If you encounter resource
1198 problems, such as out of memory conditions, you can modify the detected values
1199 with:
1200
1201 * `--with-num-cores` -- number of cores in the build system, e.g.
1202 `--with-num-cores=8`.
1203
1204 * `--with-memory-size` -- memory (in MB) available in the build system, e.g.
1205 `--with-memory-size=1024`
1206
1207 You can also specify directly the number of build jobs to use with
1208 `--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag
1209 to `make`. In most cases it will be ignored by the makefiles, but it can cause
1210 problems for some make targets.
1211
1212 It might also be necessary to specify the JVM arguments passed to the Boot JDK,
1213 using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the
1214 default JVM arguments passed to the Boot JDK.
1215
1216 At the end of a successful execution of `configure`, you will get a performance
1217 summary, indicating how well the build will perform. Here you will also get
1218 performance hints. If you want to build fast, pay attention to those!
1219
1220 If you want to tweak build performance, run with `make LOG=info` to get a build
1221 time summary at the end of the build process.
1222
1223 ### Disk Speed
1224
1225 If you are using network shares, e.g. via NFS, for your source code, make sure
1226 the build directory is situated on local disk (e.g. by `ln -s
1227 /localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely
1228 high for building on a network share; close to unusable.
1229
1230 Also, make sure that your build tools (including Boot JDK and toolchain) is
1231 located on a local disk and not a network share.
1232
1233 As has been stressed elsewhere, do use SSD for source code and build directory,
1234 as well as (if possible) the build tools.
1235
1236 ### Virus Checking
1237
1238 The use of virus checking software, especially on Windows, can *significantly*
1239 slow down building of the JDK. If possible, turn off such software, or exclude
1240 the directory containing the JDK source code from on-the-fly checking.
1241
1242 ### Ccache
1243
1244 The JDK build supports building with ccache when using gcc or clang. Using
1245 ccache can radically speed up compilation of native code if you often rebuild
1246 the same sources. Your milage may vary however, so we recommend evaluating it
1247 for yourself. To enable it, make sure it's on the path and configure with
1248 `--enable-ccache`.
1249
1250 ### Precompiled Headers
1251
1252 By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains
1253 were it is properly supported (clang, gcc, and Visual Studio). Normally, this
1254 speeds up the build process, but in some circumstances, it can actually slow
1255 things down.
1256
1257 You can experiment by disabling precompiled headers using
1258 `--disable-precompiled-headers`.
1259
1260 ### Icecc / icecream
1261
1262 [icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a
1263 distributed compiler network. If you have multiple machines available for
1264 building the JDK, you can drastically cut individual build times by utilizing
1265 it.
1266
1267 To use, setup an icecc network, and install icecc on the build machine. Then
1268 run `configure` using `--enable-icecc`.
1269
1270 ### Using sjavac
1271
1272 To speed up Java compilation, especially incremental compilations, you can try
1273 the experimental sjavac compiler by using `--enable-sjavac`.
1274
1275 ### Building the Right Target
1276
1277 Selecting the proper target to build can have dramatic impact on build time.
1278 For normal usage, `jdk` or the default target is just fine. You only need to
1279 build `images` for shipping, or if your tests require it.
1280
1281 See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on
1282 how to build an even smaller subset of the product.
1283
1284 ## Troubleshooting
1285
1286 If your build fails, it can sometimes be difficult to pinpoint the problem or
1287 find a proper solution.
1288
1289 ### Locating the Source of the Error
1290
1291 When a build fails, it can be hard to pinpoint the actual cause of the error.
1292 In a typical build process, different parts of the product build in parallel,
1293 with the output interlaced.
1294
1295 #### Build Failure Summary
1296
1297 To help you, the build system will print a failure summary at the end. It looks
1298 like this:
1299
1300 ```
1301 ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2)
1302
1303 === Output from failing command(s) repeated here ===
1304 * For target hotspot_variant-server_libjvm_objs_psMemoryPool.o:
1305 /localhome/hg/jdk9-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type
1306 ... (rest of output omitted)
1307
1308 * All command lines available in /localhome/hg/jdk9-sandbox/build/linux-x64/make-support/failure-logs.
1309 === End of repeated output ===
1310
1311 === Make failed targets repeated here ===
1312 lib/CompileJvm.gmk:207: recipe for target '/localhome/hg/jdk9-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed
1313 make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed
1314 === End of repeated output ===
1315
1316 Hint: Try searching the build log for the name of the first failed target.
1317 Hint: If caused by a warning, try configure --disable-warnings-as-errors.
1318 ```
1319
1320 Let's break it down! First, the selected configuration, and the top-level
1321 target you entered on the command line that caused the failure is printed.
1322
1323 Then, between the `Output from failing command(s) repeated here` and `End of
1324 repeated output` the first lines of output (stdout and stderr) from the actual
1325 failing command is repeated. In most cases, this is the error message that
1326 caused the build to fail. If multiple commands were failing (this can happen in
1327 a parallel build), output from all failed commands will be printed here.
1328
1329 The path to the `failure-logs` directory is printed. In this file you will find
1330 a `<target>.log` file that contains the output from this command in its
1331 entirety, and also a `<target>.cmd`, which contain the complete command line
1332 used for running this command. You can re-run the failing command by executing
1333 `. <path to failure-logs>/<target>.cmd` in your shell.
1334
1335 Another way to trace the failure is to follow the chain of make targets, from
1336 top-level targets to individual file targets. Between `Make failed targets
1337 repeated here` and `End of repeated output` the output from make showing this
1338 chain is repeated. The first failed recipe will typically contain the full path
1339 to the file in question that failed to compile. Following lines will show a
1340 trace of make targets why we ended up trying to compile that file.
1341
1342 Finally, some hints are given on how to locate the error in the complete log.
1343 In this example, we would try searching the log file for "`psMemoryPool.o`".
1344 Another way to quickly locate make errors in the log is to search for "`]
1345 Error`" or "`***`".
1346
1347 Note that the build failure summary will only help you if the issue was a
1348 compilation failure or similar. If the problem is more esoteric, or is due to
1349 errors in the build machinery, you will likely get empty output logs, and `No
1350 indication of failed target found` instead of the make target chain.
1351
1352 #### Checking the Build Log File
1353
1354 The output (stdout and stderr) from the latest build is always stored in
1355 `$BUILD/build.log`. The previous build log is stored as `build.log.old`. This
1356 means that it is not necessary to redirect the build output yourself if you
1357 want to process it.
1358
1359 You can increase the verbosity of the log file, by the `LOG` control variable
1360 to `make`. If you want to see the command lines used in compilations, use
1361 `LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug`
1362 or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g.
1363 `LOG=info,cmdlines`. The `debug` log level will show most shell commands
1364 executed by make, and `trace` will show all. Beware that both these log levels
1365 will produce a massive build log!
1366
1367 ### Fixing Unexpected Build Failures
1368
1369 Most of the time, the build will fail due to incorrect changes in the source
1370 code.
1371
1372 Sometimes the build can fail with no apparent changes that have caused the
1373 failure. If this is the first time you are building the JDK on this particular
1374 computer, and the build fails, the problem is likely with your build
1375 environment. But even if you have previously built the JDK with success, and it
1376 now fails, your build environment might have changed (perhaps due to OS
1377 upgrades or similar). But most likely, such failures are due to problems with
1378 the incremental rebuild.
1379
1380 #### Problems with the Build Environment
1381
1382 Make sure your configuration is correct. Re-run `configure`, and look for any
1383 warnings. Warnings that appear in the middle of the `configure` output is also
1384 repeated at the end, after the summary. The entire log is stored in
1385 `$BUILD/configure.log`.
1386
1387 Verify that the summary at the end looks correct. Are you indeed using the Boot
1388 JDK and native toolchain that you expect?
1389
1390 By default, the JDK has a strict approach where warnings from the compiler is
1391 considered errors which fail the build. For very new or very old compiler
1392 versions, this can trigger new classes of warnings, which thus fails the build.
1393 Run `configure` with `--disable-warnings-as-errors` to turn of this behavior.
1394 (The warnings will still show, but not make the build fail.)
1395
1396 #### Problems with Incremental Rebuilds
1397
1398 Incremental rebuilds mean that when you modify part of the product, only the
1399 affected parts get rebuilt. While this works great in most cases, and
1400 significantly speed up the development process, from time to time complex
1401 interdependencies will result in an incorrect build result. This is the most
1402 common cause for unexpected build problems.
1403
1404 Here are a suggested list of things to try if you are having unexpected build
1405 problems. Each step requires more time than the one before, so try them in
1406 order. Most issues will be solved at step 1 or 2.
1407
1408 1. Make sure your repository is up-to-date
1409
1410 Run `hg pull -u` to make sure you have the latest changes.
1411
1412 2. Clean build results
1413
1414 The simplest way to fix incremental rebuild issues is to run `make clean`.
1415 This will remove all build results, but not the configuration or any build
1416 system support artifacts. In most cases, this will solve build errors
1417 resulting from incremental build mismatches.
1418
1419 3. Completely clean the build directory.
1420
1421 If this does not work, the next step is to run `make dist-clean`, or
1422 removing the build output directory (`$BUILD`). This will clean all
1423 generated output, including your configuration. You will need to re-run
1424 `configure` after this step. A good idea is to run `make
1425 print-configuration` before running `make dist-clean`, as this will print
1426 your current `configure` command line. Here's a way to do this:
1427
1428 ```
1429 make print-configuration > current-configuration
1430 make dist-clean
1431 bash configure $(cat current-configuration)
1432 make
1433 ```
1434
1435 4. Re-clone the Mercurial repository
1436
1437 Sometimes the Mercurial repository gets in a state that causes the product
1438 to be un-buildable. In such a case, the simplest solution is often the
1439 "sledgehammer approach": delete the entire repository, and re-clone it.
1440 If you have local changes, save them first to a different location using
1441 `hg export`.
1442
1443 ### Specific Build Issues
1444
1445 #### Clock Skew
1446
1447 If you get an error message like this:
1448 ```
1449 File 'xxx' has modification time in the future.
1450 Clock skew detected. Your build may be incomplete.
1451 ```
1452 then the clock on your build machine is out of sync with the timestamps on the
1453 source files. Other errors, apparently unrelated but in fact caused by the
1454 clock skew, can occur along with the clock skew warnings. These secondary
1455 errors may tend to obscure the fact that the true root cause of the problem is
1456 an out-of-sync clock.
1457
1458 If you see these warnings, reset the clock on the build machine, run `make
1459 clean` and restart the build.
1460
1461 #### Out of Memory Errors
1462
1463 On Solaris, you might get an error message like this:
1464 ```
1465 Trouble writing out table to disk
1466 ```
1467 To solve this, increase the amount of swap space on your build machine.
1468
1469 On Windows, you might get error messages like this:
1470 ```
1471 fatal error - couldn't allocate heap
1472 cannot create ... Permission denied
1473 spawn failed
1474 ```
1475 This can be a sign of a Cygwin problem. See the information about solving
1476 problems in the [Cygwin](#cygwin) section. Rebooting the computer might help
1477 temporarily.
1478
1479 ### Getting Help
1480
1481 If none of the suggestions in this document helps you, or if you find what you
1482 believe is a bug in the build system, please contact the Build Group by sending
1483 a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net).
1484 Please include the relevant parts of the configure and/or build log.
1485
1486 If you need general help or advice about developing for the JDK, you can also
1487 contact the Adoption Group. See the section on [Contributing to OpenJDK](
1488 #contributing-to-openjdk) for more information.
1489
1490 ## Hints and Suggestions for Advanced Users
1491
1492 ### Setting Up a Repository for Pushing Changes (defpath)
1493
1494 To help you prepare a proper push path for a Mercurial repository, there exists
1495 a useful tool known as [defpath](
1496 http://openjdk.java.net/projects/code-tools/defpath). It will help you setup a
1497 proper push path for pushing changes to the JDK.
1498
1499 Install the extension by cloning
1500 `http://hg.openjdk.java.net/code-tools/defpath` and updating your `.hgrc` file.
1501 Here's one way to do this:
1502
1503 ```
1504 cd ~
1505 mkdir hg-ext
1506 cd hg-ext
1507 hg clone http://hg.openjdk.java.net/code-tools/defpath
1508 cat << EOT >> ~/.hgrc
1509 [extensions]
1510 defpath=~/hg-ext/defpath/defpath.py
1511 EOT
1512 ```
1513
1514 You can now setup a proper push path using:
1515 ```
1516 hg defpath -d -u <your OpenJDK username>
1517 ```
1518
1519 ### Bash Completion
1520
1521 The `configure` and `make` commands tries to play nice with bash command-line
1522 completion (using `<tab>` or `<tab><tab>`). To use this functionality, make
1523 sure you enable completion in your `~/.bashrc` (see instructions for bash in
1524 your operating system).
1525
1526 Make completion will work out of the box, and will complete valid make targets.
1527 For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`.
1528
1529 The `configure` script can get completion for options, but for this to work you
1530 need to help `bash` on the way. The standard way of running the script, `bash
1531 configure`, will not be understood by bash completion. You need `configure` to
1532 be the command to run. One way to achieve this is to add a simple helper script
1533 to your path:
1534
1535 ```
1536 cat << EOT > /tmp/configure
1537 #!/bin/bash
1538 if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then
1539 echo >&2 "Abort: Trying to call configure helper recursively"
1540 exit 1
1541 fi
1542
1543 bash \$PWD/configure "\$@"
1544 EOT
1545 chmod +x /tmp/configure
1546 sudo mv /tmp/configure /usr/local/bin
1547 ```
1548
1549 Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`.
1550
1551 ### Using Multiple Configurations
1552
1553 You can have multiple configurations for a single source repository. When you
1554 create a new configuration, run `configure --with-conf-name=<name>` to create a
1555 configuration with the name `<name>`. Alternatively, you can create a directory
1556 under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd
1557 build/<name> && bash ../../configure`.
1558
1559 Then you can build that configuration using `make CONF_NAME=<name>` or `make
1560 CONF=<pattern>`, where `<pattern>` is a substring matching one or several
1561 configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will
1562 match *all* available configuration, so `make CONF= hotspot` will build the
1563 `hotspot` target for all configurations. Alternatively, you can execute `make`
1564 in the configuration directory, e.g. `cd build/<name> && make`.
1565
1566 ### Handling Reconfigurations
1567
1568 If you update the repository and part of the configure script has changed, the
1569 build system will force you to re-run `configure`.
1570
1571 Most of the time, you will be fine by running `configure` again with the same
1572 arguments as the last time, which can easily be performed by `make
1573 reconfigure`. To simplify this, you can use the `CONF_CHECK` make control
1574 variable, either as `make CONF_CHECK=auto`, or by setting an environment
1575 variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc`
1576 file, `make` will always run `reconfigure` automatically whenever the configure
1577 script has changed.
1578
1579 You can also use `CONF_CHECK=ignore` to skip the check for a needed configure
1580 update. This might speed up the build, but comes at the risk of an incorrect
1581 build result. This is only recommended if you know what you're doing.
1582
1583 From time to time, you will also need to modify the command line to `configure`
1584 due to changes. Use `make print-configure` to show the command line used for
1585 your current configuration.
1586
1587 ### Using Fine-Grained Make Targets
1588
1589 The default behavior for make is to create consistent and correct output, at
1590 the expense of build speed, if necessary.
1591
1592 If you are prepared to take some risk of an incorrect build, and know enough of
1593 the system to understand how things build and interact, you can speed up the
1594 build process considerably by instructing make to only build a portion of the
1595 product.
1596
1597 #### Building Individual Modules
1598
1599 The safe way to use fine-grained make targets is to use the module specific
1600 make targets. All source code in the JDK is organized so it belongs to a
1601 module, e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific
1602 module, by giving it as make target: `make jdk.jdwp.agent`. If the specified
1603 module depends on other modules (e.g. `java.base`), those modules will be built
1604 first.
1605
1606 You can also specify a set of modules, just as you can always specify a set of
1607 make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi
1608 jdk.crypto.ucrypto`
1609
1610 #### Building Individual Module Phases
1611
1612 The build process for each module is divided into separate phases. Not all
1613 modules need all phases. Which are needed depends on what kind of source code
1614 and other artifact the module consists of. The phases are:
1615
1616 * `gensrc` (Generate source code to compile)
1617 * `gendata` (Generate non-source code artifacts)
1618 * `copy` (Copy resource artifacts)
1619 * `java` (Compile Java code)
1620 * `launchers` (Compile native executables)
1621 * `libs` (Compile native libraries)
1622
1623 You can build only a single phase for a module by using the notation
1624 `$MODULE-$PHASE`. For instance, to build the `gensrc` phase for `java.base`,
1625 use `make java.base-gensrc`.
1626
1627 Note that some phases may depend on others, e.g. `java` depends on `gensrc` (if
1628 present). Make will build all needed prerequisites before building the
1629 requested phase.
1630
1631 #### Skipping the Dependency Check
1632
1633 When using an iterative development style with frequent quick rebuilds, the
1634 dependency check made by make can take up a significant portion of the time
1635 spent on the rebuild. In such cases, it can be useful to bypass the dependency
1636 check in make.
1637
1638 > **Note that if used incorrectly, this can lead to a broken build!**
1639
1640 To achieve this, append `-only` to the build target. For instance, `make
1641 jdk.jdwp.agent-java-only` will *only* build the `java` phase of the
1642 `jdk.jdwp.agent` module. If the required dependencies are not present, the
1643 build can fail. On the other hand, the execution time measures in milliseconds.
1644
1645 A useful pattern is to build the first time normally (e.g. `make
1646 jdk.jdwp.agent`) and then on subsequent builds, use the `-only` make target.
1647
1648 #### Rebuilding Part of java.base (JDK\_FILTER)
1649
1650 If you are modifying files in `java.base`, which is the by far largest module
1651 in the JDK, then you need to rebuild all those files whenever a single file has
1652 changed. (This inefficiency will hopefully be addressed in JDK 10.)
1653
1654 As a hack, you can use the make control variable `JDK_FILTER` to specify a
1655 pattern that will be used to limit the set of files being recompiled. For
1656 instance, `make java.base JDK_FILTER=javax/crypto` (or, to combine methods,
1657 `make java.base-java-only JDK_FILTER=javax/crypto`) will limit the compilation
1658 to files in the `javax.crypto` package.
1659
1660 ### Learn About Mercurial
1661
1662 To become an efficient JDK developer, it is recommended that you invest in
1663 learning Mercurial properly. Here are some links that can get you started:
1664
1665 * [Mercurial for git users](http://www.mercurial-scm.org/wiki/GitConcepts)
1666 * [The official Mercurial tutorial](http://www.mercurial-scm.org/wiki/Tutorial)
1667 * [hg init](http://hginit.com/)
1668 * [Mercurial: The Definitive Guide](http://hgbook.red-bean.com/read/)
1669
1670 ## Understanding the Build System
1671
1672 This section will give you a more technical description on the details of the
1673 build system.
1674
1675 ### Configurations
1676
1677 The build system expects to find one or more configuration. These are
1678 technically defined by the `spec.gmk` in a subdirectory to the `build`
1679 subdirectory. The `spec.gmk` file is generated by `configure`, and contains in
1680 principle the configuration (directly or by files included by `spec.gmk`).
1681
1682 You can, in fact, select a configuration to build by pointing to the `spec.gmk`
1683 file with the `SPEC` make control variable, e.g. `make SPEC=$BUILD/spec.gmk`.
1684 While this is not the recommended way to call `make` as a user, it is what is
1685 used under the hood by the build system.
1686
1687 ### Build Output Structure
1688
1689 The build output for a configuration will end up in `build/<configuration
1690 name>`, which we refer to as `$BUILD` in this document. The `$BUILD` directory
1691 contains the following important directories:
1692
1693 ```
1694 buildtools/
1695 configure-support/
1696 hotspot/
1697 images/
1698 jdk/
1699 make-support/
1700 support/
1701 test-results/
1702 test-support/
1703 ```
1704
1705 This is what they are used for:
1706
1707 * `images`: This is the directory were the output of the `*-image` make
1708 targets end up. For instance, `make jdk-image` ends up in `images/jdk`.
1709
1710 * `jdk`: This is the "exploded image". After `make jdk`, you will be able to
1711 launch the newly built JDK by running `$BUILD/jdk/bin/java`.
1712
1713 * `test-results`: This directory contains the results from running tests.
1714
1715 * `support`: This is an area for intermediate files needed during the build,
1716 e.g. generated source code, object files and class files. Some noteworthy
1717 directories in `support` is `gensrc`, which contains the generated source
1718 code, and the `modules_*` directories, which contains the files in a
1719 per-module hierarchy that will later be collapsed into the `jdk` directory
1720 of the exploded image.
1721
1722 * `buildtools`: This is an area for tools compiled for the build platform
1723 that are used during the rest of the build.
1724
1725 * `hotspot`: This is an area for intermediate files needed when building
1726 hotspot.
1727
1728 * `configure-support`, `make-support` and `test-support`: These directories
1729 contain files that are needed by the build system for `configure`, `make`
1730 and for running tests.
1731
1732 ### Fixpath
1733
1734 Windows path typically look like `C:\User\foo`, while Unix paths look like
1735 `/home/foo`. Tools with roots from Unix often experience issues related to this
1736 mismatch when running on Windows.
1737
1738 In the JDK build, we always use Unix paths internally, and only just before
1739 calling a tool that does not understand Unix paths do we convert them to
1740 Windows paths.
1741
1742 This conversion is done by the `fixpath` tool, which is a small wrapper that
1743 modifies unix-style paths to Windows-style paths in command lines. Fixpath is
1744 compiled automatically by `configure`.
1745
1746 ### Native Debug Symbols
1747
1748 Native libraries and executables can have debug symbol (and other debug
1749 information) associated with them. How this works is very much platform
1750 dependent, but a common problem is that debug symbol information takes a lot of
1751 disk space, but is rarely needed by the end user.
1752
1753 The JDK supports different methods on how to handle debug symbols. The
1754 method used is selected by `--with-native-debug-symbols`, and available methods
1755 are `none`, `internal`, `external`, `zipped`.
1756
1757 * `none` means that no debug symbols will be generated during the build.
1758
1759 * `internal` means that debug symbols will be generated during the build, and
1760 they will be stored in the generated binary.
1761
1762 * `external` means that debug symbols will be generated during the build, and
1763 after the compilation, they will be moved into a separate `.debuginfo` file.
1764 (This was previously known as FDS, Full Debug Symbols).
1765
1766 * `zipped` is like `external`, but the .debuginfo file will also be zipped
1767 into a `.diz` file.
1768
1769 When building for distribution, `zipped` is a good solution. Binaries built
1770 with `internal` is suitable for use by developers, since they facilitate
1771 debugging, but should be stripped before distributed to end users.
1772
1773 ### Autoconf Details
1774
1775 The `configure` script is based on the autoconf framework, but in some details
1776 deviate from a normal autoconf `configure` script.
1777
1778 The `configure` script in the top level directory of the JDK is just a thin
1779 wrapper that calls `make/autoconf/configure`. This in turn will run `autoconf`
1780 to create the runnable (generated) configure script, as
1781 `.build/generated-configure.sh`. Apart from being responsible for the
1782 generation of the runnable script, the `configure` script also provides
1783 functionality that is not easily expressed in the normal Autoconf framework. As
1784 part of this functionality, the generated script is called.
1785
1786 The build system will detect if the Autoconf source files have changed, and
1787 will trigger a regeneration of the generated script if needed. You can also
1788 manually request such an update by `bash configure autogen`.
1789
1790 In previous versions of the JDK, the generated script was checked in at
1791 `make/autoconf/generated-configure.sh`. This is no longer the case.
1792
1793 ### Developing the Build System Itself
1794
1795 This section contains a few remarks about how to develop for the build system
1796 itself. It is not relevant if you are only making changes in the product source
1797 code.
1798
1799 While technically using `make`, the make source files of the JDK does not
1800 resemble most other Makefiles. Instead of listing specific targets and actions
1801 (perhaps using patterns), the basic modus operandi is to call a high-level
1802 function (or properly, macro) from the API in `make/common`. For instance, to
1803 compile all classes in the `jdk.internal.foo` package in the `jdk.foo` module,
1804 a call like this would be made:
1805
1806 ```
1807 $(eval $(call SetupJavaCompilation, BUILD_FOO_CLASSES, \
1808 SETUP := GENERATE_OLDBYTECODE, \
1809 SRC := $(TOPDIR)/src/jkd.foo/share/classes, \
1810 INCLUDES := jdk/internal/foo, \
1811 BIN := $(SUPPORT_OUTPUTDIR)/foo_classes, \
1812 ))
1813 ```
1814
1815 By encapsulating and expressing the high-level knowledge of *what* should be
1816 done, rather than *how* it should be done (as is normal in Makefiles), we can
1817 build a much more powerful and flexible build system.
1818
1819 Correct dependency tracking is paramount. Sloppy dependency tracking will lead
1820 to improper parallelization, or worse, race conditions.
1821
1822 To test for/debug race conditions, try running `make JOBS=1` and `make
1823 JOBS=100` and see if it makes any difference. (It shouldn't).
1824
1825 To compare the output of two different builds and see if, and how, they differ,
1826 run `$BUILD1/compare.sh -o $BUILD2`, where `$BUILD1` and `$BUILD2` are the two
1827 builds you want to compare.
1828
1829 To automatically build two consecutive versions and compare them, use
1830 `COMPARE_BUILD`. The value of `COMPARE_BUILD` is a set of variable=value
1831 assignments, like this:
1832 ```
1833 make COMPARE_BUILD=CONF=--enable-new-hotspot-feature:MAKE=hotspot
1834 ```
1835 See `make/InitSupport.gmk` for details on how to use `COMPARE_BUILD`.
1836
1837 To analyze build performance, run with `LOG=trace` and check `$BUILD/build-trace-time.log`.
1838 Use `JOBS=1` to avoid parallelism.
1839
1840 Please check that you adhere to the [Code Conventions for the Build System](
1841 http://openjdk.java.net/groups/build/doc/code-conventions.html) before
1842 submitting patches.
1843
1844 ## Contributing to the JDK
1845
1846 So, now you've built your JDK, and made your first patch, and want to
1847 contribute it back to the OpenJDK Community.
1848
1849 First of all: Thank you! We gladly welcome your contribution.
1850 However, please bear in mind that the JDK is a massive project, and we must ask
1851 you to follow our rules and guidelines to be able to accept your contribution.
1852
1853 The official place to start is the ['How to contribute' page](
1854 http://openjdk.java.net/contribute/). There is also an official (but somewhat
1855 outdated and skimpy on details) [Developer's Guide](
1856 http://openjdk.java.net/guide/).
1857
1858 If this seems overwhelming to you, the Adoption Group is there to help you! A
1859 good place to start is their ['New Contributor' page](
1860 https://wiki.openjdk.java.net/display/Adoption/New+Contributor), or start
1861 reading the comprehensive [Getting Started Kit](
1862 https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/en/). The
1863 Adoption Group will also happily answer any questions you have about
1864 contributing. Contact them by [mail](
1865 http://mail.openjdk.java.net/mailman/listinfo/adoption-discuss) or [IRC](
1866 http://openjdk.java.net/irc/).
1867
1868 ---
1869 # Override styles from the base CSS file that are not ideal for this document.
1870 header-includes:
1871 - '<style type="text/css">pre, code, tt { color: #1d6ae5; }</style>'
1872 ---