1 % Building the JDK
2
3 ## TL;DR (Instructions for the Impatient)
4
5 If you are eager to try out building the JDK, these simple steps works most of
6 the time. They assume that you have installed Mercurial (and Cygwin if running
7 on Windows) and cloned the top-level JDK repository that you want to build.
8
9 1. [Get the complete source code](#getting-the-source-code): \
10 `hg clone http://hg.openjdk.java.net/jdk/jdk`
11
12 2. [Run configure](#running-configure): \
13 `bash configure`
14
15 If `configure` fails due to missing dependencies (to either the
16 [toolchain](#native-compiler-toolchain-requirements), [build tools](
17 #build-tools-requirements), [external libraries](
18 #external-library-requirements) or the [boot JDK](#boot-jdk-requirements)),
19 most of the time it prints a suggestion on how to resolve the situation on
20 your platform. Follow the instructions, and try running `bash configure`
21 again.
22
23 3. [Run make](#running-make): \
24 `make images`
25
26 4. Verify your newly built JDK: \
27 `./build/*/images/jdk/bin/java -version`
28
29 5. [Run basic tests](##running-tests): \
30 `make run-test-tier1`
31
32 If any of these steps failed, or if you want to know more about build
33 requirements or build functionality, please continue reading this document.
34
35 ## Introduction
36
37 The JDK is a complex software project. Building it requires a certain amount of
38 technical expertise, a fair number of dependencies on external software, and
39 reasonably powerful hardware.
40
41 If you just want to use the JDK and not build it yourself, this document is not
42 for you. See for instance [OpenJDK installation](
43 http://openjdk.java.net/install) for some methods of installing a prebuilt
44 JDK.
45
46 ## Getting the Source Code
47
48 Make sure you are getting the correct version. As of JDK 10, the source is no
49 longer split into separate repositories so you only need to clone one single
50 repository. At the [OpenJDK Mercurial server](http://hg.openjdk.java.net/) you
51 can see a list of all available repositories. If you want to build an older version,
52 e.g. JDK 8, it is recommended that you get the `jdk8u` forest, which contains
53 incremental updates, instead of the `jdk8` forest, which was frozen at JDK 8 GA.
54
55 If you are new to Mercurial, a good place to start is the [Mercurial Beginner's
56 Guide](http://www.mercurial-scm.org/guide). The rest of this document assumes a
57 working knowledge of Mercurial.
58
59 ### Special Considerations
60
61 For a smooth building experience, it is recommended that you follow these rules
62 on where and how to check out the source code.
63
64 * Do not check out the source code in a path which contains spaces. Chances
65 are the build will not work. This is most likely to be an issue on Windows
66 systems.
67
68 * Do not check out the source code in a path which has a very long name or is
69 nested many levels deep. Chances are you will hit an OS limitation during
70 the build.
71
72 * Put the source code on a local disk, not a network share. If possible, use
73 an SSD. The build process is very disk intensive, and having slow disk
74 access will significantly increase build times. If you need to use a
75 network share for the source code, see below for suggestions on how to keep
76 the build artifacts on a local disk.
77
78 * On Windows, extra care must be taken to make sure the [Cygwin](#cygwin)
79 environment is consistent. It is recommended that you follow this
80 procedure:
81
82 * Create the directory that is going to contain the top directory of the
83 JDK clone by using the `mkdir` command in the Cygwin bash shell.
84 That is, do *not* create it using Windows Explorer. This will ensure
85 that it will have proper Cygwin attributes, and that it's children will
86 inherit those attributes.
87
88 * Do not put the JDK clone in a path under your Cygwin home
89 directory. This is especially important if your user name contains
90 spaces and/or mixed upper and lower case letters.
91
92 * Clone the JDK repository using the Cygwin command line `hg` client
93 as instructed in this document. That is, do *not* use another Mercurial
94 client such as TortoiseHg.
95
96 Failure to follow this procedure might result in hard-to-debug build
97 problems.
98
99 ## Build Hardware Requirements
100
101 The JDK is a massive project, and require machines ranging from decent to
102 powerful to be able to build in a reasonable amount of time, or to be able to
103 complete a build at all.
104
105 We *strongly* recommend usage of an SSD disk for the build, since disk speed is
106 one of the limiting factors for build performance.
107
108 ### Building on x86
109
110 At a minimum, a machine with 2-4 cores is advisable, as well as 2-4 GB of RAM.
111 (The more cores to use, the more memory you need.) At least 6 GB of free disk
112 space is required (8 GB minimum for building on Solaris).
113
114 Even for 32-bit builds, it is recommended to use a 64-bit build machine, and
115 instead create a 32-bit target using `--with-target-bits=32`.
116
117 ### Building on sparc
118
119 At a minimum, a machine with 4 cores is advisable, as well as 4 GB of RAM. (The
120 more cores to use, the more memory you need.) At least 8 GB of free disk space
121 is required.
122
123 ### Building on aarch64
124
125 At a minimum, a machine with 8 cores is advisable, as well as 8 GB of RAM.
126 (The more cores to use, the more memory you need.) At least 6 GB of free disk
127 space is required.
128
129 If you do not have access to sufficiently powerful hardware, it is also
130 possible to use [cross-compiling](#cross-compiling).
131
132 ### Building on 32-bit arm
133
134 This is not recommended. Instead, see the section on [Cross-compiling](
135 #cross-compiling).
136
137 ## Operating System Requirements
138
139 The mainline JDK project supports Linux, Solaris, macOS, AIX and Windows.
140 Support for other operating system, e.g. BSD, exists in separate "port"
141 projects.
142
143 In general, the JDK can be built on a wide range of versions of these operating
144 systems, but the further you deviate from what is tested on a daily basis, the
145 more likely you are to run into problems.
146
147 This table lists the OS versions used by Oracle when building the JDK. Such
148 information is always subject to change, but this table is up to date at the
149 time of writing.
150
151 Operating system Vendor/version used
152 ----------------- -------------------------------------------------------
153 Linux Oracle Enterprise Linux 6.4 / 7.1 (using kernel 3.8.13)
154 Solaris Solaris 11.1 SRU 21.4.1 / 11.2 SRU 5.5
155 macOS Mac OS X 10.9 (Mavericks) / 10.10 (Yosemite)
156 Windows Windows Server 2012 R2
157
158 The double version numbers for Linux, Solaris and macOS is due to the hybrid
159 model used at Oracle, where header files and external libraries from an older
160 version are used when building on a more modern version of the OS.
161
162 The Build Group has a wiki page with [Supported Build Platforms](
163 https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms). From
164 time to time, this is updated by contributors to list successes or failures of
165 building on different platforms.
166
167 ### Windows
168
169 Windows XP is not a supported platform, but all newer Windows should be able to
170 build the JDK.
171
172 On Windows, it is important that you pay attention to the instructions in the
173 [Special Considerations](#special-considerations).
174
175 Windows is the only non-POSIX OS supported by the JDK, and as such, requires
176 some extra care. A POSIX support layer is required to build on Windows.
177 Currently, the only supported such layer is Cygwin. (Msys is no longer
178 supported due to a too old bash; msys2 and the new Windows Subsystem for Linux
179 (WSL) would likely be possible to support in a future version but that would
180 require effort to implement.)
181
182 Internally in the build system, all paths are represented as Unix-style paths,
183 e.g. `/cygdrive/c/hg/jdk9/Makefile` rather than `C:\hg\jdk9\Makefile`. This
184 rule also applies to input to the build system, e.g. in arguments to
185 `configure`. So, use `--with-msvcr-dll=/cygdrive/c/msvcr100.dll` rather than
186 `--with-msvcr-dll=c:\msvcr100.dll`. For details on this conversion, see the section
187 on [Fixpath](#fixpath).
188
189 #### Cygwin
190
191 A functioning [Cygwin](http://www.cygwin.com/) environment is thus required for
192 building the JDK on Windows. If you have a 64-bit OS, we strongly recommend
193 using the 64-bit version of Cygwin.
194
195 **Note:** Cygwin has a model of continuously updating all packages without any
196 easy way to install or revert to a specific version of a package. This means
197 that whenever you add or update a package in Cygwin, you might (inadvertently)
198 update tools that are used by the JDK build process, and that can cause
199 unexpected build problems.
200
201 The JDK requires GNU Make 4.0 or greater on Windows. This is usually not a
202 problem, since Cygwin currently only distributes GNU Make at a version above
203 4.0.
204
205 Apart from the basic Cygwin installation, the following packages must also be
206 installed:
207
208 * `autoconf`
209 * `make`
210 * `zip`
211 * `unzip`
212
213 Often, you can install these packages using the following command line:
214 ```
215 <path to Cygwin setup>/setup-x86_64 -q -P autoconf -P make -P unzip -P zip
216 ```
217
218 Unfortunately, Cygwin can be unreliable in certain circumstances. If you
219 experience build tool crashes or strange issues when building on Windows,
220 please check the Cygwin FAQ on the ["BLODA" list](
221 https://cygwin.com/faq/faq.html#faq.using.bloda) and the section on [fork()
222 failures](https://cygwin.com/faq/faq.html#faq.using.fixing-fork-failures).
223
224 ### Solaris
225
226 See `make/devkit/solaris11.1-package-list.txt` for a list of recommended
227 packages to install when building on Solaris. The versions specified in this
228 list is the versions used by the daily builds at Oracle, and is likely to work
229 properly.
230
231 Older versions of Solaris shipped a broken version of `objcopy`. At least
232 version 2.21.1 is needed, which is provided by Solaris 11 Update 1. Objcopy is
233 needed if you want to have external debug symbols. Please make sure you are
234 using at least version 2.21.1 of objcopy, or that you disable external debug
235 symbols.
236
237 ### macOS
238
239 Apple is using a quite aggressive scheme of pushing OS updates, and coupling
240 these updates with required updates of Xcode. Unfortunately, this makes it
241 difficult for a project such as the JDK to keep pace with a continuously updated
242 machine running macOS. See the section on [Apple Xcode](#apple-xcode) on some
243 strategies to deal with this.
244
245 It is recommended that you use at least Mac OS X 10.13 (High Sierra). At the time
246 of writing, the JDK has been successfully compiled on macOS 10.12 (Sierra).
247
248 The standard macOS environment contains the basic tooling needed to build, but
249 for external libraries a package manager is recommended. The JDK uses
250 [homebrew](https://brew.sh/) in the examples, but feel free to use whatever
251 manager you want (or none).
252
253 ### Linux
254
255 It is often not much problem to build the JDK on Linux. The only general advice
256 is to try to use the compilers, external libraries and header files as provided
257 by your distribution.
258
259 The basic tooling is provided as part of the core operating system, but you
260 will most likely need to install developer packages.
261
262 For apt-based distributions (Debian, Ubuntu, etc), try this:
263 ```
264 sudo apt-get install build-essential
265 ```
266
267 For rpm-based distributions (Fedora, Red Hat, etc), try this:
268 ```
269 sudo yum groupinstall "Development Tools"
270 ```
271
272 ### AIX
273
274 The regular builds by SAP is using AIX version 7.1, but AIX 5.3 is also
275 supported. See the [OpenJDK PowerPC Port Status Page](
276 http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details.
277
278 ## Native Compiler (Toolchain) Requirements
279
280 Large portions of the JDK consists of native code, that needs to be compiled to
281 be able to run on the target platform. In theory, toolchain and operating
282 system should be independent factors, but in practice there's more or less a
283 one-to-one correlation between target operating system and toolchain.
284
285 Operating system Supported toolchain
286 ------------------ -------------------------
287 Linux gcc, clang
288 macOS Apple Xcode (using clang)
289 Solaris Oracle Solaris Studio
290 AIX IBM XL C/C++
291 Windows Microsoft Visual Studio
292
293 Please see the individual sections on the toolchains for version
294 recommendations. As a reference, these versions of the toolchains are used, at
295 the time of writing, by Oracle for the daily builds of the JDK. It should be
296 possible to compile the JDK with both older and newer versions, but the closer
297 you stay to this list, the more likely you are to compile successfully without
298 issues.
299
300 Operating system Toolchain version
301 ------------------ -------------------------------------------------------
302 Linux gcc 7.3.0
303 macOS Apple Xcode 9.4 (using clang 9.1.0)
304 Solaris Oracle Solaris Studio 12.4 (with compiler version 5.13)
305 Windows Microsoft Visual Studio 2017 update 15.5.5
306
307 ### gcc
308
309 The minimum accepted version of gcc is 4.8. Older versions will generate a warning
310 by `configure` and are unlikely to work.
311
312 The JDK is currently known to be able to compile with at least version 7.4 of
313 gcc.
314
315 In general, any version between these two should be usable.
316
317 ### clang
318
319 The minimum accepted version of clang is 3.2. Older versions will not be
320 accepted by `configure`.
321
322 To use clang instead of gcc on Linux, use `--with-toolchain-type=clang`.
323
324 ### Apple Xcode
325
326 The oldest supported version of Xcode is 8.
327
328 You will need the Xcode command lines developers tools to be able to build
329 the JDK. (Actually, *only* the command lines tools are needed, not the IDE.)
330 The simplest way to install these is to run:
331 ```
332 xcode-select --install
333 ```
334
335 It is advisable to keep an older version of Xcode for building the JDK when
336 updating Xcode. This [blog page](
337 http://iosdevelopertips.com/xcode/install-multiple-versions-of-xcode.html) has
338 good suggestions on managing multiple Xcode versions. To use a specific version
339 of Xcode, use `xcode-select -s` before running `configure`, or use
340 `--with-toolchain-path` to point to the version of Xcode to use, e.g.
341 `configure --with-toolchain-path=/Applications/Xcode8.app/Contents/Developer/usr/bin`
342
343 If you have recently (inadvertently) updated your OS and/or Xcode version, and
344 the JDK can no longer be built, please see the section on [Problems with the
345 Build Environment](#problems-with-the-build-environment), and [Getting
346 Help](#getting-help) to find out if there are any recent, non-merged patches
347 available for this update.
348
349 ### Oracle Solaris Studio
350
351 The minimum accepted version of the Solaris Studio compilers is 5.13
352 (corresponding to Solaris Studio 12.4). Older versions will not be accepted by
353 configure.
354
355 The Solaris Studio installation should contain at least these packages:
356
357 Package Version
358 -------------------------------------------------- -------------
359 developer/solarisstudio-124/backend 12.4-1.0.6.0
360 developer/solarisstudio-124/c++ 12.4-1.0.10.0
361 developer/solarisstudio-124/cc 12.4-1.0.4.0
362 developer/solarisstudio-124/library/c++-libs 12.4-1.0.10.0
363 developer/solarisstudio-124/library/math-libs 12.4-1.0.0.1
364 developer/solarisstudio-124/library/studio-gccrt 12.4-1.0.0.1
365 developer/solarisstudio-124/studio-common 12.4-1.0.0.1
366 developer/solarisstudio-124/studio-ja 12.4-1.0.0.1
367 developer/solarisstudio-124/studio-legal 12.4-1.0.0.1
368 developer/solarisstudio-124/studio-zhCN 12.4-1.0.0.1
369
370 Compiling with Solaris Studio can sometimes be finicky. This is the exact
371 version used by Oracle, which worked correctly at the time of writing:
372 ```
373 $ cc -V
374 cc: Sun C 5.13 SunOS_i386 2014/10/20
375 $ CC -V
376 CC: Sun C++ 5.13 SunOS_i386 151846-10 2015/10/30
377 ```
378
379 ### Microsoft Visual Studio
380
381 The minimum accepted version of Visual Studio is 2010. Older versions will not
382 be accepted by `configure`. The maximum accepted version of Visual Studio is
383 2017. Versions older than 2017 are unlikely to continue working for long.
384
385 If you have multiple versions of Visual Studio installed, `configure` will by
386 default pick the latest. You can request a specific version to be used by
387 setting `--with-toolchain-version`, e.g. `--with-toolchain-version=2015`.
388
389 If you get `LINK: fatal error LNK1123: failure during conversion to COFF: file
390 invalid` when building using Visual Studio 2010, you have encountered
391 [KB2757355](http://support.microsoft.com/kb/2757355), a bug triggered by a
392 specific installation order. However, the solution suggested by the KB article
393 does not always resolve the problem. See [this stackoverflow discussion](
394 https://stackoverflow.com/questions/10888391) for other suggestions.
395
396 ### IBM XL C/C++
397
398 The regular builds by SAP is using version 12.1, described as `IBM XL C/C++ for
399 AIX, V12.1 (5765-J02, 5725-C72) Version: 12.01.0000.0017`.
400
401 See the [OpenJDK PowerPC Port Status Page](
402 http://cr.openjdk.java.net/~simonis/ppc-aix-port) for details.
403
404 ## Boot JDK Requirements
405
406 Paradoxically, building the JDK requires a pre-existing JDK. This is called the
407 "boot JDK". The boot JDK does not, however, have to be a JDK built directly from
408 the source code available in the OpenJDK Community. If you are porting the JDK
409 to a new platform, chances are that there already exists another JDK for that
410 platform that is usable as boot JDK.
411
412 The rule of thumb is that the boot JDK for building JDK major version *N*
413 should be a JDK of major version *N-1*, so for building JDK 9 a JDK 8 would be
414 suitable as boot JDK. However, the JDK should be able to "build itself", so an
415 up-to-date build of the current JDK source is an acceptable alternative. If
416 you are following the *N-1* rule, make sure you've got the latest update
417 version, since JDK 8 GA might not be able to build JDK 9 on all platforms.
418
419 Early in the release cycle, version *N-1* may not yet have been released. In
420 that case, the preferred boot JDK will be version *N-2* until version *N-1*
421 is available.
422
423 If the boot JDK is not automatically detected, or the wrong JDK is picked, use
424 `--with-boot-jdk` to point to the JDK to use.
425
426 ### Getting JDK binaries
427
428 JDK binaries for Linux, Windows and macOS can be downloaded from
429 [jdk.java.net](http://jdk.java.net). An alternative is to download the
430 [Oracle JDK](http://www.oracle.com/technetwork/java/javase/downloads). Another
431 is the [Adopt OpenJDK Project](https://adoptopenjdk.net/), which publishes
432 experimental prebuilt binaries for various platforms.
433
434 On Linux you can also get a JDK from the Linux distribution. On apt-based
435 distros (like Debian and Ubuntu), `sudo apt-get install openjdk-<VERSION>-jdk`
436 is typically enough to install a JDK \<VERSION\>. On rpm-based distros (like
437 Fedora and Red Hat), try `sudo yum install java-<VERSION>-openjdk-devel`.
438
439 ## External Library Requirements
440
441 Different platforms require different external libraries. In general, libraries
442 are not optional - that is, they are either required or not used.
443
444 If a required library is not detected by `configure`, you need to provide the
445 path to it. There are two forms of the `configure` arguments to point to an
446 external library: `--with-<LIB>=<path>` or `--with-<LIB>-include=<path to
447 include> --with-<LIB>-lib=<path to lib>`. The first variant is more concise,
448 but require the include files an library files to reside in a default hierarchy
449 under this directory. In most cases, it works fine.
450
451 As a fallback, the second version allows you to point to the include directory
452 and the lib directory separately.
453
454 ### FreeType
455
456 FreeType2 from [The FreeType Project](http://www.freetype.org/) is not required
457 on any platform. The exception is on Unix-based platforms when configuring such
458 that the build artifacts will reference a system installed library,
459 rather than bundling the JDK’s own copy.
460
461 * To install on an apt-based Linux, try running `sudo apt-get install
462 libfreetype6-dev`.
463 * To install on an rpm-based Linux, try running `sudo yum install
464 freetype-devel`.
465 * To install on Solaris, try running `pkg install system/library/freetype-2`.
466
467 Use `--with-freetype-include=<path>` and `--with-freetype-lib=<path>`
468 if `configure` does not automatically locate the platform FreeType files.
469
470 ### CUPS
471
472 CUPS, [Common UNIX Printing System](http://www.cups.org) header files are
473 required on all platforms, except Windows. Often these files are provided by
474 your operating system.
475
476 * To install on an apt-based Linux, try running `sudo apt-get install
477 libcups2-dev`.
478 * To install on an rpm-based Linux, try running `sudo yum install
479 cups-devel`.
480 * To install on Solaris, try running `pkg install print/cups`.
481
482 Use `--with-cups=<path>` if `configure` does not properly locate your CUPS
483 files.
484
485 ### X11
486
487 Certain [X11](http://www.x.org/) libraries and include files are required on
488 Linux and Solaris.
489
490 * To install on an apt-based Linux, try running `sudo apt-get install
491 libx11-dev libxext-dev libxrender-dev libxrandr-dev libxtst-dev libxt-dev`.
492 * To install on an rpm-based Linux, try running `sudo yum install
493 libXtst-devel libXt-devel libXrender-devel libXrandr-devel libXi-devel`.
494 * To install on Solaris, try running `pkg install x11/header/x11-protocols
495 x11/library/libice x11/library/libpthread-stubs x11/library/libsm
496 x11/library/libx11 x11/library/libxau x11/library/libxcb
497 x11/library/libxdmcp x11/library/libxevie x11/library/libxext
498 x11/library/libxrender x11/library/libxrandr x11/library/libxscrnsaver
499 x11/library/libxtst x11/library/toolkit/libxt`.
500
501 Use `--with-x=<path>` if `configure` does not properly locate your X11 files.
502
503 ### ALSA
504
505 ALSA, [Advanced Linux Sound Architecture](https://www.alsa-project.org/) is
506 required on Linux. At least version 0.9.1 of ALSA is required.
507
508 * To install on an apt-based Linux, try running `sudo apt-get install
509 libasound2-dev`.
510 * To install on an rpm-based Linux, try running `sudo yum install
511 alsa-lib-devel`.
512
513 Use `--with-alsa=<path>` if `configure` does not properly locate your ALSA
514 files.
515
516 ### libffi
517
518 libffi, the [Portable Foreign Function Interface Library](
519 http://sourceware.org/libffi) is required when building the Zero version of
520 Hotspot.
521
522 * To install on an apt-based Linux, try running `sudo apt-get install
523 libffi-dev`.
524 * To install on an rpm-based Linux, try running `sudo yum install
525 libffi-devel`.
526
527 Use `--with-libffi=<path>` if `configure` does not properly locate your libffi
528 files.
529
530 ### SoftFloat
531
532 [Berkeley SoftFloat-3](http://www.jhauser.us/arithmetic/SoftFloat.html)
533 can be used on ARM processors without FPU to slightly enhance
534 the arithmetic precision of some floating point operations. It is not
535 required, system softfp routines can be used without any problems.
536 The precision loss is extremely small, but it can be detected during JCK testing.
537
538 * To build the library, you will have to download its source and build it
539 for the target platform. To do so, take a look in its
540 `build/Linux-ARM-VFPv2-GCC` subdirectory.
541 * Alternatively,
542 [SoftFloat-3e for OpenJDK](https://github.com/ev3dev-lang-java/softfloat-openjdk)
543 repository provides a build script and a README for the process.
544
545 You can enable this library by specifying a library prefix
546 via `--with-sflt=<path>` or by specifying path to softfloat.a
547 via `--with-sflt-lib=<path>` and path to directory
548 containing softfloat.h via `--with-sflt-include=<path>`. You
549 will also need to specify path to the SoftFloat license file with
550 `--with-sflt-license=<path>`. If you want to use the prefix option, ensure that
551 `<prefix>/lib/softfloat.a`, `<prefix>/include/softfloat.h` and
552 `<prefix>/share/softfloat/softfloat.md` exist. However you can override
553 the defaults by using the options above.
554
555 If you do not enable this library, standard system libraries
556 will be used instead.
557
558 ## Build Tools Requirements
559
560 ### Autoconf
561
562 The JDK requires [Autoconf](http://www.gnu.org/software/autoconf) on all
563 platforms. At least version 2.69 is required.
564
565 * To install on an apt-based Linux, try running `sudo apt-get install
566 autoconf`.
567 * To install on an rpm-based Linux, try running `sudo yum install
568 autoconf`.
569 * To install on macOS, try running `brew install autoconf`.
570 * To install on Windows, try running `<path to Cygwin setup>/setup-x86_64 -q
571 -P autoconf`.
572
573 If `configure` has problems locating your installation of autoconf, you can
574 specify it using the `AUTOCONF` environment variable, like this:
575
576 ```
577 AUTOCONF=<path to autoconf> configure ...
578 ```
579
580 ### GNU Make
581
582 The JDK requires [GNU Make](http://www.gnu.org/software/make). No other flavors
583 of make are supported.
584
585 At least version 3.81 of GNU Make must be used. For distributions supporting
586 GNU Make 4.0 or above, we strongly recommend it. GNU Make 4.0 contains useful
587 functionality to handle parallel building (supported by `--with-output-sync`)
588 and speed and stability improvements.
589
590 Note that `configure` locates and verifies a properly functioning version of
591 `make` and stores the path to this `make` binary in the configuration. If you
592 start a build using `make` on the command line, you will be using the version
593 of make found first in your `PATH`, and not necessarily the one stored in the
594 configuration. This initial make will be used as "bootstrap make", and in a
595 second stage, the make located by `configure` will be called. Normally, this
596 will present no issues, but if you have a very old `make`, or a non-GNU Make
597 `make` in your path, this might cause issues.
598
599 If you want to override the default make found by `configure`, use the `MAKE`
600 configure variable, e.g. `configure MAKE=/opt/gnu/make`.
601
602 On Solaris, it is common to call the GNU version of make by using `gmake`.
603
604 ### GNU Bash
605
606 The JDK requires [GNU Bash](http://www.gnu.org/software/bash). No other shells
607 are supported.
608
609 At least version 3.2 of GNU Bash must be used.
610
611 ## Running Configure
612
613 To build the JDK, you need a "configuration", which consists of a directory
614 where to store the build output, coupled with information about the platform,
615 the specific build machine, and choices that affect how the JDK is built.
616
617 The configuration is created by the `configure` script. The basic invocation of
618 the `configure` script looks like this:
619
620 ```
621 bash configure [options]
622 ```
623
624 This will create an output directory containing the configuration and setup an
625 area for the build result. This directory typically looks like
626 `build/linux-x64-normal-server-release`, but the actual name depends on your
627 specific configuration. (It can also be set directly, see [Using Multiple
628 Configurations](#using-multiple-configurations)). This directory is referred to
629 as `$BUILD` in this documentation.
630
631 `configure` will try to figure out what system you are running on and where all
632 necessary build components are. If you have all prerequisites for building
633 installed, it should find everything. If it fails to detect any component
634 automatically, it will exit and inform you about the problem.
635
636 Some command line examples:
637
638 * Create a 32-bit build for Windows with FreeType2 in `C:\freetype-i586`:
639 ```
640 bash configure --with-freetype=/cygdrive/c/freetype-i586 --with-target-bits=32
641 ```
642
643 * Create a debug build with the `server` JVM and DTrace enabled:
644 ```
645 bash configure --enable-debug --with-jvm-variants=server --enable-dtrace
646 ```
647
648 ### Common Configure Arguments
649
650 Here follows some of the most common and important `configure` argument.
651
652 To get up-to-date information on *all* available `configure` argument, please
653 run:
654 ```
655 bash configure --help
656 ```
657
658 (Note that this help text also include general autoconf options, like
659 `--dvidir`, that is not relevant to the JDK. To list only JDK-specific
660 features, use `bash configure --help=short` instead.)
661
662 #### Configure Arguments for Tailoring the Build
663
664 * `--enable-debug` - Set the debug level to `fastdebug` (this is a shorthand
665 for `--with-debug-level=fastdebug`)
666 * `--with-debug-level=<level>` - Set the debug level, which can be `release`,
667 `fastdebug`, `slowdebug` or `optimized`. Default is `release`. `optimized`
668 is variant of `release` with additional Hotspot debug code.
669 * `--with-native-debug-symbols=<method>` - Specify if and how native debug
670 symbols should be built. Available methods are `none`, `internal`,
671 `external`, `zipped`. Default behavior depends on platform. See [Native
672 Debug Symbols](#native-debug-symbols) for more details.
673 * `--with-version-string=<string>` - Specify the version string this build
674 will be identified with.
675 * `--with-version-<part>=<value>` - A group of options, where `<part>` can be
676 any of `pre`, `opt`, `build`, `major`, `minor`, `security` or `patch`. Use
677 these options to modify just the corresponding part of the version string
678 from the default, or the value provided by `--with-version-string`.
679 * `--with-jvm-variants=<variant>[,<variant>...]` - Build the specified variant
680 (or variants) of Hotspot. Valid variants are: `server`, `client`,
681 `minimal`, `core`, `zero`, `custom`. Note that not all
682 variants are possible to combine in a single build.
683 * `--with-jvm-features=<feature>[,<feature>...]` - Use the specified JVM
684 features when building Hotspot. The list of features will be enabled on top
685 of the default list. For the `custom` JVM variant, this default list is
686 empty. A complete list of available JVM features can be found using `bash
687 configure --help`.
688 * `--with-target-bits=<bits>` - Create a target binary suitable for running
689 on a `<bits>` platform. Use this to create 32-bit output on a 64-bit build
690 platform, instead of doing a full cross-compile. (This is known as a
691 *reduced* build.)
692
693 On Linux, BSD and AIX, it is possible to override where Java by default
694 searches for runtime/JNI libraries. This can be useful in situations where
695 there is a special shared directory for system JNI libraries. This setting
696 can in turn be overriden at runtime by setting the `java.library.path` property.
697
698 * `--with-jni-libpath=<path>` - Use the specified path as a default
699 when searching for runtime libraries.
700
701 #### Configure Arguments for Native Compilation
702
703 * `--with-devkit=<path>` - Use this devkit for compilers, tools and resources
704 * `--with-sysroot=<path>` - Use this directory as sysroot
705 * `--with-extra-path=<path>[;<path>]` - Prepend these directories to the
706 default path when searching for all kinds of binaries
707 * `--with-toolchain-path=<path>[;<path>]` - Prepend these directories when
708 searching for toolchain binaries (compilers etc)
709 * `--with-extra-cflags=<flags>` - Append these flags when compiling JDK C
710 files
711 * `--with-extra-cxxflags=<flags>` - Append these flags when compiling JDK C++
712 files
713 * `--with-extra-ldflags=<flags>` - Append these flags when linking JDK
714 libraries
715
716 #### Configure Arguments for External Dependencies
717
718 * `--with-boot-jdk=<path>` - Set the path to the [Boot JDK](
719 #boot-jdk-requirements)
720 * `--with-freetype=<path>` - Set the path to [FreeType](#freetype)
721 * `--with-cups=<path>` - Set the path to [CUPS](#cups)
722 * `--with-x=<path>` - Set the path to [X11](#x11)
723 * `--with-alsa=<path>` - Set the path to [ALSA](#alsa)
724 * `--with-libffi=<path>` - Set the path to [libffi](#libffi)
725 * `--with-sflt=<path>` - Enable and set the path to [SoftFloat](#softfloat)
726 library.
727 * `--with-jtreg=<path>` - Set the path to JTReg. See [Running Tests](
728 #running-tests)
729
730 Certain third-party libraries used by the JDK (libjpeg, giflib, libpng, lcms
731 and zlib) are included in the JDK repository. The default behavior of the
732 JDK build is to use this version of these libraries, but they might be
733 replaced by an external version. To do so, specify `system` as the `<source>`
734 option in these arguments. (The default is `bundled`).
735
736 * `--with-libjpeg=<source>` - Use the specified source for libjpeg
737 * `--with-giflib=<source>` - Use the specified source for giflib
738 * `--with-libpng=<source>` - Use the specified source for libpng
739 * `--with-lcms=<source>` - Use the specified source for lcms
740 * `--with-zlib=<source>` - Use the specified source for zlib
741
742 On Linux, it is possible to select either static or dynamic linking of the C++
743 runtime. The default is static linking, with dynamic linking as fallback if the
744 static library is not found.
745
746 * `--with-stdc++lib=<method>` - Use the specified method (`static`, `dynamic`
747 or `default`) for linking the C++ runtime.
748
749 ### Configure Control Variables
750
751 It is possible to control certain aspects of `configure` by overriding the
752 value of `configure` variables, either on the command line or in the
753 environment.
754
755 Normally, this is **not recommended**. If used improperly, it can lead to a
756 broken configuration. Unless you're well versed in the build system, this is
757 hard to use properly. Therefore, `configure` will print a warning if this is
758 detected.
759
760 However, there are a few `configure` variables, known as *control variables*
761 that are supposed to be overriden on the command line. These are variables that
762 describe the location of tools needed by the build, like `MAKE` or `GREP`. If
763 any such variable is specified, `configure` will use that value instead of
764 trying to autodetect the tool. For instance, `bash configure
765 MAKE=/opt/gnumake4.0/bin/make`.
766
767 If a configure argument exists, use that instead, e.g. use `--with-jtreg`
768 instead of setting `JTREGEXE`.
769
770 Also note that, despite what autoconf claims, setting `CFLAGS` will not
771 accomplish anything. Instead use `--with-extra-cflags` (and similar for
772 `cxxflags` and `ldflags`).
773
774 ## Running Make
775
776 When you have a proper configuration, all you need to do to build the JDK is to
777 run `make`. (But see the warning at [GNU Make](#gnu-make) about running the
778 correct version of make.)
779
780 When running `make` without any arguments, the default target is used, which is
781 the same as running `make default` or `make jdk`. This will build a minimal (or
782 roughly minimal) set of compiled output (known as an "exploded image") needed
783 for a developer to actually execute the newly built JDK. The idea is that in an
784 incremental development fashion, when doing a normal make, you should only
785 spend time recompiling what's changed (making it purely incremental) and only
786 do the work that's needed to actually run and test your code.
787
788 The output of the exploded image resides in `$BUILD/jdk`. You can test the
789 newly built JDK like this: `$BUILD/jdk/bin/java -version`.
790
791 ### Common Make Targets
792
793 Apart from the default target, here are some common make targets:
794
795 * `hotspot` - Build all of hotspot (but only hotspot)
796 * `hotspot-<variant>` - Build just the specified jvm variant
797 * `images` or `product-images` - Build the JDK image
798 * `docs` or `docs-image` - Build the documentation image
799 * `test-image` - Build the test image
800 * `all` or `all-images` - Build all images (product, docs and test)
801 * `bootcycle-images` - Build images twice, second time with newly built JDK
802 (good for testing)
803 * `clean` - Remove all files generated by make, but not those generated by
804 configure
805 * `dist-clean` - Remove all files, including configuration
806
807 Run `make help` to get an up-to-date list of important make targets and make
808 control variables.
809
810 It is possible to build just a single module, a single phase, or a single phase
811 of a single module, by creating make targets according to these followin
812 patterns. A phase can be either of `gensrc`, `gendata`, `copy`, `java`,
813 `launchers`, `libs` or `rmic`. See [Using Fine-Grained Make Targets](
814 #using-fine-grained-make-targets) for more details about this functionality.
815
816 * `<phase>` - Build the specified phase and everything it depends on
817 * `<module>` - Build the specified module and everything it depends on
818 * `<module>-<phase>` - Compile the specified phase for the specified module
819 and everything it depends on
820
821 Similarly, it is possible to clean just a part of the build by creating make
822 targets according to these patterns:
823
824 * `clean-<outputdir>` - Remove the subdir in the output dir with the name
825 * `clean-<phase>` - Remove all build results related to a certain build
826 phase
827 * `clean-<module>` - Remove all build results related to a certain module
828 * `clean-<module>-<phase>` - Remove all build results related to a certain
829 module and phase
830
831 ### Make Control Variables
832
833 It is possible to control `make` behavior by overriding the value of `make`
834 variables, either on the command line or in the environment.
835
836 Normally, this is **not recommended**. If used improperly, it can lead to a
837 broken build. Unless you're well versed in the build system, this is hard to
838 use properly. Therefore, `make` will print a warning if this is detected.
839
840 However, there are a few `make` variables, known as *control variables* that
841 are supposed to be overriden on the command line. These make up the "make time"
842 configuration, as opposed to the "configure time" configuration.
843
844 #### General Make Control Variables
845
846 * `JOBS` - Specify the number of jobs to build with. See [Build
847 Performance](#build-performance).
848 * `LOG` - Specify the logging level and functionality. See [Checking the
849 Build Log File](#checking-the-build-log-file)
850 * `CONF` and `CONF_NAME` - Selecting the configuration(s) to use. See [Using
851 Multiple Configurations](#using-multiple-configurations)
852
853 #### Test Make Control Variables
854
855 These make control variables only make sense when running tests. Please see
856 [Testing the JDK](testing.html) for details.
857
858 * `TEST`
859 * `TEST_JOBS`
860 * `JTREG`
861 * `GTEST`
862
863 #### Advanced Make Control Variables
864
865 These advanced make control variables can be potentially unsafe. See [Hints and
866 Suggestions for Advanced Users](#hints-and-suggestions-for-advanced-users) and
867 [Understanding the Build System](#understanding-the-build-system) for details.
868
869 * `SPEC`
870 * `CONF_CHECK`
871 * `COMPARE_BUILD`
872 * `JDK_FILTER`
873
874 ## Running Tests
875
876 Most of the JDK tests are using the [JTReg](http://openjdk.java.net/jtreg)
877 test framework. Make sure that your configuration knows where to find your
878 installation of JTReg. If this is not picked up automatically, use the
879 `--with-jtreg=<path to jtreg home>` option to point to the JTReg framework.
880 Note that this option should point to the JTReg home, i.e. the top directory,
881 containing `lib/jtreg.jar` etc.
882
883 The [Adoption Group](https://wiki.openjdk.java.net/display/Adoption) provides
884 recent builds of jtreg [here](
885 https://adopt-openjdk.ci.cloudbees.com/job/jtreg/lastSuccessfulBuild/artifact).
886 Download the latest `.tar.gz` file, unpack it, and point `--with-jtreg` to the
887 `jtreg` directory that you just unpacked.
888
889 To execute the most basic tests (tier 1), use:
890 ```
891 make run-test-tier1
892 ```
893
894 For more details on how to run tests, please see the [Testing
895 the JDK](testing.html) document.
896
897 ## Cross-compiling
898
899 Cross-compiling means using one platform (the *build* platform) to generate
900 output that can ran on another platform (the *target* platform).
901
902 The typical reason for cross-compiling is that the build is performed on a more
903 powerful desktop computer, but the resulting binaries will be able to run on a
904 different, typically low-performing system. Most of the complications that
905 arise when building for embedded is due to this separation of *build* and
906 *target* systems.
907
908 This requires a more complex setup and build procedure. This section assumes
909 you are familiar with cross-compiling in general, and will only deal with the
910 particularities of cross-compiling the JDK. If you are new to cross-compiling,
911 please see the [external links at Wikipedia](
912 https://en.wikipedia.org/wiki/Cross_compiler#External_links) for a good start
913 on reading materials.
914
915 Cross-compiling the JDK requires you to be able to build both for the build
916 platform and for the target platform. The reason for the former is that we need
917 to build and execute tools during the build process, both native tools and Java
918 tools.
919
920 If all you want to do is to compile a 32-bit version, for the same OS, on a
921 64-bit machine, consider using `--with-target-bits=32` instead of doing a
922 full-blown cross-compilation. (While this surely is possible, it's a lot more
923 work and will take much longer to build.)
924
925 ### Cross compiling the easy way with OpenJDK devkits
926
927 The OpenJDK build system provides out-of-the box support for creating and using
928 so called devkits. A `devkit` is basically a collection of a cross-compiling
929 toolchain and a sysroot environment which can easily be used together with the
930 `--with-devkit` configure option to cross compile the OpenJDK. On Linux/x86_64,
931 the following command:
932 ```
933 bash configure --with-devkit=<devkit-path> --openjdk-target=ppc64-linux-gnu && make
934 ```
935
936 will configure and build OpenJDK for Linux/ppc64 assuming that `<devkit-path>`
937 points to a Linux/x86_64 to Linux/ppc64 devkit.
938
939 Devkits can be created from the `make/devkit` directory by executing:
940 ```
941 make [ TARGETS="<TARGET_TRIPLET>+" ] [ BASE_OS=<OS> ] [ BASE_OS_VERSION=<VER> ]
942 ```
943
944 where `TARGETS` contains one or more `TARGET_TRIPLET`s of the form
945 described in [section 3.4 of the GNU Autobook](
946 https://sourceware.org/autobook/autobook/autobook_17.html). If no
947 targets are given, a native toolchain for the current platform will be
948 created. Currently, at least the following targets are known to work:
949
950 Supported devkit targets
951 -------------------------
952 x86_64-linux-gnu
953 aarch64-linux-gnu
954 arm-linux-gnueabihf
955 ppc64-linux-gnu
956 ppc64le-linux-gnu
957 s390x-linux-gnu
958
959 `BASE_OS` must be one of "OEL6" for Oracle Enterprise Linux 6 or
960 "Fedora" (if not specified "OEL6" will be the default). If the base OS
961 is "Fedora" the corresponding Fedora release can be specified with the
962 help of the `BASE_OS_VERSION` option (with "27" as default version).
963 If the build is successful, the new devkits can be found in the
964 `build/devkit/result` subdirectory:
965 ```
966 cd make/devkit
967 make TARGETS="ppc64le-linux-gnu aarch64-linux-gnu" BASE_OS=Fedora BASE_OS_VERSION=21
968 ls -1 ../../build/devkit/result/
969 x86_64-linux-gnu-to-aarch64-linux-gnu
970 x86_64-linux-gnu-to-ppc64le-linux-gnu
971 ```
972
973 Notice that devkits are not only useful for targeting different build
974 platforms. Because they contain the full build dependencies for a
975 system (i.e. compiler and root file system), they can easily be used
976 to build well-known, reliable and reproducible build environments. You
977 can for example create and use a devkit with GCC 7.3 and a Fedora 12
978 sysroot environment (with glibc 2.11) on Ubuntu 14.04 (which doesn't
979 have GCC 7.3 by default) to produce OpenJDK binaries which will run on
980 all Linux systems with runtime libraries newer than the ones from
981 Fedora 12 (e.g. Ubuntu 16.04, SLES 11 or RHEL 6).
982
983 ### Boot JDK and Build JDK
984
985 When cross-compiling, make sure you use a boot JDK that runs on the *build*
986 system, and not on the *target* system.
987
988 To be able to build, we need a "Build JDK", which is a JDK built from the
989 current sources (that is, the same as the end result of the entire build
990 process), but able to run on the *build* system, and not the *target* system.
991 (In contrast, the Boot JDK should be from an older release, e.g. JDK 8 when
992 building JDK 9.)
993
994 The build process will create a minimal Build JDK for you, as part of building.
995 To speed up the build, you can use `--with-build-jdk` to `configure` to point
996 to a pre-built Build JDK. Please note that the build result is unpredictable,
997 and can possibly break in subtle ways, if the Build JDK does not **exactly**
998 match the current sources.
999
1000 ### Specifying the Target Platform
1001
1002 You *must* specify the target platform when cross-compiling. Doing so will also
1003 automatically turn the build into a cross-compiling mode. The simplest way to
1004 do this is to use the `--openjdk-target` argument, e.g.
1005 `--openjdk-target=arm-linux-gnueabihf`. or `--openjdk-target=aarch64-oe-linux`.
1006 This will automatically set the `--build`, `--host` and `--target` options for
1007 autoconf, which can otherwise be confusing. (In autoconf terminology, the
1008 "target" is known as "host", and "target" is used for building a Canadian
1009 cross-compiler.)
1010
1011 ### Toolchain Considerations
1012
1013 You will need two copies of your toolchain, one which generates output that can
1014 run on the target system (the normal, or *target*, toolchain), and one that
1015 generates output that can run on the build system (the *build* toolchain). Note
1016 that cross-compiling is only supported for gcc at the time being. The gcc
1017 standard is to prefix cross-compiling toolchains with the target denominator.
1018 If you follow this standard, `configure` is likely to pick up the toolchain
1019 correctly.
1020
1021 The *build* toolchain will be autodetected just the same way the normal
1022 *build*/*target* toolchain will be autodetected when not cross-compiling. If
1023 this is not what you want, or if the autodetection fails, you can specify a
1024 devkit containing the *build* toolchain using `--with-build-devkit` to
1025 `configure`, or by giving `BUILD_CC` and `BUILD_CXX` arguments.
1026
1027 It is often helpful to locate the cross-compilation tools, headers and
1028 libraries in a separate directory, outside the normal path, and point out that
1029 directory to `configure`. Do this by setting the sysroot (`--with-sysroot`) and
1030 appending the directory when searching for cross-compilations tools
1031 (`--with-toolchain-path`). As a compact form, you can also use `--with-devkit`
1032 to point to a single directory, if it is correctly setup. (See `basics.m4` for
1033 details.)
1034
1035 If you are unsure what toolchain and versions to use, these have been proved
1036 working at the time of writing:
1037
1038 * [aarch64](
1039 https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-linux-gnu-4.8-2013.11_linux.tar.xz)
1040 * [arm 32-bit hardware floating point](
1041 https://launchpad.net/linaro-toolchain-unsupported/trunk/2012.09/+download/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux.tar.bz2)
1042
1043 ### Native Libraries
1044
1045 You will need copies of external native libraries for the *target* system,
1046 present on the *build* machine while building.
1047
1048 Take care not to replace the *build* system's version of these libraries by
1049 mistake, since that can render the *build* machine unusable.
1050
1051 Make sure that the libraries you point to (ALSA, X11, etc) are for the
1052 *target*, not the *build*, platform.
1053
1054 #### ALSA
1055
1056 You will need alsa libraries suitable for your *target* system. For most cases,
1057 using Debian's pre-built libraries work fine.
1058
1059 Note that alsa is needed even if you only want to build a headless JDK.
1060
1061 * Go to [Debian Package Search](https://www.debian.org/distrib/packages) and
1062 search for the `libasound2` and `libasound2-dev` packages for your *target*
1063 system. Download them to /tmp.
1064
1065 * Install the libraries into the cross-compilation toolchain. For instance:
1066 ```
1067 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc
1068 dpkg-deb -x /tmp/libasound2_1.0.25-4_armhf.deb .
1069 dpkg-deb -x /tmp/libasound2-dev_1.0.25-4_armhf.deb .
1070 ```
1071
1072 * If alsa is not properly detected by `configure`, you can point it out by
1073 `--with-alsa`.
1074
1075 #### X11
1076
1077 You will need X11 libraries suitable for your *target* system. For most cases,
1078 using Debian's pre-built libraries work fine.
1079
1080 Note that X11 is needed even if you only want to build a headless JDK.
1081
1082 * Go to [Debian Package Search](https://www.debian.org/distrib/packages),
1083 search for the following packages for your *target* system, and download them
1084 to /tmp/target-x11:
1085 * libxi
1086 * libxi-dev
1087 * x11proto-core-dev
1088 * x11proto-input-dev
1089 * x11proto-kb-dev
1090 * x11proto-render-dev
1091 * x11proto-xext-dev
1092 * libice-dev
1093 * libxrender
1094 * libxrender-dev
1095 * libxrandr-dev
1096 * libsm-dev
1097 * libxt-dev
1098 * libx11
1099 * libx11-dev
1100 * libxtst
1101 * libxtst-dev
1102 * libxext
1103 * libxext-dev
1104
1105 * Install the libraries into the cross-compilation toolchain. For instance:
1106 ```
1107 cd /tools/gcc-linaro-arm-linux-gnueabihf-raspbian-2012.09-20120921_linux/arm-linux-gnueabihf/libc/usr
1108 mkdir X11R6
1109 cd X11R6
1110 for deb in /tmp/target-x11/*.deb ; do dpkg-deb -x $deb . ; done
1111 mv usr/* .
1112 cd lib
1113 cp arm-linux-gnueabihf/* .
1114 ```
1115
1116 You can ignore the following messages. These libraries are not needed to
1117 successfully complete a full JDK build.
1118 ```
1119 cp: cannot stat `arm-linux-gnueabihf/libICE.so': No such file or directory
1120 cp: cannot stat `arm-linux-gnueabihf/libSM.so': No such file or directory
1121 cp: cannot stat `arm-linux-gnueabihf/libXt.so': No such file or directory
1122 ```
1123
1124 * If the X11 libraries are not properly detected by `configure`, you can
1125 point them out by `--with-x`.
1126
1127 ### Creating And Using Sysroots With qemu-deboostrap
1128
1129 Fortunately, you can create sysroots for foreign architectures with tools
1130 provided by your OS. On Debian/Ubuntu systems, one could use `qemu-deboostrap` to
1131 create the *target* system chroot, which would have the native libraries and headers
1132 specific to that *target* system. After that, we can use the cross-compiler on the *build*
1133 system, pointing into chroot to get the build dependencies right. This allows building
1134 for foreign architectures with native compilation speed.
1135
1136 For example, cross-compiling to AArch64 from x86_64 could be done like this:
1137
1138 * Install cross-compiler on the *build* system:
1139 ```
1140 apt install g++-aarch64-linux-gnu gcc-aarch64-linux-gnu
1141 ```
1142
1143 * Create chroot on the *build* system, configuring it for *target* system:
1144 ```
1145 sudo qemu-debootstrap --arch=arm64 --verbose \
1146 --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 \
1147 --resolve-deps jessie /chroots/arm64 http://httpredir.debian.org/debian/
1148 ```
1149
1150 * Configure and build with newly created chroot as sysroot/toolchain-path:
1151 ```
1152 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/
1153 make images
1154 ls build/linux-aarch64-normal-server-release/
1155 ```
1156
1157 The build does not create new files in that chroot, so it can be reused for multiple builds
1158 without additional cleanup.
1159
1160 Architectures that are known to successfully cross-compile like this are:
1161
1162 Target `CC` `CXX` `--arch=...` `--openjdk-target=...`
1163 ------------ ------------------------- --------------------------- ------------- -----------------------
1164 x86 default default i386 i386-linux-gnu
1165 armhf gcc-arm-linux-gnueabihf g++-arm-linux-gnueabihf armhf arm-linux-gnueabihf
1166 aarch64 gcc-aarch64-linux-gnu g++-aarch64-linux-gnu arm64 aarch64-linux-gnu
1167 ppc64el gcc-powerpc64le-linux-gnu g++-powerpc64le-linux-gnu ppc64el powerpc64le-linux-gnu
1168 s390x gcc-s390x-linux-gnu g++-s390x-linux-gnu s390x s390x-linux-gnu
1169
1170 Additional architectures might be supported by Debian/Ubuntu Ports.
1171
1172 ### Building for ARM/aarch64
1173
1174 A common cross-compilation target is the ARM CPU. When building for ARM, it is
1175 useful to set the ABI profile. A number of pre-defined ABI profiles are
1176 available using `--with-abi-profile`: arm-vfp-sflt, arm-vfp-hflt, arm-sflt,
1177 armv5-vfp-sflt, armv6-vfp-hflt. Note that soft-float ABIs are no longer
1178 properly supported by the JDK.
1179
1180 ### Verifying the Build
1181
1182 The build will end up in a directory named like
1183 `build/linux-arm-normal-server-release`.
1184
1185 Inside this build output directory, the `images/jdk` will contain the newly
1186 built JDK, for your *target* system.
1187
1188 Copy these folders to your *target* system. Then you can run e.g.
1189 `images/jdk/bin/java -version`.
1190
1191 ## Build Performance
1192
1193 Building the JDK requires a lot of horsepower. Some of the build tools can be
1194 adjusted to utilize more or less of resources such as parallel threads and
1195 memory. The `configure` script analyzes your system and selects reasonable
1196 values for such options based on your hardware. If you encounter resource
1197 problems, such as out of memory conditions, you can modify the detected values
1198 with:
1199
1200 * `--with-num-cores` -- number of cores in the build system, e.g.
1201 `--with-num-cores=8`.
1202
1203 * `--with-memory-size` -- memory (in MB) available in the build system, e.g.
1204 `--with-memory-size=1024`
1205
1206 You can also specify directly the number of build jobs to use with
1207 `--with-jobs=N` to `configure`, or `JOBS=N` to `make`. Do not use the `-j` flag
1208 to `make`. In most cases it will be ignored by the makefiles, but it can cause
1209 problems for some make targets.
1210
1211 It might also be necessary to specify the JVM arguments passed to the Boot JDK,
1212 using e.g. `--with-boot-jdk-jvmargs="-Xmx8G"`. Doing so will override the
1213 default JVM arguments passed to the Boot JDK.
1214
1215 At the end of a successful execution of `configure`, you will get a performance
1216 summary, indicating how well the build will perform. Here you will also get
1217 performance hints. If you want to build fast, pay attention to those!
1218
1219 If you want to tweak build performance, run with `make LOG=info` to get a build
1220 time summary at the end of the build process.
1221
1222 ### Disk Speed
1223
1224 If you are using network shares, e.g. via NFS, for your source code, make sure
1225 the build directory is situated on local disk (e.g. by `ln -s
1226 /localdisk/jdk-build $JDK-SHARE/build`). The performance penalty is extremely
1227 high for building on a network share; close to unusable.
1228
1229 Also, make sure that your build tools (including Boot JDK and toolchain) is
1230 located on a local disk and not a network share.
1231
1232 As has been stressed elsewhere, do use SSD for source code and build directory,
1233 as well as (if possible) the build tools.
1234
1235 ### Virus Checking
1236
1237 The use of virus checking software, especially on Windows, can *significantly*
1238 slow down building of the JDK. If possible, turn off such software, or exclude
1239 the directory containing the JDK source code from on-the-fly checking.
1240
1241 ### Ccache
1242
1243 The JDK build supports building with ccache when using gcc or clang. Using
1244 ccache can radically speed up compilation of native code if you often rebuild
1245 the same sources. Your milage may vary however, so we recommend evaluating it
1246 for yourself. To enable it, make sure it's on the path and configure with
1247 `--enable-ccache`.
1248
1249 ### Precompiled Headers
1250
1251 By default, the Hotspot build uses preccompiled headers (PCH) on the toolchains
1252 were it is properly supported (clang, gcc, and Visual Studio). Normally, this
1253 speeds up the build process, but in some circumstances, it can actually slow
1254 things down.
1255
1256 You can experiment by disabling precompiled headers using
1257 `--disable-precompiled-headers`.
1258
1259 ### Icecc / icecream
1260
1261 [icecc/icecream](http://github.com/icecc/icecream) is a simple way to setup a
1262 distributed compiler network. If you have multiple machines available for
1263 building the JDK, you can drastically cut individual build times by utilizing
1264 it.
1265
1266 To use, setup an icecc network, and install icecc on the build machine. Then
1267 run `configure` using `--enable-icecc`.
1268
1269 ### Using sjavac
1270
1271 To speed up Java compilation, especially incremental compilations, you can try
1272 the experimental sjavac compiler by using `--enable-sjavac`.
1273
1274 ### Building the Right Target
1275
1276 Selecting the proper target to build can have dramatic impact on build time.
1277 For normal usage, `jdk` or the default target is just fine. You only need to
1278 build `images` for shipping, or if your tests require it.
1279
1280 See also [Using Fine-Grained Make Targets](#using-fine-grained-make-targets) on
1281 how to build an even smaller subset of the product.
1282
1283 ## Troubleshooting
1284
1285 If your build fails, it can sometimes be difficult to pinpoint the problem or
1286 find a proper solution.
1287
1288 ### Locating the Source of the Error
1289
1290 When a build fails, it can be hard to pinpoint the actual cause of the error.
1291 In a typical build process, different parts of the product build in parallel,
1292 with the output interlaced.
1293
1294 #### Build Failure Summary
1295
1296 To help you, the build system will print a failure summary at the end. It looks
1297 like this:
1298
1299 ```
1300 ERROR: Build failed for target 'hotspot' in configuration 'linux-x64' (exit code 2)
1301
1302 === Output from failing command(s) repeated here ===
1303 * For target hotspot_variant-server_libjvm_objs_psMemoryPool.o:
1304 /localhome/hg/jdk9-sandbox/hotspot/src/share/vm/services/psMemoryPool.cpp:1:1: error: 'failhere' does not name a type
1305 ... (rest of output omitted)
1306
1307 * All command lines available in /localhome/hg/jdk9-sandbox/build/linux-x64/make-support/failure-logs.
1308 === End of repeated output ===
1309
1310 === Make failed targets repeated here ===
1311 lib/CompileJvm.gmk:207: recipe for target '/localhome/hg/jdk9-sandbox/build/linux-x64/hotspot/variant-server/libjvm/objs/psMemoryPool.o' failed
1312 make/Main.gmk:263: recipe for target 'hotspot-server-libs' failed
1313 === End of repeated output ===
1314
1315 Hint: Try searching the build log for the name of the first failed target.
1316 Hint: If caused by a warning, try configure --disable-warnings-as-errors.
1317 ```
1318
1319 Let's break it down! First, the selected configuration, and the top-level
1320 target you entered on the command line that caused the failure is printed.
1321
1322 Then, between the `Output from failing command(s) repeated here` and `End of
1323 repeated output` the first lines of output (stdout and stderr) from the actual
1324 failing command is repeated. In most cases, this is the error message that
1325 caused the build to fail. If multiple commands were failing (this can happen in
1326 a parallel build), output from all failed commands will be printed here.
1327
1328 The path to the `failure-logs` directory is printed. In this file you will find
1329 a `<target>.log` file that contains the output from this command in its
1330 entirety, and also a `<target>.cmd`, which contain the complete command line
1331 used for running this command. You can re-run the failing command by executing
1332 `. <path to failure-logs>/<target>.cmd` in your shell.
1333
1334 Another way to trace the failure is to follow the chain of make targets, from
1335 top-level targets to individual file targets. Between `Make failed targets
1336 repeated here` and `End of repeated output` the output from make showing this
1337 chain is repeated. The first failed recipe will typically contain the full path
1338 to the file in question that failed to compile. Following lines will show a
1339 trace of make targets why we ended up trying to compile that file.
1340
1341 Finally, some hints are given on how to locate the error in the complete log.
1342 In this example, we would try searching the log file for "`psMemoryPool.o`".
1343 Another way to quickly locate make errors in the log is to search for "`]
1344 Error`" or "`***`".
1345
1346 Note that the build failure summary will only help you if the issue was a
1347 compilation failure or similar. If the problem is more esoteric, or is due to
1348 errors in the build machinery, you will likely get empty output logs, and `No
1349 indication of failed target found` instead of the make target chain.
1350
1351 #### Checking the Build Log File
1352
1353 The output (stdout and stderr) from the latest build is always stored in
1354 `$BUILD/build.log`. The previous build log is stored as `build.log.old`. This
1355 means that it is not necessary to redirect the build output yourself if you
1356 want to process it.
1357
1358 You can increase the verbosity of the log file, by the `LOG` control variable
1359 to `make`. If you want to see the command lines used in compilations, use
1360 `LOG=cmdlines`. To increase the general verbosity, use `LOG=info`, `LOG=debug`
1361 or `LOG=trace`. Both of these can be combined with `cmdlines`, e.g.
1362 `LOG=info,cmdlines`. The `debug` log level will show most shell commands
1363 executed by make, and `trace` will show all. Beware that both these log levels
1364 will produce a massive build log!
1365
1366 ### Fixing Unexpected Build Failures
1367
1368 Most of the time, the build will fail due to incorrect changes in the source
1369 code.
1370
1371 Sometimes the build can fail with no apparent changes that have caused the
1372 failure. If this is the first time you are building the JDK on this particular
1373 computer, and the build fails, the problem is likely with your build
1374 environment. But even if you have previously built the JDK with success, and it
1375 now fails, your build environment might have changed (perhaps due to OS
1376 upgrades or similar). But most likely, such failures are due to problems with
1377 the incremental rebuild.
1378
1379 #### Problems with the Build Environment
1380
1381 Make sure your configuration is correct. Re-run `configure`, and look for any
1382 warnings. Warnings that appear in the middle of the `configure` output is also
1383 repeated at the end, after the summary. The entire log is stored in
1384 `$BUILD/configure.log`.
1385
1386 Verify that the summary at the end looks correct. Are you indeed using the Boot
1387 JDK and native toolchain that you expect?
1388
1389 By default, the JDK has a strict approach where warnings from the compiler is
1390 considered errors which fail the build. For very new or very old compiler
1391 versions, this can trigger new classes of warnings, which thus fails the build.
1392 Run `configure` with `--disable-warnings-as-errors` to turn of this behavior.
1393 (The warnings will still show, but not make the build fail.)
1394
1395 #### Problems with Incremental Rebuilds
1396
1397 Incremental rebuilds mean that when you modify part of the product, only the
1398 affected parts get rebuilt. While this works great in most cases, and
1399 significantly speed up the development process, from time to time complex
1400 interdependencies will result in an incorrect build result. This is the most
1401 common cause for unexpected build problems.
1402
1403 Here are a suggested list of things to try if you are having unexpected build
1404 problems. Each step requires more time than the one before, so try them in
1405 order. Most issues will be solved at step 1 or 2.
1406
1407 1. Make sure your repository is up-to-date
1408
1409 Run `hg pull -u` to make sure you have the latest changes.
1410
1411 2. Clean build results
1412
1413 The simplest way to fix incremental rebuild issues is to run `make clean`.
1414 This will remove all build results, but not the configuration or any build
1415 system support artifacts. In most cases, this will solve build errors
1416 resulting from incremental build mismatches.
1417
1418 3. Completely clean the build directory.
1419
1420 If this does not work, the next step is to run `make dist-clean`, or
1421 removing the build output directory (`$BUILD`). This will clean all
1422 generated output, including your configuration. You will need to re-run
1423 `configure` after this step. A good idea is to run `make
1424 print-configuration` before running `make dist-clean`, as this will print
1425 your current `configure` command line. Here's a way to do this:
1426
1427 ```
1428 make print-configuration > current-configuration
1429 make dist-clean
1430 bash configure $(cat current-configuration)
1431 make
1432 ```
1433
1434 4. Re-clone the Mercurial repository
1435
1436 Sometimes the Mercurial repository gets in a state that causes the product
1437 to be un-buildable. In such a case, the simplest solution is often the
1438 "sledgehammer approach": delete the entire repository, and re-clone it.
1439 If you have local changes, save them first to a different location using
1440 `hg export`.
1441
1442 ### Specific Build Issues
1443
1444 #### Clock Skew
1445
1446 If you get an error message like this:
1447 ```
1448 File 'xxx' has modification time in the future.
1449 Clock skew detected. Your build may be incomplete.
1450 ```
1451 then the clock on your build machine is out of sync with the timestamps on the
1452 source files. Other errors, apparently unrelated but in fact caused by the
1453 clock skew, can occur along with the clock skew warnings. These secondary
1454 errors may tend to obscure the fact that the true root cause of the problem is
1455 an out-of-sync clock.
1456
1457 If you see these warnings, reset the clock on the build machine, run `make
1458 clean` and restart the build.
1459
1460 #### Out of Memory Errors
1461
1462 On Solaris, you might get an error message like this:
1463 ```
1464 Trouble writing out table to disk
1465 ```
1466 To solve this, increase the amount of swap space on your build machine.
1467
1468 On Windows, you might get error messages like this:
1469 ```
1470 fatal error - couldn't allocate heap
1471 cannot create ... Permission denied
1472 spawn failed
1473 ```
1474 This can be a sign of a Cygwin problem. See the information about solving
1475 problems in the [Cygwin](#cygwin) section. Rebooting the computer might help
1476 temporarily.
1477
1478 ### Getting Help
1479
1480 If none of the suggestions in this document helps you, or if you find what you
1481 believe is a bug in the build system, please contact the Build Group by sending
1482 a mail to [build-dev@openjdk.java.net](mailto:build-dev@openjdk.java.net).
1483 Please include the relevant parts of the configure and/or build log.
1484
1485 If you need general help or advice about developing for the JDK, you can also
1486 contact the Adoption Group. See the section on [Contributing to OpenJDK](
1487 #contributing-to-openjdk) for more information.
1488
1489 ## Hints and Suggestions for Advanced Users
1490
1491 ### Setting Up a Repository for Pushing Changes (defpath)
1492
1493 To help you prepare a proper push path for a Mercurial repository, there exists
1494 a useful tool known as [defpath](
1495 http://openjdk.java.net/projects/code-tools/defpath). It will help you setup a
1496 proper push path for pushing changes to the JDK.
1497
1498 Install the extension by cloning
1499 `http://hg.openjdk.java.net/code-tools/defpath` and updating your `.hgrc` file.
1500 Here's one way to do this:
1501
1502 ```
1503 cd ~
1504 mkdir hg-ext
1505 cd hg-ext
1506 hg clone http://hg.openjdk.java.net/code-tools/defpath
1507 cat << EOT >> ~/.hgrc
1508 [extensions]
1509 defpath=~/hg-ext/defpath/defpath.py
1510 EOT
1511 ```
1512
1513 You can now setup a proper push path using:
1514 ```
1515 hg defpath -d -u <your OpenJDK username>
1516 ```
1517
1518 ### Bash Completion
1519
1520 The `configure` and `make` commands tries to play nice with bash command-line
1521 completion (using `<tab>` or `<tab><tab>`). To use this functionality, make
1522 sure you enable completion in your `~/.bashrc` (see instructions for bash in
1523 your operating system).
1524
1525 Make completion will work out of the box, and will complete valid make targets.
1526 For instance, typing `make jdk-i<tab>` will complete to `make jdk-image`.
1527
1528 The `configure` script can get completion for options, but for this to work you
1529 need to help `bash` on the way. The standard way of running the script, `bash
1530 configure`, will not be understood by bash completion. You need `configure` to
1531 be the command to run. One way to achieve this is to add a simple helper script
1532 to your path:
1533
1534 ```
1535 cat << EOT > /tmp/configure
1536 #!/bin/bash
1537 if [ \$(pwd) = \$(cd \$(dirname \$0); pwd) ] ; then
1538 echo >&2 "Abort: Trying to call configure helper recursively"
1539 exit 1
1540 fi
1541
1542 bash \$PWD/configure "\$@"
1543 EOT
1544 chmod +x /tmp/configure
1545 sudo mv /tmp/configure /usr/local/bin
1546 ```
1547
1548 Now `configure --en<tab>-dt<tab>` will result in `configure --enable-dtrace`.
1549
1550 ### Using Multiple Configurations
1551
1552 You can have multiple configurations for a single source repository. When you
1553 create a new configuration, run `configure --with-conf-name=<name>` to create a
1554 configuration with the name `<name>`. Alternatively, you can create a directory
1555 under `build` and run `configure` from there, e.g. `mkdir build/<name> && cd
1556 build/<name> && bash ../../configure`.
1557
1558 Then you can build that configuration using `make CONF_NAME=<name>` or `make
1559 CONF=<pattern>`, where `<pattern>` is a substring matching one or several
1560 configurations, e.g. `CONF=debug`. The special empty pattern (`CONF=`) will
1561 match *all* available configuration, so `make CONF= hotspot` will build the
1562 `hotspot` target for all configurations. Alternatively, you can execute `make`
1563 in the configuration directory, e.g. `cd build/<name> && make`.
1564
1565 ### Handling Reconfigurations
1566
1567 If you update the repository and part of the configure script has changed, the
1568 build system will force you to re-run `configure`.
1569
1570 Most of the time, you will be fine by running `configure` again with the same
1571 arguments as the last time, which can easily be performed by `make
1572 reconfigure`. To simplify this, you can use the `CONF_CHECK` make control
1573 variable, either as `make CONF_CHECK=auto`, or by setting an environment
1574 variable. For instance, if you add `export CONF_CHECK=auto` to your `.bashrc`
1575 file, `make` will always run `reconfigure` automatically whenever the configure
1576 script has changed.
1577
1578 You can also use `CONF_CHECK=ignore` to skip the check for a needed configure
1579 update. This might speed up the build, but comes at the risk of an incorrect
1580 build result. This is only recommended if you know what you're doing.
1581
1582 From time to time, you will also need to modify the command line to `configure`
1583 due to changes. Use `make print-configure` to show the command line used for
1584 your current configuration.
1585
1586 ### Using Fine-Grained Make Targets
1587
1588 The default behavior for make is to create consistent and correct output, at
1589 the expense of build speed, if necessary.
1590
1591 If you are prepared to take some risk of an incorrect build, and know enough of
1592 the system to understand how things build and interact, you can speed up the
1593 build process considerably by instructing make to only build a portion of the
1594 product.
1595
1596 #### Building Individual Modules
1597
1598 The safe way to use fine-grained make targets is to use the module specific
1599 make targets. All source code in the JDK is organized so it belongs to a
1600 module, e.g. `java.base` or `jdk.jdwp.agent`. You can build only a specific
1601 module, by giving it as make target: `make jdk.jdwp.agent`. If the specified
1602 module depends on other modules (e.g. `java.base`), those modules will be built
1603 first.
1604
1605 You can also specify a set of modules, just as you can always specify a set of
1606 make targets: `make jdk.crypto.cryptoki jdk.crypto.ec jdk.crypto.mscapi
1607 jdk.crypto.ucrypto`
1608
1609 #### Building Individual Module Phases
1610
1611 The build process for each module is divided into separate phases. Not all
1612 modules need all phases. Which are needed depends on what kind of source code
1613 and other artifact the module consists of. The phases are:
1614
1615 * `gensrc` (Generate source code to compile)
1616 * `gendata` (Generate non-source code artifacts)
1617 * `copy` (Copy resource artifacts)
1618 * `java` (Compile Java code)
1619 * `launchers` (Compile native executables)
1620 * `libs` (Compile native libraries)
1621 * `rmic` (Run the `rmic` tool)
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 ---