1b(1) General Commands Manual b(1)
2
6 b - build system driver
7
9 b --help
10 b --version
11 b [options] [variables] [buildspec]
12 buildspec = meta-operation(operation(target...[,parameters])...)...
14
16 The build2 build system driver executes a set of meta-operations on op‐
17 erations on targets according to the build specification, or buildspec
18 for short. This process can be controlled by specifying driver options
19 and build system variables.
20 Note that options, variables, and buildspec fragments can be specified
22 in any order. To avoid treating an argument that starts with '-' as an
23 option, add the '--' separator. To avoid treating an argument that con‐
24 tains '=' as a variable, add the second '--' separator.
25 All components in the buildspec can be omitted. If meta-operation is
27 omitted, then it defaults to perform. If operation is omitted, then it
28 defaults to the default operation for this meta-operation. For perform
29 it is update. Finally, if target is omitted, then it defaults to the
30 current working directory. A meta-operation on operation is called an
31 action. Some operations and meta-operations may take additional parame‐
32 ters. For example:
33 $ b # perform(update(./))
35 $ b foo/ # perform(update(foo/))
36 $ b foo/ bar/ # perform(update(foo/ bar/))
37 $ b update # perform(update(./))
38 $ b 'clean(../)' # perform(clean(../))
39 $ b perform # perform(update(./))
40 $ b configure # configure(?(./))
41 $ b 'configure(../)' # configure(?(../))
42 $ b clean update # perform(clean(./) update(./))
43 $ b configure update # configure(?(./)) perform(update(./))
44 $ b 'create(conf/, cxx)' # create(?(conf/), cxx)
45 Notice the question mark used to show the (imaginary) default operation
47 for the configure meta-operation. For configure the default operation
48 is "all operations". That is, it will configure all the operations for
49 the specified target.
50 You can also "generate" multiple operations for the same set of tar‐
52 gets. Compare:
53 $ b 'clean(foo/ bar/)' 'update(foo/ bar/)'
55 $ b '{clean update}(foo/ bar/)'
56 Some more useful buildspec examples:
58 $ b '{clean update}(...)' # rebuild
60 $ b '{clean update clean}(...)' # make sure builds
61 $ b '{clean test clean}(...)' # make sure passes tests
62 $ b '{clean disfigure}(...)' # similar to distclean
63 In POSIX shells parenthesis are special characters and must be quoted
65 when used in a buildspec. Besides being an inconvenience in itself,
66 quoting also inhibits path auto-completion. To help with this situation
67 a shortcut syntax is available for executing a single operation or
68 meta-operation, for example:
69 $ b clean: foo/ bar/ # clean(foo/ bar/)
71 $ b configure: src/@out/ # configure(src/@out/)
72 $ b create: conf/, cxx # create(conf/, cxx)
73 $ b configure: config.cxx=g++ src/ # configure(src/) config.cxx=g++
74 To activate the shortcut syntax the first buildspec argument must start
76 with an operation or meta-operation name and end with a colon (:). To
77 transform the shortcut syntax to the normal buildspec syntax the colon
78 is replaced with the opening parenthesis ('('), the rest of the build‐
79 spec arguments are treated as is, and the final closing parenthesis
80 (')') is added.
81 For each target the driver expects to find buildfile either in the tar‐
83 get's directory or, if the directory is part of the out tree
84 (out_base), in the corresponding src directory (src_base).
85 For example, assuming foo/ is the source directory of a project:
87 $ b foo/ # out_base=src_base=foo/
89 $ b foo-out/ # out_base=foo-out/ src_base=foo/
90 $ b foo-out/exe{foo} # out_base=foo-out/ src_base=foo/
91 An exception to this requirement is a directory target in which case,
93 provided the directory has subdirectories, an implied buildfile with
94 the following content is assumed:
95 # Implied directory buildfile: build all subdirectories.
97 #
98 ./: */
99 In the above example, we assumed that the build system driver was able
101 to determine the association between out_base and src_base. In case
102 src_base and out_base are not the same directory, this is achieved in
103 one of two ways: the config module (which implements the configure,
104 disfigure, and create meta-operations) saves this association as part
105 of the configuration process. If, however, the association hasn't been
106 saved, then we have to specify src_base explicitly using the following
107 extended target syntax:
108 src-base/@target
110 Continuing with the previous example:
112 $ b foo/@foo-out/exe{foo} # out_base=foo-out/ src_base=foo/
114 Normally, you would need to specify src_base explicitly only once, dur‐
116 ing configuration. For example, a typical usage would be:
117 $ b configure: foo/@foo-out/ # src_base is saved
119 $ b foo-out/ # no need to specify src_base
120 $ b clean: foo-out/exe{foo} # no need to specify src_base
121 Besides in and out of source builds, build2 also supports configuring a
123 project's source directory as forwarded to an out of source build. With
124 such a forwarded configuration in place, if we run the build system
125 driver from the source directory, it will automatically build in the
126 output directory and backlink (using symlinks or another suitable mech‐
127 anism) certain "interesting" targets (executables, documentation, etc)
128 to the source directory for easy access. Continuing with the previous
129 example:
130 $ b configure: foo/@foo-out/,forward # foo/ forwarded to foo-out/
132 $ cd foo/
133 $ b # build in foo-out/
134 $ ./foo # symlink to foo-out/foo
135 The ability to specify build2 variables as part of the command line is
137 normally used to pass configuration values, for example:
138 $ b config.cxx=clang++ config.cxx.coptions=-O3
140 Similar to buildspec, POSIX shells often inhibit path auto-completion
142 on the right hand side of a variable assignment. To help with this sit‐
143 uation the assignment can be broken down into three separate command
144 line arguments, for example:
145 $ b config.import.libhello = ../libhello/
147 The build system has the following built-in and pre-defined meta-opera‐
149 tions:
150 perform
152 Perform an operation.
153 configure
155 Configure all operations supported by a project and save the re‐
156 sult in the project's build/config.build file. Implemented by
157 the config module. For example:
158 $ b configure \
160 config.cxx=clang++ \
161 config.cxx.coptions=-O3 \
162 config.install.root=/usr/local \
163 config.install.root.sudo=sudo
164 Use the forward parameter to instead configure a source direc‐
166 tory as forwarded to an out of source build. For example:
167 $ b configure: src/@out/,forward
169 disfigure
171 Disfigure all operations supported by a project and remove the
172 project's build/config.build file. Implemented by the config
173 module.
174 Use the forward parameter to instead disfigure forwarding of a
176 source directory to an out of source build. For example:
177 $ b disfigure: src/,forward
179 create
181 Create and configure a configuration project. Implemented by the
182 config module.
183 Normally a build2 project is created manually by writing the
185 bootstrap.build and config.build files, adding source files, and
186 so on. However, a special kind of project, which we call config‐
187 uration, is often useful. Such a project doesn't have any source
188 files of its own. Instead, it serves as an amalgamation for
189 building other projects as part of it. Doing it this way has two
190 major benefits: sub-projects automatically resolve their imports
191 to other projects in the amalgamation and sub-projects inherits
192 their configuration from the amalgamation (which means if we
193 want to change something, we only need to do it in one place).
194 As an example, let's assume we have two C++ projects: the lib‐
196 hello library in libhello/ and the hello executable that imports
197 it in hello/. And we want to build hello with clang++.
198 One way to do it would be to configure and build each project in
200 its own directory, for example:
201 $ b configure: libhello/@libhello-clang/ config.cxx=clang++
203 $ b configure: hello/@hello-clang/ config.cxx=clang++ \
204 config.import.libhello=libhello-clang/
205 The two drawbacks, as mentioned above, are the need to explic‐
207 itly resolve the import and having to make changes in multiple
208 places should, for example, we want to switch from clang++ to
209 g++.
210 We can, however, achieve the same end result but without any of
212 the drawbacks using the configuration project:
213 $ b create: clang/,cxx config.cxx=clang++ # Creates clang/.
215 $ b configure: libhello/@clang/libhello/
216 $ b configure: hello/@clang/hello/
217 The targets passed to the create meta-operation must be directo‐
219 ries which should either not exist or be empty. For each such
220 directory create first initializes a project as described below
221 and then configures it by executing the configure meta-opera‐
222 tion.
223 The first optional parameter to create is the list of modules to
225 load in root.build. By default, create appends .config to the
226 names of these modules so that only their configurations are
227 loaded. You can override this behavior by specifying the period
228 (.) after the module name. You can also instruct create to use
229 the optional module load by prefixing the module name with the
230 question mark (?).
231 The second optional parameter is the list of modules to load in
233 bootstrap.build. If not specified, then the test, dist, and in‐
234 stall modules are loaded by default. The config module is always
235 loaded first.
236 Besides creating project's bootstrap.build and root.build, cre‐
238 ate also writes the root buildfile with the following contents:
239 ./: {*/ -build/}
241 If used, this buildfile will build all the sub-projects cur‐
243 rently present in the configuration.
244 dist
246 Prepare a distribution containing all files necessary to perform
247 all operations in a project. Implemented by the dist module.
248 info
250 Print basic information (name, version, source and output direc‐
251 tories, etc) about one or more projects to STDOUT, separating
252 multiple projects with a blank line. Each project is identified
253 by its root directory target. For example:
254 $ b info: libfoo/ libbar/
256 The build system has the following built-in and pre-defined operations:
258 update
260 Update a target.
261 clean
263 Clean a target.
264 test
266 Test a target. Performs update as a pre-operation. Implemented
267 by the test module.
268 update-for-test
270 Update a target for testing. This operation is equivalent to the
271 update pre-operation as executed by the test operation and can
272 be used to only update what is necessary for testing. Imple‐
273 mented by the test module.
274 install
276 Install a target. Performs update as a pre-operation. Imple‐
277 mented by the install module.
278 uninstall
280 Uninstall a target. Performs update as a pre-operation. Imple‐
281 mented by the install module.
282 update-for-install
284 Update a target for installation. This operation is equivalent
285 to the update pre-operation as executed by the install operation
286 and can be used to only update what is necessary for installa‐
287 tion. Implemented by the install module.
288 Note that buildspec and command line variable values are treated as
290 buildfile fragments and so can use quoting and escaping as well as con‐
291 tain variable expansions and evaluation contexts. However, to be more
292 usable on various platforms, escaping in these two situations is lim‐
293 ited to the effective sequences of \', \", \\, \$, and \( with all
294 other sequences interpreted as is. Together with double-quoting this is
295 sufficient to represent any value. For example:
296 $ b config.install.root=c:\projects\install
298 $ b "config.install.root='c:\Program Files (x86)\test\'"
299 $ b 'config.cxx.poptions=-DFOO_STR="foo"'
300
302 -v Print actual commands being executed. This options is equivalent
303 to --verbose 2.
304 -V Print all underlying commands being executed. This options is
306 equivalent to --verbose 3.
307 --quiet|-q
309 Run quietly, only printing error messages in most contexts. In
310 certain contexts (for example, while updating build system mod‐
311 ules) this verbosity level may be ignored. Use --silent to run
312 quietly in all contexts. This option is equivalent to --verbose
313 0.
314 --silent
316 Run quietly, only printing error messages in all contexts.
317 --verbose level
319 Set the diagnostics verbosity to level between 0 and 6. Level 0
320 disables any non-error messages (but see the difference between
321 --quiet and --silent) while level 6 produces lots of informa‐
322 tion, with level 1 being the default. The following additional
323 types of diagnostics are produced at each level:
324 1. High-level information messages.
326 2. Essential underlying commands being executed.
328 3. All underlying commands being executed.
330 4. Information that could be helpful to the user.
332 5. Information that could be helpful to the developer.
334 6. Even more detailed information.
336 --stat Display build statistics.
338 --dump phase
340 Dump the build system state after the specified phase. Valid
341 phase values are load (after loading buildfiles) and match (af‐
342 ter matching rules to targets). Repeat this option to dump the
343 state after multiple phases.
344 --progress
346 Display build progress. If printing to a terminal the progress
347 is displayed by default for low verbosity levels. Use --no-
348 progress to suppress.
349 --no-progress
351 Don't display build progress.
352 --jobs|-j num
354 Number of active jobs to perform in parallel. This includes both
355 the number of active threads inside the build system as well as
356 the number of external commands (compilers, linkers, etc)
357 started but not yet finished. If this option is not specified or
358 specified with the 0 value, then the number of available hard‐
359 ware threads is used.
360 --max-jobs|-J num
362 Maximum number of jobs (threads) to create. The default is 8x
363 the number of active jobs (--jobs|j) on 32-bit architectures and
364 32x on 64-bit. See the build system scheduler implementation for
365 details.
366 --queue-depth|-Q num
368 The queue depth as a multiplier over the number of active jobs.
369 Normally we want a deeper queue if the jobs take long (for exam‐
370 ple, compilation) and shorter if they are quick (for example,
371 simple tests). The default is 4. See the build system scheduler
372 implementation for details.
373 --file-cache impl
375 File cache implementation to use for intermediate build results.
376 Valid values are noop (no caching or compression) and sync-lz4
377 (no caching with synchronous LZ4 on-disk compression). If this
378 option is not specified, then a suitable default implementation
379 is used (currently sync-lz4).
380 --max-stack num
382 The maximum stack size in KBytes to allow for newly created
383 threads. For pthreads-based systems the driver queries the stack
384 size of the main thread and uses the same size for creating ad‐
385 ditional threads. This allows adjusting the stack size using fa‐
386 miliar mechanisms, such as ulimit. Sometimes, however, the
387 stack size of the main thread is excessively large. As a re‐
388 sult, the driver checks if it is greater than a predefined limit
389 (64MB on 64-bit systems and 32MB on 32-bit ones) and caps it to
390 a more sensible value (8MB) if that's the case. This option al‐
391 lows you to override this check with the special zero value in‐
392 dicating that the main thread stack size should be used as is.
393 --serial-stop|-s
395 Run serially and stop at the first error. This mode is useful to
396 investigate build failures that are caused by build system er‐
397 rors rather than compilation errors. Note that if you don't want
398 to keep going but still want parallel execution, add --jobs|-j
399 (for example -j 0 for default concurrency).
400 --dry-run|-n
402 Print commands without actually executing them. Note that com‐
403 mands that are required to create an accurate build state will
404 still be executed and the extracted auxiliary dependency infor‐
405 mation saved. In other words, this is not the "don't touch the
406 filesystem" mode but rather "do minimum amount of work to show
407 what needs to be done". Note also that only the perform meta-op‐
408 eration supports this mode.
409 --match-only
411 Match the rules but do not execute the operation. This mode is
412 primarily useful for profiling.
413 --no-external-modules
415 Don't load external modules during project bootstrap. Note that
416 this option can only be used with meta-operations that do not
417 load the project's buildfiles, such as info.
418 --structured-result
420 Write the result of execution in a structured form. In this
421 mode, instead of printing to STDERR diagnostics messages about
422 the outcome of executing actions on targets, the driver writes
423 to STDOUT a structured result description one line per the
424 buildspec action/target pair. Each line has the following for‐
425 mat:
426 state meta-operation operation target
428 Where state can be one of unchanged, changed, or failed. If the
430 action is a pre or post operation, then the outer operation is
431 specified in parenthesis. For example:
432 unchanged perform update(test) /tmp/dir{hello/}
434 changed perform test /tmp/dir{hello/}
435 Note that only the perform meta-operation supports the struc‐
437 tured result output.
438 --mtime-check
440 Perform file modification time sanity checks. These checks can
441 be helpful in diagnosing spurious rebuilds and are enabled by
442 default on Windows (which is known not to guarantee monotoni‐
443 cally increasing mtimes) and for the staged version of the build
444 system on other platforms. Use --no-mtime-check to disable.
445 --no-mtime-check
447 Don't perform file modification time sanity checks. See --mtime-
448 check for details.
449 --no-column
451 Don't print column numbers in diagnostics.
452 --no-line
454 Don't print line and column numbers in diagnostics.
455 --buildfile path
457 The alternative file to read build information from. The default
458 is buildfile or build2file, depending on the project's build
459 file/directory naming scheme. If path is '-', then read from
460 STDIN. Note that this option only affects the files read as part
461 of the buildspec processing. Specifically, it has no effect on
462 the source and include directives. As a result, this option is
463 primarily intended for testing rather than changing the build
464 file names in real projects.
465 --config-guess path
467 The path to the config.guess(1) script that should be used to
468 guess the host machine triplet. If this option is not specified,
469 then b will fall back on to using the target it was built for as
470 host.
471 --config-sub path
473 The path to the config.sub(1) script that should be used to
474 canonicalize machine triplets. If this option is not specified,
475 then b will use its built-in canonicalization support which
476 should be sufficient for commonly-used platforms.
477 --pager path
479 The pager program to be used to show long text. Commonly used
480 pager programs are less and more. You can also specify addi‐
481 tional options that should be passed to the pager program with
482 --pager-option. If an empty string is specified as the pager
483 program, then no pager will be used. If the pager program is not
484 explicitly specified, then b will try to use less. If it is not
485 available, then no pager will be used.
486 --pager-option opt
488 Additional option to be passed to the pager program. See --pager
489 for more information on the pager program. Repeat this option to
490 specify multiple pager options.
491 --options-file file
493 Read additional options from file. Each option should appear on
494 a separate line optionally followed by space or equal sign (=)
495 and an option value. Empty lines and lines starting with # are
496 ignored. Option values can be enclosed in double (") or single
497 (') quotes to preserve leading and trailing whitespaces as well
498 as to specify empty values. If the value itself contains trail‐
499 ing or leading quotes, enclose it with an extra pair of quotes,
500 for example '"x"'. Non-leading and non-trailing quotes are in‐
501 terpreted as being part of the option value.
502 The semantics of providing options in a file is equivalent to
504 providing the same set of options in the same order on the com‐
505 mand line at the point where the --options-file option is speci‐
506 fied except that the shell escaping and quoting is not required.
507 Repeat this option to specify more than one options file.
508 --default-options dir
510 The directory to load additional default options files from.
511 --no-default-options
513 Don't load default options files.
514 --help Print usage information and exit.
516 --version
518 Print version and exit.
519
521 Instead of having a separate config file format for tool configuration,
522 the build2 toolchain uses default options files which contain the same
523 options as what can be specified on the command line. The default op‐
524 tions files are like options files that one can specify with --options-
525 file except that they are loaded by default.
526 The default options files for the build system driver are called b.op‐
528 tions and are searched for in the .build2/ subdirectory of the home di‐
529 rectory and in the system directory (for example, /etc/build2/) if con‐
530 figured. Note that besides options these files can also contain global
531 variable overrides.
532 Once the search is complete, the files are loaded in the reverse order,
534 that is, beginning from the system directory (if any), followed by the
535 home directory, and finishing off with the options specified on the
536 command line. In other words, the files are loaded from the more
537 generic to the more specific with the command line options having the
538 ability to override any values specified in the default options files.
539 If a default options file contains --no-default-options, then the
541 search is stopped at the directory containing this file and no outer
542 files are loaded. If this option is specified on the command line, then
543 none of the default options files are searched for or loaded.
544 An additional directory containing default options files can be speci‐
546 fied with --default-options. Its configuration files are loaded after
547 the home directory.
548 The order in which default options files are loaded is traced at the
550 verbosity level 3 (-V option) or higher.
551
553 Non-zero exit status is returned in case of an error.
554
556 The HOME environment variable is used to determine the user's home di‐
557 rectory. If it is not set, then getpwuid(3) is used instead. This value
558 is used to shorten paths printed in diagnostics by replacing the home
559 directory with ~/. It is also made available to buildfile's as the
560 build.home variable.
561 The BUILD2_VAR_OVR environment variable is used to propagate global
563 variable overrides to nested build system driver invocations. Its value
564 is a list of global variable assignments separated with newlines.
565 The BUILD2_DEF_OPT environment variable is used to suppress loading of
567 default options files in nested build system driver invocations. Its
568 values are false or 0 to suppress and true or 1 to load.
569
571 Send bug reports to the users@build2.org mailing list.
572
574 Copyright (c) 2014-2021 the build2 authors.
575 Permission is granted to copy, distribute and/or modify this document
577 under the terms of the MIT License.
578build2 0.14.0 October 2021 b(1)