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 (some output is omit‐
254 ted):
255 $ b info: libfoo/ libbar/
257 project: libfoo
258 version: 1.0.0
259 src_root: /tmp/libfoo
260 out_root: /tmp/libfoo
261 project: libbar
263 version: 2.0.0
264 src_root: /tmp/libbar
265 out_root: /tmp/libbar-out
266 To instead print this information in the JSON format, use the
268 json parameter, for example:
269 $ b info: libfoo/,json
271 In this case the output is a JSON array of objects which are the
273 serialized representation of the following C++ struct
274 project_info:
275 struct subproject
277 {
278 string path;
279 optional<string> name;
280 };
281 struct project_info
283 {
284 optional<string> project;
285 optional<string> version;
286 optional<string> summary;
287 optional<string> url;
288 string src_root;
289 string out_root;
290 optional<string> amalgamation;
291 vector<subproject> subprojects;
292 vector<string> operations;
293 vector<string> meta_operations;
294 vector<string> modules;
295 };
296 For example:
298 [
300 {
301 "project": "libfoo",
302 "version": "1.0.0",
303 "summary": "libfoo C++ library",
304 "src_root": "/tmp/libfoo",
305 "out_root": "/tmp/gcc-debug/libfoo",
306 "amalgamation": "..",
307 "subprojects": [
308 {
309 "path": "tests"
310 }
311 ],
312 "operations": [
313 "update",
314 "clean",
315 "test",
316 "update-for-test",
317 "install",
318 "uninstall",
319 "update-for-install"
320 ],
321 "meta-operations": [
322 "perform",
323 "configure",
324 "disfigure",
325 "dist",
326 "info"
327 ],
328 "modules": [
329 "version",
330 "config",
331 "test",
332 "install",
333 "dist"
334 ]
335 }
336 ]
337 See the JSON OUTPUT section below for details on the overall
339 properties of this format and the semantics of the struct seri‐
340 alization.
341 The build system has the following built-in and pre-defined operations:
343 update
345 Update a target.
346 clean
348 Clean a target.
349 test
351 Test a target. Performs update as a pre-operation. Implemented
352 by the test module.
353 update-for-test
355 Update a target for testing. This operation is equivalent to the
356 update pre-operation as executed by the test operation and can
357 be used to only update what is necessary for testing. Imple‐
358 mented by the test module.
359 install
361 Install a target. Performs update as a pre-operation. Imple‐
362 mented by the install module.
363 uninstall
365 Uninstall a target. Performs update as a pre-operation. Imple‐
366 mented by the install module.
367 update-for-install
369 Update a target for installation. This operation is equivalent
370 to the update pre-operation as executed by the install operation
371 and can be used to only update what is necessary for installa‐
372 tion. Implemented by the install module.
373 Note that buildspec and command line variable values are treated as
375 buildfile fragments and so can use quoting and escaping as well as con‐
376 tain variable expansions and evaluation contexts. However, to be more
377 usable on various platforms, escaping in these two situations is lim‐
378 ited to the effective sequences of \', \", \\, \$, and \( with all
379 other sequences interpreted as is. Together with double-quoting this is
380 sufficient to represent any value. For example:
381 $ b config.install.root=c:\projects\install
383 $ b "config.install.root='c:\Program Files\test\'"
384 $ b 'config.cxx.poptions=-DFOO_STR="foo"'
385
387 -v Print actual commands being executed. This options is equivalent
388 to --verbose 2.
389 -V Print all underlying commands being executed. This options is
391 equivalent to --verbose 3.
392 --quiet|-q
394 Run quietly, only printing error messages in most contexts. In
395 certain contexts (for example, while updating build system mod‐
396 ules) this verbosity level may be ignored. Use --silent to run
397 quietly in all contexts. This option is equivalent to --verbose
398 0.
399 --silent
401 Run quietly, only printing error messages in all contexts.
402 --verbose level
404 Set the diagnostics verbosity to level between 0 and 6. Level 0
405 disables any non-error messages (but see the difference between
406 --quiet and --silent) while level 6 produces lots of informa‐
407 tion, with level 1 being the default. The following additional
408 types of diagnostics are produced at each level:
409 1. High-level information messages.
411 2. Essential underlying commands being executed.
413 3. All underlying commands being executed.
415 4. Information that could be helpful to the user.
417 5. Information that could be helpful to the developer.
419 6. Even more detailed information.
421 --stat Display build statistics.
423 --progress
425 Display build progress. If printing to a terminal the progress
426 is displayed by default for low verbosity levels. Use --no-
427 progress to suppress.
428 --no-progress
430 Don't display build progress.
431 --jobs|-j num
433 Number of active jobs to perform in parallel. This includes both
434 the number of active threads inside the build system as well as
435 the number of external commands (compilers, linkers, etc)
436 started but not yet finished. If this option is not specified or
437 specified with the 0 value, then the number of available hard‐
438 ware threads is used.
439 --max-jobs|-J num
441 Maximum number of jobs (threads) to create. The default is 8x
442 the number of active jobs (--jobs|j) on 32-bit architectures and
443 32x on 64-bit. See the build system scheduler implementation for
444 details.
445 --queue-depth|-Q num
447 The queue depth as a multiplier over the number of active jobs.
448 Normally we want a deeper queue if the jobs take long (for exam‐
449 ple, compilation) and shorter if they are quick (for example,
450 simple tests). The default is 4. See the build system scheduler
451 implementation for details.
452 --file-cache impl
454 File cache implementation to use for intermediate build results.
455 Valid values are noop (no caching or compression) and sync-lz4
456 (no caching with synchronous LZ4 on-disk compression). If this
457 option is not specified, then a suitable default implementation
458 is used (currently sync-lz4).
459 --max-stack num
461 The maximum stack size in KBytes to allow for newly created
462 threads. For pthreads-based systems the driver queries the stack
463 size of the main thread and uses the same size for creating ad‐
464 ditional threads. This allows adjusting the stack size using fa‐
465 miliar mechanisms, such as ulimit. Sometimes, however, the
466 stack size of the main thread is excessively large. As a re‐
467 sult, the driver checks if it is greater than a predefined limit
468 (64MB on 64-bit systems and 32MB on 32-bit ones) and caps it to
469 a more sensible value (8MB) if that's the case. This option al‐
470 lows you to override this check with the special zero value in‐
471 dicating that the main thread stack size should be used as is.
472 --serial-stop|-s
474 Run serially and stop at the first error. This mode is useful to
475 investigate build failures that are caused by build system er‐
476 rors rather than compilation errors. Note that if you don't want
477 to keep going but still want parallel execution, add --jobs|-j
478 (for example -j 0 for default concurrency).
479 --dry-run|-n
481 Print commands without actually executing them. Note that com‐
482 mands that are required to create an accurate build state will
483 still be executed and the extracted auxiliary dependency infor‐
484 mation saved. In other words, this is not the "don't touch the
485 filesystem" mode but rather "do minimum amount of work to show
486 what needs to be done". Note also that only the perform meta-op‐
487 eration supports this mode.
488 --match-only
490 Match the rules but do not execute the operation. This mode is
491 primarily useful for profiling.
492 --no-external-modules
494 Don't load external modules during project bootstrap. Note that
495 this option can only be used with meta-operations that do not
496 load the project's buildfiles, such as info.
497 --structured-result fmt
499 Write the result of execution in a structured form. In this
500 mode, instead of printing to stderr diagnostics messages about
501 the outcome of executing actions on targets, the driver writes
502 to stdout a machine-readable result description in the specified
503 format. Valid values for this option are lines and json. Note
504 that currently only the perform meta-operation supports the
505 structured result output.
506 If the output format is lines, then the result is written one
508 line per the buildspec action/target pair. Each line has the
509 following form:
510 state meta-operation operation target
512 Where state can be one of unchanged, changed, or failed. If the
514 action is a pre or post operation, then the outer operation is
515 specified in parenthesis. For example:
516 unchanged perform update(test) /tmp/dir{hello/}
518 changed perform test /tmp/hello/exe{test}
519 If the output format is json, then the output is a JSON array of
521 objects which are the serialized representation of the following
522 C++ struct target_action_result:
523 struct target_action_result
525 {
526 string target;
527 string quoted_target;
528 string target_type;
529 optional<string> target_path;
530 string meta_operation;
531 string operation;
532 optional<string> outer_operation;
533 string state;
534 };
535 For example:
537 [
539 {
540 "target": "/tmp/dir{hello/}",
541 "quoted_target": "/tmp/dir{hello/}",
542 "target_type": "dir",
543 "target_path": "/tmp/hello",
544 "meta_operation": "perform",
545 "operation": "update",
546 "outer_operation": "test",
547 "state": "unchanged"
548 },
549 {
550 "target": "/tmp/dir{hello/}",
551 "quoted_target": "/tmp/dir{hello/}",
552 "target_type": "dir",
553 "target_path": "/tmp/hello",
554 "meta_operation": "perform",
555 "operation": "test",
556 "state": "changed"
557 }
558 ]
559 See the JSON OUTPUT section below for details on the overall
561 properties of this format and the semantics of the struct seri‐
562 alization.
563 The target member is a "display" target name, the same as in the
565 lines format. The quoted_target member is a target name that, if
566 required, is quoted so that it can be passed back to the driver
567 on the command line. The target_type member is the type of tar‐
568 get. The target_path member is an absolute path to the target if
569 the target type is path-based or dir.
570 --mtime-check
572 Perform file modification time sanity checks. These checks can
573 be helpful in diagnosing spurious rebuilds and are enabled by
574 default on Windows (which is known not to guarantee monotoni‐
575 cally increasing mtimes) and for the staged version of the build
576 system on other platforms. Use --no-mtime-check to disable.
577 --no-mtime-check
579 Don't perform file modification time sanity checks. See --mtime-
580 check for details.
581 --dump phase
583 Dump the build system state after the specified phase. Valid
584 phase values are load (after loading buildfiles) and match (af‐
585 ter matching rules to targets). Repeat this option to dump the
586 state after multiple phases.
587 --trace-match target
589 Trace rule matching for the specified target. This is primarily
590 useful during troubleshooting. Repeat this option to trace mul‐
591 tiple targets.
592 --trace-execute target
594 Trace rule execution for the specified target. This is primarily
595 useful during troubleshooting. Repeat this option to trace mul‐
596 tiple targets.
597 --no-column
599 Don't print column numbers in diagnostics.
600 --no-line
602 Don't print line and column numbers in diagnostics.
603 --buildfile path
605 The alternative file to read build information from. The default
606 is buildfile or build2file, depending on the project's build
607 file/directory naming scheme. If path is '-', then read from
608 stdin. Note that this option only affects the files read as part
609 of the buildspec processing. Specifically, it has no effect on
610 the source and include directives. As a result, this option is
611 primarily intended for testing rather than changing the build
612 file names in real projects.
613 --config-guess path
615 The path to the config.guess(1) script that should be used to
616 guess the host machine triplet. If this option is not specified,
617 then b will fall back on to using the target it was built for as
618 host.
619 --config-sub path
621 The path to the config.sub(1) script that should be used to
622 canonicalize machine triplets. If this option is not specified,
623 then b will use its built-in canonicalization support which
624 should be sufficient for commonly-used platforms.
625 --pager path
627 The pager program to be used to show long text. Commonly used
628 pager programs are less and more. You can also specify addi‐
629 tional options that should be passed to the pager program with
630 --pager-option. If an empty string is specified as the pager
631 program, then no pager will be used. If the pager program is not
632 explicitly specified, then b will try to use less. If it is not
633 available, then no pager will be used.
634 --pager-option opt
636 Additional option to be passed to the pager program. See --pager
637 for more information on the pager program. Repeat this option to
638 specify multiple pager options.
639 --options-file file
641 Read additional options from file. Each option should appear on
642 a separate line optionally followed by space or equal sign (=)
643 and an option value. Empty lines and lines starting with # are
644 ignored. Option values can be enclosed in double (") or single
645 (') quotes to preserve leading and trailing whitespaces as well
646 as to specify empty values. If the value itself contains trail‐
647 ing or leading quotes, enclose it with an extra pair of quotes,
648 for example '"x"'. Non-leading and non-trailing quotes are in‐
649 terpreted as being part of the option value.
650 The semantics of providing options in a file is equivalent to
652 providing the same set of options in the same order on the com‐
653 mand line at the point where the --options-file option is speci‐
654 fied except that the shell escaping and quoting is not required.
655 Repeat this option to specify more than one options file.
656 --default-options dir
658 The directory to load additional default options files from.
659 --no-default-options
661 Don't load default options files.
662 --help Print usage information and exit.
664 --version
666 Print version and exit.
667
669 Instead of having a separate config file format for tool configuration,
670 the build2 toolchain uses default options files which contain the same
671 options as what can be specified on the command line. The default op‐
672 tions files are like options files that one can specify with --options-
673 file except that they are loaded by default.
674 The default options files for the build system driver are called b.op‐
676 tions and are searched for in the .build2/ subdirectory of the home di‐
677 rectory and in the system directory (for example, /etc/build2/) if con‐
678 figured. Note that besides options these files can also contain global
679 variable overrides.
680 Once the search is complete, the files are loaded in the reverse order,
682 that is, beginning from the system directory (if any), followed by the
683 home directory, and finishing off with the options specified on the
684 command line. In other words, the files are loaded from the more
685 generic to the more specific with the command line options having the
686 ability to override any values specified in the default options files.
687 If a default options file contains --no-default-options, then the
689 search is stopped at the directory containing this file and no outer
690 files are loaded. If this option is specified on the command line, then
691 none of the default options files are searched for or loaded.
692 An additional directory containing default options files can be speci‐
694 fied with --default-options. Its configuration files are loaded after
695 the home directory.
696 The order in which default options files are loaded is traced at the
698 verbosity level 3 (-V option) or higher.
699
701 Commands that support the JSON output specify their formats as a seri‐
702 alized representation of a C++ struct or an array thereof. For example:
703 struct package
705 {
706 string name;
707 };
708 struct configuration
710 {
711 uint64_t id;
712 string path;
713 optional<string> name;
714 bool default;
715 vector<package> packages;
716 };
717 An example of the serialized JSON representation of struct configura‐
719 tion:
720 {
722 "id": 1,
723 "path": "/tmp/hello-gcc",
724 "name": "gcc",
725 "default": true,
726 "packages": [
727 {
728 "name": "hello"
729 }
730 ]
731 }
732 This sections provides details on the overall properties of such for‐
734 mats and the semantics of the struct serialization.
735 The order of members in a JSON object is fixed as specified in the cor‐
737 responding struct. While new members may be added in the future (and
738 should be ignored by older consumers), the semantics of the existing
739 members (including whether the top-level entry is an object or array)
740 may not change.
741 An object member is required unless its type is optional<>, bool, or
743 vector<> (array). For bool members absent means false. For vector<>
744 members absent means empty. An empty top-level array is always present.
745 For example, the following JSON text is a possible serialization of the
747 above struct configuration:
748 {
750 "id": 1,
751 "path": "/tmp/hello-gcc"
752 }
753
755 Non-zero exit status is returned in case of an error.
756
758 The HOME environment variable is used to determine the user's home di‐
759 rectory. If it is not set, then getpwuid(3) is used instead. This value
760 is used to shorten paths printed in diagnostics by replacing the home
761 directory with ~/. It is also made available to buildfile's as the
762 build.home variable.
763 The BUILD2_VAR_OVR environment variable is used to propagate global
765 variable overrides to nested build system driver invocations. Its value
766 is a list of global variable assignments separated with newlines.
767 The BUILD2_DEF_OPT environment variable is used to suppress loading of
769 default options files in nested build system driver invocations. Its
770 values are false or 0 to suppress and true or 1 to load.
771
773 Send bug reports to the users@build2.org mailing list.
774
776 Copyright (c) 2014-2022 the build2 authors.
777 Permission is granted to copy, distribute and/or modify this document
779 under the terms of the MIT License.
780build2 0.15.0 July 2022 b(1)