[ceph.git] / ceph / src / boost / tools / build / src / tools / features / relevant-feature.jam

# Copyright 2017 Steven Watanabe
# Distributed under the Boost Software License, Version 1.0.
# (See accompanying file LICENSE.txt or copy at
# https://www.bfgroup.xyz/b2/LICENSE.txt)

import feature ;

#| tag::doc[]

[[bbv2.builtin.features.relevant]]`relevant`::
*Allowed values:* the name of any feature.
+
Indicates which other features are relevant for a given target. It is usually
not necessary to manage it explicitly, as B2 can deduce it in most
cases. Features which are not relevant will not affect target paths, and will
not cause conflicts.
+
* A feature will be considered relevant if any of the following are true
+
** It is referenced by `toolset.flags` or `toolset.uses-features`
** It is used by the requirements of a generator
** It is a sub-feature of a relevant feature
** It has a sub-feature which is relevant
** It is a composite feature, and any composed feature is relevant
** It affects target alternative selection for a main target
** It is a propagated feature and is relevant for any dependency
** It is relevant for any dependency created by the same main target
** It is used in the condition of a conditional property and the corresponding
  value is relevant
** It is explicitly named as relevant
+
* Relevant features cannot be automatically deduced in the following cases:
+
** Indirect conditionals. Solution: return properties of the form
`<relevant>result-feature:<relevant>condition-feature`
+
NOTE: This isn't really a conditional, although for most purposes it functions
like one. In particular, it does not support multiple comma-separated elements
in the condition, and it does work correctly even in contexts where conditional
properties are not allowed
** Action rules that read properties. Solution: add toolset.uses-features to
  tell B2 that the feature is actually used.
** Generators and targets that manipulate property-sets directly. Solution:
  set <relevant> manually.

|# # end::doc[]

feature.feature relevant : : incidental free ;
Commit	Line	Data
11fdf7f2 TL	1	# Copyright 2017 Steven Watanabe
11fdf7f2 TL	2	# Distributed under the Boost Software License, Version 1.0.
1e59de90 TL	3	# (See accompanying file LICENSE.txt or copy at
1e59de90 TL	4	# https://www.bfgroup.xyz/b2/LICENSE.txt)
11fdf7f2	5
11fdf7f2 TL	6	import feature ;
11fdf7f2 TL	7
f67539c2 TL	8	#\| tag::doc[]
	9
	10	[[bbv2.builtin.features.relevant]]`relevant`::
	11	Allowed values: the name of any feature.
	12	+
	13	Indicates which other features are relevant for a given target. It is usually
	14	not necessary to manage it explicitly, as B2 can deduce it in most
	15	cases. Features which are not relevant will not affect target paths, and will
	16	not cause conflicts.
	17	+
	18	* A feature will be considered relevant if any of the following are true
	19	+
	20	** It is referenced by `toolset.flags` or `toolset.uses-features`
	21	** It is used by the requirements of a generator
	22	** It is a sub-feature of a relevant feature
	23	** It has a sub-feature which is relevant
	24	** It is a composite feature, and any composed feature is relevant
	25	** It affects target alternative selection for a main target
	26	** It is a propagated feature and is relevant for any dependency
	27	** It is relevant for any dependency created by the same main target
	28	** It is used in the condition of a conditional property and the corresponding
	29	value is relevant
	30	** It is explicitly named as relevant
	31	+
	32	* Relevant features cannot be automatically deduced in the following cases:
	33	+
	34	** Indirect conditionals. Solution: return properties of the form
	35	`<relevant>result-feature:<relevant>condition-feature`
	36	+
	37	NOTE: This isn't really a conditional, although for most purposes it functions
	38	like one. In particular, it does not support multiple comma-separated elements
	39	in the condition, and it does work correctly even in contexts where conditional
	40	properties are not allowed
	41	** Action rules that read properties. Solution: add toolset.uses-features to
	42	tell B2 that the feature is actually used.
	43	** Generators and targets that manipulate property-sets directly. Solution:
	44	set <relevant> manually.
	45
	46	\|# # end::doc[]
	47
11fdf7f2	48	feature.feature relevant : : incidental free ;