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-rw-r--r--libbuild2/target.hxx35
1 files changed, 33 insertions, 2 deletions
diff --git a/libbuild2/target.hxx b/libbuild2/target.hxx
index e935477..01e82bb 100644
--- a/libbuild2/target.hxx
+++ b/libbuild2/target.hxx
@@ -409,7 +409,7 @@ namespace build2
// usually needed is to derive its path.
//
// - Unless declared, members are discovered lazily, they are only known
- // after the group's rule's apply() call.
+ // after the matching rule's apply() call.
//
// - Only declared members can be used as prerequisites but all can be
// used as targets (e.g., to set variables, etc).
@@ -439,7 +439,11 @@ namespace build2
// target for the ad hoc members (with a special target type that rules
// like install could recognize). See also the variable lookup semantics.
// We could also probably support see_through via an attribute or some
- // such.
+ // such. Or perhaps such cases should be handled through explicit groups
+ // and the ad hoc semantics is left to the non-see_through "primary
+ // targets with a bunch of subordinates" cases. In other words, if the
+ // members are "equal/symmetrical", then perhaps an explicit group is the
+ // correct approach.
//
const_ptr<target> adhoc_member = nullptr;
@@ -2148,6 +2152,33 @@ namespace build2
static const target_type static_type;
};
+ // Mtime-based group target.
+ //
+ // Used to support explicit groups in buildfiles: can be derived from,
+ // populated with static members using the group{foo}<...> syntax, and
+ // matched with an ad hoc recipe/rule, including dynamic member extraction.
+ // Note that it is not see-through but a derived group can be made see-
+ // through via the [see_through] attribute.
+ //
+ // Note that normally you wouldn't use it as a base for a custom group
+ // defined in C++, instead deriving from mtime_target directly and using a
+ // custom members layout more appropriate for the group's semantics.
+ //
+ class LIBBUILD2_SYMEXPORT group: public mtime_target
+ {
+ public:
+ vector<reference_wrapper<const target>> static_members;
+
+ group (context& c, dir_path d, dir_path o, string n)
+ : mtime_target (c, move (d), move (o), move (n))
+ {
+ dynamic_type = &static_type;
+ }
+
+ public:
+ static const target_type static_type;
+ };
+
// Alias target. It represents a list of targets (its prerequisites)
// as a single "name".
//