3 files changed, 7 insertions, 24 deletions
diff --git a/build/algorithm b/build/algorithm
index 2dc7164..bc756c2 100644
--- a/build/algorithm
+++ b/build/algorithm
@@ -70,7 +70,8 @@ namespace build
 
   // Inject dependency on the parent directory's fsdir{}, unless it is
   // the project's out_root (or is outside of any project; say, for
-  // example, an install directory).
+  // example, an install directory). Normally this function is called
+  // from the rule's apply() function.
   //
   void
   inject_parent_fsdir (action, target&);
diff --git a/build/algorithm.cxx b/build/algorithm.cxx
index 2529e13..abae023 100644
--- a/build/algorithm.cxx
+++ b/build/algorithm.cxx
@@ -206,26 +206,11 @@ namespace build
     if (!d.sub (out_root) || d == out_root)
       return;
 
-    prerequisite& p (
-      s.prerequisites.insert (
-        fsdir::static_type,
-        d,
-        string (),
-        nullptr,
-        s,
-        trace).first);
-
-    // This function is normally called from match() which means
-    // it can be called several times if we are performing several
-    // operations (e.g., clean update). Since it is a fairly common
-    // pattern to add this prerequisite at the end, do a quick check
-    // if the last prerequisite is already what we are about to add.
-    //
-    if (!t.prerequisites.empty () && &t.prerequisites.back ().get () == &p)
-      return;
+    level5 ([&]{trace << "for " << t;});
 
-    level5 ([&]{trace << "injecting prerequisite for " << t;});
-    t.prerequisites.emplace_back (p);
+    fsdir& dt (search<fsdir> (d, string (), nullptr, &s));
+    match (a, dt);
+    t.prerequisite_targets.emplace_back (&dt);
   }
 
   target_state
diff --git a/build/cxx/rule.cxx b/build/cxx/rule.cxx
index 72c4e35..9564638 100644
--- a/build/cxx/rule.cxx
+++ b/build/cxx/rule.cxx
@@ -610,10 +610,7 @@ namespace build
       // Process prerequisites: do rule chaining for C and C++ source
       // files as well as search and match.
       //
-      group_prerequisites gp (t);
-      t.prerequisite_targets.reserve (gp.size ());
-
-      for (prerequisite_ref& pr: gp)
+      for (prerequisite_ref& pr: group_prerequisites (t))
       {
         bool group (!pr.belongs (t)); // Target group's prerequisite.