5 files changed, 95 insertions, 19 deletions

diff --git a/libbuild2/adhoc-rule-buildscript.cxx b/libbuild2/adhoc-rule-buildscript.cxx
index fa60556..25ef1b7 100644
--- a/libbuild2/adhoc-rule-buildscript.cxx
+++ b/libbuild2/adhoc-rule-buildscript.cxx
@@ -456,17 +456,13 @@ namespace build2
     // If we have any update during match prerequisites, now is the time to
     // update them.
     //
-    // Note also that we ignore the result and whether it renders us out of
-    // date, leaving it to the common execute logic in perform_update_*().
+    // Note that we ignore the result and whether it renders us out of date,
+    // leaving it to the common execute logic in perform_update_*().
+    //
+    // Note also that update_during_match() spoils prerequisite_target::data.
     //
     if (a == perform_update_id)
-    {
-      for (const prerequisite_target& pt: pts)
-      {
-        if ((pt.include & 2) != 0)
-          update_during_match (trace, a, *pt.target);
-      }
-    }
+      update_during_match (trace, a, pts, 2 /* mask */);
 
     // See if this is not update or not on a file-based target.
     //
diff --git a/libbuild2/algorithm.cxx b/libbuild2/algorithm.cxx
index cbf0495..d72e95e 100644
--- a/libbuild2/algorithm.cxx
+++ b/libbuild2/algorithm.cxx
@@ -2119,6 +2119,75 @@ namespace build2
     }
   }
 
+  bool
+  update_during_match (tracer& trace,
+                       action a,
+                       prerequisite_targets& pts,
+                       uintptr_t mask)
+  {
+    // On the first pass detect and handle unchanged tragets. Note that we
+    // have to do it in a separate pass since we cannot call matched_state()
+    // once we've switched the phase.
+    //
+    context* ctx (nullptr);
+
+    for (prerequisite_target& p: pts)
+    {
+      if ((p.include & mask) != 0)
+      {
+        if (p.target != nullptr)
+        {
+          const target& pt (*p.target);
+
+          target_state os (pt.matched_state (a));
+
+          if (os != target_state::unchanged)
+          {
+            if (ctx == nullptr)
+              ctx = &pt.ctx;
+
+            p.data = static_cast<uintptr_t> (os);
+            continue;
+          }
+        }
+
+        p.data = 0;
+      }
+    }
+
+    // If all unchanged, we are done.
+    //
+    if (ctx == nullptr)
+      return false;
+
+    phase_switch ps (*ctx, run_phase::execute);
+
+    bool r (false);
+
+    for (prerequisite_target& p: pts)
+    {
+      if ((p.include & mask) != 0 && p.data != 0)
+      {
+        const target& pt (*p.target);
+
+        target_state os (static_cast<target_state> (p.data));
+        target_state ns (execute_direct (a, pt));
+
+        if (ns != os && ns != target_state::unchanged)
+        {
+          l6 ([&]{trace << "updated " << pt
+                        << "; old state " << os
+                        << "; new state " << ns;});
+          r = true;
+        }
+
+        p.data = 0;
+      }
+    }
+
+    return r;
+  }
+
   static inline void
   blank_adhoc_member (const target*&)
   {
diff --git a/libbuild2/algorithm.hxx b/libbuild2/algorithm.hxx
index c30680a..788138b 100644
--- a/libbuild2/algorithm.hxx
+++ b/libbuild2/algorithm.hxx
@@ -609,6 +609,19 @@ namespace build2
                        action, const target&,
                        timestamp = timestamp_unknown);
 
+  // As above, but update all the targets in prerequisite_targets that have
+  // the specified mask in prerequisite_target::include. Return true if any of
+  // them have changed.
+  //
+  // Note that this function spoils prerequisite_target::data (which is used
+  // for temporary storage). But it resets data to 0 once done.
+  //
+  LIBBUILD2_SYMEXPORT bool
+  update_during_match (tracer&,
+                       action,
+                       prerequisite_targets&,
+                       uintptr_t mask);
+
   // The default prerequisite execute implementation. Call execute_async() on
   // each non-ignored (non-NULL) prerequisite target in a loop and then wait
   // for their completion. Return target_state::changed if any of them were
diff --git a/libbuild2/cc/link-rule.cxx b/libbuild2/cc/link-rule.cxx
index c507155..b72e5a0 100644
--- a/libbuild2/cc/link-rule.cxx
+++ b/libbuild2/cc/link-rule.cxx
@@ -1226,17 +1226,13 @@ namespace build2
       // example, object file matches may need the headers to be already
       // updated).
       //
-      // Note also that we ignore the result and whether it renders us out of
-      // date, leaving it to the common execute logic in perform_update().
+      // Note that we ignore the result and whether it renders us out of date,
+      // leaving it to the common execute logic in perform_update().
+      //
+      // Note also that update_during_match() spoils prerequisite_target::data.
       //
       if (update_match)
-      {
-        for (const prerequisite_target& pto: pts)
-        {
-          if ((pto.include & 2) != 0)
-            update_during_match (trace, a, *pto.target);
-        }
-      }
+        update_during_match (trace, a, pts, 2 /* mask */);
 
       // Check if we have any binful utility libraries.
       //
diff --git a/libbuild2/target-state.hxx b/libbuild2/target-state.hxx
index 3457b13..48d683d 100644
--- a/libbuild2/target-state.hxx
+++ b/libbuild2/target-state.hxx
@@ -18,9 +18,11 @@ namespace build2
   // Note that postponed is "greater" than unchanged since it may result in
   // the changed state.
   //
+  // Note also that value 0 is available to indicate absent/invalid state.
+  //
   enum class target_state: uint8_t
   {
-    unknown,
+    unknown = 1,
     unchanged,
     postponed,
     busy,