Ignore prerequisite mtimes that are not linker inputs

This makes sure, for example, that we don't unnecessarily re-link an
executable when its testscript prerequisite is changes.

1 files changed, 15 insertions, 0 deletions

diff --git a/build2/target b/build2/target
index 1b75da3..dd9461c 100644
--- a/build2/target
+++ b/build2/target
@@ -1098,6 +1098,21 @@ namespace build2
       mtime_ = mt;
     }
 
+    // Return true if this target is newer than the specified timestamp.
+    //
+    bool
+    newer (timestamp mt)
+    {
+      timestamp mp (mtime ());
+
+      // What do we do if timestamps are equal? This can happen, for example,
+      // on filesystems that don't have subsecond resolution. There is not
+      // much we can do here except detect the case where the target was
+      // changed on this run.
+      //
+      return mt < mp || (mt == mp && state () == target_state::changed);
+    }
+
   protected:
     // Return timestamp_unknown if the mtime cannot be loaded.
     //