csig_fix.diff

diff --git a/scons-local-2.3.0/SCons/Node/__init__.py b/scons-local-2.3.0/SCons/Node/__init__.py
index ece4a5a..b2ccc60 100644
--- a/scons-local-2.3.0/SCons/Node/__init__.py
+++ b/scons-local-2.3.0/SCons/Node/__init__.py
@@ -1015,6 +1015,38 @@ class Node(object):
     def Decider(self, function):
         SCons.Util.AddMethod(self, function, 'changed_since_last_build')
 
+    def _build_dependency_map(self, binfo):
+        """
+        Dependency name -> node info object
+        """
+
+        # For an "empty" binfo properties like bsources
+        # do not exist: check this to avoid exception.
+        if (len(binfo.bsourcesigs) + len(binfo.bdependsigs) + \
+                len(binfo.bimplicitsigs)) == 0:
+            return {}
+
+        pairs = [
+            (binfo.bsources, binfo.bsourcesigs),
+            (binfo.bdepends, binfo.bdependsigs),
+            (binfo.bimplicit, binfo.bimplicitsigs)
+            ]
+
+        m = {}
+        for children, signatures in pairs:
+            for child, signature in zip(children, signatures):
+                schild = str(child)
+                m[schild] = signature
+        return m
+
+    def _get_previous_signatures(self, dmap, children):
+        prev = []
+        for c in map(str, children):
+            # If there is no previous signature,
+            # we place None in the corresponding position.
+            prev.append(dmap.get(c))
+        return prev
+
     def changed(self, node=None):
         """
         Returns if the node is up-to-date with respect to the BuildInfo
@@ -1037,20 +1069,17 @@ class Node(object):
         result = False
 
         bi = node.get_stored_info().binfo
-        then = bi.bsourcesigs + bi.bdependsigs + bi.bimplicitsigs
+        dmap = self._build_dependency_map(bi)
         children = self.children()
 
-        diff = len(children) - len(then)
+        diff = len(children) - len(dmap)
         if diff:
             # The old and new dependency lists are different lengths.
             # This always indicates that the Node must be rebuilt.
-            # We also extend the old dependency list with enough None
-            # entries to equal the new dependency list, for the benefit
-            # of the loop below that updates node information.
-            then.extend([None] * diff)
-            if t: Trace(': old %s new %s' % (len(then), len(children)))
             result = True
 
+        then = self._get_previous_signatures(dmap, children)
+
         for child, prev_ni in zip(children, then):
             if child.changed_since_last_build(self, prev_ni):
                 if t: Trace(': %s changed' % child)