1 files changed, 25 insertions, 0 deletions
diff --git a/src/libstore/derived-path-map.hh b/src/libstore/derived-path-map.hh
index 9ce58206e..4a2c90733 100644
--- a/src/libstore/derived-path-map.hh
+++ b/src/libstore/derived-path-map.hh
@@ -48,6 +48,8 @@ struct DerivedPathMap {
          * The map of the root node.
          */
         Map childMap;
+
+        DECLARE_CMP(ChildNode);
     };
 
     /**
@@ -60,6 +62,8 @@ struct DerivedPathMap {
      */
     Map map;
 
+    DECLARE_CMP(DerivedPathMap);
+
     /**
      * Find the node for `k`, creating it if needed.
      *
@@ -68,6 +72,27 @@ struct DerivedPathMap {
      * by changing this node.
      */
     ChildNode & ensureSlot(const SingleDerivedPath & k);
+
+    /**
+     * Like `ensureSlot` but does not create the slot if it doesn't exist.
+     *
+     * Read the entire description of `ensureSlot` to understand an
+     * important caveat here that "have slot" does *not* imply "key is
+     * set in map". To ensure a key is set one would need to get the
+     * child node (with `findSlot` or `ensureSlot`) *and* check the
+     * `ChildNode::value`.
+     */
+    ChildNode * findSlot(const SingleDerivedPath & k);
 };
 
+
+DECLARE_CMP_EXT(
+    template<>,
+    DerivedPathMap<std::set<std::string>>::,
+    DerivedPathMap<std::set<std::string>>);
+DECLARE_CMP_EXT(
+    template<>,
+    DerivedPathMap<std::set<std::string>>::ChildNode::,
+    DerivedPathMap<std::set<std::string>>::ChildNode);
+
 }