* Use a symbol table to represent identifiers and attribute names

efficiently.  The symbol table ensures that there is only one copy
  of each symbol, thus allowing symbols to be compared efficiently
  using a pointer equality test.

src/nix-instantiate/nix-instantiate.cc

@@ -28,7 +28,7 @@ static Expr * parseStdin(EvalState & state)
     startNest(nest, lvlTalkative, format("parsing standard input"));
     string s, s2;
     while (getline(std::cin, s2)) s += s2 + "\n";
-    return parseExprFromString(s, absPath("."));
+    return parseExprFromString(state, s, absPath("."));
 }
 
 
@@ -136,7 +136,7 @@ void run(Strings args)
 
     foreach (Strings::iterator, i, files) {
         Path path = absPath(*i);
-        Expr * e = parseExprFromFile(path);
+        Expr * e = parseExprFromFile(state, path);
         processExpr(state, attrPaths, parseOnly, strict, autoArgs,
             evalOnly, xmlOutput, e);
     }