From 056d28a60110975332d8cb0c08990a1d3d8060a7 Mon Sep 17 00:00:00 2001
From: Tuomas Tynkkynen <tuomas@tuxera.com>
Date: Mon, 19 Feb 2018 22:47:25 +0200
Subject: [PATCH] libexpr: Don't create lots of temporary strings in
 Bindings::lexicographicOrder

Avoids ~180,000 string temporaries created when evaluating a headless
NixOS system.
---
 src/libexpr/attr-set.hh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libexpr/attr-set.hh b/src/libexpr/attr-set.hh
index e1fc2bf6d..3119a1848 100644
--- a/src/libexpr/attr-set.hh
+++ b/src/libexpr/attr-set.hh
@@ -83,7 +83,7 @@ public:
         for (size_t n = 0; n < size_; n++)
             res.emplace_back(&attrs[n]);
         std::sort(res.begin(), res.end(), [](const Attr * a, const Attr * b) {
-            return (string) a->name < (string) b->name;
+            return (const string &) a->name < (const string &) b->name;
         });
         return res;
     }