From e5c589d271c62f57cd2e7eb7d9841f67d8845ff4 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Mon, 13 Aug 2012 15:02:09 -0400
Subject: [PATCH] Don't allocate empty lists

This saves about 4 MB when evaluating a NixOS system configuration.
---
 src/libexpr/eval.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 517a1151e..cb7c22e29 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -348,7 +348,7 @@ void EvalState::mkList(Value & v, unsigned int length)
 {
     v.type = tList;
     v.list.length = length;
-    v.list.elems = (Value * *) GC_MALLOC(length * sizeof(Value *));
+    v.list.elems = length ? (Value * *) GC_MALLOC(length * sizeof(Value *)) : 0;
     nrListElems += length;
 }