From bc08fa99f1adc02cf25c21a7f89f2f322abca150 Mon Sep 17 00:00:00 2001
From: John Wiegley <johnw@newartisans.com>
Date: Tue, 15 Apr 2014 05:04:27 -0500
Subject: [PATCH] Fix flex for building on darwin systems

---
 pkgs/development/tools/parsing/flex/2.5.39.nix | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/pkgs/development/tools/parsing/flex/2.5.39.nix b/pkgs/development/tools/parsing/flex/2.5.39.nix
index c5337d647de3..f12f89f6e24c 100644
--- a/pkgs/development/tools/parsing/flex/2.5.39.nix
+++ b/pkgs/development/tools/parsing/flex/2.5.39.nix
@@ -12,6 +12,10 @@ stdenv.mkDerivation {
 
   propagatedNativeBuildInputs = [ m4 ];
 
+  postConfigure = stdenv.lib.optionalString stdenv.isDarwin ''
+    sed -i Makefile -e 's/-no-undefined//;'
+  '';
+
   crossAttrs = {
     preConfigure = ''
       export ac_cv_func_malloc_0_nonnull=yes