From b496ffbe55f1a0604bfcf0eeb92a48f2fd504d03 Mon Sep 17 00:00:00 2001
From: mingchuan <ming@culpring.com>
Date: Tue, 16 May 2017 04:45:52 +0800
Subject: [PATCH] opencv: Fix OpenCV build on non NixOS platform

OpenCV's CMakeFile will use libraries in /lib and /lib64 if it can
find libraries from those paths. However, it causes
build failure because nix detects impure paths being used.
---
 pkgs/development/libraries/opencv/3.x.nix     | 6 ++++++
 pkgs/development/libraries/opencv/default.nix | 5 +++++
 2 files changed, 11 insertions(+)

diff --git a/pkgs/development/libraries/opencv/3.x.nix b/pkgs/development/libraries/opencv/3.x.nix
index 275c1cddab0..5c7972eb2fa 100644
--- a/pkgs/development/libraries/opencv/3.x.nix
+++ b/pkgs/development/libraries/opencv/3.x.nix
@@ -78,6 +78,12 @@ stdenv.mkDerivation rec {
         ln -s "${bootdescFiles}/$name" "$NIX_BUILD_TOP/opencv_contrib/xfeatures2d/src/$name"
       done
     '');
+
+  # This prevents cmake from using libraries in impure paths (which causes build failure on non NixOS)
+  postPatch = ''
+    sed -i '/Add these standard paths to the search paths for FIND_LIBRARY/,/^\s*$/{d}' CMakeLists.txt
+  '';
+
   preConfigure =
     (let version  = "20151201";
          md5      = "808b791a6eac9ed78d32a7666804320e";
diff --git a/pkgs/development/libraries/opencv/default.nix b/pkgs/development/libraries/opencv/default.nix
index 37b33c21a30..d7824dbed34 100644
--- a/pkgs/development/libraries/opencv/default.nix
+++ b/pkgs/development/libraries/opencv/default.nix
@@ -35,6 +35,11 @@ stdenv.mkDerivation rec {
       ./no-build-info.patch
     ];
 
+  # This prevents cmake from using libraries in impure paths (which causes build failure on non NixOS)
+  postPatch = ''
+    sed -i '/Add these standard paths to the search paths for FIND_LIBRARY/,/^\s*$/{d}' CMakeLists.txt
+  '';
+
   outputs = [ "out" "dev" ];
 
   buildInputs =