From 680c9a788c23e501699e78662a45bca6bb918e1a Mon Sep 17 00:00:00 2001
From: Markus Vieth <mvieth@techfak.uni-bielefeld.de>
Date: Fri, 28 Jul 2023 11:02:59 +0200
Subject: [PATCH] Make Flann optional Fixes
 https://github.com/PointCloudLibrary/pcl/issues/5654 cmake prints a warning
 if Flann is not found PCL modules that can be built without Flann: common,
 octree, geometry, io, ml, stereo, tools

---
 CMakeLists.txt | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f1795cb72a9..b253942cf51 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -321,10 +321,14 @@ find_package(Threads REQUIRED)
 # Eigen3 (required)
 find_package(Eigen3 3.3 REQUIRED NO_MODULE)
 
-# FLANN (required)
-find_package(FLANN 1.9.1 REQUIRED)
-if(NOT (${FLANN_LIBRARY_TYPE} MATCHES ${PCL_FLANN_REQUIRED_TYPE}) AND NOT (${PCL_FLANN_REQUIRED_TYPE} MATCHES "DONTCARE"))
-  message(FATAL_ERROR "Flann was selected with ${PCL_FLANN_REQUIRED_TYPE} but found as ${FLANN_LIBRARY_TYPE}")
+# FLANN
+find_package(FLANN 1.9.1)
+if(NOT FLANN_FOUND)
+  message(WARNING "Flann was not found, so many PCL modules will not be built!")
+else()
+  if(NOT (${FLANN_LIBRARY_TYPE} MATCHES ${PCL_FLANN_REQUIRED_TYPE}) AND NOT (${PCL_FLANN_REQUIRED_TYPE} MATCHES "DONTCARE"))
+    message(FATAL_ERROR "Flann was selected with ${PCL_FLANN_REQUIRED_TYPE} but found as ${FLANN_LIBRARY_TYPE}")
+  endif()
 endif()
 
 # libusb