From: Jochen Sprickerhof <git@jochen.sprickerhof.de>
Date: Sun, 14 Oct 2018 00:25:05 +0200
Subject: Use system version of liblz4

Also make sure that flann_cpp is linked against LZ4.
---
 CMakeLists.txt                     | 3 +++
 cmake/flann.pc.in                  | 2 +-
 examples/CMakeLists.txt            | 3 +++
 src/cpp/CMakeLists.txt             | 8 ++++++--
 src/cpp/flann/util/serialization.h | 4 ++--
 5 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index a01fb7a..995e54e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -142,6 +142,9 @@ if (BUILD_CUDA_LIB)
     endif(CUDA_FOUND)
 endif(BUILD_CUDA_LIB)
 
+find_package(PkgConfig REQUIRED)
+pkg_check_modules(LZ4 REQUIRED liblz4)
+
 #set the C/C++ include path to the "include" directory
 include_directories(BEFORE ${PROJECT_SOURCE_DIR}/src/cpp)
 
diff --git a/cmake/flann.pc.in b/cmake/flann.pc.in
index 82eee5e..07b8d64 100644
--- a/cmake/flann.pc.in
+++ b/cmake/flann.pc.in
@@ -8,6 +8,6 @@ Name: @PROJECT_NAME@
 Description: @PKG_DESC@
 Version: @FLANN_VERSION@
 Requires: @PKG_EXTERNAL_DEPS@
-Libs: -L${libdir} -lflann -lflann_cpp
+Libs: -L${libdir} @LZ4_STATIC_LDFLAGS@ -lflann -lflann_cpp
 Cflags: -I${includedir}
 
diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index e9fef04..2b2bb9d 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -3,6 +3,7 @@ add_custom_target(examples ALL)
 
 if (BUILD_C_BINDINGS)
     add_executable(flann_example_c flann_example.c)
+    target_link_libraries(flann_example_c -Wl,--push-state,--no-as-needed ${LZ4_LIBRARIES} -Wl,--pop-state)
     target_link_libraries(flann_example_c flann)
     set_target_properties(flann_example_c PROPERTIES COMPILE_FLAGS -std=c99)
 
@@ -14,6 +15,7 @@ if (HDF5_FOUND)
     include_directories(${HDF5_INCLUDE_DIRS})
 
     add_executable(flann_example_cpp flann_example.cpp)
+    target_link_libraries(flann_example_cpp -Wl,--push-state,--no-as-needed ${LZ4_LIBRARIES} -Wl,--pop-state)
     target_link_libraries(flann_example_cpp ${HDF5_LIBRARIES} flann_cpp)
     if (HDF5_IS_PARALLEL)
         target_link_libraries(flann_example_cpp ${MPI_LIBRARIES})
@@ -25,6 +27,7 @@ if (HDF5_FOUND)
 
     if (USE_MPI AND HDF5_IS_PARALLEL)
         add_executable(flann_example_mpi flann_example_mpi.cpp)
+        target_link_libraries(flann_example_mpi -Wl,--push-state,--no-as-needed ${LZ4_LIBRARIES} -Wl,--pop-state)
         target_link_libraries(flann_example_mpi flann_cpp ${HDF5_LIBRARIES} ${MPI_LIBRARIES} ${Boost_LIBRARIES})
 
         add_dependencies(examples flann_example_mpi)
diff --git a/src/cpp/CMakeLists.txt b/src/cpp/CMakeLists.txt
index b453b27..5c4f693 100644
--- a/src/cpp/CMakeLists.txt
+++ b/src/cpp/CMakeLists.txt
@@ -4,11 +4,12 @@ add_definitions(-D_FLANN_VERSION=${FLANN_VERSION})
 
 configure_file(${CMAKE_CURRENT_SOURCE_DIR}/flann/config.h.in ${CMAKE_CURRENT_SOURCE_DIR}/flann/config.h)
 
-file(GLOB_RECURSE C_SOURCES flann.cpp lz4.c lz4hc.c)
-file(GLOB_RECURSE CPP_SOURCES flann_cpp.cpp lz4.c lz4hc.c)
+file(GLOB_RECURSE C_SOURCES flann.cpp)
+file(GLOB_RECURSE CPP_SOURCES flann_cpp.cpp)
 file(GLOB_RECURSE CU_SOURCES *.cu)
 
 add_library(flann_cpp_s STATIC ${CPP_SOURCES})
+target_link_libraries(flann_cpp_s ${LZ4_LIBRARIES})
 if(CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_CLANG)
     set_target_properties(flann_cpp_s PROPERTIES COMPILE_FLAGS -fPIC)
 endif()
@@ -42,6 +43,7 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Linux" AND CMAKE_COMPILER_IS_GNUCC)
     endif()
 else()
     add_library(flann_cpp SHARED ${CPP_SOURCES})
+    target_link_libraries(flann_cpp -Wl,--push-state,--no-as-needed ${LZ4_LIBRARIES} -Wl,--pop-state)
     if (BUILD_CUDA_LIB)
 		cuda_add_library(flann_cuda SHARED ${CPP_SOURCES})
         set_property(TARGET flann_cpp PROPERTY COMPILE_DEFINITIONS FLANN_USE_CUDA)
@@ -77,6 +79,7 @@ endif()
 
 if (BUILD_C_BINDINGS)
     add_library(flann_s STATIC ${C_SOURCES})
+    target_link_libraries(flann_cpp -Wl,--push-state,--no-as-needed ${LZ4_LIBRARIES} -Wl,--pop-state)
     if(CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_CLANG)
         set_target_properties(flann_s PROPERTIES COMPILE_FLAGS -fPIC)
     endif()
@@ -88,6 +91,7 @@ if (BUILD_C_BINDINGS)
         target_link_libraries(flann -Wl,-whole-archive flann_s -Wl,-no-whole-archive)
     else()
         add_library(flann SHARED ${C_SOURCES})
+        target_link_libraries(flann_cpp -Wl,--push-state,--no-as-needed ${LZ4_LIBRARIES} -Wl,--pop-state)
 
         if(MINGW AND OPENMP_FOUND)
           target_link_libraries(flann gomp)
diff --git a/src/cpp/flann/util/serialization.h b/src/cpp/flann/util/serialization.h
index d731021..cdc2e5e 100644
--- a/src/cpp/flann/util/serialization.h
+++ b/src/cpp/flann/util/serialization.h
@@ -6,8 +6,8 @@
 #include <cstdlib>
 #include <cstring>
 #include <stdio.h>
-#include "flann/ext/lz4.h"
-#include "flann/ext/lz4hc.h"
+#include <lz4.h>
+#include <lz4hc.h>
 
 
 namespace flann