Undefined reference to LZ4_decompress_fast, LZ4_compressHC

[translunar]

I'm building on a Linux machine and getting the following errors:

[ 80%] Built target pcl_add_gaussian_noise
Linking CXX executable ../bin/pcl_boundary_estimation
../lib/libpcl_kdtree.so.1.7.2: undefined reference to `LZ4_decompress_fast'
../lib/libpcl_kdtree.so.1.7.2: undefined reference to `LZ4_compressHC'
collect2: ld returned 1 exit status
make[2]: *** [bin/pcl_boundary_estimation] Error 1
make[1]: *** [tools/CMakeFiles/pcl_boundary_estimation.dir/all] Error 2
make: *** [all] Error 2

I don't see anywhere in the CMakeCache.txt to set the LZ4 directory. I also don't see what in FLANN, but I assume this is a problem with PCL based on where the error is showing up.

[translunar]

I have not found a fix, but a workaround is to add the path to liblz4.so manually to the kdtree/CMakeFiles/pcl_kdtree.dir/link.txt file after generating my cmake build directory. This has to be repeated anytime you re-generate your cmake configuration.

[taketwo]

I wonder what is so special about your setup that you get this error. Never had it.

[VictorLamoine]

I never encountered this bug; I have no idea what can be the cause, sorry!

[translunar]

@taketwo It's a really old RedHat machine, I think.

[jspricke]

git grep -i lz4 shows only unrelated output, so I guess it's an Red Head issue. Try a newer version, maybe.

[jb4652]

At first, I met the same problem as you. But after I link flann_s.lib or flann_cpp_s.lib to PCL, no error any more. However, flann.lib and flann_cuda_s.lib still don't work.

Could anybody give an explanation?

[jspricke]

Flann includes lz4 in it's current git, but not in an official release. Which version did you use @jb4652 @MohawkJohn?

[translunar]

I was using whatever version was HEAD on git when I posted this issue.

[jb4652]

Me too, I use the most up to date master repository code, not the individual package.

[sleepyspider1]

I have this problem on windows VS2013 when building pcl_kdtree project. I needed to use the shared lib version of flann, I could not use static.

I rolled back to 1.7.1 of flann and it seemed to work. Using version 1.8.1 does not work. I had to fix a couple of things though.

1. When building debug version of flann and flann_cpp, I had to add \bigobj to the linker flags.
2. I had to add a dummy export function to the flann_cpp.cpp file so vs2013 will force output of the flann_cpp.lib import lib. If there aren't any exports, it won't create an import lib.

[kheaactua]

I still get this error with PCL>1.8.1 and FLANN 1.9.1 (four years later.) I've found that including the flann_s fixes this issue. The reason I fell upon that is that the lz4 symbols seem to only be included in that library when looking through the build scripts

I was wondering if anyone had a good solution to this? For me, I'm considering one of the following:

1. Adding flann_s to PCL's FindFLANN.cmake FLANN_LIBRARIES variable
2. Added flann_s to FLANN's exported pkg-config file (which would then inject it into FLANN_LIBRARIES)

[jspricke]

@kheaactua flann should not provide the LZ4 symbols, to begin with (see #2563 and links in there). Can you some more data? What do you compile? Which OS? Which version of PCL exactly? Which build system..

[kheaactua]

Hi @jspricke, I get this issue whenever I try to upgrade from flann 1.8.4 to flann 1.9.1. Even with PCL 1.7.2 I had to include the flann_s lib in my downstream project in order to get everything linking (though this didn't work for PCL 1.9.1)

I'm attempting to build PCL 1.9.1 (72f41b6, temporarily with a patch described in #2735) on Windows with MSVC 2013 using CMake, with:

• Boost 1.60
• Eigen 3.2.9
• FLANN 1.9.1
• QHULL 2015.2
• VTK 6.1
• Qt 5.3.2
• GTest 1.8.1

Also, looking at my build script, I set:

• CMAKE_CXX_STANDARD=True
• BUILD_surface_on_nurbs:BOOL=True
• PCL_BUILD_WITH_BOOST_DYNAMIC_LINKING_WIN32:BOOL=On
• BUILD_SHARED_LIBS:BOOL=True

I run this all in a Conan build script. FLANN is discovered with pkg-config (CMake output)

-- Checking for module 'flann>=1.7.0'
--   Found flann, version 1.9.1
-- FLANN found (include: C:/.conan/pdtd6xb8/1/include, lib: C:/.conan/31h03hz4/1/lib/flann_cpp_s.lib;C:/.conan/31h03hz4/1/lib/flann_s.lib)

(the flann_s.lib is there due to my attempt to get the lz4 symbols, with out a temporary patch that wouldn't be there. Also, this used to start with flann.lib, I'll comment out this patch, re-run, and get the true output)

My FLANN pkg-config file:

prefix=C:/Users/jenkins/.conan/data/flann/1.9.1/ntc/stable/package/3cf689755b8c112c8280af554277602991f652d9
exec_prefix=${prefix}
libdir=${prefix}/lib
includedir=${prefix}/include

Name: flann
Description: Fast Library for Approximate Nearest Neighbors
Version: 1.9.1
Requires:
Libs: -L${libdir} -lflann -lflann_cpp
Cflags: -I${includedir}

The specific errors are:

   "C:\.conan\wjtk1xca\1\ALL_BUILD.vcxproj" (default target) (1) ->
   "C:\.conan\wjtk1xca\1\tools\pcl_compute_cloud_error.vcxproj" (default target) (4) ->
   "C:\.conan\wjtk1xca\1\kdtree\pcl_kdtree.vcxproj" (default target) (10) ->
   (Link target) ->
      kdtree_flann.obj : error LNK2001: unresolved external symbol LZ4_decompress_safe_continue [C:\.conan\wjtk1xca\1\kdtree\pcl_kdtree.vcxproj]
      kdtree_flann.obj : error LNK2001: unresolved external symbol LZ4_decompress_safe [C:\.conan\wjtk1xca\1\kdtree\pcl_kdtree.vcxproj]
      kdtree_flann.obj : error LNK2001: unresolved external symbol LZ4_resetStreamHC [C:\.conan\wjtk1xca\1\kdtree\pcl_kdtree.vcxproj]
      kdtree_flann.obj : error LNK2001: unresolved external symbol LZ4_compress_HC_continue [C:\.conan\wjtk1xca\1\kdtree\pcl_kdtree.vcxproj]
      kdtree_flann.obj : error LNK2001: unresolved external symbol LZ4_setStreamDecode [C:\.conan\wjtk1xca\1\kdtree\pcl_kdtree.vcxproj]
      C:\.conan\wjtk1xca\1\bin\pcl_kdtree_release.dll : fatal error LNK1120: 5 unresolved externals [C:\.conan\wjtk1xca\1\kdtree\pcl_kdtree.vcxproj]

(more detail)

CMake Definitions:
 - CONAN_LINK_RUNTIME=/MD
 - CONAN_EXPORTED=1
 - CONAN_IN_LOCAL_CACHE=ON
 - CONAN_COMPILER=Visual Studio
 - CONAN_COMPILER_VERSION=12
 - BUILD_SHARED_LIBS=ON
 - CMAKE_INSTALL_PREFIX=C:\.conan\8qa8x8pu\1
 - CMAKE_INSTALL_BINDIR=bin
 - CMAKE_INSTALL_SBINDIR=bin
 - CMAKE_INSTALL_LIBEXECDIR=bin
 - CMAKE_INSTALL_LIBDIR=lib
 - CMAKE_INSTALL_INCLUDEDIR=include
 - CMAKE_INSTALL_OLDINCLUDEDIR=include
 - CMAKE_INSTALL_DATAROOTDIR=share
 - CONAN_CXX_FLAGS=/MP4
 - CONAN_C_FLAGS=/MP4
 - CMAKE_EXPORT_NO_PACKAGE_REGISTRY=ON
 - BOOST_ROOT:PATH=C:/.conan/vd915kie/1
 - CMAKE_CXX_STANDARD=11
 - QHULL_ROOT:PATH=C:/.conan/xyw33ogj/1
 - GTEST_ROOT:PATH=C:/.conan/lxanndul/1
 - VTK_DIR:PATH=C:/.conan/paduzfj8/1/lib/cmake/vtk-6.1
 - WITH_OPENNI:BOOL=False
 - WITH_OPENNI2:BOOL=False
 - BUILD_surface_on_nurbs:BOOL=ON
 - BUILD_SHARED_LIBS:BOOL=ON
 - PCL_BUILD_WITH_BOOST_DYNAMIC_LINKING_WIN32:BOOL=ON
 - Qt5Core_DIR:PATH=C:/.conan/be94tom9/1/lib/cmake/Qt5Core
 - Qt5Gui_DIR:PATH=C:/.conan/be94tom9/1/lib/cmake/Qt5Gui
 - Qt5OpenGL_DIR:PATH=C:/.conan/be94tom9/1/lib/cmake/Qt5OpenGL
 - Qt5Widgets_DIR:PATH=C:/.conan/be94tom9/1/lib/cmake/Qt5Widgets
 - Qt5_DIR:PATH=C:/.conan/be94tom9/1/lib/cmake/Qt5
 - QT_QMAKE_EXECUTABLE:PATH=C:/.conan/be94tom9/1/bin/qmake
 - EIGEN_INCLUDE_DIR:PATH=C:/.conan/3b7kqput/1/include/eigen3