GLFW - linker errors on UBuntu 14.04 LTS

Question

I want to compile an example code from this site (at the bottom). I downloaded GLFW 3.0.4 source code and I built it in a custom location. I used a default settings and GLFW was built as a static library. My CMakeLists.txt looks like this:

cmake_minimum_required(VERSION 2.8)
project(glfw_test_project)

SET(CMAKE_CXX_FLAGS "-Wall -Werror -g -std=c++11")

find_package(OpenGL REQUIRED)

include_directories(/home/user/MyLibs/OpenGL/glfw-3.0.4/include)
link_directories(/home/user/MyLibs/OpenGL/glfw-3.0.4/build/src)

add_executable(glfw_test main.cpp)

target_link_libraries(glfw_test ${OPENGL_gl_LIBRARY})
target_link_libraries(glfw_test glfw3)

When I run make I get following info:

Linking CXX executable glfw_test
/usr/bin/ld: /home/user/MyLibs/OpenGL/glfw-3.0.4/build/src/libglfw3.a(x11_clipboard.c.o): undefined reference to symbol 'XConvertSelection'
//usr/lib/x86_64-linux-gnu/libX11.so.6: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
make[2]: *** [glfw_test] Error 1
make[1]: *** [CMakeFiles/glfw_test.dir/all] Error 2
make: *** [all] Error 2

What is wrong ?

Edit1 When I build GLFW as a dynamic library everything works fine. Then the last line in my CMakeLists.txt have to be replaced with:

target_link_libraries(glfw_test glfw)

What is wrong when using a static library ?

Answer 1

I experienced the same problems on Ubuntu 14.04 LTS.

First: error adding symbols: DSO missing from command line shows a wrong order of linker command line parameters. This post made me realise that. You need to call $ make VERBOSE=1 to see the linker call and check it with your own eyes. Remember: TARGET_LINK_LIBRARIES() should be the last command in your CMakeLists.txt And have a look at this order explanation.

Second: if you build against static GLFW3 libraries all the X11 libraries are not automatically added to your linker call, as atsui already showed above. In the GLFW-Documentation you can find a cmake variable which should fit your needs: ${GLFW_STATIC_LIBRARIES}. To make use of it and enable a more automatic build process, let pkg-config find all dependencies for X11 libs:

CMAKE_MINIMUM_REQUIRED(VERSION 2.8)
PROJECT(myProject)

FIND_PACKAGE( PkgConfig REQUIRED )
pkg_search_module( GLFW3 REQUIRED glfw3 ) # sets GLFW3 as prefix for glfw vars

# now ${GLFW3_INCLUDE_DIR}, ${GLFW3_LIBRARIES} and ${GLFW3_STATIC_LIBRARIES} 
# are set

INCLUDE_DIRECTORIES( ${GLFW3_INCLUDE_DIR} )
ADD_EXECUTABLE( myProject mySource.cpp )

TARGET_LINK_LIBRARIES( myProject ${GLFW_STATIC_LIBRARIES} )
# they include X11 libs

Now check the linker lib parameters again with $ make VERBOSE=1 and you should find many more X11 libs like: -lXrandr -lXi -lXrender -ldrm -lXdamage -lXxf86vm -lXext -lX11 and -lpthread.

Third: when linking against the shared library, the dependencies to X11 etc. are resolved dynamically. That is why you don't need to explicitly add X11 lib flags to the linker. In that case you only need: TARGET_LINK_LIBRARIES( myProject ${GLFW_LIBRARIES} )

Fourth: it happened to me, that some glfwCommands had undefined reference to - linker errors. I found out, that I installed GLFW3 in /usr/local/lib but the linker was given only the LD_LIBRARY_PATH environment variable which was only set to /usr/lib32. Adding the parameter -L/usr/local/lib solved the reference problem. To avoid it in future I've set LD_LIBRARY_PATH=/usr/lib32;/usr/local/lib;.

Hint: to check what values are in your GLFW cmake variables, print them during build:

FOREACH(item ${GLFW3_STATIC_LIBRARIES})
    MESSAGE(STATUS "  using lib: " ${item})
ENDFOREACH()