How to link a shared library with CMake with relative path

Question

I want to link a third-party libLibrary.so and distribute it with my program. If user unzips my archive, he will get this folder structure:

game
  libLibrary.so
  game_executable

game_executable depends on ./libLibrary.so.

My project structure:

game
  bin
    libLibrary.so
  lib
    Library.h
  src
    game_executable.cpp
  CMakeLists.txt

My CMakeLists.txt:

cmake_minimum_required(VERSION 3.7)
project(game)

set(CMAKE_CXX_STANDARD 14)

set(CMAKE_BINARY_DIR ${CMAKE_SOURCE_DIR}/bin)
set(EXECUTABLE_OUTPUT_PATH ${CMAKE_BINARY_DIR})
set(LIBRARY_OUTPUT_PATH ${CMAKE_BINARY_DIR})

set(SOURCE_FILES src/game_executable.cpp)
include_directories(${CMAKE_SOURCE_DIR}/lib)
add_executable(game ${SOURCE_FILES})
target_link_libraries(${PROJECT_NAME} ${CMAKE_BINARY_DIR}/libLibrary.so)

However, what I get is my game_executable depends on the .../game/bin/libLibrary.so, not on the ./libLibrary.so that is in the folder with game_executable, making this totally unportable!

How can I make linking path relative instead of absolute?

Answer 1

Most of the time you want to set the RPATH to $ORIGIN instead of ., because it refers to the executable's path instead while . refers to the current directory at runtime (which can be anything else).

I find it simple to edit LINK_FLAGS instead of INSTALL_RPATH target property, because CMakes already has a variable named ORIGIN (see CMake's documentation).

So that boils down to the following:

# Find shared libraries next to the executable
set_target_properties(target_name PROPERTIES
        BUILD_WITH_INSTALL_RPATH FALSE
        LINK_FLAGS "-Wl,-rpath,$ORIGIN/")