c++ - 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

From the documentation:

By default if you don't change any RPATH related settings, CMake will link the executables and shared libraries with full RPATH to all used libraries in the build tree.

This is the behaviour you are seeing.

However, there are a number of ways to change this to match the behaviour you require.

Some examples from the above linked docs:

# use, i.e. don't skip the full RPATH for the build tree
SET(CMAKE_SKIP_BUILD_RPATH  FALSE)

# when building, don't use the install RPATH already
# (but later on when installing)
SET(CMAKE_BUILD_WITH_INSTALL_RPATH FALSE) 

# the RPATH to be used when installing
SET(CMAKE_INSTALL_RPATH "")

# don't add the automatically determined parts of the RPATH
# which point to directories outside the build tree to the install RPATH
SET(CMAKE_INSTALL_RPATH_USE_LINK_PATH FALSE)

Using the above you'll likely want to set CMAKE_INSTALL_RPATH and then distribute the installed binary.

If you want to distribute from the binary in your build tree, it is also possible to bypass CMake's rpath handling and modify the rpath directly using linker flags:

set_target_properties(game PROPERTIES LINK_FLAGS "-Wl,-rpath,./")