I have an issue very similar to How can I point C++ tests to my build-directory copy of my library and not to the installed library when LD_LIBRARY_PATH points to the installed one? but unrelated to LD_LIBRARY_PATH.

In my project, I first create a library using the standard cmake functions. Here is a simplified version:

    # Installation directories
    include(GNUInstallDirs)
    
    # Build library
    add_library(${PROJECT_NAME} SHARED
        ${SRC_FILES}
    )

    # Definitions
    target_compile_definitions(${PROJECT_NAME} PUBLIC ${DEFINITIONS})

    # Properties
    set_target_properties(${PROJECT_NAME} PROPERTIES
        CXX_STANDARD 20
    )

    # Compile options
    target_compile_options(${PROJECT_NAME} PRIVATE
        -Wall -Wextra -Wpedantic
    )

    # Include directories
    target_include_directories(${PROJECT_NAME} PUBLIC
        $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
        $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
    )

    # System include directories
    target_include_directories(${PROJECT_NAME} SYSTEM PUBLIC
        ${SYSTEM_INCLUDE_DIRS}
    )

    # Link libraries
    target_link_libraries(${PROJECT_NAME} PUBLIC
        ${SYSTEM_LIBRARIES}
    )

I then want to build some tests, which I do through a similar procedure, and link these tests to my library (this CMakeLists.txt is in a test subfolder):

    # Build tests
    add_executable(${PROJECT_NAME}_tests
        ${TEST_SRC_FILES}
    )

    # Definitions
    target_compile_definitions(${PROJECT_NAME}_tests PUBLIC ${TEST_DEFINITIONS})

    # Properties
    set_target_properties(${PROJECT_NAME}_tests PROPERTIES
        CXX_STANDARD 20
    )

    # Compile Options
    target_compile_options(${PROJECT_NAME}_tests PRIVATE
        -Wall -Wextra -Wpedantic
    )

    # Include Directories
    target_include_directories(${PROJECT_NAME}_tests PUBLIC
        $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
        $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/../include>
    )

    # System Include Directories
    target_include_directories(${PROJECT_NAME}_tests SYSTEM PUBLIC
        ${TEST_SYSTEM_INCLUDE_DIRS}
    )

    # Link Libraries
    target_link_libraries(${PROJECT_NAME}_tests PUBLIC
        ${PROJECT_NAME}
        ${TEST_SYSTEM_LIBRARIES}
    )

    # Enable ctest
    enable_testing()
    add_test(NAME ${PROJECT_NAME}_tests COMMAND ${PROJECT_NAME}_tests)

When I build, everything is great. The tests link to my library and life is good. If I examine the executable with ldd I see:

libmycoolproject.so => /home/username/src/mycoolproject/build/libmycoolproject.so (0x00007ffd2c8c3000)

And with readelf -d:

 0x0000000000000001 (NEEDED)             Shared library: [libconvert.so]
 ... (more libraries)
 0x000000000000001d (RUNPATH)            Library runpath: [/home/username/src/mycoolproject/build:/usr/local/lib:/home/username/src/mycoolproject/build/gtest/lib]

Note that one of the system libraries I depend on lives in /usr/local/lib.

However as soon as I install my library with sudo make install, ldd tells me:

libmycoolproject.so => /usr/local/lib/libmycoolproject.so (0x00007ffb480b3000)

The problem is then that if I make local changes, build, and run my tests, the tests link to the installed library rather than the one in my build folder.

How can I ensure that my tests link with the build directory version at runtime? What is going on here with the link order / RUNPATH?

Things I’ve tried without successful result:

• putting BUILD_RPATH ${CMAKE_BINARY_DIR} in set_target_properties
• appending to CMAKE_BUILD_RPATH
• changing the order of the libraries in target_link_libraries
• linking against ${CMAKE_BINARY_DIR}/lib${PROJECT_NAME}.so instead of ${PROJECT_NAME}