Linking with CMakeLists: ld cannot find library

Question

I have a CMakeLists.txt file, with the following:

target_link_libraries(${PROJECT_NAME} OpenNI2)

When I run cmake

Answer 1

it works if adding like:

target_link_libraries(${PROJECT_NAME} /path_to_library_build/libOpenNI2.a)

details:

ld is looking for the libraries in a very short list of folders defined in

/etc/ld.so.conf

and it usually looks like following:

include /etc/ld.so.conf.d/*.conf

and actual paths list from those *.conf files usually is like:

# Legacy biarch compatibility support
/lib32
/usr/lib32
# Multiarch support
/usr/local/lib/x86_64-linux-gnu
/lib/x86_64-linux-gnu
/usr/lib/x86_64-linux-gnu

if your project linking library is not in the folder of this list, ld won't find it unless either a special linking variable set LD_LIBRARY_PATH with the path to your library or a complete path/library name provided in cmake target_link_libraries directive.

details on how to proper setup LD_LIBRARY_PATH variable discussed here

Answer 2

That's because when linking, the linker doesn't look in the current directory but only in a set of predefined directories.

You need to tell CMake where the library is, for example by giving the full path to the library in the target_link_library command, or adding it as an imported library.