Fix for "undefined reference to dlopen" in CMake projects

README.md

Suppose you get this error with the main.cpp file below:

 Linking CXX executable testlink
 CMakeFiles/testlink.dir/main.cpp.o: In function `main':
 main.cpp:(.text+0x1a): undefined reference to `dlopen'
 main.cpp:(.text+0x2a): undefined reference to `dlclose'
 collect2: ld returned 1 exit status
 make[2]: *** [testlink] Error 1
 make[1]: *** [CMakeFiles/testlink.dir/all] Error 2
 make: *** [all] Error 2

All you need to do is add ${CMAKE_DL_LIBS} to the target_link_libraries() call:

 target_link_libraries(testlink ${CMAKE_DL_LIBS})

CMakeLists.txt

project(testlink)

add_executable(testlink main.cpp)

target_link_libraries(testlink)

main.cpp

#include <dlfcn.h>

int main(int argc, char* argv[]) {
    void *handle = dlopen("/usr/lib/libmagic.so.1", 0);
    dlclose(handle);
    return 0;
}