1. The same file handle is returned multiple times.
   • If the path provided to dlopen differs (even when the absolute path is the same), different file handles are returned.
2. A reference count is maintained by the dl library, so a dynamic library needs to be closed as many times using dlclose as it has been opened using dlopen.
   • The dynamic library is unloaded only when the reference count drops to 0 (+ no other loaded libraries use its symbol).
3. dlopen with RTLD_NOLOAD flag can be used to dlopen with RTLD_NOLOAD returns NULL if the target library is not resident on memory, or the handle of the library if it is resident. This can be used to:
   • avoid dlopen from opening the same library more than once
   • check whether the reference count has dropped to 0. E.g.:

     // NOTE: Below code has not been tested
     while ((void *handle = dlopen(TARGET_LIB_PATH, RTLD_NOLOAD)) != NULL)
     {
         dlclose(handle);
     }
     

References:

• https://stackoverflow.com/questions/12148454/will-dlopen-yield-the-same-handle-for-two-calls-with-the-same-file
• https://stackoverflow.com/questions/8033481/is-there-a-way-to-find-out-the-number-of-references-to-a-dynamic-library-in-a-pr