Question

The problem is I use dlopen to load a library (the .so is written by me, it’s not a system library), but I got the error shown in the title.

1. I have included dlfcn.h
2. in compiler, I used the -ldl command
3. What I want to load is just the source code folder, I tried to add -L., but it did not work.

Answer 1

If the library you want to dlopen is not in the standard search path you have a number of options:

1. Specify the full path to the file in dlopen

   dlopen("/full/path/to/libfile.so");

2. Add the path to the library via LD_LIBRARY_PATH

   LD_LIBRARY_PATH=/path/to/library/ ./executable

3. use the ld -rpath option to add a library path to the application.

   g++ -link stuff- -Wl,-rpath=/path/to/library/

Note that options 1 & 3 hardcode the library path into your application. -rpath does have an option to specify a relative path, i.e.

-Wl,-rpath=$ORIGIN/../lib/

Will embed a relative path into the application.