Programming :: Shared Libs - Multiple Files In C++?

I'm trying to change a group of cpp files to one shared lib. I have created a shared lib with a single file. I then did this with a group of files. The difference in what I'm doing is that before with the single file, .a, was added into a single .o file. Now I'm trying to add it to my main.cpp file which is NOT a .o file. I'm now getting these compiler errors from the main.cpp where is doesn't seem to recognize the semaphores.Example Error: undefined reference to `sem_wait'If I were not to use the share libs this compiles and runs as I expected it to.Something tells me this is a compiler flag issue, at least I hope it is