You are incorrect; optimizations are possible in dynamic linking by making first references go through a slow path, which then patches some code thunk to make a direct call. This is limited only by the undesirability of making either the callling object or the called object a private, writable mapping. Because we want to keep both objects immutable, the call has to go into some privately mapped jump table. That table contains a thunk that can be rewritten to do a direct call to an absolute address. If we didn't care about sharing executables between address spaces we could patch the actual code in one object to jump directly to a resolved address in the other object. (mmap can do this: MAP_FILE plus MAP_PRIVATE: you map a file in a way that you can change the memory, but the changes appear only in your address space and not the file.)