dlvsym
void *dlvsym(void * __restrict, const char * __restrict,
__weak_alias(dlvsym,___dlvsym)
__strong_alias(__dlvsym,dlvsym)
dlvsym(void *handle, const char *name, const char *version)
sym = dlvsym(handle, "symbol_nonexistent", "V_3");
sym = dlvsym(handle, "testfunc", "");
sym = dlvsym(handle, "testfunc", NULL);
sym = dlvsym(handle, "testfunc", "V_1");
sym = dlvsym(handle, "testfunc", "V_3");