Function erlang_nif_sys::erlang_nif_sys_api::enif_dlsym

pub unsafe extern "C" fn enif_dlsym(
    handle: *mut c_void, 
    symbol: *const c_uchar, 
    err_handler: Option<unsafe extern "C" fn(_: *mut c_void, _: *const c_uchar)>, 
    err_arg: *mut c_void
) -> *mut c_void

See enif_dlsym in the Erlang docs.