reinterpret_cast gives exactly the same error (not warning).
curlpp::Multi is a struct and handle_ is a pointer, thus it'sperferctly understandable that gcc would refused to cast the former to a pointer. What I do is to cast the pointer to a curlpp::Multi to a pointer to a pointer, since what interests me is the first member thereof, which is a pointer.

From a memory access point of view, this is good. From a language perspective, it is a blatant hack.