One could argue the reinterpret_cast makes the intent more explicit which is a good thing. That said I don’t have much against the use of void* or even char* h

One could argue the reinterpret_cast makes the intent more explicit which is a good thing. That said I don’t have much against the use of void* or even char* here. If it works in C, it works in C++ just fine. std::span is not the right tool for this.