"Marco Costalba" <mcostalba@xxxxxxxxx> writes: > On 9/23/07, David Kastrup <dak@xxxxxxx> wrote: >> "Marco Costalba" <mcostalba@xxxxxxxxx> writes: >> >> > And BTW >> > >> > template <typename T> >> > >> > is the thing in C++ that more remembers me of opaque pointers and >> > their use in C, the difference is that the first is fully type >> > checked. >> >> Not really. The difference is that the first generates new (and >> optimized) code for every type which is something you can only do >> using macros in C. Class programming is similar to opaque pointers >> (in particular concerning the generated code) but templates are really >> more like macros, as their instantiation generates specialized code, >> not at all like the handling of opaque pointers. > > Probably if I had written like this was more clear: > > template <typename T> int some_function(T* p); Huh? How is this supposed to support your point? There is nothing like an opaque pointer involved here. The point of opaque pointers is that they can stand for a variety of types, whereas each template instantiation can only substitute a single type. > And regarding 'new' code for each type I would like to remember that > template instantations of different types can be removed by > compiler/linker when the instantations are the same (i.e. produce > the same binary instuctions), this could happen for function > templates that handle pointers, as example. Hardly. The type constraints/virtual function tables of any called function depending on T will be different. And if indeed nothing depends on T at all inside of the template, it is pointless not to declare it as void *p in the first place: the type of *p will never be used then. -- David Kastrup, Kriemhildstr. 15, 44793 Bochum - To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
