On 29 June 2010 00:19, Basile Starynkevitch wrote: > On Mon, 2010-06-28 at 16:08 -0700, Ian Lance Taylor wrote: >> Basile Starynkevitch <bas...@starynkevitch.net> writes: >> >> > * I don't know exactly what should be wished with respect to templates. >> > Tom Tromey (in CC) have a wonderful insight in >> > http://gcc.gnu.org/ml/gcc/2010-06/msg00143.html but I probably did not >> > understood all the details & the consequences. In particular I don't >> > understand if the mark method in his example has to be supplied or >> > generated. >> >> In Tom's interesting idea, we would write the mark function by hand for >> each C++ type that we use GTY with. >> >> One way to make this approach work for plugins would be to write >> >> template<typename T> >> void >> mark(T& t) >> { >> t->mark(); >> } >> >> Then every plugin which invents new garbage collected types would have >> to define a mark method for them. > > Isn't that precise statement a good use case for virtual methods?
No. Not at all. > In other words, for that trick to work for plugins, don't we require the > mark() method above to be virtual? No. The mark method just needs to do whatever is needed to mark the type. T& is not a reference to base. T doesn't need to derive from a single base class. A virtual function is completely unnecessary. The template function can be instantiated for any T, and will call a function T::mark, it doesn't need to be virtual for that to work. > I would be delighted with that, but I understood that many people don't > want to have virtual methods. There is no need to have virtual functions here.
