> >> On Dec 2, 2015, at 10:41 PM, Clark Cox <clarkc...@gmail.com> wrote: >> >>> Widget *w = factory.getCurrentWidget(); >>> Paint *p = w->getPaint(); >>> If the currentWidget is NULL, the second line does this. >> >> That counts as a pointer dereference (the special case of &*foo is just >> that, a special case). > > It syntactically looks like one, but it isnât one. âDereferenceâ > means referencing, i.e. accessing, the memory location pointed to. A > nonvirtual method call doesnât do that. > > The reason itâs undefined in the standard to dereference NULL is because > on almost all operating systems thatâs unmapped memory and will cause a > crash. It isnât just because of squeamishness about what the LHS of a -> > operator should be. > >> On Dec 2, 2015, at 10:22 PM, Marco S Hyman <m...@snafu.org> wrote: >> >> Isnât it a compiler implementation detail that w->getPaint under the >> covers turns into getPaint(w)? > > > In many languages Iâd agree with you. But C++ has a very explicit design > principle of not adding extra overhead unless you ask for it. If you want > the more powerful (but slower) behavior of virtual methods (inheritance, > etc.) you have to explicitly say âvirtualâ; otherwise a method call is > implemented just like a regular C function call. > > Jens
My understanding is that a method call on a pointer is a dereference due to this: "If E1 has the type pointer to class X, then the expression E1->E2 is converted to the equivalent form (*(E1)).E2" It would appear that the * operator is part of the spec's definition. Dou _______________________________________________ Do not post admin requests to the list. They will be ignored. Xcode-users mailing list (Xcode-users@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/xcode-users/archive%40mail-archive.com This email sent to arch...@mail-archive.com
