On Tue, May 9, 2017 at 10:39 AM, Boris Zbarsky <bzbar...@mit.edu> wrote: > On 5/9/17 9:17 AM, Nathan Froyd wrote: >> The argument I have always heard, Gecko-wise and elsewhere [1], is to >> prefer pointers for modification > > This is for primitive-typed out or inout params, right?
I don't remember hearing any distinction one way or the other. I don't think we have a rule written down for Gecko, but a lot of the things we have historically dealt with are heap-allocated anyway or have had to extensively deal with XPIDL, so passing around pointers has seemed natural. But many recent things (e.g. WebIDL, some of the editor refactorings, etc.) have started to prefer references even to heap-allocated things, so we now have to think a little harder. > In other words, we should prefer "int*" to "int&" for places where we expect > the callee to modify the int, just like we should prefer "MyClass**" to > "MyClass*&". I guess the same for POD structs if we expect people to be > writing to them wholesale via assignment operators? Not sure. I think a broader definition of "POD struct" would be required here: RefPtr<T> and similar are technically not POD, but I *think* you'd want to require RefPtr<T>* arguments when you expect the smart pointer to be assigned into? Not sure. > But for object-typed things like dom::Element or nsIFrame, it seems better > to me to pass references instead of pointers (i.e "Element&" vs "Element*") > for what are fundamentally in params, even though the callee may call > mutators on the passed-in object. That is, the internal state of the > element may change, but its identity will not. I get this argument: you want the non-nullability of references, but you don't want the verboseness (or whatever) of NonNull<T> or similar, so you're using T& as a better T*. I think I would feel a little better about this rule if we permitted it only for types that deleted assignment operators. Not sure if that's really practical to enforce. -Nathan _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
