4 ms·

This bothered me enough to check the source code, because I simply had to know: template <layout_or_array A> std::pair<ArrowArray, ArrowSchema> get_a

This bothered me enough to check the source code, because I simply had to know: template <layout_or_array A> std::pair<ArrowArray*, ArrowSchema*> get_arrow_structures(A& a) { arrow_proxy& proxy = detail::array_access::get_arrow_proxy(a); return std::make_pair(&(proxy.array()), &(proxy.schema())); } https://github.com/man-group/sparrow/blob/c01a768f590ebf3b229b22fe3d46585bf9648f5b/include/sparrow/array.hpp#L72 https://github.com/man-group/sparrow/blob/c01a768f590ebf3b22... So the answer is that the `std::move` does nothing and should be omitted, because this function only has one overload, and that overload takes its argument by lvalue-reference. (And as far as I can tell, `detail::array_access::get_arrow_proxy(a)` eventually just reads a member on `a`, so there's no copying anywhere) It's a harmless mistake; I'm just surprised it wasn't caught. The authors seem pretty experienced with the language.

quietbritishjim 2y ago
> So the answer is that the `std::move` does nothing and should be omitted You can't assign an rvalue into an lvalue reference, precisely to avoid this sort of mistake. If this is the only overload then this just wouldn't compile (e.g. [1]). So the std::move isn't doing nothing, but yes it should be omitted. Maybe it's just a weird typo. [1] https://ideone.com/4NS5dI https://ideone.com/4NS5dI
- tempodox 2y ago
  Indeed, I don't even have to compile it, vim (+ Syntastic) tells me as soon as it sees it: candidate function not viable: expects an lvalue for 1st argument
BoingBoomTschak 2y ago
Modern C++ in a nutshell t. C++17 dev and pain connoisseur