[libcxx-commits] [PATCH] D129040: [libc++] Fix unwrapping ranges with different iterators and sentinels

[Nikolas Klauser via Phabricator via libcxx-commits]

philnik added inline comments.


================
Comment at: libcxx/include/__algorithm/unwrap_range.h:39
+  _LIBCPP_HIDE_FROM_ABI static constexpr auto __unwrap(_Iter __first, _Sent __last) {
+    return pair{pair{std::move(__first), nullptr}, std::move(__last)};
+  }
----------------
huixie90 wrote:
> I'd be really cautious about `nullptr`, which is comparable with pointers. if any of the logic goes wrong, it could result in a runtime UB. Is it possible to avoid `nullptr`?
How exactly would anything go wrong at runtime? This results in `pair<pair<_Iter, nullptr_t>, _Sent>`. The `nullptr_t` should only ever be passed back to `__rewrap_iter`. If that weren't the case there would be type mismatches all over the place. (i.e. `__rewrap_iter` would just return the unwrapped pointer) But anyways, just to make it //really// hard to break I'll change it to a tag type, since there isn't any downside to do so.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D129040/new/

https://reviews.llvm.org/D129040