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[libc++][nfc] Move iterator_traits and related into __iterator/iterator_traits.h.

Authored by zoecarver on Apr 16 2021, 2:21 PM.



Based on D100682 and D99855.

(Note: I originally was going to just make this part of D99855, but I decided not to because this patch moves lots of unrelated code around, and I didn't want to make D99855 harder to review because of unrelated code-changes/moves.)

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zoecarver created this revision.Apr 16 2021, 2:21 PM
zoecarver requested review of this revision.Apr 16 2021, 2:21 PM
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I like these cleanups!


Are we expecting <concepts> to include <type_traits>?


The new header includes <concepts>. What's our policy for including this header here too? I would prefer to remove it.


Yes. Everything includes <type_traits>; that's kind of an invariant of libc++.
However, if this file needs something out of <type_traits>, it's good practice to Include What You Use, preferably with a comment. E.g.

#include <type_traits> // declval

Include What You Use. If this file uses something out of <concepts>, it should include <concepts>, preferably with a comment. However, in this case, the inclusion is actually mandated by the Standard! so we should probably comment to that effect.

#include <concepts> // mandated
cjdb accepted this revision.Apr 17 2021, 5:16 PM
Mordante accepted this revision as: Mordante.Apr 18 2021, 2:16 AM

LGTM assuming fixing the CI only requires include fixes.


Fair point, but I disagree with the comment part. Unless it's a real surprise I dislike these comments since they tend to get outdated quickly.
A good example is <array> it includes <cstdlib> to use _LIBCPP_UNREACHABLE. It seems that macro is in that specific header since it may result in abort() which is in <cstdlib>.

ldionne accepted this revision.Apr 19 2021, 7:27 AM

LGTM but:

  1. Sort includes
  2. Make sure you include-what-you-use

Agreed with @Mordante, only add a comment explaining why you add an #include when it's not obvious why the #include is needed, otherwise those comments become outdated too quickly to be useful.


Please sort those includes.

This revision is now accepted and ready to land.Apr 19 2021, 7:27 AM
zoecarver updated this revision to Diff 338647.Apr 19 2021, 2:43 PM
  • Fix includes.
  • Rebase off D99855.

Assuming the tests pass here as well, I'm going to land this with D99855.

This revision was landed with ongoing or failed builds.Apr 20 2021, 8:32 AM
This revision was automatically updated to reflect the committed changes.