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### 3067. `recursive_directory_iterator::pop` must invalidate

Section: 31.12.12.2 [fs.rec.dir.itr.members] Status: C++20 Submitter: Casey Carter Opened: 2018-02-25 Last modified: 2021-02-25

Priority: 0

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Discussion:

`recursive_directory_iterator::pop` is effectively a "supercharged" `operator++`: it advances the iterator forward as many steps as are necessary to reach the next entry in the parent directory. Just as is the case for `operator++`, `pop` must be allowed to invalidate iterator copies to allow efficient implementation. The most efficient fix seems to be borrowing the invalidation wording from 25.3.5.3 [input.iterators] Table 87's specification for the required `++r` expression for input iterators.

[ 2018-03-06 Moved to Tentatively Ready after 5 positive votes on c++std-lib. ]

[2018-06 Rapperswil: Adopted]

Proposed resolution:

This wording is relative to N4727.

1. Change 31.12.12.2 [fs.rec.dir.itr.members] as indicated:

   >     void pop();
   >     void pop(error_code& ec);

   > > -26- Effects: If `depth() == 0`, set `*this` to `recursive_directory_iterator()`. Otherwise, cease iteration of the directory currently being iterated over, and continue iteration over the parent directory.

   > > -?- Postconditions: Any copies of the previous value of `*this` are no longer required either to be dereferenceable or to be in the domain of `==`.

   > > -27- Throws: As specified in 31.12.5 [fs.err.report].