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### 3056. `copy_file()` copies which attributes?

Section: 31.12.13.5 [fs.op.copy.file] Status: New Submitter: Davis Herring Opened: 2018-01-26 Last modified: 2020-09-06

Priority: 3

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Discussion:

(To resolve C++17 CD comment Late 25.) It is not stated which attributes are copied by `copy_file()`.

[2018-1-26 issues processing telecon]

Priority 3

Proposed resolution:

This wording is relative to N4713.

1. Modify 31.12.13.5 [fs.op.copy.file] as indicated:

   > Rationale:

   > The attributes specified are the useful subset of the attributes that can be queried in C++17. Existing practice is complicated: POSIX "cp -p" attempts to preserve user/group IDs, for instance, but cannot in general do so, and `setuid/setgid` permissions may be stripped.

   >     bool copy_file(const path& from, const path& to, copy_options options);
   >     bool copy_file(const path& from, const path& to, copy_options options,
   >                    error_code& ec) noexcept;

   > > […]

   > > 1. […]

   > > 2. (4.2) — Otherwise, copy the contents, permissions, and data modification time and attributes of the file `from` resolves to, to the file `to` resolves to, if:

   > > 3. […]

   > > 4. 1. (4.2.3) — `(options & copy_options::update_existing) != copy_options::none` and `from` is more recent than `to`, determined as if by use of the `last_write_time` function (31.12.13.26 [fs.op.last.write.time]).

   > >    Other implementation-defined attributes may be copied. Failure (or partial failure) to copy attributes is not an error.

   > > 5. […]

   > > […]