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Section: 15.4 [filesys.ts::fs.op.copy_file] Status: TS Submitter: CH-15 Opened: 2014-01-20 Last modified: 2017-07-30
Priority: Not Prioritized
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Even if to and from are different paths, they may be equivalent.
Specify what happens if (options & copy_options::overwrite_existing) but from and to resolve to the same file.
[2014-02-09, Beman Dawes: Need advice on this issue:]What do existing implentations do? Possible resolutions:
[2014-02-13 LWG/SG-3 Issaquah: LWG/SG-3 decided to treat equivalence in this case as an error. Beman to provide wording.]
[2014-04-09 Beman provided wording as requested. The Effects were rewritten to increase clarity. Behavior remains unchanged except for treating equivalence as an error.]
[17 Jun 2014 Rapperswil LWG moves to Immediate. Jonathan Wakely will provide editorial changes to improve the presentation of bitmask values.]
Proposed resolution:Change 15.4 [fs.op.copy_file]:
Precondition: At most one constant from each
copy_optionsoption group ([enum.copy_options]) is present in
!(options & (copy_options::skip_existing | copy_options::overwrite_existing | copy_options::update_existing))report a file already exists error as specified in Error reporting (7).
!exists(to) || (options & copy_options::overwrite_existing) || ((options & copy_options::update_existing) && last_write_time(from) > last_write_time(to)) || !(options & (copy_options::skip_existing | copy_options::overwrite_existing | copy_options::update_existing))copy the contents and attributes of the file
fromresolves to the file
fromfile was copied, otherwise
false. The signature with argument
falseif an error occurs.
Throws: As specified in Error reporting (7).
Complexity: At most one direct or indirect invocation of