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Section: 31.10.4.4[ifstream.members]Status:TC1Submitter: Nathan MyersOpened: 1998-08-06Last modified: 2016-01-28
Priority:Not Prioritized
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Discussion:
The description of basic_istream<>::open leaves unanswered questions about how itresponds to or changes flags in the error status for the stream. A strict readingindicates that it ignores the bits and does not change them, which confuses users who donot expect eofbit and failbit to remain set after a successful open. There are threereasonable resolutions: 1) status quo 2) fail if fail(), ignore eofbit 3) clear failbitand eofbit on call to open().
Proposed resolution:
In 31.10.4.4[ifstream.members] paragraph 3,and in 31.10.5.4[ofstream.members] paragraph 3, under open() effects, add a footnote:
A successful open does not change the error state.
Rationale:
This may seem surprising to some users, but it's just an instanceof a general rule: error flags are never cleared by theimplementation. The only way error flags are are ever cleared is ifthe user explicitly clears them by hand.
The LWG believed that preserving this general rule wasimportant enough so that an exception shouldn't be made just for thisone case. The resolution of this issue clarifies what the LWGbelieves to have been the original intent.