closing stream before opening sets fail bit

[Benjamin Kosnik]

I've added a testcase based on this report, so the current behavior
will be at least codified. I think libstdc++-v3 has
standards-conforming behaivor.

I believe that close() in this case should set failbit. I don't think
that's really unclear -- the question really is if ifstream/ofstream
open resets state... 

I think the current libstdc++-v3 behavior is conformant. I agree that
this behavior is perhaps counter-intiutive and needs further
specification. The following defect report also touches on this issue:

-benjamin

-----

22.  Member open vs. flags

Section: 27.8.1.7 lib.ifstream.members 
Status: DR 
Submitter: Nathan
Myers Date: 6 Aug 98

The description of basic_istream<>::open leaves unanswered questions
about how it responds to or changes flags in the error status for the
stream. A strict reading indicates that it ignores the bits and does
not change them, which confuses users who do not expect eofbit and
failbit to remain set after a successful open. There are three
reasonable resolutions: 1) status quo 2) fail if fail(), ignore eofbit
3) clear failbit and eofbit on call to open().

Proposed Resolution:

In 27.8.1.7 [lib.ifstream.members] paragraph 3, _and_ in 27.8.1.10
[lib.ofstream.members] paragraph 3, under open() effects, add a
footnote:

     A successful open does not change the error state.