837. basic_ios::copyfmt() overly loosely specified

Section: 31.5.4.3 [basic.ios.members] Status: NAD Editorial Submitter: Martin Sebor Opened: 2008-05-17 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

The basic_ios::copyfmt() member function is specified in 31.5.4.3 [basic.ios.members] to have the following effects:

Effects: If (this == &rhs) does nothing. Otherwise assigns to the member objects of *this the corresponding member objects of rhs, except that

• rdstate() and rdbuf() are left unchanged;
• exceptions() is altered last by calling exceptions(rhs.except)
• the contents of arrays pointed at by pword and iword are copied not the pointers themselves

Since the rest of the text doesn't specify what the member objects of basic_ios are this seems a little too loose.

[ Batavia (2009-05): ]

We agree with the proposed resolution. Move to NAD Editorial.

Proposed resolution:

I propose to tighten things up by adding a Postcondition clause to the function like so:

Postconditions:

copyfmt() postconditions
Element	Value
rdbuf()	unchanged
tie()	rhs.tie()
rdstate()	unchanged
exceptions()	rhs.exceptions()
flags()	rhs.flags()
width()	rhs.width()
precision()	rhs.precision()
fill()	rhs.fill()
getloc()	rhs.getloc()

The format of the table follows Table 117 (as of N2588): basic_ios::init() effects.

The intent of the new table is not to impose any new requirements or change existing ones, just to be more explicit about what I believe is already there.