Issue 661: New 27.6.1.2.2 changes make special extractions useless (original) (raw)

This page is a snapshot from the LWG issues list, see the Library Active Issues List for more information and the meaning of CD1 status.

661. New 27.6.1.2.2 changes make special extractions useless

Section: 31.7.5.3.2 [istream.formatted.arithmetic] Status: CD1 Submitter: Daniel Krügler Opened: 2007-04-01 Last modified: 2016-01-28

Priority: Not Prioritized

View all other issues in [istream.formatted.arithmetic].

View all issues with CD1 status.

Discussion:

To the more drastic changes of 31.7.5.3.2 [istream.formatted.arithmetic] in the current draft N2134 belong the explicit description of the extraction of the types short and int in terms of as-if code fragments.

1. The corresponding as-if extractions in paragraph 2 and 3 will never result in a change of the operator>> argument val, because the contents of the local variable lval is in no case written into val. Furtheron both fragments need a currently missing parentheses in the beginning of the if-statement to be valid C++.
2. I would like to ask whether the omission of a similar explicit extraction of unsigned short and unsigned int in terms of long - compared to their corresponding new insertions, as described in 31.7.6.3.2 [ostream.inserters.arithmetic], is a deliberate decision or an oversight.

Proposed resolution:

1. In 31.7.5.3.2 [istream.formatted.arithmetic]/2 change the current as-if code fragment

   typedef num_get<charT,istreambuf_iterator<charT,traits> > numget;
   iostate err = 0;
   long lval;
   use_facet(loc).get(*this, 0, *this, err, lval );
   if (err == 0) {
   && if (lval < numeric_limits::min() || numeric_limits::max() < lval))
   err = ios_base::failbit;

else
val = static_cast(lval);
}
setstate(err);
Similarily in 31.7.5.3.2 [istream.formatted.arithmetic]/3 change the current as-if fragment
typedef num_get<charT,istreambuf_iterator<charT,traits> > numget;
iostate err = 0;
long lval;
use_facet(loc).get(*this, 0, *this, err, lval );
if (err == 0) {
&& if (lval < numeric_limits::min() || numeric_limits::max() < lval))
err = ios_base::failbit;
else
val = static_cast(lval);
}
setstate(err); 2. ---

[ Kona (2007): Note to the editor: the name lval in the call to usefacetis incorrectly italicized in the code fragments corresponding tooperator>>(short &) and operator >>(int &). Also, val -- which appears twice on the line with the staticcast in the proposed resolution -- should be italicized. Also, in response to part two of the issue: this is deliberate. ]