Issue 118: basic_istream uses nonexistent num_get member functions (original) (raw)

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118. basic_istream uses nonexistent num_get member functions

Section: 31.7.5.3.2 [istream.formatted.arithmetic] Status: CD1 Submitter: Matt Austern Opened: 1998-11-20 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

Formatted input is defined for the types short, unsigned short, int,unsigned int, long, unsigned long, float, double,long double, bool, and void*. According to section 27.6.1.2.2, formatted input of a value x is done as if by the following code fragment:

typedef num_get< charT,istreambuf_iterator<charT,traits> > numget; iostate err = 0; use_facet< numget >(loc).get(*this, 0, *this, err, val); setstate(err);

According to section 28.3.4.3.2.2 [facet.num.get.members], however,num_get<>::get() is only overloaded for the typesbool, long, unsigned short, unsigned int, unsigned long, unsigned long,float, double, long double, andvoid*. Comparing the lists from the two sections, we find that 27.6.1.2.2 is using a nonexistent function for typesshort and int.

Proposed resolution:

In 31.7.5.3.2 [istream.formatted.arithmetic] Arithmetic Extractors, remove the two lines (1st and 3rd) which read:

operator>>(short& val); ... operator>>(int& val);

And add the following at the end of that section (27.6.1.2.2) :

operator>>(short& val);

The conversion occurs as if performed by the following code fragment (using the same notation as for the preceding code fragment):

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

operator>>(int& val);

The conversion occurs as if performed by the following code fragment (using the same notation as for the preceding code fragment):

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

[Post-Tokyo: PJP provided the above wording.]