[Bug libstdc++/16154] New: input iterator concept too restrictive

["cludwig at cdc dot informatik dot tu-darmstadt dot de" <gcc-bugzilla at gcc dot gnu dot org>]

The input iterator concept checks performed if std::copy is called are too 
restrictive. Neither in section 24.1.1 nor in section 25.2 of the C++ standard 
I see any requirement that input iterators have to be default constructible. 
But the compilation of the following program fails anyway due to a failed 
DefaultConstructibleConcept check. 
 
cludwig@lap200:~/C++/gcc3.4/tmp> cat input-iterator.cc 
#include <iterator> 
#include <string> 
#include <iostream> 
#include <algorithm> 
 
class myInputIterator : public std::iterator<std::input_iterator_tag, char> { 
  std::string data; 
 
public: 
  // past-the-end iterators can be constructed 
  // by myInputIterator("") 
  explicit myInputIterator(std::string const& input) 
    : data(input) { 
  } 
 
  value_type operator*() { 
    return data.at(data.length() - 1); 
  } 
 
  myInputIterator& operator++() { 
    if(!data.empty()) { 
      data.resize(data.length() - 1); 
    } 
    return *this; 
  } 
 
  myInputIterator operator++(int) { 
    myInputIterator result(*this); 
    ++(*this); 
    return result; 
  } 
 
  friend bool operator==(myInputIterator const& lhs, 
                         myInputIterator const& rhs); 
}; 
 
 
bool operator==(myInputIterator const& lhs, myInputIterator const& rhs) { 
  return lhs.data == rhs.data; 
} 
 
 
bool operator!=(myInputIterator const& lhs, myInputIterator const& rhs) { 
  return !(lhs == rhs); 
} 
 
 
int main() { 
  std::copy(myInputIterator("Hello world!"), myInputIterator(""), 
            std::ostream_iterator<char>(std::cout)); 
  return 0; 
} 
 
 
I am going to attach the compiler output. 
 
Regards 
 
Christoph

-- 
           Summary: input iterator concept too restrictive
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: cludwig at cdc dot informatik dot tu-darmstadt dot de
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16154