Assign ifstream object with old GCC - synthesized method std::basic_ifstream first required here

Question

I would like to save ifstream objects into a map to read them later. I am using old GCC version 4.4.7 (C++11 is not available) and do not manage to compile my code.

Here is my code example:

#include <iostream>
#include <fstream>
#include <map>

int main()
{
    std::map<std::string, std::ifstream> DicoRCALbin;
    DicoRCALbin["a"] = std::ifstream("M3-6I_10.rcal_0001.bin", std::ios_base::binary);
}

The error message:

$ g++ problem.cpp
In file included from /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ios:39,
                 from /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ostream:40,
                 from /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/iostream:40,
                 from test.cpp:1:
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/ios_base.h: In member function 'std::basic_ios<char, std::char_traits<char> >& std::basic_ios<char, std::char_traits<char> >::operator=(const std::basic_ios<char, std::char_traits<char> >&)':
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/ios_base.h:793: erreur: 'std::ios_base& std::ios_base::operator=(const std::ios_base&)' is private
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/iosfwd:47: erreur: à l'intérieur du contexte
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/iosfwd: In member function 'std::basic_istream<char, std::char_traits<char> >& std::basic_istream<char, std::char_traits<char> >::operator=(const std::basic_istream<char, std::char_traits<char> >&)':
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/iosfwd:53: note: synthesized method 'std::basic_ios<char, std::char_traits<char> >& std::basic_ios<char, std::char_traits<char> >::operator=(const std::basic_ios<char, std::char_traits<char> >&)' first required here 
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/iosfwd: In member function 'std::basic_ifstream<char, std::char_traits<char> >& std::basic_ifstream<char, std::char_traits<char> >::operator=(const std::basic_ifstream<char, std::char_traits<char> >&)':
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/iosfwd:81: note: synthesized method 'std::basic_istream<char, std::char_traits<char> >& std::basic_istream<char, std::char_traits<char> >::operator=(const std::basic_istream<char, std::char_traits<char> >&)' first required here 
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/streambuf: In member function 'std::basic_filebuf<char, std::char_traits<char> >& std::basic_filebuf<char, std::char_traits<char> >::operator=(const std::basic_filebuf<char, std::char_traits<char> >&)':
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/streambuf:778: erreur: 'std::basic_streambuf<_CharT, _Traits>& std::basic_streambuf<_CharT, _Traits>::operator=(const std::basic_streambuf<_CharT, _Traits>&) [with _CharT = char, _Traits = std::char_traits<char>]' is private
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/iosfwd:78: erreur: à l'intérieur du contexte
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/iosfwd: In member function 'std::basic_ifstream<char, std::char_traits<char> >& std::basic_ifstream<char, std::char_traits<char> >::operator=(const std::basic_ifstream<char, std::char_traits<char> >&)':
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/iosfwd:81: note: synthesized method 'std::basic_filebuf<char, std::char_traits<char> >& std::basic_filebuf<char, std::char_traits<char> >::operator=(const std::basic_filebuf<char, std::char_traits<char> >&)' first required here 
test.cpp: In function 'int main()':
test.cpp:8: note: synthesized method 'std::basic_ifstream<char, std::char_traits<char> >& std::basic_ifstream<char, std::char_traits<char> >::operator=(const std::basic_ifstream<char, std::char_traits<char> >&)' first required here 
[...]

Answer 1

Have you thought about boost::ref library?

#include <fstream>
#include <map>
#include <boost/ref.hpp>

int main()
{
    std::map<std::string, boost::reference_wrapper<std::ifstream> > DicoRCALbin;
    std::ifstream ifs("", std::ios_base::binary);
    DicoRCALbin.insert(std::make_pair("a", boost::ref(ifs)));
}

You'd have to forgo operator[] because ifstream isn't default constructible. Hope that helps.