Question

I am having a bit of trouble deep copying a pointer to a map of pointer values.

std::map<string, TH1D*>* m_hist_split;

My current method:

I am using a class template that copies the map pair and initializes the value of the pair on the heap. the template then returns a map::type_value

#ifndef DEEPCOPY_H
#define DEEPCOPY_H

#include <map>
#include <algorithm>

namespace DeepCopy{

  template<class A, class B>
    struct MapPointerValue{
      typedef typename std::map< A, B* >::value_type map_t;
      map_t operator() (map_t p){
        return std::make_pair(p.first, new B(*p.second) );
      }
    };

...
...

}
#endif

Inside my copy constructor I then attempt to deep copy my pointer to a map of pointer values.

Cutflow::Cutflow(const Cutflow& cpy){

m_hist_split = new map<string, TH1D*>;
transform(cpy.m_hist_split->begin(),cpy.m_hist_split->end(), inserter(m_hist_split, m_hist_split->begin()), DeepCopy::MapPointerValue<string, TH1D>() );

...
...

}

When compiling I then get an ugly error 🙁 :

Compiling src/Cutflow.cxx to obj/Cutflow.o
x86_64-slc5-gcc34-opt/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.2/../../../../include/c++/4.3.2/bits/stl_iterator.h: In instantiation of 'std::insert_iterator<std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*> > >*>':
src/Cutflow.cxx:42:   instantiated from here
x86_64-slc5-gcc34-opt/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.2/../../../../include/c++/4.3.2/bits/stl_iterator.h:562: error: 'std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*> > >*' is not a class, struct, or union type
x86_64-slc5-gcc34-opt/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.2/../../../../include/c++/4.3.2/bits/stl_iterator.h:572: error: 'std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*> > >*' is not a class, struct, or union type
x86_64-slc5-gcc34-opt/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.2/../../../../include/c++/4.3.2/bits/stl_iterator.h:599: error: 'std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*> > >*' is not a class, struct, or union type
x86_64-slc5-gcc34-opt/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.2/../../../../include/c++/4.3.2/bits/stl_iterator.h:608: error: 'std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*> > >*' is not a class, struct, or union type
x86_64-slc5-gcc34-opt/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.2/../../../../include/c++/4.3.2/bits/stl_iterator.h: In function 'std::insert_iterator<_Container> std::inserter(_Container&, _Iterator) [with _Container = std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*> > >*, _Iterator = std::_Rb_tree_iterator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*> >]':
src/Cutflow.cxx:42:   instantiated from here
x86_64-slc5-gcc34-opt/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.2/../../../../include/c++/4.3.2/bits/stl_iterator.h:648: error: 'std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*> > >*' is not a class, struct, or union type
x86_64-slc5-gcc34-opt/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.2/../../../../include/c++/4.3.2/bits/stl_algo.h: In function '_OIter std::transform(_IIter, _IIter, _OIter, _UnaryOperation) [with _IIter = std::_Rb_tree_iterator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*> >, _OIter = std::insert_iterator<std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*> > >*>, _UnaryOperation = DeepCopy::MapPointerValue<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D>]':
src/Cutflow.cxx:42:   instantiated from here
x86_64-slc5-gcc34-opt/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.2/../../../../include/c++/4.3.2/bits/stl_algo.h:4281: error: no match for 'operator=' in '__result.std::insert_iterator<_Container>::operator* [with _Container = std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*> > >*]() = DeepCopy::MapPointerValue<A, B>::operator()(typename std::map<A, B*, std::less<_Key>, std::allocator<std::pair<const A, B*> > >::value_type) [with A = std::basic_string<char, std::char_traits<char>, std::allocator<char> >, B = TH1D](std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*>(((const std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*>&)((const std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*>*)__first.std::_Rb_tree_iterator<_Tp>::operator* [with _Tp = std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*>]()))))'
x86_64-slc5-gcc34-opt/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.3.2/../../../../include/c++/4.3.2/bits/stl_iterator.h:559: note: candidates are: std::insert_iterator<std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*> > >*>& std::insert_iterator<std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*> > >*>::operator=(const std::insert_iterator<std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, TH1D*> > >*>&)

Any ideas what I am doing wrong.

Also,

is what I am doing correct?

😀

Answer 1

In the following line

transform(cpy.m_hist_split->begin(),cpy.m_hist_split->end(), inserter(m_hist_split, m_hist_split->begin()), DeepCopy::MapPointerValue<string, TH1D>() );

you have mistakenly called the inserter function with a pointer to a map as the first parameter instead of a reference.

For completeness, inserter is defined in §24.5.2.6.5 like this:

template <class Container>
  insert_iterator<Container> inserter(Container& x, typename Container::iterator i);

Returns: insert_iterator(x, i)

In this case, a simple typo caused a big headache.