Here is the simplified version of the class which is stored as value in a map which works fine in VS2008:
class Value{
friend class FriendClass;
friend class std::map<std::string, Value>;
friend struct std::pair<const std::string, Value>;
friend struct std::pair<std::string, Value>;
Value() {..}
Value(Value const& other) {..}
... rest members...
};
Code (called from FriendClass, so this can reach constructors) :
std::map<const std::string, Value> map;
map.insert(std::make_pair("x", Value()));
This compiles w/o any error in VS2008, but fails on VS2015/C++11:
file.cpp(178): error C2664: 'std::_Tree_iterator>>> std::_Tree>::insert(std::_Tree_const_iterator>>>,const std::pair &)': cannot convert argument 1 from 'std::pair' to 'std::pair &&' with [ _Kty=std::string, _Ty=Value, _Pr=std::less, _Alloc=std::allocator> ] and [ _Kty=std::string, _Ty=Value ] file.cpp(178): note: Reason: cannot convert from 'std::pair' to 'std::pair' with [ _Kty=std::string, _Ty=Value ] file.cpp(178): note: No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
If I make the Value copy constructor public, it compiles fine in VS2015 as well.
But that was private with purpose, and only made available for std::map and std::pair. However, it seems in C++11 additional friend access are also necessary to declare. Which are these?
Thank you.
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