Question

I’m running into a problem adding an element to a map linking strings to a custom class Node.
I saw no reason why the problem could have been caused by static initialization order, but wrapped the map in a function to test, and got the same results as before. I have the following code in three files:

In node.h:

class Node
{
    public:
        const std::string name;
        Node (){};
        Node (std::string name, double x, double y);
        Node (const Node& b);
};

std::map<std:: string, Node>& nodeMap();

In node.cpp:

map<string,Node>& nodeMap()
{
    static map<string,Node>* temp = new map<string, Node>();
    return *temp;
}
Node::Node (std::string name, double x, double y):name(name)
{
    nodeMap()[name]=*this;
}

And in main.cpp I initialize with:

itoa(i,i_str,10);
Node nI (i_str,rand(),rand());

The program compiles fine, but when it runs it crashes on nodeMap()[name]=*this, and the debugger returns

Program received signal SIGSEGV, Segmentation fault.
In ntdll!LdrWx86FormatVirtualImage () (C:\Windows\system32\ntdll.dll)

I’m sure I’m probably missing something obvious – I’m relatively new to c++ – but can’t figure out where my error is.

Answer 1

I’m not sure about it. But you have used the instance of Node before its constructor returns.

Node::Node (std::string name, double x, double y):name(name) // This is the constructor!
{ 
    nodeMap()[name]=*this; // You have tried to assign the current instance to map entry. NB: instance of Node is not finalized.
}

You should write constructor like

Node::Node (std::string name, double x, double y):name(name) // This is the constructor!
{ 
}

then in your main

Node nI(i_str, rand(), rand());
nodeMap()[nI.name]=nI;