关于c++的一个报错

使用tstring构造函数，用到了VarBaseString的tostring,调用完,会导致局部对象指针为nullptr,目前在查原因

    class VarBaseString : public Var
    {
    public:
        VarBaseString(std::string str = "")
        {
            val = str;
            type = "string";
        }
        VarBaseString(const char* str)
        {
            val = str;
            type = "string";
        }
        ~VarBaseString()
        {
          
        }
        static std::string GetType()
        {
            return "string";
        }
        virtual std::string ToString() {
            return std::move(val);
        }
        VarBaseString operator =(const char* src)
        {
            val = src;
            return *this;
        }
        VarBaseString operator =(std::string src)
        {
            val = src;
            return *this;
        }
        std::string val;
    };

　　接下来是：

    Control* ctrl = CreateControl(ele->Value());
    /*if (strcmp(ele->Value(), "Widget") == 0)
    {
        Widget* wi = (Widget*)ctrl;
        wi->ParseXmlElement(ele);
    }*/
    ctrl->ParseXmlElement(ele);
   
    TiXmlAttribute* ta = ele->FirstAttribute();
    while (ta)
    {
        ctrl->SetAttribute(ta->Name(), ta->Value());
        /*    if (strcmp(ta->Name(), "pos") == 0)
            {
                int x, y;
                sscanf_s(ta->Value(), "%d,%d", &x, &y);
                ctrl->pos.x = x;
                ctrl->pos.y = y;
            }
            else if (strcmp(ta->Name(), "size") == 0)
            {
                int w, h;
                sscanf_s(ta->Value(), "%d,%d", &w, &h);
                ctrl->size.x = w;
                ctrl->size.y = h;
            }
            else if (strcmp(ta->Name(), "name") == 0)
            {
                sCtrlName = ta->Value();
            }*/
        /*else if (strcmp(ta->Name(), "bkcolor") == 0 || strcmp(ta->Name(), "bkclr") == 0)
            {
                sCtrlName = ta->Value();
                int w, h;
                ctrl->size.x = w;
                ctrl->size.y = h;
            }
            else if (strcmp(ta->Name(), "hovercolor") == 0 || strcmp(ta->Name(), "hoverclr") == 0)
            {
                UITheme::
            }*/

        ta = ta->Next();
    }
    TString sCtrlName(ctrl->name.val);
    if (ctrl)
    {
       childs.push_back(std::make_pair(TString(ctrl->name), ctrl));
        //childs.push_back(std::make_pair("sCtrlName", ctrl));
    }
    ele = ele->NextSiblingElement();
}