Using the value of a static member variable in a constructor, initializing the value of the static member variable outside the class. If it is of type int, the value is initialized and accessible, but if it is of type std:: string or other non primitive types, the value does not exist. Why is this.
Here are my header files and CPP files：

namespace hiveGL
{
    namespace core
    {
        class CRenderEnvConfig : public hiveConfig::CHiveConfig
        {
        public:
            CRenderEnvConfig();
            ~CRenderEnvConfig() = default;

            std::pair<std::uint32_t, std::uint32_t> getWindowSize() const;

            void validate(const CRenderEnvConfig *vDefaultConfig);

            static const std::string ATTRIBUTE_WINDOW_WIDTH;
            static const std::string ATTRIBUTE_WINDOW_HEIGHT;
            static const std::string ATTRIBUTE_WINDOW_SYSTEM;
            static const std::string ATTRIBUTE_WINDOW_TILE;
            static const std::string ATTRIBUTE_GL_PROFILE;
            static const std::string ATTRIBUTE_GL_VERSION;
            static const std::string SUBCONFIG_RENDER_ENV;
            static const int myNumber;
            static const std::string myString;
            

        private:
            static const std::map<std::string, hiveConfig::EConfigDataType> m_Attributes;

            void __defineAttributesV() override;
            void __loadDefaultConfigV() override;

            template<typename T>
            void __validateAttribute(const std::string& vName, const std::function<bool(const T&)>& vValidator, const CRenderEnvConfig* vDefaultConfig);
        };
    }
}

const int  CRenderEnvConfig::myNumber = 20;
const std::string CRenderEnvConfig::myString = "hello";


CRenderEnvConfig::CRenderEnvConfig()
{
    std::cout << myNumber << "n";
    std::cout << myString << "n";
    __defineAttributesV();
}

below is result:

What is the reason why static member values cannot be used in constructors