关于类不生成默认构造函数的问题

项目中用到http server，选用了cpp-httplib，

我们创建类，以组合的形式对httplib::Server进行了封装：

class HttpServer {
public:
    /*
    HttpServer(const HttpServer& server){
        m_httplibServer = server.m_httplibServer;   // 错误：使用了被删除的函数‘httplib::Server& httplib::Server::operator=(const httplib::Server&)’
        m_serverHost = server.m_serverHost;
        m_port = m_serverHost.m_port;
    }
    */

    HttpServer(const std::string &host = "127.0.0.1", int32_t port  = 8080) :
      m_serverHost(host), m_port(port) { }

private:
    httplib::Server m_httplibServer;

    std::string m_serverHost;
    int32_t m_port;
};

HttpServer又作为上层Controller类的对象：

class Controller {
public:
    Controller();

    HttpServer &GetHttpServer() { return m_httpServer; }

private:
    HttpServer m_httpServer;
};

在main函数里对其调用：

HttpServer httpServer = m_controller.GetHttpServer();
httpServer.RegisterHttpInterfaces(intf1400.Get1400Interfaces());

一直报错：

错误：使用了被删除的函数‘HttpServer::HttpServer(const HttpServer&)’
  HttpServer httpServer = m_controller.GetHttpServer();

 

分析原因：从报错看，好像是HttpServer类没有拷贝构造函数，但是默认情况下应该自己生成的，随即把

HttpServer httpServer = m_controller.GetHttpServer();

里对引用返回值的接收类型改为引用：

HttpServer &httpServer = m_controller.GetHttpServer();

则可以编译通过，应该是因为引用接收不涉及拷贝构造函数的调用。

那么为什么编译器不为HttpServer类生成默认拷贝构造函数呢？不生成，那我自己写了一个试试：

class HttpServer {
public:
    HttpServer(const HttpServer& server){
        m_httplibServer = server.m_httplibServer; 
        m_serverHost = server.m_serverHost;
        m_port = m_serverHost.m_port;
    }

    HttpServer(const std::string &host = "127.0.0.1", int32_t port  = 8080) :
      m_serverHost(host), m_port(port) { }

private:
    httplib::Server m_httplibServer;

    std::string m_serverHost;
    int32_t m_port;
};

编译提示错误：

错误：使用了被删除的函数‘httplib::Server& httplib::Server::operator=(const httplib::Server&)’

 

猜想可能是cpp-httplib没有为httplib::Server实现‘=’操作符的重载，也没实现拷贝构造函数，先记录一下问题，后面有空再验证一下。