An error saying 'no matching function call'; even when I declared the function

This is a discussion on An error saying 'no matching function call'; even when I declared the function within the C++ Programming forums, part of the General Programming Boards category; Here is the code....at a very nascent stage. Code: class net_device { protected: bool send(net_device&,packet); std::deque<pack_dev_map> send_buffer; std::deque<pack_dev_map> recv_buffer; public: ...

  1. #1
    Registered User manasij7479's Avatar
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    Why is the call to the other constructor needed?

    Here is the code....at a very nascent stage.
    Code:
    class net_device
    {
        
        protected:
        bool send(net_device&,packet);
        std::deque<pack_dev_map> send_buffer;
        std::deque<pack_dev_map> recv_buffer;
        public:
        static bool connect(net_device,net_device);
    
    };
    //********/
    class packet
    {
        private:
        std::string main_data;
        //packet headers go here..
        public:
        std::string get_main_data();
        packet(std::string);
        //packet(packet&)
    };
    packet::packet(std::string data_arg)
    {
        main_data = data_arg;
    }
    
    
    std::string packet::get_main_data()
    {
        return main_data;
    }
    //*********/
    class pack_dev_map //packet-device sets...did not use std::map
    {
        public:
        packet p;
        net_device* n;
        pack_dev_map(packet&,net_device&);
    };
    
    pack_dev_map::pack_dev_map(packet& p_arg,net_device& n_arg)
    {
        p = p_arg;
        n = &n_arg;
    }
    The bold lines show an error that packet:: packet() is not defined. It is not, but why does it need it ?

    [also..to the moderators who may see this, I can't find a way to change the - now invalid- title of the post, can you do that?]
    Last edited by manasij7479; 07-08-2011 at 09:38 AM.

  2. #2
    'Allo, 'Allo, Allo
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    Because you aren't using initialization lists. From a quick google (the first question): C++ Q&A: Initializing C++ Class Members and Incorporating the Places Bar in your MFC Apps

  3. #3
    Registered User manasij7479's Avatar
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    The article says that the member objects must gave a way to be initialized; I'm sending references of objects of those types for that purpose.
    Shouldn't the default copy constructor and/0r the default assignment operator do the same job here ?

    In other words:: Why must I use

    pack_dev_map::pack_dev_map(packet& p_arg,net_device& n_arg):p(p_arg),n(&n_arg){}
    ?
    Last edited by manasij7479; 07-08-2011 at 10:20 AM.
    Manasij Mukherjee | gcc-4.8.2 @Arch Linux
    Slow and Steady wins the race... if and only if :
    1.None of the other participants are fast and steady.
    2.The fast and unsteady suddenly falls asleep while running !



  4. #4
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    Creating a non default constructor will remove the default constructor.
    It is too clear and so it is hard to see.
    A dunce once searched for fire with a lighted lantern.
    Had he known what fire was,
    He could have cooked his rice much sooner.

  5. #5
    Registered User manasij7479's Avatar
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    Why do I need the default constructor here?
    Isn't the default copy constructor/assignment operator enough for initializing ?

    I don't want to keep a default constructor because there wouldn't be any default objects in the program.
    Last edited by manasij7479; 07-08-2011 at 10:27 AM.
    Manasij Mukherjee | gcc-4.8.2 @Arch Linux
    Slow and Steady wins the race... if and only if :
    1.None of the other participants are fast and steady.
    2.The fast and unsteady suddenly falls asleep while running !



  6. #6
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    The string constructor is enough if you use and initializer list, yes. But If you don't then the packet needs to be default-constructed before the body of the constructor is called.
    It is too clear and so it is hard to see.
    A dunce once searched for fire with a lighted lantern.
    Had he known what fire was,
    He could have cooked his rice much sooner.

  7. #7
    Registered User manasij7479's Avatar
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    the packet needs to be default-constructed before the body of the constructor is called.
    Thank you..
    That was what I was having problems to come in terms with..!
    Anyway, is there a reason for that ?
    Manasij Mukherjee | gcc-4.8.2 @Arch Linux
    Slow and Steady wins the race... if and only if :
    1.None of the other participants are fast and steady.
    2.The fast and unsteady suddenly falls asleep while running !



  8. #8
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    In order to use a variable in the constructor, such as by assigning to it, it must be a valid object. That means it must already be constructed somehow. Lacking an initializer list, a no argument constructor is the only way.
    It is too clear and so it is hard to see.
    A dunce once searched for fire with a lighted lantern.
    Had he known what fire was,
    He could have cooked his rice much sooner.

  9. #9
    C++まいる!Cをこわせ! Elysia's Avatar
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    This might also be of some use to you: SourceForge.net: Do not remove parameter names - cpwiki
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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