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Undefined reference to 'vtable for ...'

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Undefined reference to 'vtable for ...'

Mar 17th, 2008

I'm self studying from the book, C++ Primer Plus Fifth Edition, by Stephen Prata. The following relates to Chapter 13, Page 699, Programming Exercise #4. One task is to write the derived class method definitions based upon the given prototypes. The following are the said prototypes.

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class Port
{
    private:
        char *brand;
        char style[20];     // i.e. tawny, ruby, vintage
        int bottles;
    public:
        Port(const char *br = "none", const char *st = "none", int b = 0);
        Port(const Port &p);            // copy constructor
        virtual ~Port() { delete [] brand;}
        Port & operator=(const Port &p);
        Port & operator+=(int b);
        Port & operator-=(int b);
        int BottleCount() const {return bottles;}
        virtual void Show() const;
        friend ostream &operator<<(ostream &os, const Port &p);
};
 
class VintagePort : public Port
{
    private:
        char * nickname;            // i.e. The Noble, or Old Velvet, etc.
        int year;                   // vintage year
    public:
        VintagePort();
        VintagePort(const char *br, int b, const char *nn, int y);
        VintagePort(const VintagePort &vp);
        ~VintagePort() {delete [] nickname;}
        void Show() const;
        friend ostream & operator<<(ostream &os, const VintagePort & vp);
};
class Port
{
    private:
        char *brand;
        char style[20];     // i.e. tawny, ruby, vintage
        int bottles;
    public:
        Port(const char *br = "none", const char *st = "none", int b = 0);
        Port(const Port &p);            // copy constructor
        virtual ~Port() { delete [] brand;}
        Port & operator=(const Port &p);
        Port & operator+=(int b);
        Port & operator-=(int b);
        int BottleCount() const {return bottles;}
        virtual void Show() const;
        friend ostream &operator<<(ostream &os, const Port &p);
};

class VintagePort : public Port
{
    private:
        char * nickname;            // i.e. The Noble, or Old Velvet, etc.
        int year;                   // vintage year
    public:
        VintagePort();
        VintagePort(const char *br, int b, const char *nn, int y);
        VintagePort(const VintagePort &vp);
        ~VintagePort() {delete [] nickname;}
        void Show() const;
        friend ostream & operator<<(ostream &os, const VintagePort & vp);
};

You will note that the base class destructor is virtual. That the derived class destructor is implemented inline.

I was creating the derived class method definitions in a cpp file and couldn't get the project to progressively compile correctly. At my first method definition, a default constructor, the compiler kept spitting out this error message:

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Chapter-13\pe-13-04\port.cpp|74|undefined reference to `vtable for VintagePort'

The line number was pointing to my derived class constructor definition. I did some googling around and came across this workaround. I removed the inline effect of the derived class destructor, made that into a method definition in the cpp file and presto, compilation succeeded.

Am I to assume that the example in the book, as regards the inline feature of a derived class destructor, is in error. Are there any other explanations.

Steve
Prime 357 and Improve memory and Steve's Stuff

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Re: Undefined reference to 'vtable for ...'

Mar 17th, 2008

> I was creating the derived class method definitions in a cpp file
> and couldn't get the project to progressively compile correctly.
> At my first method definition, a default constructor,
> the compiler kept spitting out this error message:

this is perhaps the most obscure error message that gcc (actually the linker) spits out, but the reason is simple:

the compiler has to put the (one and only one) vtable for a class into some object file or the other. it puts it into the object file for the translation unit where the definition of the first non-pure-virtual out-of-line virtual member function is present. if there is no such definition, you get this rather unhelpful linker error message.

you would be able to progressively compile the code even if a non-pure virtual function is not defined, but to be able to link without errors, every such function must have a definition (at least a stub). and to prevent the non-creation of a v-table by the compiler, at least one of the non-pure virtual functions will have to be defined out-of-line.

gcc has a faq about this: http://gcc.gnu.org/faq.html#vtables

> Am I to assume that the example in the book, as regards the inline feature
> of a derived class destructor, is in error.
i think it is not a particularly good book, but in this case neither the book nor the compiler is in error.
if you define the destructor inline, and void VintagePort::Show() const out-of-line, the error will go away. there has to be at least one out-of-line definition of a non-pure-virtual function.

note: the microsoft compiler (as well as several other compilers) does not require this; it instantiates a v-table with internal linkage in *every* translation unit in which such a header (all non-pure virtual functions are inline) is included. this violates the c++ one definition rule for v-tables, but as always, folks at redmond tend to value pragmatism highly. and they do give you __declspec(novtable) to suppress the proliferation of v-tables.

Last edited by vijayan121; Mar 17th, 2008 at 11:00 am.

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Re: Undefined reference to 'vtable for ...'

Mar 17th, 2008

Thank you very much, this has certainly cleared things up. In a way, I'm glad I came across this problem, hopefully it won't catch me out again, when progressively compiling.

Steve
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Re: Undefined reference to 'vtable for ...'

Feb 2nd, 2009

Hi ... I hope this helps someone out there....

I'm using netbeans with the C++ plugin in linux. I got the vtable error, and after a long time I figured out the solution..

basically the class I was trying to use was not added into the project. The class files (.cpp, .h) were in the project folder, and i was editing the files, etc... but they just wouldn't compile because they weren't added into the project.

so just right click the project, select "add existing items" and choose the file and add the files to the project... now it should compile, fingers crossed

--
http://www.vic-fontaine.com/

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Re: Undefined reference to 'vtable for ...'

Feb 18th, 2009

I have also seen this with GCC 4 when a virtual destructor is missing a body
eg:
virtual ~MyClass(void);
should be:
virtual ~MyClass(void){};

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Re: Undefined reference to 'vtable for ...'

Jul 16th, 2009

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Originally Posted by Procrastes

I have also seen this with GCC 4 when a virtual destructor is missing a body
eg:
virtual ~MyClass(void);
should be:
virtual ~MyClass(void){};

Also if you declare a virtual constructor but forget the '~' in its definition, e.g.:
virtual ~A(); // declaration in .h file
A::A() {} // .cpp implementation missing ~ in function name