Linked error in C++ builder 6.0

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Hello!
I'm using C++ builder 6.0 and coding this:

XML

//---------------------------------------------------------------------------
#include <vcl.h>
#pragma hdrstop
#include <iostream.h>
#include <conio.h>
#include <string.h>
#pragma argsused
class Mystring {  //now with conversion operator
    char *s;
    int size;
    public:
    Mystring(const char *);
    Mystring();
    operator const char * () { return s; } //conversion operator
    //...
};
int main(int argc, char* argv[])
{
    Mystring str("hello world");
    int n = strcmp(str, "Hello");
    cout<<str<<endl;
    getch();
    return 0;
}

and got this error:
[Linker Error] Error: Unresolved external 'Mystring::Mystring(const char *)' referenced from E:\_TPU\_KI 1 NAM 3\_OOP\LAB5\DEBUG_BUILD\UNIT.OBJ

It's the same error when compiling in Visual C++ 2008.
May someone tell me what is it? how can i solve it? Is my program correct?
Thank you very much!

Posted 12-Jan-11 19:11pm

svatstika

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2 solutions

Solution 2

You can check if Mystring(const char *) has defined properly.

Posted 12-Jan-11 19:40pm

KingsGambit

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tolw · Accepted Answer · 2011-01-12T19:35:00

I don't know if you posted your entire code, but if you did, than you only declare the constructors, you never actually define them. Try changing the class definition to this:

C#

class Mystring {  //now with conversion operator
    char *s;
    int size;
    public:
    Mystring(const char *str)
    {
         //do something here - like make a copy of str and assign it to s
    }
    Mystring()
    {
         //do something here - like set s to NULL
    }
    operator const char * () { return s; } //conversion operator
    //...
};

You may also define the constructors outside the class - but my suggestion is to do some reading about c++ first. Good luck!!