Wired errors ??

This is a discussion on Wired errors ?? within the C++ Programming forums, part of the General Programming Boards category; Here I've Pasted My very Small ammount of Codes http://phpfi.com/246165 I am getting this Errors what does it mean ?? ...

  1. #1
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    Wired errors ??

    Here I've Pasted My very Small ammount of Codes http://phpfi.com/246165
    I am getting this Errors what does it mean ??
    Code:
    /tmp/ccRTY7b3.o: In function `main':
    op_overload.cpp:(.text+0xb7): undefined reference to `Point::Point()'
    collect2: ld returned 1 exit status
    Please help

  2. #2
    Frequently Quite Prolix dwks's Avatar
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    You have a constructor prototyped in the class:
    Code:
    Point();//default Constructor
    But you don't have an implementation. You need something like
    Code:
    Point::Point() {
    }
    like you have the copy constructor:
    Code:
    Point::Point(int a, int b){
    Alternatively, you could just go
    Code:
    Point() {} //default Constructor
    inside the class.
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
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  3. #3
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    Thanks I've changed te Constructor Blocks to this
    Code:
    Point(){}//default Constructor
    Point(int, int);//Constructor
    Point(const Point&);//Copy Constructor
    And its workin Now
    But What does the error Mean ??
    Why Its getting Compiled to op_overload.o with -c if it has Errors ??

  4. #4
    C++ Witch laserlight's Avatar
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    It is the linker that is complaining that it cannot find the implementation of Point().
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  5. #5
    Frequently Quite Prolix dwks's Avatar
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    Some errors cannot be detected by the compiler. As far as the compiler can tell, Point() has a Point() default constructor which takes no parameters, because you've declared it as such. It doesn't find the implementation of Point::Point(), but it's not too worried because it could be in a different source file. If you have different source files, you oculd so this:
    Code:
    /* one.cpp */
    int square(int x) {
        return x * x;
    }
    Code:
    /* main.cpp */
    #include <iostream>
    
    /* this is the prototype, equivalent to your declaration of Point() inside the class.
        It tells the compiler that this does in fact exist somewhere, and even though it
        can't find the implementation of this function, compile on. */
    int square(int x);
    
    int main() {
        std::cout << square(3) << std::endl;
        return 0;
    }
    Now when you compile main.cpp with
    Code:
    g++ -c main.cpp
    it compiles. But when you link your program, you have to add square.o as well, or else the linker won't be able to find square().
    Code:
    g++ -c main.cpp
    g++ -c square.cpp
    g++ -o test.exe main.o square.o  /* works */
    g++ -o test.exe main.o /* fails */
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


    Other boards: DaniWeb, TPS
    Unofficial Wiki FAQ: cpwiki.sf.net

    My website: http://dwks.theprogrammingsite.com/
    Projects: codeform, xuni, atlantis, nort, etc.

  6. #6
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    Ah!
    Thanks.

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