CODEWITHSUNDEEP
c++pointerstypedef
gorootde
gorootde

Reputation: 4073

C++ typedef static function pointer: undefined symbol

//class.h
 typedef double (*ffunct)(double x1, double y1, double x2, double y2);
 class Class {
    public:
        static ffunct myfunct;
        static void setFunct();
        static double doSomething(double x1, double y1, double x2, double y2);
        static void call();
 }

 //class.cpp
 void Class::setFunct(){
     Class::myfunct=Class::doSomething;
 }
 double Class::doSomething(double x1, double y1, double x2, double y2) {
     cout << "Hello World" << endl;
 }
 void Class::call() {
     Class::myfunct(1.0,2.0,3.0,4.0);
 }
 //main.cpp
 …
 Class::setFunct();
 Class::call();
 …

Running the programm results in Undefined symbols for architecture x86_64: "Class::myfunct", referenced from Class::setFunct, Class::call…

So what am I doing wrong?

Upvotes: 0

Views: 990

Answers (4)

diwatu
diwatu

Reputation: 5699

add one line on the top of your .cpp file:

ffunct Class::myfunct=NULL;

Upvotes: 0

Mike Vine
Mike Vine

Reputation: 9837

static ffunct myfunct; is a declaration

You need a definition of it also in the cpp file

ffunct Class::myfunct;

Upvotes: 1

David G
David G

Reputation: 96835

Your prototype of doSomething has a return type of double, but your implementation thereof has a return type of void.

static double doSomething(...)
...
void Class::doSomething(...)

Fixing this won't clear all the errors however. You still have a few more as the other answers mention.

Upvotes: 1

Mark Ransom
Mark Ransom

Reputation: 308392

In your cpp file you need one more line:

ffunct Class::myfunct = NULL;

The class declaration said that the variable would exist somewhere but you never gave it a definition. Since it's not part of each object it has to be defined separately.

Upvotes: 2

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