How to Correctly Call a Member Function Using a Pointer in C ?

Calling Through a Member Function Pointer

In C , member function pointers allow us to treat member functions like regular functions through pointers. However, certain syntax rules must be followed to avoid compilation errors.

Consider the following code, where we attempt to call the walk member function of the cat class using a member function pointer:

class cat {
public:
   void walk() {
      printf("cat is walking \n");
   }
};

int main(){
   cat bigCat;
   void (cat::*pcat)();
   pcat = &cat::walk;
   bigCat.*pcat();
}

The above code fails to compile with the error "bigCat.*pcat(); statement doesn't compile." This occurs because there's a precedence issue with the syntax.

Member function pointers use the "." operator, while function calls use normal parentheses. The precedence of function calls is higher than that of the "." operator.

To fix the issue, additional parentheses are required to override the precedence rule:

(bigCat.*pcat)();

With this correction, the code will now properly call the walk function through the member function pointer.

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