Pointer to Functions
Explore how to declare and use function pointers in C for indirect function calls, passing functions as arguments, and returning them. Understand how this enables callback behavior, dynamic selection of functions at runtime, and flexible program design.
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So far, we have used pointers to store the address of variables. However, in C, functions also have addresses. Just like variables, functions occupy memory, and their starting address can be stored in a pointer.
A function pointer allows a program to refer to a function indirectly. Instead of calling a function by name, we can store its address in a variable and call it through that variable. This makes programs more flexible. It allows functions to be:
Passed as arguments to other functions.
Selected at runtime.
Used to implement callback behavior.
Declaring a function pointer
Consider a simple function:
int add(int a, int b) {return a + b;}
Here, the name add represents the address of that function. When used in most expressions, it behaves like a pointer to the function. You can assign it to a pointer variable.
The syntax for declaring a function pointer must match the function’s return type and parameter list. The general form is: return_type (*pointer_name)(parameter_types);
For the add function above, we can declare as:
int (*operation)(int, int);
This declares operation as a pointer to any function that takes two int arguments and returns an int. The parentheses around *operation are required. Also, the function pointer type must match the function’s return type and parameter types. A mismatch may compile with warnings but can lead to incorrect behavior.
Calling through a function pointer
Like assigning any value to a variable, we can assign the function's address to ...