What is a function pointer in C?
Educative Answers TeamGrokking Modern System Design Interview for Engineers & Managers
Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.
Just like an integer pointer or a char pointer, a function pointer is a variable that stores the address of a function.
Syntax
A function pointer is initialized as follows:
void (*funcPtr)(int);
We can breakdown the above syntax into the following components:
funcPtris a pointer to a function.voidis the return type of that function.intis the datatype of the argument of that function.
Once initialized, you can make funcPtr point to a function like this:
funcPtr = &foo;
foo is the name of the function which is being pointed to.
Note: The ampersand (&) sign is optional. Writing
funcPtr = foo;is a valid syntax as well.
The illustration below shows how funcPtr points to the function foo. The funcPtr variable simply stores the address of the function.
Examples
Consider the example below which uses a function pointer to a void function.
In lines 6 and 7 of the code snippet below, the variable funcPtr points to the function showMessage(). The function is then called, using the name of the function pointer variable funcPtr.
void showMessage() {printf("Hello from the function.");}int main() {void (*funcPtr)();funcPtr = &showMessage;funcPtr();}
Let’s have a look at another example which utilizes a function pointer that takes several arguments.
In the example below, the multiplier takes three integers as arguments, the function pointer, to the function multiplier, is initialized with the three integers in line 6.
The function is invoked using the name of the function pointer variable funcPtr.
int multiplier(int num1, int num2, int num3) {return num1 * num2 * num3;}int main() {int (*funcPtr)(int, int, int);funcPtr = &multiplier;int result = funcPtr(5,5,2);printf("%d", result);}
RELATED TAGS
Grokking Modern System Design Interview for Engineers & Managers
Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.
