How do function pointers in C work?

I had some experience lately with function pointers in C.
So going on with the tradition of answering your own questions, I decided to make a small summary of the very basics, for those who need a quick dive-in to the subject.


Functions pointers in C

Let's start with a basic function which we will be pointing to:
int addInt(int n, int m) {
    return n+m;
First thing, lets define a pointer to a function which receives 2 ints and returns and int:
int (*functionPtr)(int,int);
Now we can safely point to our function:
functionPtr = &addInt;
Now that we have a pointer to the function, lets use it:
int sum = (*functionPtr)(2, 3); // sum == 5
Passing the pointer to another function is basically the same:
int add2to3(int (*functionPtr)(int, int)) {
    return (*functionPtr)(2, 3);
We can use function pointers in return values as well (try to keep up, it gets messy):
// this is a function called functionFactory which receives parameter n
// and returns a pointer to another function which receives two ints
// and it returns another int
int (*functionFactory(int n))(int, int) {
    printf("Got parameter %d", n);
    int (*functionPtr)(int,int) = &addInt;
    return functionPtr;
But it's much nicer to use a typedef:
typedef int (*myFuncDef)(int, int);
// note that the typedef name is indeed myFuncDef

myFuncDef functionFactory(int n) {
    printf("Got parameter %d", n);
    myFuncDef functionPtr = &addInt;
    return functionPtr;


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