How do you swap elements of a struct array in c?

Question

I've seen the couple other question regarding this topic, but none of the answers have worked for me.

My swapClasses method follows:

void swapClasses(struct ClassInfo *p1, struct ClassInfo *p2){
    ClassInfo *temp = p1;

    *p1 = *p2;
    *p2 = *temp;
}

But when I execute the code and attempt to add a class that should technically appear first in the array, it is just added to the end. No swapping takes place even though I know that portion of the code executes (tested with a simple print statement). I believe there is something wrong with the way I'm using pointers. Can anyone advise?

Answer 1

Getting a pointer to an element in the array won't save that element from being overwritten by a write through another pointer to it. Therefore your swap function is wrong. You should be copying the first item into the temporary, like this:

void swapClasses(struct ClassInfo *p1, struct ClassInfo *p2){
    ClassInfo temp = *p1;
    *p1 = *p2;
    *p2 = temp;
}