C array size given by variable

Question

I found some code today that confused me. It did something like this:

#include 

int main(int argc, char **argv) {
    int x = 5;
    int foo         


        

Answer 1

The array foo is on the stack so how could it be expanded by x?

gcc simply moves the stack pointer:

subq    %rax, %rsp

Link to full example with assembly output