If I understand right, this is mandatory: void example(int n) { printf("%zu", sizeof(int[n])); } void example2(int n, int (*a)[n]) { } This is optional:

If I understand right, this is mandatory: void example(int n) { printf("%zu", sizeof(int[n])); } void example2(int n, int (*a)[n]) { } This is optional: void example3(int n) { int x[n]; }