What is the size of an empty struct in C?

on VC 8 It gives error if we try to get the sizeof empty struct, on the other way round on linux with gcc it gives size 1 because it uses gcc extention instead of c language specification which says this is undefined behaviour.

struct node
{
// empty struct.
};

int main()
{
printf("%d", sizeof(struct node));
return 0;
}

on windows vc 2005 It gives compilation error on linux with gcc it gives size 1 because gcc extension http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Empty-Structures.html#Empty-Structures (As Pointed out by Michael Burr)