What will this C code do?

void main(){
int x=1;
printf("%d\n",x=2);
}

>>120
You mean an uninitialized variable? It would have an indeterminate value, but it would still have been allocated. If by unnamed variable you're referring to unnamed members of a struct or union, again, it would still be allocated somewhere. In the case of a flexible array member, it would have allocated duration.