foo.c: In function 'main':
foo.c:12:2: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
  for(int i=0;i<=N-1;i++) 
  ^
foo.c:12:2: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code