View Compilation Error

0_0_29550541_25632.c: In function 'f':
0_0_29550541_25632.c:11:3: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
   for (int i1 = 2; i1 <= n; i1++) {
   ^
0_0_29550541_25632.c:11:3: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code