View Compilation Error

0_0_28347898_18769.c: In function 'main':
0_0_28347898_18769.c:10:9: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
         for(int i = 0; i < len; i++)
         ^
0_0_28347898_18769.c:10:9: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code