foo.c: In function 'main':
foo.c:17:3: error: 'for' loop initial declarations are only allowed in C99 mode
   for(int i=1;i<=strlen(tmp1);i++)
   ^
foo.c:17:3: note: use option -std=c99 or -std=gnu99 to compile your code
foo.c:18:3: error: 'for' loop initial declarations are only allowed in C99 mode
   for(int j=1;j<=strlen(tmp2);j++)
   ^