View Compilation Error

0_0_13534765_6602.cpp: In function 'int compare(const void*, const void*)':
0_0_13534765_6602.cpp:46:23: error: invalid conversion from 'const void*' to 'const ti*' [-fpermissive]
  const struct ti *p = a;
                       ^
0_0_13534765_6602.cpp:47:23: error: invalid conversion from 'const void*' to 'const ti*' [-fpermissive]
  const struct ti *q = b;
                       ^
0_0_13534765_6602.cpp:49:12: error: 'const struct ti' has no member named 'e'
  return p->e - q->e;
            ^
0_0_13534765_6602.cpp:49:19: error: 'const struct ti' has no member named 'e'
  return p->e - q->e;
                   ^