"dereferencing pointer to incomplete type" build error

- root cause of build error "dereferencing pointer to incomplete type"

This error occur that can't find struct.

1. didn't describe struct.

2. struct use upper line before describe struct.

ex) line 10 : use struct

     line 30 : describe struct

3. miss #include file

"dereferencing pointer to incomplete type"

빌드애러가 났을때 원인

1. struct 를 정의하지 않았다.

2. struct 를 정의하는 라인보다 위에서 사용했다.

ex) line 10 : struct 사용

line 30 : struct 구현

3. 적절한 #include 를 빼먹었다.