Type/offset/size of flexible array struct member

I have a question on how to correctly identify flexible array
type in clang_visitChildren walk.

With following example struct:

struct a {
  int a;
  int b[];

the attached program prints CXType::kind, which correctly shows
CXType_IncompleteArray value, but size and offset values are -2.

$ ./ex
Clang error 0
field a, size 4, offset -2, kind: 17
field b, size -2, offset -2, kind: 114

Is that expected? Is it enough to check for CXType_IncompleteArray
value in CXType::kind for flexible array type?