Protobuf-c: Nesting a message within a message creates a structure pointer

Question

I am new to protobuf usage. I am trying the following with protobuf-c to include a message within another message. It generated a structure pointer as below:

message Check {
    bool check_valid = 1;
}

message main_check {
    Check chk = 1;
}


//This generates a structure as below:
struct  _Check
{
   ProtobufCMessage base;
   protobuf_c_boolean check_valid;
};
struct  _main_check
{
    ProtobufCMessage base;
    Check *chk;  
};

What should be done differently to have a Check chk instead of *Check chk Also, I need to extend the requirement of having multiple messages defined within a oneof type.