Prototype *varsize field where CEEDOD is used in the caller to determine the length

I've the following RPG export procedure, can someone help me protoype this in C?
d SndMsg PR opdesc
d SndMsg PI opdesc
d MsgInId 10 const
d MsgInData 32766 const options(*varsize:*nopass:*omit)
d MsgInType 10 const options(*nopass:*omit )
d MsgFile 10 const options(*nopass:*omit)
d MsgLib 10 const options(*nopass:*omit)
d MsgInQueue 10 const options(*nopass:*omit)

I tried below and is getting a CZM0879 compile error:
#ifdef sndMsg_Prototype
typedef struct {
char value[10];
} sndMsg_msgID_T;

typedef struct {
char value[32766];
} sndMsg_msgData_T;

typedef struct {
char value[10];
} sndMsg_msgType_T;

typedef struct {
char value[10];
} sndMsg_msgFile_T;

typedef struct {
char value[10];
} sndMsg_msgLib_T;

typedef struct {
char value[10];
} sndMsg_msgQueue_T;

void
sndMsg(
const sndMsg_msgID_T *msgID,
const sndMsg_msgData_T *msgData,
const sndMsg_msgType_T *msgType,
const sndMsg_msgFile_T *msgFile,
const sndMsg_msgLib_T *msgLib,
const sndMsg_msgQueue_T *msgQueue);

#pragma map (sndMsg, "SNDMSG");
#pragma descriptor (void sndMsg(void,*))
#endif