Stuck on another C/C++ error

Atomic Pineapple

I'm still trying to port C++ from a Windows platform to Linux based Android (Posix).

The windows code uses a Queue or First in last out data structure.

In the Android build enviroment only the very basic c libraries are supplied so I cant use a list or a stack or a queue or a dequeue or anything helpful at all.

So after an internet search and some tutorial browsing I have come up with the following header and c file.

//queue.h

#include <stdio.h>
#include <stdlib.h>

typedef int ElementType;

#ifndef _Queue_h

  struct QueueRecord;
  typedef struct QueueRecord *Queue;

  int         IsEmpty(Queue Q);
  int         IsFull(Queue Q);
  Queue     CreateQueue(int MaxElements);
  void        DisposeQueue(Queue Q);
  void        MakeEmpty(Queue Q);
  void        Enqueue(ElementType X, Queue Q);
  ElementType Front(Queue Q);
  void        Dequeue(Queue Q);
  ElementType FrontAndDequeue(Queue Q);

#endif  /* _Queue_h */

//queue.c

#include "inc/queue.h"
#include <stdlib.h>

#define MinQueueSize (5)

struct QueueRecord {
  int Capacity;
  int Front;
  int Rear;
  int Size;
  ElementType *Array;
};

int IsEmpty(Queue Q) {
  return Q->Size == 0;
}

int IsFull(Queue Q) {
  return Q->Size == Q->Capacity;
}

Queue CreateQueue(int MaxElements) {
  Queue Q;

  if (MaxElements < MinQueueSize) {
    Error("CreateQueue Error: Queue size is too small.");
  }

  Q = malloc (sizeof(struct QueueRecord));
  if (Q == NULL) {
    FatalError("CreateQueue Error: Unable to allocate more memory.");
  }

  Q->Array = malloc( sizeof(ElementType) * MaxElements );
  if (Q->Array == NULL) {
    FatalError("CreateQueue Error: Unable to allocate more memory.");
  }

  Q->Capacity = MaxElements;
  MakeEmpty(Q);

  return Q;
}

void MakeEmpty(Queue Q) {

  Q->Size = 0;
  Q->Front = 1;
  Q->Rear = 0;

}

void DisposeQueue(Queue Q) {
  if (Q != NULL) {
    free(Q->Array);
    free(Q);
  }
}

static int Succ(int Value, Queue Q) {
  if (++Value == Q->Capacity) {
    Value = 0;
  }
  return Value;
}

void Enqueue(ElementType X, Queue Q) {

  if (IsFull(Q)) {
    Error("Enqueue Error: The queue is full.");
  } else {
    Q->Size++;
    Q->Rear = Succ(Q->Rear, Q);
    Q->Array[Q->Rear] = X;
  }

}

ElementType Front(Queue Q) {

  if (!IsEmpty(Q)) {
    return Q->Array[Q->Front];
  }
  Error("Front Error: The queue is empty.");


  return 0;

}

void Dequeue(Queue Q) {

  if (IsEmpty(Q)) {
    Error("Dequeue Error: The queue is empty.");
  } else {
    Q->Size--;
    Q->Front = Succ(Q->Front, Q);
  }

}

ElementType FrontAndDequeue(Queue Q) {

  ElementType X = 0;

  if (IsEmpty(Q)) {
    Error("FrontAndDequeue Error: The queue is empty.");
  } else {
    Q->Size--;
    X = Q->Array[Q->Front];
    Q->Front = Succ(Q->Front, Q);
  }
  return X;

}

The problem arises when I try to use this Queue in a C++ file.

//RTCPConnection.cpp

...

Queue m_InMsgs;

m_InMsgs = CreateQueue(10);

//The above seems to compile fine

...

while( (retVal == 0) && (m_InMsgs->Size > 0)) [B]//Line 237 error[/B]
{
	RTCP_Packet* msg=front(m_InMsgs); [B]//Line 239 error[/B]
	retVal = ProcessReport(msg, mask);
	Dequeue(m_InMsgs);
	if( msg != NULL ) delete msg;
}

...

while ( m_OutMsgs->Size > 0 && sentdata && (m_RAddrStruct.sin_port!=0) ) [B]//Line 348 error[/B]
{
       ......
}

...

if (result==SOCKET_ERROR)
{
	int error= errno;
	if ((error!=EWOULDBLOCK) || (error!=WSAEINPROGRESS))
	{
		m_OutMsgs.MakeEmpty(); [B]//Line 386 error[/B]
		m_Error=error;
	}
	}
	else
	{
		m_OutMsgs.MakeEmpty(); [B]//Line 392 error[/B]
		sentdata=true;
	}
	}
		else m_Error=-1;
	}
}

And I get the following errors:

apps/phone/project/jni//src/RTCPConnection.cpp: In member function 'int RTCP_Connection::ReceiveReport(UINT32&)':
apps/phone/project/jni//src/RTCPConnection.cpp:237: error: invalid use of
incomplete type 'struct QueueRecord'
apps/phone/project/jni/inc/queue.h:11: error: forward declaration of 'struct QueueRecord'
apps/phone/project/jni//src/RTCPConnection.cpp:239: error: invalid conversion from 'ElementType' to 'RTCP_Packet*'
apps/phone/project/jni//src/RTCPConnection.cpp: In member function 'int RTCP_Connection::SendData()':
apps/phone/project/jni//src/RTCPConnection.cpp:348: error: invalid use of
incomplete type 'struct QueueRecord'
apps/phone/project/jni/inc/queue.h:11: error: forward declaration of 'struct QueueRecord'
apps/phone/project/jni//src/RTCPConnection.cpp:386: error: request for member 'MakeEmpty' in '((RTCP_Connection*)this)->RTCP_Connection::m_OutMsgs', whic
h is of non-class type 'QueueRecord*'
apps/phone/project/jni//src/RTCPConnection.cpp:392: error: request for member 'MakeEmpty' in '((RTCP_Connection*)this)->RTCP_Connection::m_OutMsgs', which is of non-class type 'QueueRecord*'
make: *** [out/apps/phone/armeabi/objs/audiodatastream//src/RTCPConnectio
n.o] Error 1

I've been googling the errors but cant quite get my head around what they mean.

Can anybody help?

fasty

The queue you're using is written in C, but you're trying to treat it like a C++ class.

It's not m_Queue.MakeEmpty(), it's MakeEmpty(&m_Queue);

Look at the header file for the queue!

Also, you might run into C++ name mangling issues here.

Tobias Greeshman

As the other poster mentioned about mangling issues, so you may have to specify C linkage to stop the C++ compiler mangling the Queue library for some (if not all) declarations in your queue header file.