Whats the errors not able to understand - c++

Question

i made a code but has errors and wan't able to solve them:-
the following errors are in one of mine header file(code shown below)
error C2143:syntax error : missing ';' before '*'
error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
Header file code:-
#ifndef _DEVICE_SOURCE_FICARD_HH
#define _DEVICE_SOURCE_FICARD_HH
#ifndef _FRAMED_SOURCE_HH
#include "FramedSource.hh"
#endif
#include <DeviceSource.hh>
typedef struct LtagBufferEntry
{
char *pBuffer;
struct LtagBufferEntry *pNext;
} LBufferEntry;
class FICardDeviceParameters {
public:
(RetEntry*)(*p_lm_lock_fn)( void *data ); //error at this line
void (*p_lm_unlock_fn)( void *data );
int nFICardFrameSize;
//%%% TO BE WRITTEN %%%
};
class DeviceSourceFICard: public DeviceSource {
public:
static DeviceSourceFICard* createNew(UsageEnvironment& env, FICardDeviceParameters fi_params,
DeviceParameters params);
protected:
DeviceSourceFICard(UsageEnvironment& env, FICardDeviceParameters fi_params, DeviceParameters params);
// called only by createNew(), or by subclass constructors
virtual ~DeviceSourceFICard();
private:
// redefined virtual functions:
virtual void doGetNextFrame();
private:
void deliverFrame();
private:
DeviceParameters fParams;
LBufferEntry *pData;
char * pRetData;
//int nFICardFrameSize;
FICardDeviceParameters fiParams;
};
#endif //_DEVICE_SOURCE_FICARD_HH
Defination of RetEntry:-
typedef struct tagRetBuffer
{
char *pBuffer;
int nDataLn;
} RetEntry;
void InitBufferHandling();
void TransferBuffer( void *pBuffer );
RetEntry *lm_lock_fn( void *data );
void lm_unlock_fn( void *data );
int initLm555Settings(void);
void play();
void afterPlaying(void*);
void init_play();
void StartRTPProcess(void);
How to fix them...

Answer 1

The problem is that the compiler does not know what RetEntry is in the expression:
(RetEntry*)(*p_lm_lock_fn)( void *data );
You must either include the header that provides the definition or else declare it in your current header. From the code below it seems to be a typedef to tagRetBuffer, so to declare it in the current translation unit you will need to declare the struct and the typedef:
struct tagRetBuffer;
typedef tagRetBuffer RetEntry;
Now, I would suggest that you avoid those typedef's altogether, in C++ the compiler will search for types if needed. You can just do:
struct RetEntry
{
char *pBuffer;
int nDataLn;
};
And then use RetEntry anywhere as if it was a typedef'ed name. Note that there are differences, but that in 99% of the cases you will not notice. And when you do notice it might even be to your advantage (for example, you cannot declare a typedef, so you need to declare the typedef'ed name and then redefine the typedef as per the first suggestion here).