CreateFileMapping returns ERROR_INVALID_HANDLE - c++

Question

I am trying to use CreateFileMapping for the first time and it is giving me this error when I use GetLastError():
ERROR_INVALID_HANDLE: The handle is invalid.
Here is my code:
// create the name of our file-mapping object
nTry++; // Ensures a unique string is used in case user closes and reopens
wsprintfA(szName, FS6IPC_MSGNAME1 ":%X:%X", GetCurrentProcessId(), nTry);
// stuff the name into a global atom
m_atom = GlobalAddAtomA(szName);
if (m_atom == 0)
{ *pdwResult = ERR_ATOM;
return FALSE;
}
// create the file-mapping object
m_hMap = CreateFileMappingA(
(HANDLE)0xFFFFFFFF, // use system paging file
NULL, // security
PAGE_READWRITE, // protection
0, MAX_SIZE+256, // size
szName); //
EDIT:
The first issue was resolved, but now my program crashes somewhere else.
#define FS6IPC_MESSAGE_SUCCESS 1
#define FS6IPC_MESSAGE_FAILURE 0
// IPC message types
#define FS6IPC_READSTATEDATA_ID 1
#define FS6IPC_WRITESTATEDATA_ID 2
// read request structure
typedef struct tagFS6IPC_READSTATEDATA_HDR
{
DWORD dwId; // FS6IPC_READSTATEDATA_ID
DWORD dwOffset; // state table offset
DWORD nBytes; // number of bytes of state data to read
void* pDest; // destination buffer for data (client use only)
} FS6IPC_READSTATEDATA_HDR;
// write request structure
typedef struct tagFS6IPC_WRITESTATEDATA_HDR
{
DWORD dwId; // FS6IPC_WRITESTATEDATA_ID
DWORD dwOffset; // state table offset
DWORD nBytes; // number of bytes of state data to write
} FS6IPC_WRITESTATEDATA_HDR;
while (*pdw)
{ switch (*pdw)
{ case FS6IPC_READSTATEDATA_ID:
pHdrR = (FS6IPC_READSTATEDATA_HDR *) pdw;
m_pNext += sizeof(FS6IPC_READSTATEDATA_HDR);
if (pHdrR->pDest && pHdrR->nBytes)
CopyMemory(pHdrR->pDest, m_pNext, pHdrR->nBytes);
m_pNext += pHdrR->nBytes; // Debugger says the issue is here
break;
case FS6IPC_WRITESTATEDATA_ID:
// This is a write, so there's no returned data to store
pHdrW = (FS6IPC_WRITESTATEDATA_HDR *) pdw;
m_pNext += sizeof(FS6IPC_WRITESTATEDATA_HDR) + pHdrW->nBytes;
break;
default:
// Error! So terminate the scan
*pdw = 0;
break;
}
pdw = (DWORD *) m_pNext;
}

Answer 1

I'm guessing you're running on a 64-bit system, on which HANDLEs are 64 bits. The OS is quite right—the handle value 0x00000000FFFFFFFF is an invalid handle value for your process.
What exactly are you trying to do? If you want to create a file mapping backed by an actual file, pass in the handle for that file. If you want to a create a file mapping backed by the paging file instead, pass in INVALID_HANDLE_VALUE. INVALID_HANDLE_VALUE happens to be (HANDLE)-1, which is 0xFFFFFFFF on 32-bit systems but 0xFFFFFFFFFFFFFFFF on 64-bit systems, but that doesn't really matter since you should just use the symbolic value INVALID_HANDLE_VALUE in any case.
If your application is crashing when you pass in INVALID_HANDLE_VALUE, it's not because the call to CreateFileMapping is failing, it's for some other reason, and you should debug that.