Problems in Passing File Handle to DLL

[Igor Vartanov]

Please see the attached sample that passes file handle to dll within the same process. The code does just fine:

D:\Temp\87>87.exe C:\hiberfil.sys
EXE: last error 32

D:\Temp\87>net helpmsg 32

The process cannot access the file because it is being used by another process.


D:\Temp\87>87.exe 87.exp
EXE: last error 2

D:\Temp\87>net helpmsg 2

The system cannot find the file specified.


D:\Temp\87>87.exe 87dll.exp
EXE: dwFlags = 0
DLL: dwFlags = 0

D:\Temp\87>87.exe 87.exe
EXE: dwFlags = 0
DLL: dwFlags = 0

But when I close handle before passing it to DLL...

#include <windows.h>
#include <tchar.h>
#include <stdio.h>

BOOL testHandle(HANDLE hFile);

int _tmain(int argc, LPCTSTR* argv)
{
	if (argc < 2)
	{
		_tprintf(TEXT("No path specified. Quit.\n"));
		return 1;
	}

	BOOL success = FALSE;
	LPCTSTR lpszFileName = argv[1];
	HANDLE hHandle = CreateFile(lpszFileName, GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
	if (INVALID_HANDLE_VALUE != hHandle)
	{
		DWORD dwFlags = 0;
		success = GetHandleInformation(hHandle, &dwFlags);
		if (success)
		{
			_tprintf(TEXT("EXE: dwFlags = %d\n"), dwFlags);
			CloseHandle(hHandle);
			success = testHandle(hHandle);
		}
	}

	if (!success)
	{
		DWORD err = GetLastError();
		_tprintf(TEXT("EXE: last error %d\n"), err);
		hHandle = NULL;
	}

	CloseHandle(hHandle);

	return 0;
}

... the handle is reported invalid

D:\Temp\87>87.exe 87dll.exp
EXE: dwFlags = 0
DLL: last error 6
EXE: last error 6