Under Windows NT, Win16 Applications Opening MS-DOS Devices Fail (167969)
The information in this article applies to:
- Microsoft Windows NT Server 4.0 Terminal Server Edition
- Microsoft Windows NT Workstation 4.0
- Microsoft Windows NT Server 4.0
This article was previously published under Q167969 SYMPTOMS
Under certain circumstances, data written to LPT1 from a 16-bit Windows
application running under Windows NT can corrupt other files. This
corruption occurs when the application opens any MS-DOS device (as listed
by MEM /D; for example, LPT1, COM1, CON, and so on) through the _lopen()
RTL function and opens other data files. When the application writes data
out through the LPT1 handle, the data is misrouted to one of the other
files.
CAUSE
Some devices are handled internally by NTDOS without calling on the Win32
I/O system directly. For example, LPT1 is handled by calling the Windows NT
emulated BIOS, which in turn uses OUT instructions to feed the data to the
emulated LPT1 port. In this case, WOW mishandles several Interrupt 21
calls, including read file and write file, trying to pass these calls to
Win32 but using an uninitialized bit of memory instead of a valid Win32
file handle. In some cases, this uninitialized memory will contain a value
that is a valid handle value in the WOW process, and the data will be read
from or written to that file instead of the intended device. In other
cases, the Win32 file API fails because the handle is invalid.
RESOLUTIONTo resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in the
Microsoft Knowledge Base:
152734 How to Obtain the Latest Windows NT 4.0 Service Pack
STATUSMicrosoft has confirmed that this is a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.
MORE INFORMATION
It is highly irregular for a 16-bit Windows application to write to LPT1
through MS-DOS; the entire Windows 3.1/Windows 95 GUI will stop responding
if the printer is slow or out of paper. The correct way would be to use
OpenComm() and WriteComm(), which perform the write in the background
(using an interrupt service routine) instead of blocking the computer (or
WOW in this case) until the write completes.
| Modification Type: | Minor | Last Reviewed: | 9/23/2005 |
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| Keywords: | kbHotfixServer kbQFE kb3rdparty kbbug kbfix KB167969 |
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