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Q267993: Access Violation in Snatrc.dll When You Enable CPI-C API Traces

Article: Q267993
Product(s): Microsoft SNA Server
Version(s): 3.0 (all SP),4.0,4.0 SP1,4.0 SP2,4.0 SP3
Operating System(s): 
Keyword(s): kbsna300sp1 kbsna300sp2 kbsna300sp3 kbsna300sp4 sna4 kbsna400sp1 kbsna400sp2 kbsna400sp
Last Modified: 12-JUN-2001

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The information in this article applies to:

- Microsoft SNA Server, versions 3.0 SP1, 3.0 SP2, 3.0 SP3, 3.0 SP4, 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3 
- Microsoft Host Integration Server 2000 
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SYMPTOMS
========

An Access Violation error message may occur in the SNA Server Trace DLL
(Snatrc.dll) when CPI-C API tracing is enabled through the SNA Server Trace
program (Snatrace.exe). The symptoms that occur vary depending on the CPI-C
application and the context that it is running under. If Drwtsn32.exe is the
default debugger on the Windows NT or Windows 2000-based computer where tracing
is enabled, a Drwtsn32.log entry similar to the following may be created:

  Application exception occurred:
  App: dll\snatrc.dbg (<process id>)
  Exception number: c0000005 (access violation)

The function that fails is com_trc_dumpl.

If a Drwtsn32.log entry is not created, an application debugger such as NTSD,
CDB, or Visual Studio can be used to catch the Access Violation error message.
The following is the output obtained from an application debugger when the
Access Violation error message occurs:

  Access violation - code c0000005 (first chance)
  eax=00000000 ebx=fdc9afff ecx=00000000 edx=00000000 esi=78003e6d edi=02365001 eip=61d01cea esp=1c2cf4fc ebp=00000001 iopl=0 nv up ei pl zr na po nc
  cs=001b  ss=0023  ds=0023  es=0023  fs=0038  gs=0000 efl=00010246
  SNATRC!com_trc_dumpl+aa: 61d01cea 8a47ff           mov     al,[edi-0x1]            ds:0023:02365000=??
  0:038> kb
  ChildEBP RetAddr  Args to Child
  1c2cf54c 61d02358 00000021 61d124f0 02365000 SNATRC!com_trc_dumpl+0xaa
  1c2cf57c 61d08523 00000021 61d124f0 02364ff0 SNATRC!com_trc_dump+0x88
  1c2cf6b8 62e12058 00000001 00000017 1b8c03d0 SNATRC!seputrcp_d+0x3033
  602012b0 55536021 57c08556 0102840f 15ff0000 WCPIC32!seputrcp+0x7f [e:\sna40\shared\win32\semfcom.c @ 513]
  3d6ca151 00000000 00000000 00000000 00000000 0x55536021

If the CPI-C application is running as part of an MTX object under Microsoft
Transaction Server (MTS), an event similar to the following may be logged in the
Windows NT or Windows 2000 Application event log:

  Event ID: 4104
  Source: Transaction Server
  Description: An object call caused an exception.
  (Package: BCCS DSO) (ProgId: MCCMGSP.ExecuteTransaction)
  (CLSID: {61D8D9B8-80AF-11D2-81A6-006008A0C451})
  (Interface: ExecuteTransaction)
  (IID: {61D8D9B7-80AF-11D2-81A6-006008A0C451})
  (Method: 13)
  (Microsoft Transaction Server Internals Information:
  File: d:\viper\src\runtime\cw\cwlib.cpp, Line: 861).

After the Access Violation error message occurs, the associated MTX object(s)
stops responding (hangs).

CAUSE
=====

The following issues can cause the Access Violation error message in Snatrc.dll
when CPI-C API tracing is enabled:

- The tracing routine for the CMSTPN (Set_TP_Name) call ignores the
  TP_Name_Length field and writes a 64-byte TP_Name regardless of the actual
  length of the TP_Name. This can result in an Access Violation error message
  if the calling program allocates less than 64-bytes of buffer to store the
  TP_name.

- The tracing routine for the CMSSL (Set_Sync_Level) call causes an Access
  Violation error message if the calling program passes an invalid pointer for
  the sync_level parameter.

RESOLUTION
==========

To resolve this problem, obtain the latest service pack for SNA Server 4.0. For
additional information, please see the following article in the Microsoft
Knowledge Base:

  Q215838 How to Obtain the Latest SNA Server Version 4.0 Service Pack




WORKAROUND
==========

Disable CPI-C API tracing to prevent this problem from occurring.

STATUS
======

Microsoft has confirmed this to be a problem in Microsoft SNA Server versions
3.0, 3.0 SP1, 3.0 SP2, 3.0 SP3, 3.0 SP4, 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3.

This problem was first corrected in SNA Server 4.0 Service Pack 4.

MORE INFORMATION
================

In addition to correcting the problems found in the tracing routines for the
CPI-C CMSTPN and CMSSL calls, an exception handler has been added to the CPI-C
API tracing routines to protect applications from being affected if/when an
Access Violation error message occurs when CPI-C API traces are enabled. After
you apply this update, any future Access Violation error messages that occur
when you run CPI-C API traces will result in partially traced CPI-C verbs
without affecting the underlying CPI-C application.

Only CPI-C applications that call the CPI-C Set_TP_Name or Set_Sync_Level verbs
have the potential of experiencing the Access Violation error message described
in this article.

NOTE: SNA Server tracing (including CPI-C tracing) should not be enabled under
normal circumstances. SNA Server traces are used to troubleshoot specific
problems related to SNA Server and SNA Server related applications.

Additional query words:

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Keywords          : kbsna300sp1 kbsna300sp2 kbsna300sp3 kbsna300sp4 sna4 kbsna400sp1 kbsna400sp2 kbsna400sp3 kbSNA400sp4fix kbSNA400PreSP4fix 
Technology        : kbAudDeveloper kbSNAServSearch kbHostIntegServ2000 kbSNAServ400 kbSNAServ300SP3 kbSNAServ300SP1 kbSNAServ400SP1 kbSNAServ400SP2 kbSNAServ400SP3 kbSNAServ300SP2 kbSNAServ300SP4
Version           : :3.0 (all SP),4.0,4.0 SP1,4.0 SP2,4.0 SP3
Issue type        : kbbug
Solution Type     : kbfix

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