Article ID: 160074
Article Last Modified on 8/9/2004
APPLIES TO
- Microsoft Foundation Class Library 4.2, when used with:
- Microsoft Visual C++ 4.2 Enterprise Edition
- Microsoft Visual C++ 4.2 Professional Edition
This article was previously published under Q160074
SUMMARY
CRecordset::SetFieldNull() causes an assert or an access
violation if called for a parameter. Even if no assert or access violation
occurs, the parameter may not be set to Null.
If SetFieldNull() is
called before the recordset is open, the assert occurs in DBRFX.CPP at line 48:
ASSERT(prs->m_hstmt != SQL_NULL_HSTMT);
If SetFieldNull() is called after the recordset is open, then a call to
CRecordset::Requery() may assert in DBCORE.CPP at line 4055 or line 4062:
ASSERT(nParam < m_nParams);
If SetFieldNull() is called after the recordset is closed and before it
is reopened, you will see an access violation in DBCORE.CPP at line 4057:
m_pbParamFlags[nParam] |= AFX_SQL_FIELD_FLAG_NULL;
or at line 4064:
m_pbParamFlags[nParam] &= ~AFX_SQL_FIELD_FLAG_NULL;
NOTE: Visual C++ 5.0 has a new function called SetParamNull() that you
can use to avoid this problem. SetFieldNull() in Visual C++ 4.2 was not
designed to be called before calling CRecordset::Open(), and was not designed
to handle parameters.
The following
files are available for download from the Microsoft Download
Center:
Paramset.exe
For additional information about how
to download Microsoft Support files, click the following article number to view
the article in the Microsoft Knowledge Base:
119591 How to Obtain Microsoft Support Files from Online Services
Microsoft scanned this file for viruses. Microsoft used the most
current virus-detection software that was available on the date that the file
was posted. The file is stored on security-enhanced servers that help to
prevent any unauthorized changes to the file.
Microsoft has confirmed this to be a bug in the Microsoft
products listed at the beginning of this article. The problem has been fixed
with Visual C++ version 5.0 by adding a new function called SetParamNull().
MORE INFORMATION
Once you have downloaded Paramset.exe and run the EXE to
extract the CParamSet class files, add CParamSet.CPP to your project.
Change your recordsets to be derived from CParamSet rather than
CRecordset.
CRecordset::SetFieldNull() cannot be called before the
recordset is open. If you want to call SetFieldNull() to set parameters to Null
before calling CRecordset::Open(), then call CParamSet::SetParamNull() instead.
You will have to change the parameters that are passed to SetParamNull()
because SetFieldNull() requires a pointer to the parameter and SetParamNull()
requires a zero-based index.
In your implementation of the
DoFieldExchange() function, change each call to an RFX function for a parameter
to a call to the corresponding Param_RFX function.
REFERENCES
Visual C++ Books Online: CRecordset::SetFieldNull
Additional query words: kbVC420bug kbDSupport assert gpf crash
Keywords: kbbug kbfix kbdatabase kbfile kbvc500fix KB160074