| here is the original text of the patch. It appears to be on a VC 2.0
problem. Upgrading to VC 4.2b should eliminate the problem. I can't
stress strongly enough the desirability of an upgrade. HOwever, if you
can't upgrade, you can apply the change below to the MFC source code,
and rebuild the MFC. You cannot redistribute the rebuilt MFC DLLs
unles you rename them to be something other than MFC.
This article is about VC 2.0. The article contains the fix (a source
change to DBRFX.CPP) and requires the user to rebuild the MFC
libraries. I gave the source a cursory check and it looks like the fix
was implemented, but, it also looks like there's a typo. SQL_VARCHAR
is being used in the conditional instead of nSqlType == SQL_VARCHAR.
If the customer copied the patch from the article, then the statement
should be correct and there might be something else at fault. This
particular bug was fixed in 4.x.
FIX: Assertion Fails When Use RFX_Text() w/ SQL_VARCHAR Column
ID: Q120888
---------------------------------------------------------------------
The information in this article applies to:
The Microsoft Foundation Classes (MFC), included with:
- Microsoft Visual C++ for Windows, versions 1.5 and 1.51
- Microsoft Visual C++, 32-bit Edition, version 2.0
---------------------------------------------------------------------
SYMPTOMS
========
An assertion failure occurs when using RFX_Text() with a column of type
SQL_VARCHAR that has a column width greater than 255 bytes.
CAUSE
=====
The column width for a column with SQL type of SQL_VARCHAR is usually
less
than 256 bytes. The ASSERT on line 1747 is verifying that the column
width
is less than 256 bytes unless the column type is SQL_LONGVARCHAR or
SQL_LONGBINARY. However some drivers implement SQL_VARCHAR type columns
that allow more than 255 bytes; in which case, the assertion is not
valid.
STATUS
======
Microsoft has confirmed this to be a bug in the Microsoft products
listed
at the beginning of this article. This bug was corrected in Visual C++
versions 1.52 and 2.1.
RESOLUTION
==========
The problem occurs in the function CFieldExchange::GetColumnType().
Because
this function is not virtual, there is no easy workaround.
You could replace the GetColumnType function as well as the RFX_Text()
function but that would entail adding all of the RFX_Text() function to
your application to take care of a problem occurs only in a _DEBUG
build
because ASSERTs are removed in release builds.
Instead of re-implementing RFX_Text here are two other approaches:
- Ignore the invalid assertion failure by choosing the Ignore button
on
the Assertion failed message box. This might not be an option if the
assertion failure is raised frequently.
- Modify the assertion in the MFC code. This requires that you rebuild
the
MFC libraries. For details on rebuilding the MFC Libraries, please
see
the section titled "How To Build Other Library Versions" in the
"Class
Library User's Guide." Or read the README.TXT file located in the
MFC
source directory (the default is: \MSVC\MFC\SRC). To modify the
assertion, change the code in the CFieldExchange::GetColumnType
function in DBRFX.CPP:
From:
ASSERT(dwT <= 255 || nSqlType == SQL_LONGVARBINARY ||
nSqlType == SQL_LONGVARCHAR);
To:
ASSERT(dwT <= 255 || nSqlType == SQL_VARCHAR ||
nSqlType == SQL_LONGVARBINARY ||
nSqlType == SQL_LONGVARCHAR);
|