FIX: Changes Lost When Changing Variable During Debugging

• Microsoft Visual C++, Enterprise Edition, version 4.2

SYMPTOMS

When you debug a SQL Server-stored procedure, if you change a variable or parameter to a value that is longer than the declared size of the variable or parameter, your changes will be lost without warning in the next step of the debugger.

CAUSE

Developer Studio accumulates all changes made to variables and parameters and then ships them across to SQL Server when the user moves to the next step. SQL Server may either accept or reject the changes. In this case, it rejects because of buffer overflow. MSDEV shows the valid values of the variables in the next step and ignores the invalid assignment that the user specified.

RESOLUTION

SQL Server will only accept changes that satisfy the declaration of the variable or parameter. MSDEV does not impose this limitation on values entered in the debugger. Therefore, just because the MSDEV accepted a value for a variable or parameter, do not conclude that that value will necessarily be the one that is used thereafter in the execution of the stored procedure. The deciding factor is whether SQL Server accepts the new value.

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++, Enterprise Edition, version 5.0.

MORE INFORMATION

As an example of this behavior, if you have the following variable declaration in your stored procedure:

   declare @name varchar(10)
   select @name = 'Value'

However, as soon as you step to the next statement, "@name" will revert to the value it had before you changed it.

Keywords          : vcbuglist420 VCEntIDE VCEntIss VCEntSQLDebug vcfixlist500 kbprg kbbuglist kbfixlist
Technology        : kbMfc
Version           : 4.2
Platform          : NT WINDOWS
Issue type        : kbbug
Solution Type     : kbfix