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Q157903: FIX: Changes Lost When Changing Variable During Debugging

Article: Q157903
Product(s): Microsoft C Compiler
Version(s): WINDOWS:4.2
Operating System(s): 
Keyword(s): kbDebug kbEEdition kbide kbSQL kbVC kbVC500fix kbSQLProg
Last Modified: 04-AUG-2001

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The information in this article applies to:

- Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 
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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'

and you change "@name" to a value that is longer than 10 characters (using the
watch window) while debugging, the changes will be accepted and MSDEV will show
the new value in the watch window.

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

Additional query words: kbVC420bug kbDSupport

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Keywords          : kbDebug kbEEdition kbide kbSQL kbVC kbVC500fix kbSQLProg 
Technology        : kbVCsearch kbAudDeveloper kbVC420 kbVC32bitSearch
Version           : WINDOWS:4.2
Issue type        : kbbug
Solution Type     : kbfix

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