Q107428: FIX: Extra New Line Added to Debug Output in Visual Debugger

Article: Q107428
Product(s): Microsoft C Compiler
Version(s): 1.00
Operating System(s): 
Keyword(s): kbDebug kbidekbbuglist kbfixlist
Last Modified: 27-JUL-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- The Integrated Debugger, included with:
   - Microsoft Visual C++, 32-bit Editions, version 1.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

When using the Visual Workbench debugger, a new line is inserted in the
debugging output window every time debugging information is output through the
CDumpContext insertion operator or OutputDebugString(). This interferes with
formatting done for the debug output.

CAUSE
=====

A new line is inserted by the debugger after every call to the Windows 3.1
application programming interface (API) function OutputDebugString(). In the
Microsoft Foundation Classes (MFC), the insertion operator (<<) for
CDumpContext eventually maps to a call to OutputDebugString(), so every
invocation of << for a CDumpContext object also introduces a new line in
the output window.

RESOLUTION
==========

The following are three suggested workarounds:

- Use the WinDbg debugger that ships with the Microsoft Win32 Software
  Development Kit (SDK) for Windows NT. WinDbg does not insert uncalled for new
  lines into the debugging output.

- Consolidate debugging output into strings that can be displayed with a single
  call to OutputDebugString or with a single insertion into the dump context.

- Add additional lines of debugging information to indicate the beginning and
  end of a sequence of debugging output. For example,

     void CPerson::Dump( CDumpContext &dc ) const
      {
         dc << "Begin dump of CPerson object";  // identify dump start
         CObject::Dump( dc );
         dc << "Name: " << m_name;
         dc << "Age: " << m_years;
         dc << "End dump of CPerson object";    // identify dump end
      }

STATUS
======

Microsoft has confirmed this to be a bug in the products listed at the beginning
of this article. This problem was corrected in Visual C++ 2.0.

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

The following code fragment demonstrates the problem that occurs when calling
OutputDebugString directly. The output that would normally appear on the same
line actually displays over three lines:

Code
----

     OutputDebugString("This");
     OutputDebugString("output");
     OutputDebugString("takes three lines.\n");

Output
------

  This
  output
  takes three lines.

The code fragment below demonstrates how each insertion of debugging text into
the afxDump context causes a new line to appear in the output window:

     void CPerson::Dump( CDumpContext &dc ) const
     {
        CObject::Dump( dc );
        dc << m_name << " is ";
        dc << m_years << " years old.\n";
     }

A call to myPerson.Dump(afxDump) produces the following output in the Visual
Workbench's output window:

  a
  CObject
   at
  $18FC80

  FirstName LastName
   is
  30
   years old.

The following is what is desired:

  a CObject at $3917477E FirstName LastName is 30 years old.

Additional query words: newline afxDump 1.00 1.10

======================================================================
Keywords          : kbDebug kbide kbbuglist kbfixlist
Technology        : kbVCsearch kbAudDeveloper kbIntegratedDebugger
Version           : 1.00
Issue type        : kbbug
Solution Type     : kbfix

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