Type Visualization in Visual Studio 2012 Debugger

Warning! Some information on this page is older than 5 years now. I keep it for reference, but it probably doesn't reflect my current knowledge and beliefs.

# Type Visualization in Visual Studio 2012 Debugger

Tue
23
Apr 2013

When you code in C++ and you have your own library of data types, especially containers, it would be nice to be able to see it in the debugger formatted in some readable way. In Visual C++/Visual Studio, there used to be a special file autoexp.dat designed for this purpose, as described in "Writing custom visualizers for Visual Studio 2005". But it had weird syntax and poor error reporting.

Now in Visual Studio 2012 there is a new way of defining debugger visualizations for native data types, called Native Type Visualization Framework (natvis). All you need to do is to create an XML file with ".natvis" extension following special format and place it in directory: %USERPROFILE%\Documents\Visual Studio 2012\Visualizers. Full documentation of this format is on this single MSDN page: "Creating custom views of native objects in the debugger". See also "Expressions in Native C++" and "Format Specifiers in C++".

For example, if you have a singly linked list:

template<typename T>
class CLinkedList {
   // ...
    struct CNode {
       T Value;
       CNode* Next;
    };
    size_t Count;
    CNode* Head;
};

Default visualization of a 3-element object in the debugger would look like this:

But if you create following natvis file:

<?xml version="1.0" encoding="utf-8"?>
<AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
   <Type Name="CLinkedList&lt;*&gt;">
       <DisplayString>{{Count = {Count}}}</DisplayString>
       <Expand>
           <Item Name="[Count]">Count</Item>
           <LinkedListItems>
               <Size>Count</Size>
               <HeadPointer>Head</HeadPointer>
               <NextPointer>Next</NextPointer>
               <ValueNode>Value</ValueNode>
           </LinkedListItems>
       </Expand>
   </Type>
</AutoVisualizer>

Next time you start debugging (restarting Visual Studio is not required), same object will be shown as:

Besides extracting single fields from objects, evaluating whole C++ expressions and formatting values into a string for summary of whole object, this framework is able to visualize following data structures:

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