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Using C++ Debug Visualizers in VS2015

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Using C++ Debug Visualizers in VS2015

Need to deubg in C++? Here's how to use debug visualizers in Visual Studio 2015.

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I have been using the .NET debug visualizers (and DebuggerDisplay atribute) for a long (long) time and I like the way they make my code easy(ier) to debug. Until recently I was not aware that Visual Studio has a similar capability for C++.

Any C++ dev armed with Visual Studio can use XML files to create debug visualizers, In Visual Studio 2015 there’s no longer a need to to deploy these visualizer on each on each developer machine – just add the new, easy to write visualizer to your project and your team gets to automatically use it via the magic of source control.

Consider the following class:

class Customer
{
 int m_id;
 string m_firstName;
 string m_surname;
 int m_age;
 Gender m_gender;
 string m_emailAddress;
 string m_telephoneNumber;
 Address m_address;

 // ...
};

In order to use a debug visualizer just add a new natvis file - Add new Item and choose the Debugger visualization file (.netvis) template.

image

And presto - a new debug visualization file would be added to your project.

After a little tinkering I’ve created the following:

<?xml version="1.0" encoding="utf-8"?>
<AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
  <Type Name="Customer">
    <DisplayString>Name: {m_firstName}</DisplayString>
    <Expand>
    <Item Name="Id">m_id</Item>
    <Item Name="Gender">m_gender</Item>
    <Item Name="Age">m_age</Item>
    <Item Name="Address">m_address</Item>
    </Expand>
  </Type>
</AutoVisualizer>

Which was really simple to write:

  • To display the customer’s name automatically I’ve addedDisplayString with “Name:” and the value in curly brackets.
  • Right now I only care about four of the customer’s fields so I’ve addedExpends with those fields

And I got the following in my watch window:

image

Which is nice but not great – I would like to see the customer full name and so I’ve tweaked DisplayString a bit:

<?xml version="1.0" encoding="utf-8"?>
<AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
  <Type Name="Customer">
    <DisplayString>Name: {m_firstName, sb} {m_surname, sb}</DisplayString>
    <Expand>
    <Item Name="Id">m_id</Item>
    <Item Name="Gender">m_gender</Item>
    <Item Name="Age">m_age</Item>
   <Item Name="Address">m_address</Item>
    </Expand>
  </Type>
</AutoVisualizer>

And I did it during a debug session – seeing the results each time I save thenatvis file:

CppDebugVisulaizer1

I’ve used Format specifier (that’s the “sb”) to remove the quotes and make the name more human readable. In fact I can use another formatter for Gender –en (for Enum).

I would also like to make the customer address visible in the display string. Since Address is a class I’ll first define a visualizer for it (blow the customer visualizer) and update the customer visualizer to use the address as part of the display string:

<?xml version="1.0" encoding="utf-8"?>
<AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
  <Type Name="Customer">
    <DisplayString>{m_firstName, sb} {m_surname, sb} [{m_address}]</DisplayString>
    <Expand>
      <Item Name="Id">m_id</Item>
      <Item Name="Gender">m_gender, en</Item>
      <Item Name="Age">m_age</Item>
      <Item Name="Address">m_address</Item>
    </Expand>
  </Type>
  <Type Name="Address">
    <DisplayString>{m_streetAddress, sb}, {m_city, sb}, {m_country, sb} Zip:{m_zipCode}</DisplayString>
  </Type>
</AutoVisualizer>

This doesn’t seem much – but in order to get similar behavior in .NET I’ve needed to use OzCode – since nested/recursive DebugDisplayAttribute is not supported in .NET. 

Conclusion

There are other nifty debug visualizer related features in VS2015 but I find the ease of use and deployment to be the real game changer.

Now when I get to look at big vector of Customers without needed to expend and find what I want:

image

As simple as that.

Happy coding (Even in C++)…

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Topics:
performance ,debugging ,c++ ,vs2015 ,visual studio

Published at DZone with permission of Dror Helper, DZone MVB. See the original article here.

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