Inspecting STL containers in Visual Studio debugging

Question

If I have a std::vector or std::map variable, and I want to see the contents, it\'s a big pain to see the nth element while debugging. Is there a p

Answer 1

For vectors, this thread on the msdn forums has a code snippet for setting a watch on a vector index that might help.

Answer 2

To view the nth element of a container in the Visual Studio debugger, use:

container.operator[](n)

Answer 3

If you want to watch more than one element at the same time, you can append a comma and the number of elements as so:

(v._Myfirst)[startIndex], count

However, note that count must be a constant, it cannot be the result of another expression.

Answer 4

Most simply method is you have to ready a pointer to watch variable like this.

vector<int> a = { 0,1,2,3,4,5 };
int* ptr = &a[0]; // watch this ptr in VisualStudio Watch window like this "ptr,6".

I tried "a._Myfirst[0]" in VisualStudio2015, But It wasn't display array data.

If you can use "natvis", it will resolve your problems.

This is "sample.natvis" for display std::vector data for Visual studio 2015.

<?xml version="1.0" encoding="utf-8"?> 
<AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
  <Type Name="std::vector&lt;*&gt;">
    <DisplayString>{{ size={_Mypair._Myval2._Mylast - _Mypair._Myval2._Myfirst} }}</DisplayString>
    <Expand>
      <Item Name="[size]" ExcludeView="simple">_Mypair._Myval2._Mylast - _Mypair._Myval2._Myfirst</Item>
      <Item Name="[capacity]" ExcludeView="simple">_Mypair._Myval2._Myend - _Mypair._Myval2._Myfirst</Item>
      <ArrayItems>
        <Size>_Mypair._Myval2._Mylast - _Mypair._Myval2._Myfirst</Size>
        <ValuePointer>_Mypair._Myval2._Myfirst</ValuePointer>
      </ArrayItems>
    </Expand>
  </Type>
</AutoVisualizer>

Before

After