How to visualise a simple std::string with natvis?

Question

I can't have a decent view of a basic std:string in VS2015 while debugging. I followed the instructions given at this address : https://msdn.microsoft.com/fr-fr/library/jj620914.aspx (that is debugger type set to native mode, and uncheck both Use Managed Compatibility Mode and Use Native Compatibility Mode ) . I have also added the stl.nativs file to my solution.

Currently my debugger looks like :

I would like to see as a value directly "test" for my variable str (instead of a very complex tree). Can you help me with this ?

Answer 1

I find the answer, for a very strange reason the stl.natvis file that I found in my VS Installation directory ( C:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\Common7\\Packages\\Debugger\\Visualizers for me ) and that I have added to my project is not recognised by the debugger automatically.

So the solution was to add another Debugger visualization file (.natvis) to my solution (right click ->add new item ) and to copy/past the content of the stl.natvis file to this new file. After rebuild, the standard std:string is appropriately displayed by the debugger.

For completeness, see below the part of the stl.natvis that deals with std::string for visual studio 2015.

<!-- VC 2015 -->
  <Type Name="std::basic_string&lt;char,*&gt;">
    <DisplayString Condition="_Mypair._Myval2._Myres &lt; _Mypair._Myval2._BUF_SIZE">{_Mypair._Myval2._Bx._Buf,na}</DisplayString>
    <DisplayString Condition="_Mypair._Myval2._Myres &gt;= _Mypair._Myval2._BUF_SIZE">{_Mypair._Myval2._Bx._Ptr,na}</DisplayString>
    <StringView Condition="_Mypair._Myval2._Myres &lt; _Mypair._Myval2._BUF_SIZE">_Mypair._Myval2._Bx._Buf,na</StringView>
    <StringView Condition="_Mypair._Myval2._Myres &gt;= _Mypair._Myval2._BUF_SIZE">_Mypair._Myval2._Bx._Ptr,na</StringView>
    <Expand>
      <Item Name="[size]" ExcludeView="simple">_Mypair._Myval2._Mysize</Item>
      <Item Name="[capacity]" ExcludeView="simple">_Mypair._Myval2._Myres</Item>
      <Item Name="[allocator]" ExcludeView="simple">_Mypair</Item>
      <ArrayItems>
        <Size>_Mypair._Myval2._Mysize</Size>
        <ValuePointer Condition="_Mypair._Myval2._Myres &lt; _Mypair._Myval2._BUF_SIZE">_Mypair._Myval2._Bx._Buf</ValuePointer>
        <ValuePointer Condition="_Mypair._Myval2._Myres &gt;= _Mypair._Myval2._BUF_SIZE">_Mypair._Myval2._Bx._Ptr</ValuePointer>
      </ArrayItems>
    </Expand>
  </Type>

  <!-- VC 2015 -->
  <Type Name="std::basic_string&lt;wchar_t,*&gt;">
    <AlternativeType Name="std::basic_string&lt;unsigned short,*&gt;" />
    <AlternativeType Name="std::basic_string&lt;char16_t,*&gt;" />
    <DisplayString Condition="_Mypair._Myval2._Myres &lt; _Mypair._Myval2._BUF_SIZE">{_Mypair._Myval2._Bx._Buf,su}</DisplayString>
    <DisplayString Condition="_Mypair._Myval2._Myres &gt;= _Mypair._Myval2._BUF_SIZE">{_Mypair._Myval2._Bx._Ptr,su}</DisplayString>
    <StringView Condition="_Mypair._Myval2._Myres &lt; _Mypair._Myval2._BUF_SIZE">_Mypair._Myval2._Bx._Buf,su</StringView>
    <StringView Condition="_Mypair._Myval2._Myres &gt;= _Mypair._Myval2._BUF_SIZE">_Mypair._Myval2._Bx._Ptr,su</StringView>
    <Expand>
      <Item Name="[size]" ExcludeView="simple">_Mypair._Myval2._Mysize</Item>
      <Item Name="[capacity]" ExcludeView="simple">_Mypair._Myval2._Myres</Item>
      <Item Name="[allocator]" ExcludeView="simple">_Mypair</Item>
      <ArrayItems>
        <Size>_Mypair._Myval2._Mysize</Size>
        <ValuePointer Condition="_Mypair._Myval2._Myres &lt; _Mypair._Myval2._BUF_SIZE">_Mypair._Myval2._Bx._Buf</ValuePointer>
        <ValuePointer Condition="_Mypair._Myval2._Myres &gt;= _Mypair._Myval2._BUF_SIZE">_Mypair._Myval2._Bx._Ptr</ValuePointer>
      </ArrayItems>
    </Expand>
  </Type>

  <Type Name="std::basic_string&lt;char32_t,*&gt;">
    <DisplayString Condition="_Mypair._Myval2._Myres &lt; _Mypair._Myval2._BUF_SIZE">{_Mypair._Myval2._Bx._Buf,s32}</DisplayString>
    <DisplayString Condition="_Mypair._Myval2._Myres &gt;= _Mypair._Myval2._BUF_SIZE">{_Mypair._Myval2._Bx._Ptr,s32}</DisplayString>
    <StringView Condition="_Mypair._Myval2._Myres &lt; _Mypair._Myval2._BUF_SIZE">_Mypair._Myval2._Bx._Buf,s32</StringView>
    <StringView Condition="_Mypair._Myval2._Myres &gt;= _Mypair._Myval2._BUF_SIZE">_Mypair._Myval2._Bx._Ptr,s32</StringView>
    <Expand>
      <Item Name="[size]" ExcludeView="simple">_Mypair._Myval2._Mysize</Item>
      <Item Name="[capacity]" ExcludeView="simple">_Mypair._Myval2._Myres</Item>
      <Item Name="[allocator]" ExcludeView="simple">_Mypair</Item>
      <ArrayItems>
        <Size>_Mypair._Myval2._Mysize</Size>
        <ValuePointer Condition="_Mypair._Myval2._Myres &lt; _Mypair._Myval2._BUF_SIZE">_Mypair._Myval2._Bx._Buf</ValuePointer>
        <ValuePointer Condition="_Mypair._Myval2._Myres &gt;= _Mypair._Myval2._BUF_SIZE">_Mypair._Myval2._Bx._Ptr</ValuePointer>
      </ArrayItems>
    </Expand>
  </Type>

---

Edit

See below the final watch console : (also please note that you should only copy part of the stl.natvis that you want, it seems that a full copy/past does not work.)

Answer 2

i find that the langauge you select in VS will impact this. the .natvis xml file's schema is definited in $(VSINSTALLDIR)/xml/schemas/$(LANG)/natvis.xsd, in my computer there are two version: 1033 and 2052, and the later one is newer than the other, it has much more elements definited(such as <SmartPointerUsage> which is used in the stl.nativs). if you find your debugger's variable inspection doesn't work, you may try to change the language to an special one which has a newer natvis.xsd.