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Some advanced debugging techniques for Visual Studio 2015



  • Create custom visualization of data
  • Complex definitions possible
  • .natvis files are stored in Visual Studio project (even in pdb)
// 01_visualizers / main.cpp
#include <string>
#include <memory>

struct Circle {
    double cx, cy, r;

struct Container {
    std::shared_ptr<Circle> c1, c2;
    Container(std::shared_ptr<Circle> c1,
              std::shared_ptr<Circle> c2)
        : c1(c1), c2(c2) {};

int main() {
    auto c1 = std::shared_ptr<Circle>(
        new Circle{100.0, 200.0, 10.0});
    auto c2 = std::shared_ptr<Circle>(
        new Circle{144.0, 222.0, -33.0});
    auto container = std::make_shared<Container>(
        c1, c2);
    // watch container with .natvis visualizer


  • Add to project:
    Add / New Item / Visual C++ / Utility / Debugger visualization file (.natvis).
    Alternative: Store in %USERPROFILE%\Documents\Visual Studio 2015\Visualizers
  • Enable Natvis diagnostics:
    Tools / Options / Debugging / Output Window / Natvis diagnostic messages (C++ only) option.The errors are displayed in the Output window.
  • MSDN: Creating custom views of native objects in the debugger
  • MSDN:Format Specifiers in C++

Example .natvis

<?xml version="1.0" encoding="utf-8"?>
<AutoVisualizer xmlns="">
  <Type Name="std::shared_ptr&lt;Container&gt;">
    <DisplayString>{_Ptr->c1,g}, {_Ptr->c2,g} (d2={(((_Ptr->c1._Ptr->cx-_Ptr->c2._Ptr->cx) * (_Ptr->c1._Ptr->cx-_Ptr->c2._Ptr->cx) + (_Ptr->c1._Ptr->cy-_Ptr->c2._Ptr->cy) * (_Ptr->c1._Ptr->cy-_Ptr->c2._Ptr->cy))),g})</DisplayString>
  <Type Name="std::shared_ptr&lt;Circle&gt;">
    <DisplayString Condition="_Ptr->r &lt; 0">(cx={_Ptr->cx,g}, cy={_Ptr->cy,g}, r={_Ptr->r,g} (INVALID))</DisplayString>
    <DisplayString>(cx={_Ptr->cx,g}, cy={_Ptr->cy,g}, r={_Ptr->r,g})</DisplayString>


  • Useful to skip stepping into uninteressting calls
  • Do not skip too much. For example
// 02_stepfilters / main.cpp
#include <string>

struct MyWidget {
  MyWidget(const char* s) {}

void setNameWidget(const std::string& name, const MyWidget& w) {
  /* TODO: Debug me */

int main()
  const char* name = "myName";
  /* Debugging task: Step into setNameWidget()
   * typical sequence: F11, Shift+F11, F11, Shift+F11, F11
   * use step filter in
   * %USERPROFILE%\Documents\Visual Studio 2015\Visualizers\example.natstepfilter
   * to avoid stepping into std::string ctor and MyWidget ctor.
  setNameWidget("bla", "widgetName");


  • Must be saved in
    "%USERPROFILE%\Documents\Visual Studio 2015\Visualizers\example.natstepfilter"
    (not per-project)
  • MSDN: Just My Code


  • Execute a function of the process from debugger
  • To execute
    , go to Command window:
    ? pt(args)
  • Or: Use watch window. Expression/function call is not evaluated automatically on debugger breaks. Add e.g. a space at the end and press enter.
// 03_eval / main.cpp
#include <iostream>
#include <string>
#include "halconcpp/HalconCpp.h"

std::string __buffer;
/* to be called via Debug.EvaluateStatement or ? */
const char* pt(const HalconCpp::HTuple& t) {
  std::cout << t.ToString().Text() << '\n';
  __buffer = t.ToString().Text();
  return __buffer.c_str();

int main()
  auto bc = HalconCpp::HBarCode(HalconCpp::HTuple(),HalconCpp::HTuple());
  HalconCpp::HImage Image("barcode/ean13/ean1308.png");
  HalconCpp::HTuple DecodedString;

  bc.FindBarCode(Image, "EAN-13", &DecodedString);
  /* Contents of HALCON tuple DecodedString not
   * visible (pimpl). Call embedded function pt
   * to display string in VS Command Window:
   *   ? pt(DecodedString)  */

Piecewise execution of a statement

  • ALT + 8 -> Assembler view
  • Step through assembler code. Function calls should be clearly visible, even to developer that don't know how to read assembler code.
// 04_step_statement / main.cpp
#include <iostream>
#include <string>

#include "halconcpp/HalconCpp.h"

int main()
    HalconCpp::HTuple Rand;
    HalconCpp::TupleRand(5, &Rand);
    /* ... */
    /* Execute [] first, then L().
     * Where does exception occur?
     * Use ALT+8 to go to assembler view */
    auto l = Rand[2].L(); // HTupleAccessException!

Attach debugger automatically

  • Some applications start themselves in multiple processes
    • Chrome
    • NodeJS
    • clang
    • ...
  • Debugging of events at program start is difficult
  • Windows can attach Visual Studio Just-In-Time debugger automatically when a process is started
  • (maybe alternatively, use gflags.exe, part of the Windows 10 SDK).

Attach debugger automatically

  • Open the Registry Editor
  • navigate to HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Image File Execution Options
  • Select the application you want to debug:
    • Either it already exists as subkey, then use that one
    • Or, you have to create a new key in Image File Execution Options with the name of the application (e.g. chrome.exe)
  • Create a new string value with name debugger and name vsjitdebugger.exe


VS2015 project available:
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