regstr

English / 日本語

Sample WinDbg command & UI extensions.

Features

• regstr command extension: If a register value can be interpreted as an ASCII string, it also displays that string
• RegStr UI extension: Displays register values and strings in the RegStr tool window according to the execution state
• Command Viewer UI extension: A command execution window that updates on every step. Supports history and highlighting differences in command output

Test environment

• Windows 11
• WinDbg 1.2601.12001.0
• Windows SDK 10.0.26100.7627
• Visual Studio 2026 18.3.2

Usage

Installation

Command extension

Note: Only supports debugging x64 applications.

Note: regstr_c.dll, regstr_cpp.dll, regstr_cpp2.dll, and regstr_rs.dll have different implementations, but all provide the same functionality. If you use them, use only one of them.

1. Download and extract the prebuilt zip from the Releases page
2. Launch WinDbg, debug any x64 application, and load the DLL with .load <absolute path to the DLL>. The DLL is one of regstr_*.dll
3. Confirm that the !regstr command is available

If you want it to be loaded automatically at startup, copy the entire UserExtensions folder to %LOCALAPPDATA%\DBG\.

UI extension

Note: Operation is not guaranteed on WinDbg versions other than the one listed above.

RegStr:

Note: Only supports debugging x64 applications.

1. Download and extract the prebuilt zip from the Releases page
2. Create a UIExtensions folder under %LOCALAPPDATA%\DBG, and place RegStr.dll inside it
3. When you start WinDbg, a Register string tab will be added. Click the Register string button inside it to open the RegStr window
4. Debug any x64 application, and register information will be displayed in the RegStr window

Command Viewer:

1. Download and extract the prebuilt zip from the Releases page
2. Create a UIExtensions folder under %LOCALAPPDATA%\DBG, and place CommandViewer.dll and DiffPlex.dll inside it
3. When you start WinDbg, a Command viewer button will be added to the View tab. Click it to open the Command Viewer window
4. Debug any application and enter any command into the text box at the top; the command output will be displayed

Build

Building the C version:

1. Open c\regstr.slnx in Visual Studio
2. Copy engextcpp.cpp and engextcpp.hpp from %PROGRAMFILES(X86)%\Windows Kits\<version>\Debuggers\inc, and modify them so they can be compiled
3. Build (this produces regstr_c.dll, regstr_cpp.dll, and regstr_cpp2.dll)

Building the Rust version:

1. Command extension: In the rust folder, run cargo build --release (this produces regstr_rs.dll)

Building RegStr:

1. Open ui\RegStr\RegStr.slnx in Visual Studio
2. Build (this produces RegStr.dll)

Building Command Viewer:

1. Open ui\CommandViewer\CommandViewer.slnx in Visual Studio
2. Build (this produces CommandViewer.dll)

References

For implementation details, please refer to our blog post How to implement WinDbg extensions (in Japanese) Part 1 - Command Extension, Part 2 (coming soon), Part 3 (coming soon).

LICENSE

Apache License, Version 2.0