- This project is not produced, endorsed, or monitored by the Windows debugger team. While the debugger team welcomes feedback about their API and front ends (windbg, kd, et al), they have no connection with this project. Do not file bugs or feedback to the debugger team concerning this project.
- This is not a funded project: it has no official resources allocated to it, and is only worked on by volunteers. Do not take any production dependency on this project unless you are willing to support it completely yourself. Feel free to file Issues and submit Pull Requests, but understand that with the limited volunteer resources, it may be a while before your submissions are handled.
- This is an experimental project: it is not fully baked, and you should expect breaking changes to be made often.
Corollary of above disclaimers: I would avoid attaching DbgShell to live targets of high value.
Have you ever tried automating anything in the debugger? (cdb/ntsd/kd/windbg) How did that go for you?
The main impetus for DbgShell is that it’s just waaaay too hard to automate anything in the debugger. There are facilities today to assist in automating the debugger, of course. But in my opinion they are not meeting people’s needs.
- Using the built-in scripting language is arcane, limited, difficult to get right, and difficult to get help with.
- DScript is kind of neat, but virtually unknown, and it lacks a REPL, and it’s too low-level.
- Writing a full-blown debugger extension DLL is very powerful, but it’s a significant investment—way too expensive for solving quick, “one-off” problems as you debug random, real-world problems. Despite the cost, there are a large number of debugger extensions in existence. I think there should not be nearly so many; I think the only reason there are so many is because there aren’t viable alternatives.
- Existing attempts at providing a better interface (such as PowerDbg) are based on “scraping” and text parsing, which is hugely limiting (not to mention idealogically annoying) and thus are not able to fulfill the promise of a truly better interface (they are only marginally better, at best).
- Existing attempts to provide an easier way to write a debugger extension are merely a stop-gap addressing the pain of developing a debugger extension; they don’t really solve the larger problem. (for instance, two major shortcomings are: they are still too low-level (you have to deal with the dbgeng COM API), and there’s no REPL)
The goal of the DbgShell project is to bring the goodness of the object-based PowerShell world to the debugging world. When you do ‘dt’ to dump an ‘object’, you should get an actual object. Scripting should be as easy as writing a PowerShell script.
The DbgShell project provides a PowerShell front-end for dbgeng.dll, including:
- a managed “object model” (usable from C# if you wished), which is higher-level than the dbgeng COM API,
- a PowerShell “navigation provider”, which exposes aspects of a debugging target as a hierarchical namespace (so you can “cd” to a particular thread, type “dir” to see the stack, “cd” into a frame, do another “dir” to see locals/registers/etc.),
- cmdlets for manipulating the target,
- a custom PowerShell host which allows better control of the debugger CLI experience, as well as providing features not available in the standard powershell.exe host (namely, support for text colorization using ANSI escape codes (a la ISO/IEC 6429))
The custom host is still a command-line (conhost.exe-based) program (analogous to ntsd/cdb/kd), but it can be invoked from windbg (
In addition to making automation much easier and more powerful, it will address other concerns as well, such as ease of use for people who don’t have to use the debuggers so often. (one complaint I’ve heard is that “when I end up needing to use windbg, I spend all my time in the .CHM”)
For seasoned windbg users, on the other hand, another goal is to make the transition as seamless as possible. So, for instance, the namespace provider is not the only way to access data; you can still use traditional commands like “
~3 s“, “
- Color: support for text colorization using ANSI escape codes (a la ISO/IEC 6429)
- Custom formatting engine: Don’t like .ps1xml stuff? Me neither. In addition to standard table, list, and custom views, you can define “single-line” views which are very handy for customizing symbol value displays.
- Custom symbol value conversion: For most variables, the default conversion and display are good. But sometimes, you’d like the debugger to do a little more work for you. The symbol value conversion feature allows, for instance, STL collection objects to be transformed into .NET collection objects that are much easier to deal with.
- Derived type detection: For when your variable is an IFoo, but the actual object is a FooImpl.
- Rich type information: exposed for your programmatic pleasure.
- Q: Does it work in WinDbg? I will only use WinDbg. A: Yes–load up the DbgShellExt.dll extension DLL, and then run “
!dbgshell” to pop open a DbgShell console.
- Getting Started with DbgShell
- Custom formatting engine
- Custom symbol value conversion
- Derived type detection
- Rich type information
- Hacking on DbgShell
You can find a short (3 minute) video introduction here: https://youtu.be/ynbg2zZ1Igc