CEO Interview with Dr Greg Law of Undo

Greg Law is a C++ debugging expert, well-known conference speaker, and the founder of Undo. Greg has over 20 years’ experience in the software industry working for the pioneering British computer firm Acorn, as well as NexWave and Solarflare.

Determined to build a tool to ease the pain of debugging complex software, he started his company Undo from his garden shed. Now the company is established as the time travel debugging company for Linux. He lives in Cambridge, UK with his wife and two children; and in his spare time, he likes to code and create free C/C++ debugging tutorial videos to share on Undo’s free resource center: https://undo.io/resources/gdb-watchpoint 

Tell us about your company

Undo provides advanced debugging technology that helps engineers solve the most complex software issues in semiconductor design, EDA tools, networking, and other at-scale mission-critical environments. Our solutions are trusted by engineers at top technology companies worldwide to accelerate debugging — enabling them to boost engineering productivity and get to market faster.

What problems are you solving

Most of the world’s software is not really understood by anyone. It goes wrong, and no-one knows why. Often people don’t even know why or how it works!

At Undo we allow software engineers to see exactly what their code did and why. This allows them to easily root-cause even the most difficult issues. We also allow better collaboration between and within teams. Our technology records program execution in full detail, enabling developers to replay and analyze exactly how an issue occurred — eliminating guesswork and dramatically accelerating root-cause analysis. By making debugging deterministic and shareable, we also improve collaboration within engineering teams, reducing time wasted on reproducing issues and miscommunication

What application areas are your strongest?

Any industry dealing with millions of lines of mission-critical code — where a single bug can cost millions — benefits from Undo’s ability to provide precise, replayable debugging insights. Undo is strongest in industries where software complexity, reliability, and debugging efficiency are critical. Our technology is widely used in:

• EDA / Computational Software – Engineers rely on Undo to debug intricate design and verification tools, ensuring semiconductor development stays on schedule and resolving customer issues faster.
• Semiconductor design – Undo enables semiconductor companies to debug complex multithreaded applications efficiently.
• Databases – Our time travel debugging solution helps engineers building complex multithreaded data management systems to resolve hard-to-reproduce issues.
• Networking – We assist in diagnosing failures in networking operating systems as well as routers/switches, where intermittent issues and concurrency bugs are notoriously difficult to debug.
• Financial technology – Undo is used in trading platforms and risk management systems, where milliseconds matter and reliability is paramount.

What keeps your customers up at night?

Our customers sleep soundly! But before they become a customer, they face some serious challenges that keep them up at night:

• Development bottlenecks – Their engineering teams are stuck in a debugging tarpit, spending days or weeks diagnosing elusive issues instead of shipping new features.
• Missed deadlines – Product releases slip because debugging complex systems is slow and unpredictable.
• Production failures – Bugs escape into production, causing costly downtime, reputational damage, and support escalations.
• Incomplete coverage – In design and verification, incomplete modelling and insufficient test coverage increase the risk that a fabricated chip won’t perform as expected under real workloads. A mistake at this stage can be a multi-million-dollar disaster — or worse, require a complete respin.

Undo removes the guesswork, enabling teams to diagnose issues quickly and confidently — so they can focus on delivering high-performance, reliable software and hardware on schedule.

What does the competitive landscape look like and how do you differentiate?

Our main competition remains old-fashioned printf debugging, maybe a bit of GDB. Most engineers are still using tools and techniques that require them to guess what happened, recompile, rerun, and hope the bug reappears. Unlike printf-based debugging, the engineer can ask questions about their program’s behavior without recompiling and rerunning.

Compared to GDB, Undo tells you about the past, exactly what happened – past tense. There are a few open-source projects trying to offer similar capabilities, but they don’t scale to the size or complexity of the systems our customers work on. Time travel debugging at enterprise scale is a hard problem. We’ve spent over a decade making it reliable, fast, and usable for real-world software teams.

What new features/technology are you working on?

A lot! One interesting thing is to generate waveform views (e.g. a vcd file) from a recording. This is particularly valuable for silicon engineers using SystemC or writing C++ models. It lets them analyse software behavior in the familiar, signal-level style they’re used to from RTL simulation.

One of SystemC’s big advantages is that you can compile and run your model like regular C++, without needing a heavyweight simulator. Undo builds on that: you keep the simplicity and speed of native execution, without giving up waveforms or the power of time travel debugging. It’s the best of both worlds.

How do customers normally engage with your company?

Our customers typically engage with Undo by testing it on real-world debugging challenges. A common approach is to take a past issue — one that was exceptionally painful to diagnose — back out the fix, and then re-run the debugging process using Undo. This allows them to directly compare the traditional approach with Undo’s time travel debugging, highlighting the drastic reduction in time and effort required to find the root cause.

Once they see how much easier debugging can be, they apply Undo to an unsolved, high-priority issue. The ability to instantly replay program execution and see exactly what happened — without relying on logs or guesswork — proves so effective that teams quickly adopt Undo as a standard debugging tool across their organization.

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