Greg Law

Time-Traveling Through Spark: Recording Distributed Failures Across Space and Time @david.griffiths_96143/time-traveling-through-spark-recording-distributed-failures-across-space-and-time-084cf9530cbe" target="_blank" rel="nofollow noopener">medium.com/@david.griffit…

Latest on memory safety: "The new US administration has removed everything from the White House web site and fired most of the CISA people who worked on memory safety." tbf, memory safety is pretty woke. hubs.ly/Q038Yn1h0

Might want to watch the video at 2x, just because we ran it on a regular laptop. Recording didn't noticeably slow it down at all.

We recorded Deepseek! Obviously this won't tell you how it was made, but very cool for seeing how it works. The only sad bit was that it doesn't seem to know about time travel debugging. youtube.com/watch?v=h-fJqX…

@oogie_fletzet @ID_AA_Carmack I've never written a line of JS in my life, so haven't had an opportunity to use replay.io, but as a C programmer, I find rr-project.org to undo.io be exactly what you're asking for: very simple, and very powerful.

@gregthelaw @ID_AA_Carmack Nice, but this is very browser/JS/React specific and also makes the mistake of trying to outsmart the developer We need dumb tools to do smart work, not the other way around

I am always bemused by programmers that don’t use debuggers. It isn’t just about breakpoints and examining variables, but also being able to break into a process that has been running for an hour and issue something like: (observation_ring*255).to(dtype=torch.uint8).view(128,16,4,3,128,128).permute(1,0,2,4,5,3).cpu().numpy().tofile('results/ring_128x128.rgb')

@oogie_fletzet @ID_AA_Carmack See undo.io, replay.io, rr-project.org

@ID_AA_Carmack I agree, but we also lack good tooling around observability and breakpoints. Debuggers have not evolved much since their initial introduction and are quickly becoming irrelevant

I'm going to respectfully disagree. I used to use debuggers more than I do now - I was enough of a fan of them that I wrote the Grand Universal Debugger control mode in Emacs. In recent decades my preferences have changed. I use debuggers less and extensive debug logging more. That's an investment in the ability to troubleshoot future problems that often gains value over time. What might get me back into them is time-reversal debuggers. Those sound interesting, but I haven't actually used one yet.

@esrtweet @ID_AA_Carmack Yes! Time travelling debuggers change everything. I've been working on Undo.io for nearly 20 years, finally the approach is getting mainstream adoption. @esrtweet DM me and I'll give you a lifetime free license to undo.io. Works well with GUD, too!

@ID_AA_Carmack Time travel debugging is a game changer. rr-project.org, undo.io replay.io or learn.microsoft.com/en-us/windows-…

We have just released a new C++Now 2024 Conference Video! How do Time Travel Debuggers Work? - Design and Implementation of a Time Travel Debugger - by @gregthelaw youtu.be/NiGzdv84iDE #Cplusplus #Cpp #Debugging #Programming #Softwareengineering

How do Time Travel Debuggers Work? - Design and Implementation of a Time Travel Debugger - by @gregthelaw youtu.be/NiGzdv84iDE #Cplusplus #Cpp #Debugging #Programming #Softwareengineering

💡#cpp debugging top tip: Finding unexpected values in your variables? The 𝚕𝚊𝚜𝚝 command in Undo allows you to rewind directly back to the last time that value was changed, and find out exactly where that bad value came from. hubs.ly/Q02V49-80 #cplusplus

How do Time Travel Debuggers Work? - Design and Implementation of a Time Travel Debugger - by @gregthelaw youtu.be/NiGzdv84iDE #Cplusplus #Cpp #Debugging #Programming #Softwareengineering

Debugging Your Hardest C++ Bugs With Time Travel Debugging from Undo - by @gregthelaw - C++Online 2024 youtube.com/watch?v=R6QQT8… #Cpp #Gdb #Linux #Programming #Tooling #cpponline

My friend Aditya Gurajada and I created a lightweight logging library (L3). Compared to standard printf debugging, L3 is much faster & lock-free -- 2ns per log message compared to > 50ns for a regular, buffered fprintf(). You can get it from github here: hubs.ly/Q02PZdlB0

CppCon 2024 SESSION ANNOUNCEMENT: Back to Basics: Debugging and Testing by @gregthelaw & @MichaelShah cppcon2024.sched.com/event/1gZej/ba… Register now: cppcon.org/registration/ #cpp #cplusplus #programming #debugging

CppCon 2024 SESSION ANNOUNCEMENT: Back to Basics: Debugging and Testing by @gregthelaw & @MichaelShah cppcon2024.sched.com/event/1gZej/ba… Register now: cppcon.org/registration/ #cpp #cplusplus #programming #debugging

A wrote a book on how debuggers work! It guides you through writing a complete native debugger from scratch. Available Spring 2025 from @nostarch (probably not with this cover)

The CrowdStrike outage was super high profile, but this problem happens all the time: unsanitized input causes code to crash. Fuzzing is a good way to find these problems before your customer does (or in this case the whole world does). Ref. odbms.org/2023/08/on-deb…

CrowdStrike effectively bricked windows, Mac and Linux today. Windows machines won’t boot, and Mac and Linux work is abandoned because all their users are on twitter making memes. Incredible work.