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Pernosco
Company blog · pernos.co/blog · on HN as rocaprogrammingsystems
Pernosco is the company blog at pernos.co, writing about programming and systems. Since 2019, 29 different Hacker News readers have linked it 90 times, most often “Pernosco: Fast, Fun, Omniscient Debugging”. It is still writing: the last post was on 2025-01-27, and you can follow it by feed.
Sometimes recommended · 9 of 40 sampled comments recommend it?
Why HN links it
HN readers link pernos.co for Pernosco, a commercial time-travel debugger built on Mozilla's rr, with About pages, design posts and demos. Commenters mostly discuss the tool rather than the writing.
Summarised by Claude from a sample of 40 HN comments that link here. Each comment is marked recommending, critical or neutral (citing without judging); how this works.
Most-linked posts?
- Pernosco: Fast, Fun, Omniscient Debugging19 people · 29 mentions · first linked 2019-10-25
- Pernosco: Fast, Fun, Omniscient Debugging4 people · 9 mentions · first linked 2019-10-25
- /about/expressions/2 people · 5 mentions · first linked 2021-04-27
- /debug/e9UFXkGq__8KQB-N6n59lA/index.html2 people · 4 mentions · first linked 2019-11-27
- /about/javascript/2 people · 2 mentions · first linked 2021-04-27
- Fast, Fun, Omniscient Debugging2 people · 2 mentions · first linked 2021-03-29
- /about2 people · 2 mentions · first linked 2019-11-28
What Hacker News says?
To me this is very reminiscent of time travel debugging tools like the one used for Firefox’s C++ code, rr / Pernosco: https://pernos.co/
Comment linking /
on “Is something bugging you?”Submitted Where should the debugger set a breakpoint? as a story · 101 points
HN discussionWe have explored that sort of debugging/visualization tool in https://pernos.co . We built it before the age of genAI, but I think for coming up with powerful visualizations AI is neither necessary nor (yet) sufficient.
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on “Enough AI copilots, we need AI HUDs”Submitted Pernosco: Fast, Fun, Omniscient Debugging as a story · 99 points
HN discussionIf you use https://pernos.co/ then you don't need any of this, but I have a set of only slightly buggy gdbinit scripts that extend the rr debugging experience at < https://github.com/hotsphink/sfink-tools >. The main things it adds are: 1. a `log` command that just records whatever you give it into a plaintext file, together with its "point in time" according to rr. This is useful because when using rr, you tend to…
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on “What rr does”Submitted Pernosco Omniscient Debugger is now available for individual developers as a story · 62 points
HN discussionrr is a superpower, but pernosco is several superpowers ( https://pernos.co/; it’s built on rr). I recommend both!
Comment linking /;
on “What rr does”Submitted Structured Identifiers as a story · 43 points
HN discussionI mentioned this in a different thread, but I'd recommend you take a look at Pernosco, a debugging tool written by the original author of rr: https://pernos.co/about/callees/
Comment linking /about/callees/
on “Show HN: Time travel debugger for web development”Submitted Pernosco System Debuginfo as a story · 3 points
HN discussionI haven't personally used Replay, but from my experience using rr (a native debugger that also provides time-traveling features) being able to replay execution both backwards and forwards in time on a whim is amazing . These tools excel at diagnosing bugs that are hard to reproduce, because you only have to reproduce the bug once under the debugger and then you can endlessly replay that execution until you figure it…
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on “Show HN: Time travel debugger for web development”Submitted Tackling the C++ debugging UI nightmare with Pernosco as a story · 2 points
HN discussionFullscreen isn't just for video though. It's very commonly used for games. I also wrote fullscreen support for "DOM videos" (e.g. https://pernos.co/about/overview/ ) using the fullscreen API. The latter doesn't even support Webkit because the compatibility work was just too hard.
Comment linking /about/overview/
on “Porting Firefox to Apple Silicon”Submitted New features in Linux 6.10 contributed by Pernosco as a story · 2 points
HN discussionOne argument made for unit testing which this post doesn't address is that it's easier to understand and debug unit test failures. To which I say: yes it is, but quality debugging tools (which don't exist in many domains, and aren't used nearly as much as they could be where they do exist) can mitigate this issue. I'm talking about tools like https://rr-project.org and (self-promoting!) https://pernos.co .
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on “Unit Testing Is Overrated”Submitted Pernosco: Fast, Fun, Omniscient Debugging as a story · 2 points
HN discussionDebuggers are very specific tools, and I've never really liked them. Basically, you get a tiny view of what your code is doing, and have to slowly build a mental model of what's going on through time. I have found that prints and code reading (in a good IDE which is able to track variable references!) are often enough, and usually faster,for the kind of software I write. Now, things are getting better: mozilla's RR…
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on “Developer tools can be magic but instead collect dust”Submitted The Pernosco vision: Omniscient-mode debugging (2020) as a story · 2 points
HN discussionYou might be interested in Pernosco: see https://pernos.co/about/overview/ and its related content. We agree with your critique of traditional debuggers and Pernosco tackles that "temporal visibility" problem head on.
Comment linking /about/overview/
on “Icecream: Never use print() to debug again in Python”Submitted Gha-runner, a Rust crate for running GitHub Actions locally (or elsewhere) as a story · 2 points
HN discussionWe have a 170K line project written in Rust ( https://pernos.co ). I've written a lot of C++ in the past, but also Java and other things (I've been programming for nearly 40 years now), so I'm familiar in developing with and without GC. Pernosco is mostly a server app that could use GC. I'm happy with the choice of Rust. > And the amount of complexity in the language just to avoid that is truly staggering. In terms…
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on “Linux kernel in-tree Rust support”Submitted Fast, Fun, Omniscient Debugging as a story · 2 points
HN discussionI literally (as in 30 minutes ago) just fixed a bug in 10 minutes that I thought was going to take me 3 days to fix using https://pernos.co/ (a "timeless" debugging tool that wraps Mozilla's `rr`). This is a factor of speedup on the order of 100x+, not 10x. I highly recommend checking this tool out if you value your time.
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on “Ask HN: What are some “10x” software product innovations you have experienced?”Submitted Pernosco – new kind of x86 debugger as a story · 1 points
HN discussionThe rr debugger [1]. I desperately missed it after switching to a mac laptop -- to the point that I now have an older linux system which exists primarily to run rr. (I've heard that Pernosco [2] - partly built on rr, AFAIK - is even more revolutionary, but haven't yet tried it myself) [1] https://rr-project.org/ [2] https://pernos.co/
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on “Ask HN: What are some “10x” software product innovations you have experienced?”Submitted Shrink Your Compile Times with Split Dwarf as a story · 1 points
HN discussionSee also https://pernos.co/ which is based on rr but adds a queryable database of the whole program execution, which allows you to do things like this: > [...] just click on the incorrect value. With full program history Pernosco can immediately explain where this value came from. The value is tracked backwards through events such as memcpys or moves in and out of registers until we reach a point where the value "or…
Comment linking /examples/race-condition
on “rr – record and replay debugger for C/C++”Submitted Pernosco: Fast, Fun, Omniscient Debugging as a story · 1 points
HN discussionYou might be interested in the rather spectacular upgrade to it, called pernosco : https://pernos.co/ It’s based on rr ( same author ) but vastly better
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on “rr – record and replay debugger for C/C++”You're probably remembering https://pernos.co/blog/tzcnt-portability/
Comment linking /blog/tzcnt-portability/
on “Everything Is Broken: Shipping Rust-Minidump at Mozilla”
