Category Archives: _Twitter Archive 🐤

The astonishing cost/benefit asymmetry of a four-day work week

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Work update: I reduced to working 4 days/week and the cost/benefit asymmetry is astonishing.

Just one extra free day might not sound like much, but I feel like I gain >100% more high quality free time (Friday off is even better than Saturday; Sunday is not high quality free time for me – too much adulting to do).

And I lose only 20% of my productive work capacity (Well a bit more; Friday would be a more productive day than average for me b/c it’s quieter & less meetings).

I’ve constantly felt squashed the last few years, but always convinced myself it was a me problem, rather than a possibility that even “normal” working hours didn’t actually leave me with enough free time for everything I had to do*. (Maybe some of both)

But my energy and mood are way better than in a long time, so maybe it goes to show that the latter was the case, and one extra day can go a long way. (But that’s less surprising when you frame it as 100% more time).

I do need to be a bit more conscious of how I use my work week, and I have noticed a tendency to try to fit 5 days of work into 4… but overall it’s going well. I’m curious if I end up filling up the extra personal capacity and end up just as stressed, but I somehow doubt that will happen.

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*You might ask, well why are you so busy anyway? Are you just piling on voluntary responsibilities?

I’ve thought about this at length and I think my answer is glibly, “expat life”.

Tip: When you’re learning a new programming language, look up prominent open source projects and copy their style

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Tip: When you’re learning a new programming language, look up prominent open source projects and copy their style.

Aside from the core language, there are many conventions & little details to learn: naming (variables, classes, files), file structuring, literal code formatting

These are things few blogs talk about because it’s highly opinionated. But nevertheless when you’re learning, you’ll benefit from at least some reference for these.

Find a few “professional” open source projects and browse to see what various interpretations of “professional style” are. Then pick one you like most.

Be careful of picking projects that are too old — they might use older style for consistency with legacy, even though they might ideally wish to modernize it.

And ideally pick projects whose contributors are experienced engineers who work on it full-time. Since they “live in” the codebase, they’re less likely to tolerate sloppiness – or are at least more invested in cleaning it up.

The last idea is influenced by @awesomekling, who talks about similar things in his classic “My top advice for programmers looking to improve” car-talk video =]

Personal projects are like free weights

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I thought of this 7 years ago and I still think it rings true. In my experience, school projects were tightly scoped and had things like a basic build system and boilerplate runnable code (e.g. main) already provided. Maybe even some tests. It trains a specific muscle in a certain way.

With personal projects, you do all of this yourself and incidentally also train the equivalent “stabilizer” muscles. Things like: making the repo, writing the main and boilerplate code, setting up unit tests, setting up CI, setting up dependencies and their management.

And in my experience, it’s all these “stabilizer” activities that define what it means to be a senior engineer. Junior engineers work within an existing project; senior engineers own the entire thing, including these “little” (critical) parts.

The point here isn’t to necessarily criticize CS education; there are good, practical reasons for setting up such project structure to ensure all students have a good experience, given the time constraints. The point is that students should be wary of not doing any personal projects at all throughout a CS education. Maybe it would be possible so students don’t have to do this in their free time, and build it into some kind of flexible course. I suppose this is the point of final capstone projects, but I think senior year is far too late to be doing this for the first time.

SerenityOS Day 1: Debugging the piano app

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I love spelunking into unknown codebases with nothing but find and grep. It’s one of the most valuable skills one can develop as a programmer imo and in this video you can see how I approach it.

This video focuses on debugging GUI event handling. At first the bug seemed related to the app’s waveform selection, but I then realized it was a more general topic with the SerenityOS GUI UX — selecting a dropdown entry retains focus, and requires an explicit escape key.

Ultimately I made progress accidentally by hitting the keyboard while the selection was still active, revealing to me that fact (which I hadn’t noticed before).

You can see my general debugging flow:

  • Get things building
  • How to run app from command line (to see stdout)?
  • How to print to stdout?
  • Using debug prints to understand the GUI event handling

Overall I’m quite impressed with SerenityOS. I only realized after looking into the code exactly how much code they had written and how fully featured the system is. Well done to the team.

Do you need to learn how to implement a red-black tree?

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Pitfalls with fork() in real-time contexts

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This thread went viral. The main takeaways:

  • After calling fork(), a parent process gets its entire address space write protected to facilitate COW. This causes page faults.
  • This makes fork() unsafe to call from anywhere in a process with realtime deadlines — including non realtime threads! Usually non RT can do what they want, but that is an interesting exception.
  • On modern glibc, system() doesn’t use fork(), it uses posix_spawn(). But is posix_spawn() safe from a non RT thread?
  • posix_spawn() doesn’t COW — the parent/child literally share memory — so the page fault issue doesn’t apply. However the parent is suspended to prevent races between the child and parent. This seems RT unsafe…
  • However, only the caller thread of the parent is suspended, meaning the RT threads are not suspended and continue running with no page faults.
  • So it is safe to use system() or posix_spawn() from a non RT thread.

Pick an impressive project, then checkout to the first commit

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A takeaway I often get from exploit writeups

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Can we have non-atomic std::shared_ptr in C++?

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Turns out, we do have them. libstdc++ contains a heuristic kludge where it checks if libpthread is linked into the process and conditionally executes an atomic add or non-atomic add depending on the result. Post 2020, it doesn’t directly use the libpthread hack, but uses glibc’s native support for this.

These kinds of things always make me sad about C++ (especially compared to how nice and clean things seem to be in Rust world), but at least it’s nice knowing that the committee did consider it and there are good reasons why to not have this in the C++ stdlib. The most compelling reason is that in the absence of a borrow checker, it is all too easy to silently use a non-atomic shared_ptr in multithreaded code.

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