A Future is a Suspending Scheduler


Introduction This is another blog post related to the Build Systems à la Carte paper. See Using type-classes to model the expressivity of build systems for the first one. The paper proposes splitting build systems into two components: Rebuilders decide when to rebuild a particular key (file). Schedulers decide how to rebuild multiple keys - handling dependencies while maintaining correctness and efficiency. Schedulers come in 3 flavors (see Section 4):…
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Getting to Deterministic Builds on Windows


(Disclaimer: Some of this post discusses projects from my job. All opinions and mistakes here are my own.) This is a set of notes on getting to deterministic builds in C, C++ and Rust on Windows. The primary motivation for this is not the lofty goal of a Reproducible Build, but simply improving our Bazel cache hit rates. A Quick primer on Bazel caching At Dropbox, much of our build is powered by Bazel and I was involved in making that a reality.…
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Ankle Fracture and Recovery


I suffered a right ankle fracture on March 16, 2020. This post chronicles the accident and recovery steps and will be updated periodically over the next few months. The Accident I was at the Bill Putnam (Fairy Meadows) Hut in British Columbia, Canada on a guided ski trip. On Day 3 of our trip, we traversed the Granite Glacier and did a couple of runs below the SW face of Mt.…
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Food for Thought: January - March 2020


Books, podcasts and articles that had a strong impact this quarter, grouped into themes. Amazon links are affiliate links. Feelings and free speech I finally worked my way through The Coddling of the American Mind (Lukianoff and Haidt) in January. This is a really fantastic book. It gives names and reasoning to things that have been floating around the American cultural landscape for years now. Particularly concerning to me is the fact that just as we have more vitriolic and far-reaching media – Twitter – we are lowering the bounds of offense and diluting the scope of safety.…
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Using type-classes to model the expressivity of build systems


I first came across the paper Build Systems à la Carte by Mokhov, Mitchell and Peyton Jones over an year ago. I’ve recently been re-reading it, this time working through all the details and trying to really understand it. I love that it is an extremely readable paper analyzing a practical aspect of software engineering. The twist: it uses Haskell, using its properties to impose strong proofs on certain aspects of the build.…
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Using 1Password with ssh-agent on Linux


I run the dev channel of ChromeOS. This crashes occasionally. While my chrome tabs are generally recovered, it also resets the crostini containers. Every time this happens, I’ve to launch 1Password (the android app), unlock it, search for my SSH key, copy the password and finally paste it in the terminal. This was starting to get old. A couple of days ago I spent about an hour short circuiting this.…
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Saving Chrome Tabs to Dropbox


tl;dr: Save My Tabs is a Chrome extension to save the list of open tabs to Dropbox. I’ve a weird browser usage pattern due to hardware choices. On two of my devices (work laptop, iPhone), I use Firefox. My personal laptop is a Pixelbook. While it is possible to use Firefox on ChromeOS within Crostini, the experience is pretty abysmal compared to using Chrome. This kept leading to an annoying situation where I couldn’t access tabs open in Chrome on my other devices.…
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Library Design Gotchas: Configuration loading


A friend was complaining about this library they were trying to use that was failing to load a configuration from a file. The resulting dive into the code inspired this post about inappropriate choices made when designing how a library is configured. It isn’t my intention to pick on pyart. I appreciate the hard work the developers did to create it and open source it. It is just the example at hand.…
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Retrieving function arguments while unwinding the stack


When a debugger, profiler or crash reporter is unwinding the call stack, can it reliably retrieve the function arguments of every function in the stack? I originally intended for this to be a later part of the Sampling Profilers series, but a recent discussion with Ben Frederickson, and his subsequent py-spy implementation helped crystallize my thoughts and I figured I’d write it down separately. Retrieving function arguments is “trivial” in certain cases and pure guesswork in others.…
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Sampling Profiler Internals: Suspending Threads


This is part 2 of the Sampling Profilers Internals series. Introduction Suspending threads Stack unwinding Symbolication Presenting profile output Extending the profiler to managed languages As described in the introduction, a sampling profiler captures the stack of each thread every few milliseconds. To do this, it is preferable to suspend the thread 1. We don’t want the stack changing under us as we are profiling.…
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