blogsystem5 - Julio Merino (jmmv.dev)

Porting the EndBASIC console to an LCD

Hello again Blog System/5 and sorry for the radio silence for the last couple of months. I had been writing too much in here and neglecting my side projects so I needed to get back to them. And now that I’ve made significant progress on cool new features for EndBASIC, it’s time to write about them a little! One of the defining characteristics of EndBASIC is its hybrid console: what looks like a simple text terminal at first glance can actually render overlapping graphics and text at the same time.

April 26, 2024 · Tags: blogsystem5, endbasic, rust
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How "new type" helps avoid production outages

My January links recap included the “Phantom Types” article by David Soria Parra. In it, the author briefly touches upon the “new type” idiom, its typical implementation in Rust, and then proceeds to propose a better alternative. But the question arises: why should you care? To answer why this idiom is useful, I want to present you with a real production problem we faced in the Storage Infrastructure team at Google circa 2010.

March 9, 2024 · Tags: blogsystem5, rust, sre, twitter-thread
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Links: February 2024 edition

Hi folks! Another month has passed so it’s time for a brief recap of the main news, articles, and projects that made the rounds during this period and are on topic for Blog System/5. As usual, this is not just a list: every entry is accompanied by a short blurb detailing why I found the content interesting, which is meant to nudge you into reading it! Also, the list is ordered by when the links made it my way, not chronologically, and some items are not from this time period.

February 29, 2024 · Tags: blogsystem5, recap
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To C or not to C

Over the last few days, there has been this… debate over at Twitter sparked by a claim that you cannot be a good programmer without knowing C. You obviously can be one, but there is some nuance in what “knowing” C is truly about. Here is my take on the matter. Let me repeat this first: of course you can be a perfectly good programmer without knowing C. Knowing a language doesn’t make or break a programmer, and there are great programmers out there that don’t touch C.

February 21, 2024 · Tags: blogsystem5, opinion, programming, twitter-thread
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Running GNU on DOS with DJGPP

The recent deep dive into the IDEs of the DOS times 30 years ago made me reminisce of DJGPP, a distribution of the GNU development tools for DOS. I remember using DJGPP back in the 1990s before I had been exposed to Linux and feeling that it was a strange beast. Compared to the Microsoft C Compiler and Turbo C++, the tooling was bloated and alien to DOS, and the resulting binaries were huge. But DJGPP provided a complete development environment for free, which I got from a monthly magazine, and I could even look at its source code if I wished. You can’t imagine what a big deal that was at the time. But even if I could look under the cover, I never did. I never really understood why was DJGPP so strange, slow, and huge, or why it even existed. Until now. As I’m in the mood of looking back, I’ve spent the last couple of months figuring out what the foundations of this software were and how it actually worked. Part of this research has resulted in the previous two posts on DOS memory management. And part of this research is this article. Let’s take a look!

February 14, 2024 · Tags: blogsystem5, dos
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Beyond the 1 MB barrier in DOS

In “From 0 to 1 MB in DOS”, I presented an overview of all the ways in which DOS and its applications tried to maximize the use of the 1 MB address space inherited from the 8086—even after the 80286 introduced support for 16 MB of memory and the 80386 opened the gates to 4 GB. I know I promised that this follow-up article would be about DJGPP, but before getting into that review, I realized I had to take another detour to cover three more topics. Namely: unreal mode, which I intentionally ignored to not derail the post; LOADALL, which I didn’t know about until you readers mentioned it; and DOS extenders, which I was planning to describe in the DJGPP article but they are a better fit for this one. So… strap your seat belts on and dive right in for another tour through the ancient techniques that DOS had to pull off to peek into the memory address space above the first MB. And get your hands ready because we’ll go over assembly code for a step-by-step jump into unreal mode.

February 7, 2024 · Tags: blogsystem5, dos
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Links: January 2024 edition

It is hard to believe but we are already one month into 2024. January has flown by for me and I haven’t done a good job at keeping up with news sites… but I have been reading them on and off and I have collected a small set of interesting articles. To everyone new around here, hello and thanks for subscribing! For some context, what follows is my manual selection of cool articles, videos, and projects I stumbled upon during this time period. However, this is not just a dump of links: each link is accompanied by a short commentary to justifies why I thought the material was interesting, why it is relevant to this publication and, more importantly, an attempt to nudge you into reading the source. Let’s get to it.

January 31, 2024 · Tags: blogsystem5, recap
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From 0 to 1 MB in DOS

Since the last article on the text-based IDEs of old, I’ve been meaning to write about the GCC port to DOS, namely DJGPP. As I worked on the draft for that topic, I realized that there is a ton of ground to cover to set the stage so I took most of the content on memory management out and wrote this separate post. This article is a deep dive on how DOS had to pull out tricks to maximize the use of the very limited 1 MB address space of the 8086. Those tricks could exist because of the features later introduced by the 80286 and the 80386, but these were just clutches to paper over the fact that DOS could not leverage the real improvements provided by protected mode. This detour is long but I hope you’ll enjoy it as much as I enjoyed researching the topic. I’ll walk you through the changes in the x86 architecture over time, starting with the 8086 and ending in the 80386, and how DOS kept up along the way. I’ll conclude with a peek into DOS’ own MEM and MemMaker utilities. I must omit details to keep the text manageable in size though, so please excuse the lack of detail in some areas; just follow the links to external documentation to learn more.

January 17, 2024 · Tags: blogsystem5, dos
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Links: December 2023 edition

December draws to a close as does 2023, which means it’s time for yet another monthly links recap. For context to everyone new around here, what follows is my manual curation of cool articles, videos, and projects I stumbled upon during this time period. But this is not just a dump of links: each link is accompanied by a short commentary that justifies why I thought the material was interesting, why it is relevant to this publication and, more importantly, an attempt to nudge you into reading it.

December 31, 2023 · Tags: blogsystem5, recap
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The IDEs we had 30 years ago... and we lost

I grew up learning to program in the late 1980s / early 1990s. Back then, I did not fully comprehend what I was doing and why the tools I used were impressive given the constraints of the hardware we had. Having gained more knowledge throughout the years, it is now really fun to pick up DOSBox to re-experience those programs and compare them with our current state of affairs. This time around, I want to look at the pure text-based IDEs that we had in that era before Windows eclipsed the PC industry. I want to do this because those IDEs had little to envy from the IDEs of today—yet it feels as if we went through a dark era where we lost most of those features for years and they are only resurfacing now. If anything, stay for a nostalgic ride back in time and a little rant on “bloat”. But, more importantly, read on to gain perspective on what existed before so that you can evaluate future feature launches more critically.

December 25, 2023 · Tags: blogsystem5, history
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Bazel interview at Software Engineering Daily

Just a bit over 2 months ago, on October 5th, 2023, Jordi Mon Companys interviewed me about Bazel for an episode in the Software Engineering Daily podcast. The episode finally came out on December 18th, 2023, so here is your announcement to stop by and listen to it! Cover image (and link) to the Bazel interview in Software Engineering Daily. If you don’t have time to listen to the whole 45 minutes, or if you want to get a sense of what you will get out of it, here is a recap of everything we touched on.

December 21, 2023 · Tags: bazel, blogsystem5
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Hard disk LEDs and noisy machines

The computers of yesteryear had this little feature known as blinking LED lights 🔆. They also had this other feature called noisy disks 💾 and loud fans 🪭. Uh wait. Features? Why “features” and not “annoyances”?! 🧵👇 Front panel of a common PC case in the late 1990s. My Pentium MMX 166 was hosted in one of these. You see, these bright lights and loud noises acted as canaries 🐦 in a performance mine.

December 15, 2023 · Tags: blogsystem5, history, twitter-thread
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Strings, encodings, NULs and Bazel

Just yesterday, Twitter user @vkrajacic wrote: Advice for new C programmers: “Avoid null-terminated strings; they’re outdated, inefficient and impractical.” Create your own type with basic functions. It’s not that hard, and it goes a long way. One of the benefits of this approach, among others, is slicing without copying. This suggestion has its merits and I understand where it is coming from: performance. You see: the traditional way to represent strings in C is to use NUL-terminated byte arrays.

December 3, 2023 · Tags: bazel, blogsystem5, java
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Links: November 2023 edition

Welcome to the second edition of my “interesting links” recap, this time covering the month of November 2023. For context, what follows is my manual curation of cool articles, videos, and projects I stumbled upon during this time period. But this is not just a dump of links: each link is accompanied by a 1-paragraph commentary that justifies why I thought the material was cool, why it is relevant to this publication and, more importantly, an attempt to nudge you into reading it.

November 30, 2023 · Tags: blogsystem5, recap
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SSH agent forwarding and tmux done right

The SSH agent is a little daemon that holds your private keys in memory. This is particularly handy when your keys are protected by a passphrase: you can unlock and add your keys to the agent once and, from then on, any SSH client such as ssh(1) can interact with the keys without asking you for the passphrase again. The SSH agent becomes even handier when you primarily work on a remote workstation over SSH.

November 17, 2023 · Tags: blogsystem5, unix
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Why do I know shell, and how can you?

“Why do you know so much shell?” is a question I’m getting a lot at work lately. So yeah, why? And how can you learn it too? There is no secret here: I know the shell well because I was “forced” to write tools in it for a while and, because of that, I made a conscious effort to learn the language and get better at it. You see, most people that write shell don’t want to deal with it. They stitch together whatever works into a script and call it a day, making a bunch of spaghetti even if it goes against the coding best practices they already know. And when they encounter some odd syntax they don’t recognize, their reaction is to say “this has to be rewritten in Python!” instead of taking a breath and trying to really understand what’s going on. It doesn’t help that plenty of senior engineers scoff at shell scripts. And it is true: the shell is arcane and has many flaws as a programming language. I don’t want to convince you to start writing new tools in it. But the shell is also an incredible rapid prototyping language, and you can use it to solve business problems really quickly and with surprisingly little code. If you pause for a second to learn it, you’ll realize that you can bend tradition and write maintainable shell code too. Hear out how I got into writing so much shell and how you can get better at it too.

November 10, 2023 · Tags: blogsystem5, personal-story, shell
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End-to-end tool testing with Bazel and shtk

If you use Bazel, your project is of moderate size. And because your project is of moderate size, it almost-certainly builds one or more binaries, at least one of which is a CLI tool. But let’s face it: you don’t have end-to-end testing for those tools, do you? I’m sure you have split the binary’s main function into its own file so that the rest of the tool can be put in a library, and I’m extra-sure that you have unit tests for such library. But… those tests do little to verify the functionality and quality of the tool as experienced by the end user. Consider: What exactly does the tool print to the console on success? Does it show errors nicely when they happen, or does it dump internal stack traces? How does it handle unknown flags or bad arguments? Is the built-in help message nicely rendered when your terminal is really wide? What if the terminal is narrow? You must write end-to-end tests for your tools but, usually, that isn’t easy to do. Until today. Combining shtk with Bazel via the new rules_shtk ruleset makes it trivial to write tests that verify the behavior of your CLI tools—no matter what language they are written in—and in this article I’m going to show you how.

November 4, 2023 · Tags: bazel, blogsystem5, shell, shtk, testing
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Links: October 2023 edition

Inspired by the works of Phil Eaton, I’ve been highlighting articles and projects that I find interesting in Twitter X and Mastodon. Some of these posts were more “successful” than I had expected, which I take to mean that doing this is interesting to you all. So, it’s probably a good idea to periodically collect them all in a post with a very brief commentary on each. Here is a recap of the interesting articles that came my way in October 2023. This does not mean that these articles were published during this period: some of them are older but I just (re)discovered them now. I’ll avoid referencing my own articles: you can find those by in the archive.

October 31, 2023 · Tags: blogsystem5, recap
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BazelCon 2023 et al. trip report

I’m exhausted. I just came back to Seattle from a 10-day trip in which I attended three different Bazel events: the Build Meetup in Reykjavik, the Bazel Community Day in Munich, and BazelCon 2023 in Munich too. Oh, and because I was on the other side of the world, I also paid a visit to my family in Spain. Attending these events has been incredibly useful and productive: I got exposure to many ideas and discussions that would just not happen online, I got to build connections with very interesting people and, of course, it has also been super fun too to reconnect with old coworkers and friends. This article contains the summary of the things I learned and the things I want to follow up on. These are just a bunch of cleaned-up notes which I took and are in the context of my work with Bazel at Snowflake and my interests on build tools, so this is not endorsed by Snowflake.

October 30, 2023 · Tags: bazel, blogsystem5, snowflake
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Hello, Blog System/5!

Blog System/5 is my new Substack publication in which I write about the variety of software and systems engineering topics that pique my interest. If that sounds too generic to you, it’s because it is: there are too many cool things to write about! And yes, this sounds exactly the same as this blog. Read on to understand the motivation behind the new publication and subscribe now to not miss a beat!

October 27, 2023 · Tags: blog, blogsystem5
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