Buffered output typically comes in two flavors: fully buffered and line buffered. If output goes to a terminal then the implementation automatically selects line buffering, flushing its buffer when a line is completed so that it reaches the user immediately. Otherwise it fully buffers, holding output until the buffer…
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This has been a ground-breaking year for my C skills, and paradigm shifts in my technique has provoked me to reconsider my habits and coding style. It’s been my largest personal style change in years, so I’ve decided to take a snapshot of its current state and my reasoning. These changes have produced significant…
Most widely-used programming languages have at least one regular conference dedicated to discussing it. Heck, even Lisp has one . It’s a place to talk about the latest developments of the language, recent and upcoming standards, and so on. However, C is a notable exception. Despite its role as the foundation of the…
Regardless of your opinions of the Go programming language , the primary implementation of Go, gc, is an incredible piece of software engineering. Everyone ought to be blown away by it! Yet not only is it undervalued in general, even the Go community itself doesn’t fully appreciate it. It’s not perfect, but it has…
In the past year I’ve written a number of minimalist C libraries, particularly header libraries. The distinction for “minimalist” is, of course, completely arbitrary and subjective. My definition in this context isn’t about the library’s functionality being stupidly trivial or even necessarily simple. I’m talking…
One of the frequent challenges in C is that pointers are nothing but a memory address. A callee who is passed a pointer doesn’t truly know anything other than the type of object being pointed at, which says some things about alignment and how that pointer can be used… maybe. If it’s a pointer to void ( void * ) then…
In 2007 I wrote a pair of modding tools, binitools , for a space trading and combat simulation game named Freelancer . The game stores its non-art assets in the format of “binary INI” files, or “BINI” files. The motivation for the binary format over traditional INI files was probably performance: it’s faster to load…
I love when my current problem can be solved with a state machine. They’re fun to design and implement, and I have high confidence about correctness. They tend to:
In my first decade writing Makefiles, I developed the bad habit of liberally using GNU Make’s extensions. I didn’t know the line between GNU Make and the portable features guaranteed by POSIX. Usually it didn’t matter much, but it would become an annoyance when building on non-Linux systems, such as on the various…
The major compilers have an enormous number of knobs . Most are highly specialized, but others are generally useful even if uncommon. For warnings, the venerable -Wall -Wextra is a good start, but circumstances improve by tweaking this warning set. This article covers high-hitting development-time options in GCC…
This week I took a crack at writing a branchless UTF-8 decoder: a function that decodes a single UTF-8 code point from a byte stream without any if statements, loops, short-circuit operators, or other sorts of conditional jumps. You can find the source code here along with a test suite and benchmark:
Over the past year I’ve refined my approach to arena allocation . With practice, it’s effective, simple, and fast; typically as easy to use as garbage collection but without the costs. Depending on need, an allocator can weigh just 7–25 lines of code — perfect when lacking a runtime . With the core details of my own…
For some time Elfeed was experiencing a strange, spurious failure. Every so often users were seeing an error (spoiler warning) when updating feeds: “error in process sentinel: Search failed.” If you use Elfeed, you might have even seen this yourself. From the surface it appeared that curl, tasked with the…
I’ve noticed a small pattern across a few of my projects where I had vectorized and parallelized some code. The original algorithm had a “push” approach, the optimized version instead took a “pull” approach. In this article I’ll describe what I mean, though it’s mostly just so I can show off some pretty videos…
Over on GitHub, David Yu has an interesting performance benchmark for function calls of various Foreign Function Interfaces ( FFI ):
Yesterday I wrote that setjmp is handy and that it would be nice to have without linking the C standard library. It’s conceptually simple, after all. Today let’s explore some differently-portable implementation possibilities with distinct trade-offs. At the very least it should illuminate why setjmp sometimes requires…
Due to sheer coincidence of several unrelated tasks converging on Python at work, I recently needed to brush up on my Python skills. So far for me, Python has been little more than a fancy extension language for BeautifulSoup , though I also used it to participate in the recent tradition of writing one’s own static…
Suppose you’re writing a non-GUI C application intended to run on a number of operating systems: Linux, the various BSDs, macOS, classical unix , and perhaps even something as exotic as Windows. It might sound like a rather complicated problem. These operating systems have slightly different interfaces (or very…
Over the past couple months I’ve discovered a couple of handy tricks for working with GDB breakpoints. I figured these out on my own, and I’ve not seen either discussed elsewhere, so I really ought to share them.
I’ve been fascinated with local LLMs for a couple of years now. The better open weight models, including some that inference on regular, higher-end consumer hardware at tolerable speeds, are now reliable enough to handle simpler programming tasks. This requires a coding harness, but so far this year I’ve been…
Emacs 26.1 was recently released . As you would expect from a major release, it comes with lots of new goodies. Being a bit of an Emacs Lisp enthusiast , the two most interesting new features are generators ( iter ) and native threads ( thread ).
Linux has an elegant and beautiful design when it comes to threads: threads are nothing more than processes that share a virtual address space and file descriptor table. Threads spawned by a process are additional child processes of the main “thread’s” parent process. They’re manipulated through the same process…
The Quite OK Image (QOI) format was announced late last year and finalized into a specification a month later. Initially dismissive, a revisit has shifted my opinion to impressed. The format hits a sweet spot in the trade-off space between complexity, speed, and compression ratio. Also considering its alpha channel…
The most recent Smarter Every Day (#172) explains a phenomenon that results from rolling shutter . You’ve likely seen this effect in some of your own digital photographs. When a CMOS digital camera captures a picture, it reads one row of the sensor at a time. If the subject of the picture is a fast-moving object…
Today there was a question on /r/C_Programming about the effect of C’s const on optimization. Variations of this question have been asked many times over the past two decades. Personally, I blame naming of const .
In general, when working in C I avoid the standard library, libc, as much as possible. If possible I won’t even link it. For people not used to working and thinking this way, the typical response is confusion. Isn’t that like re-inventing the wheel? For me, libc is a wheel barely worth using — too many deficiencies in…
Now they’ve gone an done it. An unidentified agency has spread a potent computer virus across all the world’s computers and deleted the binaries for every copy of every software development tool. Even the offline copies — it’s that potent.
Users of mature C libraries conventionally get to choose how memory is allocated — that is, when it cannot be avoided entirely . The C standard never laid down a convention — perhaps for the better — so each library re-invents an allocator interface. Not all are created equal, and most repeat a few fundamental…
Did you know that Emacs comes with a calculator ? Woop-dee-doo! Call the presses! Wow, a whole calculator! Sounds a bit lame, right?
When designing or, in some cases, implementing a programming language with built-in support for Unicode strings, an important decision must be made about how to represent or encode those strings in memory. Not all representations are equal, and there are trade-offs between different choices.
While considering concurrent queue design I came up with a generic, lock-free queue that fits in a 32-bit integer. The queue is “generic” in that a single implementation supports elements of any arbitrary type, despite an implementation in C. It’s lock-free in that there is guaranteed system-wide progress. It can…