GCC and Clang inline assembly is an interface between high and low level programming languages. It is subtle and treacherous. Many are ensnared in its traps, usually unknowingly. As such, the asm keyword is essentially the unsafe keyword of C and C++. Nearly every inline assembly tutorial, including the awful ibilio page at the top of search...
This article was discussed on Hacker News. Over the past month I’ve been exploring the rapidly evolving world of Large Language Models (LLM). It’s now accessible enough to run a LLM on a Raspberry Pi smarter than the original ChatGPT (November 2022). A modest desktop or laptop supports even smarter AI. It’s also private, offline, unlimited, and...
Windows paths have been WTF-16-encoded for decades, but module names in the import tables of Portable Executable are octets. If a name contains values beyond ASCII — technically out of spec — then the dynamic linker must somehow decode those octets into Unicode in order to construct a lookup path. There are multiple ways this could be done, and...
I’m 18 years late, but Slim Reader/Writer Locks have a fantastic interface: pointer-sized (“slim”), zero-initialized, and non-allocating. Lacking cleanup, they compose naturally with arena allocation. Sounds like a futex? That’s because they’re built on futexes introduced at the same time. They’re also complemented by condition variables with the...
Suppose you’re working in C using one of the major toolchains — that is, it’s mainly a C++ implementation — and you need regular expressions. You could integrate a library, but there’s a regex implementation in the C++ standard library included with your compiler, just within reach. As a resourceful engineer, using an asset already in hand seems...
I recently came across a take-home C programming test which had more depth and complexity than I suspect the interviewer intended. While considering it, I also came up with a novel, or at least unconventional, solution. The problem is to deep copy a linked list where each node references a random list element in addition to usual linkage —...
I introduced two new tools to w64devkit, vc++filt and peports (pronounced like purports), which aid manual symbol inspection and complement one another. As of this writing, the latter is not yet in a release, but it’s feature-complete and trivial to build if you wanted to try it out early. This article explains the motivation and purpose for...
I continue to streamline an arena-based paradigm, and stumbled upon a concise technique for dynamic growth — an efficient, generic “concatenate anything to anything” within an arena built atop a core of 9-ish lines of code. The key insight originated from a reader suggestion about dynamic arrays. The subject of concatenation can be a string,...
Occasionally we need to compute the size of an object that does not yet exist, or a subscript that may fall out of bounds. It’s easy to miss the edge cases where results overflow, creating a nasty, subtle bug, even in the presence of type safety. Ideally such computations happen in specialized code, such as inside an allocator (calloc,...