Porting C to Rust for a Fast and Safe AV1 Media Decoder
AV1 is an increasingly important video format and it needs a memory safe, high performance decoder. We worked with the team at Immunant to develop rav1d, a Rust-based port of dav1d, a C decoder. This is the first of two blog posts about how the team approached this effort. Complex data parsing is one of the most security-critical operations in modern software. Browsers must decode untrusted audio
Rambles around computer science
Diverting trains of thought, wasting precious time Tue, 27 Aug 2024 How to really wrap a C compiler and preprocessor, really* * really Suppose we want to interfere with how a vaguely Unix-style C compiler does its job, and that we want to try compiling existing software with this modified compiler. Assuming the build system will let us do something like: CC=/path/to/my/wrapper make or CC=/path/to/
Why am I writing a Rust compiler in C?
To bootstrap Rust, no cost is too great. Perceptive Rustaceans may have noticed my activity has gone down as of late. There are a handful of different reasons for this. I’ve been the subject of a truly apocalyptic series of life events, including the death of a relative that rattled me to my core. I’ve had more responsibilities at work, leaving me with less time and energy to contribute. Maybe I’v
Picking glibc versions at runtime
In a recent work discussion, I came across an argument that didn’t sound quite right. The claim was that we needed to set up containers in our developer machines in order to run tests against a modern glibc. The justifications were that using LD_LIBRARY_PATH to load a different glibc didn’t work and statically linking glibc wasn’t possible either. But… running a program against a version of glibc
C is Turing complete – Tony Finch
Yesterday there was some discussion on the Orange Site about whether or not C is Turing complete. The consensus in the StackOverflow question is, no, because the C abstract machine is a (large) finite state machine, or maybe yes, if you believe that unaddressable local variables can exist outside the finite address space, and you can have an unbounded number of them, i.e. no. My answer is definite
Deep list copy: More than meets the eye
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 — similar to LeetCode problem 138. This reference is one of
strlcpy and how CPUs can defy common sense
strlcpy and how CPUs can defy common sense 24 Jul 2024 Recently one of my older post about strlcpy has sparked some discussion on various forums. Presumably the recently released POSIX edition had something to do with it. One particular counter-argument was raised by multiple posters - and it's an argument that I've heard before as well: In the common case where the source string fits in to the de
C言語を学びたての人のための電卓自作
電卓を通じて、再帰下降構文解析を使った構文解析を行います。インタプリタ自作やコンパイラ自作の前段階として挑むとちょうど良いのではと思います。 ステップ1からステップ15まであり、最終的に括弧を使った式を解析できる電卓が出来上がります。各ステップは少しの書き換えだけで済むようになっています。 「大学に入ってからプログラミングを始めて、1年生でC言語を学んでいる」という人に向けて書きました。 「このステップは難しすぎる」「説明が分からない」「ここの説明は間違っている」等があれば、sou7まで連絡を頂けるとありがたいです。また、実装してみて「みてみて！電卓が実装できたよ！」というときにも連絡を頂けると嬉しいです。 参考実装はこちらにありますCommits · soukouki/c-calc · GitHub。ステップごとにコミットを分けてあるので、難しくて進められない場合は参考にしてください。
malloc.c を読む (malloc / free)
このシリーズではこれらの関数が内部でどのように処理されるのかを調べていきます。 malloc.c を読む (malloc / free) malloc.c を読む (bins) malloc.c を読む (arena) 今回は malloc() free() の全体像を紹介します。 注意としてここでの目的は全体を俯瞰して、詳細を詰めずとも各 bins の役割を理解し、攻撃手法を理解できるようにすることです。それに合わないマルチスレッドや最適化などにおける緻密なトリックやコーナーケースなどは暗黙的に実装されていると仮定します。その詳細についてはソースコードや他の資料を参考にしていただきたいです。 ここで扱う glibc のバージョンは v2.38 です。また glibc のソースコードはブラウザ上で読むことができます。 https://elixir.bootlin.com/glibc/lat
Achieving OpenBLAS-Level Performance in Multi-Threaded Matrix Multiplication: A Tutorial
TL;DR The code from the tutorial is available at matmul.c. This blog post is the result of my attempt to implement high-performance fp32 matrix multiplication (=SGEMM) on CPU while keeping the code simple and scalable. The implementation follows BLIS design, works for arbitrary matrix sizes, and on AMD Ryzen 7 7700 outperforms NumPy with OpenBLAS and MKL backends, achieving over 1 TFLOPS across a
Your Own Constant Folder in C/C++
I was talking with someone today that really really wanted the sqrtps to be used in some code they were writing. And because of a quirk with clang (still there as of clang 18.1.0), if you happened to use -ffast-math clang would butcher the use of the intrinsic. So for the code: __m128 test(const __m128 vec) { return _mm_sqrt_ps(vec); } Clang would compile it correctly without fast-math: test: # @t
リリース、障害情報などのサービスのお知らせ
最新の人気エントリーの配信
j次のブックマーク
k前のブックマーク
lあとで読む
eコメント一覧を開く
oページを開く
The perils of transition to 64-bit time_t
GitHub - NICUP14/MiniLang: A type-safe C successor that compiles directly to various platforms.
N3332: _Record types
C Macro Reflection in Zig – Zig Has Better C Interop Than C Itself
Counting Bytes Faster Than You’d Think Possible
GitHub - bourguet/operator_precedence_parsing: C89 expressions parsed with the shunting yard algorithm in Python
GitHub - Vexu/arocc: A C compiler written in Zig.
GitHub - linkdd/larena: Yet another simple header only arena allocator for C11
GitHub - zserge/jsmn: Jsmn is a world fastest JSON parser/tokenizer. This is the official repo replacing the old one at Bitbucket
