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src
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OpenBSD Upgrade 7.3 to 7.4
The OpenBSD project released 7.4 of their OS on 16 Oct 2023 as their 55th release đź’«
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OpenBSD System-Call Pinning
Well since https://www.openbsd.org/ still says
> Only two remote holes in the default install, in a heck of a long time!
I'm assuming not, but I could always be mistaken.
- Project Bluefin: an immutable, developer-focused, Cloud-native Linux
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From Nand to Tetris: Building a Modern Computer from First Principles
> building a cat from scratch
> That would be an interesting project.
Here is the source code of the OpenBSD implementation of cat:
> https://github.com/openbsd/src/blob/master/bin/cat/cat.c
and here of the GNU coreutils implementation:
> https://github.com/coreutils/coreutils/blob/master/src/cat.c
Thus: I don't think building a cat from scratch or creating a tutorial about that topic is particularly hard (even though the HN audience would likely be interested in it). :-)
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OpenBSD – pinning all system calls
> I don't know how they define `MAX`, but I'm guessing it's a typical "a>b?a:b"
Indeed: https://github.com/openbsd/src/blob/master/sys/sys/param.h#L...
> Then `SYS_kbind` seems to be a signed int.
It's an untyped #define: https://github.com/openbsd/src/blob/master/sys/sys/syscall.h...
I believe your whole analysis is correct, that running an elf file with an openbsd.syscalls entry with .sysno > INT_MAX will allow an out-of-bounds write.
- Une nouvelle mise à jour de Systemd permettra à Linux de bénéficier de l'infâme "écran bleu de la mort" de Windows, mais la fonctionnalité a reçu un accueil très mitigé
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tmux causing ANSI color-response garbage on attaching?
I can reproduce it. And this is the commit that causes the issue: https://github.com/openbsd/src/commit/d21788ce70be80e9c4ed0c52c149e01147c4a823
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Sudo-rs' first security audit
This doesn’t really change your conclusion, but I think that’s the wrong file. This is the real doas afaict: https://github.com/openbsd/src/blob/master/usr.bin/doas/doas...
Still just a tidy 1072 lines in that folder though.
I spent 5 minutes staring at your file trying to understand how on earth it does the things in the man page, but of course it doesn’t.
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OpenBSD: Removing syscall(2) from libc and kernel
OpenBSD developers are making serious effort to kill off indirect syscalls, the base system is completely clean, take a look at the work Andrew Fresh did to adapt Perl. He write a complete syscall "dispatcher" or emulator for the Perl syscall function so that it calls the libc stubs.
https://github.com/openbsd/src/commit/312e26c80be876012ae979...
The ports tree is also being cleansed of syscall(2) usage, until they're all gone.
msyscall, pinsyscall, recent mandatory IBT/BTI, xonly. OpenBSD is making waves, but people aren't really seeing them yet.
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"<ESC>[31M"? ANSI Terminal security in 2023 and finding 10 CVEs
Actually, I got it wrong, too many vulnerabilities in flight. They did fix it: https://github.com/openbsd/src/commit/375ccafb2eb77de6cf240e...
Klib
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Factor is faster than Zig
In my example the table stores the hash codes themselves instead of the keys (because the hash function is invertible)
Oh, I see, right. If determining the home bucket is trivial, then the back-shifting method is great. The issue is just that it’s not as much of a general-purpose solution as it may initially seem.
“With a different algorithm (Robin Hood or bidirectional linear probing), the load factor can be kept well over 90% with good performance, as the benchmarks in the same repo demonstrate.”
I’ve seen the 90% claim made several times in literature on Robin Hood hash tables. In my experience, the claim is a bit exaggerated, although I suppose it depends on what our idea of “good performance” is. See these benchmarks, which again go up to a maximum load factor of 0.95 (Although boost and Absl forcibly grow/rehash at 0.85-0.9):
https://strong-starlight-4ea0ed.netlify.app/
Tsl, Martinus, and CC are all Robin Hood tables (https://github.com/Tessil/robin-map, https://github.com/martinus/robin-hood-hashing, and https://github.com/JacksonAllan/CC, respectively). Absl and Boost are the well-known SIMD-based hash tables. Khash (https://github.com/attractivechaos/klib/blob/master/khash.h) is, I think, an ordinary open-addressing table using quadratic probing. Fastmap is a new, yet-to-be-published design that is fundamentally similar to bytell (https://www.youtube.com/watch?v=M2fKMP47slQ) but also incorporates some aspects of the aforementioned SIMD maps (it caches a 4-bit fragment of the hash code to avoid most key comparisons).
As you can see, all the Robin Hood maps spike upwards dramatically as the load factor gets high, becoming as much as 5-6 times slower at 0.95 vs 0.5 in one of the benchmarks (uint64_t key, 256-bit struct value: Total time to erase 1000 existing elements with N elements in map). Only the SIMD maps (with Boost being the better performer) and Fastmap appear mostly immune to load factor in all benchmarks, although the SIMD maps do - I believe - use tombstones for deletion.
I’ve only read briefly about bi-directional linear probing – never experimented with it.
- A simple hash table in C
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So what's the best data structures and algorithms library for C?
It could be that the cost of the function calls, either directly or via a pointer, is drowned out by the cost of the one or more cache misses inevitably invoked with every hash table lookup. But I don't want to say too much before I've finished my benchmarking project and published the results. So let me just caution against laser-focusing on whether the comparator and hash function are/can be inlined. For example stb_ds uses a hardcoded hash function that presumably gets inlined, but in my benchmarking (again, I'll publish it here in coming weeks) shows it to be generally a poor performer (in comparison to not just CC, the current version of which doesn't necessarily inline those functions, but also STC, khash, and the C++ Robin Hood hash tables I tested).
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Generic dynamic array in 60 lines of C
Not an entirely uncommon idea. I've written one.
There's also a well-known one here, in klib: https://github.com/attractivechaos/klib/blob/master/kvec.h
- C_dictionary: A simple dynamically typed and sized hashmap in C - feedback welcome
- Inside boost::unordered_flat_map
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The New Ghostscript PDF Interpreter
Code reuse is achievable by (mis)using the preprocessor system. It is possible to build a somewhat usable API, even for intrusive data structures. (eg. the linux kernel and klib[1])
I do agree that generics are required for modern programming, but for some, the cost of complexity of modern languages (compared to C) and the importance of compatibility seem to outweigh the benefits.
- C LIBRARY
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boost::unordered map is a new king of data structures
Unordered hash map shootout CMAP = https://github.com/tylov/STC KMAP = https://github.com/attractivechaos/klib PMAP = https://github.com/greg7mdp/parallel-hashmap FMAP = https://github.com/skarupke/flat_hash_map RMAP = https://github.com/martinus/robin-hood-hashing HMAP = https://github.com/Tessil/hopscotch-map TMAP = https://github.com/Tessil/robin-map UMAP = std::unordered_map Usage: shootout [n-million=40 key-bits=25] Random keys are in range [0, 2^25). Seed = 1656617916: T1: Insert/update random keys: KMAP: time: 1.949, size: 15064129, buckets: 33554432, sum: 165525449561381 CMAP: time: 1.649, size: 15064129, buckets: 22145833, sum: 165525449561381 PMAP: time: 2.434, size: 15064129, buckets: 33554431, sum: 165525449561381 FMAP: time: 2.112, size: 15064129, buckets: 33554432, sum: 165525449561381 RMAP: time: 1.708, size: 15064129, buckets: 33554431, sum: 165525449561381 HMAP: time: 2.054, size: 15064129, buckets: 33554432, sum: 165525449561381 TMAP: time: 1.645, size: 15064129, buckets: 33554432, sum: 165525449561381 UMAP: time: 6.313, size: 15064129, buckets: 31160981, sum: 165525449561381 T2: Insert sequential keys, then remove them in same order: KMAP: time: 1.173, size: 0, buckets: 33554432, erased 20000000 CMAP: time: 1.651, size: 0, buckets: 33218751, erased 20000000 PMAP: time: 3.840, size: 0, buckets: 33554431, erased 20000000 FMAP: time: 1.722, size: 0, buckets: 33554432, erased 20000000 RMAP: time: 2.359, size: 0, buckets: 33554431, erased 20000000 HMAP: time: 0.849, size: 0, buckets: 33554432, erased 20000000 TMAP: time: 0.660, size: 0, buckets: 33554432, erased 20000000 UMAP: time: 2.138, size: 0, buckets: 31160981, erased 20000000 T3: Remove random keys: KMAP: time: 1.973, size: 0, buckets: 33554432, erased 23367671 CMAP: time: 2.020, size: 0, buckets: 33218751, erased 23367671 PMAP: time: 2.940, size: 0, buckets: 33554431, erased 23367671 FMAP: time: 1.147, size: 0, buckets: 33554432, erased 23367671 RMAP: time: 1.941, size: 0, buckets: 33554431, erased 23367671 HMAP: time: 1.135, size: 0, buckets: 33554432, erased 23367671 TMAP: time: 1.064, size: 0, buckets: 33554432, erased 23367671 UMAP: time: 5.632, size: 0, buckets: 31160981, erased 23367671 T4: Iterate random keys: KMAP: time: 0.748, size: 23367671, buckets: 33554432, repeats: 8, sum: 4465059465719680 CMAP: time: 0.627, size: 23367671, buckets: 33218751, repeats: 8, sum: 4465059465719680 PMAP: time: 0.680, size: 23367671, buckets: 33554431, repeats: 8, sum: 4465059465719680 FMAP: time: 0.735, size: 23367671, buckets: 33554432, repeats: 8, sum: 4465059465719680 RMAP: time: 0.464, size: 23367671, buckets: 33554431, repeats: 8, sum: 4465059465719680 HMAP: time: 0.719, size: 23367671, buckets: 33554432, repeats: 8, sum: 4465059465719680 TMAP: time: 0.662, size: 23367671, buckets: 33554432, repeats: 8, sum: 4465059465719680 UMAP: time: 6.168, size: 23367671, buckets: 31160981, repeats: 8, sum: 4465059465719680 T5: Lookup random keys: KMAP: time: 0.943, size: 23367671, buckets: 33554432, lookups: 34235332, found: 29040438 CMAP: time: 0.863, size: 23367671, buckets: 33218751, lookups: 34235332, found: 29040438 PMAP: time: 1.635, size: 23367671, buckets: 33554431, lookups: 34235332, found: 29040438 FMAP: time: 0.969, size: 23367671, buckets: 33554432, lookups: 34235332, found: 29040438 RMAP: time: 1.705, size: 23367671, buckets: 33554431, lookups: 34235332, found: 29040438 HMAP: time: 0.712, size: 23367671, buckets: 33554432, lookups: 34235332, found: 29040438 TMAP: time: 0.584, size: 23367671, buckets: 33554432, lookups: 34235332, found: 29040438 UMAP: time: 1.974, size: 23367671, buckets: 31160981, lookups: 34235332, found: 29040438
- C++ containers but in C
What are some alternatives?
cosmopolitan - build-once run-anywhere c library
stb - stb single-file public domain libraries for C/C++
bastille - Bastille is an open-source system for automating deployment and management of containerized applications on FreeBSD.
Better String - The Better String Library
buttersink - Buttersink is like rsync for btrfs snapshots
Better Enums - C++ compile-time enum to string, iteration, in a single header file
PHPT - The PHP Interpreter
ZXing - ZXing ("Zebra Crossing") barcode scanning library for Java, Android
Joomla! - Home of the Joomla! Content Management System
ZLib - A massively spiffy yet delicately unobtrusive compression library.
ctl - The C Template Library
HTTP Parser - http request/response parser for c