A leadership crisis in the Nix community https://lwn.net/SubscriberLink/970824/0d89c6d83efad1e0/

Zed Decoded: Rope and SumTree https://zed.dev/blog/zed-decoded-rope-sumtree

zed.dev

Zed Decoded: Rope & SumTree

From the Zed Blog: In this episode of Zed Decoded, Thorsten asks the founders — Nathan, Max, Antonio — about the data structures at the heart of Zed: Rope and SumTree.

via Cascade Kobayashi

TypeScript: Branded Types https://prosopo.io/articles/typescript-branding/

Prosopo

TypeScript: Branded Types 🔧

How to brand TypeScript types for norminal typing, providing an automated and easy-to-use way of making a type nominal.

Borrow Checking, RC, GC, and the Eleven () Other Memory Safety Approaches https://verdagon.dev/grimoire/grimoire

今日修水管

最近一两周发现家里的水压出奇地低。我住在一栋电梯楼内的三层，照理水压不应该低。刚开始以为是市政供水的问题，但低水压情况持续了好几天没有缓解。遂前往我所在楼层的水表间尝试定位并修复该问题。

在家中水龙头全部关闭的情况下，水表没有走表。这说明家庭管路内没有漏水等情况。

我所在楼层共有四户住户，四根入户水管以并联形式直接连接到单元楼内的一根主供水管道上。在邻居用水时观察邻居的水表走表情况，发现其走表速度明显高于我用水时的走表速度。说明问题出在我家的入户水管上。这一小段入户水管上有且仅有水表以及三个阀门。这四个设备按照从上游到下游排列分别为：阀门 A、阀门 B、阀门 C 和水表。其中阀门 A 和阀门 C 上直接有可供手拧的阀门开关。尝试分别将这两个阀门拧到最大，但问题并没有消失。于是将注意力集中于阀门 B 。

阀门 B 上没有可供手拧的开关，有且仅有一个螺栓和一个压力表。经检查，在不用水时，该压力表显示读数与邻居的压力表读数一致。该读数应该就是单元楼主供水管道内的压力值。在用水时，我家的压力表读数为 0，而在邻居用水时其压力表读数并不为 0 。

上网查阅相关资料可知，阀门 B 是一个减压阀，相关资料指出减压阀上的螺栓可用于调节输出压力。遂翻出扳手等工具相应调节减压阀的螺栓。经过反复调节后，家中的水压恢复了正常。因此问题的原因是我家的减压阀因某种原因被拧了。

2024 年 4 月 Tokyo 会议后一些频道主认为有意思的 C++ 标准提案

P1061R8: Structured Bindings can introduce a Pack
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p1061r8.html

允许结构化绑定引入 pack ：

std::tuple<X, Y, Z> f();

auto [...xs] = f();           // OK
auto [x, ...rest] = f();      // OK
auto [x,y,z, ...rest] = f();  // OK
auto [x, ...rest, z] = f();   // OK

P2034R3: Partially Mutable Lambda Captures
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p2034r3.pdf

允许分别将每个 lambda 捕获声明为 mutable 了：

auto a = [mutable x, y]() {
  x = 1;  // OK
  y = 2;  // Error
};

P2135R1: P2055R1: A Relaxed Guide to memory_order_relaxed
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p2135r1.pdf

一篇科普性质文章，介绍 C++11 relaxed 内存序的原子操作的 out-of-thin-air 现象以及 read-from-untaken-branch 现象，以及如何在已有程序中识别潜在的相关问题

P2141R2: Aggregates are named tuples
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p2141r2.html

让 std::get, std::tuple_element 以及 std::tuple_size 等实现 tuple protocol 的 STL 函数和 type traits 原生支持 aggregate 类型：

struct Foo { int x; double y; std::string z; };

Foo x{1, 2.0, "3"};
std::get<1>(x);  // Evaluate to 2.0
static_assert(std::is_same_v<
  std::string,
  typename std::tuple_element<2, Foo>::type
>);  // OK
static_assert(std::tuple_size<Foo> == 3);  // OK

P2747R2: constexpr placement new
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p2747r2.html

让 placement-new 成为 core constant expression

P2748R5: Disallow Binding a Returned Glvalue to a Temporary
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p2748r5.html

当函数返回一个引用时，不再允许这个引用绑定到临时对象上，杜绝一类 use-after-free 缺陷：

const int &foo() {
  return 42;  // Ill-formed
}

P2988R4: std::optional<T&>
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p2988r4.pdf

给 std::optional 引入 std::optional<T&> 特化，可以实现用 std::optional 上的 monadic 操作替换一堆空指针判断

逐步氧化起来了

P3166R0: Static Exception Specifications
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p3166r0.html

又要搞大新闻，重新引入了之前被废弃的 throw 声明符，可以用于声明一个函数所能够抛出的所有可能的异常类型：

void throws_nothing() throw();  // Effectively `noexcept`
void throws_a_b() throw(A, B);  // throws_a_b can throw A or B
void throws_any() throw(...);   // throws_any may throw any exception

一个亮点是允许使用 throw(auto) 自动推导函数可能抛出的异常类型集合：

void foo() throw(auto) { /* ... */ }

与老式 throw 声明符的本质区别在于编译器会强制检查异常集合的正确性。如果函数带有 throw 声明符但却可能抛出没有通过 throw 声明符声明的异常，那么程序 ill-formed：

void foo() throw(A) {
  throws_a_b(); // Ill-formed: B is not listed above

  try {
    throws_a_b(); // Ill-formed: B is not caught
  }
  catch (A) {}

  try {
    throws_a_b(); // OK since B will be caught
  }
  catch (A) {}
  catch (B) {}
}

按照这样的设计编译器理论上可以把所有带有 throw 声明符的函数的异常路径算得明明白白，可以开始优化 try-catch 路径了（例如把 throw-catch 直接优化为 goto）。

P3176R0: The Oxford variadic comma
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p3176r0.html

不再允许不带前导逗号的 ellipsis parameter ：

void foo(int ...);  // Ill-formed

Porting a cross-platform GUI application to Rust

Comments

via hacks.mozilla.org via wezm

Mozilla Hacks – the Web developer blog

Porting a cross-platform GUI application to Rust

The Firefox crash reporter has been ported to Rust, with an architecture supporting native cross-platform GUI rendering.

Sized, DynSized, and Unsized

Comments

via smallcultfollowing.com via jmillikin

lobste.rs

Sized, DynSized, and Unsized

0 comments

Good Ideas in Computer Science

Comments

via danielchasehooper.com via DanielHooper

Danielchasehooper

Good Ideas in Computer Science

Ideas every programmer likes and why Garbage Collection and Object Oriented Programming don’t count

今日大脑和手指打架：

大脑：csv! csv! csv! csv!
手：vsc

Understanding a Trait Selection Bug in Rust Compiler

Comments

via veera.app via veera

veera.app

Understanding a Trait Selection Bug

The Performance Impact of C++'s `final` Keyword

Comments

via 16bpp.net via raymii

lobste.rs

The Performance Impact of C++'s `final` Keyword

15 comments

Coroutines and effects https://without.boats/blog/coroutines-and-effects/

Dataflow Analyses and Compiler Optimizations That Use Them, for Free https://blog.regehr.org/archives/2578

3rd Edition of Programming: Principles and Practice Using C++ by Stroustrup (🔥 Score: 150+ in 3 hours)

Link: https://readhacker.news/s/66gMm
Comments: https://readhacker.news/c/66gMm

Stroustrup

Stroustrup: Programming -- Principles and Practice Using C++ (3rd Edition)

Support page for Programming -- Principles and Practice Using C++ (3rd Edition).

#交通 #metro
明起上海地铁三站试点“闸机常开门”模式｜请乘客正常刷卡（码）有序过闸

为进一步提升车站闸机的客流通行能力，学习借鉴国外同行的经验做法，自2024年4月20日至6月30日，上海地铁将在张华浜、杨树浦路、吴中路3座车站首度试点实测“闸机常开门”模式，即这三站的闸机日常均保持打开状态，乘客正常刷卡或扫码后，无需等待扇门开启即可快速进出闸机。

当闸机接受到无效车票或无票通过时，闸机扇门将自动合拢，阻挡通道，乘客须重新刷卡、扫码或寻求工作人员协助票务处置；同时，排队进出站时，当前面的乘客通过后，后面的乘客无须等待闸门关闭后再刷卡或扫码，而是可以直接刷卡或扫码通行；另外，希望乘客在高峰期排队有序进出闸机，勿拥抢，共同保障高效率通行。

InstantView from Source

woc，太先进了

Telegraph

明起上海地铁三站试点“闸机常开门”模式｜请乘客正常刷卡（码）有序过闸

上海地铁shmetro

Formal Mechanised Semantics of CHERI C: Capabilities, Undefined Behaviour https://dl.acm.org/doi/10.1145/3617232.3624859?ai=&ui=&af=

ACM Conferences

Formal Mechanised Semantics of CHERI C: Capabilities, Undefined Behaviour, and Provenance | Proceedings of the 29th ACM International…