From e66448ecef3e7fe4ac9896733f343f5386a72703 Mon Sep 17 00:00:00 2001 From: Ted Mosly Date: Fri, 15 Apr 2022 20:25:51 +0800 Subject: [PATCH] 58 --- README.md | 2 +- posts/054.md | 7 +- posts/057.md | 2 +- posts/058.md | 312 +++++++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 318 insertions(+), 5 deletions(-) create mode 100644 posts/058.md diff --git a/README.md b/README.md index 9486db7..1f2531c 100644 --- a/README.md +++ b/README.md @@ -26,7 +26,7 @@ RSS使用仓库的release RSS [链接](https://github.com/wanghenshui/cppweeklyn | [二十一](./posts/021.md) | [二十二](./posts/022.md) | [二十三](./posts/023.md) | [二十四](./posts/024.md) | [二十五](./posts/025.md) | [二十六](./posts/026.md) | [二十七](./posts/027.md) | [二十八](./posts/028.md) | [二十九](./posts/029.md) | [三十期](./posts/030.md) | | [三十一](./posts/031.md) | [三十二](./posts/032.md) | [三十三](./posts/033.md) | [三十四](./posts/034.md) | [三十五](./posts/035.md) | [三十六](./posts/036.md) | [三十七](./posts/037.md) | [三十八](./posts/038.md) | [三十九](./posts/039.md) | [四十期](./posts/040.md) | | [四十一](./posts/041.md) | [四十二](./posts/042.md) | [四十三](./posts/043.md) | [四十四](./posts/044.md) | [四十五](./posts/045.md) | [四十六](./posts/046.md) | [四十七](./posts/047.md) | [四十八](./posts/048.md) | [四十九](./posts/049.md) | [五十期](./posts/050.md) | -| [五十一](./posts/051.md) | [五十二](./posts/052.md) | [五十三](./posts/053.md) | [五十四](./posts/054.md)| [五十五](./posts/055.md) | [五十六](./posts/056.md) | [五十七](./posts/057.md) | | | | +| [五十一](./posts/051.md) | [五十二](./posts/052.md) | [五十三](./posts/053.md) | [五十四](./posts/054.md)| [五十五](./posts/055.md) | [五十六](./posts/056.md) | [五十七](./posts/057.md) | [五十八](./posts/058.md) | | | diff --git a/posts/054.md b/posts/054.md index 7a51bb5..e91c30e 100644 --- a/posts/054.md +++ b/posts/054.md @@ -70,12 +70,13 @@ for(auto t : z1) - [overload 167](https://accu.org/journals/overload/30/167/overload167.pdf) -这是个期刊，每期都会录入几篇文章，文章很长。内容标题是 + 这是个期刊，每期都会录入几篇文章，文章很长。内容标题是 - What are you optimizing for? 没啥说的 - Revisiting Data-Oriented Design - An Associative Container for Non-bash Shell Scripts - C++20 Benefits: Consistency With Ranges + 没啥值得说的 - [PartialExecuter: Reducing WebAssembly size by exploring all executions in LLVM](https://medium.com/leaningtech/partialexecuter-reducing-webassembly-size-by-exploring-all-executions-in-llvm-f1ee295e8ba) @@ -112,7 +113,7 @@ for(auto t : z1) 嵌入式场景编译器优化减小程序体积 体积影响分发。从二进制角度观测/评估哪里可以省掉，用[bloaty](https://github.com/google/bloaty)查 比如strip 减少内联 (`__attribute__((noinline))`)/模板实例化以及二进制工具修改 -编译选项，-Os -flto -Wl,--strip-all (不要-g) -fno-unroll-loops -fno-execption -fno-rtti +编译选项，-Os -flto -Wl,--strip-all (不要-g) -fno-unroll-loops -fno-exception -fno-rtti 以及编译器本身提供的减少体积的选项，比如thin-lto(llvm) -fmerge-all-constant -mllvm hot-cold-split 代码组织上，不要继承不要类不要lambda，不要复制，实现移出头文件，数据结构简单就好，算法用简单的，不需要考虑性能问题，够用，拷贝尽量用memcpy @@ -125,7 +126,7 @@ for(auto t : z1) - 推荐观看 [Embracing `noexcept` Operators and Specifiers Safely - John Lakos - CppCon 2021](https://www.youtube.com/watch?v=3GwNjGMKBtI) -如果一个类只声明不实现，不能保证成员函数是noexpect(true)的（析构函数除外），之前咱们也聊过zero cost execption相关 +如果一个类只声明不实现，不能保证成员函数是noexpect(true)的（析构函数除外），之前咱们也聊过zero cost exception相关 这个视频讨论了noexcept的方方面面。比较深入。值得一看。 - [Embracing (and also Destroying) Variant Types Safely - Andrei Alexandrescu - CppCon 2021](https://www.youtube.com/watch?v=va9I2qivBOA&t=94s) diff --git a/posts/057.md b/posts/057.md index af33a44..80ef9b0 100644 --- a/posts/057.md +++ b/posts/057.md @@ -69,7 +69,7 @@ xmake真的挺好用的。自己构建小东西，推荐使用 - [Fuzzy search for C++ Reference, Qt documentation and more from shell, Vim or Neovim](https://cukic.co/2022/04/02/fuzzy-search-documentation/) -主要是使用zeal的cli工具嵌入，最近才知道zeal支持linux了。可以下载cpp的文档然后用zeal-cli来搜索，省一个搜索的功夫 +主要是使用zeal的cli工具嵌入，最近才知道zeal支持linux了。可以下载cpp的文档然后用[zeal-cli](https://gitlab.com/ivan-cukic/zeal-lynx-cli)来搜索，省一个搜索的功夫 - [Design Patterns VS Design Principles: Abstract Factory](https://www.fluentcpp.com/2022/04/06/design-patterns-vs-design-principles-abstract-factory/) diff --git a/posts/058.md b/posts/058.md new file mode 100644 index 0000000..428ee4d --- /dev/null +++ b/posts/058.md @@ -0,0 +1,312 @@ +--- +layout: post +title: 第58期 +--- + +# C++ 动态新闻推送 第58期 + + + +从[reddit](https://www.reddit.com/r/cpp/)/[hackernews](https://news.ycombinator.com/)/[lobsters](https://lobste.rs/)/[meetingcpp](https://www.meetingcpp.com/blog/blogroll/items/Meeting-Cpp-Blogroll-325.html)摘抄一些c++动态 + +[周刊项目地址](https://github.com/wanghenshui/cppweeklynews)｜[在线地址](https://wanghenshui.github.io/cppweeklynews/) ｜[知乎专栏](https://www.zhihu.com/column/jieyaren) |[腾讯云+社区](https://cloud.tencent.com/developer/column/92884) + +弄了个qq频道，[手机qq点击进入](https://qun.qq.com/qqweb/qunpro/share?_wv=3&_wwv=128&inviteCode=xzjHQ&from=246610&biz=ka) + +欢迎投稿，推荐或自荐文章/软件/资源等，请[提交 issue](https://github.com/wanghenshui/cppweeklynews/issues) + +你们说整个代码走读周会/项目分享 靠谱么。我感觉拉不到人 + +--- + +## 资讯 + +标准委员会动态/ide/编译器信息放在这里 + +[编译器信息最新动态推荐关注hellogcc公众号 2022-04-13 第145期](https://github.com/hellogcc/osdt-weekly/blob/master/weekly-2022/2022-04-13.md) + +## 文章 + +- [**Did you know that concept can be passed via lambda expression** ](https://github.com/QuantlabFinancial/cpp_tip_of_the_week/blob/master/273.md/) + +```c++ +static_assert([]{ return std::integral; }.operator()()); + +struct f { auto foo() -> void; }; +static_assert([](auto t){ return requires { t.foo(); }; }(f{})); +``` + +我觉得这玩意还是不要知道的好 + +- [可怕！CPU暗藏了这些未公开的指令！](https://zhuanlan.zhihu.com/p/498014297) + +看个乐，挺有意思的 + +- [Pointers Are Complicated III, or: Pointer-integer casts exposed](https://www.ralfj.de/blog/2022/04/11/provenance-exposed.html) + +一些c指针的缺陷。老生常谈了属于是 + +- [Using std::chrono](https://akrzemi1.wordpress.com/2022/04/11/using-stdchrono/) + +复习一下chrono，c++20有个[file_clock](https://zh.cppreference.com/w/cpp/chrono/file_clock)，干嘛的 + +- [SnapdragonProfiler崩溃问题分析](https://zhuanlan.zhihu.com/p/498034539) + +windbg调试手把手教学 + +- [Three Benchmarks of C++20 Ranges vs Standard Algorithms ](https://www.cppstories.com/2022/ranges-perf/) + +测了几种算法range和标准实现的表现。range下限稳定。能用range尽量用range + +- [Please repeat yourself: The `noexcept(noexcept(…))` idiom](https://devblogs.microsoft.com/oldnewthing/20220408-00/?p=106438) + +```c++ +template +struct Holder +{ + T value; + + template + Holder(Args&&... args) : + value(std::forward(args)...) {} +}; + +template Holder(U&&) -> + Holder> +``` + +省一个类型缩写 `Holder(42)`而不是`Holder42` 但是问题来了，如果T的构造抛异常就完了 + +标记noexcept，怎么标？ + +```c++ + template + Holder(Args&&... args) + noexcept(noexcept(T(std::forward(args)...))) : + value(std::forward(args)...) {} +``` + + + +- [Type Erasure](http://www.modernescpp.com/index.php/type-erasure) + +```c++ +#include +#include +#include +#include + +class Object { // (2) +public: + template // (3) + Object(T&& obj): object(std::make_shared>(std::forward(obj))){} + std::string getName() const { // (4) + return object->getName(); + } + struct Concept { // (5) + virtual ~Concept() {} + virtual std::string getName() const = 0; + }; + + template< typename T > // (6) + struct Model : Concept { + Model(const T& t) : object(t) {} + std::string getName() const override { + return object.getName(); + } + private: + T object; + }; + + std::shared_ptr object; +}; + +void printName(std::vector vec){ // (7) + for (auto v: vec) std::cout << v.getName() << '\n'; +} + +struct Bar{ + std::string getName() const { // (8) + return "Bar"; + } +}; + +struct Foo{ + std::string getName() const { // (8) + return "Foo"; + } +}; + +int main(){ + std::vector vec{Object(Foo()), Object(Bar())}; // (1) + printName(vec); + std::cout << '\n'; +} +``` + +学会这种封装思想.虽然不太会用到 + +- [Memory-Size Literals](https://wunkolo.github.io/post/2022/02/memory-size-literals/) + +```c++ +constexpr unsigned long long operator""_KiB(unsigned long long int x) { + return 1024ULL * x; +} + +constexpr unsigned long long operator""_MiB(unsigned long long int x) { + return 1024_KiB * x; +} + +constexpr unsigned long long operator""_GiB(unsigned long long int x) { + return 1024_MiB * x; +} + +constexpr unsigned long long operator""_TiB(unsigned long long int x) { + return 1024_GiB * x; +} + +constexpr unsigned long long operator""_PiB(unsigned long long int x) { + return 1024_TiB * x; +} +``` + +就是这段代码，分享给大家，增加代码可读性 + +作者拿这段代码到处提MR ，比如这个https://github.com/xenia-project/xenia/pull/1935/ + +- [Stringy Templates](https://vector-of-bool.github.io/2021/10/22/string-templates.html) + +还是fix_string + +```c++ +template +struct fixed_string { + char _chars[Length+1] = {}; // +1 for null terminator +}; +template +fixed_string(const char (&arr)[N]) + -> fixed_string; // Drop the null terminator + +template Str> +struct foo; + +foo<"Hello!"> hello; +foo<"world!"> world; +foo<"nope"> b; // FAIL! + +``` + +foo的这个6非常碍眼且不合理。c++20，可以自动推导了 + +```c++ +template +struct ctad_foo {}; +ctad_foo<"Hello"> h +ctad_foo<"user"> u; + +``` + +更离谱的 + +```c++ +template // [1] +struct named_type {}; + +template <> // [2] +struct named_type<"integer"> { using type = int; }; + +template <> // [2] +struct named_type<"boolean"> { using type = bool; }; + +template // [3] +using named_type_t = named_type::type; + +named_type_t<"integer"> v = 42; +named_type_t<"boolean"> b = false; + + + +template +concept names_a_type = requires { + // Require that `named_type_t` produces a valid type + typename named_type_t; +}; + +static_assert(names_a_type<"integer">); +static_assert(!names_a_type<"widget">); + +template +auto do_something() { + static_assert( + names_a_type, + "The given string must name a registered type!"); +} + +``` + +类型信息真正的存下来了。不过一时半会用不上 + + + + + +concept+ lambda + +```c++ +#include + +template struct requires_ { + template requires (Constraint.template operator()()) operator T(); +}; + +#define $requires(...) requires_<[]{ return __VA_ARGS__; }>{} + +template +concept fooable = requires(T t) { + t.foo( + $requires(std::integral<_>), + $requires(std::same_as) + ); +}; + +struct bar { void foo(); }; +static_assert(not fooable); + +struct foo1 { void foo(int, short); }; +static_assert(fooable); + +struct foo2 { void foo(int, auto); }; +static_assert(fooable); +``` + + + +## 视频 + +- [C++ Weekly - Ep 319 - A JSON To C++ Converter ](https://www.youtube.com/watch?v=HROQPE59q_w) + +一个编译期的json parser。代码在这里https://github.com/lefticus/json2cpp 玩出花来了 + + + + + +## 开源项目需要人手 + +- [asteria](https://github.com/lhmouse/asteria) 一个脚本语言，可嵌入，长期找人，希望胖友们帮帮忙，也可以加群384042845和作者对线 +- [pika](https://github.com/OpenAtomFoundation/pika) 一个nosql 存储， redis over rocksdb，非常需要人贡献代码胖友们， 感兴趣的欢迎加群294254078前来对线 + +## 新项目介绍/版本更新 + +- [C++20 library for comfortable and efficient dynamic polymorphism ](https://github.com/kelbon/AnyAny) +- [seer](https://github.com/epasveer/seer) 一个gdb前端 +- [perf-ninja](https://github.com/dendibakh/perf-ninja) 一个c++实验课程，推荐大家都做一做，他的书这里可以领https://book.easyperf.net/perf_book +- [boost 179](https://www.boost.org/users/history/version_1_79_0.html) 一些fix。没有新库，都是fix + + + +--- + +看到这里或许你有建议或者疑问或者指出错误，请留言评论! 多谢! 你的评论非常重要！也可以帮忙点赞收藏转发！多谢支持！ + +[本文永久链接](https://wanghenshui.github.io/cppweeklynews/posts/058.html)