-
Notifications
You must be signed in to change notification settings - Fork 22
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
- Loading branch information
1 parent
349e205
commit e66448e
Showing
4 changed files
with
318 additions
and
5 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -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([]<class T>{ return std::integral<T>; }.operator()<int>()); | ||
|
|
||
| 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<typename T> | ||
| struct Holder | ||
| { | ||
| T value; | ||
| template<typename... Args> | ||
| Holder(Args&&... args) : | ||
| value(std::forward<Args>(args)...) {} | ||
| }; | ||
| template<typename U> Holder(U&&) -> | ||
| Holder<std::remove_reference_t<U>> | ||
| ``` | ||
|
|
||
| 省一个类型缩写 `Holder(42)`而不是`Holder<int>42` 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<typename... Args> | ||
| Holder(Args&&... args) | ||
| noexcept(noexcept(T(std::forward<Args>(args)...))) : | ||
| value(std::forward<Args>(args)...) {} | ||
| ``` | ||
| - [Type Erasure](http://www.modernescpp.com/index.php/type-erasure) | ||
| ```c++ | ||
| #include <iostream> | ||
| #include <memory> | ||
| #include <string> | ||
| #include <vector> | ||
| class Object { // (2) | ||
| public: | ||
| template <typename T> // (3) | ||
| Object(T&& obj): object(std::make_shared<Model<T>>(std::forward<T>(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<const Concept> object; | ||
| }; | ||
| void printName(std::vector<Object> 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<Object> 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 <size_t Length> | ||
| struct fixed_string { | ||
| char _chars[Length+1] = {}; // +1 for null terminator | ||
| }; | ||
| template <size_t N> | ||
| fixed_string(const char (&arr)[N]) | ||
| -> fixed_string<N-1>; // Drop the null terminator | ||
|
|
||
| template <fixed_string<6> 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 <fixed_string S> | ||
| struct ctad_foo {}; | ||
| ctad_foo<"Hello"> h | ||
| ctad_foo<"user"> u; | ||
| ``` | ||
|
|
||
| 更离谱的 | ||
|
|
||
| ```c++ | ||
| template <fixed_string> // [1] | ||
| struct named_type {}; | ||
|
|
||
| template <> // [2] | ||
| struct named_type<"integer"> { using type = int; }; | ||
|
|
||
| template <> // [2] | ||
| struct named_type<"boolean"> { using type = bool; }; | ||
|
|
||
| template <fixed_string S> // [3] | ||
| using named_type_t = named_type<S>::type; | ||
|
|
||
| named_type_t<"integer"> v = 42; | ||
| named_type_t<"boolean"> b = false; | ||
|
|
||
|
|
||
|
|
||
| template <fixed_string Name> | ||
| concept names_a_type = requires { | ||
| // Require that `named_type_t<Name>` produces a valid type | ||
| typename named_type_t<Name>; | ||
| }; | ||
|
|
||
| static_assert(names_a_type<"integer">); | ||
| static_assert(!names_a_type<"widget">); | ||
|
|
||
| template <fixed_string S> | ||
| auto do_something() { | ||
| static_assert( | ||
| names_a_type<S>, | ||
| "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 <concepts> | ||
| template <auto Constraint> struct requires_ { | ||
| template <class T> requires (Constraint.template operator()<T>()) operator T(); | ||
| }; | ||
| #define $requires(...) requires_<[]<class _>{ return __VA_ARGS__; }>{} | ||
| template<class T> | ||
| concept fooable = requires(T t) { | ||
| t.foo( | ||
| $requires(std::integral<_>), | ||
| $requires(std::same_as<short, _>) | ||
| ); | ||
| }; | ||
| struct bar { void foo(); }; | ||
| static_assert(not fooable<bar>); | ||
| struct foo1 { void foo(int, short); }; | ||
| static_assert(fooable<foo1>); | ||
| struct foo2 { void foo(int, auto); }; | ||
| static_assert(fooable<foo2>); | ||
| ``` | ||
|
|
||
|
|
||
|
|
||
| ## 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) |