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C++ 动态新闻推送 第51期
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@wanghenshui wanghenshui released this 25 Feb 12:57
· 195 commits to dev since this release
v0.5.1
9a84d55

从reddit/hackernews/lobsters/meetingcpp摘抄一些c++动态

周刊项目地址｜在线地址 ｜知乎专栏 |腾讯云+社区

弄了个qq频道，手机qq点击进入

欢迎投稿，推荐或自荐文章/软件/资源等，请提交 issue
资讯

标准委员会动态/ide/编译器信息放在这里

标准委员会二月份邮件列表

推荐阅读 C++ exceptions are becoming more and more problematic

异常，太坑了

编译器信息最新动态推荐关注hellogcc公众号 本周更新 2022-02-23 第138期
文章

[Linux's getrandom() Sees A 8450% Improvement With Latest Code](https://git.kernel.org/pub/scm/linux/kernel/git/crng/random.git/log/)

替换了算法，使用black而不是sha1

[Chrome V8 源码 解读系列](https://www.zhihu.com/people/v8blink/posts)

这个人写了很多文章。对浏览器感兴趣的/业界人士可以关注一波。我不太懂就不多说了

[My favorite C++20 feature](https://schneide.blog/2022/02/21/my-favorite-c20-feature/)

这玩意, 确实挺方便

auto request = http_request{
.method = http_method::get,
.uri = "localhost:7634",
.headers = { { .name = "Authorization", .value = "Bearer TOKEN" } },
};

[c++反射深入浅出 - 1. ponder 反射实现分析总篇](https://zhuanlan.zhihu.com/p/471396674)
[c++反射深入浅出 - 2. property 实现分析](https://zhuanlan.zhihu.com/p/472265782)

解析ponder这个库。对于想学习反射的值得一看

[A Good Way to Handle Errors Is To Prevent Them from Happening in the First Place](https://www.fluentcpp.com/2022/02/25/a-good-way-to-handle-errors-is-to-prevent-them-from-happening-in-the-first-place/)

尽可能把错误处理掉或者用optional /expect / outcame包装处理掉

[Returning values and errors](https://rachelbythebay.com/w/2022/02/20/return/)

string* UserIP(); //1
string UserIP(string* errmsg); //2
bool GetUserIP(string* ip); //3
bool GetUserIP(string* ip, string* errmsg); //4
Result UserIP(); //5
ResultString UserIP(); //6
string UserIP(); //7

大家觉得哪个接口好？

1肯定不行，2 3 4都需要传进个string处理，比较脏， 5是不是太复杂了，6是简单版本，但是会不会又有ResultDouble之类的东西？7简单，只有ip，errmsg不放进去，也许这个才是最优解？

开放题，没有答案

[Implementing the FLIP algorithm](https://www.jeremyong.com/color%20theory/2022/02/19/implementing-the-flip-algorithm/)

图形学的东西，不太懂，这里标记TODO

[Ways to Refactor Toggle/Boolean Parameters in C++](https://www.cppstories.com/2017/03/on-toggle-parameters/)

DoImportantStuff(true, false, true, false);

我们都知道这种参数会有莫名其妙的问题，丢失值的信息，一个两个倒还好，多了难免眼花，怎么重构，封装成enum

enum class UseCacheFlag { False, True };
enum class DeferredFlag { False, True };
enum class OptimizeFlag { False, True };
enum class FinalRenderFlag { False, True };

// and call like:
RenderGlyphs(glyphs,
UseCacheFlag::True,
DeferredFlag::False,
OptimizeFlag::True,
FinalRenderFlag::False);

使用bit flag

#include <type_traits>

struct Glyphs { };

enum class RenderGlyphsFlags
{
useCache = 1,
deferred = 2,
optimize = 4,
finalRender = 8,
};

// simplification...
RenderGlyphsFlags operator | (RenderGlyphsFlags a, RenderGlyphsFlags b) {
using T = std::underlying_type_t ;
return static_cast(static_cast(a) | static_cast(b));
// todo: missing check if the new value is in range...
}

constexpr bool IsSet(RenderGlyphsFlags val, RenderGlyphsFlags check) {
using T = std::underlying_type_t ;
return static_cast(val) & static_cast(check);
// todo: missing additional checks...
}

void RenderGlyphs(Glyphs &glyphs, RenderGlyphsFlags flags)
{
if (IsSet(flags, RenderGlyphsFlags::useCache)) { }
else { }

if (IsSet(flags, RenderGlyphsFlags::deferred)) { }
else { }

// ...

}

int main() {
Glyphs glyphs;
RenderGlyphs(glyphs, RenderGlyphsFlags::useCache | RenderGlyphsFlags::optimize);
}

结构体

struct RenderGlyphsParam
{
bool useCache;
bool deferred;
bool optimize;
bool finalRender;
};
void RenderGlyphs(Glyphs &glyphs, const RenderGlyphsParam &renderParam);

// the call:
RenderGlyphs(glyphs,
{/useCache/true,
/deferred/false,
/optimize/true,
/finalRender/false});

c++20我们有了字段构造，字段信息终于有了

struct RenderGlyphsParam
{
bool useCache;
bool deferred;
bool optimize;
bool finalRender;
};
void RenderGlyphs(Glyphs &glyphs, const RenderGlyphsParam &renderParam);

// the call:
RenderGlyphs(glyphs,
{.useCache = true,
.deferred = false,
.optimize = true,
.finalRender = false});

这个更完美一些

[Supervising in C++: how to make your programs reliable](https://basiliscos.github.io/blog/2022/02/20/supervising-in-c-how-to-make-your-programs-reliable/)[](https://github.com/wanghenshui/cppweeklynews/blob/dev/posts/051.md#%E8%A7%86%E9%A2%91)

介绍c++一些Supervise管理策略以及actor框架使用，比较少用。基本上都是糊一个taskflow模型，不用什么let it crash。这种东西放在背后的管理系统来做。不在业务进程里做
视频

C++ Weekly - Ep 312 - Stop Using constexpr (And Use This Instead!)

constexpr修饰函数，没问题

constexpr修饰值，这个值未必是编译期计算(用const可以)，取决于编译器，且 constexpr修饰的值肯定在堆栈，所以要注意作用域问题

[Keynote: C++'s Superpower - Matt Godbolt - CPPP 2021](https://www.youtube.com/watch?v=0_UttFDnV3k)

介绍周边生态

[Introduction to memory exploitation - Patricia Aas - Meeting C++ 2021](https://www.youtube.com/watch?v=s18lHhN-NXc)

讲fuzzer的工作原理

[Design of a C++ reflection API - Matúš Chochlík - Meeting C++ online](https://www.youtube.com/watch?v=BP0gsVy502w)

介绍他写的一个反射库

[The Basics of Profiling - Mathieu Ropert - CppCon 2021](https://www.youtube.com/watch?v=dToaepIXW4s)

没啥意思。讲window profile的

[Design and Implementation of Highly Scalable Quantifiable Data Structures in C++ - CppCon 2021](https://www.youtube.com/watch?v=ECWsLj0pgbI&list=PLHTh1InhhwT6vjwMy3RG5Tnahw0G9qIx6&index=74)[](https://github.com/wanghenshui/cppweeklynews/blob/dev/posts/051.md#%E5%BC%80%E6%BA%90%E9%A1%B9%E7%9B%AE%E9%9C%80%E8%A6%81%E4%BA%BA%E6%89%8B)

这讲的是个啥啊？论文在Parallel Computing Technologies这本书里，谁能搞个电子版，原版太贵了。愣是没听明白。这里标记TODO，有机会再看吧
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)[](https://github.com/wanghenshui/cppweeklynews/blob/dev/posts/051.md#%E6%96%B0%E9%A1%B9%E7%9B%AE%E4%BB%8B%E7%BB%8D%E7%89%88%E6%9C%AC%E6%9B%B4%E6%96%B0) 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

[raw pdb](https://github.com/MolecularMatters/raw_pdb) c++17一个解析pdb的库
[ledit](https://github.com/liz3/ledit) 一个编辑器
[HFSM2 development might slow down](https://www.reddit.com/r/cpp/comments/t0od6u/hfsm2_development_might_slow_down/) 乌克兰正在打仗，作为当地人无心工作
[thread-pool](https://github.com/DeveloperPaul123/thread-pool) 又一个线程池实现

实现线程池我们真正需要的是什么？是一个干活线程还是任务的投递/管理？纯纯一个线程池轮子也就看看，用处不大

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