From 5de0fdeb6f821bce0fd54bb2e6dda9d11ec1fe16 Mon Sep 17 00:00:00 2001 From: li-zhou <2181719471@qq.com> Date: Tue, 23 Jun 2026 23:10:22 +0800 Subject: [PATCH] feat(cpp14): add 08-aggregate-nsdmi MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Book chapter (zh + en): - section 一/I: Basic usage — struct with defaults, partial init - section 二/II: Real-world case — _Iterator_base12_compatible from msvc-stl/stl/inc/array#L20-L23 - section 三/III: Notes — NSDMI only when no initializer provided - section 四/IV: Exercise topics and d2x checker command - section 五/V: External resources Exercise: 0. Vec3 struct with NSDMI, partial and full aggregate init. 3 D2X_YOUR_ANSWER. Build wiring: - register 08 target in dslings/cpp14, dslings/en/cpp14, solutions/cpp14 - add 08 entry to zh/en SUMMARY.md --- book/en/src/SUMMARY.md | 1 + book/en/src/cpp14/08-aggregate-nsdmi.md | 72 +++++++++++++++++++++++ book/src/SUMMARY.md | 1 + book/src/cpp14/08-aggregate-nsdmi.md | 72 +++++++++++++++++++++++ dslings/cpp14/08-aggregate-nsdmi-0.cpp | 44 ++++++++++++++ dslings/cpp14/xmake.lua | 6 ++ dslings/en/cpp14/08-aggregate-nsdmi-0.cpp | 45 ++++++++++++++ dslings/en/cpp14/xmake.lua | 6 ++ solutions/cpp14/08-aggregate-nsdmi-0.cpp | 29 +++++++++ solutions/cpp14/xmake.lua | 6 ++ 10 files changed, 282 insertions(+) create mode 100644 book/en/src/cpp14/08-aggregate-nsdmi.md create mode 100644 book/src/cpp14/08-aggregate-nsdmi.md create mode 100644 dslings/cpp14/08-aggregate-nsdmi-0.cpp create mode 100644 dslings/en/cpp14/08-aggregate-nsdmi-0.cpp create mode 100644 solutions/cpp14/08-aggregate-nsdmi-0.cpp diff --git a/book/en/src/SUMMARY.md b/book/en/src/SUMMARY.md index b2008be..2a8581f 100644 --- a/book/en/src/SUMMARY.md +++ b/book/en/src/SUMMARY.md @@ -31,6 +31,7 @@ # C++14 Core Language Features - [Generic Lambdas](./cpp14/00-generic-lambdas.md) +- [Aggregate NSDMI](./cpp14/08-aggregate-nsdmi.md) # Additional Resources diff --git a/book/en/src/cpp14/08-aggregate-nsdmi.md b/book/en/src/cpp14/08-aggregate-nsdmi.md new file mode 100644 index 0000000..c2ad002 --- /dev/null +++ b/book/en/src/cpp14/08-aggregate-nsdmi.md @@ -0,0 +1,72 @@ +
+ + 🌎 [中文] | [English] +
+ +[中文]: ../../cpp14/08-aggregate-nsdmi.html +[English]: ./08-aggregate-nsdmi.html + +# Aggregate NSDMI Initialization + +C++14 relaxes aggregate restrictions — classes with non-static data member initializers (NSDMI) can still be aggregates + +| Book | Video | Code | X | +| --- | --- | --- | --- | +| [cppreference-aggregate_initialization](https://en.cppreference.com/w/cpp/language/aggregate_initialization) / [markdown](https://github.com/mcpp-community/d2mcpp/blob/main/book/en/src/cpp14/08-aggregate-nsdmi.md) | [Video Explanation]() | [Exercise Code](https://github.com/mcpp-community/d2mcpp/blob/main/dslings/en/cpp14/08-aggregate-nsdmi-0.cpp) | | + + +**Why introduced?** + +In C++11, a class with any NSDMI (`int x = 0;`) lost its aggregate status, breaking `{}` initialization. C++14 fixes this contradiction + +## I. Basic Usage and Scenarios + +```cpp +struct Point { + int x = 0; // NSDMI + int y = 0; +}; + +Point p1{3, 4}; // C++14: aggregate initialization OK +Point p2{1}; // y uses default 0 +Point p3{}; // x=0, y=0 +``` + +## II. Real-World Case — Aggregate + NSDMI in the STL + +> The MSVC STL uses aggregates with NSDMI internally. The example below cites the vendored [MSVC STL](https://github.com/mcpp-community/d2mcpp/tree/main/msvc-stl) (source: [`msvc-stl/stl/inc/array`](https://github.com/mcpp-community/d2mcpp/blob/main/msvc-stl/stl/inc/array#L20-L23)) + +```cpp +// MSVC STL · msvc-stl/stl/inc/array (abridged) +struct _Iterator_base12_compatible { + _Container_proxy* _Myproxy{}; + _Iterator_base12* _Mynextiter{}; +}; +``` + +Both members have `{}` default initializers, yet the type participates in iterator base class inheritance and initialization as an aggregate — relying on C++14's NSDMI aggregate relaxation + +## III. Notes + +- NSDMI values are only used when no initializer is provided +- `{}` initialization values override NSDMI defaults +- Aggregate members must all be public + +## IV. Exercise Code + +### Exercise Topics + +- 0 - [Aggregate NSDMI — Class with Default Members and Aggregate Init](https://github.com/mcpp-community/d2mcpp/blob/main/dslings/en/cpp14/08-aggregate-nsdmi-0.cpp) + +### Auto-Checker Command + +``` +d2x checker aggregate-nsdmi +``` + +## V. Other + +- [Discussion Forum](https://forum.d2learn.org/category/20) +- [d2mcpp Tutorial Repository](https://github.com/mcpp-community/d2mcpp) +- [Tutorial Video List](https://space.bilibili.com/65858958/lists/5208246) +- [Tutorial Support Tool - xlings](https://github.com/openxlings/xlings) diff --git a/book/src/SUMMARY.md b/book/src/SUMMARY.md index 7efe83a..053e273 100644 --- a/book/src/SUMMARY.md +++ b/book/src/SUMMARY.md @@ -31,6 +31,7 @@ # C++14核心语言特性 - [泛型 lambda - generic lambdas](./cpp14/00-generic-lambdas.md) +- [聚合 NSDMI - aggregate NSDMI](./cpp14/08-aggregate-nsdmi.md) # 其他 diff --git a/book/src/cpp14/08-aggregate-nsdmi.md b/book/src/cpp14/08-aggregate-nsdmi.md new file mode 100644 index 0000000..0a0c7a0 --- /dev/null +++ b/book/src/cpp14/08-aggregate-nsdmi.md @@ -0,0 +1,72 @@ +
+ + 🌎 [中文] | [English] +
+ +[中文]: ./08-aggregate-nsdmi.html +[English]: ../en/cpp14/08-aggregate-nsdmi.html + +# 聚合初始化与 NSDMI + +C++14 放宽了聚合类型的限制: 拥有非静态数据成员初始化器 (NSDMI) 的类仍然可以是聚合, 可以使用 `{}` 初始化 + +| Book | Video | Code | X | +| --- | --- | --- | --- | +| [cppreference-aggregate_initialization](https://en.cppreference.com/w/cpp/language/aggregate_initialization) / [markdown](https://github.com/mcpp-community/d2mcpp/blob/main/book/src/cpp14/08-aggregate-nsdmi.md) | [视频解读]() | [练习代码](https://github.com/mcpp-community/d2mcpp/blob/main/dslings/cpp14/08-aggregate-nsdmi-0.cpp) | | + + +**为什么引入?** + +C++11 中, 只要类有 NSDMI (`int x = 0;`), 它就不再是聚合, `{}` 初始化失效。这导致给简单数据结构加默认值后反而不能用简洁的聚合初始化。C++14 修复了这个矛盾 + +## 一、基础用法和场景 + +```cpp +struct Point { + int x = 0; // NSDMI + int y = 0; +}; + +Point p1{3, 4}; // C++14: OK, 聚合初始化 +Point p2{1}; // y 使用默认值 0 +Point p3{}; // x=0, y=0 +``` + +## 二、真实案例 - STL 中的聚合 + NSDMI + +> MSVC STL 内部大量使用带 NSDMI 的聚合类型。下面以仓库内置的 [MSVC STL](https://github.com/mcpp-community/d2mcpp/tree/main/msvc-stl) 为例 (源码: [`msvc-stl/stl/inc/array`](https://github.com/mcpp-community/d2mcpp/blob/main/msvc-stl/stl/inc/array#L20-L23)) + +```cpp +// MSVC STL · msvc-stl/stl/inc/array (有删节) +struct _Iterator_base12_compatible { + _Container_proxy* _Myproxy{}; + _Iterator_base12* _Mynextiter{}; +}; +``` + +两个成员都有 `{}` 默认初始化, 但该类型仍以聚合形式参与迭代器基类的多重继承和初始化, 依赖的正是 C++14 对聚合 NSDMI 的放宽 + +## 三、注意事项 + +- NSDMI 的值只在没有提供对应初始化器时使用 +- `{}` 初始化的值会覆盖 NSDMI 默认值 +- 聚合的成员必须全部为 public + +## 四、练习代码 + +### 练习代码主题 + +- 0 - [聚合 NSDMI — 带默认成员的类聚合初始化](https://github.com/mcpp-community/d2mcpp/blob/main/dslings/cpp14/08-aggregate-nsdmi-0.cpp) + +### 练习代码自动检测命令 + +``` +d2x checker aggregate-nsdmi +``` + +## 五、其他 + +- [交流讨论](https://forum.d2learn.org/category/20) +- [d2mcpp教程仓库](https://github.com/mcpp-community/d2mcpp) +- [教程视频列表](https://space.bilibili.com/65858958/lists/5208246) +- [教程支持工具-xlings](https://github.com/openxlings/xlings) diff --git a/dslings/cpp14/08-aggregate-nsdmi-0.cpp b/dslings/cpp14/08-aggregate-nsdmi-0.cpp new file mode 100644 index 0000000..355a702 --- /dev/null +++ b/dslings/cpp14/08-aggregate-nsdmi-0.cpp @@ -0,0 +1,44 @@ +// d2mcpp: https://github.com/mcpp-community/d2mcpp +// license: Apache-2.0 +// file: dslings/cpp14/08-aggregate-nsdmi-0.cpp +// +// Exercise/练习: cpp14 | 08 - aggregate NSDMI | 聚合 + 默认成员初始化 +// +// Tips/提示: +// - C++14 允许带 NSDMI 的类保持聚合身份 +// - 聚合初始化时提供的值覆盖默认值, 未提供的使用 NSDMI 默认值 +// +// Docs/文档: +// - https://en.cppreference.com/w/cpp/language/aggregate_initialization +// - https://github.com/mcpp-community/d2mcpp/blob/main/book/src/cpp14/08-aggregate-nsdmi.md +// +// 练习交流讨论: http://forum.d2learn.org/category/20 +// +// Auto-Checker/自动检测命令: +// +// d2x checker aggregate-nsdmi +// + +#include + +struct Vec3 { + float x = 0.0f; + D2X_YOUR_ANSWER y = 0.0f; + float z = 0.0f; +}; + +int main() { + + Vec3 v1{1.0f, 2.0f, 3.0f}; + d2x_assert_eq(v1.x, 1.0f); + d2x_assert_eq(v1.z, 3.0f); + + Vec3 v2{4.0f, D2X_YOUR_ANSWER}; + d2x_assert_eq(v2.x, 4.0f); + d2x_assert_eq(v2.y, 5.0f); + d2x_assert_eq(v2.z, D2X_YOUR_ANSWER); + + D2X_WAIT + + return 0; +} diff --git a/dslings/cpp14/xmake.lua b/dslings/cpp14/xmake.lua index 8a21cbf..6ea44c5 100644 --- a/dslings/cpp14/xmake.lua +++ b/dslings/cpp14/xmake.lua @@ -9,3 +9,9 @@ target("cpp14-00-generic-lambdas-0") target("cpp14-00-generic-lambdas-1") set_kind("binary") add_files("00-generic-lambdas-1.cpp") + +-- target: cpp14-08-aggregate-nsdmi + +target("cpp14-08-aggregate-nsdmi-0") + set_kind("binary") + add_files("08-aggregate-nsdmi-0.cpp") diff --git a/dslings/en/cpp14/08-aggregate-nsdmi-0.cpp b/dslings/en/cpp14/08-aggregate-nsdmi-0.cpp new file mode 100644 index 0000000..17d549a --- /dev/null +++ b/dslings/en/cpp14/08-aggregate-nsdmi-0.cpp @@ -0,0 +1,45 @@ +// d2mcpp: https://github.com/mcpp-community/d2mcpp +// license: Apache-2.0 +// file: dslings/en/cpp14/08-aggregate-nsdmi-0.cpp +// +// Exercise: cpp14 | 08 - aggregate NSDMI | aggregate + default member init +// +// Tips: +// - C++14 allows classes with NSDMI to remain aggregates +// - Values provided in aggregate init override defaults; missing values +// use NSDMI defaults +// +// Docs: +// - https://en.cppreference.com/w/cpp/language/aggregate_initialization +// - https://github.com/mcpp-community/d2mcpp/blob/main/book/en/src/cpp14/08-aggregate-nsdmi.md +// +// Discussion Forum: http://forum.d2learn.org/category/20 +// +// Auto-Checker: +// +// d2x checker aggregate-nsdmi +// + +#include + +struct Vec3 { + float x = 0.0f; + D2X_YOUR_ANSWER y = 0.0f; + float z = 0.0f; +}; + +int main() { + + Vec3 v1{1.0f, 2.0f, 3.0f}; + d2x_assert_eq(v1.x, 1.0f); + d2x_assert_eq(v1.z, 3.0f); + + Vec3 v2{4.0f, D2X_YOUR_ANSWER}; + d2x_assert_eq(v2.x, 4.0f); + d2x_assert_eq(v2.y, 5.0f); + d2x_assert_eq(v2.z, D2X_YOUR_ANSWER); + + D2X_WAIT + + return 0; +} diff --git a/dslings/en/cpp14/xmake.lua b/dslings/en/cpp14/xmake.lua index 8a21cbf..6ea44c5 100644 --- a/dslings/en/cpp14/xmake.lua +++ b/dslings/en/cpp14/xmake.lua @@ -9,3 +9,9 @@ target("cpp14-00-generic-lambdas-0") target("cpp14-00-generic-lambdas-1") set_kind("binary") add_files("00-generic-lambdas-1.cpp") + +-- target: cpp14-08-aggregate-nsdmi + +target("cpp14-08-aggregate-nsdmi-0") + set_kind("binary") + add_files("08-aggregate-nsdmi-0.cpp") diff --git a/solutions/cpp14/08-aggregate-nsdmi-0.cpp b/solutions/cpp14/08-aggregate-nsdmi-0.cpp new file mode 100644 index 0000000..7a2b602 --- /dev/null +++ b/solutions/cpp14/08-aggregate-nsdmi-0.cpp @@ -0,0 +1,29 @@ +// d2mcpp: https://github.com/mcpp-community/d2mcpp +// license: Apache-2.0 +// reference solution for: dslings/cpp14/08-aggregate-nsdmi-0.cpp +// +// 用途: 仅给 CI 与维护者参考使用，不是教程入口。 +// 教程练习入口: dslings/cpp14/08-aggregate-nsdmi-0.cpp +// + +#include + +struct Vec3 { + float x = 0.0f; + float y = 0.0f; + float z = 0.0f; +}; + +int main() { + + Vec3 v1{1.0f, 2.0f, 3.0f}; + d2x_assert_eq(v1.x, 1.0f); + d2x_assert_eq(v1.z, 3.0f); + + Vec3 v2{4.0f, 5.0f}; + d2x_assert_eq(v2.x, 4.0f); + d2x_assert_eq(v2.y, 5.0f); + d2x_assert_eq(v2.z, 0.0f); + + return 0; +} diff --git a/solutions/cpp14/xmake.lua b/solutions/cpp14/xmake.lua index 8bbbb90..9c406a4 100644 --- a/solutions/cpp14/xmake.lua +++ b/solutions/cpp14/xmake.lua @@ -9,3 +9,9 @@ target("cpp14-00-generic-lambdas-0-ref") target("cpp14-00-generic-lambdas-1-ref") set_kind("binary") add_files("00-generic-lambdas-1.cpp") + +-- target: cpp14-08-aggregate-nsdmi + +target("cpp14-08-aggregate-nsdmi-0-ref") + set_kind("binary") + add_files("08-aggregate-nsdmi-0.cpp")