C++核心准则ES.27:使用std::array或者stack_array在堆栈上构建数组

ES.27: Use std::array or stack_array for arrays on the stack

ES.27:使用std::array或者stack_array在堆栈上构建数组

Reason（原因）

They are readable and don't implicitly convert to pointers. They are not confused with non-standard extensions of built-in arrays.

它们的可读性好，而且不会隐式转换为指针类型。它们不会和内置数组的非标准扩展相混淆。

Example, bad（反面示例）

const int n = 7;
int m = 9;
void f()
{    
int a1[n];    
int a2[m];   // error: not ISO C++    
// ...
}

Note（注意）

The definition of a1 is legal C++ and has always been. There is a lot of such code. It is error-prone, though, especially when the bound is non-local. Also, it is a "popular" source of errors (buffer overflow, pointers from array decay, etc.). The definition of a2 is C but not C++ and is considered a security risk.

a1的定义是一直都是合法的C++语法。存在很多这样的代码。虽然它容易出错误，特别是边界不是局部变量时。同时它也是很多错误的常见原因（缓冲区溢出，退化数组的指针等）。a2是C语法而不是C++语法。在C++中被认为存在安全风险。

Example（示例）

const int n = 7;
int m = 9;

void f()
{
    array<int, n> a1;
    stack_array<int> a2(m);
    // ...
}

Enforcement（实施建议）

• Flag arrays with non-constant bounds (C-style VLAs)
• 标记变长数组（C风格不定长数组）
• Flag arrays with non-local constant bounds
• 标记非局部常量定义长度的数组。

链接

https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#es27-use-stdarray-or-stack_array-for-arrays-on-the-stack