问题描述
此问题是对。
旧式常量有几种形式，尤其是：
Legacy constants come in several forms, notably:
-
#define CONSTANT x -
enum {CONSTANT = x}; -
const / * int / unsigned / whatever * / CONSTANT = x;
#define CONSTANT xenum { CONSTANT = x };const /*int/unsigned/whatever*/ CONSTANT = x;
关于静态constexpr 和 inline constexpr 常量的评论作为替换得到了我在考虑更新许多旧式常量（尤其是 #define 常量）的主题。
A comment about static constexpr and inline constexpr constants as a replacement got me thinking on the subject of updating our many, many legacy constants (particularly #define constants).
可以理解，内联constexpr 值基本上只是被替换，就像内联函数一样（我被证明是错误的）。相反，静态constexpr 值作为二进制文件的一部分存储在单独的区域中。假设我理解正确，什么时候应该优先选择另一个？我的直觉是，对于整数常量，通常首选内联constexpr 。
As I understand, an inline constexpr value is basically just substituted in place, like an inlined function (which I've been shown to be wrong about). Conversely, a static constexpr value is stored as part of the binary in a separate area. Assuming I understand correctly, when should one be preferred over the other? My hunch is that, for integral constants, inline constexpr will generally be preferred.
推荐答案
在C ++ 17中，替换名称空间范围标头中的那些旧习惯用法（例如 #define ）的正确方法是使用 constexpr内联变量-和 not static （这意味着：它们已经具有内部链接）了。
In C++17, the proper way to replace those old idioms (e.g. #define) in headers in namespace scope is to use constexpr inline variables -- and not static (which is implied: they already have internal linkage).
虽然通常不会遇到ODR问题（因为您所描述的整数编译时常数很少使用ODR，并且在 inline 函数），现在最好将它们标记为 inline ，因为我们已经使用了该功能并避免了所有问题。
While typically you won't encounter ODR issues (because integer compile-time constants such as those you describe are rarely ODR-used and there is a provision for their typical usage within inline functions), it is best to mark them as inline now that we have the feature in the language and avoid all problems.
请参见以获得有关它的技术详细信息。
See Should `const` and `constexpr` variables in headers be `inline` to prevent ODR violations? for the technical details about it.
这篇关于替换常量：什么时候使用静态constexpr和内联constexpr？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！