字符串文字和constexpr之间的区别char数组

问题描述

我一直想知道在 ptrToArray 和 ptrToLiteral 中指向的内容之间是否有任何区别示例：

I have been wondering if there is any difference between what is being pointed by ptrToArray and ptrToLiteral in the following example:

constexpr char constExprArray[] = "hello";
const char* ptrToArray = constExprArray;

const char* ptrToLiteral = "hello";

• 我理解 constExprArray 并且两个hello文字都是编译时常数lvalue正确？




• 它们在运行时在幕后是否有不同的处理方式？


• 还要了解什么？


• Is my understanding that constExprArray and the two "hello" literals are all compile time constant lvalues correct?
• If so, is there any difference in how they are stored in the executable file, or is it purely compiler implementation or platform specific?
• Are they treated differently at runtime behind the scenes?
• Anything else to know about?

推荐答案

字符串文字和constexpr数组几乎相同。指向它的指针是地址常量表达式。允许在常量表达式中对其元素进行左值到右值转换。它们都有静态存储持续时间。我知道的唯一的区别是，一个字符串文字可以初始化数组，而constexpr数组不能：

A string literal and a constexpr array of char are almost identical. A pointer to either is an address constant expression. An lvalue-to-rvalue conversion is permitted on their elements in a constant expression. They both have static storage duration. The only difference that I know of is that a string literal can initialize an array whereas a constexpr array cannot:

constexpr char a[] = "hello";

constexpr char b[] = a; // ill-formed
constexpr char b[] = "hello"; // ok

为了解决这个问题，你可以将数组包装在一个类型的文字类型中。我们目前正在考虑标准化这样一个包装器，它将被称为 std :: string_literal 或类似的，但现在你必须手动这样做。

To get around this you can wrap the array in a class of literal type. We are currently looking at standardizing such a wrapper that will be called std::string_literal or similar, but for now you will have to do this by hand.

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