Can std::string Be Used in Constant Expressions in C ?

Using std::string in Constant Expressions

It is generally not possible to employ std::string in constant expressions. The reason for this is that std::string has a non-trivial destructor, making its use incompatible with the requirement of constant expressions to be resolved at compile time.

C 20 Solution

However, with C 20, a limited exception has been introduced. If a std::string is destroyed before the end of constant evaluation, it can be used in constant expressions. For example:

constexpr std::size_t n = std::string("hello, world").size();

In this instance, the std::string is created and destroyed within the constant expression, so its use is permissible.

Alternative Solution (C 17 and Later)

A practical alternative to std::string for use in constant expressions is std::string_view. A string_view is an immutable, non-owning reference to a character sequence. It provides similar functionality to std::string, but without a destructor, making it suitable for constant expressions:

constexpr std::string_view sv = "hello, world";

The above is the detailed content of Can std::string Be Used in Constant Expressions in C ?. For more information, please follow other related articles on the PHP Chinese website!