/Zc:char8_t (Enable C++20 char8_t type)
The /Zc:char8_t compiler option enables C++20 conforming char8_t type support. char8_t is a character type that's used to represent UTF-8 code units.
Syntax
/Zc:char8_t[-]
Remarks
The /Zc:char8_t compiler option enables the char8_t type keyword as specified in the C++20 standard. It causes the compiler to generate u8 prefixed character or string literals as const char8_t or const char8_t[N] types, respectively, instead of as const char or const char[N] types. In C++17, arrays of char may be initialized using u8 string literals. In C++20, this initialization is ill-formed, and causes compiler error C2440. This behavior can be a source-breaking change. You can revert the compiler to C++14 or C++17 behavior explicitly by specifying /Zc:char8_t-.
The /Zc:char8_t option is available starting in Visual Studio 2019 version 16.1. It's enabled automatically when you specify /std:c++20 or later (such as /std:c++latest). Otherwise, it's off by default.
Example
const char* s = u8"Hello"; // Compiles in C++17, Error C2440 in C++20
const char8_t* s = u8"Hello"; // Compiles in C++20 or with /Zc:char8_t
To set this compiler option in Visual Studio
Open the project's Property Pages dialog box. For details, see Set C++ compiler and build properties in Visual Studio.
Select the Configuration Properties > C/C++ > Command Line property page.
Add
/Zc:char8_tor/Zc:char8_t-to the Additional options: pane.