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/Zc:char8_t (Enable C++20 char8_t type)

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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

  1. Open the project's Property Pages dialog box. For details, see Set C++ compiler and build properties in Visual Studio.

  2. Select the Configuration Properties > C/C++ > Command Line property page.

  3. Add /Zc:char8_t or /Zc:char8_t- to the Additional options: pane.

See also

/Zc (Conformance)
/std (Specify language standard version)