/std (Specify Language Standard Version)

Enable supported C and C++ language features from the specified version of the C or C++ language standard.

Syntax

/std:c++14
/std:c++17
/std:c++20
/std:c++latest
/std:c11
/std:c17

Remarks

The /std options are available in Visual Studio 2017 and later. They're used to control the version-specific ISO C or C++ programming language standard features enabled during compilation of your code. The options allow you to disable support for certain new language and library features: ones that may break your existing code that conforms to a particular version of the language standard.

C++ standards support

The /std option in effect during a C++ compilation can be detected by use of the _MSVC_LANG preprocessor macro. For more information, see Preprocessor Macros.

/std:c++14
The /std:c++14 option enables C++14 standard-specific features implemented by the MSVC compiler. This option is the default for code compiled as C++. It's available starting in Visual Studio 2015 Update 3.

This option disables compiler and standard library support for features that are changed or new in more recent versions of the language standard. However, it doesn't disable some C++17 features already implemented in previous releases of the MSVC compiler. For more information, see Microsoft C/C++ language conformance. The tables indicate which C++17 features are enabled when you specify /std:c++14.

The following features remain enabled when the /std:c++14 option is specified to avoid breaking changes for users who have already taken dependencies on the features available in or before Visual Studio 2015 Update 2:

/std:c++17
The /std:c++17 option enables C++17 standard-specific features and behavior. It enables the full set of C++17 features implemented by the MSVC compiler. This option disables compiler and standard library support for features that are new or changed after C++17. It specifically disables post-C++17 changes in the C++ Standard and versions of the Working Draft. It does not disable retroactive defect updates of the C++ Standard. This option is available starting in Visual Studio 2017 version 15.3.

Depending on the MSVC compiler version or update level, C++17 features may not be fully implemented or fully conforming when you specify the /std:c++17 option. For an overview of C++ language conformance in Visual C++ by release version, see Microsoft C/C++ language conformance.

/std:c++20
The /std:c++20 option enables C++20 standard-specific features and behavior. Available starting in Visual Studio 2019 version 16.11, it enables the full set of C++20 features implemented by the MSVC compiler, with the exception of std::format, the C++20 <chrono> formatting extensions, and the range factories and range adaptors from <ranges>. These features are still only available under /std:c++latest.

The /std:c++20 option disables compiler and standard library support for features that are new or changed after C++20. It specifically disables post-C++20 changes in the C++ Standard and versions of the Working Draft. It doesn't disable retroactive defect updates of the C++ Standard.

/std:c++latest
The /std:c++latest option enables all currently implemented compiler and standard library features proposed for the next draft standard, as well as some in-progress and experimental features. This option is available starting in Visual Studio 2015 Update 3.

Depending on the MSVC compiler version or update level, C++17, C++20, or proposed C++23 features may not be fully implemented or fully conforming when you specify the /std:c++latest option. We recommend you use the latest version of Visual Studio for maximum standards conformance. For an overview of C++ language and library conformance in Visual C++ by release version, see Microsoft C/C++ language conformance.

In versions of Visual Studio 2019 before version 16.11, /std:c++latest is required to enable all the compiler and standard library features of C++20.

For a list of supported language and library features, see What's New for C++ in Visual Studio.

The /std:c++latest option doesn't enable features guarded by the /experimental switch, but may be required to enable them.

Note

The compiler and library features enabled by /std:c++latest may appear in a future C++ standard. Features that have not been approved are subject to breaking changes or removal without notice and are provided on an as-is basis.

C standards support

You can invoke the Microsoft C compiler by using the /TC or /Tc compiler option. It's used by default for code that has a .c file extension, unless overridden by a /TP or /Tp option. The default C compiler (that is, the compiler when /std:c11 or /std:c17 isn't specified) implements ANSI C89, but includes several Microsoft extensions, some of which are part of ISO C99. Some Microsoft extensions to C89 can be disabled by using the /Za compiler option, but others remain in effect. It isn't possible to specify strict C89 conformance. The compiler doesn't implement several required features of C99, so it isn't possible to specify C99 conformance, either.

/std:c11
The /std:c11 option enables ISO C11 conformance. It's available starting in Visual Studio 2019 version 16.8.

/std:c17
The /std:c17 option enables ISO C17 conformance. It's available starting in Visual Studio 2019 version 16.8.

Because the new preprocessor is needed to support these standards, the /std:c11 and /std:c17 compiler options set the /Zc:preprocessor option automatically. If you want to use the traditional (legacy) preprocessor for C11 or C17, you must set the /Zc:preprocessor- compiler option explicitly. Setting the /Zc:preprocessor- option may lead to unexpected behavior, and isn't recommended.

Note

At the time of release and through Visual Studio 2019 version 16.10, the Windows SDK and UCRT libraries installed by Visual Studio don't yet support C11 and C17 code. An updated version of the Windows SDK and UCRT is required. For more information and installation instructions, see Install C11 and C17 support in Visual Studio.

When you specify /std:c11 or /std:c17, MSVC supports all the features of C11 and C17 required by the standards. The /std:c11 and /std:c17 compiler options enable support for these functionalities:

The IDE uses C settings for IntelliSense and code highlighting when your source files have a .c file extension, or when you specify the /TC or /Tc compiler option. Currently, IntelliSense in C highlights keywords _Alignas, _Alignof, _Noreturn, and _Static_assert, but not the equivalent macros defined in the standard headers: alignas, alignof, noreturn, and static_assert.

Since C17 is largely a bug-fix release of ISO C11, MSVC support for C11 already includes all the relevant defect reports. There are no differences between the C11 and C17 versions except for the __STDC_VERSION__ macro. It expands to 201112L for C11, and 201710L for C17.

The compiler doesn't support most optional features of ISO C11. Several of these optional features of C11 were required features of C99 that MSVC hasn't implemented for architectural reasons. You can use the feature test macros such as __STDC_NO_VLA__ to detect compiler support levels for individual features. For more information about C-specific predefined macros, see Predefined macros.

  • There's no conforming multithreading, atomic, or complex number support.

  • aligned_alloc support is missing, because of the Windows heap implementation. The alternative is to use _aligned_malloc.

  • DR 400 support is currently unimplemented for realloc, because this change would break the ABI.

  • Variable length array (VLA) support isn't planned. VLAs provide attack vectors comparable to gets, which is deprecated and planned for removal.

For more information, see the C Standard library features section of Microsoft C/C++ language conformance.

To set this compiler option in the Visual Studio development environment

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

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

  3. In C++ Language Standard (or for C, C Language Standard), choose the language standard to support from the dropdown control, then choose OK or Apply to save your changes.

See also

MSVC compiler options
MSVC compiler command-line syntax