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/std (Specify Language Standard Version) |
The MSVC compiler option /std specifies the C or C++ language standard supported by the compiler. |
10/29/2020 |
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0acb74ba-1aa8-4c05-b96c-682988dc19bd |
Enable supported C and C++ language features from the specified version of the C or C++ language standard.
/std:c++14
/std:c++17
/std:c++latest
/std:c11
/std:c17
The /std option is available in Visual Studio 2017 and later. It's used to control the version-specific ISO C or C++ programming language standard features enabled during compilation of your code. This option allows 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.
By default, /std:c++14 is specified, which disables language and standard library features found in later versions of the C++ language standard. Use /std:c++17 to enable C++17 standard-specific features and behavior. To explicitly enable the currently implemented compiler and standard library features proposed for the next draft standard, use /std:c++latest. All C++20 features require /std:c++latest; when the implementation is complete, a new /std:c++20 option will be enabled.
The default /std:c++14 option enables the set of C++14 features implemented by the MSVC compiler. This option disables compiler and standard library support for features that are changed or new in more recent versions of the language standard. It doesn't disable some C++17 features already implemented in previous releases of the MSVC compiler. To avoid breaking changes for users who have already taken dependencies on the features available in or before Visual Studio 2015 Update 2, these features remain enabled when the /std:c++14 option is specified:
A list of which C++14 and C++17 features are enabled when you specify /std:c++14 is available. For more information, see the notes in Microsoft C++ language conformance table.
The /std:c++17 option 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. That includes post-C++17 changes in versions of the Working Draft and defect updates of the C++ Standard.
The /std:c++latest option enables the post-C++17 language and library features currently implemented in the compiler and libraries. These features may include changes from the C++20 Working Draft, defect updates that aren't included in C++17, and experimental proposals for the draft standard. For a list of supported language and library features, see What's New for Visual C++. The /std:c++latest option doesn't enable features guarded by the /experimental switch, but may be required to enable them.
Important
The compiler and library features enabled by /std:c++latest represent features that may appear in a future C++ standard, as well as C++20 features that are approved. Features that have not been approved are subject to breaking changes or removal without notice and are provided on an as-is basis.
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.
The /std:c++14 and /std:c++latest options are available beginning in Visual Studio 2015 Update 3. The /std:c++17 option is available beginning in Visual Studio 2017 version 15.3. As noted above, some C++17 standard behavior is enabled by the /std:c++14 option, but all other C++17 features are enabled by /std:c++17. C++20 features are enabled by /std:c++latest until the implementation is complete.
Note
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 options. For an overview of C++ language conformance in Visual C++ by release version, see Microsoft C++ language conformance table.
By default, when code is compiled as C, the MSVC compiler doesn't conform to a particular C standard. It implements ANSI C89 with several Microsoft extensions, some of which are part of ISO C99. Some Microsoft extensions can be disabled by using the /Za compiler option, but others remain in effect. It isn't possible to specify strict C89 conformance.
Starting in Visual Studio 2019 version 16.8, you may specify /std:c11 or /std:c17 for code compiled as C. These options specify conformance modes that correspond with ISO C11 and ISO C17. 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, the latest Windows SDK and UCRT libraries do not yet support C11 and C17 code. A pre-release 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 required features of C11 and C17. The compiler options enable support for these functionalities:
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restrict -
_Noreturnand <stdnoreturn.h> -
_Alignas,_Alignofand <stdalign.h> -
_Genericand <tgmath.h> -
_Static_assert
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 compiler option. Currently, IntelliSense highlighting is only available for keywords, and not the macros introduced by the standard headers.
Since C17 is largely a bug fix release of ISO C11, MSVC support for C11 already includes all the relevant defect reports. At present, 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 any 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.
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There's no conforming multithreading, atomic, or complex number support in the Visual Studio 2019 version 16.8 release.
-
aligned_allocsupport 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. Variable length arrays are often less efficient than comparable fixed sized arrays. They're also inefficient compared to equivalent heap memory allocations, when safely and securely implemented. VLAs provide attack vectors comparable to
gets(), which is deprecated and planned for removal.
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Open the project's Property Pages dialog box. For details, see Set C++ compiler and build properties in Visual Studio.
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Select the Configuration Properties > C/C++ > Language property page.
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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.