The CL tool uses the following environment variables:

- CL and \_CL\_, if defined. The CL tool inserts the options and arguments defined in the CL environment variable at the beginning of the command line arguments, and adds the options and arguments defined in \_CL\_ to the end of the command line arguments, before processing.

- INCLUDE, which must point to the \include subdirectory of your Visual C++ installation.

- LIBPATH, which specifies directories to search for metadata files referenced by a `#using` directive. See [#using](../../preprocessor/hash-using-directive-cpp.md) for more information on LIBPATH.

You can set the CL or \_CL\_ environment variables using the following syntax:

```

```

For details on the arguments to the CL and \_CL\_ environment variables, see [Compiler Command-Line Syntax](../../build/reference/compiler-command-line-syntax.md).

You can use these environment variables to define the files and options you use most often and use the command line to define specific files and options for specific purposes. The CL and \_CL\_ environment variables are limited to 1024 characters (the command-line input limit).

You cannot use the /D option to define a symbol that uses an equal sign (=). You can substitute the number sign (#) for an equal sign. In this way, you can use the CL or \_CL\_ environment variables to define preprocessor constants with explicit values; for example, `/DDEBUG#1` to define `DEBUG=1`.

For related information, see [Set Environment Variables](../../build/setting-the-path-and-environment-variables-for-command-line-builds.md).

The following is an example of setting the CL environment variable:

```

```

When this environment variable is set, if you enter `CL INPUT.C` at the command line, this is the effective command:

```

```

The following example causes a plain CL command to compile the source files FILE1.c and FILE2.c, and then link the object files FILE1.obj, FILE2.obj, and FILE3.obj:

```

```

This has the same effect as the following command line:

```

```

1. Open the project's **Property Pages** dialog box. For details, see [Setting Visual C++ Project Properties](../../ide/working-with-project-properties.md).

2. Click the **Linker** folder.

3. Click the **System** property page.

4. Modify the **Driver** property.

1. See <xref:Microsoft.VisualStudio.VCProjectEngine.VCLinkerTool.driver>.

Causes the compiler to display the full path of source code files passed to the compiler in diagnostics.

```

```

Consider the following code sample:

```

```

Without **/FC**, the diagnostic text would look similar to this diagnostic text:

- compiler_option_FC.cpp(5) : error C2143: syntax error : missing ';' before '}'

With **/FC**, the diagnostic text would look similar to this diagnostic text:

- c:\test\compiler_option_FC.cpp(5) : error C2143: syntax error : missing ';' before '}'

**/FC** is also needed if you want to see the full path of a file name when using the __FILE\_\_ macro. See [Predefined Macros](../../preprocessor/predefined-macros.md) for more information on \__FILE\_\_.

The **/FC** option is implied by **/ZI**. For more information about **/ZI**, see [/Z7, /Zi, /ZI (Debug Information Format)](../../build/reference/z7-zi-zi-debug-information-format.md).

1. Open the project's **Property Pages** dialog box. For details, see [Working with Project Properties](../../ide/working-with-project-properties.md).

2. Expand the **Configuration Properties** node.

3. Expand the **C/C++** node.

4. Select the **Advanced** property page.

5. Modify the **Use Full Paths** property.

1. See <xref:Microsoft.VisualStudio.VCProjectEngine.VCCLCompilerTool.UseFullPaths%2A>.

[Compiler Options](../../build/reference/compiler-options.md)

[Setting Compiler Options](../../build/reference/setting-compiler-options.md)

ms.date: "11/04/2016"

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

```

```

The **/std** option is used to control the version-specific ISO 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 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. To explicitly enable the latest supported compiler and standard library features, use **/std:c++latest**.

The default **/std:c++14** option enables the set of C++14 features implemented by the Visual C++ compiler. This option disables compiler and standard library support for features that are changed or new in more recent versions of the language standard, with the exception of some C++17 features already implemented in previous releases of the Visual C++ compiler. To avoid breaking changes for users who have already taken dependencies on the features available as of Visual Studio 2015 Update 2, these features remain enabled when the **/std:c++14** option is specified:

- [Rules for auto with braced-init-lists](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3922.html)

- [typename in template template-parameters](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4051.html)

- [Removing trigraphs](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4086.html)

- [Attributes for namespaces and enumerators](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4266.html)

- [u8 character literals](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4267.html)

The **/std:c++17** option enables the full set of C++17 features implemented by the Visual C++ compiler. This option disables compiler and standard library support for features that are changed or new in versions of the Working Draft and defect updates of the C++ Standard after C++17.

The **/std:c++latest** option enables the set of C++ language and library features implemented by Visual C++ to track the most recent Working Draft and defect updates of the C++ Standard. Use this switch to get the latest language features supported by the compiler. For a list of supported language and library features, see [What's New for Visual C++](../../what-s-new-for-visual-cpp-in-visual-studio.md). The **/std:c++latest** option does not enable features guarded by the **/experimental** switch.

The **/std** option in effect during a C++ compilation can be detected by use of the [\_MSVC\_LANG](../preprocessor/predefined-macros.md) preprocessor macro. For more information, see [Preprocessor Macros](../preprocessor/predefined-macros.md).

The **/std:c++14** and **/std:c++latest** options are available beginning in Visual C++ 2015 Update 3. The **/std:c++17** option is available beginning in Visual C++ 2017 Update Version 15.3.

[!NOTE]

1. Open the project's **Property Pages** dialog box. For details, see [Working with Project Properties](../../ide/working-with-project-properties.md).

2. Select **Configuration Properties**, **C/C++**, **Language**.

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

[Setting Compiler Options](../../build/reference/setting-compiler-options.md)

|__p\_\__argc|

|__p\_\__argv|

|__p\_\__initenv|

|[__p\_\__mb_cur_max](../c-runtime-library/mb-cur-max-func-mb-cur-max-l-func-p-mb-cur-max-mb-cur-max.md)|

|__p\_\__wargv|

|__p\_\__winitenv|