/experimental:preprocessor (Enable preprocessor conformance mode)
This option enables an experimental, token-based preprocessor that more closely conforms to C++11 standards, including C99 preprocessor features. For more information, see MSVC experimental preprocessor overview.
Use the /experimental:preprocessor compiler option to enable the experimental conforming preprocessor. You can use /experimental:preprocessor- option to explicitly specify the traditional preprocessor.
The /experimental:preprocessor option is available starting in Visual Studio 2017 version 15.8.
To set this compiler option in the Visual Studio development environment
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.
Modify the Additional Options property to include /experimental:preprocessor and then choose OK.