/Zc:wchar_t (wchar_t Is Native Type)
Parse wchar_t as a built-in type according to the C++ standard. By default, /Zc:wchar_t is on.
If /Zc:wchar_t is on, wchar_t maps to the Microsoft-specific native type __wchar_t. If /Zc:wchar_t- (with a minus sign) is specified, wchar_t maps to a typedef for unsigned short. (In Visual C++ 6.0 and earlier, wchar_t was not implemented as a built-in type, but was declared in wchar.h as a typedef for unsigned short.) We do not recommend /Zc:wchar_t- because the C++ standard requires that wchar_t be a built-in type. Using the typedef version can cause portability problems. If you upgrade from earlier versions of Visual C++ and encounter compiler error C2664 because the code is trying to implicitly convert a wchar_t to unsigned short, we recommend that you change the code to fix the error, instead of setting /Zc:wchar_t-.
If you write new code that has to interoperate with older code that still uses the typedef version of wchar_t, you can provide overloads for both the unsigned short and __wchar_t variations of wchar_t, so that your code can be linked with code compiled with /Zc:wchar_t or code compiled without it. Otherwise, you would have to provide two different builds of the library—one with and one without /Zc:wchar_t enabled. Even in this case, we recommend that you build the older code by using the same compiler that you use to compile the new code. Never mix binaries compiled with different compilers.
When /Zc:wchar_t is specified, _WCHAR_T_DEFINED and _NATIVE_WCHAR_T_DEFINED symbols are defined. For more information, see Predefined Macros.
If your code uses the compiler COM global functions, because /Zc:wchar_t is now on by default, we recommend that you change explicit references to comsupp.lib—from the comment pragma or on the command line—to either comsuppw.lib or comsuppwd.lib. (If you must compile with /Zc:wchar_t-, use comsupp.lib.) If you include the comdef.h header file, the correct library is specified for you. For information about compiler COM support, see Compiler COM Support.
The wchar_t type is not supported when you compile C code. For more information about conformance issues with Visual C++, see Compatibility and Compliance Issues in Visual C++.
To set this compiler option in the Visual Studio development environment
Open the project's Property Pages dialog box. For details, see Working with Project Properties.
In the left pane, expand Configuration Properties, C/C++, and then select Language.
Modify the Treat wchar_t as Built-in Type property.