/U, /u (Undefine Symbols)

The /U compiler option undefines the specified preprocessor symbol. The /u compiler option undefines the Microsoft-specific symbols that the compiler defines.

Syntax

/U[ ]symbol
/u

Arguments

symbol
The preprocessor symbol to undefine.

Remarks

Neither the /U or /u option can undefine a symbol created by using the #define directive.

The /U option can undefine a symbol that was previously defined by using the /D option.

By default, the compiler defines the following Microsoft-specific symbols.

Symbol Function
_CHAR_UNSIGNED Default char type is unsigned. Defined when the /J option is specified.
_CPPRTTI Defined for code compiled with the /GR option.
_CPPUNWIND Defined for code compiled with the /EHsc option.
_DLL Defined when the /MD option is specified.
_M_IX86 By default, defined to 600 for x86 targets.
_MSC_VER For more information, see Predefined Macros.
_WIN32 Defined for WIN32 applications. Always defined.
_MT Defined when the /MD or /MT option is specified.

To set this compiler option in the Visual Studio development environment

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

  2. Click the C/C++ folder.

  3. Click the Advanced property page.

  4. Modify the Undefine Preprocessor Definitions or Undefine All Preprocessor Definitions properties.

To set this compiler option programmatically

See also

MSVC Compiler Options
MSVC Compiler Command-Line Syntax
/J (Default char Type Is unsigned)
/GR (Enable Run-Time Type Information)
/EH (Exception Handling Model)
/MD, /MT, /LD (Use Run-Time Library)