/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 of the /U and /u options 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 may define a large number of Microsoft-specific symbols. Here are a few common ones:
| 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 |
Defined as a unique integer value for each compiler version. For more information, see Predefined macros. |
_WIN32 |
Defined for WIN32 applications. Always defined. |
_MT |
Defined when the /MD or /MT option is specified. |
For a complete list of Microsoft-specific predefined macros, see Predefined macros.
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++ > Advanced property page.
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)