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/U, /u (Undefine Symbols)

Updated: March 2009

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

/U[ ]symbol
/u

symbol

The preprocessor symbol to undefine.

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 How to: Open Project Property Pages.

  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

Date

History

Reason

March 2009

Improved the description of the compiler options.

Information enhancement.

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