/U, /u (Undefine Symbols)
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/U, /u (Undefine Symbols)

Undefine previously defined symbols. /U undefines the specified symbol. /u undefines all previously defined symbols.

/U[ ]symbol


The symbol you want undefined.

Neither option can undefine symbols created with the #define directive.

Both options undefine the following Microsoft-specific macros.

Symbol Function


Default char type is unsigned. Defined when /J is specified.


Defined for code compiled with the /GR (Enable Run-Time Type Information) option.


Defined for code compiled with the /EHsc (Enable Exception Handling) option.


Defined when /MD is specified.


Defined to 600, by default, for x86 targets.


For more information, see Predefined Macros.


Defined for applications for WIN32. Always defined.


Defined when /MD or /MT 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

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