### /U Compiler Option

Syntax: | Default:
/U[name|*] | Retain macros.

Use /U to undefine macros.

Specify /Uname to undefine macro name.

Specify /U* to undefine all macros.

Note: /U does not affect some macros, such as __DATE__, __TIME__, __TIMESTAMP__, __FILE__, and __FUNCTION__, nor does it undefine macros defined in source code.

Use the /D compiler option to define or redefine macros on the command line. Macros defined on the command line override macros defined in the source code.

By default, the preprocessor retains all macros.

Summary of Compiler Options