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-U
Removes any initial definition of the specified macro.
Syntax
-Uname
Where:
nameis the name of the macro to be undefined.
The macro name
A predefined macro.
A macro specified using the
-Doption.
Note
Not all compiler predefined macros can be undefined.Usage
Specifying -U has the same effect as placing the
text name#undef at the head of each source file.name
Restrictions
The compiler defines and undefines macros in the following order:
Compiler predefined macros.
Macros defined explicitly, using
-D.nameMacros explicitly undefined, using
-U.name