How to: Use the #undef Directive

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Applies To: Microsoft Dynamics AX 2012 R3, Microsoft Dynamics AX 2012 R2, Microsoft Dynamics AX 2012 Feature Pack, Microsoft Dynamics AX 2012

You can use the #undef directive to remove a macro definition that exists from a previous #define. After a macro name has been created by #define and then removed by #undef, the macro can be created again by another #define.

#undef has no effect on macros that are created by the #localmacro directive.

Prerequisites

For this topic, you must understand the information in How to: Use #define and #if to Test a Macro.

Using #undef

In the following code sample, the macro MyMacro is undefined by using the #undef directive. The #undef occurs between the two #if tests for its existence. The output shows only the first #if test was true.

    static void UndefMacroJob(Args _args)
    {
        ;
        #define.MyMacro
    
        #if.MyMacro
            info("Macro is defined (1)");
        #endif
    
        #undef.MyMacro // Removes the macro.
    
        #if.MyMacro
            info("Macro is defined (2)");
        #endif
    
    /************* Actual output
    Message (10:19:15 am)
    Macro is defined (1)
    *************/
    }

See also

Macros in X++

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