III.11.6 Premature End of a Macro Expansion

Sometimes it is useful, if a macro expansion can be terminated, before the end of the macro body is reached. This can be forced with the EXITM (exit macro) instruction. However, this makes sense in conjunction with conditional assembly only.

Example:

        FLEXIBLE MACRO QUANTITY
        DB 'Text'
        IF QUANTITY LE 255
        EXITM
        ENDIF
        DW QUANTITY
        ENDM

The macro FLEXIBLE always has to insert the string 'Text' into the CODE space. After that, it should insert a 16-bit constant only, if the numerical value of the parameter QUANTITY is greater than 255.
Otherwise the macro expansion should be terminated with EXITM before. If the macro is called as follows,

        FLEXIBLE 42

it will be expanded to

        DB 'Text'

in list mode $GENONLY/$CONDONLY.
However, if it is called like this,

        FLEXIBLE 4711

it will be expanded to:

        DB 'Text'
        DW 4711

When a macro expansion is terminated with EXITM, all IFxx constructions that have been opened within the macro body so far, are closed.
Of course macro bodies may also contain control statements. If an include file is inserted into a macro body with a $INCLUDE control, and this include file, or a nested include file, contains an EXITM instruction, all include file levels up to the next macro level are closed at this point, and the expansion of that macro is terminated immediately.