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#CONTENT

#TOP

#macros

See https://nasm.us/doc/nasmdoc4.html for the chapter on NASM preprocessor.

#singleline macros

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%define calc(a,b) a+b

#multiline macros

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%macro [name] [number of arguments]
    ; %0 is the number of arguments passed
    ; %1 is first argument
    ; %2 is second argument
    ; ... etc
%endmacro

#custom bytecode

NASM supports overriding existing instructions with macros.

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%macro mov 0
    db 0xee, 0xcc
%endmacro

The mov instruction will now emit 0xee 0xcc instead of the normal instruction bytes.