# 8.58. .macro

The commands .macro and .endm allow you to define macros that generate assembly output. For example, this definition specifies a macro sum that puts a sequence of numbers into memory:

  .macro sum from=0, to=5 .long \from .if \to-\from sum "(\from+1)",\to .endif .endm

With that definition, SUM 0,5 is equivalent to this assembly input:

  .long 0 .long 1 .long 2 .long 3 .long 4 .long 5

.macro macname, .macro macname macargs

Begin the definition of a macro called macname. If your macro definition requires arguments, specify their names after the macro name, separated by commas or spaces. You can supply a default value for any macro argument by following the name with =deflt. For example, these are all valid .macro statements:

.macro comm

Begin the definition of a macro called comm, which takes no arguments.

.macro plus1 p, p1, .macro plus1 p p1

Either statement begins the definition of a macro called plus1, which takes two arguments; within the macro definition, write \p or \p1 to evaluate the arguments.

.macro reserve_str p1=0 p2

Begin the definition of a macro called reserve_str, with two arguments. The first argument has a default value, but not the second. After the definition is complete, you can call the macro either as reserve_str a,b (with \p1 evaluating to a and \p2 evaluating to b), or as reserve_str ,b (with \p1 evaluating as the default, in this case 0, and \p2 evaluating to b).

When you call a macro, you can specify the argument values either by position, or by keyword. For example, sum 9,17 is equivalent to sum to=17, from=9.

.endm

Mark the end of a macro definition.

.exitm

Exit early from the current macro definition.

\@

as maintains a counter of how many macros it has executed in this pseudo-variable; you can copy that number to your output with \@, but only within a macro definition.