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Chapter 8. Assembler Directives

Expression results as strings

You can write

%expr

to evaluate the expression

expr

and use the result as a string.

8.62.

.noaltmacro

Disable alternate macro mode. Section 8.61

.altmacro

8.63.

.nolist

Control (in conjunction with the

.list

directive) whether or not assembly listings are generated.

These two directives maintain an internal counter (which is zero initially).

.list

increments the

counter, and

.nolist

decrements it. Assembly listings are generated whenever the counter is greater

than zero.

8.64.

.octa bignums

This directive expects zero or more bignums, separated by commas. For each bignum, it emits a 16 

byte integer.

The term "octa" comes from contexts in which a "word" is two bytes; hence octa word for 16 bytes.

8.65.

.org new lc, fill

Advance the location counter of the current section to

new lc

.

new lc

is either an absolute expres 

sion or an expression with the same section as the current subsection. That is, you can't use

.org

to

cross sections: if

new lc

has the wrong section, the

.org

directive is ignored. To be compatible with

former assemblers, if the section of

new lc

is absolute,

as

issues a warning, then pretends the section

of

new lc

is the same as the current subsection.

.org

may only increase the location counter, or leave it unchanged; you cannot use

.org

to move the

location counter backwards.

Because

as

tries to assemble programs in one pass,

new lc

may not be undefined. If you really detest

this restriction we eagerly await a chance to share your improved assembler.

Beware that the origin is relative to the start of the section, not to the start of the subsection. This is

compatible with other people's assemblers.

When the location counter (of the current subsection) is advanced, the intervening bytes are filled with

fill

which should be an absolute expression. If the comma and

fill

are omitted,

fill

defaults to

zero.

8.66.

.p2align[wl] abs expr, abs expr, abs expr

Pad the location counter (in the current subsection) to a particular storage boundary. The first expres 

sion (which must be absolute) is the number of low order zero bits the location counter must have

after advancement. For example

.p2align 3

advances the location counter until it a multiple of 8.

If the location counter is already a multiple of 8, no change is needed.

The second expression (also absolute) gives the fill value to be stored in the padding bytes. It (and

the comma) may be omitted. If it is omitted, the padding bytes are normally zero. However, on some

systems, if the section is marked as containing code and the fill value is omitted, the space is filled

with no op instructions.