48

Chapter 8. Assembler Directives

.equ SYM,VAL

8.33.

.err

If

as

assembles a

.err

directive, it will print an error message and, unless the

 Z

option was used, it

will not generate an object file. This can be used to signal error an conditionally compiled code.

8.34.

.exitm

Exit early from the current macro definition. Section 8.60

.macro

.

8.35.

.extern

.extern

is accepted in the source program  for compatibility with other assemblers  but it is ignored.

as

treats all undefined symbols as external.

8.36.

.fail expression

Generates an error or a warning. If the value of the

expression

is 500 or more,

as

will print a

warning message. If the value is less than 500,

as

will print an error message. The message will

include the value of

expression

. This can occasionally be useful inside complex nested macros or

conditional assembly.

8.37.

.file string

.file

tells

as

that we are about to start a new logical file.

string

is the new file name. In general,

the filename is recognized whether or not it is surrounded by quotes

"

; but if you wish to specify

an empty file name, you must give the quotes 

""

. This statement may go away in future: it is only

recognized to be compatible with old

as

programs. In some configurations of

as

,

.file

has already

been removed to avoid conflicts with other assemblers. Chapter 9 Machine Dependent Features.

8.38.

.fill repeat, size, value

repeat

,

size

and

value

are absolute expressions. This emits

repeat

copies of

size

bytes.

Repeat

may be zero or more.

Size

may be zero or more, but if it is more than 8, then it is deemed to have the

value 8, compatible with other people's assemblers. The contents of each

repeat

bytes is taken from

an 8 byte number. The highest order 4 bytes are zero. The lowest order 4 bytes are

value

rendered

in the byte order of an integer on the computer

as

is assembling for. Each

size

bytes in a repetition

is taken from the lowest order

size

bytes of this number. Again, this bizarre behavior is compatible

with other people's assemblers.

size

and

value

are optional. If the second comma and

value

are absent,

value

is assumed zero. If

the first comma and following tokens are absent,

size

is assumed to be 1.