Chapter 3.

Command Line Options

This chapter describes command line options available in all versions of the gnu assembler; Chapter

9 Machine Dependent Features, for options specific to particular machine architectures.

If you are invoking

as

via the gnu C compiler, you can use the

 Wa

option to pass arguments through to

the assembler. The assembler arguments must be separated from each other (and the

 Wa

) by commas.

For example:

gcc  c  g  O  Wa, alh, L file.c

This passes two options to the assembler:

 alh

(emit a listing to standard output with high level and

assembly source) and

 L

(retain local symbols in the symbol table).

Usually you do not need to use this

 Wa

mechanism, since many compiler command line options are

automatically passed to the assembler by the compiler. (You can call the gnu compiler driver with the

 v

option to see precisely what options it passes to each compilation pass, including the assembler.)

3.1. Enable Listings:

 a[cdhlns]

These options enable listing output from the assembler. By itself,

 a

requests high level, assembly,

and symbols listing. You can use other letters to select specific options for the list:

 ah

requests a high 

level language listing,

 al

requests an output program assembly listing, and

 as

requests a symbol

table listing. High level listings require that a compiler debugging option like

 g

be used, and that

assembly listings (

 al

) be requested also.

Use the

 ac

option to omit false conditionals from a listing. Any lines which are not assembled

because of a false

.if

(or

.ifdef

, or any other conditional), or a true

.if

followed by an

.else

,

will be omitted from the listing.

Use the

 ad

option to omit debugging directives from the listing.

Once you have specified one of these options, you can further control listing output and its appearance

using the directives

.list

,

.nolist

,

.psize

,

.eject

,

.title

, and

.sbttl

. The

 an

option turns

off all forms processing. If you do not request listing output with one of the

 a

options, the listing 

control directives have no effect.

The letters after

 a

may be combined into one option, e.g.,

 aln

.

Note if the assembler source is coming from the standard input (eg because it is being created by

gcc

and the

 pipe

command line switch is being used) then the listing will not contain any comments

or preprocessor directives. This is because the listing code buffers input source lines from stdin only

after they have been preprocessed by the assembler. This reduces memory usage and makes the code

more efficient.

3.2.

 alternate

Begin in alternate macro mode, see Section 8.61

.altmacro

.