source: trunk/src/binutils/gas/doc/as.info-3@ 1109

This is as.info, produced by makeinfo version 4.3 from as.texinfo.

START-INFO-DIR-ENTRY
* As: (as).                     The GNU assembler.
* Gas: (as).                    The GNU assembler.
END-INFO-DIR-ENTRY

   This file documents the GNU Assembler "as".

   Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002
Free Software Foundation, Inc.

   Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts.  A copy of the license is included in the section entitled "GNU
Free Documentation License".


File: as.info,  Node: Balign,  Next: Byte,  Prev: Asciz,  Up: Pseudo Ops

`.balign[wl] ABS-EXPR, ABS-EXPR, ABS-EXPR'
==========================================

   Pad the location counter (in the current subsection) to a particular
storage boundary.  The first expression (which must be absolute) is the
alignment request in bytes.  For example `.balign 8' advances the
location counter until it is 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.

   The third expression is also absolute, and is also optional.  If it
is present, it is the maximum number of bytes that should be skipped by
this alignment directive.  If doing the alignment would require
skipping more bytes than the specified maximum, then the alignment is
not done at all.  You can omit the fill value (the second argument)
entirely by simply using two commas after the required alignment; this
can be useful if you want the alignment to be filled with no-op
instructions when appropriate.

   The `.balignw' and `.balignl' directives are variants of the
`.balign' directive.  The `.balignw' directive treats the fill pattern
as a two byte word value.  The `.balignl' directives treats the fill
pattern as a four byte longword value.  For example, `.balignw
4,0x368d' will align to a multiple of 4.  If it skips two bytes, they
will be filled in with the value 0x368d (the exact placement of the
bytes depends upon the endianness of the processor).  If it skips 1 or
3 bytes, the fill value is undefined.


File: as.info,  Node: Byte,  Next: Comm,  Prev: Balign,  Up: Pseudo Ops

`.byte EXPRESSIONS'
===================

   `.byte' expects zero or more expressions, separated by commas.  Each
expression is assembled into the next byte.


File: as.info,  Node: Comm,  Next: Data,  Prev: Byte,  Up: Pseudo Ops

`.comm SYMBOL , LENGTH '
========================

   `.comm' declares a common symbol named SYMBOL.  When linking, a
common symbol in one object file may be merged with a defined or common
symbol of the same name in another object file.  If `ld' does not see a
definition for the symbol-just one or more common symbols-then it will
allocate LENGTH bytes of uninitialized memory.  LENGTH must be an
absolute expression.  If `ld' sees multiple common symbols with the
same name, and they do not all have the same size, it will allocate
space using the largest size.

   When using ELF, the `.comm' directive takes an optional third
argument.  This is the desired alignment of the symbol, specified as a
byte boundary (for example, an alignment of 16 means that the least
significant 4 bits of the address should be zero).  The alignment must
be an absolute expression, and it must be a power of two.  If `ld'
allocates uninitialized memory for the common symbol, it will use the
alignment when placing the symbol.  If no alignment is specified, `as'
will set the alignment to the largest power of two less than or equal
to the size of the symbol, up to a maximum of 16.

   The syntax for `.comm' differs slightly on the HPPA.  The syntax is
`SYMBOL .comm, LENGTH'; SYMBOL is optional.


File: as.info,  Node: Data,  Next: Def,  Prev: Comm,  Up: Pseudo Ops

`.data SUBSECTION'
==================

   `.data' tells `as' to assemble the following statements onto the end
of the data subsection numbered SUBSECTION (which is an absolute
expression).  If SUBSECTION is omitted, it defaults to zero.


File: as.info,  Node: Def,  Next: Desc,  Prev: Data,  Up: Pseudo Ops

`.def NAME'
===========

   Begin defining debugging information for a symbol NAME; the
definition extends until the `.endef' directive is encountered.

   This directive is only observed when `as' is configured for COFF
format output; when producing `b.out', `.def' is recognized, but
ignored.


File: as.info,  Node: Desc,  Next: Dim,  Prev: Def,  Up: Pseudo Ops

`.desc SYMBOL, ABS-EXPRESSION'
==============================

   This directive sets the descriptor of the symbol (*note Symbol
Attributes::) to the low 16 bits of an absolute expression.

   The `.desc' directive is not available when `as' is configured for
COFF output; it is only for `a.out' or `b.out' object format.  For the
sake of compatibility, `as' accepts it, but produces no output, when
configured for COFF.


File: as.info,  Node: Dim,  Next: Double,  Prev: Desc,  Up: Pseudo Ops

`.dim'
======

   This directive is generated by compilers to include auxiliary
debugging information in the symbol table.  It is only permitted inside
`.def'/`.endef' pairs.

   `.dim' is only meaningful when generating COFF format output; when
`as' is generating `b.out', it accepts this directive but ignores it.


File: as.info,  Node: Double,  Next: Eject,  Prev: Dim,  Up: Pseudo Ops