The Free Software Foundation Inc. thanks The Nice Computer
Company of Australia for loaning Dean Elsner to write the
first (Vax) version of as
for Project GNU.
The proprietors, management and staff of TNCCA thank FSF for
distracting the boss while they got some work
done.
Copyright (C) 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.
Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.
Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions.
This manual is a user guide to the GNU assembler ppcas
.
This version of the manual describes ppcas
configured to generate
code for Power PC architectures.
Here is a brief summary of how to invoke ppcas
. For details,
see section Command-Line Options.
ppcas [ -a[dhlns][=file] ] [ -D ] [ --defsym sym=val ] [ -f ] [ --help ] [ -I dir ] [ -J ] [ -K ] [ -L ] [ -o objfile ] [ -R ] [ --statistics ] [ -v ] [ -version ] [ --version ] [ -W ] [ -w ] [ -x ] [ -Z ] [ -- | files ... ]
-a[dhlns]
-ad
-ah
-al
-an
-as
=file
-D
--defsym sym=value
-f
--help
-I dir
.include
directives.
-J
-K
-L
-o objfile
ppcas
objfile.
-R
--statistics
-v
-version
as
version.
--version
as
version and exit.
-W
-w
-x
-Z
-- | files ...
This manual is intended to describe what you need to know to use
GNU ppcas
. We cover the syntax expected in source files, including
notation for symbols, constants, and expressions; the directives that
ppcas
understands; and of course how to invoke ppcas
.
We also cover special features in the Power PC
configuration of ppcas
, including assembler directives.
On the other hand, this manual is not intended as an introduction to programming in assembly language--let alone programming in general! In a similar vein, we make no attempt to introduce the machine architecture; we do not describe the instruction set, standard mnemonics, registers or addressing modes that are standard to a particular architecture.
GNU as
is really a family of assemblers.
This manual describes ppcas
, a member of that family which is
configured for the Power PC architectures.
If you use (or have used) the GNU assembler on one architecture, you
should find a fairly similar environment when you use it on another
architecture. Each version has much in common with the others,
including object file formats, most assembler directives (often called
pseudo-ops) and assembler syntax.
ppcas
is primarily intended to assemble the output of the
GNU C compiler gcc
for use by the linker
link3do
. Nevertheless, we've tried to make ppcas
assemble correctly everything that other assemblers for the same
machine would assemble.
Unlike older assemblers, ppcas
is designed to assemble a source
program in one pass of the source file. This has a subtle impact on the
.org directive (see section .org new-lc
, fill).
The GNU assembler can be configured to produce several alternative
object file formats. For the most part, this does not affect how you
write assembly language programs; but directives for debugging symbols
are typically different in different file formats. See section Symbol Attributes.
On the Power PC, ppcas
is configured to produce
ELF format object files.
After the program name ppcas
, the command line may contain
options and file names. Options may appear in any order, and may be
before, after, or between file names. The order of file names is
significant.
`--' (two hyphens) by itself names the standard input file
explicitly, as one of the files for ppcas
to assemble.
Except for `--' any command line argument that begins with a
hyphen (`-') is an option. Each option changes the behavior of
ppcas
. No option changes the way another option works. An
option is a `-' followed by one or more letters; the case of
the letter is important. All options are optional.
Some options expect exactly one file name to follow them. The file name may either immediately follow the option's letter (compatible with older assemblers) or it may be the next command argument (GNU standard). These two command lines are equivalent:
ppcas -o my-object-file.o mumble.s ppcas -omy-object-file.o mumble.s
We use the phrase source program, abbreviated source, to
describe the program input to one run of ppcas
. The program may
be in one or more files; how the source is partitioned into files
doesn't change the meaning of the source.
The source program is a concatenation of the text in all the files, in the order specified.
Each time you run ppcas
it assembles exactly one source
program. The source program is made up of one or more files.
(The standard input is also a file.)
You give ppcas
a command line that has zero or more input file
names. The input files are read (from left file name to right). A
command line argument (in any position) that has no special meaning
is taken to be an input file name.
If you give ppcas
no file names it attempts to read one input file
from the ppcas
standard input, which is normally your terminal. You
may have to type ctl-D to tell ppcas
there is no more program
to assemble.
Use `--' if you need to explicitly name the standard input file in your command line.
If the source is empty, ppcas
produces a small, empty object
file.
There are two ways of locating a line in the input file (or files) and either may be used in reporting error messages. One way refers to a line number in a physical file; the other refers to a line number in a "logical" file. See section Error and Warning Messages.
Physical files are those files named in the command line given
to ppcas
.
Logical files are simply names declared explicitly by assembler
directives; they bear no relation to physical files. Logical file names
help error messages reflect the original source file, when ppcas
source is itself synthesized from other files.
See section .app-file string
.
Every time you run ppcas
it produces an output file, which is
your assembly language program translated into numbers. This file
is the object file. Its default name is
a.out
.
b.out
when ppcas
is configured for the Intel 80960.
You can give it another name by using the -o
option. Conventionally,
object file names end with `.o'. The default name is used for historical
reasons: older assemblers were capable of assembling self-contained programs
directly into a runnable program. (For some formats, this isn't currently
possible, but it can be done for the a.out
format.)
The object file is meant for input to the linker link3do
. It contains
assembled program code, information to help link3do
integrate
the assembled program into a runnable file, and (optionally) symbolic
information for the debugger.
ppcas
may write warnings and error messages to the standard error
file (usually your terminal). This should not happen when a compiler
runs ppcas
automatically. Warnings report an assumption made so
that ppcas
could keep assembling a flawed program; errors report a
grave problem that stops the assembly.
Warning messages have the format
file_name:NNN:Warning Message Text
(where NNN is a line number). If a logical file name has been given
(see section .app-file string
) it is used for the filename,
otherwise the name of the current input file is used. If a logical line
number was given
(see section .line line-number
)
then it is used to calculate the number printed,
otherwise the actual line in the current source file is printed. The
message text is intended to be self explanatory (in the grand Unix
tradition).
Error messages have the format
file_name:NNN:FATAL:Error Message Text
The file name and line number are derived as for warning messages. The actual message text may be rather less explanatory because many of them aren't supposed to happen.
This chapter describes command-line options available in all versions of the GNU assembler; see section PowerPC Dependent Features, for options specific to the Power PC.
If you are invoking ppcas
via the GNU C compiler (version 2), 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
emits a listing to standard output with high-level and assembly source.
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.)
-a[dhlns]
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 `-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'.
-D
This option has no effect whatsoever, but it is accepted to make it more
likely that scripts written for other assemblers also work with
ppcas
.
-f
`-f' should only be used when assembling programs written by a (trusted) compiler. `-f' stops the assembler from doing whitespace and comment preprocessing on the input file(s) before assembling them. See section Preprocessing.
Warning: if you use `-f' when the files actually need to be preprocessed (if they contain comments, for example),
ppcas
does not work correctly.
.include
search path: -I
path
Use this option to add a path to the list of directories
ppcas
searches for files specified in .include
directives (see section .include "file
"). You may use -I
as
many times as necessary to include a variety of paths. The current
working directory is always searched first; after that, ppcas
searches any `-I' directories in the same order as they were
specified (left to right) on the command line.
-K
On the Power PC family, this option is allowed, but has no effect. It is permitted for compatibility with the GNU assembler on other platforms, where it can be used to warn when the assembler alters the machine code generated for `.word' directives in difference tables. The Power PC family does not have the addressing limitations that sometimes lead to this alteration on other platforms.
-L
Labels beginning with `L' (upper case only) are called local
labels. See section Symbol Names. Normally you do not see such labels when
debugging, because they are intended for the use of programs (like
compilers) that compose assembler programs, not for your notice.
Normally both ppcas
and link3do
discard such labels, so you do not
normally debug with them.
This option tells ppcas
to retain those `L...' symbols
in the object file. Usually if you do this you also tell the linker
link3do
to preserve symbols whose names begin with `L'.
By default, a local label is any label beginning with `L', but each target is allowed to redefine the local label prefix.
-o
There is always one object file output when you run ppcas
. By
default it has the name
`a.out'.
`a.out'.
You use this option (which takes exactly one filename) to give the
object file a different name.
Whatever the object file is called, ppcas
overwrites any
existing file of the same name.
-R
-R
tells ppcas
to write the object file as if all
data-section data lives in the text section. This is only done at
the very last moment: your binary data are the same, but data
section parts are relocated differently. The data section part of
your object file is zero bytes long because all its bytes are
appended to the text section. (See section Sections and Relocation.)
When you specify -R
it would be possible to generate shorter
address displacements (because we do not have to cross between text and
data section). We refrain from doing this simply for compatibility with
older versions of ppcas
. In future, -R
may work this way.
--statistics
Use `--statistics' to display two statistics about the resources used by
ppcas
: the maximum amount of space allocated during the assembly
(in bytes), and the total execution time taken for the assembly (in CPU
seconds).
-v
You can find out what version of as is running by including the option `-v' (which you can also spell as `-version') on the command line.
-W
ppcas
should never give a warning or error message when
assembling compiler output. But programs written by people often
cause ppcas
to give a warning that a particular assumption was
made. All such warnings are directed to the standard error file.
If you use this option, no warnings are issued. This option only
affects the warning messages: it does not change any particular of how
ppcas
assembles your file. Errors, which stop the assembly, are
still reported.
-Z
After an error message, ppcas
normally produces no output. If for
some reason you are interested in object file output even after
ppcas
gives an error message on your program, use the `-Z'
option. If there are any errors, ppcas
continues anyways, and
writes an object file after a final warning message of the form `n
errors, m warnings, generating bad object file.'
This chapter describes the machine-independent syntax allowed in a
source file. ppcas
syntax is similar to what many other
assemblers use; it is inspired by the BSD 4.2
assembler.
The ppcas
internal preprocessor:
It does not do macro processing, include file handling, or
anything else you may get from your C compiler's preprocessor. You can
do include file processing with the .include
directive
(see section .include "file
"). You can use the GNU C compiler driver
to get other "CPP" style preprocessing, by giving the input file a
`.S' suffix. See section `Options Controlling the Kind of Output' in Using GNU CC.
Excess whitespace, comments, and character constants cannot be used in the portions of the input text that are not preprocessed.
If the first line of an input file is #NO_APP
or if you use the
`-f' option, whitespace and comments are not removed from the input file.
Within an input file, you can ask for whitespace and comment removal in
specific portions of the by putting a line that says #APP
before the
text that may contain whitespace or comments, and putting a line that says
#NO_APP
after this text. This feature is mainly intend to support
asm
statements in compilers whose output is otherwise free of comments
and whitespace.
Whitespace is one or more blanks or tabs, in any order. Whitespace is used to separate symbols, and to make programs neater for people to read. Unless within character constants (see section Character Constants), any whitespace means the same as exactly one space.
There are two ways of rendering comments to ppcas
. In both
cases the comment is equivalent to one space.
Anything from `/*' through the next `*/' is a comment. This means you may not nest these comments.
/* The only way to include a newline ('\n') in a comment is to use this sort of comment. */ /* This sort of comment does not nest. */
Anything from the line comment character to the next newline is considered a comment and is ignored. The line comment character is `#' on the PowerPC; see section PowerPC Dependent Features.
To be compatible with past assemblers, lines that begin with `#' have a special interpretation. Following the `#' should be an absolute expression (see section Expressions): the logical line number of the next line. Then a string (see section Strings) is allowed: if present it is a new logical file name. The rest of the line, if any, should be whitespace.
If the first non-whitespace characters on the line are not numeric, the line is ignored. (Just like a comment.)
# This is an ordinary comment. # 42-6 "new_file_name" # New logical file name # This is logical line # 36.
This feature is deprecated, and may disappear from future versions
of ppcas
.
No symbol may begin with a digit. Case is significant. There is no length limit: all characters are significant. Symbols are delimited by characters not in that set, or by the beginning of a file (since the source program must end with a newline, the end of a file is not a possible symbol delimiter). See section Symbols.
A statement ends at a newline character (`\n') or at a semicolon (`;'). The newline or semicolon is considered part of the preceding statement. Newlines and semicolons within character constants are an exception: they do not end statements.
It is an error to end any statement with end-of-file: the last character of any input file should be a newline.
You may write a statement on more than one line if you put a
backslash (\) immediately in front of any newlines within the
statement. When ppcas
reads a backslashed newline both
characters are ignored. You can even put backslashed newlines in
the middle of symbol names without changing the meaning of your
source program.
An empty statement is allowed, and may include whitespace. It is ignored.
A statement begins with zero or more labels, optionally followed by a key symbol which determines what kind of statement it is. The key symbol determines the syntax of the rest of the statement. If the symbol begins with a dot `.' then the statement is an assembler directive: typically valid for any computer. If the symbol begins with a letter the statement is an assembly language instruction: it assembles into a machine language instruction.
A label is a symbol immediately followed by a colon (:
).
Whitespace before a label or after a colon is permitted, but you may not
have whitespace between a label's symbol and its colon. See section Labels.
label: .directive followed by something another_label: # This is an empty statement. instruction operand_1, operand_2, ...
A constant is a number, written so that its value is known by inspection, without knowing any context. Like this:
.byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value. .ascii "Ring the bell\7" # A string constant. .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum. .float 0f-314159265358979323846264338327\ 95028841971.693993751E-40 # - pi, a flonum.
There are two kinds of character constants. A character stands for one character in one byte and its value may be used in numeric expressions. String constants (properly called string literals) are potentially many bytes and their values may not be used in arithmetic expressions.
A string is written between double-quotes. It may contain
double-quotes or null characters. The way to get special characters
into a string is to escape these characters: precede them with
a backslash `\' character. For example `\\' represents
one backslash: the first \
is an escape which tells
ppcas
to interpret the second character literally as a backslash
(which prevents ppcas
from recognizing the second \
as an
escape character). The complete list of escapes follows.
\008
has the value 010, and \009
the value 011.
ppcas
has no
other interpretation, so ppcas
knows it is giving you the wrong
code and warns you of the fact.
Which characters are escapable, and what those escapes represent, varies widely among assemblers. The current set is what we think the BSD 4.2 assembler recognizes, and is a subset of what most C compilers recognize. If you are in doubt, do not use an escape sequence.
A single character may be written as a single quote immediately
followed by that character. The same escapes apply to characters as
to strings. So if you want to write the character backslash, you
must write '\\ where the first \
escapes the second
\
. As you can see, the quote is an acute accent, not a
grave accent. A newline
(or semicolon `;')
immediately following an acute accent is taken as a literal character
and does not count as the end of a statement. The value of a character
constant in a numeric expression is the machine's byte-wide code for
that character. ppcas
assumes your character code is ASCII:
'A means 65, 'B means 66, and so on.
ppcas
distinguishes three kinds of numbers according to how they
are stored in the target machine. Integers are numbers that
would fit into an int
in the C language. Bignums are
integers, but they are stored in more than 32 bits. Flonums
are floating point numbers, described below.
A binary integer is `0b' or `0B' followed by zero or more of the binary digits `01'.
An octal integer is `0' followed by zero or more of the octal digits (`01234567').
A decimal integer starts with a non-zero digit followed by zero or more digits (`0123456789').
A hexadecimal integer is `0x' or `0X' followed by one or more hexadecimal digits chosen from `0123456789abcdefABCDEF'.
Integers have the usual values. To denote a negative integer, use the prefix operator `-' discussed under expressions (see section Prefix Operator).
A bignum has the same syntax and semantics as an integer except that the number (or its negative) takes more than 32 bits to represent in binary. The distinction is made because in some places integers are permitted while bignums are not.
A flonum represents a floating point number. The translation is
indirect: a decimal floating point number from the text is converted by
ppcas
to a generic binary floating point number of more than
sufficient precision. This generic floating point number is converted
to a particular computer's floating point format (or formats) by a
portion of ppcas
specialized to that computer.
A flonum is written by writing (in order)
ppcas
the rest of the number is a flonum.
At least one of the integer part or the fractional part must be present. The floating point number has the usual base-10 value.
ppcas
does all processing using integers. Flonums are computed
independently of any floating point hardware in the computer running
ppcas
.
into a field whose width depends on which assembler directive has the bit-field as its argument. Overflow (a result from the bitwise and requiring more binary digits to represent) is not an error; instead, more constants are generated, of the specified width, beginning with the least significant digits.
The directives .byte
, .hword
, .int
, .long
,
.short
, and .word
accept bit-field arguments.
Roughly, a section is a range of addresses, with no gaps; all data "in" those addresses is treated the same for some particular purpose. For example there may be a "read only" section.
The linker link3do
reads many object files (partial programs) and
combines their contents to form a runnable program. When ppcas
emits an object file, the partial program is assumed to start at address 0.
link3do
assigns the final addresses for the partial program, so that
different partial programs do not overlap. This is actually an
oversimplification, but it suffices to explain how ppcas
uses
sections.
link3do
moves blocks of bytes of your program to their run-time
addresses. These blocks slide to their run-time addresses as rigid
units; their length does not change and neither does the order of bytes
within them. Such a rigid unit is called a section. Assigning
run-time addresses to sections is called relocation. It includes
the task of adjusting mentions of object-file addresses so they refer to
the proper run-time addresses.
An object file written by ppcas
has at least three sections, any
of which may be empty. These are named text, data and
bss sections.
ppcas
can also generate whatever other named sections you specify
using the `.section' directive (@xref{Section,,.section
}).
If you do not use any directives that place output in the `.text'
or `.data' sections, these sections still exist, but are empty.
ppcas
can also generate whatever other named sections you
specify using the `.space' and `.subspace' directives. See
HP9000 Series 800 Assembly Language Reference Manual
(HP 92432-90001) for details on the `.space' and `.subspace'
assembler directives.
Within the object file, the text section starts at address 0
, the
data section follows, and the bss section follows the data section.
To let link3do
know which data changes when the sections are
relocated, and how to change that data, ppcas
also writes to the
object file details of the relocation needed. To perform relocation
link3do
must know, each time an address in the object
file is mentioned:
(address) - (start-address of section)?
In fact, every address ppcas
ever uses is expressed as
(section) + (offset into section)
Further, most expressions ppcas
computes have this section-relative
nature.
In this manual we use the notation {secname N} to mean "offset N into section secname."
Apart from text, data and bss sections you need to know about the
absolute section. When link3do
mixes partial programs,
addresses in the absolute section remain unchanged. For example, address
{absolute 0}
is "relocated" to run-time address 0 by
link3do
. Although the linker never arranges two partial programs'
data sections with overlapping addresses after linking, by definition
their absolute sections must overlap. Address {absolute 239}
in one
part of a program is always the same address when the program is running as
address {absolute 239}
in any other part of the program.
The idea of sections is extended to the undefined section. Any address whose section is unknown at assembly time is by definition rendered {undefined U}---where U is filled in later. Since numbers are always defined, the only way to generate an undefined address is to mention an undefined symbol. A reference to a named common block would be such a symbol: its value is unknown at assembly time so it has section undefined.
By analogy the word section is used to describe groups of sections in
the linked program. link3do
puts all partial programs' text
sections in contiguous addresses in the linked program. It is
customary to refer to the text section of a program, meaning all
the addresses of all partial programs' text sections. Likewise for
data and bss sections.
Some sections are manipulated by link3do
; others are invented for
use of ppcas
and have no meaning except during assembly.
link3do
deals with just four kinds of sections, summarized below.
ppcas
and link3do
treat them as
separate but equal sections. Anything you can say of one section is
true another.
link3do
must
not change when relocating. In this sense we speak of absolute
addresses being "unrelocatable": they do not change during relocation.
An idealized example of three relocatable sections follows. Memory addresses are on the horizontal axis.
These sections are meant only for the internal use of ppcas
. They
have no meaning at run-time. You do not really need to know about these
sections for most purposes; but they can be mentioned in ppcas
warning messages, so it might be helpful to have an idea of their
meanings to ppcas
. These sections are used to permit the
value of every expression in your assembly language program to be a
section-relative address.
fall into two sections: text and data.
You may have separate groups of
data in named sections
that you want to end up near to each other in the object file, even though they
are not contiguous in the assembler source. ppcas
allows you to
use subsections for this purpose. Within each section, there can be
numbered subsections with values from 0 to 8192. Objects assembled into the
same subsection go into the object file together with other objects in the same
subsection. For example, a compiler might want to store constants in the text
section, but might not want to have them interspersed with the program being
assembled. In this case, the compiler could issue a `.text 0' before each
section of code being output, and a `.text 1' before each group of
constants being output.
Subsections are optional. If you do not use subsections, everything goes in subsection number zero.
Subsections appear in your object file in numeric order, lowest numbered
to highest. (All this to be compatible with other people's assemblers.)
The object file contains no representation of subsections; link3do
and
other programs that manipulate object files see no trace of them.
They just see all your text subsections as a text section, and all your
data subsections as a data section.
To specify which subsection you want subsequent statements assembled
into, use a numeric argument to specify it, in a `.text
expression' or a `.data expression' statement.
You
can also use an extra subsection
argument with arbitrary named sections: `.section name,
expression'.
Expression should be an absolute expression.
(See section Expressions.) If you just say `.text' then `.text 0'
is assumed. Likewise `.data' means `.data 0'. Assembly
begins in text 0
. For instance:
.text 0 # The default subsection is text 0 anyway. .ascii "This lives in the first text subsection. *" .text 1 .ascii "But this lives in the second text subsection." .data 0 .ascii "This lives in the data section," .ascii "in the first data subsection." .text 0 .ascii "This lives in the first text section," .ascii "immediately following the asterisk (*)."
Each section has a location counter incremented by one for every byte
assembled into that section. Because subsections are merely a convenience
restricted to ppcas
there is no concept of a subsection location
counter. There is no way to directly manipulate a location counter--but the
.align
directive changes it, and any label definition captures its
current value. The location counter of the section where statements are being
assembled is said to be the active location counter.
The bss section is used for local common variable storage. You may allocate address space in the bss section, but you may not dictate data to load into it before your program executes. When your program starts running, all the contents of the bss section are zeroed bytes.
Addresses in the bss section are allocated with special directives; you
may not assemble anything directly into the bss section. Hence there
are no bss subsections. See section .comm symbol
, length ,
see section .lcomm symbol
, length.
Symbols are a central concept: the programmer uses symbols to name things, the linker uses symbols to link, and the debugger uses symbols to debug.
Warning:
ppcas
does not place symbols in the object file in the same order they were declared. This may break some debuggers.
A label is written as a symbol immediately followed by a colon `:'. The symbol then represents the current value of the active location counter, and is, for example, a suitable instruction operand. You are warned if you use the same symbol to represent two different locations: the first definition overrides any other definitions.
A symbol can be given an arbitrary value by writing a symbol, followed
by an equals sign `=', followed by an expression
(see section Expressions). This is equivalent to using the .set
directive. See section .set symbol
, expression.
Case of letters is significant: foo
is a different symbol name
than Foo
.
Each symbol has exactly one name. Each name in an assembly language program refers to exactly one symbol. You may use that symbol name any number of times in a program.
Local symbols help compilers and programmers use names temporarily. There are ten local symbol names, which are re-used throughout the program. You may refer to them using the names `0' `1' ... `9'. To define a local symbol, write a label of the form `N:' (where N represents any digit). To refer to the most recent previous definition of that symbol write `Nb', using the same digit as when you defined the label. To refer to the next definition of a local label, write `Nf'---where N gives you a choice of 10 forward references. The `b' stands for "backwards" and the `f' stands for "forwards".
Local symbols are not emitted by the current GNU C compiler.
There is no restriction on how you can use these labels, but remember that at any point in the assembly you can refer to at most 10 prior local labels and to at most 10 forward local labels.
Local symbol names are only a notation device. They are immediately transformed into more conventional symbol names before the assembler uses them. The symbol names stored in the symbol table, appearing in error messages and optionally emitted to the object file have these parts:
L
ppcas
and
link3do
forget symbols that start with `L'. These labels are
used for symbols you are never intended to see. If you use the
`-L' option then ppcas
retains these symbols in the
object file. If you also instruct link3do
to retain these symbols,
you may use them in debugging.
digit
^A
ordinal number
For instance, the first 1:
is named L1^A1
, the 44th
3:
is named L3^A44
.
The special symbol `.' refers to the current address that
ppcas
is assembling into. Thus, the expression `melvin:
.long .' defines melvin
to contain its own address.
Assigning a value to .
is treated the same as a .org
directive. Thus, the expression `.=.+4' is the same as saying
`.space 4'.
Every symbol has, as well as its name, the attributes "Value" and "Type". Depending on output format, symbols can also have auxiliary attributes.
If you use a symbol without defining it, ppcas
assumes zero for
all these attributes, and probably won't warn you. This makes the
symbol an externally defined symbol, which is generally what you
would want.
The value of a symbol is (usually) 32 bits. For a symbol which labels a
location in the text, data, bss or absolute sections the value is the
number of addresses from the start of that section to the label.
Naturally for text, data and bss sections the value of a symbol changes
as link3do
changes section base addresses during linking. Absolute
symbols' values do not change during linking: that is why they are
called absolute.
The value of an undefined symbol is treated in a special way. If it is
0 then the symbol is not defined in this assembler source file, and
link3do
tries to determine its value from other files linked into the
same program. You make this kind of symbol simply by mentioning a symbol
name without defining it. A non-zero value represents a .comm
common declaration. The value is how much common storage to reserve, in
bytes (addresses). The symbol refers to the first address of the
allocated storage.
The type attribute of a symbol contains relocation (section) information, any flag settings indicating that a symbol is external, and (optionally), other information for linkers and debuggers. The exact format depends on the object-code output format in use.
a.out
This is an arbitrary 16-bit value. You may establish a symbol's
descriptor value by using a .desc
statement
(@xref{Desc,,.desc
}). A descriptor value means nothing to
ppcas
.
This is an arbitrary 8-bit value. It means nothing to ppcas
.
An expression specifies an address or numeric value. Whitespace may precede and/or follow an expression.
The result of an expression must be an absolute number, or else an offset into
a particular section. If an expression is not absolute, and there is not
enough information when ppcas
sees the expression to know its
section, a second pass over the source program might be necessary to interpret
the expression--but the second pass is currently not implemented.
ppcas
aborts with an error message in this situation.
An empty expression has no value: it is just whitespace or null.
Wherever an absolute expression is required, you may omit the
expression, and ppcas
assumes a value of (absolute) 0. This
is compatible with other assemblers.
An integer expression is one or more arguments delimited by operators.
Arguments are symbols, numbers or subexpressions. In other contexts arguments are sometimes called "arithmetic operands". In this manual, to avoid confusing them with the "instruction operands" of the machine language, we use the term "argument" to refer to parts of expressions only, reserving the word "operand" to refer only to machine instruction operands.
Symbols are evaluated to yield {section NNN} where section is one of text, data, bss, absolute, or undefined. NNN is a signed, 2's complement 32 bit integer.
Numbers are usually integers.
A number can be a flonum or bignum. In this case, you are warned
that only the low order 32 bits are used, and ppcas
pretends
these 32 bits are an integer. You may write integer-manipulating
instructions that act on exotic constants, compatible with other
assemblers.
Subexpressions are a left parenthesis `(' followed by an integer expression, followed by a right parenthesis `)'; or a prefix operator followed by an argument.
Operators are arithmetic functions, like +
or %
. Prefix
operators are followed by an argument. Infix operators appear
between their arguments. Operators may be preceded and/or followed by
whitespace.
ppcas
has the following prefix operators. They each take
one argument, which must be absolute.
-
~
Infix operators take two arguments, one on either side. Operators
have precedence, but operations with equal precedence are performed left
to right. Apart from +
or -
, both arguments must be
absolute, and the result is absolute.
*
/
%
<
<<
>
>>
|
&
^
!
+
-
In short, it's only meaningful to add or subtract the offsets in an address; you can only have a defined section in one of the two arguments.
All assembler directives have names that begin with a period (`.'). The rest of the name is letters, usually in lower case.
This chapter discusses directives that are available regardless of the target machine configuration for the GNU assembler.
.abort
This directive stops the assembly immediately. It is for
compatibility with other assemblers. The original idea was that the
assembly language source would be piped into the assembler. If the sender
of the source quit, it could use this directive tells ppcas
to
quit also. One day .abort
will not be supported.
.align 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 required, as described below. The second expression (also absolute) gives the value to be stored in the padding bytes. It (and the comma) may be omitted. If it is omitted, the padding bytes are zero.
The way the required alignment is specified varies from system to system. For the a29k, hppa, m86k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF format, the first expression is the alignment request in bytes. For example `.align 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.
For other systems, including the i386 using a.out format, it is the number of low-order zero bits the location counter must have after advancement. For example `.align 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.
This inconsistency is due to the different behaviors of the various
native assemblers for these systems which GAS must emulate.
GAS also provides .balign
and .p2align
directives,
described later, which have a consistent behavior across all
architectures (but are specific to GAS).
.app-file string
.app-file
(which may also be spelled `.file')
tells ppcas
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 is permitted,
you must give the quotes--""
. This statement may go away in
future: it is only recognized to be compatible with old ppcas
programs.
.ascii "string"
...
.ascii
expects zero or more string literals (see section Strings)
separated by commas. It assembles each string (with no automatic
trailing zero byte) into consecutive addresses.
.asciz "string"
...
.asciz
is just like .ascii
, but each string is followed by
a zero byte. The "z" in `.asciz' stands for "zero".
.balign 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 value to be stored in the padding bytes. It (and the comma) may be omitted. If it is omitted, the padding bytes are zero.
.byte expressions
.byte
expects zero or more expressions, separated by commas.
Each expression is assembled into the next byte.
.comm symbol , length
.comm
declares a named common area in the bss section. Normally
link3do
reserves memory addresses for it during linking, so no partial
program defines the location of the symbol. Use .comm
to tell
link3do
that it must be at least length bytes long. link3do
allocates space for each .comm
symbol that is at least as
long as the longest .comm
request in any of the partial programs
linked. length is an absolute expression.
.data subsection
.data
tells ppcas
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.
.double flonums
.double
expects zero or more flonums, separated by commas. It
assembles floating point numbers.
On the Power PC family `.double' emits 64-bit floating-point numbers
in IEEE format.
.eject
Force a page break at this point, when generating assembly listings.
.else
.else
is part of the ppcas
support for conditional
assembly; see section .if absolute expression
. It marks the beginning of a section
of code to be assembled if the condition for the preceding .if
was false.
.endif
.endif
is part of the ppcas
support for conditional assembly;
it marks the end of a block of code that is only assembled
conditionally. See section .if absolute expression
.
.equ symbol, expression
This directive sets the value of symbol to expression.
It is synonymous with `.set'; see section .set symbol
, expression.
.extern
.extern
is accepted in the source program--for compatibility
with other assemblers--but it is ignored. ppcas
treats
all undefined symbols as external.
.file string
.file
(which may also be spelled `.app-file') tells
ppcas
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 ppcas
programs.
.fill repeat , size , value
result, 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 ppcas
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.
.float flonums
This directive assembles zero or more flonums, separated by commas. It
has the same effect as .single
.
On the Power PC family, .float
emits 32-bit floating point numbers
in IEEE format.
.global symbol
, .globl symbol
.global
makes the symbol visible to link3do
. If you define
symbol in your partial program, its value is made available to
other partial programs that are linked with it. Otherwise,
symbol takes its attributes from a symbol of the same name
from another file linked into the same program.
Both spellings (`.globl' and `.global') are accepted, for compatibility with other assemblers.
.hword expressions
This expects zero or more expressions, and emits a 16 bit number for each.
This directive is a synonym for `.short'.
.ident
This directive is used by some assemblers to place tags in object files.
ppcas
simply accepts the directive for source-file
compatibility with such assemblers, but does not actually emit anything
for it.
.if absolute expression
.if
marks the beginning of a section of code which is only
considered part of the source program being assembled if the argument
(which must be an absolute expression) is non-zero. The end of
the conditional section of code must be marked by .endif
(see section .endif
); optionally, you may include code for the
alternative condition, flagged by .else
(see section .else
.
The following variants of .if
are also supported:
.ifdef symbol
.ifndef symbol
ifnotdef symbol
.include "file"
This directive provides a way to include supporting files at specified
points in your source program. The code from file is assembled as
if it followed the point of the .include
; when the end of the
included file is reached, assembly of the original file continues. You
can control the search paths used with the `-I' command-line option
(see section Command-Line Options). Quotation marks are required
around file.
.int expressions
Expect zero or more expressions, of any section, separated by commas. For each expression, emit a number that, at run time, is the value of that expression. The byte order and bit size of the number depends on what kind of target the assembly is for.
.irp symbol,values
...
Evaluate a sequence of statements assigning different values to symbol.
The sequence of statements starts at the .irp
directive, and is
terminated by an .endr
directive. For each value, symbol is
set to value, and the sequence of statements is assembled. If no
value is listed, the sequence of statements is assembled once, with
symbol set to the null string. To refer to symbol within the
sequence of statements, use \symbol.
For example, assembling
.irp param,1,2,3 move d\param,sp@- .endr
is equivalent to assembling
move d1,sp@- move d2,sp@- move d3,sp@-
.irpc symbol,values
...
Evaluate a sequence of statements assigning different values to symbol.
The sequence of statements starts at the .irpc
directive, and is
terminated by an .endr
directive. For each character in value,
symbol is set to the character, and the sequence of statements is
assembled. If no value is listed, the sequence of statements is
assembled once, with symbol set to the null string. To refer to
symbol within the sequence of statements, use \symbol.
For example, assembling
.irpc param,123 move d\param,sp@- .endr
is equivalent to assembling
move d1,sp@- move d2,sp@- move d3,sp@-
.lcomm symbol , length
Reserve length (an absolute expression) bytes for a local common
denoted by symbol. The section and value of symbol are
those of the new local common. The addresses are allocated in the bss
section, so that at run-time the bytes start off zeroed. Symbol
is not declared global (see section .global symbol
, .globl symbol
), so is normally
not visible to link3do
.
.lflags
ppcas
accepts this directive, for compatibility with other
assemblers, but ignores it.
.line line-number
Even though this is a directive associated with the a.out
or
b.out
object-code formats, ppcas
still recognizes it
when producing COFF output, and treats `.line' as though it
were the COFF `.ln' if it is found outside a
.def
/.endef
pair.
Inside a .def
, `.line' is, instead, one of the directives
used by compilers to generate auxiliary symbol information for
debugging.
.ln line-number
`.ln' is a synonym for `.line'.
.list
Control (in conjunction with the .nolist
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.
By default, listings are disabled. When you enable them (with the `-a' command line option; see section Command-Line Options), the initial value of the listing counter is one.
.long expressions
.long
is the same as `.int', see section .int expressions
.
.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 ...
.macro
statements:
.macro comm
comm
, which takes no
arguments.
.macro plus1 p, p1
.macro plus1 p p1
plus1
,
which takes two arguments; within the macro definition, write
`\p' or `\p1' to evaluate the arguments.
.macro reserve_str p1=0 p2
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).
.endm
.exitm
\@
ppcas
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.
.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.
.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.
.org new-lc , fill
Advance the location counter of the current section to
new-lc. new-lc is either an absolute expression 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,
ppcas
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 ppcas
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.
.p2align 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 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 value to be stored in the padding bytes. It (and the comma) may be omitted. If it is omitted, the padding bytes are zero.
.psize lines , columns
Use this directive to declare the number of lines--and, optionally, the number of columns--to use for each page, when generating listings.
If you do not use .psize
, listings use a default line-count
of 60. You may omit the comma and columns specification; the
default width is 200 columns.
ppcas
generates formfeeds whenever the specified number of
lines is exceeded (or whenever you explicitly request one, using
.eject
).
If you specify lines as 0
, no formfeeds are generated save
those explicitly specified with .eject
.
.quad bignums
.quad
expects zero or more bignums, separated by commas. For
each bignum, it emits
an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
warning message; and just takes the lowest order 8 bytes of the bignum.
The term "quad" comes from contexts in which a "word" is two bytes; hence quad-word for 8 bytes.
.rept count
Repeat the sequence of lines between the .rept
directive and the next
.endr
directive count times.
For example, assembling
.rept 3 .long 0 .endr
is equivalent to assembling
.long 0 .long 0 .long 0
.sbttl "subheading"
Use subheading as the title (third line, immediately after the title line) when generating assembly listings.
This directive affects subsequent pages, as well as the current page if it appears within ten lines of the top of a page.
.set symbol, expression
Set the value of symbol to expression. This changes symbol's value and type to conform to expression. If symbol was flagged as external, it remains flagged. (See section Symbol Attributes.)
You may .set
a symbol many times in the same assembly.
If you .set
a global symbol, the value stored in the object
file is the last value stored into it.
.short expressions
This expects zero or more expressions, and emits a 16 bit number for each.
.single flonums
This directive assembles zero or more flonums, separated by commas. It
has the same effect as .float
.
On the Power PC family, .single
emits 32-bit floating point
numbers in IEEE format.
.space size , fill
This directive emits size bytes, each of value fill. Both size and fill are absolute expressions. If the comma and fill are omitted, fill is assumed to be zero.
.stabd, .stabn, .stabs
There are three directives that begin `.stab'.
All emit symbols (see section Symbols), for use by symbolic debuggers.
The symbols are not entered in the ppcas
hash table: they
cannot be referenced elsewhere in the source file.
Up to five fields are required:
link3do
and debuggers choke on silly bit patterns.
If a warning is detected while reading a .stabd
, .stabn
,
or .stabs
statement, the symbol has probably already been created;
you get a half-formed symbol in your object file. This is
compatible with earlier assemblers!
.stabd type , other , desc
.stabd
was
assembled.
.stabn type , other , desc , value
""
.
.stabs string , type , other , desc , value
.string
"str"Copy the characters in str to the object file. You may specify more than one string to copy, separated by commas. Unless otherwise specified for a particular machine, the assembler marks the end of each string with a 0 byte. You can use any of the escape sequences described in section Strings.
.text subsection
Tells ppcas
to assemble the following statements onto the end of
the text subsection numbered subsection, which is an absolute
expression. If subsection is omitted, subsection number zero
is used.
.title "heading"
Use heading as the title (second line, immediately after the source file name and pagenumber) when generating assembly listings.
This directive affects subsequent pages, as well as the current page if it appears within ten lines of the top of a page.
.word expressions
This directive expects zero or more expressions, of any section,
separated by commas.
For each expression, ppcas
emits a 32-bit number.
In order to assemble compiler output into something that works,
ppcas
occasionlly does strange things to `.word' directives.
Directives of the form `.word sym1-sym2' are often emitted by
compilers as part of jump tables. Therefore, when ppcas
assembles a
directive of the form `.word sym1-sym2', and the difference between
sym1
and sym2
does not fit in 16 bits, ppcas
creates a secondary jump table, immediately before the next label.
This secondary jump table is preceded by a short-jump to the
first byte after the secondary table. This short-jump prevents the flow
of control from accidentally falling into the new table. Inside the
table is a long-jump to sym2
. The original `.word'
contains sym1
minus the address of the long-jump to
sym2
.
If there were several occurrences of `.word sym1-sym2' before the
secondary jump table, all of them are adjusted. If there was a
`.word sym3-sym4', that also did not fit in sixteen bits, a
long-jump to sym4
is included in the secondary jump table,
and the .word
directives are adjusted to contain sym3
minus the address of the long-jump to sym4
; and so on, for as many
entries in the original jump table as necessary.
One day these directives won't work. They are included for compatibility with older assemblers.
The PowerPC version of the GNU assembler, ppcas
, has a few machine
dependent options.
ppcas
can assemble code for several different members of the
PowerPCfamily. The default depends upon how ppcas
was configured when it was built; normally, the default is to assemble
code for the PPC 602 microprocessor. The following options may be used to
change the default. These options control which instructions and
addressing modes are permitted. The members of the PowerPC family are
very similar. For detailed information about the differences, see the
Motorola and IBM manuals.
This version of ppcas
uses instructions names and
syntax compatible with most PowerPC manuals. The basic syntax is also
compatible with the Diab assembler, allowing it to assemble the output of the
Diab compiler. Note that the syntax for macros and `.equ' are two
notable incompatibilities.
The following register names are understood:
Local labels in the PowerPC assembler begin with `.L'. No symbolic information will be generated for local labels.
The line-comment character is `#'.
If you have contributed to the GNU assembler and your name isn't listed here,
it is not meant as a slight. We just don't know about it. Send mail to the
maintainer, and we'll correct the situation. Currently
the maintainer is Ken Raeburn (email address raeburn@cygnus.com
).
Dean Elsner wrote the original GNU assembler for the VAX.(1)
Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug information and the 68k series machines, most of the preprocessing pass, and extensive changes in `messages.c', `input-file.c', `write.c'.
K. Richard Pixley maintained GAS for a while, adding various enhancements and many bug fixes, including merging support for several processors, breaking GAS up to handle multiple object file format back ends (including heavy rewrite, testing, an integration of the coff and b.out back ends), adding configuration including heavy testing and verification of cross assemblers and file splits and renaming, converted GAS to strictly ANSI C including full prototypes, added support for m680[34]0 and cpu32, did considerable work on i960 including a COFF port (including considerable amounts of reverse engineering), a SPARC opcode file rewrite, DECstation, rs6000, and hp300hpux host ports, updated "know" assertions and made them work, much other reorganization, cleanup, and lint.
Ken Raeburn wrote the high-level BFD interface code to replace most of the code in format-specific I/O modules.
The original VMS support was contributed by David L. Kashtan. Eric Youngdale has done much work with it since.
The Intel 80386 machine description was written by Eliot Dresselhaus.
Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
The Motorola 88k machine description was contributed by Devon Bowen of Buffalo University and Torbjorn Granlund of the Swedish Institute of Computer Science.
Keith Knowles at the Open Software Foundation wrote the original MIPS back end (`tc-mips.c', `tc-mips.h'), and contributed Rose format support (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to support a.out format.
Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k, tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to use BFD for some low-level operations, for use with the H8/300 and AMD 29k targets.
John Gilmore built the AMD 29000 support, added .include
support, and
simplified the configuration of which versions accept which directives. He
updated the 68k machine description so that Motorola's opcodes always produced
fixed-size instructions (e.g. jsr
), while synthetic instructions
remained shrinkable (jbsr
). John fixed many bugs, including true tested
cross-compilation support, and one bug in relaxation that took a week and
required the proverbial one-bit fix.
Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix), added support for MIPS ECOFF and ELF targets, and made a few other minor patches.
Steve Chamberlain made ppcas
able to generate listings.
Hewlett-Packard contributed support for the HP9000/300.
Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM) along with a fairly extensive HPPA testsuite (for both SOM and ELF object formats). This work was supported by both the Center for Software Science at the University of Utah and Cygnus Support.
Support for ELF format files has been worked on by Mark Eichin of Cygnus Support (original, incomplete implementation for SPARC), Pete Hoogenboom and Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc, and some initial 64-bit support).
Several engineers at Cygnus Support have also provided many small bug fixes and configuration enhancements.
Many others have contributed large or small bugfixes and enhancements. If you have contributed significant work and are not mentioned on this list, and want to be, let us know. Some of the history has been lost; we are not intentionally leaving anyone out.
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