nasmdoc.src

一个汇编语言编译器源码

instruction table \c{insns.dat} by a Perl script; the file
\c{macros.c} is generated from \c{standard.mac} by another Perl
script. Although the NASM 0.98 distribution includes these generated
files, you will need to rebuild them (and hence, will need a Perl
interpreter) if you change \c{insns.dat}, \c{standard.mac} or the
documentation. It is possible future source distributions may not
include these files at all.  Ports of \i{Perl} for a variety of
platforms, including DOS and Windows, are available from
\W{http://www.cpan.org/ports/}\i{www.cpan.org}.

\S{instdos} Installing NASM under \i{Unix}

Once you've obtained the \i{Unix source archive} for NASM,
\i\c{nasm-X.XX.tar.gz} (where \c{X.XX} denotes the version number of
NASM contained in the archive), unpack it into a directory such
as \c{/usr/local/src}. The archive, when unpacked, will create its
own subdirectory \c{nasm-X.XX}.

NASM is an \I{Autoconf}\I\c{configure}auto-configuring package: once
you've unpacked it, \c{cd} to the directory it's been unpacked into
and type \c{./configure}. This shell script will find the best C
compiler to use for building NASM and set up \i{Makefiles}
accordingly.

Once NASM has auto-configured, you can type \i\c{make} to build the
\c{nasm} and \c{ndisasm} binaries, and then \c{make install} to
install them in \c{/usr/local/bin} and install the \i{man pages}
\i\c{nasm.1} and \i\c{ndisasm.1} in \c{/usr/local/man/man1}.
Alternatively, you can give options such as \c{--prefix} to the
\c{configure} script (see the file \i\c{INSTALL} for more details), or
install the programs yourself.

NASM also comes with a set of utilities for handling the RDOFF
custom object-file format, which are in the \i\c{rdoff} subdirectory
of the NASM archive. You can build these with \c{make rdf} and
install them with \c{make rdf_install}, if you want them.

If NASM fails to auto-configure, you may still be able to make it
compile by using the fall-back Unix makefile \i\c{Makefile.unx}.
Copy or rename that file to \c{Makefile} and try typing \c{make}.
There is also a \c{Makefile.unx} file in the \c{rdoff} subdirectory.

\C{running} Running NASM

\H{syntax} NASM \i{Command-Line} Syntax

To assemble a file, you issue a command of the form

\c nasm -f <format> <filename> [-o <output>]

For example,

\c nasm -f elf myfile.asm

will assemble \c{myfile.asm} into an ELF object file \c{myfile.o}. And

\c nasm -f bin myfile.asm -o myfile.com

will assemble \c{myfile.asm} into a raw binary file \c{myfile.com}.

To produce a listing file, with the hex codes output from NASM
displayed on the left of the original sources, use the \c{-l} option
to give a listing file name, for example:

\c nasm -f coff myfile.asm -l myfile.lst

To get further usage instructions from NASM, try typing

\c nasm -h

This will also list the available output file formats, and what they
are.

If you use Linux but aren't sure whether your system is \c{a.out} or
ELF, type

\c file nasm

(in the directory in which you put the NASM binary when you
installed it). If it says something like

\c nasm: ELF 32-bit LSB executable i386 (386 and up) Version 1

then your system is ELF, and you should use the option \c{-f elf}
when you want NASM to produce Linux object files. If it says

\c nasm: Linux/i386 demand-paged executable (QMAGIC)

or something similar, your system is \c{a.out}, and you should use
\c{-f aout} instead (Linux \c{a.out} systems are considered obsolete,
and are rare these days.)

Like Unix compilers and assemblers, NASM is silent unless it
goes wrong: you won't see any output at all, unless it gives error
messages.

\S{opt-o} The \i\c{-o} Option: Specifying the Output File Name

NASM will normally choose the name of your output file for you;
precisely how it does this is dependent on the object file format.
For Microsoft object file formats (\i\c{obj} and \i\c{win32}), it
will remove the \c{.asm} \i{extension} (or whatever extension you
like to use - NASM doesn't care) from your source file name and
substitute \c{.obj}. For Unix object file formats (\i\c{aout},
\i\c{coff}, \i\c{elf} and \i\c{as86}) it will substitute \c{.o}. For
\i\c{rdf}, it will use \c{.rdf}, and for the \i\c{bin} format it
will simply remove the extension, so that \c{myfile.asm} produces
the output file \c{myfile}.

If the output file already exists, NASM will overwrite it, unless it
has the same name as the input file, in which case it will give a
warning and use \i\c{nasm.out} as the output file name instead.

For situations in which this behaviour is unacceptable, NASM
provides the \c{-o} command-line option, which allows you to specify
your desired output file name. You invoke \c{-o} by following it
with the name you wish for the output file, either with or without
an intervening space. For example:

\c nasm -f bin program.asm -o program.com
\c nasm -f bin driver.asm -odriver.sys

\S{opt-f} The \i\c{-f} Option: Specifying the \i{Output File Format}

If you do not supply the \c{-f} option to NASM, it will choose an
output file format for you itself. In the distribution versions of
NASM, the default is always \i\c{bin}; if you've compiled your own
copy of NASM, you can redefine \i\c{OF_DEFAULT} at compile time and
choose what you want the default to be.

Like \c{-o}, the intervening space between \c{-f} and the output
file format is optional; so \c{-f elf} and \c{-felf} are both valid.

A complete list of the available output file formats can be given by
issuing the command \i\c{nasm -h}.

\S{opt-l} The \i\c{-l} Option: Generating a \i{Listing File}

If you supply the \c{-l} option to NASM, followed (with the usual
optional space) by a file name, NASM will generate a
\i{source-listing file} for you, in which addresses and generated
code are listed on the left, and the actual source code, with
expansions of multi-line macros (except those which specifically
request no expansion in source listings: see \k{nolist}) on the
right. For example:

\c nasm -f elf myfile.asm -l myfile.lst

\S{opt-E} The \i\c{-E} Option: Send Errors to a File

Under MS-\i{DOS} it can be difficult (though there are ways) to
redirect the standard-error output of a program to a file. Since
NASM usually produces its warning and \i{error messages} on
\i\c{stderr}, this can make it hard to capture the errors if (for
example) you want to load them into an editor.

NASM therefore provides the \c{-E} option, taking a filename argument
which causes errors to be sent to the specified files rather than
standard error. Therefore you can \I{redirecting errors}redirect
the errors into a file by typing

\c nasm -E myfile.err -f obj myfile.asm

\S{opt-s} The \i\c{-s} Option: Send Errors to \i\c{stdout}

The \c{-s} option redirects \i{error messages} to \c{stdout} rather
than \c{stderr}, so it can be redirected under MS-\i{DOS}.  To
assemble the file \c{myfile.asm} and pipe its output to the \c{more}
program, you can type:

\c nasm -s -f obj myfile.asm | more

See also the \c{-E} option, \k{opt-E}.

\S{opt-i} The \i\c{-i}\I\c{-I} Option: Include File Search Directories

When NASM sees the \i\c{%include} directive in a source file (see
\k{include}), it will search for the given file not only in the
current directory, but also in any directories specified on the
command line by the use of the \c{-i} option. Therefore you can
include files from a \i{macro library}, for example, by typing

\c nasm -ic:\\macrolib\\ -f obj myfile.asm

(As usual, a space between \c{-i} and the path name is allowed, and
optional).

NASM, in the interests of complete source-code portability, does not
understand the file naming conventions of the OS it is running on;
the string you provide as an argument to the \c{-i} option will be
prepended exactly as written to the name of the include file.
Therefore the trailing backslash in the above example is necessary.
Under Unix, a trailing forward slash is similarly necessary.

(You can use this to your advantage, if you're really \i{perverse},
by noting that the option \c{-ifoo} will cause \c{%include "bar.i"}
to search for the file \c{foobar.i}...)

If you want to define a \e{standard} \i{include search path},
similar to \c{/usr/include} on Unix systems, you should place one or
more \c{-i} directives in the \c{NASM} environment variable (see
\k{nasmenv}).

For Makefile compatibility with many C compilers, this option can also
be specified as \c{-I}.

\S{opt-p} The \i\c{-p}\I\c{-P} Option: \I{pre-including files}Pre-Include a File

\I\c{%include}NASM allows you to specify files to be
\e{pre-included} into your source file, by the use of the \c{-p}
option. So running

\c nasm myfile.asm -p myinc.inc

is equivalent to running \c{nasm myfile.asm} and placing the
directive \c{%include "myinc.inc"} at the start of the file.

For consistency with the \c{-I}, \c{-D} and \c{-U} options, this
option can also be specified as \c{-P}.

\S{opt-d} The \i\c{-d}\I\c{-D} Option: \I{pre-defining macros} Pre-Define a Macro

\I\c{%define}Just as the \c{-p} option gives an alternative to placing
\c{%include} directives at the start of a source file, the \c{-d}
option gives an alternative to placing a \c{%define} directive. You
could code

\c nasm myfile.asm -dFOO=100

as an alternative to placing the directive

\c %define FOO 100

at the start of the file. You can miss off the macro value, as well:
the option \c{-dFOO} is equivalent to coding \c{%define FOO}. This
form of the directive may be useful for selecting \i{assembly-time
options} which are then tested using \c{%ifdef}, for example
\c{-dDEBUG}.

For Makefile compatibility with many C compilers, this option can also
be specified as \c{-D}.

\S{opt-u} The \i\c{-u}\I\c{-U} Option: \I{Undefining macros} Undefine a Macro

\I\c{%undef}The \c{-u} option undefines a macro that would otherwise
have been pre-defined, either automatically or by a \c{-p} or \c{-d}
option specified earlier on the command lines.

For example, the following command line:

\c nasm myfile.asm -dFOO=100 -uFOO

would result in \c{FOO} \e{not} being a predefined macro in the
program.  This is useful to override options specified at a different
point in a Makefile.

For Makefile compatibility with many C compilers, this option can also
be specified as \c{-U}.

\S{opt-e} The \i\c{-e} Option: Preprocess Only

NASM allows the \i{preprocessor} to be run on its own, up to a
point. Using the \c{-e} option (which requires no arguments) will
cause NASM to preprocess its input file, expand all the macro
references, remove all the comments and preprocessor directives, and
print the resulting file on standard output (or save it to a file,
if the \c{-o} option is also used).

This option cannot be applied to programs which require the
preprocessor to evaluate \I{preprocessor expressions}\i{expressions}
which depend on the values of symbols: so code such as

\c %assign tablesize ($-tablestart)

will cause an error in \i{preprocess-only mode}.

\S{opt-a} The \i\c{-a} Option: Don't Preprocess At All

If NASM is being used as the back end to a compiler, it might be
desirable to \I{suppressing preprocessing}suppress preprocessing
completely and assume the compiler has already done it, to save time
and increase compilation speeds. The \c{-a} option, requiring no
argument, instructs NASM to replace its powerful \i{preprocessor}
with a \i{stub preprocessor} which does nothing.

\S{opt-w} The \i\c{-w} Option: Enable or Disable Assembly \i{Warnings}

NASM can observe many conditions during the course of assembly which
are worth mentioning to the user, but not a sufficiently severe
error to justify NASM refusing to generate an output file. These
conditions are reported like errors, but come up with the word
`warning' before the message. Warnings do not prevent NASM from
generating an output file and returning a success status to the
operating system.

Some conditions are even less severe than that: they are only
sometimes worth mentioning to the user. Therefore NASM supports the
\c{-w} command-line option, which enables or disables certain
classes of assembly warning. Such warning classes are described by a
name, for example \c{orphan-labels}; you can enable warnings of
this class by the command-line option \c{-w+orphan-labels} and
disable it by \c{-w-orphan-labels}.

The \i{suppressible warning} classes are:

\b \i\c{macro-params} covers warnings about \i{multi-line macros}
being invoked with the wrong number of parameters. This warning
class is enabled by default; see \k{mlmacover} for an example of why
you might want to disable it.