Manual Pages for UNIX Darwin command on man nasm

NASM(1) NASM(1)

NAME

nasm - the Netwide Assembler, a portable 80x86 assembler

SYNOPSIS

nnaassmm [ -ff format ] [ -oo outfile ] [ options... ] infile

nnaassmm -hh

nnaassmm -rr

DESCRIPTION

The nnaassmm command assembles the file infile and directs output to the file outfile if specified. If outfile is not specified, nnaassmm will

derive a default output file name from the name of its input file, usu-

ally by appending `.o' or `.obj', or by removing all extensions for a

raw binary file. Failing that, the output file name will be `nasm.out'.

OOPPTTIIOONNSS

-hh Causes nnaassmm to exit immediately, after giving a summary of its

invocation options, and listing all its supported output file formats.

-aa Causes nnaassmm to assemble the given input file without first

applying the macro preprocessor.

-ee Causes nnaassmm to preprocess the given input file, and write the

output to stdout (or the specified output file name), and not actually assemble anything.

-MM Causes nnaassmm to output Makefile-style dependencies to stdout;

normal output is suppressed.

-EE filename

Causes nnaassmm to redirect error messages to filename. This option

exists to support operating systems on which stderr is not eas-

ily redirected.

-rr Causes nnaassmm to exit immediately, after displaying its version

number. (obsolete)

-vv Causes nnaassmm to exit immediately, after displaying its version

number.

-ff format

Specifies the output file format. Formats include bin, to pro-

duce flat-form binary files, and aout and elf to produce Linux

a.out and ELF object files, respectively.

-oo outfile

Specifies a precise name for the output file, overriding nnaassmm's default means of determining it.

-ll listfile

Causes an assembly listing to be directed to the given file, in which the original source is displayed on the right hand side

(plus the source for included files and the expansions of multi-

line macros) and the generated code is shown in hex on the left.

-ss Causes nnaassmm to send its error messages and/or help text to std-

out instead of stderr.

-ww[+-]foo

Causes nnaassmm to enable or disable certain classes of warning mes-

sages, for example -ww++oorrpphhaann-llaabbeellss or -ww-mmaaccrroo-ppaarraammss to,

respectively, enable warnings about labels alone on lines or disable warnings about incorrect numbers of parameters in macro calls.

-II directory

Adds a directory to the search path for include files. The directory specification must include the trailing slash, as it will be directly prepended to the name of the include file.

-ii directory

Same as the -II option.

-PP file

Specifies a file to be pre-included, before the main source file

starts to be processed.

-pp file

Same as the -PP option.

-DD macro[=value]

Pre-defines a single-line macro.

-dd macro[=value]

Same as the -DD option.

-UU macro

Undefines a single-line macro.

-uu macro

Same as the -UU option.

SSYYNNTTAAXX This man page does not fully describe the syntax of nnaassmm's assembly

language, but does give a summary of the differences from other assem-

blers.

Registers have no leading `%' sign, unlike ggaass, and floating-point

stack registers are referred to as st0, st1, and so on.

Floating-point instructions may use either the single-operand form or

the double. A TO keyword is provided; thus, one could either write fadd st0,st1 fadd st1,st0

or one could use the alternative single-operand forms

fadd st1 fadd to st1 Uninitialised storage is reserved using the RESB, RESW, RESD, RESQ and

REST pseudo-opcodes, each taking one parameter which gives the number

of bytes, words, doublewords, quadwords or ten-byte words to reserve.

Repetition of data items is not done by the DUP keyword as seen in DOS assemblers, but by the use of the TIMES prefix, like this: message: times 3 db 'abc'

times 64-$+message db 0

which defines the string `abcabcabc', followed by the right number of zero bytes to make the total length up to 64 bytes. Symbol references are always understood to be immediate (i.e. the address of the symbol), unless square brackets are used, in which case the contents of the memory location are used. Thus: mov ax,wordvar loads AX with the address of the variable `wordvar', whereas mov ax,[wordvar] mov ax,[wordvar+1] mov ax,[es:wordvar+bx] all refer to the contents of memory locations. The syntaxes mov ax,es:wordvar[bx] es mov ax,wordvar[1] are not legal at all, although the use of a segment register name as an instruction prefix is valid, and can be used with instructions such as LODSB which can't be overridden any other way. Constants may be expressed numerically in most formats: a trailing H, Q or B denotes hex, octal or binary respectively, and a leading `0x' or

`$' denotes hex as well. Leading zeros are not treated specially at

all. Character constants may be enclosed in single or double quotes;

there is no escape character. The ordering is little-endian (reversed),

so that the character constant 'abcd' denotes 0x64636261 and not 0x61626364. Local labels begin with a period, and their `locality' is granted by

the assembler prepending the name of the previous non-local symbol.

Thus declaring a label `.loop' after a label `label' has actually defined a symbol called `label.loop'. DDIIRREECCTTIIVVEESS SECTION name or SEGMENT name causes nnaassmm to direct all following code to the named section. Section names vary with output file format, although most formats support the names .text, .data and .bss. (The

exception is the obj format, in which all segments are user-definable.)

ABSOLUTE address causes nnaassmm to position its notional assembly point at an absolute address: so no code or data may be generated, but you can use RESB, RESW and RESD to move the assembly point further on, and you

can define labels. So this directive may be used to define data struc-

tures. When you have finished doing absolute assembly, you must issue another SECTION directive to return to normal assembly. BITS 16 or BITS 32 switches the default processor mode for which nnaassmm

is generating code: it is equivalent to USE16 or USE32 in DOS assem-

blers. EXTERN symbol and GLOBAL symbol import and export symbol definitions, respectively, from and to other modules. Note that the GLOBAL directive must appear before the definition of the symbol it refers to. STRUC strucname and ENDSTRUC, when used to bracket a number of RESB, RESW or similar instructions, define a data structure. In addition to defining the offsets of the structure members, the construct also defines a symbol for the size of the structure, which is simply the structure name with size tacked on to the end.

FFOORRMMAATT-SSPPEECCIIFFIICC DDIIRREECCTTIIVVEESS

ORG address is used by the bin flat-form binary output format, and

specifies the address at which the output code will eventually be loaded.

GROUP grpname seg1 seg2... is used by the obj (Microsoft 16-bit) out-

put format, and defines segment groups. This format also uses UPPER-

CASE, which directs that all segment, group and symbol names output to the object file should be in uppercase. Note that the actual assembly is still case sensitive.

LIBRARY libname is used by the rdf output format, and causes a depen-

dency record to be written to the output file which indicates that the program requires a certain library in order to run. MMAACCRROO PPRREEPPRROOCCEESSSSOORR

Single-line macros are defined using the %define or %idefine commands,

in a similar fashion to the C preprocessor. They can be overloaded with respect to number of parameters, although defining a macro with no

parameters prevents the definition of any macro with the same name tak-

ing parameters, and vice versa. %define defines macros whose names

match case-sensitively, whereas %idefine defines case-insensitive

macros.

Multi-line macros are defined using %macro and %imacro (the distinction

is the same as that between %define and %idefine), whose syntax is as

follows:

%macro name minprm[-maxprm][+][.nolist] [defaults]

%endmacro

Again, these macros may be overloaded. The trailing plus sign indicates

that any parameters after the last one get subsumed, with their sepa-

rating commas, into the last parameter. The defaults part can be used to specify defaults for unspecified macro parameters after minparam.

%endm is a valid synonym for %endmacro.

To refer to the macro parameters within a macro expansion, you use %1,

%2 and so on. You can also enforce that a macro parameter should con-

tain a condition code by using %+1, and you can invert the condition

code by using %-1. You can also define a label specific to a macro

invocation by prefixing it with a double % sign.

Files can be included using the %include directive, which works like C.

The preprocessor has a `context stack', which may be used by one macro to store information that a later one will retrieve. You can push a

context on the stack using %push, remove one using %pop, and change the

name of the top context (without disturbing any associated definitions)

using %repl. Labels and %define macros specific to the top context may

be defined by prefixing their names with %$, and things specific to the

next context down with %$$, and so on.

Conditional assembly is done by means of %ifdef, %ifndef, %else and

%endif as in C. (Except that %ifdef can accept several putative macro

names, and will evaluate TRUE if any of them is defined.) In addition,

the directives %ifctx and %ifnctx can be used to condition on the name

of the top context on the context stack. The obvious set of `else-if'

directives, %elifdef, %elifndef, %elifctx and %elifnctx are also sup-

ported.

BUGS

There is a reported seg-fault on some (Linux) systems with some large

source files. This appears to be very hard to reproduce. All other known bugs have been fixed... RREESSTTRRIICCTTIIOONNSS There is no support for listing files, symbol maps, or debugging

object-file records. The advanced features of the ELF and Win32 object

file formats are not supported, and there is no means for warning the programmer against using an instruction beyond the capability of the target processor.