22. Running the assembler¶
The assembler is run from the command line, or from an IDE that interfaces with the assembler using the command line.
22.1. Basic invocation¶
The assembler is invoked in the following way:
$ as68k [options] sourcefile [options]
As an example, to assemble a source file with debugging information and a list file, you can use:
$ as68k --debug source.c -l
Command line options are optional arguments that tune the behavior
of the assembler. They always start with a dash character. There are
two variants, single letter options (-l to instruct the assembler
to create a list file) starts with a single dash. The other variant is
long descriptive options that starts with two dashes.
Some options require arguments. These follow the option, separated by a
space or an equals sign (=). For single-argument options, the
separator is optional:
$ as68k -Iinclude source.c -D VERBOSE=2 --list-file=tiny-source.lst
In this case the -I option adds include as a directory to scan
for header files. The symbol VERBOSE is defined in the
preprocessor with value 2. A list file with a specific name is also
produced.
The order in which the options appear normally do matter, except for
the -I option that adds directories to search for header
files. Such directories are searched in the order in which they appear
on the command line.
To display the version of the assembler, use --version:
$ as68k --version
Calypsi assembler for Motorola 68000 version 5.16
Command line options are described in Command line options.
22.2. Include search path¶
Header files are included by surrounding the filename with either double quotes or angled brackets:
#include "myheader.h"
#include <system.h>
Angled brackets are typically for system header files, while double quotes are for application-specific header files.
Note
The installation provides no system header files for the as68k assembler. However, the preprocessor retains its standard behavior of supporting angled include files and searching the installation directory.
The search order for include files is as follows:
Relative to compilation directory (double quote include only)
In directories specified in the
-Ioption in the order they appear on the command lineThe system directory, which is the Calypsi installation directory
Header files specified in angle brackets are not searched relative to the compilation directory. Otherwise, their behavior is identical.
Note
More precisely, the system header file directory is relative to the as68k executable. If you move an installation, it will still find the correct system header file directory.
Note
No header files are currently provided with the assembler. The preprocessor search path exists for consistency with the C compiler.
22.3. Assembler output¶
The assembler outputs one or two files, an object file that can be
linked with other object files and libraries by ln68k to produce an
executable file, and optionally a list file.
Object file¶
The object file is in ELF format, optionally including DWARF debugging
information if --debug (or -g) is specified.
It contains:
A symbol table
Relocatable sections for code and data
Relocations, allowing linker to modify address values after section placement
DWARF-formatted source-level debugging information (if
--debugwas specified)Vendor-specific data, including runtime attributes and additional the Calypsi C compiler tool chain-specific information not covered by ELF/DWARF, used by the linker and debugger, with section types
0x8000000aand0x8000000b.
Note
DWARF version 5 is used. The implementation covers the needs of the Calypsi C compiler tool chain and includes vendor extensions.
Note
DWARF debug information from the assembler includes source line information. The object file also contains a symbol table.
List file¶
The list file is a text file meant to be shown with a fixed width font. It contains a header that shows assembler, version, time when it was created and the command line used. The assembly source is shown with corresponding hex machine code. It also shows macro expansions and includes a summary of code and data sizes.
The following example is the setjmp source file from the C runtime
library:
/****************************************************************************
*
* Copyright Håkan Thörngren
*
* This file is part of the Calypsi C library.
* Permission to use with the Calypsi tool chain is hereby granted.
*
****************************************************************************/
.rtmodel version, "1"
.rtmodel cpu, "*"
.public setjmp
#ifdef __CALYPSI_CODE_MODEL_SMALL__
.section nearcode
#else
.section code
#endif
.align 2
setjmp: move.l sp,(a0)+
move.l a5,(a0)+
move.l (sp),(a0)+
moveq.l #0,d0
rts
#ifdef __CALYPSI_CODE_MODEL_SMALL__
.section nearcode
#else
.section code
#endif
.public longjmp
.align 2
longjmp: move.l (a0)+,sp
move.l (a0)+,a5
move.l (a0)+,(sp)
rts
Compiling with the -l option produces a list file:
###############################################################################
# #
# Calypsi assembler for Motorola 68000 version 5.16 #
# 14/Apr/2026 16:42:00 #
# Command line: setjmp.s -l #
# #
###############################################################################
0001 /****************************************************************************
0002 *
0003 * Copyright Håkan Thörngren
0004 *
0005 * This file is part of the Calypsi C library.
0006 * Permission to use with the Calypsi tool chain is hereby granted.
0007 *
0008 ****************************************************************************/
0009
0010 .rtmodel version, "1"
0011 .rtmodel cpu, "*"
0012
0013 .public setjmp
0014 #ifdef __CALYPSI_CODE_MODEL_SMALL__
0015 .section nearcode
0016 #else
0017 .section code
0018 #endif
0019 .align 2
0020 00000000 20cf setjmp: move.l sp,(a0)+
0021 00000002 20cd move.l a5,(a0)+
0022 00000004 20d7 move.l (sp),(a0)+
0023 00000006 7000 moveq.l #0,d0
0024 00000008 4e75 rts
0025
0026 #ifdef __CALYPSI_CODE_MODEL_SMALL__
0027 .section nearcode
0028 #else
0029 .section code
0030 #endif
0031 .public longjmp
0032 .align 2
0033 00000000 2e58 longjmp: move.l (a0)+,sp
0034 00000002 2a58 move.l (a0)+,a5
0035 00000004 2e98 move.l (a0)+,(sp)
0036 00000006 4e75 rts
##########################
# #
# Memory sizes (decimal) #
# #
##########################
Executable (Text): 18 bytes
22.4. Command line options¶
This section covers the as68k command-line options in detail.
Options overview¶
Running the assembler from the command line without arguments results in a missing input file error, followed by a short help message:
$ as68k
Missing: FILE
Usage: as68k [--version] [-o|--output-file OUTPUT-FILE] [-l]
[--list-file LIST-FILE] [-I DIRECTORY] [-D IDENTIFIER]
[-U IDENTIFIER] [-g|--debug] [--rtattr NAME=VALUE] [--weak-symbols]
[--core CORE] [--target TARGET] [--code-model NAME]
[--data-model NAME] FILE
use 'as68k --help' for detailed help
For more detailed help, use the --help option:
$ as68k --help
Calypsi assembler for Motorola 68000 version 5.16
Usage: as68k [--version] [-o|--output-file OUTPUT-FILE] [-l]
[--list-file LIST-FILE] [-I DIRECTORY] [-D IDENTIFIER]
[-U IDENTIFIER] [-g|--debug] [--rtattr NAME=VALUE] [--weak-symbols]
[--core CORE] [--target TARGET] [--code-model NAME]
[--data-model NAME] FILE
use 'as68k --help' for detailed help
Available options:
--version Display version number
-o,--output-file OUTPUT-FILE
Name of output file
-l Generate a list file, named by appending '.lst' to
input file
--list-file LIST-FILE Generate list file, using given name
-I DIRECTORY Include directory
-D IDENTIFIER Predefine a macro
-U IDENTIFIER #undef a predefined macro
-g,--debug Produce debugging information
--rtattr NAME=VALUE Define a runtime attribute (identifier or quoted
string value accepted)
--weak-symbols Make all public symbols entries weak
--core CORE Core, one of '68000', '68010', '68020', '68030',
'68040', '68060' or '68080' (defaults to '68000')
--target TARGET Target system, one of 'Amiga', 'A2560U', 'A2560K' or
'TOS' (defaults to embedded/ROM use, if omitted)
--code-model NAME Code model, one of 'small' or 'large' (defaults to
'large')
--data-model NAME Data model, one of 'small', 'large' or 'far-only'
(defaults to 'small')
-h,--help Show this help text
Options in detail¶
--version¶
Displays the name and version of the assembler.
--output-file, -o¶
Specify the output object file name. If omitted, the output file is
derived from the input file name (excluding path) with a .o
extension, written to the current directory by default.
This option can also alter the output file name and provide a directory path. The specified directory must already exist.
-l¶
Generate a list file. The name used is the name of the input file
(ignoring any directory path) with a .lst file extension.
See also --list-file.
--list-file¶
Generate a list file. The name of the list file is given as argument
to this option. See also -l to generate a list file based on the
source filename.
-I¶
Add a directory to the current include search path. This option can be used multiple times on a command line. The order in which they appear specifies the search order between the directories.
The system include directory is always added last to the search order list.
--include-system¶
Add a directory to the current system include search path before the provided system include directories. This option can be used multiple times on a command line. The order in which they appear specifies the search order between the directories.
--include-system-after¶
Add a directory to the current system include search path after the provided system include directories. This option can be used multiple times on a command line. The order in which they appear specifies the search order between the directories.
-D¶
Define a macro. This takes an argument with the symbol
name and optionally an assignment value -Dsymbol[=value]. If no
value is given, the macro is given the value 1.
-U¶
Undefine a macro. This takes an argument with the symbol name to be undefined.
--debug¶
Generate DWARF symbolic debugging information. In order to get debugging information all the way to the debugger, the linker must also be given this option.
When debugging information is enabled the __CALYPSI_DEBUG__ macro
is also defined and set to 1.
-g¶
Synonym for --debug.
--rtattr NAME=VALUE¶
This defines a runtime attribute, written to the object file, that the linker can use for object file consistency checks.
--weak-symbols¶
Make all public symbols in the object file weak. This is normally not needed, but can provide a default library function implementation that is used if no replacement is provided.
In the assembler you can also specify symbols to be exported weak
individually using the .pubweak directive.
--core¶
This selects which 68000 core to use. This can either be 68000, 68010, 68020, 68030, 68040, 68060 or 68080. If not specified it defaults to 68000.
--target¶
This option is available for symmetry with the compiler. It has the effect of setting the corresponding target preprocessor macro.
--code-model¶
This option is available for symmetry with the compiler. It has the effect of setting the corresponding code model preprocessor macro.
--data-model¶
This option is available for symmetry with the compiler. It has the effect of setting the corresponding data model preprocessor macro.