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rgbasm

Game Boy assembler

rgbasm [-EhVvw] [-B param] [-b chars] [--color when] [-D name[=value]] [-g chars] [-I path] [-M depend_file] [-MG] [-MC] [-MP] [-MT target_file] [-MQ target_file] [-o out_file] [-P include_file] [-p pad_value] [-Q fix_precision] [-r recursion_depth] [-s features:state_file] [-W warning] [-X max_errors] asmfile

The rgbasm program creates an RGB object file from an assembly source file. The object file format is documented in rgbds(5).

rgbasm accepts the usual short and long options, such as -V and --version. Options later in the command line override those set earlier, except for when duplicate options are considered an error. Options can be abbreviated as long as the abbreviation is unambiguous: --verb is --verbose, but --ver is invalid because it could also be --version.

Unless otherwise noted, passing ‘-’ (a single dash) as a file name makes rgbasm use standard input (for input files) or standard output (for output files). To suppress this behavior, and open a file in the current directory actually called ‘-’, pass ‘./-’ instead. Using standard input or output for more than one file in a single command may produce unexpected results.

rgbasm accepts decimal, hexadecimal, octal, and binary for numeric option arguments. Decimal numbers are written as usual; hexadecimal numbers must be prefixed with either ‘$’ or ‘0x’; octal numbers must be prefixed with either ‘&’ or ‘0o’; and binary numbers must be prefixed with either ‘%’ or ‘0b’. (The prefixes ‘$’ and ‘&’ will likely need escaping or quoting to avoid being interpreted by the shell.) Leading zeros (after the base prefix, if any) are accepted, and letters are not case-sensitive. For example, all of these are equivalent: ‘42’, ‘042’, ‘0x2A’, ‘0X2A’, ‘0x2a’, ‘&52’, ‘0o52’, ‘0O052’, ‘0b00101010’, ‘0B101010’.

The following options are accepted:

param, --backtrace param
Configures how location backtraces are printed if warnings or errors occur. This flag may be specified multiple times with different parameters that combine meaningfully. If param is a positive number, it specifies the maximum backtrace depth, abbreviating deeper ones. Other valid parameter values are the following:
Do not limit the maximum backtrace depth; this is the default.
Force all locations to be printed, even "quiet" ones (see “Excluding locations from backtraces” in rgbasm(5) for details).
Do not print "quieted" locations in backtraces; this is the default.
Print all locations on one line.
Print one location per line; this is the default.
chars, --binary-digits chars
Allow two characters to be used for binary constants in addition to the default ‘0’ and ‘1’. Valid characters are numbers other than ‘0’ and ‘1’, letters, ‘.’, ‘#’, or ‘@’.
when
Specify when to highlight warning and error messages with color: ‘always’, ‘never’, or ‘auto’. ‘auto’ determines whether to use colors based on the ‘NO_COLOR’ or ‘FORCE_COLOR’ environment variables, or whether the output is to a TTY.
name[=value], --define name[=value]
Add a string symbol to the compiled source code. This is equivalent to ‘name EQUS "value"’ in code, or ‘name EQUS "1"’ if value is not specified.
, --export-all
Export all labels, including unreferenced and local labels.
chars, --gfx-chars chars
Allow four characters to be used for graphics constants in addition to the default ‘0’, ‘1’, ‘2’, and ‘3’. Valid characters are numbers other than ‘0’ to ‘3’, letters, ‘.’, ‘#’, or ‘@’. The defaults are 0123.
, --help
Print help text for the program and exit.
path, --include path
Add a new “include path”; path must point to a directory. When any INCLUDE (including the implicit one from -P), INCBIN, or READFILE is attempted, rgbasm first looks up the provided path from its working directory; if this fails, it tries again from each of the “include path” directories, in the order they were provided.
depend_file, --dependfile depend_file
Write make(1) dependencies to depend_file.
To be used in conjunction with -M. This makes rgbasm assume that missing files are auto-generated: when any INCLUDE (including the implicit one from -P), INCBIN, or READFILE is attempted on a non-existent file, it is added as a dependency, then rgbasm exits normally or continues processing (depending on whether -MC was enabled) instead of erroring out. This feature is used in automatic updating of Makefiles.
Implies -MG. This makes rgbasm continue processing after a non-existent dependency file, instead of exiting. Note that this is recommended if any non-existent dependencies would have influenced subsequent processing, e.g. by causing an IF condition to take a different branch.
When enabled, this adds a phony target to the rules emitted by -M for each dependency other than the main file. This prevents make(1) from erroring out when dependency files are deleted.
target_file
Add a target to the rules emitted by -M. The exact string provided will be written, including spaces and special characters.
-MT fileA -MT fileB
is equivalent to
-MT 'fileA fileB'
. If neither this nor -MQ is specified, the output file name is used.
target_file
Same as -MT, but additionally escapes any special make(1) characters, essentially ‘$’.
out_file, --output out_file
Write an object file to the given filename.
include_file, --preinclude include_file
Pre-include a file. This acts as if a ‘INCLUDE "include_file"’ was read before the input asmfile. Multiple files can be pre-included in the order they were provided.
pad_value, --pad-value pad_value
Use this as the value for DS directives in ROM sections, unless overridden. The default is 0x00.
fix_precision, --q-precision fix_precision
Use this as the precision of fixed-point numbers after the decimal point, unless they specify their own precision. The default is 16, so fixed-point numbers are Q16.16 (since they are 32-bit integers). The argument may start with a ‘.’ to match the Q notation, for example, ‘-Q .16’.
recursion_depth, --recursion-depth recursion_depth
Specifies the recursion depth past which rgbasm will assume being in an infinite loop. The default is 64.
features:state_file, --state features:state_file
Write the specified features to state_file, based on the final state of rgbasm at the end of its input. The expected features are a comma-separated subset of the following:
Write all numeric constants as ‘def name equ value’.
Write all variables as ‘def name = value’.
Write all string constants as ‘def name equs "value"’.
Write all characters as ‘charmap name, value’.
Write all macros as ‘macro name ... endm’.
Acts like equ,var,equs,char,macro.

This flag may be specified multiple times with different feature subsets to write them to different files (see EXAMPLES below).

, --version
Print the version of the program and exit.
, --verbose
Be verbose. The verbosity level is increased by one each time the flag is specified, with each level including the previous:
  1. Print the rgbasm configuration before taking actions.
  2. Print a notice before significant actions.
  3. Print some of the actions' intermediate results.
  4. Print some internal debug information.
  5. Print detailed internal information.
The verbosity level does not go past 6.

Note that verbose output is only intended to be consumed by humans, and may change without notice between RGBDS releases; relying on those for scripts is not advised.

warning, --warning warning
Set warning flag warning. A warning message will be printed if warning is an unknown warning flag. See the DIAGNOSTICS section for a list of warnings.
Disable all warning output, even when turned into errors.
max_errors, --max-errors max_errors
If more than this number of errors (not warnings) occur, then abort the assembly process; -X 0 disables this behavior. The default is 100 if rgbasm is printing errors to a terminal, and 0 otherwise.
@at_file
Read more options and arguments from a file, as if its contents were given on the command line. Arguments are separated by whitespace or newlines. Lines starting with a hash sign (‘#’) are considered comments and ignored.

No shell processing is performed, such as wildcard or variable expansion. There is no support for escaping or quoting whitespace to be included in arguments. The standard ‘--’ to stop option processing also disables at-file processing. Note that while ‘--’ can be used an at-file, it only disables option processing within that at-file, and processing continues in the parent scope.

Warnings are diagnostic messages that indicate possibly erroneous behavior that does not necessarily compromise the assembling process. The following options alter the way warnings are processed.

Make all warnings into errors. This can be negated as -Wno-error to prevent turning all warnings into errors.
Make the specified warning or meta warning into an error. A warning's name is appended (example: -Werror=obsolete), and this warning is implicitly enabled and turned into an error. This can be negated as -Wno-error= to prevent turning a specified warning into an error, even if -Werror is in effect.

The following warnings are “meta” warnings, that enable a collection of other warnings. If a specific warning is toggled via a meta flag and a specific one, the more specific one takes priority. The position on the command-line acts as a tie breaker, the last one taking effect.

This enables warnings that are likely to indicate an error or undesired behavior, and that can easily be fixed.
This enables extra warnings that are less likely to pose a problem, but that may still be wanted.
Enables literally every warning.

The following warnings are actual warning flags; with each description, the corresponding warning flag is included. Note that each of these flags also has a negation (for example, -Wobsolete enables the warning that -Wno-obsolete disables; and -Wall enables every warning that -Wno-all disables). Only the non-default flag is listed here. Ignoring the “no-” prefix, entries are listed alphabetically.

Warn when WARN-type assertions fail. (See “Aborting the assembly process” in rgbasm(5) for ASSERT).
Warn when FOR loops have their start and stop values switched according to the step value. This warning is enabled by -Wall.
Warn about incorrect arguments to built-in functions, such as STRSLICE() with indexes outside of the string's bounds. This warning is enabled by -Wall.
Warn when re-defining a charmap mapping. This warning is enabled by -Wall.
Warn when dividing the smallest negative integer (-2**31) by -1, which yields itself due to integer overflow.
Warn when DB, DW, or DL is used without an argument in a ROM section. This warning is enabled by -Wall.
Warn when a macro argument is empty. This warning is enabled by -Wextra.
Warn when STRRPL() is called with an empty string as its second argument (the substring to replace). This warning is enabled by -Wall.
Warn when exporting an undefined symbol. This warning is enabled by -Wall.
Warn when a constant too large to fit in a signed 32-bit integer is encountered.
Warn when shifting macro arguments past their limits. This warning is enabled by -Wextra.
Warn when the block comment start sequence ‘/*’ is found inside of a block comment. Block comments cannot be nested, so the first ‘*/’ will end the whole comment.
Warn when obsolete features are encountered, which have been deprecated and may later be removed.
Warn when a multi-character string is treated as a number. -Wnumeric-string=0 or -Wno-numeric-string disables this warning. -Wnumeric-string=1 or just -Wnumeric-string warns about strings longer than four characters, since four or fewer characters fit within a 32-bit integer. -Wnumeric-string=2 warns about any multi-character string.
Warn when purging symbols which are likely to have been necessary. -Wpurge=0 or -Wno-purge disables this warning. -Wpurge=1 warns when purging any exported symbol (regardless of type). -Wpurge=2 or just -Wpurge also warns when purging any label (even if not exported).
Warn when shifting right a negative value. Use a division by 2**N instead.
Warn when a shift's operand is negative or greater than 32.
Warn when an implicit truncation (for example, db to an 8-bit value) loses some bits. -Wtruncation=0 or -Wno-truncation disables this warning. -Wtruncation=1 or just -Wtruncation warns when an N-bit value is 2**N or greater, or less than -2**N. -Wtruncation=2 also warns when an N-bit value is less than -2**(N-1), which will not fit in two's complement encoding.
Warn when a character goes through charmap conversion but has no defined mapping. -Wunmapped-char=0 or -Wno-unmapped-char disables this warning. -Wunmapped-char=1 or just -Wunmapped-char only warns if the active charmap is not empty. -Wunmapped-char=2 warns if the active charmap is empty, and/or is not the default charmap ‘main’.
Warn when a PUSHC, PUSHO, or PUSHS directive does not have a corresponding POPC, POPO, or POPS. This warning is enabled by -Wextra.
Warn when a LOAD block is not terminated by an ENDL. This warning is enabled by -Wextra.
Warn when the WARN built-in is executed. (See “Aborting the assembly process” in rgbasm(5) for WARN).

You can assemble a source file in two ways.

Straightforward way:

$ rgbasm -o bar.o foo.asm

Pipes way:

$ cat foo.asm | rgbasm -o bar.o -
$ rgbasm -o bar.o - < foo.asm

The resulting object file is not yet a usable ROM image—it must first be run through rgblink(1) and then rgbfix(1).

Writing the final assembler state to a file:

$ rgbasm -s all:state.dump.asm foo.asm

Or to multiple files:

$ rgbasm -s equ,var:numbers.dump.asm -s equs:strings.dump.asm foo.asm

Please report bugs or mistakes in this documentation on GitHub.

rgbasm(5), rgblink(1), rgbfix(1), rgbgfx(1), gbz80(7), rgbasm-old(5), rgbds(5), rgbds(7)

rgbasm was originally written by Carsten Sørensen as part of the ASMotor package, and was later repackaged in RGBDS by Justin Lloyd. It is now maintained by a number of contributors at https://github.com/gbdev/rgbds.