rgbasm - Man Page

Game Boy assembler


rgbasm[-EhLVvw] [-b chars] [-D name[=value]] [-g chars] [-i path] [-M depend_file] [-MG] [-MP] [-MT target_file] [-MQ target_file] [-o out_file] [-p pad_value] [-r recursion_depth] [-W warning] file ...


The rgbasm program creates an RGB object file from an assembly source file. The input file can be a file path, or - denoting stdin.

Note that options can be abbreviated as long as the abbreviation is unambiguous: --verb is --verbose, but --ver is invalid because it could also be --version. The arguments are as follows:

-b chars, --binary-digits chars

Change the two characters used for binary constants. The defaults are 01.

-D 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.

-E, --export-all

Export all labels, including unreferenced and local labels.

-g chars, --gfx-chars chars

Change the four characters used for gfx constants. The defaults are 0123.

-h, --halt-without-nop

By default, rgbasm inserts a nop instruction immediately after any halt instruction. The -h option disables this behavior.

-i path, --include path

Add an include path.

-L, --preserve-ld

Disable the optimization that turns loads of the form LD [$FF00+n8],A into the opcode LDH [$FF00+n8],A in order to have full control of the result in the final ROM.

-M depend_file, --dependfile depend_file

Print make(1) dependencies to depend_file.


To be used in conjunction with -M. This makes rgbasm assume that missing files are auto-generated: when INCLUDE or INCBIN is attempted on a non-existent file, it is added as a dependency, then rgbasm exits normally instead of erroring out. This feature is used in automatic updating of makefiles.


When enabled, this causes a phony target to be added for each dependency other than the main file. This prevents make(1) from erroring out when dependency files are deleted.

-MT 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.

-MQ target_file

Same as -MT, but additionally escapes any special make(1) characters, essentially ‘$’.

-o out_file, --output out_file

Write an object file to the given filename.

-p pad_value, --pad-value pad_value

When padding an image, pad with this value. The default is 0x00.

-r recursion_depth, --recursion-depth recursion_depth

Specifies the recursion depth at which RGBASM will assume being in an infinite loop.

-V, --version

Print the version of the program and exit.

-v, --verbose

Be verbose.

-W 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.


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.


Make the specified 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 is an error if used with a meta warning, such as -Werror=all.

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 flag also has a negation (for example, -Wempty-entry enables the warning that -Wno-empty-entry disables). Only the non-default flag is listed here. Ignoring the “no-” prefix, entries are listed alphabetically.


Warns when WARN-type assertions fail. (See “Aborting the assembly process” in rgbasm(5) for ASSERT).


Warn about incorrect arguments to built-in functions, such as STRSUB() 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 by -1, which yields itself due to integer overflow.


Warn when an empty entry is encountered in a db, dw, dl list. This warning is enabled by -Wextra.


Warn when a constant too large to fit in a signed 32-bit integer is encountered. This warning is enabled by -Wall.


Warn when a string too long to fit in internal buffers is encountered. This warning is enabled by -Wall.


Warn when obsolete constructs such as the jp [hl] instruction or HOME section type are encountered.


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) loses some bits.


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).


Please report bugs on GitHub.

See Also

rgbasm(5), rgbfix(1), rgblink(1), rgbds(5), rgbds(7), gbz80(7)


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

Referenced By

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

July 8, 2019