object file format documentation
This is the description of the object files used by rgbasm(1)
and rgblink(1). Please note that the
specifications may change. This toolchain is in development and new
features may require adding more information to the current format, or
modifying some fields, which would break compatibility with older versions.
The following types are used:
LONG is a 32‐bit integer stored in
little‐endian format. BYTE is an 8‐bit
integer. STRING is a 0‐terminated string of
Expressions in the object file are stored as RPN. This is an expression of the
form “2 5 +”. This will first push the value “2”
to the stack, then “5”. The “+” operator pops two
arguments from the stack, adds them, and then pushes the result on the stack,
effectively replacing the two top arguments with their sum. In the RGB format,
RPN expressions are stored as BYTEs with some bytes
being special prefixes for integers and symbols.
BYTE ID ; "RGB9"
LONG RevisionNumber ; The format's revision number this file uses
LONG NumberOfSymbols ; The number of symbols used in this file
LONG NumberOfSections ; The number of sections used in this file
REPT NumberOfSymbols ; Number of symbols defined in this object file.
STRING Name ; The name of this symbol. Local symbols are stored
; as "Scope.Symbol".
BYTE Type ; 0 = LOCAL symbol only used in this file.
; 1 = IMPORT this symbol from elsewhere
; 2 = EXPORT this symbol to other objects.
; Bit 7 is independent from the above value, and
; encodes whether the section is unionized
IF (Type & 0x7F) != 1 ; If symbol is defined in this object file.
STRING FileName ; File where the symbol is defined.
LONG LineNum ; Line number in the file where the symbol is defined.
LONG SectionID ; The section number (of this object file) in which
; this symbol is defined. If it doesn't belong to any
; specific section (like a constant), this field has
; the value -1.
LONG Value ; The symbols value. It's the offset into that
; symbol's section.
STRING Name ; Name of the section
LONG Size ; Size in bytes of this section
BYTE Type ; 0 = WRAM0
; 1 = VRAM
; 2 = ROMX
; 3 = ROM0
; 4 = HRAM
; 5 = WRAMX
; 6 = SRAM
; 7 = OAM
LONG Org ; Address to fix this section at. -1 if the linker should
; decide (floating address).
LONG Bank ; Bank to load this section into. -1 if the linker should
; decide (floating bank). This field is only valid for ROMX,
; VRAM, WRAMX and SRAM sections.
LONG Align ; Alignment of this section, expressed as 1 << align. 1 if
; not specified.
IF (Type == ROMX) || (Type == ROM0) ; Sections that can contain data.
BYTE Data[Size] ; Raw data of the section.
LONG NumberOfPatches ; Number of patches to apply.
; These types of sections may have patches
STRING SourceFile ; Name of the source file (for printing error
LONG Offset ; Offset into the section where patch should
; be applied (in bytes).
BYTE Type ; 0 = BYTE patch.
; 1 = little endian WORD patch.
; 2 = little endian LONG patch.
; 3 = JR offset value BYTE patch.
LONG RPNSize ; Size of the buffer with the RPN.
BYTE RPN[RPNSize] ; RPN expression. Definition below.
STRING SourceFile ; Name of the source file (for printing the failure).
LONG Offset ; Offset into the section where the assertion is located.
BYTE Type ; 0 = Prints the message but allows linking to continue
; 1 = Prints the message and evaluates other assertions,
; but linking fails afterwards
; 2 = Prints the message and immediately fails linking
LONG RPNSize ; Size of the RPN expression's buffer.
BYTE RPN[RPNSize] ; RPN expression, same as patches. Assert fails if == 0.
LONG SectionID ; The section number (of this object file) in which this
; assert is defined. If it doesn't belong to any specific
; section (like a constant), this field has the value -1.
STRING Message ; A message displayed when the assert fails. If set to
; the empty string, a generic message is printed instead.
rgbds 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