Specifics

Specific implementations/changes for Free Pascal on Amiga systems

in Relation to other Free Pascal implementations

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Compiler defines

There are several compiler defines (table G.4) available for Free Pascal. More on multiplatform programming can be found here.

Definition HASAMIGA	With this definition you can can determine if you are on any of the Amiga platforms (also future proof for future Amiga platforms). Use it to encapsulate code parts (or uses) for all Amiga-style systems {$ifdef HASAMIGA} {$endif} or disable parts which does not work on all Amiga-style systems via {$ifndef HASAMIGA} {$endif}
Definition AMIGA	This definition exists in FreePascal for Amiga m68k and Amiga PowerPC (OS4) only. Do separate Amiga m68k and OS4 you can use the processor defines M68K and POWERPC or the specialized defines AMIGA68k and AMIGAOS4.
Definition MORPHOS	This definition exists in FreePascal for MorphOS.
Definition AROS	This definition exists in FreePascal for AROS. This enables you to determine if your program is compiled/targeted for AROS or not. You can use {$IFDEF AROS} or {$IFNDEF AROS} to make use of this define. ABI define AROS_ABIv0 and AROS_ABIv1 NOTE: There is no dedicated AROS m68k Version, the released Version is the Amiga m68k version because AROS m68k is binary compatible to Amiga classic.

Tree structure of Amiga related platform defines:

• HASAMIGA (defined since FPC 3.0)
  • AMIGA (Classic and new)
    • AMIGA68K (Classic Amiga OS, defined since FPC 3.0.2)
    • AMIGAOS4 (Amiga OS4)
  • AROS (AROS)
    • AROS_ABIv0 (AROS v0 ABI)
    • AROS_ABIv1 (AROS v1 ABI)
  • MORPHOS (MorphOS)

Additional System unit contents

System unit has some additional functions and variables:

Be warned if you change any of the variables then your program will crash and most likely your computer as well.

SysDebug(Msg: ShortString); SysDebugLn(Msg: ShortString);	Write a message to debug output of the system. To read this debug messages you need a special tool to catch the messages (AROS: sashimi, hosted AROS: consoleoutput; MorphOS/AmigaOS4: LogTool) SysDebugLn() adds a return after the message, SysDebug() does not. NOTE: The Msg parameter is a ShortString, so must not be longer than 255 chars.
AOS_WbMsg: Pointer;	Real Type is PWBStartup (from "Workbench" unit) can be used to determine if the program was started from WB (if this pointer is Nil then it was started from CLI)
AOS_ExecBase: Pointer;	Real type is: PExecBase (from "Exec" Unit) can be used to call all exec.library calls, or to inspect system basic features
AOS_DOSBase: Pointer;	Real type is: PDOSBase (from "AmigaDos" Unit) can be used to call all dos.library calls
AOS_UtilityBase: Pointer;	Real type is: PUtilityBase (from "Utility" Unit) can be used to call all utility.library calls
AOS_heapPool: Pointer;	Its a Pool Header created with (CreatePool from exec), all memory allocations are created in this pool, could be used to AllocPooled memory as well (even AllocMem, New and so on do it automatically)

Threading

athreads	This unit is needed if the program wants to use threads. It must be added as very first uses in the main source file. it is comparable to the cthreads units of freepascal for linux.

Syscalls

For all Amiga systems a special calling convention for calls into a Amiga-style (.library) with the keyword syscall. A typical Library call looks like this:

procedure FktName(parameters); syscall Base Offset;

Parameter	AROS(i386, x86_64, ARM), AmigaOS4: Parameter of the function with type: param: type AmigaOS3, MorphOS: Parameter of the function with type and location: param: type location 'register' register is a standard m68k register 'd0'-'d7','a0'-'a6'
Base	AmigaOS3, AROS, MorphOS: LibraryBase from OpenLibrary(); AmigaOS4: Interface of the Library from GetInterface();
Offset	AmigaOS3, MorphOS, AmigaOS4: Offset relative to the Base AROS: Offset relative to the Base divided by the size of a Pointer (therefore its the same value for 64 bit and 32bit)

Call Library shows how to create syscalls for the different platforms and how to gather the needed informations

Further informations about syscalls: AmigaOS3, AmigaOS4, MorphOS

Relation to other languages on AROS/Amiga

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Not really compiler related, but more about how ones program should behave, look and act on an amiganoid system.

There is a document called "Amiga User Interface Style Guide" [1] that cover some of the basic techniques that should be practised when programming for amiganoid systems. Of course, it would be impossible to follow them all (if even for the GUI differences) but there are a couple of interesting topics in there:

Embedded version IDs: [2]	Gives the programmer the ability to let the system 'interrogate' your program (executable) and displays version information (from either commandline tool version or by using the icon information menu from the workbench). To put it simply, add a const string in generic version format: $VER: <name> <version>.<revision> (<d>.<m>.<y>)

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Changed Unit Names

Library name in AROS	corresponding Free Pascal Unit	Collision with
graphics.libray	agraphics	Graphics unit from LCL
dos.library	amigados	Dos unit from RTL

Also note that the usage of unit amigalib is deprecated. The functions that resided in this unit can now be found in their respective counterpart units e.g. graphic related function can now be found inside unit AGraphics, Intuition related functions can now be found inside unit Intuition, etc.

Changed constants/function Names

type	Original Name	Free Pascal Name	Collision with
Exec.Library (exec)
function	AllocMem	ExecAllocMem	AllocMem() in System
procedure	FreeMem	ExecFreeMem	FreeMem() in System
procedure	Insert	ExecInsert	Insert() in System
procedure	Exception	ExecException	Exception keyword
dos.Library (amigados)
procedure	Close	DOSClose	Collides with Close() function in unit System
function	CreateDir	DOSCreateDir	Collides with CreateDir() function in unit SysUtils
function	DateToStr	DOSDateToStr	Collides with DateToStr() function in unit SysUtils
procedure	Delay	DOSDelay	Collides with Delay() function in unit CRT
procedure	DeleteFile	DOSDeleteFile	Collides with DeleteFile() function in unit SysUtils
procedure	Exit	DOSExit	Collides with Exit() function in unit System
procedure	Flush	DOSFlush	Collides with Flush() function in unit System
function	Format	DOSFormat	Collides with Format() function in unit SysUtils
variable	Input	DOSInput	Collides with Input() variable in unit System
procedure	Open	DOSOpen	For consistency with other dos functions
variable	Output	DOSOutput	Collides with Output() variable in unit System
procedure	Read	DOSRead	Collides with Read() function in unit System
procedure	Rename	DOSRename	Collides with Rename() function in unit System
procedure	Seek	DOSSeek	Collides with Seek() function in unit System
function	StrToDate	DOSStrToDate	Collides with StrToDate() function in unit SysUtils
function	System	DOSSystem	For consistency with other dos functions
procedure	Write	DOSWrite	Collides with Write() function in unit System
Graphics.Library (agraphics)
procedure	Move	GfxMove	Move() in System
procedure	Text	GfxText	Text type
Intuition.Library (intuition)
const	SINGLE	SINGLE_PT	Single type
const	FANFOLD	FANFOLD_PT	(renamed because of Single renaming)
const	WBENCHSCREEN	WBENCHSCREEN_f
const	PUBLICSCREEN	PUBLICSCREEN_f
const	CUSTOMSCREEN	CUSTOMSCREEN_f
const	SCREENTYPE	SCREENTYPE_f
const	SHOWTITLE	SHOTITLE_f
const	BEEPING	BEEPING_f
const	CUSTOMBITMAP	CUSTOMBITMAP_f
const	SCREENBEHIND	SCREENBEHIND_f