🚀 go-pugleaf

In article <809@gould9.UUCP> joel@gould9.UUCP (Joel West) writes:
>This only works for stack-based calls, which are normally limited
>to the toolbox.  For example, if MacMETH doesn't provide assembler,
>and doesn't provide direct access to the file manager, device
>manager, and memory manager, you're SOOL.
>-- 
>	Joel West			     MCI Mail: 282-8879

Actually you don't need a assembler to do OS traps, but some simple
rules are in order.  First OS traps require some glue code to adjust
things correctly for example, and the INLINE directive should be used
instead of the "CODE" procedure:

FROM SYSTEM IMPORT ADDRESS,INLINE,SETREG,REG,ADR,WORD;
CONST A0 = 8; D0 = 0;
PROCEDURE OSEventAvail (mask: WORD; VAR theEvent: EventRecord): BOOLEAN;
BEGIN
	SETREG(8,ADR(theEvent)); SETREG(0,mask);
	CODE(0A030H);
	RETURN(VAL(INTEGER,REG(0)) = 0)
END OSEventAvail;

Rule #2 Don't use WITH statements with INLINE traps. Things will
normally work ok if the WITH closes before the TRAP.  For example the
following may fail:

IMPLEMENTATION MODULE FileManager;
FROM SYSTEM		IMPORT ADR,REG,SETREG,INLINE,WORD;
FROM PascalStrings	IMPORT MakePascalString;
FROM MacTypes		IMPORT OSErr;
FROM FileTypes		IMPORT OSType,ParamBlockRec;
CONST
    OpenTrap	=   0A000H;
    A0		=   8;
    D0		=   0;
...
PROCEDURE FSOpen(VAR Name:ARRAY OF CHAR;vRef:INTEGER;VAR ref:INTEGER):OSErr;
VAR PB:ParamBlockRec; Str:ARRAY[0..255] OF CHAR;
BEGIN
    WITH PB DO
	ioCompletion := NIL; MakePascalString(Name,Str);
	PB.ioNamePtr := ADR(Str); PB.ioVRefNum := vRef;
	PB.ioVersNum := 0C; PB.ioPermssn := 0C; PB.ioMisc := NIL;
	SETREG(A0,ADR(PB)); INLINE(OpenTrap);
	ref := ioRefNum; RETURN(ioResult);
    END;
END FSOpen;
....
But if it is done like this it will work:
    WITH PB DO
	ioCompletion := NIL;
	...
	ioMisc := NIL;
    END;
    SETREG(A0,ADR(PB)); INLINE(OpenTrap);
    ref := ioRefNum;
    RETURN(ioResult);
    ...

Of the things in MacMETH that I want the most are: HFS Search Paths, in
both the Linker and in the Loader for finding object files.  But by the
time that they get that done I will not need MacMETH anymore.  (Hint:
I am working on a MPW version of Modula-2).

Bob Campbell
Teltone Corporation		18520 - 66th AVE NE
P.O. Box 657			Seattle, WA 98155
Kirkland, WA 98033

{amc,dataio,fluke,hplsla,sunup,uw-beaver}!tikal!bobc