🚀 go-pugleaf

In article <15433@cbmvax.commodore.com> valentin@cbmvax.commodore.com (Valentin Pepelea) writes:
   In article <2728cc8d-a00comp.sys.amiga.tech@tronsbox.xei.com>
   dfrancis@tronsbox.xei.com (Dennis Francis Heffernan) writes:
   >
   >	Well, I've hit a good one.  I've finally gotten around to trying to l
   >learn assembly on this beast, and my first program crashes.
   >
   >getvarmem     move #4,a6                    ;get memory for variables
   >              move.b #60,D0
   >              move.l #0,D1
   >              jsr _LVOAllocMem(A6)
   >              bne 1$
   >              jmp giveup                    ;didn't get 60 bytes?  SHEESH!
   >1$            move.l D0,vars                ;stash the address for variables

V:   The first problem is with the first instruction. What is the data width of
V:   that instruction? What data width does your assembler default to? Replace
V:   that instruction with "move.l #4,a6".

	The correct one is:  move.l  4,a6
	Or shorter:          move.l  4.w,a6

	That #4 moves the value 4 into A6. You have to move the address
	which is in 4 to A6.

V:   The second problem is with the test for the return value. Hey, wait a minute,
V:   you are not testing for the return value at all! Here is what you should do:
V:
V:		   jsr	_LVOAllocMem(a6)	; Try to allocate memory
V:		   tst.l	d0			; Is the return value zero?
V:		   beq	giveup			; Branch if so
V:		   move.l	d0,vars			; Stash the address



More comments:

   >getvarmem     move #4,a6                    ;get memory for variables

	move.l  4.w,A6

   >              move.b #60,D0

	moveq.l #60,D0		This one cleans the whole registed. If D0
				contains "something big" before your move.b,
				you only change the lowest byte and D0 will
				contain a big number and you ask for a huge
				amount of memory.

   >              move.l #0,D1

	moveq.l #0,D0		Those "quick" moves produce smaller code
				and are faster.

   >              jsr _LVOAllocMem(A6)

	tst.l D0		Just like Valentin wrote...

   >              bne 1$

	bne.s 1$		Optimization...

   >              jmp giveup                    ;didn't get 60 bytes?  SHEESH!
   >1$            move.l D0,vars                ;stash the address for variables

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