Fix Debug Mode Crash

(Method #1 by Esrael, Method #2 by Shadow05)

Bug

In Sonic 2 there's a bug the occurs in Debug Mode.

When Placing an object in Debug Mode after dying it crashes the game.

The culprit can be found at the BuildSprites_ObjLoop: or Debug_SpawnObject:

Esrael's Method

At Debug_SpawnObject: you'll see this

	btst	#button_C,(Ctrl_1_Press).w
	beq.s	Debug_ExitDebugMode
	; Spawn object
	jsr	(SingleObjLoad).l

In between beq.s Debug_ExitDebugMode and ; Spawn object add this,

	cmpi.b	#$06,(MainCharacter+status).w	; is Sonic dead?
	bne.s	+				; if not, branch
	rts					; return to prevent Sonic from placing objects.
+

Shadow05's Method

At BuildSprites_ObjLoop: you'll see this.

    if gameRevision=0
	; the additional check prevents a crash triggered by placing an object in debug mode while dead
	; unfortunately, the code it branches *to* causes a crash of its own
	tst.b	id(a0)			; is this object slot occupied?
	beq.w	BuildSprites_Unknown	; if not, branch
	tst.l	mappings(a0)		; does this object have any mappings?
	beq.w	BuildSprites_Unknown	; if not, branch
    else
	; REV01 uses a better branch, but removed the useful check
	tst.b	id(a0)			; is this object slot occupied?
	beq.w	BuildSprites_NextObj	; if not, check next one
    endif

Replace it with this.

	tst.b	id(a0)			; is this object slot occupied?
	beq.w	BuildSprites_NextObj	; if not, check next one
	tst.l	mappings(a0)		; does this object have any mappings?
	beq.w	BuildSprites_NextObj	; if not, check next one

Explanation

This crash occurs because in the Simon Wai Prototype it was a simple branch to command but later builds added this line.

	move.w	(1).w,d0

This is why the game crashes as the word operation is at an odd address.

REV01 tried to fix this by branching to check for the next object but it removes a useful check.

Esrael's method works as it checks if Sonic is dead before placing an object.

My method works as it checks if the object has any mappings.

|Fix Debug Mode Crash]]