WHD isntall problem

[Belgarath]

You ever going to fix the typo in the thread title?

[BippyM]

No it makes the thread title unique

[StingRay]

Originally Posted by bippym

so it is allocating 78bytes of best-Available ram!

Close but no cigar It's allocating cleared mem.

Hmmm.. i'm figuring stack out more than anything.. it's the movem.l(4,sp)d0/d1 as I presume it adds 4 to the stack.. which is kinda backwards to me

The 4(a7) is just to get the right things from the stack. When calling a subroutine the return address is pushed onto the stack thus the offset to skip that very return address. If the Allocmem would have been called directly (i.e. without any jsr) you would not need the offset, you would do "movem.l (a7),d0/d1" to get the parameters. Play a bit around in a debugger, call a subroutine and watch the stack, then you should understand what's going on.

[BippyM]

how big is the amiga stack when not defined?

[BippyM]

Ok nobody answered so I'm gonna take a stab in the dark at 4096bytes, unless modified in the icon tooltypes or using the stack command

I guess this game uses amigaos quite a bit. where is the stack located?

[BippyM]

if the program dos the following

START
    JMP ADDY1

    <code>

ADDY1    move.l sp,address

    <code>

    move.l address,sp

    RTS

Now from the start of the program what exactly does the SP contain because it is saved and then used later!

[Toni Wilen]

Originally Posted by bippym

Ok nobody answered so I'm gonna take a stab in the dark at 4096bytes, unless modified in the icon tooltypes or using the stack command

Default is 4096, very small.. Always set bigger stack or you will have problems with many programs.

I guess this game uses amigaos quite a bit. where is the stack located?

Stack is per process/task and is dynamically allocated when process/task is created. Stack start and end pointers are located in Task structure if you really want to know but it is not normally needed.

[StingRay]

Originally Posted by bippym

if the program dos the following

START
    JMP ADDY1

    <code>

ADDY1    move.l sp,address

    <code>

    move.l address,sp

    RTS

Now from the start of the program what exactly does the SP contain because it is saved and then used later!

This is probably just to save the current stack pointer and restore it later when the program ends. E.g.

START   lea     InitialStack(pc),a0
        move.l  a7,(a0)                 ; store sp
        bsr     alotofthings
        ....
        
END     move.l  InitialStack(pc),a7     ; restore sp
        ...                             ; some other cleanup stuff
        rts

I do something like this in my demosystem f.e.

[BippyM]

The game uses a lot of LINK etc and the game accesses the register that is linked alot and I need to follow what it is doing

Anyway have the following code, which loads the system prefs, then modifies I think and saves them back.

lbC0040AA    LINK.W    A5,#-4
    MOVEM.L    D2/D3/A6,-(SP)
    PEA    ($E8).W
    PEA    (_PrefBuffer).L
    JSR    (_GetPrefs).L
    ADDQ.W    #8,SP
    PEA    ($E8).W
    PEA    (_PrefBuffer2).L
    JSR    (_GetPrefs).L
    ADDQ.W    #8,SP
    CLR.L    (-4,A5)
lbC0040DA     MOVE.L    (-4,A5),D0
    ASL.L    #1,D0
    LEA    (lbL024E98).L,A0
    CLR.W    (A0,D0.L)
    ADDQ.L    #1,(-4,A5)
    CMPI.L    #$24,(-4,A5)
    BLT.B    lbC0040DA
    CLR.L    -(SP)
    PEA    ($E8).W
    PEA    (_PrefBuffer2).L
    JSR    (lbC009AD4).L
    LEA    (12,SP),SP
    MOVEM.L    (SP)+,D2/D3/A6
    UNLK    A5
    RTS

Now I have started inserting labels, and if you want to see the _GetPrefs routine let me know, all it does is put $e8 into d0 and points a0 to either prefbuffer or prefbuffer2 then executes _LVOGetPrefs

The lines i'm unsure of I have made bold. If you could tell me what is happening, andf why there is stuff like clr.l -4.a5 etc.. why is it doing the -4? what is a5 pointing to?

Thanks

[StingRay]

Don't be so impatient I just answered that question in a pm :P

[BippyM]

hehehe sorry thoght you was busy, and I have work in an hour

[StingRay]

I just had a meeting and thus couldn't reply immediately :P

[Hungry Horace]

any chance of seeing a copy of that reply for the sake of those of us who like to learn?

[StingRay]

Of course, no problem! Here's what I wrote to bippym:

A5 is the ptr to the local variables that is created using the LINK instruction at the beginning. As you can see, it's just a simple counter and the clr instruction is just to initialise the counter. In "normal" (i.e. not produced by a compiler) asm it could look like:

lbC0040DA
        MOVE.L  .counter(pc),D0
        ASL.L   #1,D0
        LEA     (lbL024E98).L,A0
        CLR.W   (A0,D0.L)
        ADDQ.L  #1,.counter
        CMPI.L  #$24,.counter
        BLT.B   lbC0040DA
        ...
.counter        dc.l 0

That should be a bit easier to understand I hope.

[Wepl]

this program is compiled using Aztec-C, if you are using ReSource you should 'run the .rcl file' CFuncs.rcl supplied with ReSource.
this will name most Compiler and clib stuff

PS: the usage of frestore is 68060 incompatible (workaround in the 68060.library) because the stackframe (size) has changed