3 replies to this topic

[jorants]

Hello,

I have the following code: (simplefied)

Main:
 mov si,WORD[.Adr]
 call si
 cli
 hlt

.Adr: dw TTT

TTT:
 --DO SOMETHING---
 ret

But the function never gets used, if i call TTT direct i does work:

Main:
 call TTT
 cli
 hlt

Also, comparing SI with TTT show the are the same.
I'm i missing something when it comes to function pointers?

i'm using NASM in 16bit binairy mode (bootloader)

Tanx,

Joran

[jorants]

If anyone wants to know, i have found a workaround.
The problem was that only 32 bit registers where allowed with jumps.
however, 16bit reletive jumps are alowed, when the distance to jump is already known:

    mov si,WORD[.adr]             ;Load absolute adress
    sub si,.After                      ;Calc relative
    mov WORD[.JumpLoc],si      ;Alter Jump code     
    db 0xE9                            ;Opcode for 16bit relative JUMPS
    .JumpLoc: db 0,0               ;Bytes to jump
    .After:

I hope it can help anyone.

[dargueta]

Try mov si, TTT

[jorants]

That didn't work.
Also, cmp si,TTT and than Jump if Equeal showed that TTT was in SI.