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Phosque



Joined: 20 May 2007
Posts: 2
Location: Sweden
Phosque
Hi!

I'm new around here, hopefully I'll stay Smile I'm trying to create a DLL in FASM, exporting basic VGA functions. It compiles just fine, but when I run it from another programming language it doesn't work. Any help is greatly appreciated.

Code:
format PE GUI 4.0 DLL
entry DllEntryPoint

include '%fasminc%\win32a.inc'

section '.code' code readable executable

proc DllEntryPoint hinstDLL,fdwReason,lpvReserved
        mov eax,TRUE
        ret
endp

proc OpenScreen
    org 100h    ; DOS
    mov al, 13h ; VGA 320x200
    int 10h     ;
endp

proc SetPixel
     mov ax,0a000h
     mov ds,ax

     mov si,120    ; Position
     mov al,1      ; Color
     mov [si],al   ; Draw in vid mem
endp

section '.edata' export data readable

  export 'gfxlib.dll',\
         OpenScreen, 'OpenScreen'

section '.reloc' fixups data discardable
    


(Yes, I just modified the DLL example that came with FASM)

Thanks,
Martin
Post 20 May 2007, 17:22
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LocoDelAssembly
Your code has a bug


Joined: 06 May 2005
Posts: 4633
Location: Argentina
LocoDelAssembly
Code:
proc OpenScreen 
    org 100h    ; DOS 
    mov al, 13h ; VGA 320x200 
    int 10h     ; 
endp     


As you said, it's for DOS and will not work under Windows. You have to use DirectDraw instead. Also note that "org 100h" is not a kind of DOS tag, it only sets the origin, something that could lead some problems when you write a DLL.
Post 20 May 2007, 17:39
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Phosque



Joined: 20 May 2007
Posts: 2
Location: Sweden
Phosque
Alright, thanks for the reply, LocoDelAssembly.
Post 20 May 2007, 18:05
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Hayden



Joined: 06 Oct 2005
Posts: 132
Hayden
to make things more clear for other readers, interrupt calls cannot be used in a window *.dll

_________________
New User.. Hayden McKay.
Post 21 May 2007, 03:46
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LocoDelAssembly
Your code has a bug


Joined: 06 May 2005
Posts: 4633
Location: Argentina
LocoDelAssembly
Although it's undocumented you can do it even on NT/2000/XP, look at NTDLL.DLL disassembly on machines with no SYSENTER/SYSCALL support. On http://www.ctyme.com/intr/cat-049.htm you can see interrupt services for non-NT Windowses.

What you can't do is calling BIOS** and DOS** interrupts from Windows.

**On Win9x I'm almost sure that I saw it on 16-bit or 32-bit Windows executables but Int $10 wasn't one of them.
Post 21 May 2007, 13:01
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