From:	Joseph Rose <jorose AT mail DOT gis DOT net>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: 3rd Try: Maybe an asm problem? (Problems linking)
Date:	Fri, 28 Apr 2000 17:21:51 -0400
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Steamer wrote:

> Joseph Rose wrote:
>
> >I have described what the asm source code looks like.
>
> Only very vaguely.  My NASM files look like that too, but they work.
> How have you declared the segments?
>

SECTION .text

All data and stack as of yet are given by the calling routine, so there
is no data section.

>
> >If you need more, I can publish a function in question and
> >the beginning of the file.
>
> Go on then.
>

It's at the end of the post.

>
> Looking at your other post, however, your problem may be elsewhere.
> The prototypes for your asm functions need to be wrapped in
> extern "C" {} if you're using C++, unless you've taken name-mangling
> into account in your asm file.
>

I'll try that.  If name-mangling is more than "_" at the beginning of
the name, then I don't know about it.

>
> S.

                     .          == -|-=-
     |\_/|           ;         ----/ -= -
    / .-=|          \[/        - -=|-\=--=
   | ..-==\      --==+==--     --=-|=|- -=
  /  .---==\        /[\        =- /==-==-
 /  ..---===\        ;          =-|- -\--
 --__----__---       .            | - |
     ````            `           /    \

--------------
VGADr386.asm:
.
.
.
BITS 32

COMMON VidBuffer 6
SECTION .text
;SEGMENT VGA8_2D FLAT PUBLIC 'GRAPHICS'
GLOBAL _ClrScn, _Screen_Copy
GLOBAL _Draw_Pixel, _Read_Pixel
GLOBAL _Draw_Line_Horiz, _Draw_Line_Vert, _Draw_Line
GLOBAL Draw_Line_Horiz
GLOBAL _Draw_Box, _Draw_Tri
GLOBAL _Draw_Image, _Font_Print
;EXPORT _Draw_Line_Horiz
%INCLUDE "c:\zzz\gr\386p\VGADR386.MAC"

.
.
.

%IFDEF Line2
;Draws a horizontal line from left to right.
_Draw_Line_Horiz: ;PROC NEAR
;Draw_Line_Horiz: ; PROC
;InitX=D[EBP+16]
;InitY=D[EBP+12]
;Len=W[EBP+10]
;Col=W[EBP+8]
 PUSH EBP  ;Set up to read stack.
 MOV EBP,ESP
 PUSH DS
 MOVZX ECX,WORD [SS:EBP+10] ;Load length of line.
 JECXZ .Exit ;No length?  Exit.
;Error Check:
%IFDEF OffScreen
 CMP DWORD [SS:EBP+12],200 ;Is line outside screen limits?
 JAE .Exit ;  Yes--Exit.
 MOVSX EBX,WORD [SS:EBP+16] ;Load InitX into BX reg. for testing.
 CMP EBX,320 ;Off the right side of the screen?--Exit.
 JGE .Exit
 TEST EBX,EBX ;Negative?
 JNS .ChkX2
 ADD ECX,EBX ;If so, decrease length by -InitX to counteract
   ;  screen overflow,
 JS .Exit ;  (Exit if line's to the left of the screen)
 XOR EBX,EBX ;  and make InitX = 0.
 MOV DWORD [SS:EBP+16],EBX
.ChkX2: ADD EBX,ECX ;Will line be drawn off the right screen border?
 SUB EBX,320
 JS .ChkXF
 SUB ECX,EBX ;If so, truncate the overflow.
.ChkXF:
%ENDIF
;Draw Line:
 LDS EDI,[CS:VidBuffer] ;Load memory pointer to video buffer.


;Calculate starting pos.
 CalcPixelLoc EDI,EAX,DWORD [SS:EBP+16],DWORD [SS:EBP+10]
 MOV AL,BYTE [SS:EBP+6] ;Load color twice (for hi byte and low byte) for

 MOV AH,AL ;  faster writing in Dword increments.
 MOV BX,AX
 SHL EAX,16
 MOV AX,BX
 CALL _Draw_Line_HorizHere
.Exit: POP DS
 POP EBP  ;Exit.
 RET
;ENDP

%ENDIF

%IFDEF Line2
;Draws a horizontal line of color AX and length CX starting at pixel at
;DS:DI.  The caller is responsible for error-checking.
_Draw_Line_HorizHere: ; PROC
 JCXZ .Exit
 SHR ECX,1
 JNC .W
 MOV [DS:EDI],AL
 INC EDI
 JCXZ .Exit
.W:
 SHR ECX,1
 JNC .D
 MOV [DS:EDI],AX
 ADD EDI,2
.D:
 MOV [DS:EDI],EAX
 ADD EDI,4
 DEC ECX
 JNZ .D
.Exit:
 RET
%ENDIF

.
.
.

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