QB64 x86 Error, Unknown Opcode (92)

[EricE]

I am using the ABSOLUTE function to execute machine code that has been placed in an array.

QB64 is reporting this runtime error:
x86 Error, Unknown Opcode (92)

Opcode 92 is one of the instructions in my machine code array.
The mnemonic for this opcode is:

XCHG    DX,AX

Why would QB64 report that the opcode for this instruction is unknown?

[luke]

Because the x86 emulation is really half-assed, and basically has had just enough work done on it to allow some standard mouse routines from the QB era to work.

[EricE]

Thank you Luke.
I will try to find a work around.

[FellippeHeitor]

Yeah, no low level in the basic side. You’d need to dive into c for that.

What did you intend to do with machine code?

[EricE]

The opcode 92 is contained in the source code for the QBWrite text editor, version 2.7.

This can be obtained by downloading the file obw.zip from this page:

https://qb45.org/files.php?cat=10&p=8

[FellippeHeitor]

But what’s the machine code call supposed to do? Maybe qb64 already does it without the low level call.

[EricE]

Here is the qbwrite 2.7 source code that contains not only the 92 opcode, but the 91 and 93 opcodes as well.
The opcodes used are part of the program's mouse routine.

Code: QB64: [Select]

1. DEFINT A-Z
2. DIM SHARED a(9)
3. DEF SEG = VARSEG(a(0))
4. FOR i = 0 TO 17
5.     READ r
6.     POKE VARPTR(a(0)) + i, r
7. NEXT i
8. '---------------------------- Machine Code -----------------------------------
9. DATA &HB8,&H00,&H00:
10. DATA &H55:
11. DATA &H8B,&HEC:
12. DATA &HCD,&H33:
13. DATA &H92:
14. DATA &H8B,&H5E,&H06:
15. DATA &H89,&H07:
16. DATA &H5D:
17. DATA &HCA,&H02,&H00:
18. '-------------------------------------------------------------------------------
19.  
20. SUB Mouse (cx, dx, bx)
21.        
22.     POKE VARPTR(a(4)), &H92 'Swap code,Get CX setup
23.     CALL ABSOLUTE(cx, VARPTR(a(0))) 'Run Code
24.     cx = (cx / 8) + 1 'Adjust 25x80
25.     POKE VARPTR(a(4)), &H91 'Swap code,Get DX setup
26.     CALL ABSOLUTE(dx, VARPTR(a(0))) 'Run Code
27.     dx = (dx / 8) + 1 'Adjust 25x80
28.     POKE VARPTR(a(4)), &H93 'Swap code,Get BX setup
29.     CALL ABSOLUTE(bx, VARPTR(a(0))) 'Run Code
30.  
31. END SUB
32.  
33. SUB MousePointer (SW)
34.        
35.     POKE VARPTR(a(0)) + 1, SW 'Swap code,Set AX = (SW)
36.     CALL ABSOLUTE(c, VARPTR(a(0))) 'Run Code
37.  
38. END SUB
39.  

[FellippeHeitor]

Adapt your code to use the new mouse features. http://www.qb64.org/wiki/Keyword_Reference_-_By_usage#Mouse_Input:

All functions are prefixed with _MOUSE.

[EricE]

Here are the subroutines using QB64's mouse features.

Code: QB64: [Select]

1. SUB Mouse (cx, dx, bx)
2.  
3.     mi = _MOUSEINPUT
4.     cx = _MOUSEY ' Qbwrite's horizontal column number
5.     dx = _MOUSEX ' Qbwrite's vertical row number
6.  
7.     bx = 0
8.     IF _MOUSEBUTTON(1) THEN bx = bx OR &H1 ' Left mouse button
9.     IF _MOUSEBUTTON(2) THEN bx = bx OR &H2 ' Right mouse button
10.     IF _MOUSEBUTTON(3) THEN bx = bx OR &H4 ' Center or scroll button
11.  
12.  
13. END SUB
14.  
15. SUB MousePointer (SW)
16.  
17.     WHILE _MOUSEINPUT: WEND
18.  
19.     SELECT CASE SW
20.         CASE 0 ' Initialize mouse
21.             ' In QB64 nothing to do
22.         CASE 1 ' Show mouse cursor
23.             _MOUSESHOW
24.         CASE 2 ' Hide mouse cursor
25.             _MOUSEHIDE
26.         CASE 3 ' Get mouse position
27.             ' Done in Mouse subroutine
28.     END SELECT
29. END SUB

[EricE]

Waiting for the _MOUSEINPUT function to return zero

Code: QB64: [Select]

1. WHILE _MOUSEINPUT: WEND

might not be required in the above code.

[EricE]

The mouse machine code is explained in detail in this file:
qmouse.zip by Robert Wolf
which is available for download from the web page:
https://qb45.org/files.php?cat=10&p=8

This is only to understand the operation of the original code, as it will not run in QB64 due to some opcodes not being emulated.