FIX: MOV with Type Operator Generates Incorrect Opcodes

 Last reviewed: September 11, 1997
Article ID: Q30385
5.10 5.10a MS-DOS kbtool kbfixlist kbbuglist

The information in this article applies to:

  • Microsoft Macro Assembler for MS-DOS, versions 5.1 and 5.1a

SYMPTOMS

The MOV instruction, using indirect addressing, and the Type operator generate incorrect opcodes.

STATUS

Microsoft has confirmed this to be a problem in Microsoft Macro Assembler versions 5.1 and 5.1a. This problem was corrected in MASM version 6.0.

MORE INFORMATION

The first MOV instruction generates the opcode "B8FFF4", which is a move-immediate instruction. The assembler should generate the opcode "8B44F4". This opcode is generated on the second move instruction. MASM Version 5.00 generates the correct code for both MOV instructions.

The following code demonstrates the problem:

seg_1 segment para public 'code' 

       assume cs:seg_1
test_str struc test_f1 dw ? test_f2 dw ? test_f3 db 8 dup (?) test_str ends main_entry proc 
       mov  ax,word ptr [si] - type test_str
; ; This alternate generation works ; 
       mov  ax,word ptr [ si - type test_str]
main_entry endp seg_1 ends 
       end

Additional reference words: 5.10 5.10a buglist5.10 buglist5.10a fixlist6.00
KBCategory: kbtool kbfixlist kbbuglist
KBSubCategory: MLIss
Solution Type : kbfix

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Last reviewed: September 11, 1997
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