FIX: MOV with Type Operator Generates Incorrect Opcodes (30385)


The information in this article applies to:

  • Microsoft Macro Assembler (MASM) 5.1
  • Microsoft Macro Assembler (MASM) 5.1a
This article was previously published under Q30385

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
Modification Type:MajorLast Reviewed:10/22/2003
Keywords:kbfix KB30385
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