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Q79835: FIX: MASM 6.0 May Generate Wrong Listing for CMPXCHG

Article: Q79835
Product(s): Microsoft Macro Assembler
Version(s): 6.0,6.0a,6.0b,6.10,6.10a
Operating System(s): 
Keyword(s): 
Last Modified: 06-MAY-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Macro Assembler (MASM), versions 6.0, 6.0a, 6.0b, 6.10, 6.10a 
-------------------------------------------------------------------------------

SYMPTOMS
========

When using the Microsoft Macro Assembler (MASM) to generate a listing file for
an assembler source file that contains a CMPXCHG instruction, errors may occur
in that listing. A colon is appended to bytes of values 26h, 2Eh, 36h, and 3Eh
when they appear in an instruction. For example, the following are generated:

  0000  0F B0 26: 00 00              cmpxchg data1, ah
  0005  0F B0 2E: 00 00              cmpxchg data1, ch
  000A  0F B0 36: 00 00              cmpxchg data1, dh
  000F  0F B0 3E: 00 00              cmpxchg data1, bh

instead of the following:

  0000  0F B0 26 0000  R             cmpxchg data1, ah
  0005  0F B0 2E 0000  R             cmpxchg data1, ch
  000A  0F B0 36 0000  R             cmpxchg data1, dh
  000F  0F B0 3E 0000  R             cmpxchg data1, bh

In addition, the address of a memory location is not always shown; instead, a
series of disjoint zero bytes appear. For example, the following is generated:

  0014  0F B0 16 00 00               cmpxchg data2, dl

instead of the following:

  0014  0F B0 16 0100  R             cmpxchg data2, dl

Note that this also occurs in the first example. Finally, extra trailing bytes
may be placed in the listing file. For example, the following is generated:

  0019  67& 0F B1 94 73 00000200  R  cmpxchg data3[ebx+2*esi],dx
        00 00 00 09

instead of the following:

  0019  67& 0F B1 94 73 00000200  R  cmpxchg data3[ebx+2*esi],dx

STATUS
======

Microsoft has confirmed this to be a problem in MASM versions 6.0, 6.0a, 6.0b,
6.1, and 6.1a. This problem was corrected in MASM for MS-DOS version 6.11.

Sample Code
-----------

  ; Assemble options needed: /c /Fl

  .MODEL small
  .486
  .STACK 4096

  .DATA
  data1 DB 100h DUP ('x')
  data2 DB 100h DUP ('y')
  data3 DW 100h DUP (1)

  .CODE
  start:
       cmpxchg data1, ah
       cmpxchg data1, ch
       cmpxchg data1, dh
       cmpxchg data1, bh
       cmpxchg data2, dl
       cmpxchg data3[ebx+2*esi],dx
  END start

Additional query words: 6.00 6.00a 6.00b 6.10 6.10a buglist6.00a buglist6.00b buglist6.10 buglist6.10a fixlist6.11

======================================================================
Keywords          :  
Technology        : kbMASMsearch kbAudDeveloper kbMASM600 kbMASM600a kbMASM600b
Version           : :6.0,6.0a,6.0b,6.10,6.10a
Solution Type     : kbfix

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