Microsoft KB Archive/107500

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Knowledge Base

Article ID: 107500

Article Last Modified on 10/14/2003


  • Microsoft Macro Assembler 6.0 Standard Edition
  • Microsoft Macro Assembler 6.0a
  • Microsoft Macro Assembler 6.0b
  • Microsoft Macro Assembler 6.1 Standard Edition
  • Microsoft Macro Assembler 6.1a
  • Microsoft Macro Assembler 6.11 Standard Edition

This article was previously published under Q107500


When you attempt to assemble the sample code below, the Microsoft Macro Assembler (MASM) fails and reports the following error for the two lines with "mov" instructions:

error A2006: undefined symbol


To work around the problem, do one of the following,

  • Simplify the expression. If you uncomment the lines in the sample code, and delete the original instructions, the code will assemble without errors. -or-
  • Assemble with the /Zm option (or run MASM.EXE instead of ML.EXE). -or-

  • Use the OPTION OLDSTRUCTS directive to have the assembler treat structure members the same as in MASM 5.1.


Microsoft has confirmed this to be a problem in MASM versions 6.0x, 6.1, 6.1a, and 6.11. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

Sample Code

; Assemble options needed: none

        .MODEL  small

  f1    BYTE    ?
  f2    BYTE    ?

        mov     al, SIZEOF STEST.f1 + SIZEOF STEST.f2
        mov     al, LENGTHOF STEST.f1 + LENGTHOF STEST.f2
; Uncomment the lines below and delete the two lines above to avoid
; the A2006 error
;       temp = SIZEOF STEST.f1
;       mov    al, temp + SIZEOF STEST.f2
;       temp = LENGTHOF STEST.f1
;       mov    al, temp + LENGTHOF STEST.f2


Additional query words: buglist6.00 buglist6.00a 6.00 6.00a 6.00b 6.10 6.10a 6.11 buglist6.00b buglist6.10 buglist6.10a buglist6.11

Keywords: KB107500