Microsoft KB Archive/35128

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Knowledge Base

Article ID: 35128

Article Last Modified on 11/19/2003


  • Microsoft Macro Assembler 5.1 Standard Edition
  • Microsoft Macro Assembler 5.1a
  • Microsoft Macro Assembler 6.0 Standard Edition
  • Microsoft Macro Assembler 6.0a
  • Microsoft Macro Assembler 6.0b

This article was previously published under Q35128


The example below will generate the warning:

warning A4016: Reserved word used as symbol: MOV

when assembled with Microsoft Macro Assembler (MASM) 5.1 and 5.1a. This warning is misleading. MASM 6.0, 6.0a, and 6.0b generate the more specific error message:

error A2001: immediate operand not allowed


The reference to a_struc.a in the example below is a reference to a structure template and not to a variable stored in memory. Thus, a_struc.a is a constant or immediate operand. MASM 5.1 and 5.1a always looks up the second token on the line first. In the case below, it sees "a_struc". Because a_struc is a structure declaration, MASM assumes the line declares a structure instance with "MOV" being the label. At this point, MASM errors on trying to use reserved symbol "MOV" as a structure instance label.


This is the expected behavior of MASM.


Sample Code

; Assemble options needed: none

a_struc STRUC
    a DW ?
a_struc ENDS

    mov a_struc.a, ax
    mov ax, 4C00h
    int 21h

END start

Additional query words: 5.10 5.10a 6.00 6.00a 6.00b

Keywords: KB35128