FIX: MASM Moves Segment Register w/out Generating Error

 Last reviewed: September 16, 1997
Article ID: Q83087
6.00 6.00a 6.00b 6.10 6.10a | 6.00 6.00a 6.00b 
MS-DOS                      | OS/2
kbprg kbfixlist kbbuglist

The information in this article applies to:

  • Microsoft Macro Assembler for MS-DOS, versions 6.0, 6.0a, 6.0b, 6.1, and 6.1a
  • Microsoft Macro Assembler for OS/2, versions 6.0, 6.0a, and 6.0b

SYMPTOMS

Microsoft Macro Assembler (MASM) may move a segment register instead of generating an error on an invalid code statement. In the following example, the statement: 

   mov bx, es[1234h]
should generate an error. However, MASM treats the statement as: 

   mov bx, es
and thus does not generate the code that may be expected. The code that the user anticipated being generated was: 

   mov bx, es:[1234h]

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.

MORE INFORMATION

The following program should generate two assembler errors but does not:

Sample Code

; Assemble options needed: none

.MODEL small .386 .STACK 4096

.CODE start: 

   mov bx,es[1234h]     ; This should generate an error.
   mov es[1234h],bx     ; This should generate an error.
   mov ax, 4C00h
   int 21h
END start

Additional reference words: 6.00 6.00a 6.00b 6.10 6.10a buglist6.00a
buglist6.00b buglist6.10 buglist6.10a fixlist6.11
KBCategory: kbprg kbfixlist kbbuglist
KBSubCategory: MLIss
Solution Type : kbfix

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Last reviewed: September 16, 1997
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