Q26822: FIX: Relational Operators Evaluate to Wrong Value

Article: Q26822
Product(s): Microsoft Macro Assembler
Version(s): 5.0,5.1,5.1a
Operating System(s): 
Keyword(s): 
Last Modified: 06-MAY-2001

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The information in this article applies to:

- Microsoft Macro Assembler (MASM), versions 5.0, 5.1, 5.1a 
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SYMPTOMS
========

When used with a MOV instruction, some relational operators will evaluate to the
wrong value. The following listing file sections are examples of this problem.
It is important to note that FFFF = true, and 0000 = false. It is also important
to note that when FFFFh is used with the GT, GE, or LT, LE operator, it is
interpreted as the largest positive number and not as -1.

STATUS
======

Microsoft has confirmed this to be a problem in Microsoft Macro Assembler (MASM)
version 5.0, 5.1, and 5.1a. This problem was corrected in MASM version 6.0.

MORE INFORMATION
================

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

The following demonstrates this problem with MASM 5.0:

                .MODEL SMALL
         0000   .CODE
         0000   B8 0000    MOV AX, 0FFFFH GT -1
         0003   B8 FFFF    MOV AX, 0FFFFH LE -1
         0006

                .386
                .MODEL SMALL
         0000   .CODE
         0000   66 | B8 FFFF   MOV AX, -1 GE 0FFFFFFFFH
         0004   66 | B8 FFFF   MOV AX, 0FFFFFFFFH LE -1
         0008   66 | B8 0000   MOV AX, 0FFFFFFFFH GT -1
         000C   66 | B8 0000   MOV AX, -1 LT 0FFFFFFFFH
         0010   END

The following demonstrates the problem MASM 5.1:

                .MODEL SMALL
         0000   .CODE
         0000   B8 0000    MOV AX, 0FFFFH GT -1
         0003   B8 FFFF    MOV AX, 0FFFFH LE -1
         0006

                .386
                .MODEL SMALL
         0000   .CODE
         0000   66 | B8 FFFF   MOV AX, -1 GE 0FFFFFFFFH
         0004   66 | B8 0000   MOV AX, 0FFFFFFFFH LE -1
         0008   66 | B8 FFFF   MOV AX, 0FFFFFFFFH GT -1
         000C   66 | B8 0000   MOV AX, -1 LT 0FFFFFFFFH
         0010   END

Additional query words: 5.00 5.10 5.10a buglist5.00 buglist5.10 fixlist6.00

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Keywords          :  
Technology        : kbMASMsearch kbAudDeveloper kbMASM510 kbMASM500 kbMASM510a
Version           : :5.0,5.1,5.1a
Solution Type     : kbfix

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