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Q29735: FIX: LES Instruction Assembles Incorrectly

Article: Q29735
Product(s): Microsoft Macro Assembler
Version(s): 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 5.1, 5.1a 
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SYMPTOMS
========

The program example below demonstrates a problem with the LES instructions in
Microsoft Macro Assembler (MASM) versions 5.1 and 5.1a. The first LES
instruction (Parm1) assembles correctly, but the second instruction (Parm2)
generates the error message:

  error A2056: Immediate mode illegal

The only difference between the two instructions is the order of the arguments.
In earlier versions of MASM, they produced identical code.

CAUSE
=====

The problem is with the type operator and the way it handles registers inside
brackets ([]). The type operator makes things a constant on the left of the
expression.

Parm1 works because it handles registers inside brackets differently. "TYPE x"
turns bp into a constant; +10 then turns it back into an addressing mode.

However, in Parm2, bp+10 has been turned into an addressing mode, which is then
turned into a constant by "TYPE x". This difference is demonstrated in the
sample code below.

STATUS
======

Microsoft has confirmed this to be a problem in MASM versions 5.1 and 5.1a. This
problem was corrected in MASM version 6.0.

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

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

  ; Assemble options needed: none

  .MODEL   small

  x STRUC
  y DD ?
  x ENDS

  Parm1 EQU DWORD PTR [bp+TYPE x+10]
  Parm2 EQU DWORD PTR [bp+10+TYPE x]

  .CODE
  begin:
      les di,Parm1
      les di,Parm2

  END begin

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

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

=============================================================================

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