FIX: DOSXNT DX1020 Error Using .WHILE and Processor Flag (97840)

The information in this article applies to:

Microsoft Macro Assembler (MASM) 6.1
Microsoft Macro Assembler (MASM) 6.1a
Microsoft Macro Assembler (MASM) 6.0, when used with:
- the operating system: OS/2

This article was previously published under Q97840

SYMPTOMS

Microsoft Macro Assembler (MASM) version 6.1, and 6.1a may generate a DOSXNT DX1020 general protection fault when using the .WHILE directive to test the state of a processor flag (SIGN?, ZERO?, CARRY?, PARITY?, or OVERFLOW?). The error occurs if the processor flag is tested by itself or is negated and tested. For example:

.WHILE SIGN?
.WHILE !SIGN?

MASM version 6.0 running under OS/2 version 1.21 may generate a trap 13 in the above situation.

RESOLUTION

To work around this problem, OR the desired processor flag with zero. For example:

.WHILE SIGN? || 0

This work around will also work with ZERO?, CARRY?, PARITY?, and OVERFLOW?.

STATUS

Microsoft has confirmed this to be a problem in MASM versions 6.0, 6.1, and 6.1a. This problem was corrected in MASM version 6.11.

MORE INFORMATION

The following sample code can be used to demonstrate the problem.

Sample Code

; Assemble options needed: none

.MODEL small
.STACK 4096

.DATA

.CODE
    .startup
    .WHILE SIGN?       ; generates DOSXNT general protection fault
        nop
    .ENDW
    .WHILE SIGN? || 0  ; avoids the protection fault
        nop
    .ENDW
    .exit 0
END

Modification Type:	Major	Last Reviewed:	10/22/2003
Keywords:	kbfix KB97840