FIX: ORG Calculated from Label May Fail in 6.0a/6.0b

MS-DOS      | OS/2

The information in this article applies to:

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

SYMPTOMS

In Microsoft Macro Assembler (MASM) versions 6.0a and 6.0b, if the expression for an ORG directive is calculated from a label, the ORG directive will not give the correct results. The origin set by the ORG directive will be off by the value of the current location counter ($) prior to the ORG directive.

RESOLUTION

The sample code below demonstrates a macro that can be used to correct the behavior of ORG. This macro should be used only if the expression being supplied to ORG was calculated using a label. If the expression being supplied to ORG was not calculated using any labels, the ORG directive should work correctly.

This macro works correctly only under MASM versions 6.0a and 6.0b.

STATUS

Microsoft has confirmed this to be a problem in MASM versions 6.0a, and 6.0b. This problem was corrected in MASM for MS-DOS version 6.1.

MORE INFORMATION

Sample Code

; Assemble options needed: none

ORGFIX MACRO arg1             ; This macro can be used
   ORG (arg1- ($- @CurSeg))   ; whenever the origin you are
ENDM                          ; trying to set contains a LABEL
                              ; or $ as part of the expression.

.CODE start LABEL BYTE

   .startup
   .exit 0

ORG ((finish- start)+ 10h)    ; This will incorrectly set
tst1 LABEL BYTE               ; the origin.

tst2 LABEL BYTE               ; the origin.

   DB 'hello'