Microsoft KB Archive/59754

= FIX: A2006: Phase Error May Be Caused By Incorrect NOP =

Article ID: 59754

Article Last Modified on 10/16/2003

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APPLIES TO


 * Microsoft Macro Assembler 5.1 Standard Edition
 * Microsoft Macro Assembler 5.1a

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This article was previously published under Q59754



SYMPTOMS
Using the &quot;SEG&quot; directive in conjunction with forward reference to a procedure or a segment name will produce the error

A2006 : phase error between passes



CAUSE
The assembler incorrectly places a &quot;NOP&quot; instruction in the code generated during Pass 1. This NOP is not generated in Pass 2, so the assembler generates a phase error. This phase error will most often happen on the next instruction that is associated with a fixup.



STATUS
Microsoft has confirmed this to be a problem in MASM versions 5.1 and 5.10a. This problem was fixed in MASM version 6.0.



RESOLUTION
To work around this problem, introduce a NOP that is seen by the assembler only during the second pass.



MORE INFORMATION
The following code produces the errors. The errors do not occur when the ax register is used. They occur when the bx, cx, and dx registers are used. The workaround is shown in commented out lines.

Sample Code:
;Assemble options needed: none


 * filler         MACRO                     ;macro that codes a nop
 * if2                      ;in the second pass of the
 * nop                      ;assembler
 * endif
 * ENDM

_text          SEGMENT PARA PUBLIC 'CODE' ASSUME CS:_TEXT

MOV    cx, SEG proc1     ;error using cx, bx or dx                MOV     ax, SEG proc1     ;no error using ax                MOV     cx, SEG stackseg  ;error using cx, bx, or dx                MOV     ax, SEG stackseg  ;no error using ax
 * filler
 * filler

STACKSEG       SEGMENT PARA PUBLIC 'STACK' db 100 dup (?) STACKSEG       ENDS

proc1          PROC    FAR ret proc1          ENDP _text          ENDS END

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

Keywords: kbfix KB59754

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