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Q59754: MASM Err Msg: A2006: Phase Error Forward Referencing... |
/pubs/pc/reference/microsoft/kb/Q59754/ |
Article: Q59754
Version(s): 5.10 5.10a | 5.10 5.10a
Operating System: MS-DOS | OS/2
Flags: ENDUSER | buglist5.10
Last Modified: 12-JUL-1990
Using the "SEG" directive in conjunction with forward reference to a
procedure or a segment name will produce the error "A2006 : phase
error between passes."
The assembler incorrectly places a "NOP" 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 most often will be
against the first subsequent instruction that is associated with a
fixup (an instruction that contains any address, such as a JMP
<label>, CALL <label>, or MOV <reg>,<label>).
Microsoft has confirmed this to be a problem in the Microsoft Macro
Assembler Version 5.10. We are researching this problem and will post
new information here as it becomes available.
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.
_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
STACKSEG SEGMENT PARA PUBLIC 'STACK'
DB 100 DUP (?)
STACKSEG ENDS
PROC1 PROC FAR
nop
PROC1 ENDP
_TEXT ENDS
END
To work around this problem, introduce a NOP that is seen by the
assembler only during the second pass. The following code assembles
without an error:
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
filler
mov cx, SEG STACKSEG
filler
STACKSEG SEGMENT PARA PUBLIC 'STACK'
DB 100 DUP (?)
STACKSEG ENDS
PROC1 PROC FAR
nop
PROC1 ENDP
_TEXT ENDS
END