ID Number: Q81894
5.10 5.10a | 5.10 5.10a
MS-DOS | OS/2
buglist5.10 buglist5.10a fixlist6.00
Summary:
PROBLEM ID: MSM9203004
SYMPTOMS
The Microsoft Macro Assembler (MASM) versions 5.1 and 5.1a
incorrectly allow ALIGN directives that are greater than the
alignment of the segment they appear within. MASM 5.1 does not
generate errors for these statements; however, it cannot guarantee
that the item following these ALIGN directives will be aligned on
the given boundary.
RESOLUTION
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:
The maximum ALIGN value for data or code is the alignment used when
defining the segment. When a segment is declared, it is guaranteed to
start only at its specified alignment. Since the assembler can align
items relative only to the start of a segment, any ALIGN statement
greater than the segment's alignment should generate an error. If the
following sample code is assembled with MASM 5.1 or MASM 5.1a, no
error is generated. Padding is inserted after the ALIGN 4
directive, but it will not align the next statement on the indicated
boundary. MASM 6.0 correctly generates the following error:
A2189: invalid combination with segment alignment : 4
Valid segment alignments include: BYTE, WORD, DWORD, PARA, or PAGE.
PARA is the default.
Sample Code
-----------
; Assemble options needed: none
STACK SEGMENT PARA STACK 'STACK'
DB 100h DUP('x')
STACK ENDS
_DATA SEGMENT WORD PUBLIC 'DATA'
msg DB "Hello World!", 13, 10, '$'
_DATA ENDS
_TEXT1 SEGMENT WORD PUBLIC 'CODE'
ASSUME CS:_TEXT1
retrn: ret
_TEXT1 ENDS
_TEXT2 SEGMENT WORD PUBLIC 'CODE'
ASSUME CS:_TEXT2, DS:_DATA
start: mov ax, SEG msg
mov ds, ax
ALIGN 4
mov dx, OFFSET msg
mov ah, 09h
int 21h
mov ax, 4C00h
int 21h
_TEXT2 ENDS
END start
Additional reference words: 5.10 5.10a 6.00