Microsoft KB Archive/81894

= FIX: MASM Allows Alignments > Segment Alignment =

Article ID: 81894

Article Last Modified on 10/22/2003

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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 Q81894



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      &quot;Hello World!&quot;, 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 query words: 5.10 5.10a 6.00 buglist5.10 buglist5.10a fixlist6.00

Keywords: kbfix KB81894

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