FIX: MASM 6.0 Generates L1103 for Nested Structures

The information in this article applies to:

• Microsoft Macro Assembler for MS-DOS, version 6.0
• Microsoft Macro Assembler for OS/2, version 6.0

SYMPTOMS

The Microsoft Macro Assembler (MASM) version 6.0 may produce an invalid object file, generating the following error message at link time:

   fatal error L1103: attempt to access data outside segment bounds

RESOLUTION

A work around is to rearrange the order of the outer-most structure. The sample code below illustrates this.

STATUS

Microsoft has confirmed this to be a problem in MASM version 6.0. This problem was corrected in MASM version 6.0a.

MORE INFORMATION

The sample code below illustrates this problem. If the MASM switch /Fl is used to generate a listing file, it can be seen that the assembler generates an offset for "BAD" of 001E in the structure ST1. Because this structure is a copy of the previous structure (ST0), the offset for BAD in each structure should be the same, the correct offset is 0014. No assembler error or warning is generated, but when the .OBJ file is linked, the L1103 error is generated.

Note: In the file listing, an incorrect offset is generated, but in the symbol listing, a correct offset is displayed for both instances of BAD.

Sample Code

; Rearranging ST1 as indicated in the comments fixed the problem in ST1 ; for this sample code.

; Assemble options needed: none ; (use /Fl to generate listing file)

.MODEL small .STACK 4096

ST0 STRUCT

   UNION
      STRUCT
         A       BYTE 10 DUP ('A')
         UNION
            B    BYTE 10 DUP ('B')
            D    BYTE 10 DUP ('D')
         ENDS
      ENDS
      E          BYTE 10 DUP ('E')
   ENDS
   BAD    BYTE   (' ')

ST1  STRUCT                        ; ST1  STRUCT
   UNION                           ;    BAD    BYTE   (' ')
      E          BYTE 10 DUP ('E') ;    UNION
      STRUCT                       ;       E          BYTE 10 DUP ('E')
         A       BYTE 10 DUP ('A') ;       STRUCT
         UNION                     ;          A       BYTE 10 DUP ('A')
            B    BYTE 10 DUP ('B') ;          UNION
            D    BYTE 10 DUP ('D') ;             B    BYTE 10 DUP ('B')
         ENDS                      ;             D    BYTE 10 DUP ('D')
      ENDS                         ;          ENDS
   ENDS                            ;       ENDS
   BAD    BYTE   (' ')             ;    ENDS
ST1  ENDS                          ; ST1  ENDS

item1   ST0    <>
item2   ST1    <>

    .startup
    .exit 0