FIX: Near Call Between Segments Within a Group May Fail

ID: Q74532

The information in this article applies to:

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

SYMPTOMS

The Microsoft Macro Assembler (MASM) version 6.0 may generate incorrect code when a near call is made to a procedure in another segment. When a call is made from an offset greater that 0FDh in the calling segment to a procedure declared in the same source file, the call is made to an incorrect offset.

RESOLUTION

To work around this problem, code the procedure in another module and declare it as external in the problem module.

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 program below illustrates this problem. It defines two segments that are defined in the same group. Calls are being made from different offsets in the file. All calls after offset 0FDh are made to incorrect addresses rather than being set up as relocatable calls.

The following is incorrect code generated for the procedure called Generic:


 00F8                           Generic proc    near
 00F8  E8 0000 R                        call    Simple
 00FB  E8 0000 R                        call    Simple
 00FE  E8 11B2                          call    Simple
 0101  E8 5200                          call    Simple
 0104  E8 11B2                          call    Simple
 0107  E8 11B2                          call    Simple
 010A  E8 0854                          call    Simple
 010D                           Generic endp

The correct code that should be generated would appear as follows:


 00F8                           Generic proc    near
 00F8  E8 0000 R                        call    Simple
 00FB  E8 0000 R                        call    Simple
 00FE  E8 0000 R                        call    Simple
 0101  E8 0000 R                        call    Simple
 0104  E8 0000 R                        call    Simple
 0107  E8 0000 R                        call    Simple
 010A  E8 0000 R                        call    Simple
 010D                           Generic endp

Sample Code


; Assemble options needed: none
;

CGroup  group   Init, Code

ASSUME CS:CGroup

Code    segment para public 'CODE'

Simple  proc    near
        ret
Simple  endp

Code    ends


Init    segment para public 'CODE'
        ORG     0F8h

Generic proc    near
        call    Simple
        call    Simple
        call    Simple
        call    Simple
        call    Simple
        call    Simple
        call    Simple
Generic endp

Init    ends

END

Additional query words: 6.00 buglist6.00 fixlist6.00a

Keywords :
Version : MS-DOS:6.0
Platform : MS-DOS
Issue type :