Q40784

layout	title	permalink
page	Q40784: CodeView Does Not Work with Grouped Code Segments	/pubs/pc/reference/microsoft/kb/Q40784/

Q40784: CodeView Does Not Work with Grouped Code Segments

Article: Q40784
Version(s): 2.20   | 2.20
Operating System: MS-DOS | OS/2
Flags: ENDUSER | H_MASM
Last Modified: 9-FEB-1989

When using MASM it is possible to associate various segments into a
group; DGROUP is an example of this technique. Grouped data or stack
segments do not affect CodeView, but CodeView does not recognize
grouped code segments. The program will execute correctly under
CodeView, but none of the CodeView functions will be available on the
second and subsequent segments in the code group.

The following code segment illustrates this behavior:

codegroup  GROUP ASEG,BSEG
        assume cs:codegroup

ASEG    SEGMENT WORD PUBLIC 'CODE'
A:
        mov ax,1
        mov ax,1
        JMP B
ASEG    ends

;   Will not be able to single step through this section
BSEG    SEGMENT WORD PUBLIC 'CODE'
B:      mov ax,1
        mov ax,1
        mov ax,1
        int 21h
BSEG    ends
        end A

Once the program executes into the BSEG segment, all CodeView
functionality will be lost. You cannot set any breakpoints or single
step through the BSEG segment of code. It appears that CodeView does
not store any symbolic information for the BSEG segment. Any attempt
to single step through this section of code will result in CodeView
executing the BSEG segment of code until the program is completed.

Microsoft is researching this problem and will post new information as
it becomes available.