BUG: A2154 If Structure Member in Control-Flow Directive

• Microsoft Macro Assembler for MS-DOS, versions 6.0, 6.0a, 6.0b, 6.1, 6.1a, and 6.11
• Microsoft Macro Assembler for OS/2, versions 6.0, 6.0a, and 6.0b

SYMPTOMS

The Microsoft Macro Assembler (MASM) versions 6.0 and later provide several Control-Flow directives such as the .WHILE, .REPEAT, and .IF constructs. When structure members are accessed inside of these constructs, MASM may incorrectly generate the following error:

   error A2154: syntax error on control-flow directive

RESOLUTION

The sample program below illustrates this problem. As a workaround, a register or a temporary variable may be used to hold the structure member, as demonstrated below in Sample Code 2.

STATUS

Microsoft has confirmed this to be a problem in MASM versions 6.0, 6.0a, 6.0b, 6.1, 6.1a, and 6.11. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

Sample Code 1

.MODEL small, C

STRUCT1 STRUCT SMember SWORD 0 STRUCT1 ENDS

.STACK 4096

.DATA var1 STRUCT1 <0>

.CODE

   .startup
   mov bx, OFFSET var1

   .WHILE ((STRUCT1 PTR [bx]).SMember != 1000)
   inc (STRUCT1 PTR [bx]).SMember
   .ENDW

   .REPEAT
   dec (STRUCT1 PTR [bx]).SMember
   .UNTIL ((STRUCT1 PTR [bx]).SMember == 0)

   .IF ((STRUCT1 PTR [bx]).SMember == 0)
   nop
   .ENDIF

   .exit 0

Sample Code 2

.MODEL small, C

STRUCT1 STRUCT SMember SWORD 0 STRUCT1 ENDS

.STACK 4096

.DATA var1 STRUCT1 <0>

.CODE

   .statup
   mov bx, OFFSET var1.SMember

   .WHILE (SWORD PTR [bx] != 1000)
   inc SWORD PTR [bx]
   .ENDW

   .REPEAT
   dec SWORD PTR [bx]
   .UNTIL (SWORD PTR [bx] == 0)

   .IF (SWORD PTR [bx] == 0)
   nop
   .ENDIF

   .exit 0