BUG: Ml.exe Hangs If ASSUME DataReg:ERROR Directive Used

• Microsoft Macro Assembler for Windows NT, version 6.11

SYMPTOMS

Using the MASM ASSUME DataReg:ERROR directive, where DataReg is one of the general purpose data registers (ax, bx, cx, or dx) and then using indirect addressing on the same register, causes Ml.exe to hang (stop responding).

The problem can be demonstrated by Assembling the code sample given in this article. The ASSUME DatReg:ERROR directive would normally cause the assembler to emit an error when the data register is used. By changing the first line of code in the sample code to a comment, you can see the error message output by the assembler; that line does indirect addressing with bx (mov ax,[bx]).

RESOLUTION

The only resolution at this time is to not use the ASSUME reg:ERROR directive in a program that does indirect addressing using one of the general purpose data registers.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

Sample Code to Reproduce Problem

;Compile options needed: NONE

.MODEL SMALL

   ASSUME bx:ERROR

   mov ax,[bx]
   mov ax,bx    ;Change the proceeding line to a comment and this line will
                ;generate expected error
END