Conditionally Assembling the END Directive

• Microsoft Macro Assembler for MS-DOS, versions 5.x, 6.0, 6.0a, and 6.0b
• Microsoft Macro Assembler for OS/2, versions 5.x, 6.0, 6.0a, and 6.0b

Sometimes it is helpful to conditionally have a starting label specified with the END directive; for example, to use preprocessor directives to specify various END directives:

IFDEF xyz

  END start_label

  END

Note, however, that this approach will not work. As soon as MASM encounters the first END directive it will stop assembling. The assembler stops regardless of whether or not the END directive is inside a preprocessor block. This is the expected behavior for the assembler.

A method that can be used to accomplish this task involves using a conditionally defined text equate with the END directive. The following sample code demonstrates this method:

Sample Code

; Assemble options needed: /Dxyz

.MODEL small

.STACK 4096

.CODE start_label:

  mov ax, 4C00h
  int 21h

  end_label EQU <start_label>

  end_label EQU <>

END end_label