.title   iferr
;     this function returns the value of the
;     first argument.
;     If this is an error then the appropriate error message
;     text is output, the user-supplied string is output,
;     and the image exits.
;
;     USAGE:
;     J = IFERR(SYS$SETEF(%VAL(FTHEM)),'RJEMASTER UNABLE TO SETEF')
;
iferr::  .word ^m<r2>
      movl  @4(ap),r0
      blbc  r0,doit
      ret
doit:
      clrl     -(sp)
      pushl    r0
      pushl    #1
      moval    (sp),r2
      movq     @8(ap),desc
      $putmsg_s   msgvec=(r2),actrtn=ifexit
      $exit_s  code=@4(ap)
desc:   .quad    0
ifexit:  .word 0
      movq     desc,@4(ap)
      ret
      .end