leaving the region highlighted after a command

[Jonathan Swartz]

I use transient-mark-mode. I'm trying to write a command like mark- 
whole-buffer that selects a certain region and leaves it highlighted.  
But I cannot seem to get this to work; at the end of my command, the  
region is never highlighted.

Here's the definition of mark-whole-buffer in simple.el:

   (defun mark-whole-buffer ()
     "Put point at beginning and mark at end of buffer.
   You probably should not use this function in Lisp programs;
   it is usually a mistake for a Lisp function to use any subroutine
   that uses or sets the mark."
     (interactive)
     (push-mark (point))
     (push-mark (point-max) nil t)
     (goto-char (point-min)))

This leaves the region highlighted. But if I simply call mark-whole- 
buffer from another function or copy its code verbatim to another  
function, the new other functions do NOT leave the region highlighted:

   ;; No highlighting
   (defun mb ()
     (interactive)
     (mark-whole-buffer))

   ;; Yup, still no highlighting
   (defun mb2 ()
     "Put point at beginning and mark at end of buffer.
   You probably should not use this function in Lisp programs;
   it is usually a mistake for a Lisp function to use any subroutine
   that uses or sets the mark."
     (interactive)
     (push-mark (point))
     (push-mark (point-max) nil t)
     (goto-char (point-min)))

So is there something magical about mark-whole-buffer that isn't  
evident in the source? e.g. is it on a list of functions somewhere to  
leave the region highlighted?

I've reproduced this on both Emacs 22.0.50.1 on OS X, and Emacs  
21.3.1 on RHEL4.

Any help much appreciated,
Jon