autconf, configure & purify...

[Boggis, Antony]

After much googling and no answers (and least, none I can understand) I am 
resorting to querying the wisdom of this list (and excuse me if cc'ing is 
frowned upon).

We have a build environment that as it is, works pretty well.

I have a global script that does the following (in this order):

aclocal         (aclocal (GNU automake) 1.7.3)
autoheader              (autoheader (GNU Autoconf) 2.57)
automake -a             (automake (GNU automake) 1.7.3)
autoconf                (autoconf (GNU Autoconf) 2.57)

This results in the following files being created:
        configure
        Makefile
        libtool

Then, using gmake, all is good.

Now, I wish to introduce the usage of Purify into the equation.

So, I have the following section in configure.ac:

--- BEGIN ---
AC_ARG_ENABLE(purify,
AS_HELP_STRING(--enable-purify,build with Purify [[default=no]]),
[case "${enableval}" in
yes) enable_purify=true ;;
no) enable_purify=false ;;
*) AC_MSG_ERROR([bad value ${enableval} for --enable-purify, need yes or no]) ;;
esac],
[enable_purify=no])

if test "$enable_purify" = "true"; then
  AC_CHECK_PROGS(PURIFY,purify purify2002)

  if test -z $PURIFY; then
     AC_MSG_ERROR([purify requested, but unable to find purify])
  fi

  CPPFLAGS="$CPPFLAGS -DNOSMALLOC -DPURIFY"

  AC_DEFINE(USE_PURIFY,1,[Use Purify])

  AC_SUBST(PURIFY,$PURIFY)
  AC_SUBST(USE_PURIFY,1)
fi
--- END ---

This results in USE_PURIFY and PURIFY being defined:

        Final USE_PURIFY is 1
        Final PURIFY is purify

BUT, when I run my build purify is not being invoked at build time, even though 
I am getting my compile define "-DPURIFY".

For both the compile and link steps, libtool is being correctly invoked with 
the right value for mode (--mode=compile or --mode=link). I added a call to 
$echo in libtool:

    $echo "$modename: *** PURIFY = $PURIFY" 1>&2
    $echo "$modename: *** USE_PURIFY = $USE_PURIFY" 1>&2

In the link mode section. The lines get echoed, but the values are empty. Hence 
no purify.

Can anyone offer advice, suggestions? I'm no Unix expert (certainly not in this 
area, anyway), so be gentle!

--
tonyB.