AC_CONFIG_HEADERS vs. AC_CONFIG_FILES

[David Fang]

Hi,
        Is there a way to produce a header file at configure time using
AC_CONFIG_HEADERS, *and* have it perform AC_SUBST-itutions on the files,
like AC_CONFIG_FILES?
        What I'd like is AC_CONFIG_FILES to also perform a difference
check on the output files before overwriting them, just the way
AC_CONFIG_HEADERS does.  (Is this a safe and easy request to accommodate?)
In my case, these output files are headers at the leaves of deep
dependency-chains (not all C/C++).
        I basically do NOT want to AC_DEFINE such variables because they
will end up changing config.h -- I'd rather have these variables isolated
from config.h.  Another idea could be to provide an option in AC_DEFINE to
retarget to another file besides the default "config.h"?
        Any ideas?

David Fang