How to use cache variables

[John D. Burger]

I have what I think is a style question:

If I want to do something with the results of autoconf tests in my
configure script, what's the best way to check these results?  For
instance, say I'd like to do this:

  AC_CHECK_LIB(norman, snStackPush)
  AC_CHECK_HEADERS([norman.h])

  # Gripe if neither the library nor the header is around

  if test $SOME_VAR = no && test $SOME_OTHER_VAR = no; then
    AC_MSG_WARN([$PACKAGE requires libnorman])
  fi

My question is, are SOME_VAR and SOME_OTHER_VAR things I should set
myself in the optional arguments to the AC_CHECK macros, or should I use
cache variables?  I'm uneasy about using the latter, because I've had
trouble predicting the names of some macros' cache vars, and having to
slog through the generated configure
script makes me think I'm doing something wrong.

Thanks.

- John Burger
  MITRE