added test for CC value not matching cache
diff --git a/configure.in b/configure.in
index 0ef0473..78ec997 100644
--- a/configure.in
+++ b/configure.in
@@ -17,6 +17,13 @@
esac], [without_gcc=no])
AC_MSG_RESULT($without_gcc)
+# If the user switches compilers, we can't believe the cache
+if test ! -z "$ac_cv_prog_CC" -a ! -z "$CC" -a "$CC" != "$ac_cv_prog_CC"
+then
+ AC_ERROR(cached CC is different -- throw away $cache_file
+(it is also a good idea to do 'make clean' before compiling))
+fi
+
AC_PROG_CC
AC_PROG_RANLIB
AC_SUBST(AR)