As you may know, RedHat has made a highly controversial move by shipping a new version of gcc (actually the snapshot of a work in progress) with the 7.0 distribution. It is labeled "2.96". This had the sad effect, among other things, to break a lot of C++ code around. However, given the large base of RedHat users, we may want that those who want can compile gltt effortlessly, while at the same time keeping people using another compiler happy. The problem would have surfaced at one time or another anyway, with the upcoming of the new gcc compiler. So, I would (humbly) suggest to alter the conditional around CALLBACKARG, as shown by the patch below:

--- gltt-2.5/GLTTGlyphPolygonizer.C     Sun Nov 21 02:04:43 1999
+++ gltt-2.5-new/GLTTGlyphPolygonizer.C Thu Nov  2 00:03:56 2000
@@ -107,7 +107,7 @@
 #endif

 // IMHO, the (...) vs. (void) warning is due to GNU-C/C++.
-#if defined(__GNUC__) || defined(_GNUG_)
+#if (defined(__GNUC__) || defined(_GNUG_)) && !__GNUC_PREREQ(2,96)
  #define CALLBACKARG ...
 #else
  #define CALLBACKARG void