xscreensaver 5.12-* contains (in the upstream 5.12 tarball) the following change relative to 5.11-9 (using 5.11 upstream):

diff -rU3 11-9/xscreensaver-5.11/hacks/flame.c 12-1/xscreensaver-5.12/hacks/flame.c
--- 11-9/xscreensaver-5.11/hacks/flame.c        2008-07-31 10:29:35.000000000 +0100
+++ 12-1/xscreensaver-5.12/hacks/flame.c        2010-05-24 06:39:51.000000000 +0100
@@ -173,7 +173,7 @@
 static int
 recurse (struct state *st, double x, double y, int l, Display *dpy, Window win)
 {
-  int xp, yp, i;
+  int /*xp, yp,*/ i;
   double nx, ny;
 
   if (l == st->max_levels)
@@ -184,8 +184,8 @@
 
       if (x > -1.0 && x < 1.0 && y > -1.0 && y < 1.0)
        {
-         xp = st->points[st->num_points].x = (int) ((st->width / 2) * (x + 1.0));
-         yp = st->points[st->num_points].y = (int) ((st->height / 2) * (y + 1.0));
+/*       xp = st->points[st->num_points].x = (int) ((st->width / 2) * (x + 1.0));
+         yp = st->points[st->num_points].y = (int) ((st->height / 2) * (y + 1.0));*/
          st->num_points++;
          if (st->num_points >= POINT_BUFFER_SIZE)
            {


This doesn't appear to be mentioned in the changelog (file README in the tarball), but has the effect that the flame display is now blank.

Note that though xp and yp are unused in the rest of the function and could be removed (and were presumably removed because newer gcc versions whine about the unused locals), the two removed assignments also assign to the points array passed to XDrawPoints, so instead all points drawn are left as [0, 0].