BufFilePut is called (through FontFilePutc macro) with some (shr-ed or not)
ints. int may be equal -1 (e.g. 0xFFFFFFFF or 0xFFxxxxxx >> 24). -1 has
special meaning for BufFileRawFlush (just flush instead of write char and
flush), so any FF values on buffer boundary disappeared...

--- XFree86-4.1.0/xc/lib/font/include/bufio.h.orig	Wed Jan 17 20:43:31 2001
+++ XFree86-4.1.0/xc/lib/font/include/bufio.h	Mon Jul  2 13:25:41 2001
@@ -74,7 +74,7 @@
 extern void BufFileFree ( BufFilePtr );
 
 #define BufFileGet(f)	((f)->left-- ? *(f)->bufp++ : ((f)->eof = (*(f)->input) (f)))
-#define BufFilePut(c,f)	(--(f)->left ? *(f)->bufp++ = (c) : (*(f)->output) (c,f))
+#define BufFilePut(c,f)	(--(f)->left ? *(f)->bufp++ = ((unsigned char)(c)) : (*(f)->output) ((unsigned char)(c),f))
 #define BufFileSkip(f,c)    ((f)->eof = (*(f)->skip) (f, c))
 
 #ifndef TRUE