Trying to print for example a ps file from the command line :~# xfprint4 filename.ps with the PRINTER variable missing, the program exits with segfault. I digged a little bit in to the code. Around line 409 of xfprint/print_dialog.c, looks like the fault is caused by referencing default_printer->name, as default_printer has NULL value. xfprint4 works perfectly with PRINTER variable set to one of the names in /etc/printcap or /usr/etc/printcap
I forgot this bug and fixed 3816 which seems to have the same cause. *** This bug has been marked as a duplicate of bug 3816 ***