# gdb --args xl2tpd -C /var/run/l2tp-control
GNU gdb (Gentoo 7.6 p2) 7.6
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-pc-linux-gnu".
For bug reporting instructions, please see:
<http://bugs.gentoo.org/>...
Reading symbols from /usr/sbin/xl2tpd...done.
(gdb) set follow-fork-mode child
(gdb) run
Starting program: /usr/sbin/xl2tpd -C /var/run/l2tp-control
warning: Could not load shared library symbols for linux-vdso.so.1.
Do you need "set solib-search-path" or "set sysroot"?
[New process 16858]
[New process 16859]
process 16859 is executing new program: /usr/sbin/pppd
warning: Could not load shared library symbols for linux-vdso.so.1.
Do you need "set solib-search-path" or "set sysroot"?
[tcsetpgrp failed in terminal_inferior: No such process]

Program received signal SIGSEGV, Segmentation fault.
[Switching to process 16859]
vslprintf (buf=buf@entry=0x7fffffffdee0 " ", buflen=255, buflen@entry=256, fmt=0x0, args=args@entry=0x7fffffffdec8) at utils.c:175
175 utils.c: No such file or directory.
(gdb) thread apply all backtrace full

Thread 3 (process 16859):
#0  vslprintf (buf=buf@entry=0x7fffffffdee0 " ", buflen=255, buflen@entry=256, fmt=0x0, args=args@entry=0x7fffffffdec8) at utils.c:175
        c = <optimized out>
        i = <optimized out>
        n = <optimized out>
        width = <optimized out>
        prec = <optimized out>
        fillch = <optimized out>
        base = <optimized out>
        len = <optimized out>
        neg = <optimized out>
        quoted = <optimized out>
        val = <optimized out>
        str = <optimized out>
        f = 0x0
        buf0 = 0x7fffffffdee0 " "
        p = <optimized out>
        num = "%\372d\000\000\000\000\000\265\370\336\367\377\177", '\000' <repeats 11 times>, "\001\000\000\000\000\000"
        t = 140737343653728
        hexchars = "0123456789abcdef"
        bufinfo = {ptr = 0x0, len = -8480}
#1  0x00000000004216d5 in pr_log (arg=<optimized out>, fmt=<optimized out>) at utils.c:571
        l = <optimized out>
        n = <optimized out>
        pvar = {{gp_offset = 16, fp_offset = 48, overflow_arg_area = 0x7fffffffe0c0, reg_save_area = 0x7fffffffdfe0}}
        p = <optimized out>
        eol = <optimized out>
        buf = " \000pol2tp\000 /etc/ppp/options1)\n\000\000\000\240\377\377\377\377\377\377\377\020\000\000\000\060\000\000\000\000\341\377\377\377\177\000\000 \340\377\377\377\177\000\000pppd options in effect:\000\000\337\377\377\377\177\000\000i\000\000\000\000\000\000\000\b\026q\367\377\177\000\000\000\237i\000\000\000\000\000p\304i\000\000\000\000\000 \033i\000\000\000\000\000\200q\333\366\377\177\000\000\001\000\000\000\000\000\000\000\001\000\000\000\377\177\000\000\300\300i\000\000\000\000\000\300\337\377\377\377\177\000\000\000\004\000\000\000\000\000\000\030\333\377\377\377\177\000\000p\300i\000\000\000\000\000\000"...
#2  0x000000000041e432 in print_option (mainopt=0x7ffff6db50e0 <pppol2tp_options>, arg=0x0, printer=0x421620 <pr_log>, opt=0x7ffff6db50e0 <pppol2tp_options>) at options.c:971
        i = <optimized out>
        v = <optimized out>
        p = <optimized out>
#3  print_option_list (opt=0x7ffff6db50e0 <pppol2tp_options>, printer=printer@entry=0x421620 <pr_log>, arg=arg@entry=0x0) at options.c:1008
No locals.
#4  0x000000000041e978 in print_options (printer=0x421620 <pr_log>, arg=arg@entry=0x0) at options.c:1030
        list = 0x69d1b0
        i = <optimized out>
#5  0x000000000040b33e in main (argc=12, argv=0x7fffffffe2c8) at main.c:421
        i = <optimized out>
        t = <optimized out>
        p = <optimized out>
        pw = <optimized out>
        protp = <optimized out>
        numbuf = "0", '\000' <repeats 14 times>
(gdb)