root@a:/mailstore/db.org/users/alice# gdb /usr/local/mailsys/libexec/dovecot/imap core 
GNU gdb (GDB) 7.1-ubuntu
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i486-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /usr/local/mailsys/libexec/dovecot/imap...done.
[New Thread 13008]

warning: Can't read pathname for load map: Input/output error.
Reading symbols from /usr/local/mailsys/lib/dovecot/libdovecot-storage.so.0...done.
Loaded symbols for /usr/local/mailsys/lib/dovecot/libdovecot-storage.so.0
Reading symbols from /usr/local/mailsys/lib/dovecot/libdovecot.so.0...done.
Loaded symbols for /usr/local/mailsys/lib/dovecot/libdovecot.so.0
Reading symbols from /lib/tls/i686/cmov/libdl.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib/tls/i686/cmov/libdl.so.2
Reading symbols from /lib/tls/i686/cmov/librt.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib/tls/i686/cmov/librt.so.1
Reading symbols from /lib/tls/i686/cmov/libc.so.6...(no debugging symbols found)...done.
Loaded symbols for /lib/tls/i686/cmov/libc.so.6
Reading symbols from /lib/ld-linux.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib/ld-linux.so.2
Reading symbols from /lib/tls/i686/cmov/libpthread.so.0...(no debugging symbols found)...done.
Loaded symbols for /lib/tls/i686/cmov/libpthread.so.0
Reading symbols from /usr/local/mailsys/lib/dovecot/lib01_acl_plugin.so...done.
Loaded symbols for /usr/local/mailsys/lib/dovecot/lib01_acl_plugin.so
Reading symbols from /usr/local/mailsys/lib/dovecot/lib02_imap_acl_plugin.so...done.
Loaded symbols for /usr/local/mailsys/lib/dovecot/lib02_imap_acl_plugin.so
Core was generated by `dovecot/imap'.
Program terminated with signal 11, Segmentation fault.
#0  0x00826790 in ?? () from /lib/tls/i686/cmov/libc.so.6
(gdb) bt full
#0  0x00826790 in ?? () from /lib/tls/i686/cmov/libc.so.6
No symbol table info available.
#1  0x00323bcf in mailbox_list_mailbox (list=0x822c8c8, name=0x8061178 "", flags_r=0xbfd7692c) at mailbox-list.c:709
        path = 0x8234f50 "/mailstore/db.org/users//Maildir"
        fname = <value optimized out>
        rootdir = 0x0
        inbox = <value optimized out>
        st = {st_dev = 585594636049871681, __pad1 = 29156, __st_ino = 3077609744, st_mode = 3218565320, 
          st_nlink = 4294967295, st_uid = 3018740, st_gid = 134527722, st_rdev = 13823632823799513089, 
          __pad2 = 9910, st_size = 3021488, st_blksize = 1, st_blocks = 1, st_atim = {tv_sec = 1, 
            tv_nsec = 134523744}, st_mtim = {tv_sec = 134627808, tv_nsec = 0}, st_ctim = {tv_sec = 3174884, 
            tv_nsec = 136344392}, st_ino = 586173391483098976}
#2  0x080519f5 in list_namespace_send_prefix (ctx=0x822d760, have_children=<value optimized out>) at cmd-list.c:285
        listed = <value optimized out>
        flags = <value optimized out>
        name = 0x8207348 "shared"
        str = <value optimized out>
        ends_with_sep = true
#3  0x0805255d in list_namespace_init (cmd=0x822d6d0) at cmd-list.c:717
        pat = <value optimized out>
        ns = 0x8228158
        cur_ref = 0x822fbc8 ""
        pattern = 0x822fbd0 "%"
        inbox_match = 136344320
#4  cmd_list_continue (cmd=0x822d6d0) at cmd-list.c:759
        _data_stack_cur_id = 4
        ctx = 0x822d760
#5  0x08052a68 in cmd_list_full (cmd=0x822d6d0, lsub=false) at cmd-list.c:931
        client = 0x822d0d8
        args = 0x822fb68
        list_args = 0xbfd76ac8
        arg_count = 21
        ctx = 0x822d760
        patterns = {arr = {buffer = 0x822d790, element_size = 4}, v = 0x822d790, v_modifiable = 0x822d790}
        pattern = 0x822fbd0 "%"
        patterns_strarr = <value optimized out>
#6  0x08052e29 in cmd_list (cmd=0x822d6d0) at cmd-list.c:946
No locals.
#7  0x080563bc in client_command_input (cmd=0x822d6d0) at imap-client.c:646
        client = 0x822d0d8
        command = <value optimized out>
        __FUNCTION__ = "client_command_input"
#8  0x08056492 in client_command_input (cmd=0x822d6d0) at imap-client.c:696
        client = 0x822d0d8
        command = <value optimized out>
        __FUNCTION__ = "client_command_input"
#9  0x08056715 in client_handle_next_command (client=0x822d0d8) at imap-client.c:737
        size = 15
#10 client_handle_input (client=0x822d0d8) at imap-client.c:749
        _data_stack_cur_id = 3
        ret = <value optimized out>
        remove_io = 244
        handled_commands = false
        __FUNCTION__ = "client_handle_input"
#11 0x08056fef in client_input (client=0x822d0d8) at imap-client.c:788
        cmd = <value optimized out>
        output = 0x822d5f4
        bytes = <value optimized out>
        __FUNCTION__ = "client_input"
#12 0x005653f2 in io_loop_handler_run (ioloop=0x820f368) at ioloop-epoll.c:212
        ctx = 0x820f488
        event = <value optimized out>
        list = 0x822d678
        io = 0x822d650
        tv = {tv_sec = 1799, tv_usec = 998792}
        t_id = 2
        msecs = 2
        ret = 1
        i = 0
        j = 0
        call = <value optimized out>
#13 0x00564440 in io_loop_run (ioloop=0x820f368) at ioloop.c:350
No locals.
#14 0x00551c8a in master_service_run (service=0x820f2b8, callback=0x805f220 <client_connected>)
    at master-service.c:486
No locals.
#15 0x0805faa5 in main (argc=1, argv=0x820f1c0) at main.c:357
        set_roots = {0x80624c0, 0x0}
        service_flags = <value optimized out>
        storage_service_flags = <value optimized out>
        postlogin_socket_path = 0x0
        username = 0x0
        c = <value optimized out>