Hopefully useful now...
GNU gdb 6.8-debian Copyright (C) 2008 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-linux-gnu"... (no debugging symbols found)
warning: Can't read pathname for load map: Input/output error. Reading symbols from /usr/lib/dovecot/libdovecot-storage.so.0...(no debugging symbols found)...done. Loaded symbols for /usr/lib/dovecot/libdovecot-storage.so.0 Reading symbols from /usr/lib/dovecot/libdovecot.so.0...(no debugging symbols found)...done. Loaded symbols for /usr/lib/dovecot/libdovecot.so.0 Reading symbols from /lib/libdl.so.2...(no debugging symbols found)...done. Loaded symbols for /lib/libdl.so.2 Reading symbols from /lib/librt.so.1...(no debugging symbols found)...done. Loaded symbols for /lib/librt.so.1 Reading symbols from /lib/libc.so.6...(no debugging symbols found)...done. Loaded symbols for /lib/libc.so.6 Reading symbols from /lib/ld-linux-x86-64.so.2...(no debugging symbols found)...done. Loaded symbols for /lib64/ld-linux-x86-64.so.2 Reading symbols from /lib/libpthread.so.0... (no debugging symbols found)...done. Loaded symbols for /lib/libpthread.so.0 Reading symbols from /usr/lib/dovecot/modules/lib01_acl_plugin.so...(no debugging symbols found)...done. Loaded symbols for /usr/lib/dovecot/modules/lib01_acl_plugin.so Reading symbols from /usr/lib/dovecot/modules/lib02_imap_acl_plugin.so...(no debugging symbols found)...done. Loaded symbols for /usr/lib/dovecot/modules/lib02_imap_acl_plugin.so Reading symbols from /usr/lib/dovecot/modules/lib10_quota_plugin.so...(no debugging symbols found)...done. Loaded symbols for /usr/lib/dovecot/modules/lib10_quota_plugin.so Reading symbols from /usr/lib/dovecot/modules/lib11_imap_quota_plugin.so...(no debugging symbols found)...done. Loaded symbols for /usr/lib/dovecot/modules/lib11_imap_quota_plugin.so Reading symbols from /usr/lib/dovecot/modules/lib20_fts_plugin.so...(no debugging symbols found)...done. Loaded symbols for /usr/lib/dovecot/modules/lib20_fts_plugin.so Reading symbols from /usr/lib/dovecot/modules/lib21_fts_squat_plugin.so... (no debugging symbols found)...done. Loaded symbols for /usr/lib/dovecot/modules/lib21_fts_squat_plugin.so (no debugging symbols found) Core was generated by `dovecot/imap'. Program terminated with signal 11, Segmentation fault. [New process 17997] #0 0x00007f256d8c86ee in hash_table_destroy () from /usr/lib/dovecot/libdovecot.so.0 (gdb) bt full #0 0x00007f256d8c86ee in hash_table_destroy () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #1 0x00007f256d8a54c4 in settings_parser_deinit () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #2 0x00007f256d8c0bbc in master_service_settings_cache_deinit () from /usr/lib/dovecot/libdovecot.so.0 No symbol table info available. #3 0x00007f256db33709 in mail_storage_service_deinit () from /usr/lib/dovecot/libdovecot-storage.so.0 No symbol table info available. #4 0x0000000000418629 in main () No symbol table info available.
Feb 28 17:15:22 spectre dovecot: master: service(imap): child 17997 killed with signal 11 (core dumped)