Debugging with ddd : crashes in rtl_ImplGetFastUTF8UnicodeLen

Found it where it crashes at line 645 in Connection.cxx

OUString aData(pResults + 3,
                           isc_vax_integer(pResults, 2),
                           RTL_TEXTENCODING_UTF8);
            

and here is the backtrace at line 634 in ustring.cxx

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7b7aebd in rtl_ImplGetFastUTF8UnicodeLen (pStr=0x7ffffffff000 , nLen=11582, ascii=0x7fffffffc4b8) at /home/mariuz/work/libo/sal/rtl/ustring.cxx:634
(gdb) frame 4
#4  0x00007fff96c9bce2 in connectivity::firebird::Connection::runBackupService (this=0x7fffac0a1400, nAction=1) at /home/mariuz/work/libo/connectivity/source/drivers/firebird/Connection.cxx:645
(gdb) frame 24
#24 0x00007ffff195e906 in SalFrame::CallCallback (this=0x10a7680, nEvent=22, pEvent=0x15fd5d0) at /home/mariuz/work/libo/vcl/inc/salframe.hxx:246
(gdb) frame 23
#23 0x00007ffff1586e00 in ImplWindowFrameProc (_pWindow=0x10a6ce0, nEvent=22, pEvent=0x15fd5d0) at /home/mariuz/work/libo/vcl/source/window/winproc.cxx:2578
(gdb) frame 5
#5  0x00007fff96c9c99c in connectivity::firebird::Connection::documentEventOccured (this=0x7fffac0a1400, _Event=...) at /home/mariuz/work/libo/connectivity/source/drivers/firebird/Connection.cxx:814
(gdb) frame 4
#4  0x00007fff96c9bce2 in connectivity::firebird::Connection::runBackupService (this=0x7fffac0a1400, nAction=1) at /home/mariuz/work/libo/connectivity/source/drivers/firebird/Connection.cxx:645