c++ - Trouble reading a Qt application stacktrace with gdb/qtdebugger -

i have program getting crash.

generally reading stacktrace not issue, in case cannot understand problem is. amunable know part of code causing crash.

i attaching gdb debugger stacktrace:

(gdb) r starting program: /home/r/l33t/kepler/build-supergui-5_2_1-debug/supergui  [thread debugging using libthread_db enabled] using host libthread_db library "/lib/i386-linux-gnu/libthread_db.so.1". [new thread 0xb4762b40 (lwp 6612)] [new thread 0xb327cb40 (lwp 6613)] [new thread 0xb28ffb40 (lwp 6615)] [new thread 0xb1ea3b40 (lwp 6616)] [new thread 0xb16a2b40 (lwp 6617)] [new thread 0xb0ea1b40 (lwp 6618)] [thread 0xb16a2b40 (lwp 6617) exited] connecting...  connected...  [thread 0xb0ea1b40 (lwp 6618) exited]  symbol --banknifty  program received signal sigsegv, segmentation fault. __memcpy_ssse3 () @ ../sysdeps/i386/i686/multiarch/memcpy-ssse3.s:2590 2590    ../sysdeps/i386/i686/multiarch/memcpy-ssse3.s: no such file or directory. (gdb) bt #0  __memcpy_ssse3 () @ ../sysdeps/i386/i686/multiarch/memcpy-ssse3.s:2590 #1  0x081ca9b0 in ?? () #2  0x3143041a in ?? () #3  0x03223930 in ?? () #4  0x2a363530 in ?? () #5  0x4e414209 in ?? () #6  0x46494e4b in ?? () #7  0xb2305954 in ?? () backtrace stopped: previous frame inner frame (corrupt stack?) 

can please me understand how read , how point in code causing crash information ?

the qt debugger more unhelpful :

the dissambler view of qt equally unhelpful (for me understand)

0xb711fe8d  <+0x1cfd>         sub    $0x80,%ecx         2588    in ../sysdeps/i386/i686/multiarch/memcpy-ssse3.s 0xb711fe93  <+0x1d03>         movntdq %xmm0,(%edx)         2589    in ../sysdeps/i386/i686/multiarch/memcpy-ssse3.s 0xb711fe97  <+0x1d07>         movntdq %xmm1,0x10(%edx)         2590    in ../sysdeps/i386/i686/multiarch/memcpy-ssse3.s 0xb711fe9c  <+0x1d0c>         movntdq %xmm2,0x20(%edx)         2591    in ../sysdeps/i386/i686/multiarch/memcpy-ssse3.s 

it said program crashed @ line 2589 in dissambler output ..

what wrong ?

here part of code think might causing crash (this working on right now)

void tradeview::readyread() {     std::cout << "line 70" << "\n";     char delimiter_buffer[sizeof(google::protobuf::uint32)]; // read max size protobuf might write.     memset(delimiter_buffer, '\0', sizeof(google::protobuf::uint32));      char* proto_data_buffer;    // buffer should have been of type google::protobuf::uint8     //memset(proto_data_buffer, '\0', sizeof(google::protobuf::uint32));      google::protobuf::uint32 payload_size = 0;     int space_takenby_delimiter = 0;     size_t startof_extra_read, extra_read;     std::cout << "line 79" << "\n";     if ( socket->read(delimiter_buffer, sizeof(google::protobuf::uint32)) != -1)     {         google::protobuf::io::arrayinputstream ais(delimiter_buffer,sizeof(google::protobuf::uint32));         google::protobuf::io::codedinputstream coded_input(&ais);         coded_input.readvarint32(&payload_size);          proto_data_buffer = new char[payload_size]; // buffer should have been of type google::protobuf::uint8         space_takenby_delimiter = coded_input.currentposition();          if (space_takenby_delimiter < 1)         {             std::cout << "could not read delimiter";             return;         }          if ( space_takenby_delimiter < sizeof(google::protobuf::uint32) )         {             startof_extra_read = ( sizeof(google::protobuf::uint32) - (sizeof(google::protobuf::uint32) - space_takenby_delimiter) );             extra_read = (sizeof(google::protobuf::uint32) - space_takenby_delimiter);             std::cout << "line 99" << "\n";             memcpy(proto_data_buffer, delimiter_buffer + startof_extra_read , extra_read);             std::cout << "line 101" << "\n";          }     }      size_t bytes_stilltoberead = payload_size - extra_read;     char payload_buffer[bytes_stilltoberead];      if ( socket->read(payload_buffer, bytes_stilltoberead) != -1)     {         std::cout << "line 110" << "\n";         memcpy(proto_data_buffer + extra_read, payload_buffer, bytes_stilltoberead);         std::cout << "line 112" << "\n";         google::protobuf::io::arrayinputstream array_input(proto_data_buffer, payload_size);         google::protobuf::io::codedinputstream coded_input(&array_input);         data_model::terminal_data* tdata = new data_model::terminal_data();         if (!tdata->parsefromcodedstream(&coded_input))            std::cout << "could not fetch parse  " << std::endl;         else            std::cout <<" symbol --" << tdata->symbol_name() << std::endl;     }     delete proto_data_buffer; } 

the above function slot in qt. invoked each time there data in socket. executes once (correctly) , there crash. have debug statement (as can see) @ first line of function. since not getting printed, guessing fucntion not @ fault ? because of function got screwed somewhere manifested crash ? getting pro me. can please me !

proto_data_buffer , extra_read not inited. if following condition not satisfied:

if ( socket->read(delimiter_buffer, sizeof(google::protobuf::uint32)) != -1) 

then proto_data_buffer point address. extra_read.

these lead wrong address operation in line:

memcpy(proto_data_buffer + extra_read, payload_buffer, bytes_stilltoberead);