title: no symbol table info avaliable after analysing coredump in gdb
body: <p>I am new to this unix and gdb. I have a coredump file generated.I am using gdb to debug, but there is no meaningful information found. 
  I am getting output as </p>
  
  <pre>
  (gdb) thread apply all bt full 
  
  Thread 7 (LWP 12190):
  #0  0x00007fa2eae29896 in ?? ()
  No symbol table info available.
  #1  0x000000000000019a in ?? ()
  No symbol table info available.
  #2  0x00007fa2e9906ce0 in ?? ()
  No symbol table info available.
  </pre>
  
  <p>There are 7 seven threads. and for all I am getting the same. I am not getting the way forward to proceed.Please help me. OR please explain me what does this mean.</p>