Printing useful STL container information with GDB

GDB's "p variable-name" is the Swiss Army knife of the programmer, except when it comes to examine the contents of STL containers.

(gdb) p fieldInd
$110 = {
  <std::_Vector_base<unsigned long, std::allocator<unsigned long> >> = {
    _M_impl = {
      <std::allocator<unsigned long>> = {
        <__gnu_cxx::new_allocator<unsigned long>> = {<No data fields>}, <No data fields>}, 
      members of std::_Vector_base<unsigned long, std::allocator<unsigned long> >::_Vector_impl: 
      _M_start = 0x646c60, 
      _M_finish = 0x646cc8, 
      _M_end_of_storage = 0x646d20
    }
  }, <No data fields>}

This tutorial gives you useful information to have GDB print useful STL container information for you.

(gdb) pvector perm
elem[0]: $111 = 4
elem[1]: $112 = 2
elem[2]: $113 = 0
elem[3]: $114 = 3
elem[4]: $115 = 1
elem[5]: $116 = 5
Vector size = 6
Vector capacity = 6
Element type = unsigned long *