Re: How to inspect and debug STL containers?

[karsten]

Nice to see this, helped me much, since I was just working on this.
Short remark:

# NOTE: remember to put single quotes around complex types:
# Example  std::list<int>  list1
# (gdb) p_list list1 int
#      --> works
# Example  std::list< std::string >  list1
# (gdb) p_list list1 std::string
#      --> syntax error
# (gdb) whatis list1
#      type = std::list<std::basic_string<char,
std::char_traits<char>, std::allocator<char>
>,std::allocator<std::basic_string<char, std::char_traits<char>,
std::allocator<char> > > >
# (gdb) p_list list1 'std::basic_string<char, std::char_traits<char>,
std::allocator<char> >'
#      --> works, please note the single quotes


I found an older set of macros, which at least worked for gcc 3.2. It
doesn't need so many macro parameters, since the STL classes were
implemented differently and it was easier to debug: one trick was to
notice a data pointer in the class "list" with the correct type, so
that a cast from _List_node_base to _List_node<_Tp> is done by gdb,
please see below. Same worked with std::map.

------------------------------------------------------------------------------------------------------------------------------------------------
set print pretty on
set print object on
set print demangle on
#set overload-resolution on


################################################
# Commands for STL vector ######################
################################################
define stl_vector_len
  output $arg0._M_finish-$arg0._M_start
  echo \n
end

document stl_vector_len
  Print the vector's length
end

###############################################
define stl_vector_pos
  p *($arg0._M_start + $arg1)
  echo \n
end

document stl_vector_pos
  Print the vector's element at specified position
end

###############################################
define stl_vector
  whatis $arg0
  p *$arg0._M_start@($arg0._M_finish-$arg0._M_start)
end

document stl_vector
  Print all the vector's elements
end

##################################################
# Commands for STL map ###########################
##################################################
define stl_map_len
  output $arg0._M_t._M_node_count
  echo \n
end

document stl_map_len
  Print the number of elements stored in the map
end

###############################################
define stl_map
  whatis $arg0
  tree $arg0 $arg0._M_t._M_header->_M_parent
end

document stl_map
  Print the map's elements
end

define tree
# $arg0: map
# $arg1: current root node

  if $arg1->_M_left
    tree $arg0 $arg1->_M_left
  end

# The header pointer has the needed type i.e.
# std::_Rb_tree_node<std::pair<T1 const, T2> > *
# whereas the node is of type (std::_Rb_tree_node_base *). So we copy
# the node pointer temporarily to the header pointer to have the
# correct output
  set $header=$arg0._M_t._M_header
  set variable $arg0._M_t._M_header=$arg1
  print $arg0._M_t._M_header._M_value_field
  set variable $arg0._M_t._M_header=$header

  if $arg1->_M_right
    tree $arg0 $arg1->_M_right
  end
end

document tree
  Auxiliary function used by stl_map
end

###################################################
# Commands for STL list ###########################
###################################################
define stl_list_len
  set $count=0
  set $head=$arg0._M_node
  set $next=$arg0._M_node._M_next
  while $next != $head
    set $next=$next._M_next
    set $count= $count + 1
  end
  output $count
  echo \n
end

document stl_list_len
  Print the list's length
end

###############################################
define stl_list
  whatis $arg0

  set $head=$arg0._M_node
  set $next=$arg0._M_node._M_next
  while $next != $head
    # trick using the _M_node pointer for type conversion to the
correct type
    set variable $arg0._M_node=$next
    print $arg0._M_node._M_data
    set $next=$next._M_next
  end
  set variable $arg0._M_node=$head
end

document stl_list
  Print the list's elements
end