Is there something wrong with my GDB? - c++

Question

My program hangs hard (nigh freezes my whole computer), and I'm trying to figure out where it's happening. I've gone through some gdb tutorials and other things—and followed them pretty well. Whenever I see gdb output, though, it's somewhat clean and readable (that is, its output seems to at least relate to the file which it is debugging).
Here's a small chunk of my gdb's output:
23 std::map<std::string, int> Item::getStats() { return enhancements_; };
(gdb) step
Python Exception <class 'ValueError'> Cannot find type const std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, int> > >::_Rep_type:
map (__x=std::map with 2 elements, this=0x7fffffffd0c0)
at src/item.cpp:23
23 std::map<std::string, int> Item::getStats() { return enhancements_; };
(gdb) step
_Rb_tree (__x=..., this=0x7fffffffd0c0) at src/item.cpp:23
23 std::map<std::string, int> Item::getStats() { return enhancements_; };
(gdb) step
_Rb_tree_impl (__a=<optimized out>, __comp=..., this=0x7fffffffd0c0)
at /usr/include/c++/4.9/bits/stl_tree.h:474
474 _M_header(), _M_node_count(0)
(gdb) step
475 { _M_initialize(); }
(gdb) step
_M_initialize (this=0x7fffffffd0c0)
at /usr/include/c++/4.9/bits/stl_tree.h:484
484 this->_M_header._M_left = &this->_M_header;
(gdb)
485 this->_M_header._M_right = &this->_M_header;
(gdb) step
_Rb_tree (__x=..., this=0x7fffffffd0c0)
at /usr/include/c++/4.9/bits/stl_tree.h:674
674 if (__x._M_root() != 0)
(gdb) step
_M_root (this=0x7fffffffd038)
at /usr/include/c++/4.9/bits/stl_tree.h:498
498 { return this->_M_impl._M_header._M_parent; }
Is there something up with my gdb or is this how it's generally supposed to read? I'm not seeing anything from the other header files or code outside of main.cpp. Only three of the above lines seem to relate to my code at all.
Edit:
I'm using G++ 4.9.2 and GDB 7.7.1 on Ubuntu 14.04 w/ Python 2.7.6
The output of 'where' is:
(gdb) where
#0 _int_malloc (av=0x7ffff7840760 <main_arena>, bytes=48) at malloc.c:3775
#1 0x00007ffff75047b0 in __GI___libc_malloc (bytes=48) at malloc.c:2891
#2 0x00007ffff7aebf18 in operator new(unsigned long) () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#3 0x00000000004016f7 in allocate (__n=1, this=0x7fffffffd0c0) at /usr/include/c++/4.9/ext/new_allocator.h:104
#4 allocate (__n=1, __a=...) at /usr/include/c++/4.9/bits/alloc_traits.h:357
#5 _M_get_node (this=0x7fffffffd0c0) at /usr/include/c++/4.9/bits/stl_tree.h:385
#6 _M_create_node<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, int> const&> (this=0x7fffffffd0c0)
at /usr/include/c++/4.9/bits/stl_tree.h:417
#7 _M_clone_node (__x=0xa7b82fa0, this=0x7fffffffd0c0) at /usr/include/c++/4.9/bits/stl_tree.h:445
#8 std::_Rb_tree<std::string, std::pair<std::string const, int>, std::_Select1st<std::pair<std::string const, int> >, std::less<std::string>, std::allocator<std::pair<std::string const, int> > >::_M_copy (this=this#entry=0x7fffffffd0c0, __x=0xa7b82fa0, __p=0xa7b82fa0,
__p#entry=0x7fffffffd0c8) at /usr/include/c++/4.9/bits/stl_tree.h:1219
#9 0x0000000000401cc5 in _Rb_tree (__x=..., this=0x7fffffffd0c0) at /usr/include/c++/4.9/bits/stl_tree.h:676
Python Exception <class 'ValueError'> Cannot find type const std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, int> > >::_Rep_type:
#10 map (__x=std::map with 2 elements, this=0x7fffffffd0c0) at /usr/include/c++/4.9/bits/stl_map.h:183
#11 Item::getStats (this=0x7fffffffd020) at src/item.cpp:23
#12 0x00000000004011a5 in main () at src/main.cpp:26
I can walk up and down the stack, backtrace, set breaks, and things like this—but all the output is similar in its format. I was expecting to see something a little cleaner, with more relevance to the code that I'm debugging. Something like what's in this tutorial:
Breakpoint 1, LinkedList<int>::remove (this=0x40160,
item_to_remove=#0xffbef014) at main.cc:52
52 Node<T> *marker = head_;
(gdb) step
53 Node<T> *temp = 0; // temp points to one behind as we iterate
(gdb)
55 while (marker != 0) {
(gdb)
56 if (marker->value() == item_to_remove) {
(gdb)
Node<int>::value (this=0x401b0) at main.cc:30
30 const T& value () const { return value_; }
(gdb)
LinkedList<int>::remove (this=0x40160, item_to_remove=#0xffbef014)
at main.cc:75
75 marker = 0; // reset the marker
(gdb)
76 temp = marker;
(gdb)
77 marker = marker->next();
(gdb)
Node<int>::next (this=0x0) at main.cc:28
28 Node<T>* next () const { return next_; }
(gdb)
Program received signal SIGSEGV, Segmentation fault.
Node<int>::next (this=0x0) at main.cc:28
28 Node<T>* next () const { return next_; }
(gdb)
Mine seems unintelligible compared to that.

Answer 1

I have no idea why your program freezes your whole computer, but the problem is obvious right here:
75 marker = 0; // reset the marker
76 temp = marker;
77 marker = marker->next();
If you ignore line 76, and just read the code, it appears to be clearly wrong. Perhaps you meant to write:
marker = marker->next();