For non-static member functions, the implicit this pointer is displayed as the address on the stack trace along with the class type of the object, as shown in the following example:
GDB Mode
(idb) break List<Node>::print
Breakpoint 3 at 0x804aee2: file src/x_list.cxx, line 162.
(idb) continue
Continuing.
Breakpoint 3, List<Node>::print (this=0xbfff8db0) at src/x_list.cxx:162
162 Node* currentNode = _firstNode;
(idb) backtrace 2
#0 0x0804aee2 in List<Node>::print (this=0xbfff8db0) at src/x_list.cxx:162
#1 0x08051a3c in main () at src/x_list.cxx:203
DBX Mode
(idb) stop in List<Node>::print
[#3: stop in void List<Node>::print(void) const]
(idb) cont
[3] stopped at [void List<Node>::print(void) const:162 0x0804aee2]
162 Node* currentNode = _firstNode;
(idb) where 2
>0 0x0804aee2 in ((List<Node>*)0xbfff83f0)->List<Node>::print() "src/x_list.cxx":162
#1 0x08051a3c in main() "src/x_list.cxx":203