Why isn't Eclipse using GDB's pretty printing?

Question

I am using Eclipse 4.4.2 on Ubuntu 14.04, and GDB 7.7.1. I am trying to inspect the contents of some C++ standard library containers in the Eclipse debugger.

What I have tried so far: following instructions here, I ran the command

svn co svn://gcc.gnu.org/svn/gcc/trunk/libstdc++-v3/python

Copying it into /home/myusername/prettyprint.

Then I copied this text into my .gdbinit:

python
import sys
sys.path.insert(0, '/home/myusername/prettyprint/python')
from libstdcxx.v6.printers import register_libstdcxx_printers
register_libstdcxx_printers (None)
end

When I ran gdb, I got this error message:

Traceback (most recent call last):
  File "<string>", line 4, in <module>
  File "/home/myusername/prettyprint/python/libstdcxx/v6/printers.py", line 1266, in register_libstdcxx_printers
    gdb.printing.register_pretty_printer(obj, libstdcxx_printer)
  File "/usr/myusername/gdb/python/gdb/printing.py", line 146, in register_pretty_printer
    printer.name)
RuntimeError: pretty-printer already registered: libstdc++-v6

I searched for help on this, and found that the second last line in the file (register_libstdcxx_printers (None)) was not necessary, so I removed it. Then, when I ran gdb and typed:

info pretty-print

I got this output, indicating that the backend was installed properly:

global pretty-printers:
  .*
    bound
  libstdc++-v6
    __gnu_cxx::_Slist_iterator
    __gnu_cxx::__7::_Slist_iterator
    __gnu_cxx::__7::__normal_iterator
    __gnu_cxx::__7::slist
    __gnu_cxx::__normal_iterator
    __gnu_cxx::slist
    __gnu_debug::_Safe_iterator
    std::_Deque_const_iterator
    std::_Deque_iterator
    std::_List_const_iterator
    std::_List_iterator
    std::_Rb_tree_const_iterator
    std::_Rb_tree_iterator
    std::__7::_Deque_const_iterator
    std::__7::_Deque_iterator
    std::__7::_List_const_iterator
    std::__7::_List_iterator
    std::__7::_Rb_tree_const_iterator
---Type <return> to continue, or q <return> to quit---
    std::__7::_Rb_tree_iterator
    std::__7::__cxx11::basic_string
    std::__7::basic_string
    std::__7::bitset
    std::__7::deque
    std::__7::forward_list
    std::__7::list
    std::__7::map
    std::__7::multimap
    std::__7::multiset
    std::__7::priority_queue
    std::__7::queue
    std::__7::set
    std::__7::shared_ptr
    std::__7::stack
    std::__7::tuple
    std::__7::unique_ptr
    std::__7::unordered_map
    std::__7::unordered_multimap
    std::__7::unordered_multiset
    std::__7::unordered_set
    std::__7::vector
    [... many more lines of output omitted]

For good measure, I added the following lines to .gdbinit:

set print pretty on
set print object on
set print static-members on
set print vtbl on
set print demangle on
set demangle-style gnu-v3
set print sevenbit-strings off

So I opened Eclipse and started debugging my application, only to find that the ugly print was still in effect:

How can I fix this to use GDB's pretty print; is pretty print even installed?

Answer 1

The values in your screenshot look like memory addresses, which leads me to believe you're trying to inspect a pointer to an instance of an STL type. AFAIK, the pretty printers won't automatically dereference pointers, but will pretty-print if you add a watch expression that deferences the pointer.

The additional .gdbinit lines you're using shouldn't be necessary; the following steps are all that should be required (for Eclipse Mars.1):

1. Download the pretty printers:

   svn co svn://gcc.gnu.org/svn/gcc/trunk/libstdc++-v3/python
   

2. Create a /home/<user>/.gdbinit file with the following contents:

   python
   import sys
   sys.path.insert(0, '/path/to/prettyprint/python')
   from libstdcxx.v6.printers import register_libstdcxx_printers
   end
   

3. In the GDB settings for Eclipse (Window->Preferences->C/C++->Debug->GDB), set the GDB command file path to the .gdbinit file you just created.

4. For any existing debug configurations (Run->Debug Configurations) which require pretty-printing, select the debug configuration, then set the GDB command file path on the Debugger tab.

You can verify that GDB is pretty-printing as follows (once the first two steps of the previous procedure have been completed):

1. Save the following code in a file named test.cpp:

   #include <map>
   int main() {
       std::map<char, int> first;
       first['a'] = 10;
       first['b'] = 20;
   }
   

2. Compile with g++:

   $ g++ -g -o test test.cpp
   

3. Run gdb:

   $ gdb test
   

4. Set a break point:

   (gdb) b test.cpp:5
   Breakpoint 1 at 0x40093f: file src/test.cpp, line 5.
   

5. Run the program:

   (gdb) run
   Starting program: /path/to/test
   

6. When the break point is hit, the gdb prompt will be displayed. Print the map with the following command:

   (gdb) p first
   

   If all is well, you should see the following output:

   $1 = std::map with 1 elements = {[97 'a'] = 10}