How to pretty-print STL containers in GDB?

It just works on Ubuntu 17.04

Debian seems to have finally integrated things properly now:

main.cpp

#include <map>
#include <utility>
#include <vector>

int main() {
    std::vector<int> v;
    v.push_back(0);
    v.push_back(1);
    v.push_back(2);
    std::map<int,int> m;
    m.insert(std::make_pair(0, 0));
    m.insert(std::make_pair(1, -1));
    m.insert(std::make_pair(2, -2));
}

Compile:

g++ -O0 -ggdb3 -o main.out -std=c++98 main.cpp

Outcome:

(gdb) p v
$1 = std::vector of length 3, capacity 4 = {0, 1, 2}
(gdb) p m
$2 = std::map with 3 elements = {[0] = 0, [1] = -1, [2] = -2}

We can see that the pretty printer is installed with:

(gdb) info pretty-printer

Which contains the lines:

global pretty-printers:
  objfile /usr/lib/x86_64-linux-gnu/libstdc++.so.6 pretty-printers:
  libstdc++-v6
    std::map
    std::vector

The printers are provided by the file:

/usr/share/gcc-7/python/libstdcxx/v6/printers.py

which comes with the main C++ library package libstdc++6 and is located under libstdc++-v3/python/libstdcxx in the GCC source code: https://github.com/gcc-mirror/gcc/blob/releases/gcc-6.3.0/libstdc%2B%2B-v3/python/libstdcxx/v6/printers.py#L244

TODO: how GDB finds that file is the final mistery, it is not in my Python path: python -c "import sys; print('\n'.join(sys.path))" so it must be hardcoded somewhere?

Custom classes

See how to define a custom toString method and call it at: Printing C++ class objects with GDB

Inspect specific elements in optimized code

It was hard last time I checked, you get "Cannot evaluate function -- may be in-lined" C++, STL, GDB: Cannot evaluate function maybe inlined

On unoptimized code it works: Inspecting standard container (std::map) contents with gdb

You can try with below GDB macro (append it to your ~/.gdbinit file) to print STL containter types data and even their data members: https://gist.github.com/3978082

I ran on this problem and hit this page while trying to figure it out. I eventually fixed it, and I thought it would be worth it to share my experience.

I am using gcc-5.2, so I downloaded the gcc-5-branch version of pretty printer from the svn repo. However, I had to do these two mods:

1. when editing the ~/.gdbinit file, the suggested addition is

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

However, I had to comment the line register_libstdcxx_printers (None), since I kept getting an error telling me the libstdcxx_printers were already registered. Apparently they get registered during the import phase.

2. I had to edit the printers.py file for std::set and std::map. Since the type _Rep_type is private in both. In particular, I replace the routine children in std::map and std::set with the corresponding one in the version of pretty printer from the gcc-4_6-branch version on the svn repo. Got no error ever since, and stuff prints out nicely now.

Hope this helps.