gdb complains about missing Python module libstdcxx.v6.printers

[Jon Bailey]

This appears to be a regression of Debian Bug 726094
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=726094

Invoking GDB on any C++ program generates the message:

Traceback (most recent call last):
  File "/usr/share/gdb/auto-load/usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.19-gdb.py", line 63, in <module>
    from libstdcxx.v6.printers import register_libstdcxx_printers
ImportError: No module named 'libstdcxx'

My system info:
$ lsb_release -rd
Description: Ubuntu 14.04.2 LTS
Release: 14.04
$ apt-cache policy libstdc++6-4.8-dbg
libstdc++6-4.8-dbg:
  Installed: 4.8.4-2ubuntu1~14.04
  Candidate: 4.8.4-2ubuntu1~14.04
  Version table:
 *** 4.8.4-2ubuntu1~14.04 0
        500 http://us.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     4.8.2-19ubuntu1 0
        500 http://us.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages

Expected to happen:
  No Python tracebacks in GDB
What happened instead:
  ImportError: No module named 'libstdcxx'

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: libstdc++6-4.8-dbg 4.8.4-2ubuntu1~14.04
ProcVersionSignature: Ubuntu 3.13.0-57.95-generic 3.13.11-ckt21
Uname: Linux 3.13.0-57-generic x86_64
NonfreeKernelModules: nvidia zfs zunicode zavl zcommon znvpair
ApportVersion: 2.14.1-0ubuntu3.11
Architecture: amd64
Date: Fri Jul 10 18:03:53 2015
ProcEnviron:
 TERM=screen
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: gcc-4.8
UpgradeStatus: Upgraded to trusty on 2014-04-28 (438 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Ionut (albertino)]

If anyone is still having this problem (as I just had), I have found that the solution explained here: https://bugs.launchpad.net/ubuntu/+source/gcc-4.8/+bug/1446828 solves it.

Basically, you have to comment lines 51 and 52, the ones dealing with multiarch, in /usr/share/gdb/auto-load/usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.19-gdb.py

After doing that, pretty printers should work.

[Ionut (albertino)]

In case it's ever needed, for the future, the relevant lines that should be commented are:

    if not os.path.basename(os.path.dirname(__file__)).startswith('lib'):
        backdirs += 1 # multiarch subdir