Ubuntu 14.04, gcc 4.8.4: gdb pretty printing doesn't work because of Python issue

Question

I'm getting this error when launching a program in gdb:

Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
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'

Google turned up this bug report: http://osdir.com/ml/debian-gcc/2014-02/msg00061.html This bug report list using the command python print sys.path on the gdb prompt. However, when I try to use any python on the gdb prompt, this happens:

(gdb) python print sys.path
File "<string>", line 1
print sys.path
        ^
SyntaxError: invalid syntax
Error while executing Python code.

(gdb) python print "Hello"
File "<string>", line 1
print "HellO"
            ^
SyntaxError: invalid syntax
Error while executing Python code.

I'm using Ubuntu 14.04 LTS, relevant version information:

$ gcc --version
gcc (Ubuntu 4.8.4-2ubuntu1~14.04) 4.8.4
$ gdb --version
GNU gdb (Ubuntu 7.7.1-0ubuntu5~14.04.2) 7.7.1
$ python --version
Python 2.7.6

Clearly, something in my setup is broken. Is it python, gdb, or something else?

Eau

Ubuntu 14.04 builds gdb with python 3, so print is now a function; use (gdb) python print(sys.path) – Kilowatthour

Thanks, that answers that question. However, the original error "ImportError: No module named 'libstdcxx'" still remains. Does that mean this script needs to be converted to python 3? – Eau

The script in libstdc++.so.6.0.19-gdb.py ought to be fixed as per that email message, and possibly ported to python 3 (I haven't looked at it really closely yet). But if your target is compiled with the system version of gcc (i.e. you're not cross-compiling nor using a version of gcc different from the one that came with the system), you can just do (gdb) python sys.path.append("/usr/share/gcc-4.8/python"); then it won't matter that the libstdc++.so.6.0.19-gdb.py script adds a nonexistent directory to the path. – Kilowatthour

@Mark: Thanks! I also added this line in ~/.gdbinit and it's automatically loaded each time gdb is run: python sys.path.append("/usr/share/gcc-4.8/python") – Ambivalence

Confirmed bug: bugs.launchpad.net/ubuntu/+source/gcc-4.8/+bug/1473599...or more helpfully here: bugs.launchpad.net/ubuntu/+source/gcc-4.8/+bug/1446828. Comment out the two lines with the if statement containing multiarch and the problem will go away(in /usr/share/gdb/auto-load/usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.19-gdb.py). – Overwinter

Answer 1

I'm posting this as an answer so it will be easier for others to find it. The comments from Mark Plotnick and webbertiger are the actual answer.

To summarize, here is what worked for me:

• Created a ~/.gdbinit file
• Added python sys.path.append("/usr/share/gcc-4.8/python"); to that file

I'm using Eclipse CDT so I checked that this file is being used in window > preferences > GDB > GDB command file.

Bireme