double free from xdressed pair of custom type

gistfile1.txt

** Error in `/usr/bin/python': double free or corruption (fasttop): 0x00000000018a60e0 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x80996)[0x7ffff7875996]
/usr/lib/x86_64-linux-gnu/libstdc++.so.6(_ZNSsD1Ev+0x1f)[0x7ffff0e8405f]
/home/gidden/work/xdress/tests/cppproj/install-gccxml/lib/python2.7/site-packages/cppproj/pybasics.so(_ZN7cppproj18SomeCrazyPairValueD1Ev+0x18)[0x7fffef57807e]
/home/gidden/work/xdress/tests/cppproj/install-gccxml/lib/python2.7/site-packages/cppproj/pybasics.so(_ZNSt4pairIiN7cppproj18SomeCrazyPairValueEED1Ev+0x1c)[0x7fffef57809c]
/home/gidden/work/xdress/tests/cppproj/install-gccxml/lib/python2.7/site-packages/cppproj/pybasics.so(_ZN7cppproj7TClass2IfED1Ev+0x2d)[0x7fffef579265]
/lib/x86_64-linux-gnu/libc.so.6(+0x3c071)[0x7ffff7831071]
/lib/x86_64-linux-gnu/libc.so.6(+0x3c0f5)[0x7ffff78310f5]
/usr/bin/python[0x4189b9]
/usr/bin/python[0x418aef]
/usr/bin/python(PyErr_PrintEx+0x1d)[0x41802a]
/usr/bin/python(PyRun_SimpleFileExFlags+0x301)[0x468ab3]
/usr/bin/python(Py_Main+0xb5e)[0x46a1e3]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf5)[0x7ffff7816de5]
/usr/bin/python[0x5735fe]