Python include warnings ======================= Very often compile warnings of Python can be seen, something like :: /usr/local/install/python-2.7.5/include/python2.7/pyconfig.h:1173:0: warning: "_POSIX_C_SOURCE" redefined [enabled by default] #define _POSIX_C_SOURCE 200112L ^ In file included from /usr/local/install/gcc-4.8.1/include/c++/4.8.1/x86_64-unknown-linux-gnu/bits/os_defines.h:39:0, ...... /usr/include/features.h:162:0: note: this is the location of the previous definition # define _POSIX_C_SOURCE 200809L ... #define _XOPEN_SOURCE 600 It is due to the fact that Python.h must be included before some other headers (cf python documentation). Solutions: #. include first some triqs library, like arrays.hpp, gfs.hpp, etc... #. include first that conditionally includes python if python is to be supported. (used by all triqs libs, hence the first point).