I don't think there's anything wrong with the setup we've been looking at so far, per se. The libpython2.7.a file produced has the 'round' function like it should:

> nm libpython2.7.a | grep round
[116] |      1360|     696|FUNC |GLOB |0    |2      |_Py_double_round
[218] |         0|       0|NOTY |GLOB |0    |UNDEF  |_Py_double_round
[10] |     15268|     236|FUNC |LOCL |0    |2      |builtin_round
[48] |      9912|     198|OBJT |LOCL |0    |4      |round_doc
[8] |         0|      96|FUNC |GLOB |0    |2      |round

However, the python executable itself, compiled against that archive, does *not* have it:

> nm python | grep round
[4805] |    244408|     696|FUNC |GLOB |0    |9      |_Py_double_round
[1735] |    640836|     236|FUNC |LOCL |0    |9      |builtin_round
[1770] |   1533576|     198|OBJT |LOCL |0    |16     |round_doc

So, for some reason, the gcc command that builds that python executable is leaving it out:

gcc -o python \
       Modules/python.o \
       libpython2.7.a -lresolv -lsocket -lnsl -lrt -ldl -lpthread -lm

Just an update. Going to try to debug that command and see if I can find out why.