Undefined symbols on Linux (but works well on OS X)

[zliucd]

Hi,

Pybind11 works well on Mac OS X but errors occurred "Undefined symbol" in Ubuntu. With ldd -r my.so, there are lots of undefined symbols, e.g.,

undefined symbol: PyExc_ValueError
undefined symbol: PyExc_IndexError
...

I used add_subdirectory( ) in CMakeLists.txt. Can you give me a hint? Thanks.