我是一个Python的新手，想通过在http://blog.perrygeo.net/2008/04/19/a-quick-cython-introduction/找到的简单示例来尝试使用Cython。
Cython文件名为c1.pyx。
然后运行cython c1.pyx，一切都很好。
然后运行gcc -c -fPIC -I/usr/include/python2.7/ c1.c，也很正常。
但是运行gcc -shared c1.o -o c1.so时出了问题。
有人能解释一下这个错误吗？
以下是错误消息：
Undefined symbols for architecture x86_64:
"_PyCFunction_NewEx", referenced from:
_initc1 in cc5xSgOI.o
"_PyCode_New", referenced from:
___Pyx_AddTraceback in cc5xSgOI.o
_initc1 in cc5xSgOI.o
"_PyDict_GetItem", referenced from:
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
"_PyDict_New", referenced from:
_initc1 in cc5xSgOI.o
"_PyDict_Next", referenced from:
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
"_PyDict_Size", referenced from:
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
"_PyErr_Clear", referenced from:
___Pyx_GetName in cc5xSgOI.o
"_PyErr_Format", referenced from:
___Pyx_RaiseArgtupleInvalid.constprop.5 in cc5xSgOI.o
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
"_PyErr_Occurred", referenced from:
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
_initc1 in cc5xSgOI.o
"_PyErr_SetObject", referenced from:
___Pyx_GetName in cc5xSgOI.o
"_PyErr_SetString", referenced from:
_initc1 in cc5xSgOI.o
"_PyErr_WarnEx", referenced from:
_initc1 in cc5xSgOI.o
"_PyExc_ImportError", referenced from:
_initc1 in cc5xSgOI.o
"_PyExc_NameError", referenced from:
___Pyx_GetName in cc5xSgOI.o
"_PyExc_TypeError", referenced from:
___Pyx_RaiseArgtupleInvalid.constprop.5 in cc5xSgOI.o
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
"_PyFloat_AsDouble", referenced from:
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
"_PyFloat_FromDouble", referenced from:
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
"_PyFloat_Type", referenced from:
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
"_PyFrame_New", referenced from:
___Pyx_AddTraceback in cc5xSgOI.o
"_PyImport_AddModule", referenced from:
_initc1 in cc5xSgOI.o
"_PyInt_FromLong", referenced from:
_initc1 in cc5xSgOI.o
"_PyList_New", referenced from:
_initc1 in cc5xSgOI.o
"_PyMem_Malloc", referenced from:
___Pyx_AddTraceback in cc5xSgOI.o
"_PyMem_Realloc", referenced from:
___Pyx_AddTraceback in cc5xSgOI.o
"_PyModule_GetDict", referenced from:
___Pyx_AddTraceback in cc5xSgOI.o
_initc1 in cc5xSgOI.o
"_PyNumber_Add", referenced from:
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
"_PyNumber_Multiply", referenced from:
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
"_PyOS_snprintf", referenced from:
_initc1 in cc5xSgOI.o
"_PyObject_Call", referenced from:
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
"_PyObject_CallFunctionObjArgs", referenced from:
_initc1 in cc5xSgOI.o
"_PyObject_GetAttr", referenced from:
___Pyx_GetName in cc5xSgOI.o
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
"_PyObject_GetAttrString", referenced from:
_initc1 in cc5xSgOI.o
"_PyObject_SetAttr", referenced from:
_initc1 in cc5xSgOI.o
"_PyObject_SetAttrString", referenced from:
_initc1 in cc5xSgOI.o
"_PyString_AsString", referenced from:
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
"_PyString_FromFormat", referenced from:
___Pyx_AddTraceback in cc5xSgOI.o
"_PyString_FromString", referenced from:
___Pyx_AddTraceback in cc5xSgOI.o
"_PyString_FromStringAndSize", referenced from:
_initc1 in cc5xSgOI.o
"_PyString_InternFromString", referenced from:
_initc1 in cc5xSgOI.o
"_PyString_Type", referenced from:
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
"_PyTraceBack_Here", referenced from:
___Pyx_AddTraceback in cc5xSgOI.o
"_PyTuple_New", referenced from:
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
_initc1 in cc5xSgOI.o
"_PyUnicodeUCS2_DecodeUTF8", referenced from:
_initc1 in cc5xSgOI.o
"_Py_GetVersion", referenced from:
_initc1 in cc5xSgOI.o
"_Py_InitModule4_64", referenced from:
_initc1 in cc5xSgOI.o
"__PyString_Eq", referenced from:
___pyx_pw_2c1_1great_circle in cc5xSgOI.o
"__PyThreadState_Current", referenced from:
___Pyx_AddTraceback in cc5xSgOI.o
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status