問題描述

我嘗試通過C語言編寫一個Python的模塊，但是我的C程序本身又依賴于一個第三方的庫（libwiringPi.so），當(dāng)我在Python源程序中import我生成的庫時，會提示函數(shù)未定義，這些函數(shù)都是那個第三方庫里的，我應(yīng)該怎樣編譯才能讓我編譯出的模塊可以動態(tài)鏈接那個庫？

我也嘗試過使用gcc手動編譯動態(tài)鏈接庫，然后用ctyes，但是報一樣的錯誤；生成模塊的C代碼和setup.py代碼都是基于Python源碼包中的demo程序。

我的C程序代碼

/* Example of embedding Python in another program */#include 'python2.7/Python.h'#include <wiringPi.h>void initdht11(void); /* Forward */int main(int argc, char **argv){ /* Initialize the Python interpreter. Required. */ Py_Initialize(); /* Add a static module */ initdht11(); /* Exit, cleaning up the interpreter */ Py_Exit(0); return 0;}/* A static module *//* ’self’ is not used */static PyObject *dht11_foo(PyObject *self, PyObject* args){ wiringPiSetup(); return PyInt_FromLong(42L);}static PyMethodDef dht11_methods[] = { {'foo', dht11_foo, METH_NOARGS, 'Return the meaning of everything.'}, {NULL, NULL} /* sentinel */};voidinitdht11(void){ PyImport_AddModule('dht11'); Py_InitModule('dht11', dht11_methods);}

setup.py

from distutils.core import setup, Extensiondht11module = Extension(’dht11’, library_dirs = [’/usr/lib’], include_dirs = [’/usr/include’], sources = [’math.c’])setup (name = ’dht11’, version = ’1.0’, description = ’This is a demo package’, author = ’Martin v. Loewis’, author_email = ’martin@v.loewis.de’, url = ’https://docs.python.org/extending/building’, long_description = ’’’This is really just a demo package.’’’, ext_modules = [dht11module])

錯誤信息

Traceback (most recent call last): File 'test.py', line 1, in <module> import dht11ImportError: /usr/local/lib/python2.7/dist-packages/dht11.so: undefined symbol: wiringPiSetup

問題解答

哎，早上醒來突然想到，趕緊試了一下。

出現(xiàn)這個問題是因為在編譯的時候需要加 -lwiringPi 選項來引用這個庫，但是我仔細(xì)看了以下執(zhí)行 python setup.py build 之后執(zhí)行的編譯命令，根本就沒有加這個選項，解決方式很簡單，只需要修改一下setup.py，在Extension里面加上 libraries = [’wiringPi’] 這個參數(shù)就行了，修改后的setup.py變成如下樣子

from distutils.core import setup, Extensiondht11module = Extension(’dht11’, library_dirs = [’/usr/lib’], #指定庫的目錄 include_dirs = [’/usr/include’], #制定頭文件的目錄 libraries = [’wiringPi’], #指定庫的名稱 sources = [’math.c’])setup (name = ’dht11’, version = ’1.0’, description = ’This is a demo package’, author = ’Martin v. Loewis’, author_email = ’martin@v.loewis.de’, url = ’https://docs.python.org/extending/building’, long_description = ’’’This is really just a demo package.’’’, ext_modules = [dht11module])