我得到一个错误，当使用Cython的Clibrary

Question

在Qt Creator中，我创建了一个小库（在Python项目的“Squaring”子文件夹中）：

平方.h:

int squaring(int a);

平方.c:

#include "squaring.h"
int squaring(int a){
    return a * a;
}

在Eclipse中，我创建了一个Python项目，试图使用这个库（according to the instructions from the official website)：

cSquaring.pxd:

cdef extern from "Squaring/squaring.h":
    int squaring(int a)

函数.pix:

cimport cSquaring
cpdef int count(int value):
    return cSquaring.squaring(value)

设置.py:

from distutils.core import setup
from distutils.extension import Extension
from Cython.Build import cythonize
setup(ext_modules=cythonize([Extension("Functions", ["Functions.pyx"])]))

main.py:

from Functions import count
if __name__ == '__main__':
    data = 1
    returned = count(data)
    print(returned)

使用（无任何错误）完成了C代码的编译：

python3 setup.py build_ext -i

但当我在执行时运行main.py时，我会感到恐惧：

File “/home/denis/.p2/pool/plugins/org.python.pydev.core_7.3.0.201908161924/pysrc/pydevd.py”, line 2643, in <module>
main()
File “/home/denis/.p2/pool/plugins/org.python.pydev.core_7.3.0.201908161924/pysrc/pydevd.py”, line 2636, in main
globals = debugger.run(setup, None, None, is_module)
File “/home/denis/.p2/pool/plugins/org.python.pydev.core_7.3.0.201908161924/pysrc/pydevd.py”, line 1920, in run
return self._exec(is_module, entry_point_fn, module_name, file, globals, locals)
File “/home/denis/.p2/pool/plugins/org.python.pydev.core_7.3.0.201908161924/pysrc/pydevd.py”, line 1927, in _exec
pydev_imports.execfile(file, globals, locals) # execute the script
File “/home/denis/.p2/pool/plugins/org.python.pydev.core_7.3.0.201908161924/pysrc/_pydev_imps/_pydev_execfile.py”, line 25, in execfile
exec(compile(contents+“\n”, file, ‘exec’), glob, loc)
File “/home/denis/eclipse-workspace/ConnectionWithCPlusPlus/main.py”, line 1, in <module>
from Functions import count
ImportError: /home/denis/eclipse-workspace/ConnectionWithCPlusPlus/Functions.cpython-37m-x86_64-linux-gnu.so: undefined symbol: squaring

而另一个使用Cython的项目（在那里我没有创建C库，而是直接在Cython上编写代码）运行良好

有什么问题

Answer 1

你在Cython中包含了头文件，但是你从来没有告诉过它实现，也就是定义函数的库。您需要针对编译C源代码生成的库进行链接，如Cython docs中所述

在Functions.pyx中，必须在顶部添加这样的注释

# distutils: sources = path/to/squaring.c