在Windows上将Cython扩展链接到C库时出现“无法解析的外部符号”错误

我正在学习Cython，并尝试运行一个简单的示例，在这里：使C库可调用。

我使用VS 2019创建mylib.lib和setup.py构建Cython扩展（有关详细信息和代码，请参见下文），但是链接器失败并出现错误：

错误LNK2001：无法解析的外部符号

但是，当我nm mylib.lib在其他帖子中找到自己的跑步时，可以看到该符号_hello存在：

D:\Codes\git_folders\my_repository\Cython_test\lib>nm mylib.lib
...
Debug/examples.obj:
...
00000000 T _hello
...

怎么了？

码：

pyexamples.pyx

cdef extern from "examples.h":
    void hello(const char *name)

def py_hello(name: bytes) -> None:
    hello(name)

setup.py

from distutils.core import setup
from distutils.extension import Extension
from Cython.Build import cythonize

examples_extension = Extension(
    name="pyexamples",
    sources=["pyexamples.pyx"],
    libraries=["mylib"],
    library_dirs=["lib"],
    include_dirs=["lib"]
)
setup(
    name="pyexamples",
    ext_modules=cythonize([examples_extension])
)

examples.c

#include <stdio.h>
#include "examples.h"

void hello(const char *name) {
    printf("hello %s\n", name);
}

examples.h

#ifndef EXAMPLES_H
#define EXAMPLES_H

void hello(const char *name);

#endif

但是，如果我运行此命令， python setup.py build_ext --inplace

我得到这个错误。

running build_ext
building 'pyexamples' extension
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\bin\HostX86\x64\cl.exe /c /nologo /Ox /W3 /GL /DNDEBUG /MD -Ilib -IC:\Users\swsyo\anaconda3\include -IC:\Users\swsyo\anaconda3\include "-IC:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\ATLMFC\include" "-IC:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\ucrt" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\shared" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\um" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\winrt" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\cppwinrt" /Tcpyexamples.c /Fobuild\temp.win-amd64-3.7\Release\pyexamples.obj
pyexamples.c
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\bin\HostX86\x64\link.exe /nologo /INCREMENTAL:NO /LTCG /DLL /MANIFEST:EMBED,ID=2 /MANIFESTUAC:NO /LIBPATH:lib /LIBPATH:C:\Users\swsyo\anaconda3\libs /LIBPATH:C:\Users\swsyo\anaconda3\PCbuild\amd64 "/LIBPATH:C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\ATLMFC\lib\x64" "/LIBPATH:C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\lib\x64" "/LIBPATH:C:\Program Files (x86)\Windows Kits\10\lib\10.0.18362.0\ucrt\x64" "/LIBPATH:C:\Program Files (x86)\Windows Kits\10\lib\10.0.18362.0\um\x64" mylib.lib /EXPORT:PyInit_pyexamples build\temp.win-amd64-3.7\Release\pyexamples.obj /OUT:D:\git_folders\my_repository\Cython_test\pyexamples.cp37-win_amd64.pyd /IMPLIB:build\temp.win-amd64-3.7\Release\pyexamples.cp37-win_amd64.lib
   Creating library build\temp.win-amd64-3.7\Release\pyexamples.cp37-win_amd64.lib and object build\temp.win-amd64-3.7\Release\pyexamples.cp37-win_amd64.exp
pyexamples.obj : error LNK2001: unresolved external symbol hello
D:\git_folders\my_repository\Cython_test\pyexamples.cp37-win_amd64.pyd : fatal error LNK1120: 1 unresolved externals
error: command 'C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\Community\\VC\\Tools\\MSVC\\14.27.29110\\bin\\HostX86\\x64\\link.exe' failed with exit status 1120

更多细节：

基于以下注释，我运行dumpbin mylib.lib命令以查看hello函数是否在库中。这是正确的方法吗？我hello在此摘要中看不到该名称。

D:\Codes\git_folders\my_repository\Cython_test\lib>dumpbin mylib.lib
Microsoft (R) COFF/PE Dumper Version 14.27.29111.0
Copyright (C) Microsoft Corporation.  All rights reserved.


Dump of file mylib.lib

File Type: LIBRARY

  Summary

          E8 .chks64
         C94 .debug$S
          C8 .debug$T
         10A .drectve
           5 .msvcjmc
           A .rdata
           8 .rtc$IMZ
           8 .rtc$TMZ
         1B4 .text$mn

我还跑nm mylib.lib了我在其他帖子中找到的。您可以_hello在摘要末尾看到。

D:\Codes\git_folders\my_repository\Cython_test\lib>nm mylib.lib

Debug\mylib.obj:
00000000 N .chks64
00000000 N .debug$S
00000000 N .debug$S
00000000 N .debug$S
00000000 N .debug$T
00000000 i .drectve
00000000 d .msvcjmc
00000000 r .rtc$IMZ
00000000 r .rtc$TMZ
00000000 t .text$mn
00000000 t .text$mn
         U @__CheckForDebuggerJustMyCode@4
010471b7 a @comp.id
80000391 a @feat.00
00000000 d __87B4E6C0_mylib@c
00000000 T __JustMyCode_Default
         U __RTC_CheckEsp
         U __RTC_InitBase
00000000 r __RTC_InitBase.rtc$IMZ
         U __RTC_Shutdown
00000000 r __RTC_Shutdown.rtc$TMZ
00000000 T _fnmylib

Debug/examples.obj:
00000000 N .chks64
00000000 N .debug$S
00000000 N .debug$S
00000000 N .debug$S
00000000 N .debug$S
00000000 N .debug$S
00000000 N .debug$S
00000000 N .debug$T
00000000 i .drectve
00000000 d .msvcjmc
00000000 r .rdata
00000000 r .rtc$IMZ
00000000 r .rtc$TMZ
00000000 t .text$mn
00000000 t .text$mn
00000000 t .text$mn
00000000 t .text$mn
00000000 t .text$mn
00000000 R ??_C@_09DEHHIH@hello?5?$CFs?6@
00000008 C ?_OptionsStorage@?1??__local_stdio_printf_options@@9@9
         U @__CheckForDebuggerJustMyCode@4
010471b7 a @comp.id
80000391 a @feat.00
00000000 T ___local_stdio_printf_options
00000001 d __101834BA_corecrt_wstdio@h
00000003 d __2F33A99E_examples@c
00000002 d __AD6A91B7_stdio@h
00000000 d __F66CEB67_corecrt_stdio_config@h
         U __imp____acrt_iob_func
         U __imp____stdio_common_vfprintf
00000000 T __JustMyCode_Default
         U __RTC_CheckEsp
         U __RTC_InitBase
00000000 r __RTC_InitBase.rtc$IMZ
         U __RTC_Shutdown
00000000 r __RTC_Shutdown.rtc$TMZ
00000000 T __vfprintf_l
00000000 T _hello
00000000 T _printf

在为x64系统重建项目后（必须在Build> Configuration Manager中将“活动解决方案平台”更改为x64），这是的结果dumpbin /symbols mylib.lib。我可以hello在摘要中看到该功能。