为什么在Python上正确导入我的C dll而不是我的C++；动态链接库？

操作系统：Windows 10 64位

Python:3.9.5 64位

编译器：gcc版本8.1.0（x86_64-posix-seh-rev0，由MinGW-W64项目构建）

问题：我对Python不太了解，我尝试导入一些非常基本的DLL来开始。我不明白为什么在我的计算机上找到了一个C DLL，而找不到C++ DLL。 C代码（mini.C）：

#include <stdio.h>

extern "C" {

        __declspec( dllexport ) void hi() {

                printf("\nHello World from C !\n");

        }

}

#include <iostream>

extern "C" {

        __declspec(dllexport) void hi() {

                std::cout << std::endl << "Hello World from C++ !" << std::endl;

        }

}

all: mini.dll mini_cpp.dll

mini.dll: mini.o

        g++ mini.o -shared -Wl,--out-implib,libmini.a -o mini.dll

mini.o: mini.c

        g++ -c mini.c -I . -o mini.o

mini_cpp.dll: mini_cpp.o

        g++ mini_cpp.o -shared -Wl,--out-implib,libmini_cpp.a -o mini_cpp.dll

mini_cpp.o: mini_cpp.cpp

        g++ -c mini_cpp.cpp -I . -o mini_cpp.o


g++ -c mini.c -I . -o mini.o

g++ mini.o -shared -Wl,--out-implib,libmini.a -o mini.dll

g++ -c mini_cpp.cpp -I . -o mini_cpp.o

g++ mini_cpp.o -shared -Wl,--out-implib,libmini_cpp.a -o mini_cpp.dll

Python 3.9.5 (tags/v3.9.5:0a7dcbd, May  3 2021, 17:27:52) [MSC v.1928 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>>
>>> import ctypes
>>>
>>> from ctypes import *
>>>
>>> my_lib = windll.LoadLibrary( os.path.abspath( "mini.dll") )
>>>
>>> my_func = my_lib.hi
>>>
>>> my_func.restype = c_char_p
>>>
>>> my_func()

Hello World from C !

>>> my_cpp_lib = windll.LoadLibrary( os.path.abspath( "mini_cpp.dll") )

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\AGENT_TI\AppData\Local\Programs\Python\Python39\lib\ctypes\__init__.py", line 452, in LoadLibrary
return self._dlltype(name)
  File "C:\Users\AGENT_TI\AppData\Local\Programs\Python\Python39\lib\ctypes\__init__.py", line 374, in __init__
self._handle = _dlopen(self._name, mode)
FileNotFoundError: Could not find module 'C:\Users\AGENT_TI\Desktop\STRINGS\python\mini_cpp.dll' (or one of its dependencies). Try using the full path with constructor syntax.
>>>    

>>> import os
>>>
>>> import ctypes
>>>
>>> from ctypes import *
>>>
>>> my_lib = windll.LoadLibrary( os.path.abspath( "mini.dll") )
>>>
>>> my_func = my_lib.hi
>>>
>>> my_func.restype = c_char_p
>>>
>>> my_func()

Hello World from C !
>>>
>>> windll.LoadLibrary("C:\\mingw-w64\\x86_64-8.1.0-posix-seh-rt_v6-rev0\\mingw64\\x86_64-w64-mingw32\\lib\\libstdc++-6.dll")
<WinDLL 'C:\mingw-w64\x86_64-8.1.0-posix-seh-rt_v6-rev0\mingw64\x86_64-w64-mingw32\lib\libstdc++-6.dll', handle 6fc40000 at 0x25a1f2ade50>
>>>
>>> my_cpp_lib = windll.LoadLibrary( os.path.abspath( "mini_cpp.dll") )
>>>
>>> my_cpp_func = my_cpp_lib.hi
>>>
>>> my_cpp_func.restype = c_wchar_p
>>>
>>> my_cpp_func()

Hello World from C++ !
'\uf038濑'
>>>

C DLL的Python代码和结果：

#include <stdio.h>

extern "C" {

        __declspec( dllexport ) void hi() {

                printf("\nHello World from C !\n");

        }

}

#include <iostream>

extern "C" {

        __declspec(dllexport) void hi() {

                std::cout << std::endl << "Hello World from C++ !" << std::endl;

        }

}

all: mini.dll mini_cpp.dll

mini.dll: mini.o

        g++ mini.o -shared -Wl,--out-implib,libmini.a -o mini.dll

mini.o: mini.c

        g++ -c mini.c -I . -o mini.o

mini_cpp.dll: mini_cpp.o

        g++ mini_cpp.o -shared -Wl,--out-implib,libmini_cpp.a -o mini_cpp.dll

mini_cpp.o: mini_cpp.cpp

        g++ -c mini_cpp.cpp -I . -o mini_cpp.o


g++ -c mini.c -I . -o mini.o

g++ mini.o -shared -Wl,--out-implib,libmini.a -o mini.dll

g++ -c mini_cpp.cpp -I . -o mini_cpp.o

g++ mini_cpp.o -shared -Wl,--out-implib,libmini_cpp.a -o mini_cpp.dll

Python 3.9.5 (tags/v3.9.5:0a7dcbd, May  3 2021, 17:27:52) [MSC v.1928 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>>
>>> import ctypes
>>>
>>> from ctypes import *
>>>
>>> my_lib = windll.LoadLibrary( os.path.abspath( "mini.dll") )
>>>
>>> my_func = my_lib.hi
>>>
>>> my_func.restype = c_char_p
>>>
>>> my_func()

Hello World from C !

>>> my_cpp_lib = windll.LoadLibrary( os.path.abspath( "mini_cpp.dll") )

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\AGENT_TI\AppData\Local\Programs\Python\Python39\lib\ctypes\__init__.py", line 452, in LoadLibrary
return self._dlltype(name)
  File "C:\Users\AGENT_TI\AppData\Local\Programs\Python\Python39\lib\ctypes\__init__.py", line 374, in __init__
self._handle = _dlopen(self._name, mode)
FileNotFoundError: Could not find module 'C:\Users\AGENT_TI\Desktop\STRINGS\python\mini_cpp.dll' (or one of its dependencies). Try using the full path with constructor syntax.
>>>    

>>> import os
>>>
>>> import ctypes
>>>
>>> from ctypes import *
>>>
>>> my_lib = windll.LoadLibrary( os.path.abspath( "mini.dll") )
>>>
>>> my_func = my_lib.hi
>>>
>>> my_func.restype = c_char_p
>>>
>>> my_func()

Hello World from C !
>>>
>>> windll.LoadLibrary("C:\\mingw-w64\\x86_64-8.1.0-posix-seh-rt_v6-rev0\\mingw64\\x86_64-w64-mingw32\\lib\\libstdc++-6.dll")
<WinDLL 'C:\mingw-w64\x86_64-8.1.0-posix-seh-rt_v6-rev0\mingw64\x86_64-w64-mingw32\lib\libstdc++-6.dll', handle 6fc40000 at 0x25a1f2ade50>
>>>
>>> my_cpp_lib = windll.LoadLibrary( os.path.abspath( "mini_cpp.dll") )
>>>
>>> my_cpp_func = my_cpp_lib.hi
>>>
>>> my_cpp_func.restype = c_wchar_p
>>>
>>> my_cpp_func()

Hello World from C++ !
'\uf038濑'
>>>

强> Python代码和C++ DLL的结果：>/P>

#include <stdio.h>

extern "C" {

        __declspec( dllexport ) void hi() {

                printf("\nHello World from C !\n");

        }

}

#include <iostream>

extern "C" {

        __declspec(dllexport) void hi() {

                std::cout << std::endl << "Hello World from C++ !" << std::endl;

        }

}

all: mini.dll mini_cpp.dll

mini.dll: mini.o

        g++ mini.o -shared -Wl,--out-implib,libmini.a -o mini.dll

mini.o: mini.c

        g++ -c mini.c -I . -o mini.o

mini_cpp.dll: mini_cpp.o

        g++ mini_cpp.o -shared -Wl,--out-implib,libmini_cpp.a -o mini_cpp.dll

mini_cpp.o: mini_cpp.cpp

        g++ -c mini_cpp.cpp -I . -o mini_cpp.o


g++ -c mini.c -I . -o mini.o

g++ mini.o -shared -Wl,--out-implib,libmini.a -o mini.dll

g++ -c mini_cpp.cpp -I . -o mini_cpp.o

g++ mini_cpp.o -shared -Wl,--out-implib,libmini_cpp.a -o mini_cpp.dll

Python 3.9.5 (tags/v3.9.5:0a7dcbd, May  3 2021, 17:27:52) [MSC v.1928 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>>
>>> import ctypes
>>>
>>> from ctypes import *
>>>
>>> my_lib = windll.LoadLibrary( os.path.abspath( "mini.dll") )
>>>
>>> my_func = my_lib.hi
>>>
>>> my_func.restype = c_char_p
>>>
>>> my_func()

Hello World from C !

>>> my_cpp_lib = windll.LoadLibrary( os.path.abspath( "mini_cpp.dll") )

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\AGENT_TI\AppData\Local\Programs\Python\Python39\lib\ctypes\__init__.py", line 452, in LoadLibrary
return self._dlltype(name)
  File "C:\Users\AGENT_TI\AppData\Local\Programs\Python\Python39\lib\ctypes\__init__.py", line 374, in __init__
self._handle = _dlopen(self._name, mode)
FileNotFoundError: Could not find module 'C:\Users\AGENT_TI\Desktop\STRINGS\python\mini_cpp.dll' (or one of its dependencies). Try using the full path with constructor syntax.
>>>    

>>> import os
>>>
>>> import ctypes
>>>
>>> from ctypes import *
>>>
>>> my_lib = windll.LoadLibrary( os.path.abspath( "mini.dll") )
>>>
>>> my_func = my_lib.hi
>>>
>>> my_func.restype = c_char_p
>>>
>>> my_func()

Hello World from C !
>>>
>>> windll.LoadLibrary("C:\\mingw-w64\\x86_64-8.1.0-posix-seh-rt_v6-rev0\\mingw64\\x86_64-w64-mingw32\\lib\\libstdc++-6.dll")
<WinDLL 'C:\mingw-w64\x86_64-8.1.0-posix-seh-rt_v6-rev0\mingw64\x86_64-w64-mingw32\lib\libstdc++-6.dll', handle 6fc40000 at 0x25a1f2ade50>
>>>
>>> my_cpp_lib = windll.LoadLibrary( os.path.abspath( "mini_cpp.dll") )
>>>
>>> my_cpp_func = my_cpp_lib.hi
>>>
>>> my_cpp_func.restype = c_wchar_p
>>>
>>> my_cpp_func()

Hello World from C++ !
'\uf038濑'
>>>

my_cpp_lib=windell.LoadLibrary（os.path.abspath（“mini_cpp.dll”）） 回溯（最近一次呼叫最后一次）： 文件“”，第1行，在 LoadLibrary中第452行的文件“C:\Users\AGENT\u TI\AppData\Local\Programs\Python\Python39\lib\ctypes\\uuuuuu init\uuuuu.py” 返回自我类型（名称） 文件“C:\Users\AGENT\u TI\AppData\Local\Programs\Python39\lib\ctypes\\uuuuuu init\uuuuu.py”，第374行，在\uuu init中__ self.\u handle=\u dlopen（self.\u名称，模式） FileNotFoundError:找不到模块“C:\Users\AGENT\TI\Desktop\STRINGS\python\mini\u cpp.dll”（或其依赖项之一）。尝试使用构造函数语法的完整路径。 >>> ~
~
我已经尝试过的：

• Python中的不同os.path操作：

chdir（“C:\Users\AGENT\u TI\Desktop\STRINGS\python”）

添加dll目录（“C:\Users\AGENT\u TI\Desktop\STRINGS\python”）

• 用GCC编译而不是G++（加上-+LSTDC++ + C++代码）

---

如果有人已经遇到了这个问题并进行了一些修复，谢谢…

Paxdiablo：您对dll问题的假设是正确的（我100%同意消息的准确性不足导致如此浪费时间）

objdump向我展示了mini_cpp.dll的以下内容：

DLL Name: libstdc++-6.dll
vma:  Hint/Ord Member-Name Bound-To
9588     1739  _ZNSolsEPFRSoS_E
959c     4448  _ZNSt8ios_base4InitC1Ev
95b8     4450  _ZNSt8ios_base4InitD1Ev
95d4     4738  _ZSt4cout
95e0     4739  _ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_
9620     4847  _ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc

CristiFati：我没有尝试静态构建dll，但我想它确实可以工作

顺便说一下，根据您的直觉（事实上-lstdlibc++最终是我的两个dll之间的唯一区别），我只是在dll之前用Python加载了库 结果是好的（尽管我的字符串下有虚假字符，但我想稍后可以在Python中修复）。它解释了为什么尝试使用boost:：python或 pythonapi也导致了同样的问题

修改的Python代码和结果：

#include <stdio.h>

extern "C" {

        __declspec( dllexport ) void hi() {

                printf("\nHello World from C !\n");

        }

}

#include <iostream>

extern "C" {

        __declspec(dllexport) void hi() {

                std::cout << std::endl << "Hello World from C++ !" << std::endl;

        }

}

all: mini.dll mini_cpp.dll

mini.dll: mini.o

        g++ mini.o -shared -Wl,--out-implib,libmini.a -o mini.dll

mini.o: mini.c

        g++ -c mini.c -I . -o mini.o

mini_cpp.dll: mini_cpp.o

        g++ mini_cpp.o -shared -Wl,--out-implib,libmini_cpp.a -o mini_cpp.dll

mini_cpp.o: mini_cpp.cpp

        g++ -c mini_cpp.cpp -I . -o mini_cpp.o


g++ -c mini.c -I . -o mini.o

g++ mini.o -shared -Wl,--out-implib,libmini.a -o mini.dll

g++ -c mini_cpp.cpp -I . -o mini_cpp.o

g++ mini_cpp.o -shared -Wl,--out-implib,libmini_cpp.a -o mini_cpp.dll

Python 3.9.5 (tags/v3.9.5:0a7dcbd, May  3 2021, 17:27:52) [MSC v.1928 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>>
>>> import ctypes
>>>
>>> from ctypes import *
>>>
>>> my_lib = windll.LoadLibrary( os.path.abspath( "mini.dll") )
>>>
>>> my_func = my_lib.hi
>>>
>>> my_func.restype = c_char_p
>>>
>>> my_func()

Hello World from C !

>>> my_cpp_lib = windll.LoadLibrary( os.path.abspath( "mini_cpp.dll") )

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\AGENT_TI\AppData\Local\Programs\Python\Python39\lib\ctypes\__init__.py", line 452, in LoadLibrary
return self._dlltype(name)
  File "C:\Users\AGENT_TI\AppData\Local\Programs\Python\Python39\lib\ctypes\__init__.py", line 374, in __init__
self._handle = _dlopen(self._name, mode)
FileNotFoundError: Could not find module 'C:\Users\AGENT_TI\Desktop\STRINGS\python\mini_cpp.dll' (or one of its dependencies). Try using the full path with constructor syntax.
>>>    

>>> import os
>>>
>>> import ctypes
>>>
>>> from ctypes import *
>>>
>>> my_lib = windll.LoadLibrary( os.path.abspath( "mini.dll") )
>>>
>>> my_func = my_lib.hi
>>>
>>> my_func.restype = c_char_p
>>>
>>> my_func()

Hello World from C !
>>>
>>> windll.LoadLibrary("C:\\mingw-w64\\x86_64-8.1.0-posix-seh-rt_v6-rev0\\mingw64\\x86_64-w64-mingw32\\lib\\libstdc++-6.dll")
<WinDLL 'C:\mingw-w64\x86_64-8.1.0-posix-seh-rt_v6-rev0\mingw64\x86_64-w64-mingw32\lib\libstdc++-6.dll', handle 6fc40000 at 0x25a1f2ade50>
>>>
>>> my_cpp_lib = windll.LoadLibrary( os.path.abspath( "mini_cpp.dll") )
>>>
>>> my_cpp_func = my_cpp_lib.hi
>>>
>>> my_cpp_func.restype = c_wchar_p
>>>
>>> my_cpp_func()

Hello World from C++ !
'\uf038濑'
>>>

导入操作系统 >>> >>>导入ctypes >>> >>>从ctypes导入* >>> >>>my_lib=windell.LoadLibrary（os.path.abspath（“mini.dll”）） >>> >>>my_func=my_lib.hi >>> >>>my_func.restype=c_char\p >>> >>>my_func（） 你好，来自C的世界！ >>> >>>LoadLibrary（“C:\\mingw-w64\\x86\U 64-8.1.0-posix-seh-rt\U v6-rev0\\mingw64\\x86\U 64-w64-mingw32\\lib\\libstdc++-6.dll”） >>> >>>my_cpp_lib=windell.LoadLibrary（os.path.abspath（“mini_cpp.dll”）） >>> >>>my_cpp_func=my_cpp_lib.hi >>> >>>my_cpp_func.restype=c_wchar\u p >>> >>>my_cpp_func（） 从C++世界问好！ '\uf038濑' >>>

---

感谢您的帮助paxdiablo和CristiFati:-）

“或其依赖项之一”-这在这里可能很重要：-）加载程序很难将“罪魁祸首是XYZY.dll”这样的消息推到标准错误中，这让我很恼火。建议您找到依赖项查询工具，并调查找不到哪个特定的库/对象。如果使用-static libstdc++？旁注（没有任何函数含义）构建.dll，则会发生什么情况？不要设置返回void的函数的restype（或者如果您希望显式地将其设置为None）。另外，我认为G++产生了CCDL函数（在这种情况下，应该使用CDLL代替WEDLL），但是这只与32位有关。此外，我不知道为什么RO静态C++ LIB“不可测试”。