Calling C++ from python

Question

I'm trying to call C++ from Python.

import ctypes

clibrary = ctypes.WinDLL("C:/Users/Desktop/SOURCE/build/libmy_library.dll")

my_library.hello_world()

I am most certainly sure that my_library.dll path is exactly correct. But I still get this error:

self._handle = _dlopen(self._name, mode)
FileNotFoundError: Could not find module 'C:\Users\Desktop\SOURCE\build\libmy_library.dll' (or one of its dependencies). Try using the full path with constructor syntax.

What is wrong here?

Note: If it matters my cmake is "Unix Makefiles". And I don't use visual studio, I use VS code.

Edit: Dependency Walker Error: At least one required implicit or forwarded dependency was not found. Error: At least one module has an unresolved import due to a missing export function in an implicitly dependent module. Error: Modules with different CPU types were found. Error: A circular dependency was detected. Warning: At least one delay-load dependency module was not found. Warning: At least one module has an unresolved import due to a missing export function in a delay-load dependent module.

EDIT This really fixed it:

dll_name = "C:/Users/Desktop/SOURCE/build/libmy_library.dll"
dll_handle = win32api.LoadLibraryEx(dll_name, 0, win32con.LOAD_WITH_ALTERED_SEARCH_PATH)
my_lib = ctypes.WinDLL(dll_name, handle=dll_handle)

My rusty crystal ball says that your libstdc++ is not in the PATH. Try opening your library with the dependency walker. — n. m. could be an AI, Jan 16 '23 at 09:38
There are a lot of dependencies as I see. I cannot add them manually @n.m. — merovingian, Jan 16 '23 at 09:54
Are you using Visual C++ or g++ or something else to build the DLL? Since you are importing ctypes, you should be using ctypes.CDLL to load the DLL. — cup, Jan 16 '23 at 10:00
So it looks like your library is broken and cannot be loaded. Normally the depwalker paints dependencies with errors red, you may want to look at those. — n. m. could be an AI, Jan 16 '23 at 10:04
Paste that in your ticket instead of a comment - it is a lot easier to read from the ticket. — cup, Jan 16 '23 at 10:05
It can be broken in many subtle ways. A big unpleasant surprise here. — n. m. could be an AI, Jan 16 '23 at 10:10
It is not really different from any other OS in this regard. If anything, it is harder to produce a broken DLL on windows (but still entirely possible). Have you looked at red dependencies? — n. m. could be an AI, Jan 16 '23 at 10:13
There are at least 100 `The system cannot find the file specified (2)` errors. So I don't know what to do. It cannot be that broken imo. You were saying something about I should include libstdc++ is not in my path? @n.m. — merovingian, Jan 16 '23 at 10:17
Your issue looks similar to this: https://stackoverflow.com/questions/34206957/issues-using-ctypes-windll — nielsen, Jan 16 '23 at 10:19
Thanks. It solved my problem. But I'm surprised. Because according to the dependency walker my dll was broken and it was crying as if it couldn't find anything but kernel32 — merovingian, Jan 16 '23 at 10:30
maybe try adding this before - `import os; os.add_dll_directory(""C:/Users/Desktop/SOURCE/build")` — therealanshuman, Jan 18 '23 at 19:59

Calling C++ from python

0 Answers0