我正在使用ctypes在Python中加载DLL,这非常好。
现在我们想要能够在运行时重新加载该DLL。
直接的方法似乎是:
1. 卸载DLL
2. 加载DLL
不幸的是,我不确定卸载DLL的正确方法。
_ctypes.FreeLibrary可用,但是是私有的。
是否有其他方法可以卸载该DLL?
我正在使用ctypes在Python中加载DLL,这非常好。
现在我们想要能够在运行时重新加载该DLL。
直接的方法似乎是:
1. 卸载DLL
2. 加载DLL
不幸的是,我不确定卸载DLL的正确方法。
_ctypes.FreeLibrary可用,但是是私有的。
是否有其他方法可以卸载该DLL?
你应该能够通过处理对象来完成它
mydll = ctypes.CDLL('...')
del mydll
mydll = ctypes.CDLL('...')
编辑:Hop的评论是正确的,这解除了名称的绑定,但垃圾回收并不会那么快,事实上我甚至怀疑它甚至是否释放了加载的库。
Ctypes似乎没有提供一种清理资源的简洁方法,它只提供了一个_handle
字段来处理dlopen句柄...
所以我唯一看到的方式,是一个真正的,非常不干净的方式,即在系统依赖下关闭句柄,但这非常非常不干净,因为ctypes还在内部保留对该句柄的引用。因此,卸载需要采取以下形式:
mydll = ctypes.CDLL('./mylib.so')
handle = mydll._handle
del mydll
while isLoaded('./mylib.so'):
dlclose(handle)
它非常不干净,我只检查了它的工作情况:
def isLoaded(lib):
libp = os.path.abspath(lib)
ret = os.system("lsof -p %d | grep %s > /dev/null" % (os.getpid(), libp))
return (ret == 0)
def dlclose(handle)
libdl = ctypes.CDLL("libdl.so")
libdl.dlclose(handle)
dlclose
返回非零值,而Windows的FreeLibrary
返回零。在这种情况下,_ctypes.dlclose
和_ctypes.FreeLibrary
(注意下划线)会引发OSError
异常。 - Eryk Sun如果你正在使用iPython或类似的工作流程,能够卸载DLL是很有帮助的,这样你就可以在不必重新启动会话的情况下重建DLL。在Windows环境下,我仅尝试过与Windows DLL相关的方法。
REBUILD = True
if REBUILD:
from subprocess import call
call('g++ -c -DBUILDING_EXAMPLE_DLL test.cpp')
call('g++ -shared -o test.dll test.o -Wl,--out-implib,test.a')
import ctypes
import numpy
# Simplest way to load the DLL
mydll = ctypes.cdll.LoadLibrary('test.dll')
# Call a function in the DLL
print mydll.test(10)
# Unload the DLL so that it can be rebuilt
libHandle = mydll._handle
del mydll
ctypes.windll.kernel32.FreeLibrary(libHandle)
int
值;这将截断 64 位指针的值。你需要将句柄包装成指针,即ctypes.c_void_p(mydll._handle)
,或者声明kernel32.FreeLibrary.argtypes = (ctypes.c_void_p,)
,或者调用 _ctypes.FreeLibrary
(注意初始下划线;它是底层的 _ctypes
扩展模块)。 - Eryk Sun以下是类似讨论的概述(我从中构建了这个答案)。
这适用于Windows和Linux,因此需要提供2个编译脚本。 测试环境如下:
cpp_code.cpp
extern "C" int my_fct(int n)
{
int factor = 10;
return factor * n;
}
compile-linux.sh
#!/bin/bash
g++ cpp_code.cpp -shared -o myso.so
compile-windows.cmd
set gpp="C:\Program Files\mingw-w64\x86_64-8.1.0-posix-seh-rt_v6-rev0\mingw64\bin\g++.exe"
%gpp% cpp_code.cpp -shared -o mydll.dll
PAUSE
Python 代码
from sys import platform
import ctypes
if platform == "linux" or platform == "linux2":
# https://dev59.com/Oazka4cB1Zd3GeqP6lP1#50986803
# https://stackoverflow.com/a/52223168/7128154
dlclose_func = ctypes.cdll.LoadLibrary('').dlclose
dlclose_func.argtypes = [ctypes.c_void_p]
fn_lib = './myso.so'
ctypes_lib = ctypes.cdll.LoadLibrary(fn_lib)
handle = ctypes_lib._handle
valIn = 42
valOut = ctypes_lib.my_fct(valIn)
print(valIn, valOut)
del ctypes_lib
dlclose_func(handle)
elif platform == "win32": # Windows
# https://dev59.com/qGcs5IYBdhLWcg3wHwNH#13129176
# https://dev59.com/ZXRC5IYBdhLWcg3wROpQ
lib = ctypes.WinDLL('./mydll.dll')
libHandle = lib._handle
# do stuff with lib in the usual way
valIn = 42
valOut = lib.my_fct(valIn)
print(valIn, valOut)
del lib
ctypes.windll.kernel32.FreeLibrary(libHandle)
如果一个共享库有依赖关系,这种方法不一定适用(但也有可能适用——取决于依赖项^^)。我没有详细研究过,但看起来机制如下:库和依赖项被加载。由于依赖项没有被卸载,所以库不能被卸载。
我发现,如果我将OpenCv
(版本4.2)包含在我的共享库中,这会搞乱卸载过程。以下示例仅在linux系统上进行了测试:
code.cpp
#include <opencv2/core/core.hpp>
#include <iostream>
extern "C" int my_fct(int n)
{
cv::Mat1b mat = cv::Mat1b(10,8,(unsigned char) 1 ); // change 1 to test unloading
return mat(0,1) * n;
}
使用以下命令进行编译
g++ code.cpp -shared -fPIC -Wall -std=c++17 -I/usr/include/opencv4 -lopencv_core -o so_opencv.so
Python 代码
from sys import platform
import ctypes
class CtypesLib:
def __init__(self, fp_lib, dependencies=[]):
self._dependencies = [CtypesLib(fp_dep) for fp_dep in dependencies]
if platform == "linux" or platform == "linux2": # Linux
self._dlclose_func = ctypes.cdll.LoadLibrary('').dlclose
self._dlclose_func.argtypes = [ctypes.c_void_p]
self._ctypes_lib = ctypes.cdll.LoadLibrary(fp_lib)
elif platform == "win32": # Windows
self._ctypes_lib = ctypes.WinDLL(fp_lib)
self._handle = self._ctypes_lib._handle
def __getattr__(self, attr):
return self._ctypes_lib.__getattr__(attr)
def __del__(self):
for dep in self._dependencies:
del dep
del self._ctypes_lib
if platform == "linux" or platform == "linux2": # Linux
self._dlclose_func(self._handle)
elif platform == "win32": # Windows
ctypes.windll.kernel32.FreeLibrary(self._handle)
fp_lib = './so_opencv.so'
ctypes_lib = CtypesLib(fp_lib, ['/usr/lib64/libopencv_core.so'])
valIn = 1
ctypes_lib.my_fct.argtypes = [ctypes.c_int]
ctypes_lib.my_fct.restype = ctypes.c_int
valOut = ctypes_lib.my_fct(valIn)
print(valIn, valOut)
del ctypes_lib
如果代码示例或目前的解释有任何问题,请告诉我。如果你知道更好的方法,那就更好了!如果我们能够一劳永逸地解决这个问题,那就太棒了。
为了实现完全的跨平台兼容性:我维护了一个包含各个平台上dlclose()
等效函数以及它们所属库的列表。这是一个有些冗长的列表,但可以随意复制/粘贴。
import sys
import ctypes
import platform
OS = platform.system()
if OS == "Windows": # pragma: Windows
dll_close = ctypes.windll.kernel32.FreeLibrary
elif OS == "Darwin":
try:
try:
# macOS 11 (Big Sur). Possibly also later macOS 10s.
stdlib = ctypes.CDLL("libc.dylib")
except OSError:
stdlib = ctypes.CDLL("libSystem")
except OSError:
# Older macOSs. Not only is the name inconsistent but it's
# not even in PATH.
stdlib = ctypes.CDLL("/usr/lib/system/libsystem_c.dylib")
dll_close = stdlib.dlclose
elif OS == "Linux":
try:
stdlib = ctypes.CDLL("")
except OSError:
# Alpine Linux.
stdlib = ctypes.CDLL("libc.so")
dll_close = stdlib.dlclose
elif sys.platform == "msys":
# msys can also use `ctypes.CDLL("kernel32.dll").FreeLibrary()`. Not sure
# if or what the difference is.
stdlib = ctypes.CDLL("msys-2.0.dll")
dll_close = stdlib.dlclose
elif sys.platform == "cygwin":
stdlib = ctypes.CDLL("cygwin1.dll")
dll_close = stdlib.dlclose
elif OS == "FreeBSD":
# FreeBSD uses `/usr/lib/libc.so.7` where `7` is another version number.
# It is not in PATH but using its name instead of its path is somehow the
# only way to open it. The name must include the .so.7 suffix.
stdlib = ctypes.CDLL("libc.so.7")
dll_close = stdlib.close
else:
raise NotImplementedError("Unknown platform.")
dll_close.argtypes = [ctypes.c_void_p]
你可以使用dll_close(dll._handle)
来卸载库dll = ctypes.CDLL("your-library")
。
Piotr的回答对我很有帮助,但在64位Windows上我遇到了一个问题:
Traceback (most recent call last):
...
ctypes.ArgumentError: argument 1: <class 'OverflowError'>: int too long to convert
FreeLibrary
调用的参数类型,如此答案所建议的,解决了我的问题。import ctypes, ctypes.windll
def free_library(handle):
kernel32 = ctypes.WinDLL('kernel32', use_last_error=True)
kernel32.FreeLibrary.argtypes = [ctypes.wintypes.HMODULE]
kernel32.FreeLibrary(handle)
使用方法:
lib = ctypes.CDLL("foobar.dll")
free_library(lib._handle)