强制ctypes.cdll.LoadLibrary（）从文件中重新加载库 [英] forcing ctypes.cdll.LoadLibrary() to reload library from file

问题描述

我有以下代码

import ctypes
lib1 = ctypes.cdll.LoadLibrary("./mylib.so")
# modify mylib.so (code generation and compilation) or even delete it
lib2 = ctypes.cdll.LoadLibrary("./mylib.so")

问题是 lib2 是指原始共享库，而不是新共享库一。如果我在两次调用之间删除mylib.so，我不会出错。

The problem is that lib2 refers to the original shared library, not the new one. If I delete mylib.so between the calls I get no error.

使用 ctypes._reset_cache（）不会

我如何告诉 ctypes 实际上是从硬盘上重新加载库的？

How can I tell ctypes to actually reload the library from the hard disk?

推荐答案

我不知道如何指示 ctypes 如何卸载库（找不到< a href = https://docs.python.org/3/library/ctypes.html#module-ctypes rel = nofollow noreferrer> [Python 3]：ctypes-Python的外部函数库

I don't know how to instruct ctypes how to unload a library (didn't find a way on [Python 3]: ctypes - A foreign function library for Python, but that doesn't mean that there isn't one).

可以通过强制加载器（减少库的引用​​计数并）卸载来手动完成此操作。通过 [man7]：DLCLOSE（3P）（也阅读 [man7]：DLOPEN（3）了解更多信息加载/卸载库）。

It can be done manually, by forcing the loader to (decrement the library's reference count and) unload it via [man7]: DLCLOSE(3P) (also read [man7]: DLOPEN(3) for additional info on loading / unloading libraries).

dll.c ：

#include <stdio.h>

int func0(int arg0) {
    int alter_factor = 2;
    printf("From C - arg0: %d, alter_factor: %d\n", arg0, alter_factor);
    return arg0 * alter_factor;
}

code.py ：

#!/usr/bin/env python3

import sys
import ctypes


DLL_NAME = "./dll.so"


def handle_dll(dll_name=DLL_NAME):
    dll_dll = ctypes.CDLL(dll_name)
    func0_func = dll_dll.func0
    func0_func.argtypes = [ctypes.c_int]
    func0_func.restype = ctypes.c_int
    return dll_dll, func0_func


def main():
    dlclose_func = ctypes.CDLL(None).dlclose
    dlclose_func.argtypes = [ctypes.c_void_p]
    dlclose_func.restype = ctypes.c_int

    dll, func0 = handle_dll()
    res = func0(42)
    print(res)
    dlclose_func(dll._handle)
    input("In another terminal, modify the C code (e.g. change `alter_factor`), recompile (gcc -fPIC -shared -o dll.so dll.c), and when done press ENTER here...")
    dll, func0 = handle_dll()
    res = func0(42)
    print(res)


if __name__ == "__main__":
    print("Python {:s} on {:s}\n".format(sys.version, sys.platform))
    main()

输出：

[cfati@cfati-ubtu16x64-0:~/Work/Dev/StackOverflow/q050964033]> python3 code.py
Python 3.5.2 (default, Nov 23 2017, 16:37:01)
[GCC 5.4.0 20160609] on linux

From C - arg0: 42, alter_factor: 2
84
In another terminal, modify the C code (e.g. change `alter_factor`), recompile (gcc -fPIC -shared -o dll.so dll.c), and when done press ENTER here...
From C - arg0: 42, alter_factor: 3
126

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