python - 强制 ctypes.cdll.LoadLibrary() 从文件重新加载库

Question

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 指的是原始共享库，而不是新共享库。如果我在调用之间删除 mylib.so，我不会出错。

使用 ctypes._reset_cache() 没有帮助。

我如何告诉 ctypes 从硬盘实际重新加载库？

Answer 1

我不知道如何指示 ctypes 如何卸载库(在 [Python.Docs]: ctypes - A foreign function library for Python 上没有找到方法，但这并不意味着没有)。

它可以通过强制加载程序(减少库的引用​​计数并)通过 [Man7]: DLCLOSE(3P) 卸载它来手动完成。 (另请阅读 [Man7]: DLOPEN(3) 以获取有关加载/卸载库的更多信息)。

dll00.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;
}

code00.py:

#!/usr/bin/env python

import ctypes as cts
import sys


DLL_NAME = "./dll00.{:s}".format("dll" if sys.platform[:3].lower() == "win" else "so")


def handle_dll(name=DLL_NAME):
    dll = cts.CDLL(name)
    func0 = dll.func0
    func0.argtypes = (cts.c_int,)
    func0.restype = cts.c_int
    return dll, func0


def main(*argv):
    dlclose_func = cts.CDLL(None).dlclose
    dlclose_func.argtypes = (cts.c_void_p,)
    dlclose_func.restype = cts.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 dll00.so dll00.c), and when done press ENTER here... ")
    dll, func0 = handle_dll()
    res = func0(42)
    print(res)


if __name__ == "__main__":
    print("Python {:s} {:03d}bit on {:s}\n".format(" ".join(elem.strip() for elem in sys.version.split("\n")),
                                                   64 if sys.maxsize > 0x100000000 else 32, sys.platform))
    rc = main(*sys.argv[1:])
    print("\nDone.\n")
    sys.exit(rc)

输出:

(qaic-env) [cfati@cfati-5510-0:/mnt/e/Work/Dev/StackOverflow/q050964033]> ~/sopr.sh
### Set shorter prompt to better fit when pasted in StackOverflow (or other) pages ###

[064bit prompt]> ls
code00.py  dll00.c  dll00.so
[064bit prompt]>
[064bit prompt]> python code00.py
Python 3.8.10 (default, Nov 26 2021, 20:14:08) [GCC 9.3.0] 064bit 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 dll00.so dll00.c), and when done press ENTER here... 
From C - arg0: 42, alter_factor: 3
126

Done.

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