尽管我在 python ctypes 中设置了信号处理程序，但它没有被调用

Question

我已经尝试使用 sigaction 和 ctypes 设置信号处理程序。（我知道它可以在 python 中使用信号模块，但我想尝试学习。）

当我向这个进程发送 SIGTERM 时，它没有调用我设置的处理程序，只打印 "Terminated"。为什么它不调用处理程序？

我使用 Ubuntu 19.10 和 Python 3.7.5 x64。

import ctypes
from ctypes import *
from ctypes.util import *
from os import getpid


class sigset_t(Structure):
    __fields__ = [
        ("__val",               c_ulong*16)        
    ]

class sigval_t(Union):
    __fields__ = [
        ("sival_int",           c_int),
        ("sival_ptr",           c_void_p)
    ]



class siginfo_t(Structure):
    __fields__ = [
        ("si_signo",            c_int),
        ("si_errno",            c_int),
        ("si_code",             c_int),
        ("si_trapno",           c_int),
        ("si_pid",              c_uint),
        ("si_status",           c_int),
        ("si_utime",            c_long),
        ("si_stime",            c_long),
        ("si_value",            sigval_t),
        ("si_int",              c_int),
        ("si_ptr",              c_void_p),
        ("si_overrun",          c_int),
        ("si_timerid",          c_int),
        ("si_addr",             c_void_p),
        ("si_band",             c_long),
        ("si_fd",               c_int),
        ("si_addr_lsb",         c_short),
        ("si_call_addr",        c_void_p),
        ("si_syscall",          c_int),
        ("si_arch",             c_uint)

    ]

sa_handler_functype = CFUNCTYPE(None, c_int)
sigaction_functype = CFUNCTYPE(None, c_int, siginfo_t, c_void_p)


class SIGACTION(Structure):
    __fields__ = [
        ("sa_handler",          sa_handler_functype),
        ("sa_sigaction",        sigaction_functype),
        ("sa_mask",             sigset_t),
        ("sa_flags",            c_int),

    ]


def p(sig): # signal handler function
    libc.puts("bye")

libc_path = find_library("c")
libc = CDLL(libc_path)

libc.sigaction.restype = c_int
libc.sigaction.argtypes = [c_int, POINTER(SIGACTION), POINTER(SIGACTION)]

act = SIGACTION(sa_handler=sa_handler_functype(p))
print(act)
res = libc.sigaction(15, act, None)
print(res)
print("pid:", getpid()) # show pid
while True: # wait until receive sigterm signal
    pass

Answer 1

清单[Python 3.Docs]: ctypes - A foreign function library for Python.

代码有一些问题：

ctypes.Structure后代需要定义_fields_(而不是__fields__）。相应地更改了结构
将 struct sigaction *（指针）作为参数传递给 sigaction
根据 /usr/include/bits 中的文件内容修改了结构定义（在我的 Ubtu 16 x64 VM)
为任何使用的函数 (puts) 定义了 argtypes 和 restype。检查了解更多详情
其他（次要）更改

code00.py:

#!/usr/bin/env python3

import sys
import os
import time
from ctypes import Structure, Union, POINTER, CFUNCTYPE, CDLL, byref, sizeof, \
    c_short, c_int, c_uint, c_long, c_ulong, c_char_p, c_void_p


SIGTERM = 15


class sigset_t(Structure):
    _fields_ = [
        ("__val", c_ulong * (1024 // (8 * sizeof (c_long)))),
    ]


'''
class sigval_t(Union):
    _fields_ = [
        ("sival_int", c_int),
        ("sival_ptr", c_void_p),
    ]


class siginfo_t(Structure):
    _fields_ = [
        ("si_signo", c_int),
        ("si_errno", c_int),
        ("si_code", c_int),
        ("_pad", c_int * 29),
    ]


sa_sigaction_functype = CFUNCTYPE(None, c_int, POINTER(siginfo_t), c_void_p)
'''
sa_handler_functype = CFUNCTYPE(None, c_int, use_errno=True)


class SIGACTION(Structure):
    _fields_ = [
        ("sa_handler", sa_handler_functype),
        ("sa_mask", sigset_t),
        ("sa_flags", c_int),
        ("sa_restorer", c_void_p),
    ]


libc = CDLL(None)


def sighandler(sig):  # Signal handler function
    libc.puts.argtypes = [c_char_p]
    libc.puts.restype = c_int
    libc.puts("Custom signal handler called for signal {0:d}".format(sig).encode())


def main(*argv):

    libc.sigaction.argtypes = [c_int, POINTER(SIGACTION), POINTER(SIGACTION)]
    libc.sigaction.restype = c_int

    signal_number = SIGTERM
    act = SIGACTION(sa_handler=sa_handler_functype(sighandler))
    #print(act)

    res = libc.sigaction(signal_number, byref(act), None)
    print("sigaction result: {0:d}".format(res))
    print("PId {0:d} waiting for SIG {1:d}...".format(os.getpid(), signal_number))

    while 1:
        time.sleep(0.1)


if __name__ == "__main__":
    print("Python {0:s} {1:d}bit on {2:s}\n".format(" ".join(item.strip() for item in sys.version.split("\n")), 64 if sys.maxsize > 0x100000000 else 32, sys.platform))
    main(*sys.argv[1:])
    print("\nDone.")

输出（程序运行，发送SIGTERM两次然后SIGKILL从另一个终端）：

[cfati@cfati-ubtu16x64-0:~/Work/Dev/Whosebug/q059521251]> uname -m
x86_64
[cfati@cfati-ubtu16x64-0:~/Work/Dev/Whosebug/q059521251]> cat /etc/lsb-release | grep DESCR
DISTRIB_DESCRIPTION="Ubuntu 16.04.6 LTS"
[cfati@cfati-ubtu16x64-0:~/Work/Dev/Whosebug/q059521251]> python3 code00.py
Python 3.5.2 (default, Oct  8 2019, 13:06:37) [GCC 5.4.0 20160609] 64bit on linux

sigaction result: 0
PId 20050 waiting for SIG 15...
Custom signal handler called for signal 15
Custom signal handler called for signal 15
Killed

尽管我在 python ctypes 中设置了信号处理程序，但它没有被调用

Signal handler does not be invoked despite I have set it in python ctypes

python

linux

ubuntu

ctypes

signals