sigaction : 使用“void (*sa_sigaction)(int, siginfo_t *, void *);" [英] sigaction : using "void (*sa_sigaction)(int, siginfo_t *, void *);"

问题描述

在 sigaction 联机帮助页中是这样写的:

In sigaction manpage it's written :

sa_sigaction 还指定要与 signum 关联的操作.这个函数接收信号编号作为它的第一个参数，一个指向 siginfo_t 作为第二个参数的指针和指向 ucon 的指针text_t(转换为 void*)作为它的第三个参数.

sa_sigaction also specifies the action to be associated with signum. This function receives the signal number as its first argument, a pointer to a siginfo_t as its second argument and a pointer to a ucon- text_t (cast to void*) as its third argument.

所以我们可以将参数传递给信号处理程序(通过 void*)，但是我找不到路.有没有办法把它放在任何地方?

So we can pass arguments to the signal handler (throught void*), but I can't find the way. Is there no way to put it anywhere?

示例:

struct ping_val
{
    int data1;
    int data2;
};

void ping(int sig, siginfo_t *siginf, void *ptr) 
{
    // ....
}

int main()
{
    struct sigaction sa_ping;
    ping_val foo;
    foo.data1 = 3;
    foo.data2 = 4;
    sa_ping.sa_sigaction = ping;
    sigemptyset(&sa_ping.sa_mask);
    sa_ping.sa_flags = 0;
    sigaction(SIGALRM, &sa_ping, NULL);
    // ....
}

我在哪里可以在 ping 的参数中传递 foo 结构值(在 struct * 中进行强制转换)???

Where I can pass foo structure value in argument in ping (with a cast in struct *)???

推荐答案

你写的:

所以我们可以[通过 void* ucontext_t 参数] 将参数传递给信号处理程序，但我找不到方法.

找不到这样的方法 — ucontext_t 参数由系统本身设置并引用 "发送信号时中断的接收线程的上下文."

There is no such way to be found — the ucontext_t argument is set by the system itself and refers to "the receiving thread's context that was interrupted when the signal was delivered."

(具体来说，根据规范至少是对中断上下文的引用，以及对该上下文的特定于机器的表示，以及当前上下文的堆栈及其阻塞信号集.)

(Specifically, by spec it contains at least a reference to that interrupted context, and to a machine-specific representation of that context, and also the current context's stack and its set of blocked signals.)

您可能不需要任何这些.如果您希望您的程序在收到信号时采取一些行动和/或修改其状态，那么您可以在信号处理程序中安全使用的策略数量有限(volatile sigatomic_t 标志，自管道，特定于平台的接口)，但是您的主循环当然可以根据刚刚收到的 SIGFOO 的知识做您想做的任何事情.

You probably don't need any of this. If you want your program to take some action and/or modify its state on receipt of a signal, you've a limited number of tactics that can be safely used in a signal handler (volatile sigatomic_t flags, self-pipes, platform-specific interfaces), but then your main loop can of course do whatever you want with the knowledge that SIGFOO was just received.

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