Question

在查找手册页进行签名时，我偶然发现了Linux手册页中一个令人困惑的注释：

在某些体系结构上，涉及一个联合：不要同时分配给两个 sa_handler和sa_sigaction（sigaction man page）。

有两种可能的阅读方式：

据我所知，这是否意味着不允许您在同一.sa_sigaction中设置.sa_handler和struct sigaction。
还是只允许在整个项目中使用.sa_sigaction或.sa_handler？

struct sigaction sigactionArray[SIGNAL_SIGACTION_ARRAY_SIZE] = {
   {.sa_handler = SIG_DFL, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_DFL, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_DFL, .sa_flags = SA_NODEFER},
   {.sa_sigaction = HandleBacktraceSignals, .sa_flags = SA_SIGINFO | SA_RESTART | SA_ONSTACK},
   {.sa_sigaction = HandleBacktraceSignals, .sa_flags = SA_SIGINFO | SA_RESTART | SA_ONSTACK},
   {.sa_sigaction = HandleBacktraceSignals, .sa_flags = SA_SIGINFO | SA_RESTART | SA_ONSTACK},
   {.sa_sigaction = HandleBacktraceSignals, .sa_flags = SA_SIGINFO | SA_RESTART | SA_ONSTACK},
   {.sa_sigaction = HandleBacktraceSignals, .sa_flags = SA_SIGINFO | SA_RESTART | SA_ONSTACK},
   {.sa_handler = SIG_IGN, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_IGN, .sa_flags = SA_NODEFER},
   {.sa_sigaction = HandleBacktraceSignals, .sa_flags = SA_SIGINFO | SA_RESTART | SA_ONSTACK},
   {.sa_handler = SIG_IGN, .sa_flags = SA_NODEFER},
   {.sa_sigaction = HandleBacktraceSignals, .sa_flags = SA_SIGINFO | SA_RESTART | SA_ONSTACK},
   {.sa_handler = SIG_DFL, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_DFL, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_IGN, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_IGN, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_DFL, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_IGN, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_DFL, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_DFL, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_DFL, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_DFL, .sa_flags = SA_NODEFER},
   {.sa_sigaction = HandleBacktraceSignals, .sa_flags = SA_SIGINFO | SA_RESTART | SA_ONSTACK},
   {.sa_sigaction = HandleBacktraceSignals, .sa_flags = SA_SIGINFO | SA_RESTART | SA_ONSTACK},
   {.sa_handler = SIG_DFL, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_DFL, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_IGN, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_DFL, .sa_flags = SA_NODEFER},
   {.sa_handler = SIG_DFL, .sa_flags = SA_NODEFER},
   {.sa_sigaction = HandleBacktraceSignals, .sa_flags = SA_SIGINFO | SA_RESTART | SA_ONSTACK}
};

根据解释1.上面的代码片段是可以的，但是当定义2.正确时，由于我混合使用，它将是无效的。

哪个是真的？注意：在我的架构上，它定义为联合体

Answer 1

它只是在谈论相同的结构。它解释了原因：它们可能是union的一部分，因此它们在结构中使用相同的内存。例如。实际上可能是这样的：

struct sigaction {
    union {
        void     (*sa_handler)(int);
        void     (*sa_sigaction)(int, siginfo_t *, void *);
    },
    sigset_t   sa_mask;
    int        sa_flags;
    void     (*sa_restorer)(void);
};

因此，写入其中一个会覆盖另一个。

.sa_sigaction和.sa_handler在同一项目中的使用（说明手册页）

1 个答案: