在同一项目中使用 .sa_sigaction 和 .sa_handler（手册页说明）

Question

在查找 sigaction 的手册页时，我在 Linux 手册页中偶然发现了一个令人困惑的注释：

On some architectures a union is involved: do not assign to both sa_handler and sa_sigaction(sigaction man page).

有两种阅读方式：

这是否意味着，按照我的理解，您不能在同一个 struct sigaction.

.sa_sigaction

.sa_handler

或者在整个项目中只允许使用 .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}
};

按照解释1.上面这段代码可以，但是当定义2.对的时候，我混了就无效了

哪个是真的？注意：在我的架构中，它被定义为一个 union

Answer 1

说的就是同一个结构。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。它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。

在同一项目中使用 .sa_sigaction 和 .sa_handler（手册页说明）

Use of .sa_sigaction and .sa_handler in same project(man page clarification)

linux

signals

manpage

sigaction