在查看man page页面时,我在Linux手册页中偶然发现了一个令人困惑的注意事项:
在某些体系结构中涉及到一个联合:不要同时分配sa_handler和sa_sigaction(sigaction man page)。
有两种可能的方法来阅读它:
.sa_sigaction
中设置.sa_handler
和struct sigaction
。.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.上面的代码很好,但是当定义2是正确的时候,因为我混合它将是无效的。
哪一个是真的?注意:在我的架构中,它被定义为联合
它只是谈论相同的结构。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。它可能实际上是这样的:
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。