ref: f82124efc20c2976037f821cfa502b03f11bd2a6
dir: /include/bits/darwin/amd64/arch/sigaction.h/
typedef unsigned int sigset_t;
typedef struct siginfo siginfo_t;
struct sigaction {
	union {
		void (*__sa_handler)(int);
		void (*__sa_sigaction)(int, siginfo_t *, void *);
	} __sigaction_u;
	sigset_t sa_mask;
	int sa_flags;
};
#define sa_handler      __sigaction_u.__sa_handler
#define sa_sigaction    __sigaction_u.__sa_sigaction