// SPDX-License-Identifier: GPL-2.0#include <signal.h>#include "subcmd-util.h"#include "sigchain.h" #define SIGCHAIN_MAX_SIGNALS 32 struct sigchain_signal {	sigchain_fun *old;	int n;	int alloc;};static struct sigchain_signal signals[SIGCHAIN_MAX_SIGNALS]; static void check_signum(int sig){	if (sig < 1 || sig >= SIGCHAIN_MAX_SIGNALS)		die("BUG: signal out of range: %d", sig);} static int sigchain_push(int sig, sigchain_fun f){	struct sigchain_signal *s = signals + sig;	check_signum(sig); 	ALLOC_GROW(s->old, s->n + 1, s->alloc);	s->old[s->n] = signal(sig, f);	if (s->old[s->n] == SIG_ERR)		return -1;	s->n++;	return 0;} int sigchain_pop(int sig){	struct sigchain_signal *s = signals + sig;	check_signum(sig);	if (s->n < 1)		return 0; 	if (signal(sig, s->old[s->n - 1]) == SIG_ERR)		return -1;	s->n--;	return 0;} void sigchain_push_common(sigchain_fun f){	sigchain_push(SIGINT, f);	sigchain_push(SIGHUP, f);	sigchain_push(SIGTERM, f);	sigchain_push(SIGQUIT, f);	sigchain_push(SIGPIPE, f);}