#define _GNU_SOURCE
#include <errno.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/wait.h>

static int child_pid;           /* process id of child */
static int pipe_fd[2];          /* file descriptors for pipe */
static int caught[NSIG];

static void def_handler(int sig)
{
	fprintf(stderr, "Unexpected signal %d received.\n", sig);
	exit(1);
}

static void read_pipe(void)
{
	static char buf[1];
	if (read(pipe_fd[0], buf, sizeof(buf)) < 0) {
		fprintf(stderr, "read() pipe failed. error:%d %s.\n",
			errno, strerror(errno));
		exit(1);
	}
}

static void write_pipe(void)
{
	if (write(pipe_fd[1], "", 1) < 0) {
		fprintf(stderr, "write() pipe failed. error:%d %s.\n",
			errno, strerror(errno));
		exit(1);
	}
}

static void parent(int testsig)
{
	int term_stat;
	int sig;

	for (sig = 1; sig < NSIG; sig++) {
		switch(sig) {
		    case SIGKILL:
		    case SIGSTOP:
		    case SIGCONT:
			break;
		    case SIGCLD:
			continue;
		    default:
			if (signal(sig, def_handler) == SIG_ERR) {
				fprintf(stderr, "signal() failed for signal %d. error:%d %s.\n",
					sig, errno, strerror(errno));
				exit(1);
			}
		}
	}
	read_pipe();
	printf("p sending signal %d\n", testsig);
	if (kill(child_pid, testsig) < 0) {
		fprintf(stderr, "kill() failed. sig:%d error:%d %s.\n",
			testsig, errno, strerror(errno));
		exit(1);
	}
	if (wait(&term_stat) < 0) {
		fprintf(stderr, "wait() failed. error:%d %s.\n",
			errno, strerror(errno));
		exit(1);
	}
	if (WIFSIGNALED(term_stat)) {
		sig = WTERMSIG(term_stat);
		fprintf(stderr, "Unexpected signal killed child. sig:%d.\n", sig);
		exit(1);
	}
	if (!WIFEXITED(term_stat)) {
		fprintf(stderr, "Unexpected return killed child.\n");
		exit(1);
	}
	printf("p Child exited with status %d\n", WEXITSTATUS(term_stat));
	return;
}

static void handler(int sig)
{
	printf("c caught signal %d", sig);
	if (sig == SIGALRM)
		printf(" - ignored");
	else
		++caught[sig];
	printf("\n");
}

static void child(int testsig)
{
	int rv;
	int sig;
	printf("c start %d\n", getpid());
	if (signal(testsig, handler) == SIG_ERR) {
		fprintf(stderr,
			"signal() failed for signal %d. error:%d %s.\n",
			testsig, errno, strerror(errno));
		exit(1);
	}
	printf("c after defining testsig\n");
	if (signal(SIGALRM, handler) == SIG_ERR) {
		fprintf(stderr,
			"signal() failed for signal %d. error:%d %s.\n",
			SIGALRM, errno, strerror(errno));
		exit(1);
	}
	printf("c after defining alrm\n");

	if ((rv = sighold(testsig)) != 0) {
		fprintf(stderr,
			"sighold did not return 0. rv:%d sig:%d.\n", rv, testsig);

	}
#ifdef MAGIC_INCANTATION
	/* holding sig32 makes the hold of other rt signals work */
	if ((rv = sighold(32)) != 0) {
		fprintf(stderr,
			"sighold did not return 0. rv:%d sig:%d.\n", rv, 32);

	}
#endif
	printf("c setup complete\n");
	write_pipe();
	alarm(2);
	pause();
	for (sig = 1; sig < NSIG; ++sig) {
		if (caught[sig]) {
			fprintf(stderr, "Child caught signal %d before it was unblocked\n", sig);
			exit(1);
		}
	}
	printf("c releasing signal %d\n", testsig);
	if ((rv = sigrelse(testsig)) != 0) {
		fprintf(stderr, "sigrelse did not return 0. rv:%d\n", rv);

	}
	for (sig = 1; sig < NSIG; ++sig) {
		if (caught[sig] && sig != testsig) {
			fprintf(stderr, "Child caught unexpected signal %d\n", sig);
			exit(1);
		}
	}
	if (caught[testsig] != 1) {
		fprintf(stderr, "Child did not receive signal %d after it was released\n", testsig);
		exit(1);
	}
	exit(0);
}

#define TESTSIG 45

int main(void)
{
	setvbuf(stdout, NULL, _IONBF, 0);
	if (pipe(pipe_fd) < 0) {
		fprintf(stderr, "pipe() failed. error:%d %s.\n",
			errno, strerror(errno));
		return 1;
	}
	if ((child_pid = fork()) < 0) {
		fprintf(stderr, "fork() failed. error:%d %s.\n",
			errno, strerror(errno));
		return 1;
	}
	if (child_pid > 0) {
		parent(TESTSIG);
	} else {
		child(TESTSIG);
	}
	return 0;
}