abort.c

#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

void
abort(void)			/* POSIX-style abort() function */
{
	sigset_t			mask;
	struct sigaction	action;

	/*
	 * Caller can't ignore SIGABRT, if so reset to default.
	 */
	sigaction(SIGABRT, NULL, &action);
	if (action.sa_handler == SIG_IGN) {
		action.sa_handler = SIG_DFL;
		sigaction(SIGABRT, &action, NULL);
	}
	if (action.sa_handler == SIG_DFL)
		fflush(NULL);			/* flush all open stdio streams */

	/*
	 * Caller can't block SIGABRT; make sure it's unblocked.
	 */
	sigfillset(&mask);
	sigdelset(&mask, SIGABRT);	/* mask has only SIGABRT turned off */
	sigprocmask(SIG_SETMASK, &mask, NULL);
	kill(getpid(), SIGABRT);	/* send the signal */

	/*
	 * If we're here, process caught SIGABRT and returned.
	 */
	fflush(NULL);				/* flush all open stdio streams */
	action.sa_handler = SIG_DFL;
	sigaction(SIGABRT, &action, NULL);	/* reset to default */
	sigprocmask(SIG_SETMASK, &mask, NULL);	/* just in case ... */
	kill(getpid(), SIGABRT);				/* and one more time */
	exit(1);	/* this should never be executed ... */
}