linux abort函数的实现
各位大虾：
看这段代码时，不明白牙。具体请看下面代码：

#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 */
/*为什么这里要重新设置信号处理函数并再次发送SIGABRT信号呢？为什么不直接exit*/
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 ... */
}

[解决办法]
abort() 通常伴随core文件产生
如果直接exit，不会产生core文件