From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <da8ce844cf1ada7a22b076ea326673d5@quanstro.net>
From: erik quanstrom <quanstro@quanstro.net>
Date: Wed, 26 Nov 2008 18:54:17 -0500
To: 9fans@9fans.net
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Subject: [9fans] acidself
Topicbox-Message-UUID: 5341012e-ead4-11e9-9d60-3106f5b1d025

i hope this is worth a few tens of microseconds of
amusement.

the problem is this.  how to get a backtrace when
you may be killed by your parent who is cleaning
up after himself before somone wielding a debugger
has a chance to react?  the amusing answer is just run
acid yourself.  how?  well just catch the note.

sleazy, no? think of it as one more reason to enjoy plan 9.

- erik

----
; cat /rc/bin/stk
#!/bin/rc
for(i)
	echo 'stk()' | acid $i
----
#include <u.h>
#include <libc.h>

void
system(char *cmd, char **av)
{
	int in, pid;

	switch(pid=fork()){
	case -1:
		return;
	case 0:
		in = open("/dev/null", OREAD);
		close(0);
		dup(in, 0);
		exec(cmd, av);
		_exits(0);
	default:
		while(waitpid() < 0)
			postnote(PNPROC, pid, "die");
		break;
	}
}

void
acid(void)
{
	char *av[3], buf[16];

	snprint(buf, sizeof buf, "%d", getpid());
	av[0] = "stk";
	av[1] = buf;
	av[2] = 0;
	system("/bin/stk", av);
}

int
an(void*, char*)
{
	acid();
	return 0;
}

void
main(void)
{
	atnotify(an, 1);
	abort();
	exits("");
}