Path: utzoo!mnetor!uunet!tektronix!tekgen!rad
From: rad@tekgen.TEK.COM (Richard Doty)
Newsgroups: comp.bugs.4bsd
Subject: dbx 'cont n' does not work on waiting process
Message-ID: <2580@tekgen.TEK.COM>
Date: 19 Mar 88 01:38:56 GMT
Reply-To: rad@tektronix.tek.com (Richard Doty)
Organization: Tektronix, Inc., Beaverton, OR.
Lines: 63

Index:	ucb/dbx/process.c 4.3BSD

Description:
	If the user interrupts dbx, and then types 'cont n' where n is
	the number (or name) of the signal to be sent to the controlled
	process, the signal is not sent if the process is waiting for
	input and the handler for the signal is either SIG_IGN or
	SIF_DFL.  This is because:

	cont(signo)
	   calls stepover()
	      calls dostep()
		 calls stepto()
	            calls xto()
		       calls resume(DEFSIG)	<-- DEFSIG is hardcoded
			  calls pcont(c, signo=DEFSIG)
			     calls setinfo(  , signo=DEFSIG)
			     calls ptrace(... p->signo)
	
	When setinfo() is called with signal DEFSIG, it sets p->signo
	to 0 if the process has a signal handler of 0 or 1,
	and no signal gets sent to the process.

	Ideally, the specified signal number would be propagated down the
	chain to xto(), but that results in a lot of changed argument
	lists and invocations.

	A shorter fix is to set p->signo in cont() and at the same time
	change the signal handler to something other than 0 or 1 so
	setinfo() won't change p->signo.

Repeat-By:
	Run dbx on the following trivial program, then type ^C to
	interrupt dbx and try to send a SIGINT to the process by
	typing 'cont 2'.The process will continue without being
	interrupted.

		main()
		{
			int i;
			char buf[20];
			i = read(0,buf,19);
			write(1,buf,i);
		}
Fix:
	I am a little suspicious of this fix, but can't find anything
	really wrong with it.

*** .dist/process.c	Fri May 31 10:15:12 1985
--- process.c	Fri Mar 18 15:37:03 1988
***************
*** 321,326 ****
--- 321,330 ----
  {
      integer s;
  
+     if (signo != DEFSIG) {
+ 	process->signo = signo;
+ 	process->sigstatus = 2; /* fake out setinfo() */
+     }
      dbintr = signal(SIGINT, intr);
      if (just_started) {
  	just_started = false;