RFC: fix problems with errors during quitting (killed.exp)

["J. Johnston" <jjohnstn at redhat dot com>]

The following patch fixes the problem that occurs when an error happens while
quitting.  Often an error() call gets triggered and the poor user is thrown
back to the gdb command line where they try to quit again.  I made an attempt
to fix a similar problem by handling ptrace errors in quitting, however, thread-db.c gets
into multiple precarious situations because it has to rely on libthread_db
for information.  When the thread has been killed/maimed, it gets errors when
they are not expected and quitting becomes impossible.

My new strategy is to intercept error() calls during quitting.  Basically,
a simple get/set function is set up to denote when we the user has confirmed
a quit.  If we get into top.c:throw_exception() and quit has been confirmed, it
exits the program.  This handles any number of messy kill scenarios and causes
no regressions in the current testsuite.  It fixes gdb.threads/killed.exp.  I made the
functions external so other parts of gdb can register a confirmed quit if necessary.  I could
make these routines static if this feature is not needed.  I chose to exit with the
code being passed on the jump.  There may be a better constant choice.

If anyone can think of scenario that this code is not going to handle correctly that might
not be exercised by the testsuite, please let me know.

Tested on x86 and ia64.

Comments?

2003-09-04  Jeff Johnston  <jjohnstn@redhat.com>

	* top.h (get_quit_confirmed, set_quit_confirmed): New prototypes.
	* top.c (get_quit_confirmed, set_quit_confirmed): New functions.
	(throw_exception): If quit confirmed, exit instead of jumping.

Index: top.c
===================================================================
RCS file: /cvs/src/src/gdb/top.c,v
retrieving revision 1.75
diff -u -r1.75 top.c
--- top.c	16 Aug 2003 18:38:46 -0000	1.75
+++ top.c	4 Sep 2003 21:34:25 -0000
@@ -341,6 +341,9 @@
      to that call via setjmp's return value.  Note that REASON can't
      be zero, by definition in defs.h. */
 
+  if (get_quit_confirmed ())
+    exit ((int) reason);
+
   (NORETURN void) SIGLONGJMP (*catch_return, (int) reason);
 }
 
@@ -546,6 +549,21 @@
   return catch_errors (do_captured_command, &args, "", mask);
 }
 
+/* Flag to indicate if quit has been performed.  */
+static int quit_confirmed;
+
+/* Verify if end-user has performed a quit operation.  */
+int
+get_quit_confirmed (void)
+{
+  return quit_confirmed;
+}
+
+void
+set_quit_confirmed (int val)
+{
+  quit_confirmed = val;
+}
 
 /* Handler for SIGHUP.  */
 
@@ -560,6 +578,7 @@
 {
   caution = 0;			/* Throw caution to the wind -- we're exiting.
 				   This prevents asking the user dumb questions.  */
+  set_quit_confirmed (1);
   quit_command ((char *) 0, 0);
   return 0;
 }
@@ -771,6 +790,7 @@
 	(*window_hook) (instream, get_prompt ());
 
       quit_flag = 0;
+      set_quit_confirmed (0);
       if (instream == stdin && stdin_is_tty)
 	reinitialize_more_filter ();
       old_chain = make_cleanup (null_cleanup, 0);
@@ -836,6 +856,7 @@
   while (instream && !feof (instream))
     {
       quit_flag = 0;
+      set_quit_confirmed (0);
       if (instream == stdin && stdin_is_tty)
 	reinitialize_more_filter ();
       old_chain = make_cleanup (null_cleanup, 0);
@@ -1422,6 +1443,8 @@
     {
       char *s;
 
+      set_quit_confirmed (0);
+
       /* This is something of a hack.  But there's no reliable way to
          see if a GUI is running.  The `use_windows' variable doesn't
          cut it.  */
@@ -1436,6 +1459,7 @@
 	return 0;
     }
 
+  set_quit_confirmed (1);
   return 1;
 }
 
Index: top.h
===================================================================
RCS file: /cvs/src/src/gdb/top.h,v
retrieving revision 1.9
diff -u -r1.9 top.h
--- top.h	8 Jun 2003 18:27:14 -0000	1.9
+++ top.h	4 Sep 2003 21:34:25 -0000
@@ -42,6 +42,8 @@
 				     void (*execute_command_func) (char *,
 								   int));
 extern int quit_confirm (void);
+extern int get_quit_confirmed (void);
+extern void set_quit_confirmed (int);
 extern void quit_force (char *, int);
 extern void quit_command (char *, int);
 extern int quit_cover (void *);