Re: RFC: fix crash when inferior exits during "continue"

[Tom Tromey <tromey@redhat.com>]

>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:

Pedro> Yeah.  We also don't randomly switch to another thread if the previous
Pedro> selected thread exits (and this is the reason we have "exited" threads).
Pedro> Otherwise, if the user is typing

Pedro> (gdb) some_command_that_applies_to_the_current_thread <enter>

Pedro> and the current thread disappears while the user is typing,
Pedro> the command ends up being applied to a random thread, which is
Pedro> not good.

This makes sense to me if the user entered a background command.
But why not switch if the last command was a foreground command?

Pedro>  - Make make_cleanup_restore_current_thread "lock" the current
Pedro>    inferior, so it isn't removed even if it is "removable".
Pedro>    We do something similar for threads -- That's the whole reason
Pedro>    for thread_info->refcount.  (This is also Jan's suggestion.)

What do you think of the appended?

Tom

2012-02-15  Tom Tromey  <tromey@redhat.com>

	PR c++/13653:
	* thread.c (struct current_thread_cleanup) <was_removable>: New
	field.
	(do_restore_current_thread_cleanup): Restore 'removable' field.
	(restore_current_thread_cleanup_dtor): Likewise.
	(make_cleanup_restore_current_thread): Initialize new field.

2012-02-15  Tom Tromey  <tromey@redhat.com>

	* gdb.base/inferior-died.c: New file.
	* gdb.base/inferior-died.exp: New file.

diff --git a/gdb/testsuite/gdb.base/inferior-died.c b/gdb/testsuite/gdb.base/inferior-died.c
new file mode 100644
index 0000000..66227cf
--- /dev/null
+++ b/gdb/testsuite/gdb.base/inferior-died.c
@@ -0,0 +1,37 @@
+/* Test for fork-related gdb bug
+
+   Copyright 2012 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+void function(void)
+{
+  exit (0);			/* Break here */
+}
+
+int main()
+{
+  pid_t child = fork ();
+
+  if (child == 0)
+    function ();
+  else
+    waitpid (child, NULL, 0);
+}
diff --git a/gdb/testsuite/gdb.base/inferior-died.exp b/gdb/testsuite/gdb.base/inferior-died.exp
new file mode 100644
index 0000000..458dd61
--- /dev/null
+++ b/gdb/testsuite/gdb.base/inferior-died.exp
@@ -0,0 +1,56 @@
+# Copyright 2012 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+if { [is_remote target] || ![isnative] } then {
+    unsupported "inferior-died.exp"
+    continue
+}
+
+# Until "set follow-fork-mode" and "catch fork" are implemented on
+# other targets...
+#
+if {![istarget "hppa*-hp-hpux*"] && ![istarget "*-*-linux*"]} then {
+    unsupported "inferior-died.exp"
+    continue
+}
+
+if { ![support_displaced_stepping] } {
+    unsupported "inferior-died.exp"
+    return -1
+}
+
+set testfile "inferior-died"
+set srcfile ${testfile}.c
+set binfile ${objdir}/${subdir}/${testfile}
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} ${testfile}.c] } {
+    return -1
+}
+
+gdb_test_no_output "set detach-on-fork off"
+gdb_test_no_output "set target-async on"
+gdb_test_no_output "set non-stop on"
+
+if ![runto_main] {
+    return
+}
+
+set line [gdb_get_line_number "Break here"]
+gdb_breakpoint $srcfile:$line
+
+gdb_continue_to_breakpoint "breakpoint"
+
+gdb_test "inferior 2" "Switching to inferior 2.*"
+gdb_test "continue" "exited normally.*"
diff --git a/gdb/thread.c b/gdb/thread.c
index 9a29383..c7c9699 100644
--- a/gdb/thread.c
+++ b/gdb/thread.c
@@ -1072,6 +1072,7 @@ struct current_thread_cleanup
   int selected_frame_level;
   int was_stopped;
   int inf_id;
+  int was_removable;
 };
 
 static void
@@ -1095,6 +1096,8 @@ do_restore_current_thread_cleanup (void *arg)
       set_current_inferior (find_inferior_id (old->inf_id));
     }
 
+  current_inferior ()->removable = old->was_removable;
+
   /* The running state of the originally selected thread may have
      changed, so we have to recheck it here.  */
   if (!ptid_equal (inferior_ptid, null_ptid)
@@ -1112,10 +1115,14 @@ restore_current_thread_cleanup_dtor (void *arg)
 {
   struct current_thread_cleanup *old = arg;
   struct thread_info *tp;
+  struct inferior *inf;
 
   tp = find_thread_ptid (old->inferior_ptid);
   if (tp)
     tp->refcount--;
+  inf = find_inferior_id (old->inf_id);
+  if (inf != NULL)
+    inf->removable = old->was_removable;
   xfree (old);
 }
 
@@ -1129,6 +1136,7 @@ make_cleanup_restore_current_thread (void)
   old = xmalloc (sizeof (struct current_thread_cleanup));
   old->inferior_ptid = inferior_ptid;
   old->inf_id = current_inferior ()->num;
+  old->was_removable = current_inferior ()->removable;
 
   if (!ptid_equal (inferior_ptid, null_ptid))
     {
@@ -1156,6 +1164,8 @@ make_cleanup_restore_current_thread (void)
 	tp->refcount++;
     }
 
+  current_inferior ()->removable = 0;
+
   return make_cleanup_dtor (do_restore_current_thread_cleanup, old,
 			    restore_current_thread_cleanup_dtor);
 }