2006-12-13  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb/frame.c (get_prev_frame): Already the first `PC == 0' stack frame
	is declared invalid, not the second one as before.

2006-12-13  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.threads/bt-clone-stop.exp, gdb.threads/bt-clone-stop.c:
	Backtraced `clone' must not have `PC == 0' as its previous frame.


--- ./gdb/frame.c	10 Nov 2006 20:11:35 -0000	1.215
+++ ./gdb/frame.c	13 Dec 2006 19:06:19 -0000
@@ -1390,19 +1390,28 @@ get_prev_frame (struct frame_info *this_
       return NULL;
     }
 
+  prev_frame = get_prev_frame_1 (this_frame);
+  if (!prev_frame)
+    return NULL;
+
   /* Assume that the only way to get a zero PC is through something
      like a SIGSEGV or a dummy frame, and hence that NORMAL frames
-     will never unwind a zero PC.  */
-  if (this_frame->level > 0
+     will never unwind a zero PC.
+     This check must be done after retrieving the previous frame as we
+     would report the last PC == 0 frame:
+     	#4  0x00000036dd0c68c3 in clone () from /lib64/tls/libc.so.6
+     	#5  0x0000000000000000 in ?? ()
+     */
+  if (prev_frame->level > 0
+      && get_frame_type (prev_frame) == NORMAL_FRAME
       && get_frame_type (this_frame) == NORMAL_FRAME
-      && get_frame_type (get_next_frame (this_frame)) == NORMAL_FRAME
-      && get_frame_pc (this_frame) == 0)
+      && get_frame_pc (prev_frame) == 0)
     {
-      frame_debug_got_null_frame (gdb_stdlog, this_frame, "zero PC");
+      frame_debug_got_null_frame (gdb_stdlog, prev_frame, "zero PC");
       return NULL;
     }
 
-  return get_prev_frame_1 (this_frame);
+  return prev_frame;
 }
 
 CORE_ADDR
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ ./gdb/testsuite/gdb.threads/bt-clone-stop.c	13 Dec 2006 19:06:19 -0000
@@ -0,0 +1,39 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2006 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 2 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, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+   MA 02110-1301, USA.  */
+
+
+#include <pthread.h>
+#include <unistd.h>
+#include <assert.h>
+
+
+void *threader(void *arg)
+{
+	assert(0);
+	return NULL;
+}
+
+int main()
+{
+	pthread_t t1;
+
+	pthread_create(&t1,NULL,threader,(void *)NULL);
+	for (;;)
+		pause();
+}
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ ./gdb/testsuite/gdb.threads/bt-clone-stop.exp	13 Dec 2006 19:06:19 -0000
@@ -0,0 +1,56 @@
+# Copyright 2006 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 2 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, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  
+
+if $tracelevel then {
+    strace $tracelevel
+}
+
+set testfile bt-clone-stop
+set srcfile ${testfile}.c
+set binfile ${objdir}/${subdir}/${testfile}
+if  { [gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
+    untested "Couldn't compile test program"
+    return -1
+}
+
+# Get things started.
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
+# threader: threader.c:8: threader: Assertion `0' failed.
+# Program received signal SIGABRT, Aborted.
+
+gdb_test "run" \
+     "Program received signal SIGABRT.*" \
+     "run"
+
+# #5  0x0000003421ecd62d in ?? () from /lib64/libc.so.6
+# #6  0x0000000000000000 in ?? ()
+# (gdb)
+# Line `#6' must not be present
+# Keep those two cases in this order!
+# Fallback is some invalid output (FAIL).
+gdb_test_multiple "bt" "0x0 entry output invalid" {
+    -re "in threader \\(.*\n#\[0-9\]* *0x0* in .*$gdb_prompt $" {
+    	fail "0x0 entry found there"
+    }
+    -re "in threader \\(.*$gdb_prompt $" {
+    	pass "0x0 entry not found there"
+    }
+}