[PATCH] PR 15520 - GDB step command crashed on non-stop mode

[Muhammad Waqas <mwaqas at codesourcery dot com>]

Hi!

In adjust_pc_after_break

if (singlestep_breakpoints_inserted_p
	  || !ptid_equal (ecs->ptid, inferior_ptid)
	  || !currently_stepping (ecs->event_thread)
	  || ecs->event_thread->prev_pc == breakpoint_pc)
	regcache_write_pc (regcache, breakpoint_pc);

We should check for breakpoint_pc is software_breakpoint (
as here we only consider it is software breakpoint that is not enough
in my thoughts) which is missing right now and it keep executing
again and again the same instruction until the breakpoint is ripped
off the moribund list and our program crashed if breakpoint is not
software.

I place this check and this fix the bug. What's your thought is it ok?
Tested on x86_64-Ubuntu-linux-gnu, no regressions.

Find the patch in attachment as well.

gdb/ChangeLog
2013-09-13  Muhammad Waqas  <mwaqas@codesourcery.com>

	PR 15520
	* infrun.c (adjust_pc_after_break): In non-stop mode
	verify software_breakpoint at breakpoint_pc before backup
	to breakpoint address.

gdb.base/ChangeLog
2013-09-13  Muhammad Waqas  <mwaqas@codesourcery.com>

	PR 15520
	*gdb.base/pr15520.cc: New file.
	*gdb.base/pr15520.exp: New file.

Index: infrun.c
===================================================================
RCS file: /cvs/src/src/gdb/infrun.c,v
retrieving revision 1.590
diff -u -p -r1.590 infrun.c
--- infrun.c	3 Sep 2013 17:22:45 -0000	1.590
+++ infrun.c	16 Sep 2013 08:06:02 -0000
@@ -3038,7 +3038,8 @@ adjust_pc_after_break (struct execution_
       if (singlestep_breakpoints_inserted_p
 	  || !ptid_equal (ecs->ptid, inferior_ptid)
 	  || !currently_stepping (ecs->event_thread)
-	  || ecs->event_thread->prev_pc == breakpoint_pc)
+	  || (ecs->event_thread->prev_pc == breakpoint_pc
+	      && software_breakpoint_inserted_here_p (aspace, breakpoint_pc)))
 	regcache_write_pc (regcache, breakpoint_pc);

       do_cleanups (old_cleanups);
Index: testsuite/gdb.base/pr15520.cc
===================================================================
RCS file: testsuite/gdb.base/pr15520.cc
diff -N testsuite/gdb.base/pr15520.cc
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.base/pr15520.cc	16 Sep 2013 08:06:03 -0000
@@ -0,0 +1,33 @@
+# Copyright 2013 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 <string>
+using namespace std;
+
+void
+fun (string &str1, string &str2)
+{
+  str1 += str2;
+}
+
+int
+main (void)
+{
+  string str1 = "abc";
+  string str2 = "def";
+  fun(str1,str2);
+
+  return 0;
+}
Index: testsuite/gdb.base/pr15520.exp
===================================================================
RCS file: testsuite/gdb.base/pr15520.exp
diff -N testsuite/gdb.base/pr15520.exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.base/pr15520.exp	16 Sep 2013 08:06:03 -0000
@@ -0,0 +1,36 @@
+# Copyright 2013 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/>.
+
+#
+# test running programs
+#
+standard_testfile .cc
+
+if {[prepare_for_testing $testfile.exp $testfile $srcfile {debug c++}]} {
+    return -1
+}
+
+if ![runto_main] {
+    untested non-stop-step
+    return -1
+}
+
+gdb_test "set target-async on" ".*" "Set async mode"
+gdb_test "set non-stop on" ".*" "Set non stop mode"
+
+gdb_breakpoint "fun"
+gdb_continue_to_breakpoint "fun"
+gdb_test "step" ".*}.*" "step 1"
+gdb_test "step" ".*main .*$srcfile.*\[\n\r\].*return 0;.*" "step 2"

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