Installing a breakpoint on top of a dprintf makes GDB lose control.

While the full fix for PR 15180 isn't in, it's best if we at least
make sure that GDB doesn't lose control when a breakpoint is set at
the same address as a dprintf.

gdb/
2014-06-02  Pedro Alves  <palves@redhat.com>

	* breakpoint.c (build_target_command_list): Don't build a command
	list if we have any duplicate location that isn't a dprintf.

gdb/testsuite/
2014-06-02  Pedro Alves  <palves@redhat.com>

	* gdb.base/dprintf-bp-same-addr.c: New file.
	* gdb.base/dprintf-bp-same-addr.exp: New file.

5 files changed, 120 insertions, 4 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 1d37c56..d8f1cbe 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,10 @@
 2014-06-02  Pedro Alves  <palves@redhat.com>
 
+	* breakpoint.c (build_target_command_list): Don't build a command
+	list if we have any duplicate location that isn't a dprintf.
+
+2014-06-02  Pedro Alves  <palves@redhat.com>
+
 	* breakpoint.c (dprintf_breakpoint_hit): New function.
 	(initialize_breakpoint_ops): Install it as dprintf's
 	breakpoint_hit method.
diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index a966ba2..4e6c627 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -2351,14 +2351,26 @@ build_target_command_list (struct bp_location *bl)
   /* Release commands left over from a previous insert.  */
   VEC_free (agent_expr_p, bl->target_info.tcommands);
 
-  /* For now, limit to agent-style dprintf breakpoints.  */
-  if (bl->owner->type != bp_dprintf
-      || strcmp (dprintf_style, dprintf_style_agent) != 0)
+  if (!target_can_run_breakpoint_commands ())
     return;
 
-  if (!target_can_run_breakpoint_commands ())
+  /* For now, limit to agent-style dprintf breakpoints.  */
+  if (dprintf_style != dprintf_style_agent)
     return;
 
+  /* For now, if we have any duplicate location that isn't a dprintf,
+     don't install the target-side commands, as that would make the
+     breakpoint not be reported to the core, and we'd lose
+     control.  */
+  ALL_BP_LOCATIONS_AT_ADDR (loc2p, locp, bl->address)
+    {
+      loc = (*loc2p);
+      if (is_breakpoint (loc->owner)
+	  && loc->pspace->num == bl->pspace->num
+	  && loc->owner->type != bp_dprintf)
+	return;
+    }
+
   /* Do a first pass to check for locations with no assigned
      conditions or conditions that fail to parse to a valid agent expression
      bytecode.  If any of these happen, then it's no use to send conditions
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index eed85c1..f4d59cf 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2014-06-02  Pedro Alves  <palves@redhat.com>
+
+	* gdb.base/dprintf-bp-same-addr.c: New file.
+	* gdb.base/dprintf-bp-same-addr.exp: New file.
+
 2014-06-02  Edjunior Barbosa Machado  <emachado@linux.vnet.ibm.com>
 
 	* gdb.arch/powerpc-power.exp: Add power8 instructions to the testcase.
diff --git a/gdb/testsuite/gdb.base/dprintf-bp-same-addr.c b/gdb/testsuite/gdb.base/dprintf-bp-same-addr.c
new file mode 100644
index 0000000..b28e102
--- /dev/null
+++ b/gdb/testsuite/gdb.base/dprintf-bp-same-addr.c
@@ -0,0 +1,28 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright (C) 2014 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/>.  */
+
+int
+main (void)
+{
+  int x = 1, y = 1, z = 1;
+
+  ++x; /* before dprintf */
+  ++y; /* set dprintf here */
+  ++z; /* after dprintf */
+
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/dprintf-bp-same-addr.exp b/gdb/testsuite/gdb.base/dprintf-bp-same-addr.exp
new file mode 100644
index 0000000..b0c6d7b
--- /dev/null
+++ b/gdb/testsuite/gdb.base/dprintf-bp-same-addr.exp
@@ -0,0 +1,66 @@
+# Copyright 2014 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 that GDB doesn't lose control when a breakpoint is set at the
+# same address as a dprintf.
+
+standard_testfile
+
+if [prepare_for_testing "failed to prepare" \
+    ${testfile} ${srcfile} {debug}] {
+    return -1
+}
+
+set dp_location [gdb_get_line_number "set dprintf here"]
+
+proc test { style } {
+    global gdb_prompt binfile dp_location
+
+    with_test_prefix "$style" {
+	clean_restart $binfile
+
+	if ![runto_main] {
+	    fail "Can't run to main"
+	    return -1
+	}
+
+	delete_breakpoints
+
+	gdb_test_no_output "set dprintf-style $style"
+
+	# Enable always-inserted so we can control the breakpoint
+	# insertion order.
+	gdb_test_no_output "set breakpoint always-inserted on"
+
+	set test "set dprintf"
+	gdb_test_multiple "dprintf $dp_location, \"y=%d\\n\", y" $test {
+	    -re "cannot run dprintf commands.*$gdb_prompt $" {
+		unsupported $test
+	    }
+	    -re "Dprintf .* at .*$gdb_prompt $" {
+		pass $test
+	    }
+	}
+
+	# In case of agent style, this should force the target to
+	# report the trap to GDB.  IOW, GDB should remove the commands
+	# from the target-side breakpoint.
+	gdb_test "break $dp_location" ".*" "set breakpoint"
+
+	gdb_test "continue" "set dprintf here.*"
+    }
+}
+
+test "gdb"
+test "agent"