2010-02-22 Pedro Alves <pedro@codesourcery.com>

	PR9605

	gdb/
	* breakpoint.c (insert_bp_location): If inserting the read
	watchpoint failed, fallback to an access watchpoint.
	(bpstat_check_watchpoint): Stop for read watchpoint triggers even
	if the value changed, if not watching the same memory for writes.
	(watchpoint_locations_match): Add comment.
	(update_global_location_list): Copy the location's watchpoint type.
	* i386-nat.c (i386_length_and_rw_bits): It's an internal error to
	handle read watchpoints here.
	(i386_insert_watchpoint): Read watchpoints aren't supported.
	* remote.c (remote_insert_watchpoint): Return 1 for unsupported
	packets.
	* target.h (target_insert_watchpoint): Update description.

2010-02-22  Pedro Alves  <pedro@codesourcery.com>

	PR9605

	gdbserver/
	* i386-low.c (i386_length_and_rw_bits): Throw a fatal error if
	handing a read watchpoint.
	(i386_low_insert_watchpoint): Read watchpoints aren't supported.

2010-02-22  Pedro Alves  <pedro@codesourcery.com>

	PR9605

	gdb/testsuite/
	* gdb.base/watch-read.c, gdb.base/watch-read.exp: New files.

3 files changed, 148 insertions, 0 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 995ac27..7010553 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2010-02-22  Pedro Alves  <pedro@codesourcery.com>
+
+	PR9605
+
+	* gdb.base/watch-read.c, gdb.base/watch-read.exp: New files.
+
 2010-02-19  Tom Tromey  <tromey@redhat.com>
 
 	PR c++/8693, PR c++/9496:
diff --git a/gdb/testsuite/gdb.base/watch-read.c b/gdb/testsuite/gdb.base/watch-read.c
new file mode 100644
index 0000000..27c8703
--- /dev/null
+++ b/gdb/testsuite/gdb.base/watch-read.c
@@ -0,0 +1,33 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2009, 2010 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/>.  */
+
+volatile int global;
+
+int
+main (void)
+{
+  int foo = -1;
+
+  while (1)
+    {
+      foo = global; /* read line */
+
+      global = foo + 1; /* write line */
+    }
+
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/watch-read.exp b/gdb/testsuite/gdb.base/watch-read.exp
new file mode 100644
index 0000000..98cab04
--- /dev/null
+++ b/gdb/testsuite/gdb.base/watch-read.exp
@@ -0,0 +1,109 @@
+# This testcase is part of GDB, the GNU debugger.
+
+# Copyright 2010 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/>.
+
+# This file was written by Pedro Alves <pedro@codesourcery.com>
+
+# This file is part of the gdb testsuite.
+
+#
+# Tests involving read watchpoints, and other kinds of watchpoints
+# watching the same memory as read watchpoints.
+#
+
+set testfile "watch-read"
+set srcfile ${testfile}.c
+
+if { [target_info exists gdb,no_hardware_watchpoints] } {
+    untested ${testfile}.exp
+    return -1
+}
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] } {
+    untested ${testfile}.exp
+    return -1
+}
+
+if { ![runto main] } then {
+    fail "run to main"
+    return
+}
+
+set read_line [gdb_get_line_number "read line" $srcfile]
+
+# Test running to a read of `global', with a read watchpoint set
+# watching it.
+
+gdb_test "rwatch global" \
+    "Hardware read watchpoint .*: global" \
+    "set hardware read watchpoint on global variable"
+
+# The first read is on entry to the loop.
+
+gdb_test "continue" \
+    "read watchpoint .*: global.*.*Value = 0.*in main.*$srcfile:$read_line.*" \
+    "read watchpoint triggers on first read"
+
+# The second read happens on second loop iteration, after `global'
+# having been incremented.  On architectures where gdb has to emulate
+# read watchpoints with access watchpoints, this tests the
+# only-report-if-value-changed logic.  On targets that support real
+# read watchpoints, this tests that GDB ignores the watchpoint's old
+# value, knowing that some untrapped write could have changed it, and
+# so reports the read watchpoint unconditionally.
+
+gdb_test "continue" \
+    "read watchpoint .*: global.*.*Value = 1.*in main.*$srcfile:$read_line.*" \
+    "read watchpoint triggers on read after value changed"
+
+# The following tests check that when the user sets a write or access
+# watchpoint watching the same memory as a read watchpoint, GDB also
+# applies the only-report-if-value-changed logic even on targets that
+# support real read watchpoints.
+
+# The program should be stopped at the read line.  Set a write
+# watchpoint (leaving the read watchpoint) and continue.  Only the
+# write watchpoint should be reported as triggering.
+
+gdb_test "watch global" \
+    "atchpoint .*: global" \
+    "set write watchpoint on global variable"
+
+gdb_test "continue" \
+    "atchpoint .*: global.*Old value = 1.*New value = 2.*" \
+    "write watchpoint triggers"
+
+set exp ""
+set exp "${exp}2.*read watchpoint.*keep y.*global.*breakpoint already hit 2 times.*"
+set exp "${exp}3.*watchpoint.*keep y.*global.*breakpoint already hit 1 time.*"
+gdb_test "info watchpoints" \
+    "$exp" \
+    "only write watchpoint triggers when value changes"
+
+# The program is now stopped at the write line.  Continuing should
+# stop at the read line, and only the read watchpoint should be
+# reported as triggering.
+
+gdb_test "continue" \
+    "read watchpoint .*: global.*Value = 2.*in main.*$srcfile:$read_line.*" \
+    "read watchpoint triggers when value doesn't change, trapping reads and writes"
+
+set exp ""
+set exp "${exp}2.*read watchpoint.*keep y.*global.*breakpoint already hit 3 times.*"
+set exp "${exp}3.*watchpoint.*keep y.*global.*breakpoint already hit 1 time.*"
+gdb_test "info watchpoints" \
+    "$exp" \
+    "only read watchpoint triggers when value doesn't change"