binutils-gdb/gdb/testsuite/gdb.base/watch-read.exp

# This testcase is part of GDB, the GNU debugger.

# Copyright 2010-2020 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 is part of the gdb testsuite.

#
# Tests involving read watchpoints, and other kinds of watchpoints
# watching the same memory as read watchpoints.
#

standard_testfile .c

if {[skip_hw_watchpoint_access_tests]} {
    return 0
}

if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
    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"