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[61.220.36.70]) by smtp.gmail.com with ESMTPSA id o35-20020a635a23000000b00519c3475f21sm707954pgb.46.2023.04.09.13.47.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 09 Apr 2023 13:47:08 -0700 (PDT) Message-ID: Date: Mon, 10 Apr 2023 04:47:05 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.9.1 Subject: Re: [PATCH v4] [PR python/29603] Disable out-of-scope watchpoints To: SimonMarchi , Lancelot SIX , gdb-patches@sourceware.org References: <0e614d96-52dc-6e14-ea23-8aca19c5414c@gmail.com> <20230323183118.3172-1-j3.soon777@gmail.com> Content-Language: en-US From: Johnson Sun In-Reply-To: <20230323183118.3172-1-j3.soon777@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-13.1 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_ENVFROM_END_DIGIT,FREEMAIL_FROM,GIT_PATCH_0,KAM_SHORT,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Ping for: Johnson On 3/24/2023 2:31 AM, Johnson Sun wrote: > Currently, when a local software watchpoint goes out of scope, GDB sets > the watchpoint's disposition to `delete at next stop' and then normal > stops (i.e., stop and wait for the next GDB command). When GDB normal > stops, it automatically deletes the breakpoints with their disposition > set to `delete at next stop'. > > Suppose a Python script decides not to normal stop when a local > software watchpoint goes out of scope, the watchpoint will not be > automatically deleted even when its disposition is set to > `delete at next stop'. > > Since GDB single-steps the program and tests the watched expression > after each instruction, not deleting the watchpoint causes the > watchpoint to be hit many more times than it should, as reported in > PR python/29603. > > This was happening because the watchpoint is not deleted or disabled > when going out of scope. > > This commit fixes this issue by disabling the watchpoint when going out > of scope. It also adds a test to ensure this feature isn't regressed in > the future. > > Calling `breakpoint_auto_delete' on all kinds of stops (in > `fetch_inferior_event') seem to solve this issue, but is in fact > inappropriate, since `breakpoint_auto_delete' goes over all breakpoints > instead of just going through the bpstat chain (which only contains the > breakpoints that were hit right now). > > Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29603 > --- > gdb/breakpoint.c | 1 + > gdb/testsuite/gdb.python/py-watchpoint.c | 27 +++++++++++ > gdb/testsuite/gdb.python/py-watchpoint.exp | 54 ++++++++++++++++++++++ > gdb/testsuite/gdb.python/py-watchpoint.py | 30 ++++++++++++ > 4 files changed, 112 insertions(+) > create mode 100644 gdb/testsuite/gdb.python/py-watchpoint.c > create mode 100644 gdb/testsuite/gdb.python/py-watchpoint.exp > create mode 100644 gdb/testsuite/gdb.python/py-watchpoint.py > > diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c > index bff3bac7d1..47dcf1e127 100644 > --- a/gdb/breakpoint.c > +++ b/gdb/breakpoint.c > @@ -1832,6 +1832,7 @@ watchpoint_del_at_next_stop (struct watchpoint *w) > w->related_breakpoint = w; > } > w->disposition = disp_del_at_next_stop; > + disable_breakpoint (w); > } > > /* Extract a bitfield value from value VAL using the bit parameters contained in > diff --git a/gdb/testsuite/gdb.python/py-watchpoint.c b/gdb/testsuite/gdb.python/py-watchpoint.c > new file mode 100644 > index 0000000000..0c58b31647 > --- /dev/null > +++ b/gdb/testsuite/gdb.python/py-watchpoint.c > @@ -0,0 +1,27 @@ > +/* This testcase is part of GDB, the GNU debugger. > + > + Copyright 2022 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 . */ > + > +#include > + > +int > +main (void) > +{ > + int i = -1; > + for (i = 0; i < 3; i++) > + printf ("%d", i); > + return 0; > +} > diff --git a/gdb/testsuite/gdb.python/py-watchpoint.exp b/gdb/testsuite/gdb.python/py-watchpoint.exp > new file mode 100644 > index 0000000000..5504736629 > --- /dev/null > +++ b/gdb/testsuite/gdb.python/py-watchpoint.exp > @@ -0,0 +1,54 @@ > +# Copyright (C) 2022 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 . > + > +# Check that Watchpoints are deleted after use. > + > +load_lib gdb-python.exp > + > +standard_testfile > + > +if {[prepare_for_testing "failed to prepare" $testfile $srcfile]} { > + return -1 > +} > + > +# Skip all tests if Python scripting is not enabled. > +if { [skip_python_tests] } { continue } > + > +if ![runto_main] then { > + return 0 > +} > + > +# For remote host testing > +set pyfile [gdb_remote_download host ${srcdir}/${subdir}/${testfile}.py] > + > +gdb_test_no_output "set can-use-hw-watchpoints 0" "don't use hardware watchpoints" > +gdb_test "break 24" ".*" "set breakpoint before loop" > +gdb_test "continue" ".*" "run until reaching loop" > +gdb_test "clear" ".*" "delete the breakpoint before loop" > +gdb_test "python print(len(gdb.breakpoints()))" "1" "check default BP count" > +gdb_test "source $pyfile" ".*Python script imported.*" \ > + "import python scripts" > +gdb_test "python print(len(gdb.breakpoints()))" "2" "check modified BP count" > +gdb_test_sequence "continue" "run until program stops" { > + "Watchpoint Hit: 1" > + "Watchpoint Hit: 2" > + "Watchpoint Hit: 3" > + "Watchpoint Hit: 4" > + "Watchpoint 3 deleted because the program has left the block in" > + "which its expression is valid\." > + "Watchpoint Hit: 5" > + "012\\[Inferior 1 \\(process .*\\) exited normally\\]" > +} > +gdb_test "python print(len(gdb.breakpoints()))" "1" "check BP count" > diff --git a/gdb/testsuite/gdb.python/py-watchpoint.py b/gdb/testsuite/gdb.python/py-watchpoint.py > new file mode 100644 > index 0000000000..c5fae00e93 > --- /dev/null > +++ b/gdb/testsuite/gdb.python/py-watchpoint.py > @@ -0,0 +1,30 @@ > +# Copyright (C) 2022 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 . > + > + > +class MyBreakpoint(gdb.Breakpoint): > + def __init__(self, *args, **kwargs): > + gdb.Breakpoint.__init__(self, *args, **kwargs) > + self.n = 0 > + > + def stop(self): > + self.n += 1 > + print("Watchpoint Hit:", self.n, flush=True) > + return False > + > + > +MyBreakpoint("i", gdb.BP_WATCHPOINT) > + > +print("Python script imported")