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From: Johnson Sun <j3.soon777@gmail.com>
To: LancelotSIX <lsix@lancelotsix.com>, gdb-patches@sourceware.org
Subject: [PING^2] [PATCH v3] [PR python/29603] Disable out-of-scope watchpoints
Date: Fri, 25 Nov 2022 23:11:33 +0800	[thread overview]
Message-ID: <4fc32997-d555-1aeb-1b57-fce152a33540@gmail.com> (raw)
In-Reply-To: <e574e661-7170-093c-9eea-fcf7827e37f5@gmail.com>

Ping for: 
<https://sourceware.org/pipermail/gdb-patches/2022-October/192909.html>.

Johnson

On 11/18/2022 8:17 PM, JohnsonSun wrote:
> Ping for: 
> <https://sourceware.org/pipermail/gdb-patches/2022-October/192909.html>.
>
> Johnson
>
> On 10/21/2022 2:11 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.
>>
>> Two other solutions seem to solve this issue, but are in fact 
>> inappropriate:
>> 1. Automatically delete breakpoints on all kinds of stops
>>     (in `fetch_inferior_event'). This solution is very slow since the 
>> deletion
>>     requires O(N) time for N breakpoints.
>> 2. Disable the watchpoint after the watchpoint's disposition is set to
>>     `delete at next stop' (in `watchpoint_del_at_next_stop'). This 
>> solution
>>     modifies a non-extension-related code path, and isn't preferred 
>> since this
>>     issue cannot occur without extension languages. (gdb scripts 
>> always normal
>>     stop before continuing execution)
>>
>> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29603
>> ---
>>   gdb/breakpoint.c                           |  2 +
>>   gdb/testsuite/gdb.python/py-watchpoint.c   | 27 ++++++++++++
>>   gdb/testsuite/gdb.python/py-watchpoint.exp | 48 ++++++++++++++++++++++
>>   gdb/testsuite/gdb.python/py-watchpoint.py  | 30 ++++++++++++++
>>   4 files changed, 107 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 bff3bac7d1a..15f4ae2131c 100644
>> --- a/gdb/breakpoint.c
>> +++ b/gdb/breakpoint.c
>> @@ -5340,6 +5340,8 @@ bpstat_check_breakpoint_conditions (bpstat *bs, 
>> thread_info *thread)
>>     /* Evaluate extension language breakpoints that have a "stop" method
>>        implemented.  */
>>     bs->stop = breakpoint_ext_lang_cond_says_stop (b);
>> +  if (b->disposition == disp_del_at_next_stop)
>> +    disable_breakpoint(b);
>>       if (is_watchpoint (b))
>>       {
>> diff --git a/gdb/testsuite/gdb.python/py-watchpoint.c 
>> b/gdb/testsuite/gdb.python/py-watchpoint.c
>> new file mode 100644
>> index 00000000000..4e1760bb05b
>> --- /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 
>> <http://www.gnu.org/licenses/>.  */
>> +
>> +#include <stdio.h>
>> +
>> +int
>> +main (void)
>> +{
>> +  int i;
>> +  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 00000000000..ac58d75c523
>> --- /dev/null
>> +++ b/gdb/testsuite/gdb.python/py-watchpoint.exp
>> @@ -0,0 +1,48 @@
>> +# 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 <http://www.gnu.org/licenses/>.
>> +
>> +# 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 "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: ."
>> +    "\[\r\n\]+Watchpoint . deleted because the program has left the 
>> block in"
>> +    "\[\r\n\]+which its expression is valid\."
>> +    "Watchpoint Hit: ."
>> +    "\[\r\n\]+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 00000000000..ce5dee118ad
>> --- /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 <http://www.gnu.org/licenses/>.
>> +
>> +
>> +class MyBreakpoint(gdb.Breakpoint):
>> +    def __init__(self, *args, **kwargs):
>> +        gdb.Breakpoint.__init__(self, *args, **kwargs)
>> +        self.i = 0
>> +
>> +    def stop(self):
>> +        self.i += 1
>> +        print("Watchpoint Hit:", self.i)
>> +        return False
>> +
>> +
>> +MyBreakpoint("i", gdb.BP_WATCHPOINT)
>> +
>> +print("Python script imported")
>

  reply	other threads:[~2022-11-25 15:11 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-25  5:33 [PATCH] [PR python/29603] Fix deletion of Watchpoints Johnson Sun
2022-09-25 18:10 ` Lancelot SIX
2022-10-01  5:20 ` Johnson Sun
2022-10-01  5:27   ` [PATCH v2] [PR python/29603] Disable out-of-scope watchpoints Johnson Sun
2022-10-20 17:57     ` Johnson Sun
2022-10-20 18:11       ` [PATCH v3] " Johnson Sun
2022-11-18 12:17         ` [PING] " Johnson Sun
2022-11-25 15:11           ` Johnson Sun [this message]
2022-12-04 16:45             ` [PING^3] " Johnson Sun
2022-12-12 21:44               ` [PING^4] " Johnson Sun
2022-12-20 22:08                 ` [PING^5] " Johnson Sun
2022-12-27 16:40                   ` [PING^6] " Johnson Sun
2023-01-12 18:34                     ` [PING^7] " Johnson Sun
2023-01-13 15:40         ` Simon Marchi
2023-01-23 10:15           ` Johnson Sun
2023-02-18 16:26             ` [PING] " Johnson Sun
2023-02-26  6:16               ` [RFC] " Johnson Sun
2023-03-12 17:24                 ` [PING] " Johnson Sun
2023-03-13 16:00             ` Simon Marchi
2023-03-23 18:25               ` Johnson Sun
2023-03-23 18:31                 ` [PATCH v4] " Johnson Sun
2023-04-09 20:47                   ` Johnson Sun
2023-04-09 20:49                     ` [PING] " Johnson Sun
2023-04-17 18:18                       ` [PING^2] " Johnson Sun
2023-04-17 18:56                   ` Simon Marchi
2023-04-23  9:46                     ` Johnson Sun
2023-04-23  9:54                       ` [PATCH v5] " Johnson Sun
2023-05-06 19:06                         ` [PING] " Johnson Sun
2023-05-09 18:50                         ` Simon Marchi
2023-05-10 17:22                           ` Johnson Sun
2023-05-11  2:08                             ` Simon Marchi
2023-05-11 15:46                               ` [PATCH v6] " Johnson Sun
2023-05-11 16:09                                 ` Simon Marchi
2023-05-11 15:50                               ` [PATCH v5] " Johnson Sun

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