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From: Johnson Sun <j3.soon777@gmail.com>
To: LancelotSIX <lsix@lancelotsix.com>, gdb-patches@sourceware.org
Subject: Re: [PING^3] [PATCH v3] [PR python/29603] Disable out-of-scope watchpoints
Date: Mon, 5 Dec 2022 00:45:38 +0800	[thread overview]
Message-ID: <23ce74fe-1d98-8b22-85f9-9b825c81b66d@gmail.com> (raw)
In-Reply-To: <4fc32997-d555-1aeb-1b57-fce152a33540@gmail.com>

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

Johnson

On 11/25/2022 11:11 PM, Johnson Sun wrote:
> 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:[~2022-12-04 16:45 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           ` [PING^2] " Johnson Sun
2022-12-04 16:45             ` Johnson Sun [this message]
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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