From: Pedro Alves <pedro@palves.net>
To: Kevin Buettner <kevinb@redhat.com>, gdb-patches@sourceware.org
Cc: simark@simark.ca, tdevries@suse.de
Subject: Re: [PATCH v4 8/8] Forced quit cases handled by resetting sync_quit_force_run
Date: Mon, 30 Jan 2023 19:02:23 +0000 [thread overview]
Message-ID: <6c35f63b-5eda-20ea-126f-4e5390710a0c@palves.net> (raw)
In-Reply-To: <20230112015630.32999-9-kevinb@redhat.com>
On 2023-01-12 1:56 a.m., Kevin Buettner wrote:
> During my audit of the use of gdb_exception with regard to QUIT
> processing, I found a try/catch in the scoped_switch_fork_info
> destructor.
>
> Static analysis found this call path from the destructor to
> maybe_quit():
>
> scoped_switch_fork_info::~scoped_switch_fork_info()
> -> remove_breakpoints()
> -> remove_breakpoint(bp_location*)
> -> remove_breakpoint_1(bp_location*, remove_bp_reason)
> -> memory_validate_breakpoint(gdbarch*, bp_target_info*)
> -> target_read_memory(unsigned long, unsigned char*, long)
> -> target_read(target_ops*, target_object, char const*, unsigned char*, unsigned long, long)
> -> maybe_quit()
>
> Since it's not safe to do a 'throw' from a destructor, we simply
> call set_quit_flag and, for gdb_exception_forced_quit, also
> set sync_quit_force_run. This will cause the appropriate
> exception to be rethrown at the next QUIT check.
>
> Another case is the try / catch in tui_getc() in tui-io.c. The
> existing catch swallows the exception. I've added a catch for
> 'gdb_exception_forced_quit', which also swallows the exception,
> but also sets sync_quit_force_run and calls set_quit_flag in
> order to restart forced quit processing at the next QUIT check.
> This is required because it isn't safe to throw into/through
> readline.
>
> Thanks to Pedro Alves for suggesting this idea.
>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=26761
> ---
> gdb/linux-fork.c | 13 +++++++++++++
> gdb/tui/tui-io.c | 9 +++++++++
> 2 files changed, 22 insertions(+)
>
> diff --git a/gdb/linux-fork.c b/gdb/linux-fork.c
> index 61545b859ea..fc2f00d0766 100644
> --- a/gdb/linux-fork.c
> +++ b/gdb/linux-fork.c
> @@ -430,6 +430,19 @@ class scoped_switch_fork_info
> fork_load_infrun_state (m_oldfp);
> insert_breakpoints ();
> }
> + catch (const gdb_exception_quit &ex)
> + {
> + /* We can't throw from a destructor, so re-set the quit flag
> + for later QUIT checking. */
> + set_quit_flag ();
> + }
> + catch (const gdb_exception_forced_quit &ex)
> + {
> + /* Like above, but (eventually) cause GDB to terminate by
> + setting sync_quit_force_run. */
> + sync_quit_force_run = 1;
> + set_quit_flag ();
I think it'd be nice if we had a function that did both of these for us.
Something like "set_force_quit_flag()".
> + }
> catch (const gdb_exception &ex)
> {
> warning (_("Couldn't restore checkpoint state in %s: %s"),
> diff --git a/gdb/tui/tui-io.c b/gdb/tui/tui-io.c
> index 2f39e34df2f..ac3c7296499 100644
> --- a/gdb/tui/tui-io.c
> +++ b/gdb/tui/tui-io.c
> @@ -1275,6 +1275,15 @@ tui_getc (FILE *fp)
> {
> return tui_getc_1 (fp);
> }
> + catch (const gdb_exception_forced_quit &ex)
> + {
> + /* As noted below, it's not safe to let an exception escape
> + to newline, so, for this case, reset the quit flag for
Spurious double space before "reset".
> + later QUIT checking. */
> + sync_quit_force_run = 1;
> + set_quit_flag ();
> + return 0;
> + }
> catch (const gdb_exception &ex)
> {
> /* Just in case, don't ever let an exception escape to readline.
>
next prev parent reply other threads:[~2023-01-30 19:02 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-12 1:56 [PATCH v4 0/8] Fix gdb.base/gdb-sigterm.exp failure/error Kevin Buettner
2023-01-12 1:56 ` [PATCH v4 1/8] Introduce gdb_exception_forced_quit Kevin Buettner
2023-01-30 18:56 ` Pedro Alves
2023-01-12 1:56 ` [PATCH v4 2/8] Handle gdb SIGTERM by throwing / catching gdb_exception_force_quit Kevin Buettner
2023-01-30 18:57 ` Pedro Alves
2023-01-12 1:56 ` [PATCH v4 3/8] Catch gdb_exception_error instead of gdb_exception (in many places) Kevin Buettner
2023-01-30 19:00 ` Pedro Alves
2023-02-16 10:52 ` Pedro Alves
2023-01-12 1:56 ` [PATCH v4 4/8] Python QUIT processing updates Kevin Buettner
2023-01-30 19:01 ` Pedro Alves
2023-02-20 2:52 ` Kevin Buettner
2023-02-23 12:50 ` Pedro Alves
2023-01-12 1:56 ` [PATCH v4 5/8] Guile " Kevin Buettner
2023-01-12 1:56 ` [PATCH v4 6/8] Call quit_force for gdb_exception_forced_quit in safe_execute_command Kevin Buettner
2023-01-30 19:01 ` Pedro Alves
2023-01-12 1:56 ` [PATCH v4 7/8] QUIT processing w/ explicit throw for gdb_exception_forced_quit Kevin Buettner
2023-01-30 19:02 ` Pedro Alves
2023-01-12 1:56 ` [PATCH v4 8/8] Forced quit cases handled by resetting sync_quit_force_run Kevin Buettner
2023-01-30 19:02 ` Pedro Alves [this message]
2023-01-12 12:37 ` [PATCH v4 0/8] Fix gdb.base/gdb-sigterm.exp failure/error Tom de Vries
2023-01-27 22:03 ` Kevin Buettner
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