[PING][PATCH v2 1/1] gdb, breakpoint: add a destructor to the watchpoint struct

[Bouhaouel, Mohamed]

Dear all,

I kindly request that you review this patch.

Thanks,
-Mohamed

> -----Original Message-----
> From: Gdb-patches <gdb-patches-
> bounces+felix.willgerodt=intel.com@sourceware.org> On Behalf Of Mohamed
> Bouhaouel via Gdb-patches
> Sent: Wednesday, April 5, 2023 3:35 PM
> To: gdb-patches@sourceware.org
> Cc: tom@tromey.com; aburgess@redhat.com
> Subject: [PATCH v2 1/1] gdb, breakpoint: add a destructor to the watchpoint
> struct
> 
> Make sure to unlink the related breakpoint when the watchpoint instance
> is deleted.  This prevents having a wp-related breakpoint that is
> linked to a NULL watchpoint (e.g.  the watchpoint instance is being
> deleted when the 'watch' command fails).  With the below scenario,
> having such a left out breakpoint will lead to a GDB hang, and this
> is due to an infinite loop when deleting all inferior breakpoints.
> 
> Scenario:
> 	(gdb) set can-use-hw-watchpoints 0
> 	(gdb) awatch <SCOPE VAR>
> 	Can't set read/access watchpoint when hardware watchpoints are
> disabled.
> 	(gdb) rwatch <SCOPE VAR>
> 	Can't set read/access watchpoint when hardware watchpoints are
> disabled.
> 	(gdb) <continue the program until the end>
> 	>> HANG <<
> 
> Signed-off-by: Mohamed Bouhaouel <mohamed.bouhaouel@intel.com>
> ---
>  gdb/breakpoint.c                              | 15 +++++++
>  gdb/breakpoint.h                              |  3 ++
>  .../gdb.base/scope-hw-watch-disable.c         | 26 ++++++++++++
>  .../gdb.base/scope-hw-watch-disable.exp       | 40 +++++++++++++++++++
>  4 files changed, 84 insertions(+)
>  create mode 100644 gdb/testsuite/gdb.base/scope-hw-watch-disable.c
>  create mode 100644 gdb/testsuite/gdb.base/scope-hw-watch-disable.exp
> 
> diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
> index ebe97940f54..862e9a372ab 100644
> --- a/gdb/breakpoint.c
> +++ b/gdb/breakpoint.c
> @@ -9594,6 +9594,21 @@ break_range_command (const char *arg, int
> from_tty)
>    install_breakpoint (false, std::move (br), true);
>  }
> 
> +/* See breakpoint.h.  */
> +
> +watchpoint::~watchpoint ()
> +{
> +  /* Make sure to unlink the destroyed watchpoint from the related
> +     breakpoint ring.  */
> +
> +  breakpoint *bpt = this;
> +  breakpoint *related = bpt;
> +  while (related->related_breakpoint != bpt)
> +    related = related->related_breakpoint;
> +
> +  related->related_breakpoint = bpt->related_breakpoint;
> +}
> +
>  /*  Return non-zero if EXP is verified as constant.  Returned zero
>      means EXP is variable.  Also the constant detection may fail for
>      some constant expressions and in such case still falsely return
> diff --git a/gdb/breakpoint.h b/gdb/breakpoint.h
> index 7c5cf3f2bef..cccd331e6e8 100644
> --- a/gdb/breakpoint.h
> +++ b/gdb/breakpoint.h
> @@ -933,6 +933,9 @@ struct watchpoint : public breakpoint
>    void print_recreate (struct ui_file *fp) const override;
>    bool explains_signal (enum gdb_signal) override;
> 
> +  /* Destructor for WATCHPOINT.  */
> +  ~watchpoint ();
> +
>    /* String form of exp to use for displaying to the user (malloc'd),
>       or NULL if none.  */
>    gdb::unique_xmalloc_ptr<char> exp_string;
> diff --git a/gdb/testsuite/gdb.base/scope-hw-watch-disable.c
> b/gdb/testsuite/gdb.base/scope-hw-watch-disable.c
> new file mode 100644
> index 00000000000..30956fe1b84
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/scope-hw-watch-disable.c
> @@ -0,0 +1,26 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2023 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/>.  */
> +
> +int
> +main ()
> +{
> +  int a = 0, b = 0;
> +  b = a;
> +  a = b + 10;
> +
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.base/scope-hw-watch-disable.exp
> b/gdb/testsuite/gdb.base/scope-hw-watch-disable.exp
> new file mode 100644
> index 00000000000..54ebb4e4226
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/scope-hw-watch-disable.exp
> @@ -0,0 +1,40 @@
> +# Copyright 2023 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/>.
> +
> +# Test that GDB displays the correct error message when hardware
> watchpoints
> +# are not supported or explicitly disabled.  Test also that GDB terminates
> +# successfully after several attempts to insert a hardware watchpoint.
> +
> +standard_testfile
> +
> +if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile}]} {
> +    return -1
> +}
> +
> +gdb_test_no_output "set can-use-hw-watchpoints 0"
> +
> +if {![runto_main]} {
> +    return -1
> +}
> +
> +gdb_test "awatch a" \
> +    "Can't set read/access watchpoint when hardware watchpoints are
> disabled." \
> +    "unsuccessful attempt to create an access watchpoint"
> +gdb_test "rwatch b" \
> +    "Can't set read/access watchpoint when hardware watchpoints are
> disabled." \
> +    "unsuccessful attempt to create a read watchpoint"
> +
> +# The program continues until termination.
> +gdb_continue_to_end
> --
> 2.25.1
> 
> Intel Deutschland GmbH
> Registered Address: Am Campeon 10, 85579 Neubiberg, Germany
> Tel: +49 89 99 8853-0, www.intel.de <http://www.intel.de>
> Managing Directors: Christin Eisenschmid, Sharon Heck, Tiffany Doon Silva
> Chairperson of the Supervisory Board: Nicole Lau
> Registered Office: Munich
> Commercial Register: Amtsgericht Muenchen HRB 186928

Intel Deutschland GmbH
Registered Address: Am Campeon 10, 85579 Neubiberg, Germany
Tel: +49 89 99 8853-0, www.intel.de <http://www.intel.de>
Managing Directors: Christin Eisenschmid, Sharon Heck, Tiffany Doon Silva  
Chairperson of the Supervisory Board: Nicole Lau
Registered Office: Munich
Commercial Register: Amtsgericht Muenchen HRB 186928