[v4,PR,python/18655] Fix deletion of FinishBreakpoints

  Currently, FinishBreakpoints are set at the return address of a frame based on
the `finish' command, and are meant to be temporary breakpoints. However, they
are not being cleaned up after use, as reported in PR python/18655. This was
happening because the disposition of the breakpoint was not being set
correctly.

This commit fixes this issue by correctly setting the disposition in the
post-stop hook of the breakpoint. It also adds a test to ensure this feature
isn't regressed in the future.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=18655
---
 gdb/python/py-finishbreakpoint.c              |  2 +-
 .../py-finish-breakpoint-deletion.c           | 31 ++++++++++++++
 .../py-finish-breakpoint-deletion.exp         | 41 +++++++++++++++++++
 .../py-finish-breakpoint-deletion.py          | 32 +++++++++++++++
 4 files changed, 105 insertions(+), 1 deletion(-)
 create mode 100644 gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.c
 create mode 100644 gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.exp
 create mode 100644 gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.py
  

Ping for: 
<https://sourceware.org/pipermail/gdb-patches/2022-October/192905.html>.

Johnson

On 10/21/2022 1:49 AM, Johnson Sun wrote:
> Currently, FinishBreakpoints are set at the return address of a frame based on
> the `finish' command, and are meant to be temporary breakpoints. However, they
> are not being cleaned up after use, as reported in PR python/18655. This was
> happening because the disposition of the breakpoint was not being set
> correctly.
>
> This commit fixes this issue by correctly setting the disposition in the
> post-stop hook of the breakpoint. It also adds a test to ensure this feature
> isn't regressed in the future.
>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=18655
> ---
>   gdb/python/py-finishbreakpoint.c              |  2 +-
>   .../py-finish-breakpoint-deletion.c           | 31 ++++++++++++++
>   .../py-finish-breakpoint-deletion.exp         | 41 +++++++++++++++++++
>   .../py-finish-breakpoint-deletion.py          | 32 +++++++++++++++
>   4 files changed, 105 insertions(+), 1 deletion(-)
>   create mode 100644 gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.c
>   create mode 100644 gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.exp
>   create mode 100644 gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.py
>
> diff --git a/gdb/python/py-finishbreakpoint.c b/gdb/python/py-finishbreakpoint.c
> index c80096f6810..d8b1aff0e2b 100644
> --- a/gdb/python/py-finishbreakpoint.c
> +++ b/gdb/python/py-finishbreakpoint.c
> @@ -145,7 +145,7 @@ bpfinishpy_post_stop_hook (struct gdbpy_breakpoint_object *bp_obj)
>       {
>         /* Can't delete it here, but it will be removed at the next stop.  */
>         disable_breakpoint (bp_obj->bp);
> -      gdb_assert (bp_obj->bp->disposition == disp_del);
> +      bp_obj->bp->disposition = disp_del_at_next_stop;
>       }
>     catch (const gdb_exception &except)
>       {
> diff --git a/gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.c b/gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.c
> new file mode 100644
> index 00000000000..b6e71513373
> --- /dev/null
> +++ b/gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.c
> @@ -0,0 +1,31 @@
> +/* 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/>.  */
> +
> +static int
> +subroutine (int a)
> +{
> +  return a;
> +}
> +
> +int
> +main (void)
> +{
> +  int i;
> +  for (i = 0; i < 5; i++)
> +    subroutine (i);
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.exp b/gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.exp
> new file mode 100644
> index 00000000000..cd882cee91d
> --- /dev/null
> +++ b/gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.exp
> @@ -0,0 +1,41 @@
> +# 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 FinishBreakpoints 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 "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 "continue" "Breakpoint.*at.*" "run until FinishBreakpoint stops"
> +gdb_test "python print(len(gdb.breakpoints()))" "2" "check BP count"
> diff --git a/gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.py b/gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.py
> new file mode 100644
> index 00000000000..ab05b0c35a3
> --- /dev/null
> +++ b/gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.py
> @@ -0,0 +1,32 @@
> +# 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 MyFinishBreakpoint(gdb.FinishBreakpoint):
> +    def stop(self):
> +        print("stopped at MyFinishBreakpoint")
> +        return self.return_value == 4
> +
> +
> +class MyBreakpoint(gdb.Breakpoint):
> +    def stop(self):
> +        print("stopped at MyBreakpoint")
> +        MyFinishBreakpoint()
> +        return False
> +
> +
> +MyBreakpoint("subroutine", internal=True)
> +
> +print("Python script imported")
  

On 10/20/22 13:49, Johnson Sun wrote:
> Currently, FinishBreakpoints are set at the return address of a frame based on
> the `finish' command, and are meant to be temporary breakpoints. However, they
> are not being cleaned up after use, as reported in PR python/18655. This was
> happening because the disposition of the breakpoint was not being set
> correctly.
> 
> This commit fixes this issue by correctly setting the disposition in the
> post-stop hook of the breakpoint. It also adds a test to ensure this feature
> isn't regressed in the future.
> 
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=18655

Thanks, I see your copyright assignment is complete.  I pushed the
patch.

Simon