[PATCH v3] [PR python/18655] Fix deletion of FinishBreakpoints

[Johnson Sun <j3.soon777@gmail.com>]

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         | 43 +++++++++++++++++++
 .../py-finish-breakpoint-deletion.py          | 33 ++++++++++++++
 4 files changed, 108 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..f09f58861e8
--- /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/>.  */
+
+int
+subroutine (int a)
+{
+  return a;
+}
+
+int
+main ()
+{
+  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..25919900a59
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.exp
@@ -0,0 +1,43 @@
+# 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/>.
+
+# This file is part of the GDB testsuite.  It checks FinishBreakpoints
+# are deleted after used.
+
+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
+}
+
+#
+# Check FinishBreakpoints are deleted after used
+#
+
+gdb_test "python print (len(gdb.breakpoints()))" "1" "check default BP count"
+gdb_test "source ${srcdir}/${subdir}/${testfile}.py" ".*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..f207d0bd2bf
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-finish-breakpoint-deletion.py
@@ -0,0 +1,33 @@
+# 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/>.
+
+# This file is part of the GDB testsuite.  It checks FinishBreakpoints
+# are deleted after used.
+
+
+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")
-- 
2.34.1

base-commit: c99b2113a478a075e8d8f7c3848a92f1ce73f847