1 files changed, 109 insertions, 0 deletions
diff --git a/gdb/testsuite/gdb.python/py-inferior-leak.py b/gdb/testsuite/gdb.python/py-inferior-leak.py
new file mode 100644
index 0000000..914fb3e
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-inferior-leak.py
@@ -0,0 +1,109 @@
+# Copyright (C) 2021 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/>.
+
+import tracemalloc
+import gdb
+import re
+
+# A global variable in which we store a reference to the gdb.Inferior
+# object sent to us in the new_inferior event.
+inf = None
+
+# Register the new_inferior event handler.
+def new_inferior_handler(event):
+    global inf
+    inf = event.inferior
+
+
+gdb.events.new_inferior.connect(new_inferior_handler)
+
+# A global filters list, we only care about memory allocations
+# originating from this script.
+filters = [tracemalloc.Filter(True, "*py-inferior-leak.py")]
+
+# Add a new inferior, and return the number of the new inferior.
+def add_inferior():
+    output = gdb.execute("add-inferior", False, True)
+    m = re.search(r"Added inferior (\d+)", output)
+    if m:
+        num = int(m.group(1))
+    else:
+        raise RuntimeError("no match")
+    return num
+
+
+# Run the test.  When CLEAR is True we clear the global INF variable
+# before comparing the before and after memory allocation traces.
+# When CLEAR is False we leave INF set to reference the gdb.Inferior
+# object, thus preventing the gdb.Inferior from being deallocated.
+def test(clear):
+    global filters, inf
+
+    # Start tracing, and take a snapshot of the current allocations.
+    tracemalloc.start()
+    snapshot1 = tracemalloc.take_snapshot()
+
+    # Create an inferior, this triggers the new_inferior event, which
+    # in turn holds a reference to the new gdb.Inferior object in the
+    # global INF variable.
+    num = add_inferior()
+    gdb.execute("remove-inferiors %s" % num)
+
+    # Possibly clear the global INF variable.
+    if clear:
+        inf = None
+
+    # Now grab a second snapshot of memory allocations, and stop
+    # tracing memory allocations.
+    snapshot2 = tracemalloc.take_snapshot()
+    tracemalloc.stop()
+
+    # Filter the snapshots; we only care about allocations originating
+    # from this file.
+    snapshot1 = snapshot1.filter_traces(filters)
+    snapshot2 = snapshot2.filter_traces(filters)
+
+    # Compare the snapshots, this leaves only things that were
+    # allocated, but not deallocated since the first snapshot.
+    stats = snapshot2.compare_to(snapshot1, "traceback")
+
+    # Total up all the deallocated things.
+    total = 0
+    for stat in stats:
+        total += stat.size_diff
+    return total
+
+
+# The first time we run this some global state will be allocated which
+# shows up as memory that is allocated, but not released.  So, run the
+# test once and discard the result.
+test(True)
+
+# Now run the test twice, the first time we clear our global reference
+# to the gdb.Inferior object, which should allow Python to deallocate
+# the object.  The second time we hold onto the global reference,
+# preventing Python from performing the deallocation.
+bytes_with_clear = test(True)
+bytes_without_clear = test(False)
+
+# The bug that used to exist in GDB was that even when we released the
+# global reference the gdb.Inferior object would not be deallocated.
+if bytes_with_clear > 0:
+    raise gdb.GdbError("memory leak when gdb.Inferior should be released")
+if bytes_without_clear == 0:
+    raise gdb.GdbError("gdb.Inferior object is no longer allocated")
+
+# Print a PASS message that the test script can see.
+print("PASS")