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# Copyright (C) 2024 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 os
import tracemalloc
import gdb
# A global variable in which we store a reference to the memory buffer
# returned from gdb.Inferior.read_memory().
mem_buf = None
# A global filters list, we only care about memory allocations
# originating from this script.
filters = [tracemalloc.Filter(True, "*" + os.path.basename(__file__))]
# 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, mem_buf
addr = gdb.parse_and_eval("px")
inf = gdb.inferiors()[0]
# Start tracing, and take a snapshot of the current allocations.
tracemalloc.start()
snapshot1 = tracemalloc.take_snapshot()
# Read from the inferior, this allocate a memory buffer object.
mem_buf = inf.read_memory(addr, 4096)
# Possibly clear the global INF variable.
if clear:
mem_buf = 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 allocated 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 memory buffer 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 memory buffer should be released")
if bytes_without_clear == 0:
raise gdb.GdbError("memory buffer object is no longer allocated")
# Print a PASS message that the test script can see.
print("PASS")
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