From: Andrew Burgess Date: Sat, 19 Apr 2025 13:41:17 +0000 (+0100) Subject: gdb/python: restructure the existing memory leak tests X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=93c145c2aaf3b85b7c3b7abee029da5438d6732f;p=thirdparty%2Fbinutils-gdb.git gdb/python: restructure the existing memory leak tests We currently have two memory leak tests in gdb.python/ and there's a lot of duplication between these two. In the next commit I'd like to add yet another memory leak test, which would mean a third set of scripts which duplicate the existing two. And three is where I draw the line. This commit factors out the core of the memory leak tests into a new module gdb_leak_detector.py, which can then be imported by each tests's Python file in order to make writing the memory leak tests easier. I've also added a helper function to lib/gdb-python.exp which captures some of the common steps needed in the TCL file in order to run a memory leak test. Finally, I use this new infrastructure to rewrite the two existing memory leak tests. What I considered, but ultimately didn't do, is merge the two memory leak tests into a single TCL script. I did consider this, and for the existing tests this would be possible, but future tests might require different enough setup that this might not be possible for all future tests, and now that we have helper functions in a central location, the each individual test is actually pretty small now, so leaving them separate seemed OK. There should be no change in what is actually being tested after this commit. Approved-By: Tom Tromey --- diff --git a/gdb/testsuite/gdb.python/gdb_leak_detector.py b/gdb/testsuite/gdb.python/gdb_leak_detector.py new file mode 100644 index 00000000000..b0f6d47d27c --- /dev/null +++ b/gdb/testsuite/gdb.python/gdb_leak_detector.py @@ -0,0 +1,120 @@ +# Copyright (C) 2021-2025 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 . + +# Defines a base class, which can be sub-classed, in order to run +# memory leak tests on some aspects of GDB's Python API. See the +# comments on the gdb_leak_detector class for more details. + +import os +import tracemalloc +import gdb + + +# This class must be sub-classed to create a memory leak test. The +# sub-classes __init__ method should call the parent classes __init__ +# method, and the sub-class should override allocate() and +# deallocate(). See the comments on the various methods below for +# more details of required arguments and expected usage. +class gdb_leak_detector: + + # Class initialisation. FILENAME is the file in which the + # sub-class is defined, usually passed as just '__file__'. This + # is used when looking for memory allocations; only allocations in + # FILENAME are considered. + def __init__(self, filename): + self.filters = [tracemalloc.Filter(True, "*" + os.path.basename(filename))] + + # Internal helper function to actually run the test. Calls the + # allocate() method to allocate an object from GDB's Python API. + # When CLEAR is True the object will then be deallocated by + # calling deallocate(), otherwise, deallocate() is not called. + # + # Finally, this function checks for any memory allocatios + # originating from 'self.filename' that have not been freed, and + # returns the total (in bytes) of the memory that has been + # allocated, but not freed. + def _do_test(self, clear): + # Start tracing, and take a snapshot of the current allocations. + tracemalloc.start() + snapshot1 = tracemalloc.take_snapshot() + + # Generate the GDB Python API object by calling the allocate + # method. + self.allocate() + + # Possibly clear the reference to the allocated object. + if clear: + self.deallocate() + + # 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(self.filters) + snapshot2 = snapshot2.filter_traces(self.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 + + # Run the memory leak test. Prints 'PASS' if successful, + # otherwise, raises an exception (of type GdbError). + def run(self): + # 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. + self._do_test(True) + + # Now run the test twice, the first time we clear our global reference + # to the allocated 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 = self._do_test(True) + bytes_without_clear = self._do_test(False) + + # If there are any allocations left over when we cleared the reference + # (and expected deallocation) then this indicates a leak. + if bytes_with_clear > 0: + raise gdb.GdbError("memory leak when object reference was released") + + # If there are no allocations showing when we hold onto a reference, + # then this likely indicates that the testing infrastructure is broken, + # and we're no longer spotting the allocations at all. + if bytes_without_clear == 0: + raise gdb.GdbError("object is unexpectedly not showing as allocated") + + # Print a PASS message that the TCL script can see. + print("PASS") + + # Sub-classes must override this method. Allocate an object (or + # multiple objects) from GDB's Python API. Store references to + # these objects within SELF. + def allocate(self): + raise NotImplementedError("allocate() not implemented") + + # Sub-classes must override this method. Deallocate the object(s) + # allocated by the allocate() method. All that is required is for + # the references created in allocate() to be set to None. + def deallocate(self): + raise NotImplementedError("allocate() not implemented") diff --git a/gdb/testsuite/gdb.python/py-inferior-leak.exp b/gdb/testsuite/gdb.python/py-inferior-leak.exp index 6710f59e9e3..15216ee76b7 100644 --- a/gdb/testsuite/gdb.python/py-inferior-leak.exp +++ b/gdb/testsuite/gdb.python/py-inferior-leak.exp @@ -24,15 +24,5 @@ standard_testfile clean_restart -# Skip this test if the tracemalloc module is not available. -if { ![gdb_py_module_available "tracemalloc"] } { - unsupported "tracemalloc module not available" - return -} - -set pyfile [gdb_remote_download host ${srcdir}/${subdir}/${testfile}.py] - -# Source the Python script, this runs the test (which is written -# completely in Python), and either prints PASS, or throws an -# exception. -gdb_test "source ${pyfile}" "PASS" "source python script" +gdb_py_run_memory_leak_test ${srcdir}/${subdir}/${testfile}.py \ + "gdb.Inferior object deallocates correctly" diff --git a/gdb/testsuite/gdb.python/py-inferior-leak.py b/gdb/testsuite/gdb.python/py-inferior-leak.py index 97837dccb85..38f33c3b78a 100644 --- a/gdb/testsuite/gdb.python/py-inferior-leak.py +++ b/gdb/testsuite/gdb.python/py-inferior-leak.py @@ -14,99 +14,31 @@ # along with this program. If not, see . import re -import tracemalloc +import gdb_leak_detector -import gdb -# A global variable in which we store a reference to the gdb.Inferior -# object sent to us in the new_inferior event. -inf = None +class inferior_leak_detector(gdb_leak_detector.gdb_leak_detector): + def __init__(self): + super().__init__(__file__) + self.inferior = None + self.__handler = lambda event: setattr(self, "inferior", event.inferior) + gdb.events.new_inferior.connect(self.__handler) + def __del__(self): + gdb.events.new_inferior.disconnect(self.__handler) -# Register the new_inferior event handler. -def new_inferior_handler(event): - global inf - inf = event.inferior + def allocate(self): + 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") + gdb.execute("remove-inferiors %s" % num) -gdb.events.new_inferior.connect(new_inferior_handler) + def deallocate(self): + self.inferior = None -# 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") +inferior_leak_detector().run() diff --git a/gdb/testsuite/gdb.python/py-read-memory-leak.exp b/gdb/testsuite/gdb.python/py-read-memory-leak.exp index 0015a573226..9ae5eb8a5eb 100644 --- a/gdb/testsuite/gdb.python/py-read-memory-leak.exp +++ b/gdb/testsuite/gdb.python/py-read-memory-leak.exp @@ -30,15 +30,5 @@ if ![runto_main] { return -1 } -# Skip this test if the tracemalloc module is not available. -if { ![gdb_py_module_available "tracemalloc"] } { - unsupported "tracemalloc module not available" - return -} - -set pyfile [gdb_remote_download host ${srcdir}/${subdir}/${testfile}.py] - -# Source the Python script, this runs the test (which is written -# completely in Python), and either prints PASS, or throws an -# exception. -gdb_test "source ${pyfile}" "PASS" "source python script" +gdb_py_run_memory_leak_test ${srcdir}/${subdir}/${testfile}.py \ + "buffers returned by read_memory() deallocates correctly" diff --git a/gdb/testsuite/gdb.python/py-read-memory-leak.py b/gdb/testsuite/gdb.python/py-read-memory-leak.py index 348403d8494..71edf47e7dc 100644 --- a/gdb/testsuite/gdb.python/py-read-memory-leak.py +++ b/gdb/testsuite/gdb.python/py-read-memory-leak.py @@ -13,81 +13,21 @@ # You should have received a copy of the GNU General Public License # along with this program. If not, see . -import os -import tracemalloc +import gdb_leak_detector -import gdb -# A global variable in which we store a reference to the memory buffer -# returned from gdb.Inferior.read_memory(). -mem_buf = None +class read_leak_detector(gdb_leak_detector.gdb_leak_detector): + def __init__(self): + super().__init__(__file__) + self.mem_buf = None + self.addr = gdb.parse_and_eval("px") + self.inf = gdb.inferiors()[0] + def allocate(self): + self.mem_buf = self.inf.read_memory(self.addr, 4096) -# A global filters list, we only care about memory allocations -# originating from this script. -filters = [tracemalloc.Filter(True, "*" + os.path.basename(__file__))] + def deallocate(self): + self.mem_buf = None -# 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") +read_leak_detector().run() diff --git a/gdb/testsuite/lib/gdb-python.exp b/gdb/testsuite/lib/gdb-python.exp index b4eb40dfcec..e026c1bc857 100644 --- a/gdb/testsuite/lib/gdb-python.exp +++ b/gdb/testsuite/lib/gdb-python.exp @@ -77,3 +77,24 @@ proc gdb_py_module_available { name } { return ${available} } + +# Run a memory leak test within the Python script FILENAME. This proc +# checks that the required Python modules are available, sets up the +# syspath so that the helper module can be found (in the same +# directory as FILENAME), then loads FILENAME to run the test. +proc gdb_py_run_memory_leak_test { filename testname } { + if { ![gdb_py_module_available "tracemalloc"] } { + unsupported "$testname (tracemalloc module not available)" + } + + gdb_test_no_output -nopass "python import sys" + gdb_test_no_output -nopass \ + "python sys.path.insert(0, \"[file dirname $filename]\")" \ + "setup sys.path" + + set pyfile [gdb_remote_download host ${filename}] + + # Source the Python script, this runs the test, and either prints + # PASS, or throws an exception. + gdb_test "source ${pyfile}" "^PASS" $testname +}