Merge branch 'y/lsan' into next

* y/lsan:
  golang: pychan: Fix memory leak in .from_chan_* pychan <- chan[X] wrappers
  tox: *-asan: Activate LeakSanitizer on recent CPython 3
  tox: Explicitly use -fno-omit-frame-pointer for ASAN/TSAN builds
  tox -= CPython 3.5, 3.6, 3.7
  tox: Tell it that our trun is ok to run

.lsan-ignore.txt

+# .lsan-ignore.txt lists memory leak events that LeakSanitizer should not
+# report when running pygolang tests.
+#
+# Many python allocations, whose lifetime coincides with python interpreter
+# lifetime, and which are not explicitly freed on python shutdown, are
+# reported as leaks by default. Disable leak reporting for those to avoid
+# non-pygolang related printouts.
+
+
+# >>> Everything created when initializing python, e.g. sys.stderr
+#   #0 0x7f21e74f3bd7 in malloc .../asan_malloc_linux.cpp:69
+#   #1 0x555f361ff9a4 in PyThread_allocate_lock Python/thread_pthread.h:385
+#   #2 0x555f3623f72a in _buffered_init Modules/_io/bufferedio.c:725
+#   #3 0x555f3623ff7e in _io_BufferedWriter___init___impl Modules/_io/bufferedio.c:1803
+#   #4 0x555f3623ff7e in _io_BufferedWriter___init__ Modules/_io/clinic/bufferedio.c.h:489
+#   #5 0x555f3610c086 in type_call Objects/typeobject.c:1103
+#   #6 0x555f3609cdcc in _PyObject_MakeTpCall Objects/call.c:214
+#   #7 0x555f3609d6a8 in _PyObject_VectorcallTstate Include/internal/pycore_call.h:90
+#   #8 0x555f3609d6a8 in _PyObject_VectorcallTstate Include/internal/pycore_call.h:77
+#   #9 0x555f3609d6a8 in _PyObject_CallFunctionVa Objects/call.c:536
+#   #10 0x555f3609e89c in _PyObject_CallFunction_SizeT Objects/call.c:590
+#   #11 0x555f3623a0df in _io_open_impl Modules/_io/_iomodule.c:407
+#   #12 0x555f3623a0df in _io_open Modules/_io/clinic/_iomodule.c.h:264
+#   #13 0x555f360f17da in cfunction_vectorcall_FASTCALL_KEYWORDS Objects/methodobject.c:443
+#   #14 0x555f3609d54c in _PyObject_VectorcallTstate Include/internal/pycore_call.h:92
+#   #15 0x555f3609d54c in _PyObject_CallFunctionVa Objects/call.c:536
+#   #16 0x555f3609ec34 in callmethod Objects/call.c:608
+#   #17 0x555f3609ec34 in _PyObject_CallMethod Objects/call.c:677
+#   #18 0x555f361e60cf in create_stdio Python/pylifecycle.c:2244
+#   #19 0x555f361e6523 in init_sys_streams Python/pylifecycle.c:2431
+#   #20 0x555f361e6523 in init_interp_main Python/pylifecycle.c:1154
+#   #21 0x555f361e7204 in pyinit_main Python/pylifecycle.c:1230
+#   #22 0x555f361e85ba in Py_InitializeFromConfig Python/pylifecycle.c:1261
+#   #23 0x555f3621010a in pymain_init Modules/main.c:67
+#   #24 0x555f362113de in pymain_main Modules/main.c:701
+#   #25 0x555f362113de in Py_BytesMain Modules/main.c:734
+leak:^pymain_init$
+
+# >>> Everything created when importing py modules, e.g.
+#   #0 0x7f18c86f3bd7 in malloc .../asan_malloc_linux.cpp:69
+#   #1 0x55b971430acf in PyMem_RawMalloc Objects/obmalloc.c:586
+#   #2 0x55b971430acf in _PyObject_Malloc Objects/obmalloc.c:2003
+#   #3 0x55b971430acf in _PyObject_Malloc Objects/obmalloc.c:1996
+#   #4 0x55b971415696 in new_keys_object Objects/dictobject.c:632
+#   #5 0x55b971415716 in dictresize Objects/dictobject.c:1429
+#   #6 0x55b97141961a in insertion_resize Objects/dictobject.c:1183
+#   #7 0x55b97141961a in insertdict Objects/dictobject.c:1248
+#   #8 0x55b97143eb7b in add_subclass Objects/typeobject.c:6547
+#   #9 0x55b97144ca52 in type_ready_add_subclasses Objects/typeobject.c:6345
+#   #10 0x55b97144ca52 in type_ready Objects/typeobject.c:6476
+#   #11 0x55b971451a1f in PyType_Ready Objects/typeobject.c:6508
+#   #12 0x55b971451a1f in type_new_impl Objects/typeobject.c:3189
+#   #13 0x55b971451a1f in type_new Objects/typeobject.c:3323
+#   #14 0x55b971443014 in type_call Objects/typeobject.c:1091
+#   #15 0x55b9713d3dcc in _PyObject_MakeTpCall Objects/call.c:214
+#   #16 0x55b9713d47bd in _PyObject_FastCallDictTstate Objects/call.c:141
+#   #17 0x55b9713d47bd in PyObject_VectorcallDict Objects/call.c:165
+#   #18 0x55b9714d14c2 in builtin___build_class__ Python/bltinmodule.c:209
+#   #19 0x55b9714287da in cfunction_vectorcall_FASTCALL_KEYWORDS Objects/methodobject.c:443
+#   #20 0x55b9713d4a7b in _PyObject_VectorcallTstate Include/internal/pycore_call.h:92
+#   #21 0x55b9713d4a7b in PyObject_Vectorcall Objects/call.c:299
+#   #22 0x55b97137666e in _PyEval_EvalFrameDefault Python/ceval.c:4769
+#   #23 0x55b9714d7e6b in _PyEval_EvalFrame Include/internal/pycore_ceval.h:73
+#   #24 0x55b9714d7e6b in _PyEval_Vector Python/ceval.c:6434
+#   #25 0x55b9714d7e6b in PyEval_EvalCode Python/ceval.c:1148
+#   #26 0x55b9714d2e1f in builtin_exec_impl Python/bltinmodule.c:1077
+#   #27 0x55b9714d2e1f in builtin_exec Python/clinic/bltinmodule.c.h:465
+#   #28 0x55b9714287da in cfunction_vectorcall_FASTCALL_KEYWORDS Objects/methodobject.c:443
+#   #29 0x55b971376dcb in do_call_core Python/ceval.c:7349
+#   #30 0x55b971376dcb in _PyEval_EvalFrameDefault Python/ceval.c:5376
+#   #31 0x55b9714d7faf in _PyEval_EvalFrame Include/internal/pycore_ceval.h:73
+#   #32 0x55b9714d7faf in _PyEval_Vector Python/ceval.c:6434
+#   #33 0x55b9713d436e in _PyObject_VectorcallTstate Include/internal/pycore_call.h:92
+#   #34 0x55b9713d436e in object_vacall Objects/call.c:819
+#   #35 0x55b9713d63cf in PyObject_CallMethodObjArgs Objects/call.c:879
+#   #36 0x55b9715080e1 in import_find_and_load Python/import.c:1748
+#   #37 0x55b9715080e1 in PyImport_ImportModuleLevelObject Python/import.c:1847
+#   #38 0x55b97137de9c in import_name Python/ceval.c:7422
+#   #39 0x55b97137de9c in _PyEval_EvalFrameDefault Python/ceval.c:3946
+#   #40 0x55b9714d7e6b in _PyEval_EvalFrame Include/internal/pycore_ceval.h:73
+#   #41 0x55b9714d7e6b in _PyEval_Vector Python/ceval.c:6434
+#   #42 0x55b9714d7e6b in PyEval_EvalCode Python/ceval.c:1148
+#   #43 0x55b9714d2e1f in builtin_exec_impl Python/bltinmodule.c:1077
+#   #44 0x55b9714d2e1f in builtin_exec Python/clinic/bltinmodule.c.h:465
+#   #45 0x55b9714287da in cfunction_vectorcall_FASTCALL_KEYWORDS Objects/methodobject.c:443
+#   #46 0x55b971376dcb in do_call_core Python/ceval.c:7349
+#   #47 0x55b971376dcb in _PyEval_EvalFrameDefault Python/ceval.c:5376
+leak:^PyImport_Import
+#  importlib.import_module leads to
+#   #0 0x7f1951ef3bd7 in malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:69
+#   #1 0x55f399e8cacf in PyMem_RawMalloc Objects/obmalloc.c:586
+#   #2 0x55f399e8cacf in _PyObject_Malloc Objects/obmalloc.c:2003
+#   #3 0x55f399e8cacf in _PyObject_Malloc Objects/obmalloc.c:1996
+#   #4 0x55f399e86344 in PyModule_ExecDef Objects/moduleobject.c:400
+#   #5 0x55f399f6178a in exec_builtin_or_dynamic Python/import.c:2345
+#   #6 0x55f399f6178a in _imp_exec_dynamic_impl Python/import.c:2419
+#   #7 0x55f399f6178a in _imp_exec_dynamic Python/clinic/import.c.h:474
+#   #8 0x55f399e8438a in cfunction_vectorcall_O Objects/methodobject.c:514
+leak:^_imp_exec_dynamic
+
+
+# >>> Everything allocated at DSO initialization, e.g.
+#   #0 0x7f35d2af46c8 in operator new(unsigned long) .../asan_new_delete.cpp:95
+#   #1 0x7f35ce897e9f in __static_initialization_and_destruction_0 golang/context.cpp:61
+#   #2 0x7f35ce8982ef in _GLOBAL__sub_I_context.cpp golang/context.cpp:380
+#   #3 0x7f35d32838bd in call_init elf/dl-init.c:90
+#   #4 0x7f35d32838bd in call_init elf/dl-init.c:27
+#   #5 0x7f35d32839a3 in _dl_init elf/dl-init.c:137
+#   #6 0x7f35d256e023 in __GI__dl_catch_exception elf/dl-error-skeleton.c:182
+#   #7 0x7f35d328a09d in dl_open_worker elf/dl-open.c:808
+#   #8 0x7f35d256dfc9 in __GI__dl_catch_exception elf/dl-error-skeleton.c:208
+#   #9 0x7f35d328a437 in _dl_open elf/dl-open.c:884
+#   #10 0x7f35d24a4437 in dlopen_doit dlfcn/dlopen.c:56
+#   #11 0x7f35d256dfc9 in __GI__dl_catch_exception elf/dl-error-skeleton.c:208
+#   #12 0x7f35d256e07e in __GI__dl_catch_error elf/dl-error-skeleton.c:227
+#   #13 0x7f35d24a3f26 in _dlerror_run dlfcn/dlerror.c:138
+#   #14 0x7f35d24a44e8 in dlopen_implementation dlfcn/dlopen.c:71
+#   #15 0x7f35d24a44e8 in ___dlopen dlfcn/dlopen.c:81
+#   #16 0x7f35d2a77ff9 in dlopen .../sanitizer_common_interceptors.inc:6341
+leak:^_GLOBAL_
+
+
+# global<> does not deallocate its reference on purpose
+leak:^_test_global()$

MANIFEST.in

-include COPYING README.rst CHANGELOG.rst tox.ini pyproject.toml trun .nxdtest
+include COPYING README.rst CHANGELOG.rst tox.ini pyproject.toml trun .lsan-ignore.txt .nxdtest conftest.py
 include golang/libgolang.h
 include golang/runtime/libgolang.cpp
 include golang/runtime/libpyxruntime.cpp

conftest.py

+# pygolang | pytest config
+# Copyright (C) 2021-2024  Nexedi SA and Contributors.
+#                          Kirill Smelkov <kirr@nexedi.com>
+#
+# This program is free software: you can Use, Study, Modify and Redistribute
+# it under the terms of the GNU General Public License version 3, or (at your
+# option) any later version, as published by the Free Software Foundation.
+#
+# You can also Link and Combine this program with other software covered by
+# the terms of any of the Free Software licenses or any of the Open Source
+# Initiative approved licenses and Convey the resulting work. Corresponding
+# source of such a combination shall include the source code for all other
+# software used.
+#
+# This program is distributed WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+#
+# See COPYING file for full licensing terms.
+# See https://www.nexedi.com/licensing for rationale and options.
+
+from __future__ import print_function, absolute_import
+
+import gc
+
+
+# Do full GC before pytest exits, to avoid false positives in the leak detector.
+def pytest_unconfigure():
+    gc.collect()

golang/_golang.pyx

@@ -5,7 +5,7 @@
 # distutils: language = c++
 # distutils: depends = libgolang.h os/signal.h _golang_str.pyx
 #
-# Copyright (C) 2018-2023  Nexedi SA and Contributors.
+# Copyright (C) 2018-2024  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
@@ -173,9 +173,16 @@ cdef void __goviac(void *arg) nogil:
 
 # ---- channels ----
 
+# _frompyx indicates that a constructor is called from pyx code
+cdef object _frompyx = object()
+
 @final
 cdef class pychan:
     def __cinit__(pychan pych, size=0, dtype=object):
+        if dtype is _frompyx:
+            pych.dtype = DTYPE_STRUCTZ  # anything
+            pych._ch   = NULL
+        else:
             pych.dtype = parse_dtype(dtype)
             pych._ch = _makechan_pyexc(dtypeRegistry[<int>pych.dtype].size, size)
 
@@ -370,7 +377,7 @@ cdef void pychan_asserttype(pychan pych, DType dtype) nogil:
         panic("pychan: channel type mismatch")
 
 cdef pychan pychan_from_raw(_chan *_ch, DType dtype):
-    cdef pychan pych = pychan.__new__(pychan)
+    cdef pychan pych = pychan.__new__(pychan, dtype=_frompyx)
     pych.dtype = dtype
     pych._ch   = _ch; _chanxincref(_ch)
     return pych
@@ -626,9 +633,7 @@ cdef object c_to_py(DType dtype, const chanElemBuf *cfrom):
 
 # mkpynil creates pychan instance that represents nil[dtype].
 cdef PyObject *mkpynil(DType dtype):
-    cdef pychan pynil = pychan.__new__(pychan)
-    pynil.dtype = dtype
-    pynil._ch   = NULL   # should be already NULL
+    cdef pychan pynil = pychan_from_raw(NULL, dtype)
     Py_INCREF(pynil)
     return <PyObject *>pynil
 
@@ -818,9 +823,6 @@ from libcpp.typeinfo cimport type_info
 from cython.operator cimport typeid
 from libc.string cimport strcmp
 
-# _frompyx indicates that a constructor is called from pyx code
-cdef object _frompyx = object()
-
 cdef class pyerror(Exception):
     # pyerror <- error
     @staticmethod

golang/_golang_test.pyx

@@ -2,7 +2,7 @@
 # cython: language_level=2
 # distutils: language=c++
 #
-# Copyright (C) 2018-2020  Nexedi SA and Contributors.
+# Copyright (C) 2018-2024  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
@@ -344,6 +344,25 @@ cdef nogil:
         pych.chan_double().close()
 
 
+# verify that pychan_from_raw is not leaking C channel.
+def test_pychan_from_raw_noleak():
+    # pychan_from_raw used to create another channel and leak it
+    #
+    # this test _implicitly_ verifies that it is no longer the case - if it is,
+    # LSAN will report a memory leak after running the test.
+    #
+    # TODO consider adding explicit verification effective even under regular
+    #      builds. Possible options:
+    #
+    #      * verify malloc totals before and after tested code
+    #        see e.g. https://stackoverflow.com/q/1761125/9456786
+    #      * hook _makechan and verify that it is not invoked from under
+    #        pychan_from_raw. Depends on funchook integration.
+    cdef chan[int] ch   = makechan[int]()
+    cdef pychan    pych = pychan.from_chan_int(ch)  # uses pychan_from_raw internally
+    # pych and ch are freed automatically
+
+
 # ---- benchmarks ----
 
 # bench_go_nogil mirrors golang_test.py:bench_go

golang/golang_test.py

 # -*- coding: utf-8 -*-
-# Copyright (C) 2018-2023  Nexedi SA and Contributors.
+# Copyright (C) 2018-2024  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
@@ -74,7 +74,8 @@ import_pyx_tests("golang._golang_test")
 # leaked goroutine behaviour check: done in separate process because we need
 # to test process termination exit there.
 def test_go_leaked():
-    pyrun([dir_testprog + "/golang_test_goleaked.py"])
+    pyrun([dir_testprog + "/golang_test_goleaked.py"],
+          lsan=False)   # there are on-purpose leaks in this test
 
 # benchmark go+join a thread/coroutine.
 # pyx/nogil mirror is in _golang_test.pyx
@@ -1756,6 +1757,11 @@ def _pyrun(argv, stdin=None, stdout=None, stderr=None, **kw):   # -> retcode, st
         assert len(enc) == 1
         env['PYTHONIOENCODING'] = enc.pop()
 
+    # disable LeakSanitizer if requested, e.g. when test is known to leak something on purpose
+    lsan = kw.pop('lsan', True)
+    if not lsan:
+        env['ASAN_OPTIONS'] = env.get('ASAN_OPTIONS', '') + ',detect_leaks=0'
+
     p = Popen(argv, stdin=(PIPE if stdin else None), stdout=stdout, stderr=stderr, env=env, **kw)
     stdout, stderr = p.communicate(stdin)
 

golang/pyx/build_test.py

 # -*- coding: utf-8 -*-
-# Copyright (C) 2019  Nexedi SA and Contributors.
+# Copyright (C) 2019-2024  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
@@ -28,7 +28,8 @@ testprog = dirname(__file__) + "/testprog"
 # verify that we can build/run external package that uses pygolang in pyx mode.
 def test_pyx_build():
     pyxuser = testprog + "/golang_pyx_user"
-    pyrun(["setup.py", "build_ext", "-i"], cwd=pyxuser)
+    pyrun(["setup.py", "build_ext", "-i"], cwd=pyxuser,
+          lsan=False)   # gcc leaks
 
     # run built test.
     _ = pyout(["-c",
@@ -44,8 +45,8 @@ def test_pyx_build():
 # verify that we can build/run external dso that uses libgolang.
 def test_dso_build():
     dsouser = testprog + "/golang_dso_user"
-    pyrun(["setup.py", "build_dso", "-i"], cwd=dsouser)
-    pyrun(["setup.py", "build_ext", "-i"], cwd=dsouser)
+    pyrun(["setup.py", "build_dso", "-i"], cwd=dsouser,  lsan=False) # gcc leaks
+    pyrun(["setup.py", "build_ext", "-i"], cwd=dsouser,  lsan=False) # gcc leaks
 
     # run built test.
     _ = pyout(["-c",

setup.py

@@ -346,9 +346,6 @@ setup(
         Programming Language :: Python :: 2
         Programming Language :: Python :: 2.7
         Programming Language :: Python :: 3
-        Programming Language :: Python :: 3.5
-        Programming Language :: Python :: 3.6
-        Programming Language :: Python :: 3.7
         Programming Language :: Python :: 3.8
         Programming Language :: Python :: 3.9
         Programming Language :: Python :: 3.10

tox.ini

 [tox]
 envlist =
-    {py27d,py27,py37,py38,py39d,py39,py310d,py310,py311d,py311,py312,pypy,pypy3}-{thread,gevent}
+    {py27d,py27,py38,py39d,py39,py310d,py310,py311d,py311,py312,pypy,pypy3}-{thread,gevent}
 
 
 # ThreadSanitizer
@@ -10,24 +10,23 @@ envlist =
 # (*) PyPy locks its GIL (see RPyGilAcquire) by manually doing atomic cmpxchg
 # and other games, which TSAN cannot see if PyPy itself was not compiled with
 # -fsanitize=thread.
-    {py27d,py27,py37,py38,py39d,py39,py310d,py310,py311d,py311,py312           }-{thread       }-tsan
+    {py27d,py27,py38,py39d,py39,py310d,py310,py311d,py311,py312           }-{thread       }-tsan
 # XXX py*-gevent-tsan would be nice to have, but at present TSAN is not
 # effective with gevent, because it does not understand greenlet "thread"
 # switching and so perceives the program as having only one thread where races
 # are impossible. Disabled to save time.
-#   {py27d,py27,py37,py38,py39d,py39,py310d,py310,py311d,py311,py312           }-{       gevent}-tsan
+#   {py27d,py27,py38,py39d,py39,py310d,py310,py311d,py311,py312           }-{       gevent}-tsan
 
 
 # AddressSanitizer
 
 # XXX asan does not work with gevent: https://github.com/python-greenlet/greenlet/issues/113
-    {py27d,py27,py37,py38,py39d,py39,py310d,py310,py311d,py311,py312,pypy,pypy3}-{thread       }-asan
+    {py27d,py27,py38,py39d,py39,py310d,py310,py311d,py311,py312,pypy,pypy3}-{thread       }-asan
 
 [testenv]
 basepython =
     py27d:  python2.7-dbg
     py27:   python2.7
-    py37:   python3.7
     py38:   python3.8
     py39d:  python3.9-dbg
     py39:   python3.9
@@ -43,16 +42,16 @@ basepython =
 setenv =
 # distutils take CFLAGS for both C and C++.
 # distutils use  CFLAGS also at link stage -> we don't need to set LDFLAGS separately.
-    tsan: CFLAGS=-g -fsanitize=thread
-    asan: CFLAGS=-g -fsanitize=address
+    tsan: CFLAGS=-g -fsanitize=thread   -fno-omit-frame-pointer
+    asan: CFLAGS=-g -fsanitize=address  -fno-omit-frame-pointer
 # XXX however distutils' try_link, which is used by numpy.distutils use only CC
 # as linker without CFLAGS and _without_ LDFLAGS, which fails if *.o were
 # compiled with -fsanitize=X and linked without that option. Work it around
 # with also adjusting CC.
 # XXX better arrange to pass CFLAGS to pygolang only, e.g. by adding --race or
 # --sanitize=thread to `setup.py build_ext`.
-    tsan: CC=cc -fsanitize=thread
-    asan: CC=cc -fsanitize=address
+    tsan: CC=cc -fsanitize=thread   -fno-omit-frame-pointer
+    asan: CC=cc -fsanitize=address  -fno-omit-frame-pointer
 
 # always compile pygolang from source and don't reuse binary pygolang wheels as
 # we compile each case with different CFLAGS.
@@ -76,3 +75,5 @@ commands=
 # likewise for python debug builds.
         asan,tsan,py{27,39,310,311,312}d: -s    \
         gpython/ golang/
+
+allowlist_externals={toxinidir}/trun

trun

 #!/usr/bin/env python
+# -*- coding: utf-8 -*-
 # Copyright (C) 2019-2024  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
@@ -34,7 +35,7 @@ trun cares to run python with LD_PRELOAD set appropriately to /path/to/libtsan.s
 
 from __future__ import print_function, absolute_import
 
-import os, sys, re, subprocess, types
+import os, os.path, sys, re, subprocess, platform, types
 PY3 = (bytes is not str)
 if PY3:
     from importlib import machinery as imp_machinery
@@ -87,6 +88,7 @@ def main():
 
     # determine if _golang.so is linked to a sanitizer, and if yes, to which
     # particular sanitizer DSO. Set LD_PRELOAD appropriately.
+    libxsan    = None
     ld_preload = None
     if 'linux' in sys.platform:
         p = subprocess.Popen(["ldd", _golang_so.path], stdout=subprocess.PIPE)
@@ -127,7 +129,8 @@ def main():
 
             _ = grep1("DYLD_INSERT_LIBRARIES=(.*)$", err)
             if _ is not None:
-                ld_preload = ("DYLD_INSERT_LIBRARIES", _.group(1))
+                libxsan = _.group(1)
+                ld_preload = ("DYLD_INSERT_LIBRARIES", libxsan)
             else:
                 print("trun %r: `import golang` failed with unexpected error:" % sys.argv[1:], file=sys.stderr)
                 print(err, file=sys.stderr)
@@ -144,7 +147,7 @@ def main():
     env_prepend("TSAN_OPTIONS", "halt_on_error=1")
     env_prepend("ASAN_OPTIONS", "halt_on_error=1")
 
-    # tweak TSAN/ASAN defaults:
+    # tweak TSAN/ASAN/LSAN defaults:
 
     # enable TSAN deadlock detector
     # (unfortunately it caughts only few _potential_ deadlocks and actually
@@ -152,15 +155,49 @@ def main():
     env_prepend("TSAN_OPTIONS", "detect_deadlocks=1")
     env_prepend("TSAN_OPTIONS", "second_deadlock_stack=1")
 
-    # many python allocations, whose lifetime coincides with python interpreter
-    # lifetime and which are not explicitly freed on python shutdown, are
-    # reported as leaks. Disable leak reporting to avoid huge non-pygolang
-    # related printouts.
-    env_prepend("ASAN_OPTIONS", "detect_leaks=0")
-
     # tune ASAN to check more aggressively by default
     env_prepend("ASAN_OPTIONS", "detect_stack_use_after_return=1")
 
+    # enable ASAN/LSAN leak detector.
+    #
+    # Do it only on CPython ≥ 3.11 because on py2 and on earlier py3 versions
+    # there are many many python allocations, whose lifetime coincide with
+    # python interpreter lifetime, and which are not explicitly freed on python
+    # shutdown. For py3 they significantly improved this step by step and
+    # starting from 3.11 it becomes practical to silence some still-leaks with
+    # suppressions, while for earlier py3 versions and especially for py2 it
+    # is, unfortunately, not manageable. Do not spend engineering time with
+    # activating LSAN on PyPy as that is tier 2 platform and bug tail history
+    # of memory leaks is very long even only on cpython.
+    if sys.version_info < (3,11):
+        env_prepend("ASAN_OPTIONS", "detect_leaks=0")
+        if libxsan is not None:
+            if 'asan' in libxsan.lower():
+                print("W: trun %r: asan: leak detection deactivated on %s %s" % (
+                    sys.argv[1:], platform.python_implementation(), platform.python_version()),
+                    file=sys.stderr)
+    else:
+        env_prepend("ASAN_OPTIONS", "detect_leaks=1")
+        env_prepend("LSAN_OPTIONS", "suppressions=%s" % os.path.abspath(os.path.join(
+                                        os.path.dirname(__file__), ".lsan-ignore.txt")))
+        # do not print statistics for suppressed leaks - else it breaks tests that verify program output
+        env_prepend("LSAN_OPTIONS", "print_suppressions=0")
+
+        # enable DWARF-based unwinding.
+        # else, if python is not compiled with -fno-omit-frame-pointer, it can show
+        # the whole traceback as e.g. just
+        #   Direct leak of 32 byte(s) in 1 object(s) allocated from:
+        #     #0 0x7f88522f3bd7 in malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:69
+        #     #1 0x55f910a3d9a4 in PyThread_allocate_lock Python/thread_pthread.h:385
+        # and our leak suppressions won't work.
+        # this is slower compared to default frame-pointer based unwinding, but
+        # still works reasonably timely when run with just tests.
+        env_prepend("ASAN_OPTIONS", "fast_unwind_on_malloc=0")
+        # leak suppression also needs full tracebacks to work correctly, since with
+        # python there are many levels of call nesting at C level, and to filter-out e.g.
+        # top-level PyImport_Import we need to go really deep.
+        env_prepend("ASAN_OPTIONS", "malloc_context_size=255")
+
     # exec `...`
     os.execvp(sys.argv[1], sys.argv[1:])