[Python-Dev] Garbage announcement printed on interpreter shutdown (original) (raw)

Georg Brandl g.brandl at gmx.net
Fri Sep 10 22:32:25 CEST 2010

Hey #python-dev,

I'd like to ask your opinion on this change; I think it should be reverted or at least made silent by default. Basically, it prints a warning like

  gc: 2 uncollectable objects at shutdown:
      Use gc.set_debug(gc.DEBUG_UNCOLLECTABLE) to list them.

at interpreter shutdown if gc.garbage is nonempty.

IMO this runs contrary to the decision we made when DeprecationWarnings were made silent by default: it spews messages not only at developers, but also at users, who don't need it and probably are going to be quite confused by it, assuming it came from their console application (imagine Mercurial printing this).

Opinions?

Georg

Am 09.08.2010 00:18, schrieb antoine.pitrou:

Author: antoine.pitrou Date: Mon Aug 9 00🔞46 2010 New Revision: 83861

Log: Issue #477863: Print a warning at shutdown if gc.garbage is not empty.

Modified: python/branches/py3k/Doc/library/gc.rst python/branches/py3k/Doc/whatsnew/3.2.rst python/branches/py3k/Include/pythonrun.h python/branches/py3k/Lib/test/testgc.py python/branches/py3k/Misc/NEWS python/branches/py3k/Modules/gcmodule.c python/branches/py3k/Python/pythonrun.c Modified: python/branches/py3k/Doc/library/gc.rst ============================================================================== --- python/branches/py3k/Doc/library/gc.rst (original) +++ python/branches/py3k/Doc/library/gc.rst Mon Aug 9 00🔞46 2010 @@ -177,6 +177,15 @@ If :const:DEBUGSAVEALL is set, then all unreachable objects will be added to this list rather than freed. + .. versionchanged:: 3.2 + If this list is non-empty at interpreter shutdown, a warning message + gets printed: + + :: + + gc: 2 uncollectable objects at shutdown: + Use gc.setdebug(gc.DEBUGUNCOLLECTABLE) to list them. + The following constants are provided for use with :func:setdebug: @@ -197,6 +206,9 @@ reachable but cannot be freed by the collector). These objects will be added to the garbage list. + .. versionchanged:: 3.2 + Also print the contents of the :data:garbage list at interpreter + shutdown (rather than just its length), if it isn't empty. .. data:: DEBUGSAVEALL Modified: python/branches/py3k/Doc/whatsnew/3.2.rst ============================================================================== --- python/branches/py3k/Doc/whatsnew/3.2.rst (original) +++ python/branches/py3k/Doc/whatsnew/3.2.rst Mon Aug 9 00🔞46 2010 @@ -119,6 +119,11 @@ * The :class:ftplib.FTP class now supports the context manager protocol (Contributed by Tarek Ziadé and Giampaolo Rodolà; :issue:4972.) +* A warning message will now get printed at interpreter shutdown if + the :data:gc.garbage list isn't empty. This is meant to make the + programmer aware that his code contains object finalization issues. + (Added by Antoine Pitrou; :issue:477863.) + * The :func:shutil.copytree function has two new options: * ignoredanglingsymlinks: when symlinks=False (meaning that the Modified: python/branches/py3k/Include/pythonrun.h ============================================================================== --- python/branches/py3k/Include/pythonrun.h (original) +++ python/branches/py3k/Include/pythonrun.h Mon Aug 9 00🔞46 2010 @@ -148,6 +148,7 @@ PyAPIFUNC(void) PyByteArrayFini(void); PyAPIFUNC(void) PyFloatFini(void); PyAPIFUNC(void) PyOSFiniInterrupts(void); +PyAPIFUNC(void) PyGCFini(void); /* Stuff with no proper home (yet) */ PyAPIFUNC(char *) PyOSReadline(FILE *, FILE *, char *); Modified: python/branches/py3k/Lib/test/testgc.py ============================================================================== --- python/branches/py3k/Lib/test/testgc.py (original) +++ python/branches/py3k/Lib/test/testgc.py Mon Aug 9 00🔞46 2010 @@ -1,5 +1,5 @@ import unittest -from test.support import verbose, rununittest +from test.support import verbose, rununittest, strippythonstderr import sys import gc import weakref @@ -466,6 +466,42 @@ # would be damaged, with an empty dict. self.assertEqual(x, None) + def testgarbageatshutdown(self): + import subprocess + code = """if 1: + import gc + class X: + def init(self, name): + self.name = name + def repr(self): + return "<X %%r>" %% self.name + def del(self): + pass + + x = X('first') + x.x = x + x.y = X('second') + del x + if %d: + gc.setdebug(gc.DEBUGUNCOLLECTABLE) + """ + def runcommand(code): + p = subprocess.Popen([sys.executable, "-c", code], + stdout=subprocess.PIPE, + stderr=subprocess.PIPE) + stdout, stderr = p.communicate() + self.assertEqual(p.returncode, 0) + self.assertEqual(stdout.strip(), b"") + return strippythonstderr(stderr) + + stderr = runcommand(code % 0) + self.assertIn(b"gc: 2 uncollectable objects at shutdown", stderr) + self.assertNotIn(b"[<X 'first'>, <X 'second'>]", stderr) + # With DEBUGUNCOLLECTABLE, the garbage list gets printed + stderr = runcommand(code % 1) + self.assertIn(b"gc: 2 uncollectable objects at shutdown", stderr) + self.assertIn(b"[<X 'first'>, <X 'second'>]", stderr) + class GCTogglingTests(unittest.TestCase): def setUp(self): gc.enable() Modified: python/branches/py3k/Misc/NEWS ============================================================================== --- python/branches/py3k/Misc/NEWS (original) +++ python/branches/py3k/Misc/NEWS Mon Aug 9 00🔞46 2010 @@ -30,6 +30,8 @@ Extensions ---------- +- Issue #477863: Print a warning at shutdown if gc.garbage is not empty. + - Issue #6869: Fix a refcount problem in the ctypes extension. - Issue #5504: ctypes should now work with systems where mmap can't Modified: python/branches/py3k/Modules/gcmodule.c ============================================================================== --- python/branches/py3k/Modules/gcmodule.c (original) +++ python/branches/py3k/Modules/gcmodule.c Mon Aug 9 00🔞46 2010 @@ -1295,17 +1295,16 @@ static struct PyModuleDef gcmodule = { PyModuleDefHEADINIT, - "gc", - gc_doc,_ - -1, - GcMethods, - NULL, - NULL, - NULL, - NULL + "gc", /* mname */ + gc_doc, /* mdoc /_ _+ -1, / msize /_ _+ GcMethods, / mmethods /_ _+ NULL, / mreload /_ _+ NULL, / mtraverse /_ _+ NULL, / mclear /_ _+ NULL / mfree */_ }; - PyMODINITFUNC PyInitgc(void) { @@ -1364,6 +1363,37 @@ return n; } +void +PyGCFini(void) +{ + if (garbage != NULL && PyListGETSIZE(garbage) > 0) { + PySysWriteStderr( + "gc: " + "%" PYFORMATSIZET "d uncollectable objects at shutdown:\n", + PyListGETSIZE(garbage) + ); + if (debug & DEBUGUNCOLLECTABLE) { + PyObject *repr = NULL, *bytes = NULL; + repr = PyObjectRepr(garbage); + if (!repr || !(bytes = PyUnicodeEncodeFSDefault(repr))) + PyErrWriteUnraisable(garbage); + else { + PySysWriteStderr( + " %s\n", + PyBytesASSTRING(bytes) + ); + } + PyXDECREF(repr); + PyXDECREF(bytes); + } + else { + PySysWriteStderr( + " Use gc.setdebug(gc.DEBUGUNCOLLECTABLE) to list them.\n" + ); + } + } +} + /* for debugging */ void PyGCDump(PyGCHead *g) Modified: python/branches/py3k/Python/pythonrun.c ============================================================================== --- python/branches/py3k/Python/pythonrun.c (original) +++ python/branches/py3k/Python/pythonrun.c Mon Aug 9 00🔞46 2010 @@ -404,6 +404,9 @@ while (PyGCCollect() > 0) /* nothing */; #endif + /* We run this while most interpreter state is still alive, so that + debug information can be printed out */ + PyGCFini(); /* Destroy all modules */ PyImportCleanup();

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