From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Daniel Colascione Newsgroups: gmane.emacs.bugs Subject: bug#17168: 24.3.50; Segfault at mark_object Date: Sun, 06 Apr 2014 10:11:28 -0700 Message-ID: <53418AC0.5010300@dancol.org> References: <87y4zop44m.fsf@yahoo.fr> <533C3AF5.6070502@yandex.ru> <533C6905.9060309@dancol.org> <83bnwjbh8v.fsf@gnu.org> <533C75A6.60900@dancol.org> <533D06E6.2060001@yandex.ru> <533D07EF.1040502@yandex.ru> <533D13E2.3060300@dancol.org> <533D251E.3030108@dancol.org> <533D6A19.8050504@yandex.ru> <533D9099.3000104@dancol.org> <533D9F2C.7030500@yandex.ru> <533D9FBB.2050803@dancol.org> <533DB4F0.20706@dancol.org> <534085B1.9070307@dancol.org> <838uri8pkf.fsf@gnu.org> <534179FB.4090301@dancol.org> <834n268m7r.fsf@gnu.org> <53417FA1.1060100@dancol.org> <83zjjy7763.fsf@gnu.org> <534182C3.30205@dancol.org> <83y4zi75se.fsf@gnu.org> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; 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charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 04/06/2014 09:59 AM, Eli Zaretskii wrote: >> Date: Sun, 06 Apr 2014 09:37:23 -0700 >> From: Daniel Colascione >> CC: monnier@IRO.UMontreal.CA, dmantipov@yandex.ru, 17168@debbugs.gnu.o= rg >> >>> Because Richard has been using that machine for years, and I very muc= h >>> doubt that he changed his usage patterns lately. >> >> Richard's not the only one who has seen this crash. Drew's also report= ed >> GC crashes in odd, and different, places. >=20 > Which seem unrelated, and started much later than Richard reported > his. With a bug like this, unpredictable, usage-pattern-dependent behavior is expected. >>>>>>> In http://debbugs.gnu.org/cgi/bugreport.cgi?bug=3D15583#23, Richa= rd >>>>>>> provided the last good revno (113938) and the first bad one (1142= 68); >>>>>>> I looked at that range of revisions, and 114156 looks relevant. = How >>>>>>> about if we revert it and see if the problems go away? >>>>>> >>>>>> The bug would still be there, and we'd have no way to tell whether= your >>>>>> proposed change actually reduced its occurrence to a tolerable lev= el. >>>>>> Why would you want to do that instead of just fixing the bug? >>>>> >>>>> Because it's simpler, >>>> >>>> It's easy to make code that's simple and wrong. >>> >>> I didn't suggest any new code. >> >> No: you're just suggesting leaving incorrect code in Emacs. >=20 > It's not incorrect, AFAIU. It might be less optimal. The current code isn't just sub-optimal. It's wrong. If you get unlucky and try to mark a dead symbol, you will crash. >>>>> and because it just might be that the bug was >>>>> caused by that other changeset. >>>> >>>> How might that changeset in particular have caused the problem repor= ts? >>> >>> It is related to calling a function, and is in the same function from= >>> which all the recent crashes started. >> >> You haven't identified a causal mechanism. Any recent change could hav= e >> caused enough of a shift in code generation or stack layout to cause >> this problem, and because it manifests so seldom, it'd be hard to veri= fy >> that reverting any particular change "fixed" the problem. >=20 > I thought you had a test case. If not, how did you verify that your > suggested changes do fix the problem? There is a test. Your proposed change does not cause the test to pass. Even if it did, I would argue against substituting a real fix with your change. >> Also, eval_sub does *everything*. It's no surprise that we saw the >> crashes there. That's like saying "all crashes are associated with mai= n, >> this change affects main, and therefore this change is responsible." >=20 > The change is related to calling a function whose symbol has certain > properties. That sounds related to me, not just a random change > somewhere in eval_sub. It's a dangling pointer. Changing slightly the way we chase that dangling pointer won't change the overall result. --9K8HMDGO13VVMjXVWVPeGJosrwJWpPW8P Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.14 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQIcBAEBAgAGBQJTQYrAAAoJEMAaIROpHW7InBkQAMYFcyYra/ghuMh45szb+2DN SEPKcNWtWAEk+/y6elFP1f5v2WvO97rENe4Xg6WrQeohp2vIgf70sKvTUtMZnYHa QTFDhVF4TjhN7qRdVU6NzwbOpyhZmvsdPv6SOgZ0u1YRbbDKr6xuWRoKzVz1VfiI PSZ0zghomgZ5k0xBt/6CZyuxilAlrlUW1NH1i3sLlMO+KsMomX2PWUdKrggSFFE4 uBfq1HK0g1SIij9IyYZqmVuAfEmM98LDtRbyWFSYR4g+PttV8UQpliRa/AxPsn0n Zd00FTRfFnampOYL6EaXsObS52J71SAZCRZLjrid3cgELJMv4JbX8rXvN4ImEFXc LMEHvy4F7v7KiaXL52gcU0KFSZlEvKOxYV1iuZkWyGPJhEF5yosSpsMQ8RrIF42Y XI7VY/yGW9R0sKtOiJ5rLF18mxKLnpg8VnICV0u6wdPLpjHdHoL90Hwi0KwoIn+6 QEmSOmgIEulskQMe1V7GxYPmcBYJl3d2eP0/KeF+M/aoOmv/BzXquSk43Bet/OPE lFfqe4vAsJIBTd1+6s0ve9q5bEubrQ6ADjrgQYiY8wqLi0MKzbwcBpfxgqDNLy5a XFvRIKLrPU+lZM699gZLcc+WXpJPxdRZ2tQ/oTeRx+mC2qo1gUwTaL5wQMfVlJtd vxGMqhp5VUeN4eplZY1l =zqvE -----END PGP SIGNATURE----- --9K8HMDGO13VVMjXVWVPeGJosrwJWpPW8P--