From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ffbox0-bg.mplayerhq.hu (ffbox0-bg.ffmpeg.org [79.124.17.100]) by master.gitmailbox.com (Postfix) with ESMTP id 67BC74B011 for ; Mon, 1 Jul 2024 18:07:34 +0000 (UTC) Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id 8AAFB68D7C0; Mon, 1 Jul 2024 21:07:32 +0300 (EEST) Received: from relay5-d.mail.gandi.net (relay5-d.mail.gandi.net [217.70.183.197]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id 3E77868D428 for ; Mon, 1 Jul 2024 21:07:25 +0300 (EEST) Received: by mail.gandi.net (Postfix) with ESMTPSA id 93F691C0003 for ; Mon, 1 Jul 2024 18:07:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=niedermayer.cc; s=gm1; t=1719857244; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=xeM3KkZukErDmK7JnbN/JBaN8/YCMz2A+u6YV7iTkCw=; b=QJdIWQoFSjbS30yPy9waO3zaHaqBzFvWLZjS1mmDdcXtMs9X/evVar954aUsfgnuExJ6gM Dh9fTZDXOk0DHuF/G3TzEsWfijuhuGY37JQMw8iIbiqLPGv/9wA8OepCDzGTjxLegPyOnK XL0+6OJC9uwsIcFRPGGFDMMfIy/CKm/5EPYCTPPJyc0/UMNXrQqp8DtgPRdUKqwi53Avqd yrRatODW7oUfe9/HfNqMwE34G09OpJEkrwEqS8sLbyfIZqtTpblUiDeFjR9z+3iqS+kzNj DhQDaotYNPariVdwdLPbe+msep+D7gL/YgOe43cBSWeh3ULTtQJ/xampyOsUTg== Date: Mon, 1 Jul 2024 20:07:23 +0200 From: Michael Niedermayer To: FFmpeg development discussions and patches Message-ID: <20240701180723.GH4991@pb2> References: <20240701133923.GF4991@pb2> MIME-Version: 1.0 In-Reply-To: <20240701133923.GF4991@pb2> X-GND-Sasl: michael@niedermayer.cc Subject: Re: [FFmpeg-devel] [RFC] av_rescale() coverity X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Content-Type: multipart/mixed; boundary="===============0975502109768999408==" Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" Archived-At: List-Archive: List-Post: --===============0975502109768999408== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="8YDLdOu/DaKXZo9W" Content-Disposition: inline --8YDLdOu/DaKXZo9W Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jul 01, 2024 at 03:39:23PM +0200, Michael Niedermayer wrote: > Hi all >=20 > coverity seems to have started to do a new thing. Namely if theres a > return statement it assumes it can independant of everything occurr >=20 > an example would be av_rescale() which on overflow returns INT64_MIN >=20 > also with the right flags av_rescale() will pass INT64_MIN and INT64_MAX = through > from the input >=20 > So coverity since a few days seems to treat every av_rescale() call as if= it returns > INT64_MIN and INT64_MAX. coverity doesnt care if that return statement is= reachable or > if the flags even include the execution path. >=20 > An example is this: > AVRational time_base_q =3D AV_TIME_BASE_Q; > int64_t next_dts =3D av_rescale_q(ds->next_dts, time_base_q, = av_inv_q(ist->framerate)); > ds->next_dts =3D av_rescale_q(next_dts + 1, av_inv_q(ist->fra= merate), time_base_q); >=20 > Here coverity as a initial statement claims next_dts is INT64_MAX > and next_dts + 1 would overflow >=20 >=20 > 8. function_return: Function av_rescale_q(ds->next_dts, time_base_q, = av_inv_q(ist->framerate)) returns 9223372036854775807. > 9. known_value_assign: next_dts =3D av_rescale_q(ds->next_dts= , time_base_q, av_inv_q(ist->framerate)), its value is now 9223372036854775= 807. > 331 int64_t next_dts =3D av_rescale_q(ds->next_dts, time_b= ase_q, av_inv_q(ist->framerate)); >=20 > CID 1604545: (#1 of 1): Overflowed constant (INTEGER_OVERFLOW) > 10. overflow_const: Expression next_dts + 1LL, which is equal to -922= 3372036854775808, where next_dts is known to be equal to 922337203685477580= 7, overflows the type that receives it, a signed integer 64 bits wide. >=20 >=20 > another example is this: >=20 > #define AV_TIME_BASE 1000000 > pts =3D av_rescale(ds->dts, 1000000, AV_TIME_BASE); >=20 > coverity hallucinates pts as a tainted negative number here nothing says = anything about > the input ds->dts (and thats what would matter) >=20 > In the past coverity provided a detailed list of steps on how a > case is reached. One could then check these assumtions and mark things > as false positive when one assumtion is wrong. (coverity was most of the = time > wrong) >=20 > Now coverity just hallucinates claims out of the blue without any > explanation how that can happen. >=20 > Iam a bit at a loss how to deal with this and also why exactly this > new behavior appeared. >=20 > Has anyone changed any setting or anything in coverity ? >=20 > The number of issues shot up to over 400 on the 22th june > "194 new defect(s) introduced to FFmpeg/FFmpeg found with Coverity Scan." >=20 > before this i thought iam mostly done with my coverity work. > now truth is, the STF text speaks about 673 issues at the time and not > what appears after the work started, but it makes me a bit sad if i categ= orize > ~700+ issues and then fix the ones that are bugs just to find coverity > hallucinate 200 new issues a month that ill have to leave open for future > efforts. >=20 > I did not expect that years of ignoring coverity accumulate 673 issues and > then suddenly the rate of new issues to shoot up like this. I kind of exp= ected > that i can fix all new issues appearing during the work with insignifican= t extra effort I will try to adjust the modelling file we use and see if that reduces the av_rescale() hallucinations [...] --=20 Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety -- Benjamin Franklin --8YDLdOu/DaKXZo9W Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iF0EABEKAB0WIQSf8hKLFH72cwut8TNhHseHBAsPqwUCZoLwWAAKCRBhHseHBAsP q7HyAJ9r+gyjcPelSx8Q/wT7+tnRDfCUdACeJ0765e0os7dNA4gB89RmMUu+rLk= =1+lf -----END PGP SIGNATURE----- --8YDLdOu/DaKXZo9W-- --===============0975502109768999408== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe". --===============0975502109768999408==--