From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by sourceware.org (Postfix) with ESMTPS id AE6883858439 for ; Thu, 30 Mar 2023 11:16:55 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org AE6883858439 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=suse.de Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=suse.de Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id C88B321B3A; Thu, 30 Mar 2023 11:16:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1680175014; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type; bh=ivl5cOpMt2nbOIcO24RcO+8QuLrtiGXRwM0OJbxflWU=; b=OHlKvNdLhoaPDN9TVsPr147T6PGww4YTMNPDaCXaJu1+/xwLcjsst0znIbyv0vzPT25q1L PakU7Zq89MCfvSxuSeFnK3jf5FwZOJH4ksfyaEmCNRJzETCaX7Z+y5YUHnb5lEOZ5auoMy v85Oo1+kpgjoLkc44SpFvs+H20U8hBk= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1680175014; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type; bh=ivl5cOpMt2nbOIcO24RcO+8QuLrtiGXRwM0OJbxflWU=; b=9b4cMl/qX3/PMUh7ncYrdeH//AuVlvw06nMsoB8bWBZX55tYGar46+rp3HSBkUm4bEBzMC dRZxEOvKXKjq8uCQ== Received: from wotan.suse.de (wotan.suse.de [10.160.0.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id B73532C420; Thu, 30 Mar 2023 11:16:54 +0000 (UTC) Date: Thu, 30 Mar 2023 11:16:54 +0000 (UTC) From: Richard Biener To: gcc-patches@gcc.gnu.org cc: Jakub Jelinek Subject: Re: [PATCH] tree-optimization/107561 - reduce -Wstringop-overflow false positives Message-ID: User-Agent: Alpine 2.22 (LSU 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Spam-Status: No, score=-11.0 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Wed, 29 Mar 2023, Richard Biener wrote: > The following tells pointer-query to prefer a zero size when we > are querying for the size range for a write into an object we've > determined is of zero size. That avoids diagnostics about really > varying size arguments that just get a meaningful range for example > because they are multiplied by an element size. > > I've adjusted only one call to get_size_range since that's what > I have a testcase for. I think this is the most sensible > "workaround" for some of the false positives we see. > > Bootstrapped on x86_64-unknown-linux-gnu, testing in progress. > > OK if it succeeds? It did, I have now pushed this, it seems like an obvious improvement. Richard. > Thanks, > Richard. > > PR tree-optimization/107561 > * gimple-ssa-warn-access.cc (get_size_range): Add flags > argument and pass it on. > (check_access): When querying for the size range pass > SR_ALLOW_ZERO when the known destination size is zero. > > * g++.dg/pr71488.C: Remove XFAILed bogus diagnostic again. > * g++.dg/warn/Warray-bounds-16.C: Likewise. > --- > gcc/gimple-ssa-warn-access.cc | 19 +++++++++++++------ > gcc/testsuite/g++.dg/pr71488.C | 1 - > gcc/testsuite/g++.dg/warn/Warray-bounds-16.C | 1 - > 3 files changed, 13 insertions(+), 8 deletions(-) > > diff --git a/gcc/gimple-ssa-warn-access.cc b/gcc/gimple-ssa-warn-access.cc > index 88d44690ade..b3de4b77924 100644 > --- a/gcc/gimple-ssa-warn-access.cc > +++ b/gcc/gimple-ssa-warn-access.cc > @@ -1198,10 +1198,10 @@ warn_for_access (location_t loc, tree func, tree expr, int opt, > > static void > get_size_range (range_query *query, tree bound, gimple *stmt, tree range[2], > - const offset_int bndrng[2]) > + int flags, const offset_int bndrng[2]) > { > if (bound) > - get_size_range (query, bound, stmt, range); > + get_size_range (query, bound, stmt, range, flags); > > if (!bndrng || (bndrng[0] == 0 && bndrng[1] == HOST_WIDE_INT_M1U)) > return; > @@ -1347,7 +1347,12 @@ check_access (GimpleOrTree exp, tree dstwrite, > /* Set RANGE to that of DSTWRITE if non-null, bounded by PAD->DST_BNDRNG > if valid. */ > gimple *stmt = pad ? pad->stmt : nullptr; > - get_size_range (rvals, dstwrite, stmt, range, pad ? pad->dst_bndrng : NULL); > + get_size_range (rvals, dstwrite, stmt, range, > + /* If the destination has known zero size prefer a zero > + size range to avoid false positives if that's a > + possibility. */ > + integer_zerop (dstsize) ? SR_ALLOW_ZERO : 0, > + pad ? pad->dst_bndrng : NULL); > > tree func = get_callee_fndecl (exp); > /* Read vs write access by built-ins can be determined from the const > @@ -1442,7 +1447,8 @@ check_access (GimpleOrTree exp, tree dstwrite, > { > /* Set RANGE to that of MAXREAD, bounded by PAD->SRC_BNDRNG if > PAD is nonnull and BNDRNG is valid. */ > - get_size_range (rvals, maxread, stmt, range, pad ? pad->src_bndrng : NULL); > + get_size_range (rvals, maxread, stmt, range, 0, > + pad ? pad->src_bndrng : NULL); > > location_t loc = get_location (exp); > tree size = dstsize; > @@ -1489,7 +1495,8 @@ check_access (GimpleOrTree exp, tree dstwrite, > { > /* Set RANGE to that of MAXREAD, bounded by PAD->SRC_BNDRNG if > PAD is nonnull and BNDRNG is valid. */ > - get_size_range (rvals, maxread, stmt, range, pad ? pad->src_bndrng : NULL); > + get_size_range (rvals, maxread, stmt, range, 0, > + pad ? pad->src_bndrng : NULL); > /* Set OVERREAD for reads starting just past the end of an object. */ > overread = pad->src.sizrng[1] - pad->src.offrng[0] < pad->src_bndrng[0]; > range[0] = wide_int_to_tree (sizetype, pad->src_bndrng[0]); > @@ -2679,7 +2686,7 @@ pass_waccess::check_strncmp (gcall *stmt) > /* Determine the range of the bound first and bail if it fails; it's > cheaper than computing the size of the objects. */ > tree bndrng[2] = { NULL_TREE, NULL_TREE }; > - get_size_range (m_ptr_qry.rvals, bound, stmt, bndrng, adata1.src_bndrng); > + get_size_range (m_ptr_qry.rvals, bound, stmt, bndrng, 0, adata1.src_bndrng); > if (!bndrng[0] || integer_zerop (bndrng[0])) > return; > > diff --git a/gcc/testsuite/g++.dg/pr71488.C b/gcc/testsuite/g++.dg/pr71488.C > index a89e6465a94..ffe30f1afeb 100644 > --- a/gcc/testsuite/g++.dg/pr71488.C > +++ b/gcc/testsuite/g++.dg/pr71488.C > @@ -3,7 +3,6 @@ > // { dg-options "-O3 -std=c++11" } > // { dg-additional-options "-msse4" { target sse4_runtime } } > // { dg-require-effective-target c++11 } > -// { dg-bogus "size 0 overflows" "pr107561" { xfail *-*-* } 0 } > > #include > > diff --git a/gcc/testsuite/g++.dg/warn/Warray-bounds-16.C b/gcc/testsuite/g++.dg/warn/Warray-bounds-16.C > index 49d3437fa1b..89cbadb91c7 100644 > --- a/gcc/testsuite/g++.dg/warn/Warray-bounds-16.C > +++ b/gcc/testsuite/g++.dg/warn/Warray-bounds-16.C > @@ -20,7 +20,6 @@ struct S > > for (int i = 0; i < m; i++) > new (p + i) int (); /* { dg-bogus "bounds" "pr102690" { xfail *-*-* } } */ > - // { dg-bogus "size 0 overflows" "pr107561" { xfail ilp32 } .-1 } > } > }; > > -- Richard Biener SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg, Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman; HRB 36809 (AG Nuernberg)