From 04b0a7b1a6d9e0f3782888f1ebf187c26690038b Mon Sep 17 00:00:00 2001 From: Richard Biener Date: Wed, 29 Mar 2023 13:49:24 +0200 Subject: [PATCH] tree-optimization/107561 - reduce -Wstringop-overflow false positives 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. 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 } } };