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tree-optimization/107561 - reduce -Wstringop-overflow false positives

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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.
This commit is contained in:
Richard Biener 2023-03-29 13:49:24 +02:00
parent 1d0ba4467d
commit 04b0a7b1a6
3 changed files with 13 additions and 8 deletions
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19
gcc/gimple-ssa-warn-access.cc
View file

@ -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;

1
gcc/testsuite/g++.dg/pr71488.C
View file

@ -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 <valarray>

1
gcc/testsuite/g++.dg/warn/Warray-bounds-16.C
View file

@ -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 }
}
};