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* [gcc r11-10069] tree-optimization/105726 - adjust array bound heuristic
@ 2022-06-15 8:59 Richard Biener
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From: Richard Biener @ 2022-06-15 8:59 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:d76c15430f74024f1658be55cfcd2ed9f581f1bd
commit r11-10069-gd76c15430f74024f1658be55cfcd2ed9f581f1bd
Author: Richard Biener <rguenther@suse.de>
Date: Wed May 25 11:49:03 2022 +0200
tree-optimization/105726 - adjust array bound heuristic
There's heuristic to detect ptr[1].a[...] out of bound accesses
reasoning that if ptr points to an array of aggregates a trailing
incomplete array has to have size zero. The following more
thoroughly constrains the cases this applies to avoid false
positive diagnostics.
2022-05-25 Richard Biener <rguenther@suse.de>
PR tree-optimization/105726
* gimple-ssa-warn-restrict.c (builtin_memref::set_base_and_offset):
Constrain array-of-flexarray case more.
* g++.dg/warn/Warray-bounds-27.C: New testcase.
(cherry picked from commit e7c482b08076bb299742883c4ffd65b31e33200c)
Diff:
---
gcc/gimple-ssa-warn-restrict.c | 22 +++++++++++++---------
gcc/testsuite/g++.dg/warn/Warray-bounds-27.C | 16 ++++++++++++++++
2 files changed, 29 insertions(+), 9 deletions(-)
diff --git a/gcc/gimple-ssa-warn-restrict.c b/gcc/gimple-ssa-warn-restrict.c
index ad37f20afaa..cfaa2179bb6 100644
--- a/gcc/gimple-ssa-warn-restrict.c
+++ b/gcc/gimple-ssa-warn-restrict.c
@@ -514,7 +514,6 @@ builtin_memref::set_base_and_offset (tree expr)
{
tree memrefoff = fold_convert (ptrdiff_type_node, TREE_OPERAND (base, 1));
extend_offset_range (memrefoff);
- base = TREE_OPERAND (base, 0);
if (refoff != HOST_WIDE_INT_MIN
&& TREE_CODE (expr) == COMPONENT_REF)
@@ -527,14 +526,19 @@ builtin_memref::set_base_and_offset (tree expr)
REFOFF is set to s[1].b - (char*)s. */
offset_int off = tree_to_shwi (memrefoff);
refoff += off;
- }
-
- if (!integer_zerop (memrefoff))
- /* A non-zero offset into an array of struct with flexible array
- members implies that the array is empty because there is no
- way to initialize such a member when it belongs to an array.
- This must be some sort of a bug. */
- refsize = 0;
+
+ if (!integer_zerop (memrefoff)
+ && !COMPLETE_TYPE_P (TREE_TYPE (expr))
+ && multiple_of_p (sizetype, memrefoff,
+ TYPE_SIZE_UNIT (TREE_TYPE (base))))
+ /* A non-zero offset into an array of struct with flexible array
+ members implies that the array is empty because there is no
+ way to initialize such a member when it belongs to an array.
+ This must be some sort of a bug. */
+ refsize = 0;
+ }
+
+ base = TREE_OPERAND (base, 0);
}
if (TREE_CODE (ref) == COMPONENT_REF)
diff --git a/gcc/testsuite/g++.dg/warn/Warray-bounds-27.C b/gcc/testsuite/g++.dg/warn/Warray-bounds-27.C
new file mode 100644
index 00000000000..06ce089c4b0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Warray-bounds-27.C
@@ -0,0 +1,16 @@
+// PR105726
+// { dg-do compile }
+// { dg-require-effective-target c++11 }
+// { dg-options "-O2 -Warray-bounds" }
+
+#include <array>
+#include <cstring>
+
+struct X {
+ char pad[4];
+ std::array<char, 1> mField;
+};
+
+void encode(char* aBuffer, const X& aMessage) {
+ strncpy(aBuffer, aMessage.mField.data(), 1); // { dg-bogus "bounds" }
+}
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