From b0856bb588c76e16a518b459a8c9a012dc2b4e21 Mon Sep 17 00:00:00 2001
From: Richard Biener <rguenther@suse.de>
Date: Mon, 5 Jun 2023 08:56:53 +0200
Subject: [PATCH] middle-end/110055 - avoid CLOBBERing static variables
The gimplifier can elide initialized constant automatic variables
to static storage in which case TARGET_EXPR gimplification needs
to avoid emitting a CLOBBER for them since their lifetime is no
longer limited. Failing to do so causes spurious dangling-pointer
diagnostics on the added testcase for some targets.
PR middle-end/110055
* gimplify.cc (gimplify_target_expr): Do not emit
CLOBBERs for variables which have static storage duration
after gimplifying their initializers.
* g++.dg/warn/Wdangling-pointer-pr110055.C: New testcase.
(cherry picked from commit 84eec2916fa68cd2e2b3a2cf764f2ba595cce843)
---
gcc/gimplify.cc | 4 +++-
.../g++.dg/warn/Wdangling-pointer-pr110055.C | 16 ++++++++++++++++
2 files changed, 19 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/warn/Wdangling-pointer-pr110055.C
diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
index ade6e335da7b..aece89a3e9bd 100644
--- a/gcc/gimplify.cc
+++ b/gcc/gimplify.cc
@@ -7154,8 +7154,10 @@ gimplify_target_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p)
gimplify_and_add (init, &init_pre_p);
/* Add a clobber for the temporary going out of scope, like
- gimplify_bind_expr. */
+ gimplify_bind_expr. But only if we did not promote the
+ temporary to static storage. */
if (gimplify_ctxp->in_cleanup_point_expr
+ && !TREE_STATIC (temp)
&& needs_to_live_in_memory (temp))
{
if (flag_stack_reuse == SR_ALL)
diff --git a/gcc/testsuite/g++.dg/warn/Wdangling-pointer-pr110055.C b/gcc/testsuite/g++.dg/warn/Wdangling-pointer-pr110055.C
new file mode 100644
index 000000000000..77dbbf380b69
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wdangling-pointer-pr110055.C
@@ -0,0 +1,16 @@
+// { dg-do compile }
+// { dg-require-effective-target c++11 }
+// { dg-options "-O3 -fno-exceptions -Wdangling-pointer" }
+
+#include <cstdint>
+#include <vector>
+
+struct Data {
+ std::vector<uint16_t> v = {1, 1};
+};
+
+int main()
+{
+ Data a;
+ Data b;
+}
--
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