[llvm] [flang] Don't associate pointers with zero sized storage targets (PR #155867)

[Eugene Epshteyn via llvm-commits]

https://github.com/eugeneepshteyn created https://github.com/llvm/llvm-project/pull/155867

Fixes #155481

>From 96e80af46f4cba147b3c3297cdcc138ffcafb775 Mon Sep 17 00:00:00 2001
From: Eugene Epshteyn <eepshteyn at nvidia.com>
Date: Thu, 28 Aug 2025 11:54:13 -0400
Subject: [PATCH] [flang] Don't associate pointers with zero sized storage
 targets

Fixes #155481
---
 flang-rt/lib/runtime/pointer.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/flang-rt/lib/runtime/pointer.cpp b/flang-rt/lib/runtime/pointer.cpp
index 68db2594acdd4..4b1b921b1ce07 100644
--- a/flang-rt/lib/runtime/pointer.cpp
+++ b/flang-rt/lib/runtime/pointer.cpp
@@ -67,8 +67,12 @@ void RTDEF(PointerAssociateScalar)(Descriptor &pointer, void *target) {
 }
 
 void RTDEF(PointerAssociate)(Descriptor &pointer, const Descriptor &target) {
-  pointer = target;
-  pointer.raw().attribute = CFI_attribute_pointer;
+  if (target.ElementBytes() > 0) {
+    // F2023, 16.9.20, p5, case (v)-(vi): don't associate pointers with
+    // targets that have zero sized storage sequence.
+    pointer = target;
+    pointer.raw().attribute = CFI_attribute_pointer;
+  }
 }
 
 void RTDEF(PointerAssociateLowerBounds)(Descriptor &pointer,