From 354f5b684bf73feeea429740600b051ded3c9a92 Mon Sep 17 00:00:00 2001
From: Roy Stogner <Roy.Stogner@inl.gov>
Date: Fri, 11 Oct 2024 15:07:37 -0500
Subject: [PATCH] Workaround gcc 13 -Wdangling-reference warning

I don't see how this could be an actual dangling reference, and gcc has
bug reports specifically related to dangling reference false positives
from lambda functions, but the test case in bug report
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111607
doesn't actually trigger my gcc version.

This template metafunction workaround is much uglier code than the if
constexpr, but it should compile to the same binary and it doesn't
trigger any warnings.

Closes #28835
---
 .../include/auxkernels/MaterialAuxBase.h      | 34 +++++++++++++++----
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/framework/include/auxkernels/MaterialAuxBase.h b/framework/include/auxkernels/MaterialAuxBase.h
index 1e4565188bcb..28fb1bf950f7 100644
--- a/framework/include/auxkernels/MaterialAuxBase.h
+++ b/framework/include/auxkernels/MaterialAuxBase.h
@@ -13,6 +13,10 @@
 #include "AuxKernel.h"
 #include "Assembly.h"
 
+// Forward declarations
+template <typename T, bool is_ad, bool is_functor, typename RT>
+struct PropSetter;
+
 /**
  * A base class for the various Material related AuxKernal objects.
  * \p RT is short for return type
@@ -61,6 +65,9 @@ class MaterialAuxBaseTempl : public AuxKernelTempl<RT>
 
   /// ID of the subdomain currently being iterated over
   const SubdomainID & _current_subdomain_id;
+
+  /// Hack to avoid "dangling reference" warnings from gcc 13
+  friend struct PropSetter<T, is_ad, is_functor, RT>;
 };
 
 template <typename T, bool is_ad, bool is_functor, typename RT>
@@ -90,16 +97,31 @@ MaterialAuxBaseTempl<T, is_ad, is_functor, RT>::validParams()
   return params;
 }
 
+template <typename T, bool is_ad, bool is_functor, typename RT>
+struct PropSetter
+{
+  static const Moose::Functor<Moose::GenericType<T, is_ad>> &
+  prop(MaterialAuxBaseTempl<T, is_ad, is_functor, RT> & mabt)
+  {
+    return mabt.template getFunctor<Moose::GenericType<T, is_ad>>("functor");
+  }
+};
+
+template <typename T, bool is_ad, typename RT>
+struct PropSetter<T, is_ad, false, RT>
+{
+  static const GenericMaterialProperty<T, is_ad> &
+  prop(MaterialAuxBaseTempl<T, is_ad, false, RT> & mabt)
+  {
+    return mabt.template getGenericMaterialProperty<T, is_ad>("property");
+  }
+};
+
 template <typename T, bool is_ad, bool is_functor, typename RT>
 MaterialAuxBaseTempl<T, is_ad, is_functor, RT>::MaterialAuxBaseTempl(
     const InputParameters & parameters)
   : AuxKernelTempl<RT>(parameters),
-    _prop([this]() -> const auto & {
-      if constexpr (is_functor)
-        return this->template getFunctor<Moose::GenericType<T, is_ad>>("functor");
-      else
-        return this->template getGenericMaterialProperty<T, is_ad>("property");
-    }()),
+    _prop(PropSetter<T, is_ad, is_functor, RT>::prop(*this)),
     _selected_qp(this->isParamValid("selected_qp")
                      ? this->template getParam<unsigned int>("selected_qp")
                      : libMesh::invalid_uint),