From 41174ed7f6eedc0be4bbfdebc021453af7785df7 Mon Sep 17 00:00:00 2001
From: Roland Reichwein <Roland.Reichwein@bmw.de>
Date: Tue, 26 May 2026 05:18:27 +0200
Subject: [PATCH] Add missing constexpr to intrusive_links.h constructors
 (#1446)

---
 include/etl/intrusive_links.h | 16 ++++++-------
 test/test_intrusive_links.cpp | 42 +++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 8 deletions(-)

diff --git a/include/etl/intrusive_links.h b/include/etl/intrusive_links.h
index a1a9e653..3d23f326 100644
--- a/include/etl/intrusive_links.h
+++ b/include/etl/intrusive_links.h
@@ -91,25 +91,25 @@ namespace etl
     };
 
     //***********************************
-    forward_link()
+    ETL_CONSTEXPR forward_link()
       : etl_next(ETL_NULLPTR)
     {
     }
 
     //***********************************
-    forward_link(forward_link* p_next)
+    ETL_CONSTEXPR forward_link(forward_link* p_next)
       : etl_next(p_next)
     {
     }
 
     //***********************************
-    forward_link(const forward_link& other)
+    ETL_CONSTEXPR forward_link(const forward_link& other)
       : etl_next(other.etl_next)
     {
     }
 
     //***********************************
-    forward_link& operator=(const forward_link& other)
+    ETL_CONSTEXPR14 forward_link& operator=(const forward_link& other)
     {
       etl_next = other.etl_next;
 
@@ -495,28 +495,28 @@ namespace etl
     };
 
     //***********************************
-    bidirectional_link()
+    ETL_CONSTEXPR bidirectional_link()
       : etl_previous(ETL_NULLPTR)
       , etl_next(ETL_NULLPTR)
     {
     }
 
     //***********************************
-    bidirectional_link(bidirectional_link* p_previous, bidirectional_link* p_next)
+    ETL_CONSTEXPR bidirectional_link(bidirectional_link* p_previous, bidirectional_link* p_next)
       : etl_previous(p_previous)
       , etl_next(p_next)
     {
     }
 
     //***********************************
-    bidirectional_link(const bidirectional_link& other)
+    ETL_CONSTEXPR bidirectional_link(const bidirectional_link& other)
       : etl_previous(other.etl_previous)
       , etl_next(other.etl_next)
     {
     }
 
     //***********************************
-    bidirectional_link& operator=(const bidirectional_link& other)
+    ETL_CONSTEXPR14 bidirectional_link& operator=(const bidirectional_link& other)
     {
       etl_previous = other.etl_previous;
       etl_next     = other.etl_next;
diff --git a/test/test_intrusive_links.cpp b/test/test_intrusive_links.cpp
index 7bdbeb1b..141cb7f6 100644
--- a/test/test_intrusive_links.cpp
+++ b/test/test_intrusive_links.cpp
@@ -1855,5 +1855,47 @@ namespace
       // If we get here without crashing, the test passes
       CHECK(true);
     }
+
+#if ETL_USING_CPP14
+    //*************************************************************************
+    TEST(test_forward_link_constexpr)
+    {
+      constexpr FLink0 link0{};
+      static_assert(link0.etl_next == nullptr, "forward_link default ctor should be constexpr");
+
+      constexpr FLink0 link1{nullptr};
+      static_assert(link1.etl_next == nullptr, "forward_link pointer ctor should be constexpr");
+
+      constexpr FLink0 link2{link1};
+      static_assert(link2.etl_next == nullptr, "forward_link copy ctor should be constexpr");
+
+      CHECK(link0.etl_next == nullptr);
+      CHECK(link1.etl_next == nullptr);
+      CHECK(link2.etl_next == nullptr);
+    }
+
+    //*************************************************************************
+    TEST(test_bidirectional_link_constexpr)
+    {
+      constexpr BLink0 link0{};
+      static_assert(link0.etl_previous == nullptr, "bidirectional_link default ctor should be constexpr (previous)");
+      static_assert(link0.etl_next == nullptr, "bidirectional_link default ctor should be constexpr (next)");
+
+      constexpr BLink0 link1{nullptr, nullptr};
+      static_assert(link1.etl_previous == nullptr, "bidirectional_link param ctor should be constexpr (previous)");
+      static_assert(link1.etl_next == nullptr, "bidirectional_link param ctor should be constexpr (next)");
+
+      constexpr BLink0 link2{link1};
+      static_assert(link2.etl_previous == nullptr, "bidirectional_link copy ctor should be constexpr (previous)");
+      static_assert(link2.etl_next == nullptr, "bidirectional_link copy ctor should be constexpr (next)");
+
+      CHECK(link0.etl_previous == nullptr);
+      CHECK(link0.etl_next == nullptr);
+      CHECK(link1.etl_previous == nullptr);
+      CHECK(link1.etl_next == nullptr);
+      CHECK(link2.etl_previous == nullptr);
+      CHECK(link2.etl_next == nullptr);
+    }
+#endif
   }
 } // namespace