From 0f487fa12673a6aab406c1ed0bc23d5602eb406d Mon Sep 17 00:00:00 2001
From: John Wellbelove <github@wellbelove.co.uk>
Date: Mon, 16 Dec 2024 14:58:16 +0000
Subject: [PATCH] Make 'packed' have better cross platform functionality

---
 include/etl/platform.h       | 13 +++++++++++--
 include/etl/unaligned_type.h |  6 +++---
 test/test_etl_traits.cpp     |  1 +
 test/test_utility.cpp        | 26 ++++++++++++++++++++++++++
 4 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/include/etl/platform.h b/include/etl/platform.h
index 6ea92d362..0583d17ae 100644
--- a/include/etl/platform.h
+++ b/include/etl/platform.h
@@ -462,10 +462,18 @@ SOFTWARE.
 
 //*************************************
 // Determine if the ETL should use __attribute__((packed).
-#if defined(ETL_COMPILER_CLANG) || defined(ETL_COMPILER_GCC) || defined(ETL_COMPILER_INTEL)
-  #define ETL_PACKED __attribute__((packed))
+#if defined(ETL_COMPILER_CLANG) || defined(ETL_COMPILER_GCC) || defined(ETL_COMPILER_INTEL) || defined(ETL_COMPILER_ARM6)
+  #define ETL_PACKED     __attribute__((packed))
+  #define ETL_END_PACKED
+  #define ETL_HAS_PACKED 1
+#elif defined(ETL_COMPILER_MICROSOFT)
+  #define ETL_PACKED     __pragma(pack(push, 1))
+  #define ETL_END_PACKED __pragma(pack(pop))
+  #define ETL_HAS_PACKED 1
 #else
   #define ETL_PACKED
+  #define ETL_END_PACKED
+  #define ETL_HAS_PACKED 0
 #endif
 
 //*************************************
@@ -526,6 +534,7 @@ namespace etl
     static ETL_CONSTANT bool has_mutable_array_view           = (ETL_HAS_MUTABLE_ARRAY_VIEW == 1);
     static ETL_CONSTANT bool has_ideque_repair                = (ETL_HAS_IDEQUE_REPAIR == 1);
     static ETL_CONSTANT bool has_virtual_messages             = (ETL_HAS_VIRTUAL_MESSAGES == 1);
+    static ETL_CONSTANT bool has_packed                       = (ETL_HAS_PACKED == 1);
 
     // Is...
     static ETL_CONSTANT bool is_debug_build                   = (ETL_IS_DEBUG_BUILD == 1);
diff --git a/include/etl/unaligned_type.h b/include/etl/unaligned_type.h
index 77e38ce12..1c406ba3c 100644
--- a/include/etl/unaligned_type.h
+++ b/include/etl/unaligned_type.h
@@ -53,7 +53,7 @@ namespace etl
     /// Contains all functionality that doesn't require the type.
     //*************************************************************************
     template <size_t Size_>
-    class unaligned_type_common
+    class ETL_PACKED unaligned_type_common
     {
     public:
 
@@ -214,7 +214,7 @@ namespace etl
     protected:
 
       unsigned char storage[Size];
-    };
+    }; ETL_END_PACKED
 
     template <size_t Size_>
     ETL_CONSTANT size_t unaligned_type_common<Size_>::Size;
@@ -729,7 +729,7 @@ namespace etl
         }
       }
     };
-  };
+  }; ETL_END_PACKED
 
   template <typename T, int Endian_>
   ETL_CONSTANT int unaligned_type<T, Endian_>::Endian;
diff --git a/test/test_etl_traits.cpp b/test/test_etl_traits.cpp
index a071960e4..24123ad3a 100644
--- a/test/test_etl_traits.cpp
+++ b/test/test_etl_traits.cpp
@@ -77,6 +77,7 @@ namespace
       CHECK_EQUAL((ETL_HAS_IDEQUE_REPAIR == 1),                etl::traits::has_ideque_repair);
       CHECK_EQUAL((ETL_HAS_MUTABLE_ARRAY_VIEW == 1),           etl::traits::has_mutable_array_view);
       CHECK_EQUAL((ETL_HAS_VIRTUAL_MESSAGES == 1),             etl::traits::has_virtual_messages);
+      CHECK_EQUAL((ETL_HAS_PACKED == 1),                       etl::traits::has_packed);
 
       CHECK_EQUAL((ETL_IS_DEBUG_BUILD == 1),                   etl::traits::is_debug_build);
       CHECK_EQUAL(__cplusplus,                                 etl::traits::cplusplus);
diff --git a/test/test_utility.cpp b/test/test_utility.cpp
index 223058547..5d7e28091 100644
--- a/test/test_utility.cpp
+++ b/test/test_utility.cpp
@@ -718,5 +718,31 @@ namespace
       CHECK_EQUAL(forward_like_call_type::ConstRValue, template_function_fl<TFL&&>(etl::move(u4)));
       CHECK_EQUAL(forward_like_call_type::ConstRValue, template_function_fl<const TFL&&>(etl::move(u4)));
     }
+
+#if ETL_HAS_PACKED
+    //*********************************
+    TEST(test_packed)
+    {
+      struct Unpacked
+      {
+        uint32_t a = 0x12345678;
+        uint8_t  b = 0x9A;
+        uint32_t c = 0x87654321;
+      };
+
+      struct ETL_PACKED Packed
+      {
+        uint32_t a = 0x12345678;
+        uint8_t  b = 0x9A;
+        uint32_t c = 0x87654321;
+      }; ETL_END_PACKED
+
+      Unpacked unpacked;
+      Packed   packed;
+
+      CHECK_TRUE(sizeof(unpacked) > sizeof(packed));
+      CHECK_EQUAL(9U, sizeof(packed));
+    }
+#endif
   };
 }