PR fixes #verification

1. Less `auto` according AUTOSAR A7-1-5
2. Less `struct` according AUTOSAR A11-0-2
3. C.35: A base class destructor should be either public and virtual, or protected and non-virtual.
4. `IMedia::setFilters` now fallible.

include/libcyphal/transport/can/media.hpp

@@ -40,6 +40,7 @@ class IMedia
     IMedia(const IMedia&)            = delete;
     IMedia& operator=(IMedia&&)      = delete;
     IMedia& operator=(const IMedia&) = delete;
+    virtual ~IMedia()                = default;
 
     /// @brief Get the maximum transmission unit (MTU) of the CAN bus.
     ///
@@ -55,9 +56,9 @@ class IMedia
     /// While reconfiguration is in progress, incoming frames may be lost and/or unwanted frames may be received.
     /// The lifetime of the filter array may end upon return (no references retained).
     ///
-    /// @return Returns `true` on success, `false` in case of a low-level error (e.g., IO error).
+    /// @return Returns `nullopt` on success; otherwise some `MediaError` in case of a low-level error.
     ///
-    CETL_NODISCARD virtual bool setFilters(const Filters filters) noexcept = 0;
+    CETL_NODISCARD virtual cetl::optional<MediaError> setFilters(const Filters filters) noexcept = 0;
 
     /// @brief Schedules the frame for transmission asynchronously and return immediately.
     ///
@@ -76,8 +77,7 @@ class IMedia
         const cetl::span<cetl::byte> payload_buffer) noexcept = 0;
 
 protected:
-    IMedia()          = default;
-    virtual ~IMedia() = default;
+    IMedia() = default;
 
 };  // IMedia
 

include/libcyphal/transport/can/transport.hpp

@@ -51,8 +51,9 @@ class TransportImpl final : public ICanTransport
     }
     CETL_NODISCARD ProtocolParams getProtocolParams() const noexcept override
     {
-        const auto min_mtu = reduceMediaInto(std::numeric_limits<std::size_t>::max(),
-                                             [](auto&& mtu, IMedia& media) { mtu = std::min(mtu, media.getMtu()); });
+        const auto min_mtu =
+            reduceMediaInto(std::numeric_limits<std::size_t>::max(),
+                            [](std::size_t&& mtu, IMedia& media) { mtu = std::min(mtu, media.getMtu()); });
         return ProtocolParams{1 << CANARD_TRANSFER_ID_BIT_LENGTH, min_mtu, CANARD_NODE_ID_MAX + 1};
     }
 
@@ -99,7 +100,7 @@ class TransportImpl final : public ICanTransport
     // TODO: Remove this workaround when the issue is resolved.
     // see https://github.com/OpenCyphal/libcanard/issues/216
     //
-    struct CanardMemory
+    struct CanardMemory final
     {
         alignas(std::max_align_t) std::size_t size;
     };
@@ -116,8 +117,8 @@ class TransportImpl final : public ICanTransport
     {
         auto& self = getSelfFrom(ins);
 
-        const auto memory_size   = sizeof(CanardMemory) + amount;
-        auto       canard_memory = static_cast<CanardMemory*>(self.memory_.allocate(memory_size));
+        const std::size_t memory_size   = sizeof(CanardMemory) + amount;
+        auto              canard_memory = static_cast<CanardMemory*>(self.memory_.allocate(memory_size));
         if (canard_memory == nullptr)
         {
             return nullptr;
@@ -144,20 +145,10 @@ class TransportImpl final : public ICanTransport
         self.memory_.deallocate(canard_memory, canard_memory->size);
     }
 
-    template <typename Action>
-    void forEachMedia(Action action)
-    {
-        for (const auto media : media_array_)
-        {
-            CETL_DEBUG_ASSERT(media != nullptr, "Expected media interface.");
-            action(std::ref(*media));
-        }
-    }
-
     template <typename T, typename Reducer>
     T reduceMediaInto(T&& init, Reducer reducer) const
     {
-        for (const auto media : media_array_)
+        for (IMedia* const media : media_array_)
         {
             CETL_DEBUG_ASSERT(media != nullptr, "Expected media interface.");
             reducer(std::forward<T>(init), std::ref(*media));
@@ -188,8 +179,8 @@ CETL_NODISCARD inline Expected<UniquePtr<ICanTransport>, FactoryError> makeTrans
     // - At least one media interface must be provided.
     // - If a local node ID is provided, it must be within the valid range.
     //
-    const auto media_count =
-        static_cast<std::size_t>(std::count_if(media.cbegin(), media.cend(), [](auto m) { return m != nullptr; }));
+    const auto media_count = static_cast<std::size_t>(
+        std::count_if(media.cbegin(), media.cend(), [](IMedia* const m) { return m != nullptr; }));
     if (media_count == 0)
     {
         return ArgumentError{};
@@ -201,7 +192,9 @@ CETL_NODISCARD inline Expected<UniquePtr<ICanTransport>, FactoryError> makeTrans
 
     libcyphal::detail::VarArray<IMedia*> media_array{MaxMediaInterfaces, &memory};
     media_array.reserve(media_count);
-    std::copy_if(media.cbegin(), media.cend(), std::back_inserter(media_array), [](auto m) { return m != nullptr; });
+    std::copy_if(media.cbegin(), media.cend(), std::back_inserter(media_array), [](IMedia* const m) {
+        return m != nullptr;
+    });
     CETL_DEBUG_ASSERT(!media_array.empty() && (media_array.size() == media_count), "");
 
     const auto canard_node_id = static_cast<CanardNodeID>(local_node_id.value_or(CANARD_NODE_ID_UNSET));

include/libcyphal/transport/errors.hpp

@@ -48,7 +48,7 @@ using FactoryError = cetl::variant<ArgumentError, MemoryError, NotImplementedErr
 
 /// @brief Defines any possible error at Cyphal media layer.
 ///
-using MediaError = cetl::variant<ArgumentError, PlatformError>;
+using MediaError = cetl::variant<ArgumentError, PlatformError, CapacityError>;
 
 }  // namespace transport
 }  // namespace libcyphal

include/libcyphal/transport/multiplexer.hpp

@@ -18,12 +18,12 @@ class IMultiplexer
     IMultiplexer(const IMultiplexer&)            = delete;
     IMultiplexer& operator=(IMultiplexer&&)      = delete;
     IMultiplexer& operator=(const IMultiplexer&) = delete;
+    virtual ~IMultiplexer()                      = default;
 
     // TODO: Add methods here
 
 protected:
-    IMultiplexer()          = default;
-    virtual ~IMultiplexer() = default;
+    IMultiplexer() = default;
 
 };  // IMultiplexer
 

include/libcyphal/transport/udp/media.hpp

@@ -20,12 +20,12 @@ class IMedia
     IMedia(const IMedia&)            = delete;
     IMedia& operator=(IMedia&&)      = delete;
     IMedia& operator=(const IMedia&) = delete;
+    virtual ~IMedia()                = default;
 
     // TODO: Add methods here
 
 protected:
-    IMedia()          = default;
-    virtual ~IMedia() = default;
+    IMedia() = default;
 
 };  // IMedia
 

test/unittest/transport/can/media_mock.hpp

@@ -21,7 +21,7 @@ class MediaMock : public IMedia
 {
 public:
     MOCK_METHOD(std::size_t, getMtu, (), (const, noexcept, override));
-    MOCK_METHOD(bool, setFilters, (const Filters filters), (noexcept, override));
+    MOCK_METHOD(cetl::optional<MediaError>, setFilters, (const Filters filters), (noexcept, override));
     MOCK_METHOD((Expected<bool, MediaError>),
                 push,
                 (const TimePoint deadline, const CanId can_id, const cetl::span<const cetl::byte> payload),

test/unittest/transport/test_dynamic_buffer.cpp

@@ -30,7 +30,7 @@ class InterfaceMock : public DynamicBuffer::Interface
     MOCK_METHOD(std::size_t, size, (), (const, noexcept, override));
     MOCK_METHOD(std::size_t, copy, (const std::size_t, void* const, const std::size_t), (const, override));
 };
-class InterfaceWrapper : public rtti_helper<TestTypeIdType, DynamicBuffer::Interface>
+class InterfaceWrapper final : public rtti_helper<TestTypeIdType, DynamicBuffer::Interface>
 {
 public:
     explicit InterfaceWrapper(InterfaceMock* mock)