Merge 5a110847a19e4a758c2f06dab04c21b5e2d844c0 into 60ba92928e8af3441f2a4eea5f18fd2563d98ad0

2026-10-28 18:07:10 +08:00 · 2026-10-19 11:09:20 +00:00 · 2026-10-19 11:09:20 +00:00 · 8a20befca4
commit 8a20befca4
parent 60ba92928e 5a110847a1
16 changed files with 4069 additions and 0 deletions
--- a/.devcontainer/gcc16/Dockerfile
+++ b/.devcontainer/gcc16/Dockerfile
@ -0,0 +1,57 @@
+# Pinned by digest for reproducible builds.
+# To update: docker buildx imagetools inspect debian:sid-slim
+FROM debian:sid-slim@sha256:ec3fa4e0b2987ae47be353f56854191e300261915470e40165b1c906d22a65db
+
+# Pin the package archive to a snapshot.debian.org timestamp so that
+# `apt-get install` resolves the same package versions on every build.
+# This is the snapshot the base image itself was built from - see the comment
+# in /etc/apt/sources.list.d/debian.sources of the pinned image above.
+ARG DEBIAN_SNAPSHOT=20260918T000000Z
+
+# snapshot.debian.org serves archived Release files whose Valid-Until has long
+# since passed, so that check has to be disabled.
+# http is used rather than https because the slim base image has no
+# ca-certificates; integrity is guaranteed by the archive's GPG signature.
+RUN printf '%s\n' \
+    'Types: deb' \
+    "URIs: http://snapshot.debian.org/archive/debian/${DEBIAN_SNAPSHOT}/" \
+    'Suites: sid' \
+    'Components: main' \
+    'Check-Valid-Until: no' \
+    'Signed-By: /usr/share/keyrings/debian-archive-keyring.pgp' \
+    > /etc/apt/sources.list.d/debian.sources
+
+RUN apt-get update && apt-get install -y \
+    build-essential \
+    cmake \
+    git \
+    ninja-build \
+    python3 \
+    python3-cogapp \
+    gcc-16 \
+    g++-16 \
+    && rm -rf /var/lib/apt/lists/*
+
+RUN update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-16 100 \
+    --slave /usr/bin/gcc-ar gcc-ar /usr/bin/gcc-ar-16 \
+    --slave /usr/bin/gcc-nm gcc-nm /usr/bin/gcc-nm-16 \
+    --slave /usr/bin/gcc-ranlib gcc-ranlib /usr/bin/gcc-ranlib-16 \
+    && update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-16 100
+
+# Create non-root user with stable UID/GID
+ARG USERNAME=vscode
+ARG USER_UID=1000
+ARG USER_GID=1000
+
+RUN groupadd --gid ${USER_GID} ${USERNAME} && \
+    useradd --uid ${USER_UID} --gid ${USER_GID} --shell /bin/bash --create-home ${USERNAME}
+
+# Ensure workspace directory ownership for non-root user
+RUN mkdir -p /etl && chown -R ${USERNAME}:${USERNAME} /etl
+
+WORKDIR /etl
+
+# Switch to non-root user
+USER ${USERNAME}
+
+CMD ["/bin/bash"]
--- a/.devcontainer/gcc16/devcontainer.json
+++ b/.devcontainer/gcc16/devcontainer.json
@ -0,0 +1,12 @@
+// For format details, see https://aka.ms/devcontainer.json. For config options, see the
+// README at: https://github.com/devcontainers/templates/tree/main/src/cpp
+//
+// GCC 16 is the reference toolchain for the C++26 static reflection support in
+// etl/meta.h. It cannot use the shared ../Dockerfile because there is no
+// 'gcc:16' base image yet, so gcc-16 is taken from Debian sid instead.
+{
+	"name": "Gcc 16",
+	"build": {
+		"dockerfile": "./Dockerfile"
+	}
+}
--- a/.github/workflows/gcc16-c++26-reflection.yml
+++ b/.github/workflows/gcc16-c++26-reflection.yml
@ -0,0 +1,78 @@
+name: gcc16-c++26-reflection
+on:
+  push:
+    branches: [ master, development, pull-request/* ]
+    paths:
+      - '.github/workflows/**'
+      - 'include/**'
+      - 'test/**'
+      - 'CMakeLists.txt'
+      - 'cmake/**'
+      - '.devcontainer/**'
+  pull_request:
+    branches: [ master, development, pull-request/* ]
+    types: [opened, synchronize, reopened]
+    paths:
+      - '.github/workflows/**'
+      - 'include/**'
+      - 'test/**'
+      - 'CMakeLists.txt'
+      - 'cmake/**'
+      - '.devcontainer/**'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+
+  build-gcc16-cpp26-reflection-stl:
+    name: GCC 16 C++26 Reflection - STL
+    runs-on: ubuntu-24.04
+
+    steps:
+    - uses: actions/checkout@v6.0.3
+      with:
+        persist-credentials: false
+
+    - name: Build Docker image
+      run: docker build -t etl-gcc16 -f .devcontainer/gcc16/Dockerfile .
+
+    - name: Build and run tests
+      run: |
+        docker run --rm --user root -v ${{ github.workspace }}:/etl etl-gcc16 bash -c "\
+          cd /etl && \
+          export CC=gcc-16 && \
+          export CXX=g++-16 && \
+          g++-16 --version && \
+          cmake -G Ninja -B /tmp/build-stl -DBUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=26 -DETL_OPTIMISATION=-O0 /etl/test && \
+          grep -q 'ETL_GNU_HAS_FREFLECTION:INTERNAL=1' /tmp/build-stl/CMakeCache.txt || (echo 'ERROR: -freflection was not detected - C++26 reflection is not being tested.' && exit 1) && \
+          cmake --build /tmp/build-stl -j \$(getconf _NPROCESSORS_ONLN) && \
+          ctest --test-dir /tmp/build-stl --output-on-failure"
+
+  build-gcc16-cpp26-reflection-no-stl:
+    name: GCC 16 C++26 Reflection - No STL
+    runs-on: ubuntu-24.04
+
+    steps:
+    - uses: actions/checkout@v6.0.3
+      with:
+        persist-credentials: false
+
+    - name: Build Docker image
+      run: docker build -t etl-gcc16 -f .devcontainer/gcc16/Dockerfile .
+
+    - name: Build and run tests
+      run: |
+        docker run --rm --user root -v ${{ github.workspace }}:/etl etl-gcc16 bash -c "\
+          cd /etl && \
+          export CC=gcc-16 && \
+          export CXX=g++-16 && \
+          g++-16 --version && \
+          cmake -G Ninja -B /tmp/build-no-stl -DBUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=26 -DETL_OPTIMISATION=-O0 /etl/test && \
+          grep -q 'ETL_GNU_HAS_FREFLECTION:INTERNAL=1' /tmp/build-no-stl/CMakeCache.txt || (echo 'ERROR: -freflection was not detected - C++26 reflection is not being tested.' && exit 1) && \
+          cmake --build /tmp/build-no-stl -j \$(getconf _NPROCESSORS_ONLN) && \
+          ctest --test-dir /tmp/build-no-stl --output-on-failure"
--- a/docs/getting-started/macros.md
+++ b/docs/getting-started/macros.md
@ -103,6 +103,7 @@ These may be defined in the project settings or the user created `etl_profile.h`
 | `ETL_HAS_IDEQUE_REPAIR`              | Set to `1` if the repair functionality for `etl::ideque` is enabled, otherwise `0`.|
 | `ETL_IS_DEBUG_BUILD`                 | Set to `1` if in a debug build, otherwise `0`.|
 | `ETL_HAS_POLYMORPHIC_MESSAGES`       | Set to `1` if messages are polymorphic, otherwise `0`.|
+| `ETL_HAS_REFLECTION`                 | Defined by `etl/meta.h`. Set to `1` if the compiler supports C++26 static reflection (P2996) and `etl::meta` is available, otherwise `0`.|
 | `ETL_HAS_ERROR_ON_STRING_TRUNCATION` | Set to `1` if truncated strings are an error, otherwise `0`.|
 | `ETL_USING_LIBC_WCHAR_H`             | These macros will be defined as `0` & `1` depending on whether `ETL_NO_LIBC_WCHAR_H` is defined or not.|
 | `ETL_NOT_USING_LIBC_WCHAR_H`         | Inversion of `ETL_USING_LIBC_WCHAR_H`.|
--- a/docs/types/meta.md
+++ b/docs/types/meta.md
@ -0,0 +1,97 @@
+---
+title: "meta"
+---
+
+{{< callout type="info">}}
+  Header: `meta.h`  
+  From: `20.50.0`  
+  Similar to: `std::meta`
+{{< /callout >}}
+
+C++26 static reflection (P2996) in namespace `etl::meta`.
+
+`etl::meta` mirrors `std::meta`, but is usable in both STL and non-STL builds.
+In an STL build it is a thin layer of using-declarations over `std::meta`.
+In a non-STL build ETL supplies the minimal declarations that the compiler's
+reflection builtins require, so no standard library is needed.
+
+```cpp
+#include "etl/meta.h"
+```
+
+## Compiler support
+
+Static reflection is a very new language feature, and at the time of writing
+**GCC 16** is the only compiler that implements enough of P2996 to be usable.
+Clang (including the Bloomberg `clang-p2996` fork) and MSVC are not supported.
+
+`etl/meta.h` may always be included. It defines a single macro,
+`ETL_HAS_REFLECTION`, as `1` or `0`; when it is `0` the header defines nothing
+else. This is the only reflection feature switch in the ETL, and user code
+should test it before using anything in `etl::meta`.
+
+```cpp
+#include "etl/meta.h"
+
+#if ETL_HAS_REFLECTION
+  static_assert(etl::meta::identifier_of(^^my_type) == "my_type");
+#endif
+```
+
+GCC requires the `-freflection` option in addition to `-std=c++26`.
+The reference toolchain is defined in `.devcontainer/gcc16`.
+
+## Usage
+
+Names are used exactly as their `std::meta` equivalents.
+
+```cpp
+struct point
+{
+  int x;
+  int y;
+};
+
+constexpr auto members =
+  etl::meta::nonstatic_data_members_of(^^point,
+                                       etl::meta::access_context::unchecked());
+
+static_assert(etl::meta::identifier_of(members[0]) == "x");
+static_assert(etl::meta::type_of(members[0])       == ^^int);
+static_assert(etl::meta::size_of(^^point)          == 2 * sizeof(int));
+```
+
+`identifier_of`, `display_string_of` and `symbol_of` return `std::string_view`
+in an STL build and `etl::string_view` in a non-STL build.
+
+## info_array
+
+GCC cannot keep the heap allocation of a `std::vector<info>` alive across a
+constant evaluation, so a `template for` over the result of `members_of` does
+not compile. `etl::meta::info_array` is a fixed-size, allocation-free array of
+`info` that can be iterated instead.
+
+```cpp
+constexpr auto ctx = etl::meta::access_context::unchecked();
+constexpr auto count = etl::meta::nonstatic_data_members_of(^^point, ctx).size();
+constexpr auto members =
+  etl::meta::to_info_array<count>(etl::meta::nonstatic_data_members_of(^^point, ctx));
+
+template for (constexpr auto member : members)
+{
+  // ...
+}
+```
+
+| Member | Description |
+|--------|-------------|
+| `begin()` | Pointer to the first element. |
+| `end()` | Pointer past the last element. |
+| `size()` | The number of elements. |
+| `operator[](size_t)` | The element at the index. |
+
+All members are `consteval`.
+
+## Tests
+
+`test_meta.cpp`
--- a/include/etl/meta.h
+++ b/include/etl/meta.h
@ -0,0 +1,73 @@
+///\file
+
+/******************************************************************************
+The MIT License(MIT)
+
+Embedded Template Library.
+https://github.com/ETLCPP/etl
+https://www.etlcpp.com
+
+Copyright(c) 2026 BMW AG
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files(the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions :
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+******************************************************************************/
+
+#ifndef ETL_META_INCLUDED
+#define ETL_META_INCLUDED
+
+#include "platform.h"
+
+//*****************************************************************************
+/// \defgroup meta meta
+/// C++26 static reflection (P2996).
+/// \ingroup etl
+//*****************************************************************************
+
+//*****************************************************************************
+// This is the one and only place where reflection support is detected.
+//
+// GCC 16 is currently the only compiler that implements enough of P2996 for
+// etl::meta, and it does so for both STL and non-STL builds.
+// See .devcontainer/gcc16 for the reference toolchain.
+//
+// Clang (including the Bloomberg p2996 fork) and MSVC are not supported yet.
+//
+// ETL_HAS_REFLECTION is always defined, as 1 or 0.
+// When it is 0 this header defines nothing else, so user code can include
+// etl/meta.h unconditionally and test ETL_HAS_REFLECTION.
+//*****************************************************************************
+#if defined(ETL_COMPILER_GCC) && defined(__cpp_impl_reflection) && (__cpp_impl_reflection >= 202506L)
+  #define ETL_HAS_REFLECTION 1
+#else
+  #define ETL_HAS_REFLECTION 0
+#endif
+
+#if ETL_HAS_REFLECTION
+  #if ETL_USING_STL
+    // The full standard library is available, so etl::meta is a thin
+    // using-declaration layer over std::meta.
+    #include "private/meta/stl.h"
+  #else
+    // No standard library: etl::meta supplies the minimal std declarations
+    // that the reflection builtins require.
+    #include "private/meta/gcc.h"
+  #endif
+#endif
+
+#endif // ETL_META_INCLUDED
--- a/include/etl/private/meta/gcc.h
+++ b/include/etl/private/meta/gcc.h
--- a/include/etl/private/meta/stl.h
+++ b/include/etl/private/meta/stl.h
@ -0,0 +1,117 @@
+///\file
+
+/******************************************************************************
+The MIT License(MIT)
+
+Embedded Template Library.
+https://github.com/ETLCPP/etl
+https://www.etlcpp.com
+
+Copyright(c) 2026 BMW AG
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files(the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions :
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+******************************************************************************/
+
+#ifndef ETL_PRIVATE_META_STL_H_INCLUDED
+#define ETL_PRIVATE_META_STL_H_INCLUDED
+
+#include <cstddef>
+#include <initializer_list>
+#include <optional>
+#include <string>
+#include <string_view>
+#include <vector>
+
+#include <meta>
+#include <source_location> // Workaround for GCC 16: <meta> depends on <source_location> but does not include it.
+
+///\defgroup meta meta
+///\ingroup etl
+
+namespace etl
+{
+  namespace meta
+  {
+    //*************************************************************************
+    // Standard <meta> path, used when the full standard library is available.
+    //
+    // A using-directive is sufficient here: qualified lookup for
+    // etl::meta::foo also searches the namespaces nominated by the
+    // using-directives of etl::meta ([namespace.qual]), so every std::meta
+    // name - including the function templates such as extract<> - is
+    // reachable as etl::meta::name.  This mirrors the non-STL implementation
+    // in gcc.h, which uses the same mechanism.
+    //*************************************************************************
+    using namespace std::meta;
+
+    // Enumerators of std::meta::operators (op_equals_equals, etc.) are scoped,
+    // so they need a using-enum-declaration rather than the using-directive.
+    using enum std::meta::operators;
+
+    //*************************************************************************
+    /// info_array — fixed-size, zero-allocation array of info values.
+    ///
+    /// GCC limitation: template-for over a std::vector<info> fails because the
+    /// vector's heap allocation cannot persist in a constant expression.  The
+    /// workaround is to copy the elements into a plain aggregate array (no
+    /// allocation) and iterate that instead.
+    ///
+    /// Usage pattern:
+    ///   constexpr auto N   = std::meta::members_of(^^T, ctx).size();
+    ///   constexpr auto arr = etl::meta::to_info_array<N>(
+    ///                            std::meta::members_of(^^T, ctx));
+    ///   template for (constexpr auto m : arr) { ... }
+    //*************************************************************************
+    template <size_t N>
+    struct info_array
+    {
+      info                  elems[N > 0 ? N : 1]{};
+      consteval const info* begin() const
+      {
+        return elems;
+      }
+      consteval const info* end() const
+      {
+        return elems + N;
+      }
+      consteval size_t size() const
+      {
+        return N;
+      }
+      consteval const info& operator[](size_t i) const
+      {
+        return elems[i];
+      }
+    };
+
+    template <size_t N>
+    consteval info_array<N> to_info_array(const std::vector<info>& v)
+    {
+      info_array<N> a{};
+      for (size_t i = 0; i < N; ++i)
+      {
+        a.elems[i] = v[i];
+      }
+      return a;
+    }
+
+  } // namespace meta
+} // namespace etl
+
+#endif // ETL_PRIVATE_META_STL_H_INCLUDED
--- a/include/etl/type_traits.h
+++ b/include/etl/type_traits.h
@ -3808,9 +3808,14 @@ namespace etl
  template <typename T>
  struct is_nothrow_relocatable
  {
+  #if ETL_USING_CPP11
    static ETL_CONSTANT bool value = etl::is_trivially_relocatable<T>::value
                             || (etl::is_nothrow_move_constructible<typename etl::remove_all_extents<T>::type>::value
                                 && etl::is_nothrow_destructible<typename etl::remove_all_extents<T>::type>::value);
+  #else
+    // No move semantics: only trivially relocatable types are known to be nothrow relocatable.
+    static ETL_CONSTANT bool value = etl::is_trivially_relocatable<T>::value;
+  #endif
  };

 #elif defined(ETL_USER_DEFINED_TYPE_TRAITS) && !defined(ETL_USE_TYPE_TRAITS_BUILTINS)
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@ -1,6 +1,8 @@
 cmake_minimum_required(VERSION 3.10)
 project(etl_unit_tests LANGUAGES CXX)

+include(CheckCXXCompilerFlag)
+
 #include(FetchContent)
 #FetchContent_Declare(
 #  googletest
@ -232,6 +234,7 @@ add_executable(etl_tests
 	test_map.cpp
 	test_math.cpp
 	test_math_functions.cpp
+	test_meta.cpp
 	test_mean.cpp
 	test_memory.cpp
 	test_mem_cast.cpp
@ -513,6 +516,16 @@ if (CMAKE_CXX_COMPILER_ID MATCHES "GNU")
 			${EXTRA_COMPILE_OPTIONS}
 			)
 	target_link_options(etl_tests PRIVATE ${EXTRA_LINK_OPTIONS})
+
+	if (ETL_CXX_STANDARD MATCHES "26")
+		# -freflection is only accepted when compiling as C++26, so probe with that standard.
+		set(CMAKE_REQUIRED_FLAGS "-std=c++26")
+		check_cxx_compiler_flag(-freflection ETL_GNU_HAS_FREFLECTION)
+		unset(CMAKE_REQUIRED_FLAGS)
+		if (ETL_GNU_HAS_FREFLECTION)
+			target_compile_options(etl_tests PRIVATE -freflection)
+		endif ()
+	endif ()
 endif ()

 if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
--- a/test/meson.build
+++ b/test/meson.build
@ -234,6 +234,7 @@ etl_test_sources = files(
 	'test_message_timer_atomic.cpp',
 	'test_message_timer_interrupt.cpp',
 	'test_message_timer_locked.cpp',
+	'test_meta.cpp',
 	'test_multi_array.cpp',
 	'test_multi_range.cpp',
 	'test_multi_span.cpp',
--- a/test/syntax_check/CMakeLists.txt
+++ b/test/syntax_check/CMakeLists.txt
@ -289,6 +289,7 @@ target_sources(tests PRIVATE
 		message_timer_interrupt.h.t.cpp
 		message_timer_locked.h.t.cpp
 		message_types.h.t.cpp
+                meta.h.t.cpp
 		multimap.h.t.cpp
 		multiset.h.t.cpp
 		multi_array.h.t.cpp
--- a/test/syntax_check/meta.h.t.cpp
+++ b/test/syntax_check/meta.h.t.cpp
@ -0,0 +1,40 @@
+/******************************************************************************
+The MIT License(MIT)
+
+Embedded Template Library.
+https://github.com/ETLCPP/etl
+https://www.etlcpp.com
+
+Copyright(c) 2026 BMW AG
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files(the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions :
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+******************************************************************************/
+
+#include <etl/meta.h>
+
+// etl/meta.h must be includable unconditionally, on every compiler and every
+// language standard.  Where reflection is unavailable it defines nothing
+// except ETL_HAS_REFLECTION, which is always defined as either 1 or 0.
+#if !defined(ETL_HAS_REFLECTION)
+  #error ETL_HAS_REFLECTION is not defined by etl/meta.h
+#endif
+
+#if (ETL_HAS_REFLECTION != 0) && (ETL_HAS_REFLECTION != 1)
+  #error ETL_HAS_REFLECTION must be defined as 0 or 1
+#endif
--- a/test/test_meta.cpp
+++ b/test/test_meta.cpp
--- a/test/vs2022/etl.vcxproj
+++ b/test/vs2022/etl.vcxproj
@ -10447,6 +10447,7 @@
    <ClCompile Include="..\test_message_timer_atomic.cpp" />
    <ClCompile Include="..\test_message_timer_interrupt.cpp" />
    <ClCompile Include="..\test_message_timer_locked.cpp" />
+    <ClCompile Include="..\test_meta.cpp" />
    <ClCompile Include="..\test_multi_array.cpp" />
    <ClCompile Include="..\test_array.cpp">
      <AdditionalIncludeDirectories Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">../../../unittest-cpp</AdditionalIncludeDirectories>
--- a/test/vs2022/etl.vcxproj.filters
+++ b/test/vs2022/etl.vcxproj.filters
@ -1664,6 +1664,9 @@
    <ClCompile Include="..\test_message_timer_locked.cpp">
      <Filter>Tests\Messaging</Filter>
    </ClCompile>
+    <ClCompile Include="..\test_meta.cpp">
+      <Filter>Tests\Types</Filter>
+    </ClCompile>
    <ClCompile Include="..\test_shared_message.cpp">
      <Filter>Tests\Messaging</Filter>
    </ClCompile>