Module target by Neargye · Pull Request #465 · Neargye/magic_enum

Neargye · 2026-08-03T10:35:01Z

No description provided.

ClausKlein · 2026-08-06T10:31:20Z

LGTM: tested only with GNU 16.1.0 on OSX!

But MAGIC_ENUM_MODULE_WITH_FMT does not compile with import std; or MAGIC_ENUM_USE_MODULES!

IMHO I should not needed in this case.

I would change a view points and the test script:

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 76f3056..c6b365b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -102,7 +102,7 @@ if(MAGIC_ENUM_OPT_VERIFY_INTERFACE_HEADER_SETS)
   if(CMAKE_VERSION VERSION_LESS "3.24")
     message(FATAL_ERROR "MAGIC_ENUM_OPT_VERIFY_INTERFACE_HEADER_SETS requires CMake >= 3.24")
   endif()
-  set_property(TARGET ${PROJECT_NAME} PROPERTY VERIFY_INTERFACE_HEADER_SETS ON)
+  set_property(TARGET ${PROJECT_NAME} PROPERTY VERIFY_INTERFACE_HEADER_SETS ${PROJECT_IS_TOP_LEVEL})
 endif()
 
 function(magic_enum_make_module_library name)
@@ -124,13 +124,18 @@ function(magic_enum_make_module_library name)
     if(NOT TARGET fmt::fmt)
       find_package(fmt CONFIG REQUIRED)
     endif()
-    target_link_libraries(${name} PUBLIC fmt::fmt)
-    target_compile_definitions(${name} PRIVATE MAGIC_ENUM_MODULE_WITH_FMT)
+    if(MAGIC_ENUM_USE_MODULES AND TARGET fmt::fmt-module)
+      # FIXME: this does not compile! CK
+      target_link_libraries(${name} PUBLIC fmt::fmt-module)
+    else()
+      target_link_libraries(${name} PUBLIC fmt::fmt)
+    endif()
+    target_compile_definitions(${name} PUBLIC MAGIC_ENUM_MODULE_WITH_FMT)
   endif()
 
   if(MAGIC_ENUM_MODULE_IMPORT_STD)
-    if(CMAKE_VERSION VERSION_LESS "3.30")
-      message(FATAL_ERROR "MAGIC_ENUM_MODULE_IMPORT_STD requires CMake >= 3.30")
+    if(CMAKE_VERSION VERSION_LESS "3.31")
+      message(FATAL_ERROR "MAGIC_ENUM_MODULE_IMPORT_STD requires CMake >= 3.31")
     endif()
     if(CMAKE_CXX_STANDARD LESS 23)
       message(FATAL_ERROR "MAGIC_ENUM_MODULE_IMPORT_STD requires CMAKE_CXX_STANDARD >= 23")
@@ -143,7 +148,7 @@ function(magic_enum_make_module_library name)
     endif()
     message(STATUS "${name}: using import std")
     set_property(TARGET ${name} PROPERTY CXX_MODULE_STD ON)
-    target_compile_definitions(${name} PRIVATE MAGIC_ENUM_USE_STD_MODULE)
+    target_compile_definitions(${name} PUBLIC MAGIC_ENUM_USE_STD_MODULE)
   elseif(CMAKE_VERSION VERSION_GREATER_EQUAL "3.30")
     set_property(TARGET ${name} PROPERTY CXX_MODULE_STD OFF)
   endif()
diff --git a/test_installed_version.bash b/test_installed_version.bash
index 8c3705e..6444962 100644
--- a/test_installed_version.bash
+++ b/test_installed_version.bash
@@ -9,33 +9,53 @@ install_dir="${build_root}/install"
 consumer_prefix="${build_root}/relocated-install"
 cmake_consumer_build_dir="${build_root}/cmake-consumer"
 pkgconfig_consumer_build_dir="${build_root}/pkgconfig-consumer"
+cxx_modules_consumer_build_dir="${build_root}/cxx_modules-consumer"
 
 test_installed_consumer() {
   local build_dir="$1"
   shift
 
   CMAKE_PREFIX_PATH="${consumer_prefix}" cmake -S "${repo_root}" -B "${build_dir}" \
+    -G Ninja \
     -DCMAKE_BUILD_TYPE=Debug \
     "$@"
   cmake --build "${build_dir}" --parallel
   ctest --test-dir "${build_dir}" --output-on-failure --no-tests=error
 }
 
+cmake --version
 cmake -E remove_directory "${build_root}"
 
-cmake -S "${repo_root}" -B "${source_build_dir}" \
+cmake -S "${repo_root}" -B "${source_build_dir}" -G Ninja \
   -DCMAKE_BUILD_TYPE=Release \
+  -DCMAKE_CXX_STANDARD=23 \
+  -DCMAKE_EXPERIMENTAL_CXX_IMPORT_STD=f35a9ac6-8463-4d38-8eec-5d6008153e7d \
   -DCMAKE_INSTALL_PREFIX="${configured_install_dir}" \
+  -DMAGIC_ENUM_MODULE_IMPORT_STD=ON \
+  -DMAGIC_ENUM_MODULE_WITH_FMT=OFF \
   -DMAGIC_ENUM_OPT_BUILD_EXAMPLES=OFF \
   -DMAGIC_ENUM_OPT_BUILD_TESTS=OFF \
   -DMAGIC_ENUM_OPT_INSTALL=ON \
-  -DMAGIC_ENUM_OPT_VERIFY_INTERFACE_HEADER_SETS=ON
+  -DMAGIC_ENUM_OPT_VERIFY_INTERFACE_HEADER_SETS=ON \
+  -DMAGIC_ENUM_USE_MODULES=ON
 cmake --build "${source_build_dir}" \
   --target magic_enum_verify_interface_header_sets \
   --parallel
+cmake --build "${source_build_dir}" \
+  --target all \
+  --parallel
 cmake --install "${source_build_dir}" --prefix "${install_dir}"
 cmake -E copy_directory "${install_dir}" "${consumer_prefix}"
 
+test_installed_consumer "${cxx_modules_consumer_build_dir}" \
+  -DCMAKE_CXX_STANDARD=23 \
+  -DCMAKE_EXPERIMENTAL_CXX_IMPORT_STD=f35a9ac6-8463-4d38-8eec-5d6008153e7d \
+  -DMAGIC_ENUM_MODULE_IMPORT_STD=ON \
+  -DMAGIC_ENUM_MODULE_WITH_FMT=OFF \
+  -DMAGIC_ENUM_OPT_TEST_INSTALLED_VERSION=ON \
+  -DMAGIC_ENUM_USE_MODULES=ON \
+  -DPKG_CONFIG_USE_CMAKE_PREFIX_PATH=OFF --fresh
+
 test_installed_consumer "${cmake_consumer_build_dir}" \
   -DMAGIC_ENUM_OPT_TEST_INSTALLED_VERSION=ON

ClausKlein · 2026-08-06T19:22:21Z

Please note: fmt lib is still NOT proper build and installed with CXX_MODULES!

I opened a bunch of issues, but they are all ignored and closed at fmt lib?

IMHO: if you build with import std; you should never need the fmt lib, use std:format please.

bash-5.3$ builddriver ninja
builddriver executing: 'ninja'
Compilation FAILED in 1.714425 seconds
Number of warnings: 0
Number of errors: 1914
Last Error:
  Message: "template constraint failure for 'template<class _It>  requires  input_iterator<_It> using std::const_iterator = std::__conditional_t<__constant_iterator<_It>, _It, std::basic_const_iterator<_It> >'"
  Path: /usr/local/Cellar/gcc/16.1.0/include/c++/16/span
  Line Number: 166
  Column: 13
For full log, please open: /var/folders/wb/ckvxxgls5db7qyhqq4y5_l1c0000gq/T/build-mocbts17.log
bash-5.3$ cmake -L .
-- magic_enum module: using fmt::fmt
-- Configuring done (0.1s)
CMake Warning (experimental) in CMakeLists.txt:
  CMake's support for `import std;` in C++23 and newer is experimental.  It
  is meant only for experimentation and feedback to CMake developers.
This warning is for project developers.  Use -Wno-author or -Wno-experimental
to suppress it.

-- Generating done (0.0s)
-- Build files have been written to: /Users/clausklein/Workspace/cpp/magic_enum/build-installed-version/source
-- Cache values
CMAKE_BUILD_TYPE:STRING=Release
CMAKE_CXX_COMPILER_LAUNCHER:STRING=ccache
CMAKE_INSTALL_PREFIX:PATH=/Users/clausklein/Workspace/cpp/magic_enum/build-installed-version/configured-install
CMAKE_OSX_ARCHITECTURES:STRING=
CMAKE_OSX_DEPLOYMENT_TARGET:STRING=
CMAKE_OSX_SYSROOT:STRING=
MAGIC_ENUM_MODULE_IMPORT_STD:BOOL=OFF
MAGIC_ENUM_MODULE_WITH_FMT:BOOL=ON
MAGIC_ENUM_OPT_BUILD_EXAMPLES:BOOL=OFF
MAGIC_ENUM_OPT_BUILD_TESTS:BOOL=OFF
MAGIC_ENUM_OPT_INSTALL:BOOL=ON
MAGIC_ENUM_OPT_INSTALL_PACKAGE_XML:BOOL=ON
MAGIC_ENUM_OPT_TEST_INSTALLED_VERSION:BOOL=OFF
MAGIC_ENUM_OPT_TEST_INSTALLED_VERSION_PKGCONFIG:BOOL=OFF
MAGIC_ENUM_OPT_VERIFY_INTERFACE_HEADER_SETS:BOOL=ON
MAGIC_ENUM_USE_MODULES:BOOL=ON
fmt_DIR:PATH=/Users/clausklein/.local/lib/cmake/fmt
bash-5.3$ pwd
/Users/clausklein/Workspace/cpp/magic_enum/build-installed-version/source
bash-5.3$ echo $CXX
g++-16
bash-5.3$

ClausKlein · 2026-08-07T15:02:38Z

Sorry to bother you, but if fmt lib use import std; too, this does still not work.

fmt lib was right build and installed from my PR:

[1/7] /Users/clausklein/.local/bin/cmake -E cmake_ninja_dyndep --tdi=CMakeFiles/@cmake_cxx_std.dir/CXXDependInfo.json --lang=CXX --modmapfmt=gcc --dd='CMakeFiles/@cmake_cxx_std.dir/CXX.dd' @'CMakeFiles/@cmake_cxx_std.dir/CXX.dd'.rsp
[2/7] /Users/clausklein/.local/bin/cmake -E cmake_ninja_dyndep --tdi=CMakeFiles/@cmake_cxx_std@synth_0.dir/CXXDependInfo.json --lang=CXX --modmapfmt=gcc --dd='CMakeFiles/@cmake_cxx_std@synth_0.dir/CXX.dd' @'CMakeFiles/@cmake_cxx_std@synth_0.dir/CXX.dd'.rsp
[3/6] /Users/clausklein/.local/bin/cmake -E cmake_ninja_dyndep --tdi=CMakeFiles/fmt__fmt@synth_0.dir/CXXDependInfo.json --lang=CXX --modmapfmt=gcc --dd='CMakeFiles/fmt__fmt@synth_0.dir/CXX.dd' @'CMakeFiles/fmt__fmt@synth_0.dir/CXX.dd'.rsp
[4/6] /Users/clausklein/.local/bin/cmake -E cmake_ninja_dyndep --tdi=CMakeFiles/magic_enum_module.dir/CXXDependInfo.json --lang=CXX --modmapfmt=gcc --dd=CMakeFiles/magic_enum_module.dir/CXX.dd @CMakeFiles/magic_enum_module.dir/CXX.dd.rsp

[5/6] ccache /usr/local/bin/g++-16 -DFMT_IMPORT_STD -DFMT_MODULE
-DMAGIC_ENUM_USE_FMT_HEADER -I/Users/clausklein/Workspace/cpp/magic_enum/include
-isystem /Users/clausklein/.local/include -O3 -DNDEBUG -std=c++26 -MD -MT
CMakeFiles/magic_enum_module.dir/module/magic_enum.cppm.o -MF
CMakeFiles/magic_enum_module.dir/module/magic_enum.cppm.o.d -fmodules-ts
-fmodule-mapper=CMakeFiles/magic_enum_module.dir/module/magic_enum.cppm.o.modmap
-MD -fdeps-format=p1689r5 -x c++ -o
CMakeFiles/magic_enum_module.dir/module/magic_enum.cppm.o -c
/Users/clausklein/Workspace/cpp/magic_enum/module/magic_enum.cppm

FAILED: [code=1] CMakeFiles/magic_enum_module.dir/module/magic_enum.cppm.o CMakeFiles/magic_enum_module.dir/magic_enum.gcm 
ccache /usr/local/bin/g++-16 -DFMT_IMPORT_STD -DFMT_MODULE -DMAGIC_ENUM_USE_FMT_HEADER -I/Users/clausklein/Workspace/cpp/magic_enum/include -isystem /Users/clausklein/.local/include -O3 -DNDEBUG -std=c++26 -MD -MT CMakeFiles/magic_enum_module.dir/module/magic_enum.cppm.o -MF CMakeFiles/magic_enum_module.dir/module/magic_enum.cppm.o.d -fmodules-ts -fmodule-mapper=CMakeFiles/magic_enum_module.dir/module/magic_enum.cppm.o.modmap -MD -fdeps-format=p1689r5 -x c++ -o CMakeFiles/magic_enum_module.dir/module/magic_enum.cppm.o -c /Users/clausklein/Workspace/cpp/magic_enum/module/magic_enum.cppm
In file included from /Users/clausklein/.local/include/fmt/format.h:41,
                 from /Users/clausklein/Workspace/cpp/magic_enum/module/magic_enum.cppm:5:
/Users/clausklein/.local/include/fmt/base.h:312:35: error: 'enable_if' in namespace 'std' does not name a template type
  312 | using enable_if_t = typename std::enable_if<B, T>::type;
      |                                   ^~~~~~~~~
/Users/clausklein/.local/include/fmt/base.h:1:1: note: 'std::enable_if' is defined in header '<type_traits>'; this is probably fixable by adding '#include <type_traits>'
  +++ |+#include <type_traits>
    1 | // Formatting library for C++ - the base API for char/UTF-8
/Users/clausklein/.local/include/fmt/base.h:314:37: error: 'conditional' in namespace 'std' does not name a template type
  314 | using conditional_t = typename std::conditional<B, T, F>::type;
      |                                     ^~~~~~~~~~~
/Users/clausklein/.local/include/fmt/base.h:315:46: error: 'integral_constant' in namespace 'std' does not name a template type
  315 | template <bool B> using bool_constant = std::integral_constant<bool, B>;
      |                                              ^~~~~~~~~~~~~~~~~
/Users/clausklein/.local/include/fmt/base.h:317:42: error: 'remove_reference' in namespace 'std' does not name a template type
  317 | using remove_reference_t = typename std::remove_reference<T>::type;
      |                                          ^~~~~~~~~~~~~~~~
/Users/clausklein/.local/include/fmt/base.h:319:38: error: 'remove_const' in namespace 'std' does not name a template type
  319 | using remove_const_t = typename std::remove_const<T>::type;
      |                                      ^~~~~~~~~~~~
/Users/clausklein/.local/include/fmt/base.h:321:38: error: 'remove_cv' in namespace 'std' does not name a template type
  321 | using remove_cvref_t = typename std::remove_cv<remove_reference_t<T>>::type;
      |                                      ^~~~~~~~~
/Users/clausklein/.local/include/fmt/base.h:323:39: error: 'make_unsigned' in namespace 'std' does not name a template type
  323 | using make_unsigned_t = typename std::make_unsigned<T>::type;
      |                                       ^~~~~~~~~~~~~
/Users/clausklein/.local/include/fmt/base.h:325:36: error: 'underlying_type' in namespace 'std' does not name a template type
  325 | using underlying_t = typename std::underlying_type<T>::type;
      |                                    ^~~~~~~~~~~~~~~
/Users/clausklein/.local/include/fmt/base.h:326:53: error: 'decay' in namespace 'std' does not name a template type
  326 | template <typename T> using decay_t = typename std::decay<T>::type;
      |                                                     ^~~~~
/Users/clausklein/.local/include/fmt/base.h: In function 'constexpr bool fmt::v12::detail::is_constant_evaluated(bool)':
/Users/clausklein/.local/include/fmt/base.h:380:15: error: 'is_constant_evaluated' is not a member of 'std'
  380 |   return std::is_constant_evaluated();
      |               ^~~~~~~~~~~~~~~~~~~~~
/Users/clausklein/.local/include/fmt/base.h: At global scope:
/Users/clausklein/.local/include/fmt/base.h:421:46: error: 'make_unsigned_t' does not name a type
  421 | FMT_CONSTEXPR auto to_unsigned(Int value) -> make_unsigned_t<Int> {
      |                                              ^~~~~~~~~~~~~~~
/Users/clausklein/.local/include/fmt/base.h:421:61: error: expected initializer before '<' token
  421 | FMT_CONSTEXPR auto to_unsigned(Int value) -> make_unsigned_t<Int> {
      |                                                             ^
/Users/clausklein/.local/include/fmt/base.h:427:23: error: 'conditional_t' does not name a type
  427 | using unsigned_char = conditional_t<sizeof(Char) == 1, unsigned char, unsigned>;
      |                       ^~~~~~~~~~~~~
/Users/clausklein/.local/include/fmt/base.h:432:45: error: expected class-name before '{' token [-Wtemplate-body]
  432 | struct is_std_string_like : std::false_type {};
      |                                             ^
/Users/clausklein/.local/include/fmt/base.h:434:51: error: 'declval' is not a member of 'std'
  434 | struct is_std_string_like<T, void_t<decltype(std::declval<T>().find_first_of(
      |                                                   ^~~~~~~
/Users/clausklein/.local/include/fmt/base.h:1:1: note: 'std::declval' is defined in header '<utility>'; this is probably fixable by adding '#include <utility>'
  +++ |+#include <utility>
    1 | // Formatting library for C++ - the base API for char/UTF-8
/Users/clausklein/.local/include/fmt/base.h:434:51: error: 'declval' is not a member of 'std'
  434 | struct is_std_string_like<T, void_t<decltype(std::declval<T>().find_first_of(
      |                                                   ^~~~~~~
/Users/clausklein/.local/include/fmt/base.h:434:51: note: 'std::declval' is defined in header '<utility>'; this is probably fixable by adding '#include <utility>'
/Users/clausklein/.local/include/fmt/base.h:434:60: error: expected primary-expression before '>' token
  434 | struct is_std_string_like<T, void_t<decltype(std::declval<T>().find_first_of(
      |                                                            ^
/Users/clausklein/.local/include/fmt/base.h:434:62: error: expected primary-expression before ')' token
  434 | struct is_std_string_like<T, void_t<decltype(std::declval<T>().find_first_of(
      |                                                              ^
/Users/clausklein/.local/include/fmt/base.h:434:37: error: template argument 1 is invalid
. . .
ninja: build stopped: subcommand failed.
bash-5.3$ cmake -L .
-- The CXX compiler identification is GNU 16.1.0
-- Checking whether CXX compiler has -isysroot
-- Checking whether CXX compiler has -isysroot - no
-- Checking whether CXX compiler supports OSX deployment target flag
-- Checking whether CXX compiler supports OSX deployment target flag - no
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/local/bin/g++-16 - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Performing Test MAGIC_ENUM_HAS_CPP20_FLAG
-- Performing Test MAGIC_ENUM_HAS_CPP20_FLAG - Success
-- Performing Test MAGIC_ENUM_HAS_CPP23_FLAG
-- Performing Test MAGIC_ENUM_HAS_CPP23_FLAG - Success
-- Performing Test MAGIC_ENUM_HAS_CPP26_FLAG
-- Performing Test MAGIC_ENUM_HAS_CPP26_FLAG - Success
-- Configuring done (1.9s)
-- Generating done (0.1s)
-- Build files have been written to: /Users/clausklein/Workspace/cpp/magic_enum
-- Cache values
CMAKE_BUILD_TYPE:STRING=
CMAKE_CXX_COMPILER_LAUNCHER:STRING=ccache
CMAKE_INSTALL_PREFIX:PATH=/Users/clausklein/.local
CMAKE_OSX_ARCHITECTURES:STRING=
CMAKE_OSX_DEPLOYMENT_TARGET:STRING=
CMAKE_OSX_SYSROOT:STRING=
MAGIC_ENUM_MODULE_IMPORT_STD:BOOL=OFF
MAGIC_ENUM_MODULE_WITH_FMT:BOOL=OFF
MAGIC_ENUM_OPT_BUILD_EXAMPLES:BOOL=ON
MAGIC_ENUM_OPT_BUILD_TESTS:BOOL=ON
MAGIC_ENUM_OPT_INSTALL:BOOL=ON
MAGIC_ENUM_OPT_INSTALL_PACKAGE_XML:BOOL=ON
MAGIC_ENUM_OPT_TEST_INSTALLED_VERSION:BOOL=OFF
MAGIC_ENUM_OPT_TEST_INSTALLED_VERSION_PKGCONFIG:BOOL=OFF
MAGIC_ENUM_OPT_VERIFY_INTERFACE_HEADER_SETS:BOOL=ON
MAGIC_ENUM_USE_MODULES:BOOL=OFF
bash-5.3$

Neargye · 2026-08-07T18:35:07Z

@ClausKlein If I understood correctly, it’s better to remove support for the fmt module for now, until it becomes stable in their library?

ClausKlein · 2026-08-07T20:58:07Z

@ClausKlein If I understood correctly, it’s better to remove support for the fmt module for now, until it becomes stable in their library?

Yes.

And note: the Beman project decided to build CXX_MODULES only together with import std; => needs toolchain support and at least C++23.

Neargye added 2 commits July 11, 2026 19:08

add new magic_enum::magic_enum_module target

09de782

wip

ed9aabb

Neargye force-pushed the module_target branch from b573a2d to ed9aabb Compare August 3, 2026 10:35

Neargye added 3 commits August 3, 2026 15:34

Merge remote-tracking branch 'origin/master' into module_target

d8cf80b

wip

e8c7f43

wip

7a2244e

Neargye mentioned this pull request Aug 3, 2026

g++-16 fails to build magic_enum with import std; on macos #461

Open

Neargye added 2 commits August 3, 2026 18:56

wip

c28e8a0

Merge remote-tracking branch 'origin/master' into module_target

8d84638