Caio/modules

CMakeLists.txt

@@ -22,7 +22,7 @@ project(
 if(NOT CMAKE_BUILD_TYPE)
     set(CMAKE_BUILD_TYPE Debug)
 endif()
-    
+
 message(VERBOSE "*")
 message(VERBOSE "* ${PROJECT_NAME} v${PROJECT_VERSION} (${CMAKE_BUILD_TYPE})")
 message(VERBOSE "* Copyright (c) 2017-2026 Michele Caini <michele.caini@gmail.com>")
@@ -37,6 +37,13 @@ list(INSERT CMAKE_MODULE_PATH 0 ${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules)
 option(ENTT_USE_LIBCPP "Use libc++ by adding -stdlib=libc++ flag if available." OFF)
 option(ENTT_USE_SANITIZER "Enable sanitizers by adding -fsanitize=address -fno-omit-frame-pointer -fsanitize=undefined flags if available." OFF)
 option(ENTT_USE_CLANG_TIDY "Enable static analysis with clang-tidy" OFF)
+option(ENTT_MODULE "Build EnTT module instead of a regular header-only library." OFF)
+
+set(ENTT_USER_CONFIG "" CACHE FILEPATH "Path to a file containing user EnTT configuration.")
+
+if (NOT ENTT_MODULE AND ENTT_USER_CONFIG)
+    message(FATAL_ERROR "The option ENTT_USER_CONFIG can be used only when ENTT_MODULE is ON")
+endif()
 
 if(ENTT_USE_LIBCPP)
     if(NOT WIN32)
@@ -83,25 +90,54 @@ endif()
 
 include(GNUInstallDirs)
 
-add_library(EnTT INTERFACE)
+if (ENTT_MODULE)
+    if (CMAKE_VERSION VERSION_LESS 3.28)
+        message(FATAL_ERROR "CMake >= 3.28 is required to build EnTT as a module")
+    endif()
+
+    set(ENTT_LIBRARY_TYPE STATIC)
+    set(ENTT_SCOPE PUBLIC)
+else()
+    set(ENTT_LIBRARY_TYPE INTERFACE)
+    set(ENTT_SCOPE INTERFACE)
+endif()
+
+add_library(EnTT ${ENTT_LIBRARY_TYPE})
 add_library(EnTT::EnTT ALIAS EnTT)
 
 target_include_directories(
     EnTT
-    INTERFACE
+    ${ENTT_SCOPE}
         $<BUILD_INTERFACE:${EnTT_SOURCE_DIR}/src>
         $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
 )
 
 target_compile_features(EnTT INTERFACE cxx_std_20)
 
 if(ENTT_HAS_LIBCPP)
-    target_compile_options(EnTT BEFORE INTERFACE -stdlib=libc++)
+    target_compile_options(EnTT BEFORE ${ENTT_SCOPE} -stdlib=libc++)
+    if(ENTT_MODULE)
+        target_link_options(EnTT ${ENTT_SCOPE} -stdlib=libc++)
+    endif()
 endif()
 
 if(ENTT_HAS_SANITIZER)
-    target_compile_options(EnTT INTERFACE $<$<CONFIG:Debug>:-fsanitize=address -fno-omit-frame-pointer -fsanitize=undefined>)
-    target_link_libraries(EnTT INTERFACE $<$<CONFIG:Debug>:-fsanitize=address -fno-omit-frame-pointer -fsanitize=undefined>)
+    target_compile_options(EnTT ${ENTT_SCOPE} $<$<CONFIG:Debug>:-fsanitize=address -fno-omit-frame-pointer -fsanitize=undefined>)
+    target_link_options(EnTT ${ENTT_SCOPE} $<$<CONFIG:Debug>:-fsanitize=address -fno-omit-frame-pointer -fsanitize=undefined>)
+endif()
+
+if (ENTT_USER_CONFIG)
+    target_compile_definitions(EnTT ${ENTT_SCOPE} ENTT_USER_CONFIG=\"${ENTT_USER_CONFIG}\")
+endif()
+
+if (ENTT_MODULE)
+    target_sources(EnTT
+        PUBLIC
+            FILE_SET cxx_modules TYPE CXX_MODULES
+            BASE_DIRS ${EnTT_SOURCE_DIR}/src/entt
+            FILES
+                ${EnTT_SOURCE_DIR}/src/entt/entt.ixx
+    )
 endif()
 
 if(ENTT_CLANG_TIDY_EXECUTABLE)
@@ -295,11 +331,22 @@ if(ENTT_INSTALL)
 
     include(CMakePackageConfigHelpers)
 
-    install(
-        TARGETS EnTT
-        EXPORT EnTTTargets
-        ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
-    )
+    if(ENTT_MODULE)
+        install(
+            TARGETS EnTT
+            EXPORT EnTTTargets
+            ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
+            INCLUDES DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+            FILE_SET cxx_modules DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/entt
+        )
+    else()
+        install(
+            TARGETS EnTT
+            EXPORT EnTTTargets
+            ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
+            INCLUDES DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+        )
+    endif()
 
     write_basic_package_version_file(
         EnTTConfigVersion.cmake
@@ -313,18 +360,37 @@ if(ENTT_INSTALL)
         INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/EnTT/cmake
     )
 
-    export(
-        EXPORT EnTTTargets
-        FILE ${CMAKE_CURRENT_BINARY_DIR}/EnTTTargets.cmake
-        NAMESPACE EnTT::
-    )
+    if(ENTT_MODULE)
+        export(
+            TARGETS EnTT
+            FILE "${CMAKE_CURRENT_BINARY_DIR}/EnTTTargets.cmake"
+            NAMESPACE EnTT::
+            CXX_MODULES_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/cxx-modules"
+        )
+    else()
+        export(
+            TARGETS EnTT
+            FILE "${CMAKE_CURRENT_BINARY_DIR}/EnTTTargets.cmake"
+            NAMESPACE EnTT::
+        )
+    endif()
 
-    install(
-        EXPORT EnTTTargets
-        FILE EnTTTargets.cmake
-        DESTINATION ${CMAKE_INSTALL_LIBDIR}/EnTT/cmake
-        NAMESPACE EnTT::
-    )
+    if(ENTT_MODULE)
+        install(
+            EXPORT EnTTTargets
+            FILE EnTTTargets.cmake
+            DESTINATION ${CMAKE_INSTALL_LIBDIR}/EnTT/cmake
+            NAMESPACE EnTT::
+            CXX_MODULES_DIRECTORY ${CMAKE_INSTALL_LIBDIR}/EnTT/cmake/cxx-modules
+        )
+    else()
+        install(
+            EXPORT EnTTTargets
+            FILE EnTTTargets.cmake
+            DESTINATION ${CMAKE_INSTALL_LIBDIR}/EnTT/cmake
+            NAMESPACE EnTT::
+        )
+    endif()
 
     install(
         FILES
@@ -357,12 +423,12 @@ if(ENTT_BUILD_TESTING OR ENTT_BUILD_TESTBED)
     # Tests and tesetbed do not work together because SDL gets confused with EnTT tests
     if(ENTT_BUILD_TESTING)
         option(ENTT_FIND_GTEST_PACKAGE "Enable finding gtest package." OFF)
-    
+
         option(ENTT_BUILD_BENCHMARK "Build benchmark." OFF)
         option(ENTT_BUILD_EXAMPLE "Build examples." OFF)
         option(ENTT_BUILD_LIB "Build lib tests." OFF)
         option(ENTT_BUILD_SNAPSHOT "Build snapshot test with Cereal." OFF)
-    
+
         include(CTest)
         enable_testing()
         add_subdirectory(test)

README.md

@@ -111,6 +111,8 @@ mind.
 
 ```cpp
 #include <entt/entt.hpp>
+// or import entt; 
+// See Integration > CMake for details.
 
 struct position {
     float x;
@@ -246,6 +248,9 @@ using `EnTT` as a submodule without conflicting with user logic.<br/>
 It is therefore necessary to set the option to true to take advantage of the
 installation logic provided by this library.
 
+Note that `EnTT` can be consumed also as a C++ module. To enable module support, 
+the `ENTT_MODULE` option has to be set to `ON` in `CMake`.
+
 ## Natvis support
 
 When using `CMake`, just enable the option `ENTT_INCLUDE_NATVIS` and enjoy

docs/md/config.md

@@ -142,3 +142,35 @@ paths appropriately.<br/>
 For example, `CMake` allows users to _bind_ additional include directories to a
 target with `target_include_directories`. See the test suite, and in particular
 the `config_ext` test for a practical example.
+
+## When consumed as a module
+
+When `EnTT` is consumed as a C++20 module, all the above definitions can be
+put into a custom configuration file that can be referred to through the
+`ENTT_USER_CONFIG` compile definition using its path. <br/>
+
+In case the module is built through CMake, the variable
+`ENTT_USER_CONFIG` can be set directly from the `CMakeLists.txt` file before
+including the library through `add_subdirectory`.<br/>
+
+Example of a custom configuration file and CMake setup:
+```c++
+// user_config.h
+
+#define ENTT_ID_TYPE std::uint64_t
+#define ENTT_USE_ATOMIC
+```
+```c++
+// CMakeLists.txt
+
+set(ENTT_MODULE ON)
+set(ENTT_USER_CONFIG "path/to/user_config.h")
+
+...
+
+add_subdirectory(path/to/entt)
+
+...
+
+target_link_libraries(your_target PUBLIC EnTT::EnTT)
+```

src/entt/config/module.h

@@ -0,0 +1,16 @@
+#ifndef ENTT_MODULE_H
+#define ENTT_MODULE_H
+
+#ifndef ENTT_MODULE_EXPORT
+#    define ENTT_MODULE_EXPORT
+#endif // ENTT_MODULE_EXPORT
+
+#ifndef ENTT_MODULE_EXPORT_BEGIN
+#    define ENTT_MODULE_EXPORT_BEGIN
+#endif // ENTT_MODULE_EXPORT_BEGIN
+
+#ifndef ENTT_MODULE_EXPORT_END
+#    define ENTT_MODULE_EXPORT_END
+#endif // ENTT_MODULE_EXPORT_END
+
+#endif // ENTT_MODULE_H