Make import std; usable

.github/workflows/ci.yml

@@ -243,8 +243,8 @@ jobs:
     needs: posix
     runs-on: ubuntu-latest
     steps:
-    - name: Coveralls Finished
-      uses: coverallsapp/github-action@master
-      with:
-        github-token: ${{ secrets.github_token }}
-        parallel-finished: true
+      - name: Coveralls Finished
+        uses: coverallsapp/github-action@master
+        with:
+          github-token: ${{ secrets.github_token }}
+          parallel-finished: true

.gitignore

@@ -0,0 +1,2 @@
+build/
+compile_commands.json

CMakeLists.txt

@@ -1,46 +1,120 @@
+# -----------------------------------------------------------------------------
+# Boost.Any CMake
+# Handles: no modules, modules, modules + import std;
+# -----------------------------------------------------------------------------
 # Copyright 2019 Mike Dev
 # Distributed under the Boost Software License, Version 1.0.
-# See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt
+# -----------------------------------------------------------------------------
 
-cmake_minimum_required( VERSION 3.8...3.31 )
-project( boost_any VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX )
+cmake_minimum_required(VERSION 3.21...4.2)
+
+project(boost_any VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX)
+
+if(PROJECT_IS_TOP_LEVEL)
+    find_package(Boost 1.90.0 CONFIG)
+endif()
+
+# -----------------------------------------------------------------------------
+# User option: enable C++ modules
+# -----------------------------------------------------------------------------
+option(BOOST_USE_MODULES "Build Boost using C++ modules" OFF)
+
+# -----------------------------------------------------------------------------
+# Determine target type and sources
+# -----------------------------------------------------------------------------
+if(BOOST_USE_MODULES)
+
+    # Ensure CMAKE_CXX_STANDARD is set for module detection
+    if(NOT DEFINED CMAKE_CXX_STANDARD)
+        set(CMAKE_CXX_STANDARD 20)
+    endif()
 
-if (BOOST_USE_MODULES)
     add_library(boost_any)
-    target_sources(boost_any PUBLIC
-        FILE_SET modules_public
-            TYPE CXX_MODULES
-            FILES modules/boost_any.cppm
+
+    target_sources(
+        boost_any
+        PUBLIC
+            FILE_SET modules_public
+                TYPE CXX_MODULES
+                FILES modules/boost_any.cppm
     )
 
-    target_compile_features(boost_any PUBLIC cxx_std_20)
+    # Require C++20 for modules
+    target_compile_features(boost_any PUBLIC cxx_std_${CMAKE_CXX_STANDARD})
+
+    # Define macro indicating modules usage
     target_compile_definitions(boost_any PUBLIC BOOST_USE_MODULES)
-    set(__boost_cxx_standard ${CMAKE_CXX_STANDARD})
-    if (NOT __boost_cxx_standard)
-        set(__boost_cxx_standard 20)
-    endif()
-    if (CMAKE_CXX_COMPILER_IMPORT_STD AND ${__boost_cxx_standard} IN_LIST CMAKE_CXX_COMPILER_IMPORT_STD)
-        target_compile_definitions(boost_any PRIVATE BOOST_ANY_USE_STD_MODULE)
-        message(STATUS "Using `import std;`")
+
+    # Check if import std; is available for the current standard
+    if(${CMAKE_CXX_STANDARD} IN_LIST CMAKE_CXX_COMPILER_IMPORT_STD)
+        target_compile_definitions(boost_any PUBLIC BOOST_ANY_USE_STD_MODULE)
+        set_property(TARGET boost_any CXX_MODULE_STD ON)
+        message(STATUS "Boost.Any: Using `import std;`")
     else()
-        message(STATUS "`import std;` is not available")
+        message(WARNING "Boost.Any: `import std;` is not available for C++${CMAKE_CXX_STANDARD}")
     endif()
+
     set(__scope PUBLIC)
+
 else()
+
+    # Modules disabled -> INTERFACE library
     add_library(boost_any INTERFACE)
+
+    # If modules are disabled, require C++17 for headers
+    target_compile_features(boost_any INTERFACE cxx_std_17)
+
+    # Verify interface headers only at top level
+    if(PROJECT_IS_TOP_LEVEL)
+        set(CMAKE_VERIFY_INTERFACE_HEADER_SETS ON)
+    endif()
+
     set(__scope INTERFACE)
+
 endif()
 
-target_include_directories(boost_any ${__scope} include)
-target_link_libraries( boost_any
-    ${__scope}
+# -----------------------------------------------------------------------------
+# Include headers
+# -----------------------------------------------------------------------------
+if(BOOST_USE_MODULES)
+    target_sources(
+        boost_any
+        PUBLIC
+            FILE_SET headers_public
+                TYPE HEADERS
+                BASE_DIRS include
+                FILES
+                    include/boost/any/bad_any_cast.hpp
+                    include/boost/any/basic_any.hpp
+                    include/boost/any/fwd.hpp
+                    include/boost/any/unique_any.hpp
+                    include/boost/any/detail/config.hpp
+                    include/boost/any/detail/placeholder.hpp
+    )
+else()
+    target_include_directories(boost_any ${__scope} include)
+endif()
+
+# -----------------------------------------------------------------------------
+# Link dependencies
+# -----------------------------------------------------------------------------
+if(PROJECT_IS_TOP_LEVEL)
+    target_link_libraries(boost_any ${__scope} Boost::headers)
+else()
+    target_link_libraries(boost_any
+       ${__scope}
         Boost::config
         Boost::throw_exception
         Boost::type_index
-)
+    )
+endif()
 
-add_library( Boost::any ALIAS boost_any )
+# Alias for convenient import
+add_library(Boost::any ALIAS boost_any)
 
+# -----------------------------------------------------------------------------
+# Testing
+# -----------------------------------------------------------------------------
 if(BUILD_TESTING)
     add_subdirectory(test)
 endif()

include/boost/any/fwd.hpp

@@ -17,6 +17,9 @@
 #ifdef BOOST_HAS_PRAGMA_ONCE
 # pragma once
 #endif
+
+#include <type_traits>
+
 #endif  // #ifndef BOOST_ANY_INTERFACE_UNIT
 
 /// \file boost/any/fwd.hpp

modules/boost_any.cppm

@@ -11,12 +11,14 @@ module;
 #include <boost/assert.hpp>
 #include <boost/config.hpp>
 #include <boost/throw_exception.hpp>
-#include <boost/type_index.hpp>
+
+#include <memory> // for std::addressof
+
+import boost.type_index;
 
 #ifdef BOOST_ANY_USE_STD_MODULE
 import std;
 #else
-#include <memory>
 #include <stdexcept>
 #include <typeinfo>
 #include <type_traits>

modules/usage_sample.cpp

@@ -7,10 +7,50 @@
 // clang++ -std=c++20 -fmodule-file=type_index.pcm type_index.pcm usage_sample.cpp
 
 //[any_module_example
+
+#ifdef BOOST_ANY_USE_STD_MODULE
+import std;
+#else
+# include <iostream>
+# include <sstream>
+# include <string>
+#endif
+
 import boost.any;
 
-int main() {
-    boost::any a = 42;
+namespace {
+
+    template <typename... Ts> auto any_to_string(const boost::any& a) -> std::string {
+        std::ostringstream oss;
+
+        auto try_cast = [&](auto* dummy) -> bool {
+            using T = std::decay_t<decltype(*dummy)>;
+            if (a.type() == typeid(T)) {
+                oss << boost::any_cast<T>(a);
+                return true;
+            }
+            return false;
+        };
+
+        // Expand over Ts...
+        bool const success = (try_cast((Ts*)nullptr) || ...);
+
+        if (!success) {
+            oss << "<unknown type: " << a.type().name() << ">";
+        }
+        return oss.str();
+    }
+
+}  // namespace
+
+// Usage:
+auto main() -> int {
+    boost::any const a = 42;
+#ifdef BOOST_ANY_USE_STD_MODULE
+    std::println("{}", any_to_string<int, double, std::string>(a));
+#else
+    std::cout << any_to_string<int, double, std::string>(a) << '\n';
+#endif
 }
 //]
 

test/cmake_subdir_test/CMakeLists.txt

@@ -2,9 +2,9 @@
 # Distributed under the Boost Software License, Version 1.0.
 # See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt
 
-cmake_minimum_required(VERSION 3.5...4.0)
+cmake_minimum_required(VERSION 3.21...4.2)
 
-project(any_subdir_test LANGUAGES CXX)
+project(boost_any LANGUAGES CXX VERSION 1.90.0)
 
 add_subdirectory(../../../assert boostorg/assert)
 add_subdirectory(../../../core boostorg/core)
@@ -19,35 +19,49 @@ add_subdirectory(../../../throw_exception boostorg/throw_exception)
 add_subdirectory(../../../type_index boostorg/type_index)
 add_subdirectory(../../../type_traits boostorg/type_traits)
 
+# ../../CMakeLists.txt
 add_subdirectory(../../ boostorg/any)
 
+include(cmake/boost-install-library.cmake)
+boost_install_library(boost_config TARGETS boost_config)
+boost_install_library(boost_assert TARGETS boost_assert)
+boost_install_library(boost_mp11 TARGETS boost_mp11 DEPENDENCIES Boost::core)
+boost_install_library(boost_describe TARGETS boost_describe DEPENDENCIES Boost::mp11)
+boost_install_library(boost_container_hash TARGETS boost_container_hash DEPENDENCIES Boost::describe)
+boost_install_library(boost_throw_exception TARGETS boost_throw_exception DEPENDENCIES Boost::assert)
+boost_install_library(boost_type_index TARGETS boost_type_index DEPENDENCIES Boost::boost_container_hash)
+boost_install_library(boost_any TARGETS boost_any DEPENDENCIES Boost::type_index Boost::config Boost::throw_exception)
+
 enable_testing()
 
-if (BOOST_USE_MODULES)
+if(BOOST_USE_MODULES)
     add_executable(boost_any_module_usage ../../modules/usage_sample.cpp)
     target_link_libraries(boost_any_module_usage PRIVATE Boost::any)
     add_test(NAME boost_any_module_usage COMMAND boost_any_module_usage)
+else()
+    set(RUN_TESTS_SOURCES
+        any_test_mplif.cpp
+        any_test_rv.cpp
+        basic_any_test.cpp
+        basic_any_test_large_object.cpp
+        basic_any_test_mplif.cpp
+        basic_any_test_rv.cpp
+        basic_any_test_small_object.cpp
+        unique_any/base.cpp
+        unique_any/emplace.cpp
+        unique_any/from_any.cpp
+        unique_any/move.cpp
+        # any_test.cpp  # Ambiguous with modules, because all the anys now available
+    )
 endif()
 
-list(APPEND RUN_TESTS_SOURCES
-    any_test_mplif.cpp
-    basic_any_test_small_object.cpp
-    any_test_rv.cpp
-    basic_any_test.cpp
-
-    unique_any/from_any.cpp
-    unique_any/move.cpp
-    unique_any/emplace.cpp
-    unique_any/base.cpp
-
-    basic_any_test_mplif.cpp
-    basic_any_test_rv.cpp
-    basic_any_test_large_object.cpp
-    # any_test.cpp  # Ambiguous with modules, because all the anys now available
-)
-
-foreach (testsourcefile ${RUN_TESTS_SOURCES})
-    get_filename_component(testname ${testsourcefile} NAME_WLE)
+foreach(testsourcefile ${RUN_TESTS_SOURCES})
+    if(NOT EXISTS ../${testsourcefile})
+        message(WARNING "Missing ../${testsourcefile}")
+        continue()
+    endif()
+
+    get_filename_component(testname ../${testsourcefile} NAME_WLE)
     add_executable(${PROJECT_NAME}_${testname} ../${testsourcefile})
     target_link_libraries(${PROJECT_NAME}_${testname} Boost::any Boost::core)
     add_test(NAME ${PROJECT_NAME}_${testname} COMMAND ${PROJECT_NAME}_${testname})