boostorg · apolukhin · May 24, 2026 · Apr 13, 2026 · Apr 13, 2026 · Apr 18, 2026
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -105,6 +105,23 @@ jobs:
           ./b2 -d0 headers
           ./b2 -j4 variant=debug tools/inspect
 
+      - name: Run modules tests without 'import std;'
+        if: ${{matrix.toolset == 'clang-19'}}
+        run: |
+          cd ../boost-root/libs/$LIBRARY
+          cmake -S test/cmake_subdir_test -B __build \
+            -GNinja \
+            -DBUILD_TESTING=1 \
+            -DBOOST_DLL_USE_STD_FS=1 \
+            -DBOOST_USE_MODULES=1 \
+            -DCMAKE_CXX_COMPILER=${{matrix.compiler}} \
+            -DCMAKE_CXX_FLAGS="-stdlib=libc++"  \
+            -DCMAKE_CXX_STANDARD=20
+
+          cmake --build __build
+          ctest --test-dir __build --output-on-failure --no-tests=error -VV
+          rm -rf __build
+
       - name: Run CMake subdir tests
         if: ${{matrix.toolset == 'gcc-14' || matrix.toolset == 'clang-19'}}
         run: |

diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -1,10 +1,11 @@
 # Copyright 2020 Peter Dimov
 # Copyright Antony Polukhin, 2021-2026
+# Copyright Fedor Osetrov, 2025-2026
 #
 # Distributed under the Boost Software License, Version 1.0.
 # https://www.boost.org/LICENSE_1_0.txt
 
-cmake_minimum_required(VERSION 3.5...3.16)
+cmake_minimum_required(VERSION 3.5...4.20)
 
 project(boost_dll VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX)
 
@@ -48,16 +49,32 @@ target_link_libraries(boost_dll_boost_fs
     Boost::filesystem
 )
 
-# Detault library
+# Default library
+
+if (BOOST_USE_MODULES)
+  add_library(boost_dll)
+  target_compile_definitions(boost_dll PUBLIC BOOST_USE_MODULES)
+  target_compile_features(boost_dll PUBLIC cxx_std_20)
+  target_sources(boost_dll
+    PUBLIC
+      FILE_SET CXX_MODULES
+      BASE_DIRS ${CMAKE_CURRENT_SOURCE_DIR}/modules
+      FILES ${CMAKE_CURRENT_SOURCE_DIR}/modules/boost_dll.cppm
+  )
+  set(__scope PUBLIC)
+else()
+  add_library(boost_dll INTERFACE)
+  set(__scope INTERFACE)
+endif()
 
-add_library(boost_dll INTERFACE)
 add_library(Boost::dll ALIAS boost_dll)
-target_include_directories(boost_dll INTERFACE include)
+target_include_directories(boost_dll ${__scope} include)
 if (BOOST_DLL_USE_STD_FS)
-  target_link_libraries(boost_dll INTERFACE Boost::dll_std_fs)
+  target_link_libraries(boost_dll ${__scope} Boost::dll_std_fs)
 else()
-  target_link_libraries(boost_dll INTERFACE Boost::dll_boost_fs)
+  target_link_libraries(boost_dll ${__scope} Boost::dll_boost_fs)
 endif()
+unset(__scope)
 
 if (BOOST_SUPERPROJECT_VERSION AND NOT CMAKE_VERSION VERSION_LESS 3.13)
   boost_install(

diff --git a/example/b2_workarounds.hpp b/example/b2_workarounds.hpp
@@ -8,12 +8,13 @@
 #ifndef BOOST_DLL_EXAMPLE_COMMON_B2_WORKAROUNDS_HPP
 #define BOOST_DLL_EXAMPLE_COMMON_B2_WORKAROUNDS_HPP
 
-#include <boost/dll/config.hpp>
 #include <boost/filesystem.hpp>
 #include <boost/system/error_code.hpp>
 #include <iostream>
 #include <cctype>
 
+#include <boost/dll/config.hpp>
+
 namespace b2_workarounds {
 
 

diff --git a/example/getting_started_library.cpp b/example/getting_started_library.cpp
@@ -8,8 +8,8 @@
 // MinGW related workaround
 #define BOOST_DLL_FORCE_ALIAS_INSTANTIATION
 
-#include <boost/dll.hpp>
 #include <string>
+#include <boost/dll.hpp>
 
 #define API extern "C" BOOST_SYMBOL_EXPORT
 

diff --git a/example/tutorial4/load_self.cpp b/example/tutorial4/load_self.cpp
@@ -9,11 +9,11 @@
 #define BOOST_DLL_FORCE_ALIAS_INSTANTIATION
 
 //[plugcpp_my_plugin_load_self
-#include <boost/dll/shared_library.hpp>         // for shared_library
-#include <boost/dll/runtime_symbol_info.hpp>    // for program_location()
 #include "static_plugin.hpp"                    // without this headers some compilers may optimize out the `create_plugin` symbol
 #include <iostream>
 #include <memory>
+#include <boost/dll/shared_library.hpp>         // for shared_library
+#include <boost/dll/runtime_symbol_info.hpp>    // for program_location()
 
 namespace dll = boost::dll;
 

diff --git a/example/tutorial4/static_plugin.hpp b/example/tutorial4/static_plugin.hpp
@@ -6,9 +6,9 @@
 // or copy at http://www.boost.org/LICENSE_1_0.txt)
 
 //[plugcpp_my_plugin_static
-#include <boost/dll/alias.hpp>                          // for BOOST_DLL_ALIAS
 #include <memory>
 #include "../tutorial_common/my_plugin_api.hpp"
+#include <boost/dll/alias.hpp>                          // for BOOST_DLL_ALIAS
 
 namespace my_namespace {
     std::shared_ptr<my_plugin_api> create_plugin();   // Forward declaration

diff --git a/example/tutorial6/on_unload_lib.cpp b/example/tutorial6/on_unload_lib.cpp
@@ -9,9 +9,9 @@
 #define BOOST_DLL_FORCE_ALIAS_INSTANTIATION
 
 //[plugcpp_on_unload
-#include <boost/dll/alias.hpp> // for BOOST_DLL_ALIAS
 #include <functional>
 #include <vector>
+#include <boost/dll/alias.hpp> // for BOOST_DLL_ALIAS
 
 namespace my_namespace {
 

diff --git a/example/tutorial7/library1.cpp b/example/tutorial7/library1.cpp
@@ -9,9 +9,9 @@
 #define BOOST_DLL_FORCE_ALIAS_INSTANTIATION
 
 //[plugcpp_tutorial7_library1
-#include <boost/dll/alias.hpp> // for BOOST_DLL_ALIAS_SECTIONED
 #include <iostream>
 #include <string>
+#include <boost/dll/alias.hpp> // for BOOST_DLL_ALIAS_SECTIONED
 
 void print(const std::string& s) {
     std::cout << "Hello, " << s << '!' << std::endl;

diff --git a/example/tutorial7/library2.cpp b/example/tutorial7/library2.cpp
@@ -9,9 +9,9 @@
 #define BOOST_DLL_FORCE_ALIAS_INSTANTIATION
 
 //[plugcpp_tutorial7_library2
-#include <boost/dll/alias.hpp> // for BOOST_DLL_ALIAS_SECTIONED
 #include <string>
 #include <iostream>
+#include <boost/dll/alias.hpp> // for BOOST_DLL_ALIAS_SECTIONED
 
 void print_howdy(const std::string& s) {
     std::cout << "How're you doing, " << s << '?' << std::endl;

diff --git a/example/tutorial8/refcounting_api.hpp b/example/tutorial8/refcounting_api.hpp
@@ -7,6 +7,7 @@
 
 //[plugcpp_my_plugin_refcounting_api
 #include "../tutorial_common/my_plugin_api.hpp"
+#include <memory>
 #include <boost/dll/config.hpp>
 
 class my_refcounting_api: public my_plugin_api {
@@ -19,7 +20,6 @@ class my_refcounting_api: public my_plugin_api {
 
 
 //[plugcpp_library_holding_deleter_api_bind
-#include <memory>
 #include <boost/dll/shared_library.hpp>
 
 struct library_holding_deleter {

diff --git a/example/tutorial8/tutorial8_static.cpp b/example/tutorial8/tutorial8_static.cpp
@@ -6,9 +6,9 @@
 // or copy at http://www.boost.org/LICENSE_1_0.txt)
 
 //[callplugcpp_tutorial8_static
-#include <boost/dll/runtime_symbol_info.hpp> // program_location()
 #include <iostream>
 #include "refcounting_plugin.hpp"
+#include <boost/dll/runtime_symbol_info.hpp> // program_location()
 
 int main() {
     std::shared_ptr<my_refcounting_api> plugin = get_plugin(

diff --git a/include/boost/dll.hpp b/include/boost/dll.hpp
@@ -12,16 +12,23 @@
 /// \file boost/dll.hpp
 /// \brief Includes all the non-experimental headers of the Boost.DLL library.
 
+#include <boost/dll/detail/config.hpp>
+
+#if !defined(BOOST_USE_MODULES) || defined(BOOST_DLL_INTERFACE_UNIT)
+
+#ifdef BOOST_HAS_PRAGMA_ONCE
+# pragma once
+#endif
+
 #include <boost/dll/config.hpp>
 #include <boost/dll/shared_library.hpp>
-#include <boost/dll/alias.hpp>
 #include <boost/dll/import.hpp>
 #include <boost/dll/library_info.hpp>
 #include <boost/dll/runtime_symbol_info.hpp>
 
-#ifdef BOOST_HAS_PRAGMA_ONCE
-# pragma once
-#endif
+#endif // !defined(BOOST_USE_MODULES) || defined(BOOST_DLL_INTERFACE_UNIT)
+
+#include <boost/dll/alias.hpp>
 
 #endif // BOOST_DLL_DLL_HPP
 
diff --git a/include/boost/dll/alias.hpp b/include/boost/dll/alias.hpp
@@ -5,26 +5,36 @@
 // (See accompanying file LICENSE_1_0.txt
 // or copy at http://www.boost.org/LICENSE_1_0.txt)
 
+/// \file boost/dll/alias.hpp
+/// \brief Includes alias methods and macro. You can include this header or
+/// boost/dll/shared_library.hpp to reduce dependencies
+/// in case you do not use the refcountable functions.
+
 #ifndef BOOST_DLL_ALIAS_HPP
 #define BOOST_DLL_ALIAS_HPP
 
+#include <boost/dll/detail/config.hpp>
+
+#if !defined(BOOST_USE_MODULES) || defined(BOOST_DLL_INTERFACE_UNIT)
+
 #include <boost/dll/config.hpp>
+
+#ifdef BOOST_HAS_PRAGMA_ONCE
+# pragma once
+#endif
+
+#if !defined(BOOST_DLL_INTERFACE_UNIT)
 #include <boost/predef/compiler.h>
 #include <boost/predef/os.h>
-#include <boost/dll/detail/aggressive_ptr_cast.hpp>
 
 #if BOOST_COMP_GNUC // MSVC does not have <stdint.h> and defines it in some other header, MinGW requires that header.
 #include <stdint.h> // intptr_t
 #endif
+#endif // !defined(BOOST_DLL_INTERFACE_UNIT)
 
-#ifdef BOOST_HAS_PRAGMA_ONCE
-# pragma once
-#endif
+#include <boost/dll/detail/aggressive_ptr_cast.hpp>
 
-/// \file boost/dll/alias.hpp
-/// \brief Includes alias methods and macro. You can include this header or
-/// boost/dll/shared_library.hpp to reduce dependencies
-/// in case you do not use the refcountable functions.
+#endif // !defined(BOOST_USE_MODULES) || defined(BOOST_DLL_INTERFACE_UNIT)
 
 namespace boost { namespace dll {
 
@@ -284,6 +294,5 @@ namespace boost { namespace dll {
 
 }} // namespace boost::dll
 
-
 #endif // BOOST_DLL_ALIAS_HPP
 
diff --git a/include/boost/dll/config.hpp b/include/boost/dll/config.hpp
@@ -7,10 +7,11 @@
 /// \file boost/dll/config.hpp
 /// \brief Imports filesystem, error_code, errc, system_error, make_error_code from Boost or C++17 into `boost::dll::fs` namespace.
 
-#ifndef BOOST_DLL_DETAIL_CONFIG_HPP
-#define BOOST_DLL_DETAIL_CONFIG_HPP
+#ifndef BOOST_DLL_CONFIG_HPP
+#define BOOST_DLL_CONFIG_HPP
+
+#include <boost/dll/detail/config.hpp>
 
-#include <boost/config.hpp>
 #ifdef BOOST_HAS_PRAGMA_ONCE
 #   pragma once
 #endif
@@ -44,9 +45,11 @@ using system_error = std::conditional_t<BOOST_DLL_USE_STD_FS, std::system_error,
 
 
 #ifdef BOOST_DLL_USE_STD_FS
-#include <filesystem>
 
+#if !defined(BOOST_DLL_INTERFACE_UNIT)
+#include <filesystem>
 #include <system_error>
+#endif // !defined(BOOST_DLL_INTERFACE_UNIT)
 
 namespace boost { namespace dll { namespace fs {
 
@@ -58,10 +61,12 @@ using std::system_error;
 
 #else // BOOST_DLL_USE_STD_FS
 
+#if !defined(BOOST_DLL_INTERFACE_UNIT)
 #include <boost/filesystem/path.hpp>
 #include <boost/filesystem/operations.hpp>
 #include <boost/system/system_error.hpp>
 #include <boost/system/error_code.hpp>
+#endif // !defined(BOOST_DLL_INTERFACE_UNIT)
 
 namespace boost { namespace dll { namespace fs {
 
@@ -76,7 +81,9 @@ using boost::system::system_error;
 
 #ifdef BOOST_DLL_USE_BOOST_SHARED_PTR
 
+#if !defined(BOOST_DLL_INTERFACE_UNIT)
 #include <boost/make_shared.hpp>
+#endif // !defined(BOOST_DLL_INTERFACE_UNIT)
 
 namespace boost { namespace dll { namespace detail {
     template <class T>
@@ -86,7 +93,9 @@ namespace boost { namespace dll { namespace detail {
 
 #else  // BOOST_DLL_USE_STD_FS
 
+#if !defined(BOOST_DLL_INTERFACE_UNIT)
 #include <memory>
+#endif // !defined(BOOST_DLL_INTERFACE_UNIT)
 
 namespace boost { namespace dll { namespace detail {
     template <class T>
@@ -96,5 +105,5 @@ namespace boost { namespace dll { namespace detail {
 
 #endif  // BOOST_DLL_USE_STD_FS
 
-#endif // BOOST_DLL_DETAIL_PUSH_OPTIONS_HPP
+#endif // BOOST_DLL_CONFIG_HPP
 
diff --git a/include/boost/dll/detail/aggressive_ptr_cast.hpp b/include/boost/dll/detail/aggressive_ptr_cast.hpp
@@ -13,9 +13,11 @@
 #   pragma once
 #endif
 
+#if !defined(BOOST_DLL_INTERFACE_UNIT)
 #include <cstring>              // std::memcpy
 #include <memory>
 #include <type_traits>
+#endif // !defined(BOOST_DLL_INTERFACE_UNIT)
 
 #if defined(__GNUC__) && defined(__GNUC_MINOR__) && (__GNUC__ * 100 + __GNUC_MINOR__ > 301)
 #   pragma GCC system_header

diff --git a/include/boost/dll/detail/config.hpp b/include/boost/dll/detail/config.hpp
@@ -0,0 +1,29 @@
+// Copyright Fedor Osetrov, 2025-2026.
+//
+// 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)
+
+#ifndef BOOST_DLL_DETAIL_CONFIG_HPP
+#define BOOST_DLL_DETAIL_CONFIG_HPP
+
+#if !defined(BOOST_DLL_INTERFACE_UNIT)
+# include <boost/config.hpp>
+# ifdef BOOST_HAS_PRAGMA_ONCE
+# pragma once
+# endif
+#endif
+
+#ifdef BOOST_DLL_INTERFACE_UNIT
+# define BOOST_DLL_BEGIN_MODULE_EXPORT export {
+# define BOOST_DLL_END_MODULE_EXPORT }
+#else
+# define BOOST_DLL_BEGIN_MODULE_EXPORT
+# define BOOST_DLL_END_MODULE_EXPORT
+#endif
+
+#if defined(BOOST_USE_MODULES) && !defined(BOOST_DLL_INTERFACE_UNIT)
+import boost.dll;
+#endif
+
+#endif // BOOST_DLL_DETAIL_CONFIG_HPP
diff --git a/include/boost/dll/detail/demangling/demangle_symbol.hpp b/include/boost/dll/detail/demangling/demangle_symbol.hpp
@@ -9,9 +9,12 @@
 #define BOOST_DLL_DEMANGLE_SYMBOL_HPP_
 
 #include <boost/dll/config.hpp>
+
+#if !defined(BOOST_DLL_INTERFACE_UNIT)
 #include <string>
 #include <algorithm>
 #include <memory>
+#endif // !defined(BOOST_DLL_INTERFACE_UNIT)
 
 #if defined(_MSC_VER) // MSVC, Clang-cl, and ICC on Windows
 
@@ -61,7 +64,9 @@ inline std::string demangle_symbol(const std::string& mangled_name)
 }}}
 #else
 
+#if !defined(BOOST_DLL_INTERFACE_UNIT)
 #include <boost/core/demangle.hpp>
+#endif // !defined(BOOST_DLL_INTERFACE_UNIT)
 
 namespace boost
 {