Initial support for the C++20 modules

Author: apolukhin

CMakeLists.txt

@@ -16,6 +16,10 @@ target_link_libraries(boost_throw_exception
     Boost::config
 )
 
+if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.28.0" AND BUILD_MODULE)
+    add_subdirectory(module)
+endif()
+
 if(BUILD_TESTING)
 
   add_subdirectory(test)

include/boost/exception/exception.hpp

@@ -6,16 +6,28 @@
 #ifndef BOOST_EXCEPTION_274DA366004E11DCB1DDFE2E56D89593
 #define BOOST_EXCEPTION_274DA366004E11DCB1DDFE2E56D89593
 
+#ifndef BOOST_THROW_EXCEPTION_BEGIN_MODULE_EXPORT
+#define BOOST_THROW_EXCEPTION_BEGIN_MODULE_EXPORT
+#endif
+
+#ifndef BOOST_THROW_EXCEPTION_END_MODULE_EXPORT
+#define BOOST_THROW_EXCEPTION_END_MODULE_EXPORT
+#endif
+
 #include <boost/assert/source_location.hpp>
 #include <boost/config.hpp>
 #include <exception>
 
 #ifdef BOOST_EXCEPTION_MINI_BOOST
 #include  <memory>
+BOOST_THROW_EXCEPTION_BEGIN_MODULE_EXPORT
 namespace boost { namespace exception_detail { using std::shared_ptr; } }
+BOOST_THROW_EXCEPTION_END_MODULE_EXPORT
 #else
+BOOST_THROW_EXCEPTION_BEGIN_MODULE_EXPORT
 namespace boost { template <class T> class shared_ptr; }
 namespace boost { namespace exception_detail { using boost::shared_ptr; } }
+BOOST_THROW_EXCEPTION_END_MODULE_EXPORT
 #endif
 
 #if !defined(BOOST_EXCEPTION_ENABLE_WARNINGS)
@@ -31,6 +43,7 @@ namespace boost { namespace exception_detail { using boost::shared_ptr; } }
 #endif
 #endif
 
+BOOST_THROW_EXCEPTION_BEGIN_MODULE_EXPORT
 namespace
 boost
     {
@@ -566,4 +579,6 @@ boost
 #pragma warning(pop)
 #endif
 
+BOOST_THROW_EXCEPTION_END_MODULE_EXPORT
+
 #endif // #ifndef BOOST_EXCEPTION_274DA366004E11DCB1DDFE2E56D89593

include/boost/throw_exception.hpp

@@ -19,6 +19,7 @@
 //  http://www.boost.org/libs/throw_exception
 
 #include <boost/exception/exception.hpp>
+
 #include <boost/assert/source_location.hpp>
 #include <boost/config.hpp>
 #include <boost/config/workaround.hpp>
@@ -38,8 +39,10 @@ namespace boost
 
 #if defined( BOOST_NO_EXCEPTIONS )
 
+BOOST_THROW_EXCEPTION_BEGIN_MODULE_EXPORT
 BOOST_NORETURN void throw_exception( std::exception const & e ); // user defined
 BOOST_NORETURN void throw_exception( std::exception const & e, boost::source_location const & loc ); // user defined
+BOOST_THROW_EXCEPTION_END_MODULE_EXPORT
 
 #endif
 
@@ -68,6 +71,9 @@ template<class E, class B> struct wrapexcept_add_base<E, B, 2>
 
 } // namespace detail
 
+
+BOOST_THROW_EXCEPTION_BEGIN_MODULE_EXPORT
+
 template<class E> struct BOOST_SYMBOL_VISIBLE wrapexcept:
     public detail::wrapexcept_add_base<E, boost::exception_detail::clone_base>::type,
     public E,
@@ -175,6 +181,8 @@ template<class E> BOOST_NORETURN void throw_exception( E const & e, boost::sourc
 
 #endif // !defined( BOOST_NO_EXCEPTIONS )
 
+BOOST_THROW_EXCEPTION_END_MODULE_EXPORT
+
 } // namespace boost
 
 // BOOST_THROW_EXCEPTION
@@ -217,6 +225,8 @@ template<class E> class BOOST_SYMBOL_VISIBLE with_throw_location: public E, publ
 
 } // namespace detail
 
+BOOST_THROW_EXCEPTION_BEGIN_MODULE_EXPORT
+
 #if !defined(BOOST_NO_EXCEPTIONS)
 
 #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES) && !defined(BOOST_NO_CXX11_HDR_TYPE_TRAITS)
@@ -273,6 +283,8 @@ template<class E> boost::source_location get_throw_location( E const & e )
 #endif
 }
 
+BOOST_THROW_EXCEPTION_END_MODULE_EXPORT
+
 } // namespace boost
 
 #endif // #ifndef BOOST_THROW_EXCEPTION_HPP_INCLUDED

module/CMakeLists.txt

@@ -0,0 +1,37 @@
+# Copyright (c) 2025 Antony Polukhin
+#
+# Distributed under the Boost Software License, Version 1.0.
+# https://www.boost.org/LICENSE_1_0.txt
+
+cmake_minimum_required(VERSION 3.28)
+
+function (_add_boost_throw_exception_module_impl NAME)
+    add_library(${NAME})
+    target_compile_features(${NAME} PUBLIC cxx_std_20)
+    target_sources(${NAME} PUBLIC
+        FILE_SET modules_public TYPE CXX_MODULES FILES
+            ${CMAKE_CURRENT_LIST_DIR}/throw_exception.cppm
+    )
+endfunction()
+
+function (add_boost_throw_exception_module NAME)
+    _add_boost_throw_exception_module_impl(${NAME})
+    target_include_directories(${NAME} PRIVATE ${CMAKE_CURRENT_LIST_DIR}/../include)
+
+    _add_boost_throw_exception_module_impl(${NAME}_migration)
+    target_include_directories(${NAME}_migration PUBLIC ${CMAKE_CURRENT_LIST_DIR}/../include)
+    target_compile_definitions(${NAME}_migration PRIVATE BOOST_THROW_EXCEPTION_ATTACH_TO_GLOBAL_MODULE)
+endfunction()
+
+add_boost_throw_exception_module(boost_throw_exception_module)
+add_library(Boost::throw_exception_module ALIAS boost_throw_exception_module)
+add_library(Boost::throw_exception_module_migration ALIAS boost_throw_exception_module_migration)
+
+if (BUILD_TESTING)
+    add_executable(boost_throw_exception_module_usage usage_sample.cpp)
+    target_link_libraries(boost_throw_exception_module_usage PRIVATE Boost::throw_exception_module)
+
+    # Make sure that mixing includes and imports is fine for different TU
+    add_executable(boost_throw_exception_module_usage_mu usage_test_mu1.cpp usage_test_mu2.cpp)
+    target_link_libraries(boost_throw_exception_module_usage_mu PRIVATE Boost::throw_exception_module_migration)
+endif()

module/throw_exception.cppm

@@ -0,0 +1,43 @@
+// Copyright (c) 2016-2024 Antony Polukhin
+//
+// 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)
+
+// To compile manually use a command like the folowing:
+// clang++ -I ../include -std=c++20 --precompile -x c++-module throw_exception.cppm
+
+#define BOOST_THROW_EXCEPTION_BEGIN_MODULE_EXPORT export {
+#define BOOST_THROW_EXCEPTION_END_MODULE_EXPORT }
+
+module;
+
+#include <boost/assert/source_location.hpp> // TODO: modularize
+#include <boost/config.hpp>
+#include <boost/config/workaround.hpp>
+
+#ifndef BOOST_THROW_EXCEPTION_HAS_STD_MODULE
+#include <exception>
+#include <utility>
+#include <cstddef>
+#include <memory>
+#include <exception>
+#include <type_traits>
+#endif
+
+export module Boost.ThrowException;
+
+#ifdef BOOST_THROW_EXCEPTION_HAS_STD_MODULE
+import std;
+#endif
+
+#ifdef __clang__
+#   pragma clang diagnostic ignored "-Winclude-angled-in-module-purview"
+#endif
+
+#ifdef BOOST_THROW_EXCEPTION_ATTACH_TO_GLOBAL_MODULE
+extern "C++" {
+#include <boost/throw_exception.hpp>
+}
+#else
+#include <boost/throw_exception.hpp>
+#endif

module/usage_sample.cpp

@@ -0,0 +1,33 @@
+//Copyright (c) 2006-2009 Emil Dotchevski and Reverge Studios, Inc.
+//Copyright (c) 2025 Antony Polukhin.
+
+//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)
+
+// To compile manually use a command like the folowing:
+// clang++ -std=c++20 -fmodule-file=throw_exception.pcm throw_exception.pcm usage_sample.cpp
+
+#include <exception>
+
+import Boost.ThrowException;
+
+class my_exception: public std::exception { };
+
+int
+main()
+    {
+    try
+        {
+        boost::throw_exception(my_exception());
+        return 1;
+        }
+    catch(
+    my_exception & )
+        {
+        }
+    catch(
+    ... )
+        {
+        return 2;
+        }
+    }