feat: Add C++ modules support

.github/workflows/test-docs-examples.yml

@@ -18,7 +18,7 @@ permissions:
 jobs:
   test_docs_examples:
     name: Test build examples
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-24.04
     concurrency:
       group: ${{ github.workflow }}-${{ github.ref }}
       cancel-in-progress: true
@@ -35,17 +35,59 @@ jobs:
           submodules: recursive
 
       - name: Install apt packages
-        run: sudo sed -i 's/azure\.//' /etc/apt/sources.list && sudo apt-get update && sudo apt-get install -y g++-12 libopus-dev zlib1g-dev libmpg123-dev liboggz-dev cmake libfmt-dev libopusfile-dev
+        run: sudo sed -i 's/azure\.//' /etc/apt/sources.list && sudo apt-get update && sudo apt-get install -y clang-20 libopus-dev ninja-build zlib1g-dev libmpg123-dev liboggz-dev cmake libfmt-dev libopusfile-dev
 
       - name: Generate CMake
-        run: mkdir build && cd build && cmake -DDPP_NO_VCPKG=ON -DAVX_TYPE=T_fallback -DDPP_CORO=ON -DCMAKE_BUILD_TYPE=Debug ..
+        run: mkdir build && cd build && cmake -G Ninja -DDPP_NO_VCPKG=ON -DDPP_MODULES=ON -DAVX_TYPE=T_fallback -DDPP_CORO=ON -DCMAKE_BUILD_TYPE=Debug ..
         env:
-          CXX: g++-12
+          CXX: clang++-20
 
       - name: Build Project
-        run: cd build && make -j2 && sudo make install
+        run: cd build && cmake --build . -j2 && sudo ninja install
+        env:
+          CXX: clang++-20
 
       - name: Test compile examples
-        run: cd docpages/example_code && mkdir build && cd build && cmake .. && make -j2
+        run: cd docpages/example_code && mkdir build && cd build && cmake -G Ninja -DDPP_MODULES=ON .. && cmake --build . -j2
+        env:
+          CXX: clang++-20
+
+  test_docs_module_windows:
+    name: Test build module (Windows)
+    runs-on: windows-2022
+    # Experimental: clang-cl C++20 module scanning is only supported from
+    # CMake 4.4 onwards, and cl.exe cannot consume the nlohmann::json-wrapping
+    # module. Keep this non-blocking while the toolchain support matures.
+    continue-on-error: true
+    concurrency:
+      group: ${{ github.workflow }}-windows-${{ github.ref }}
+      cancel-in-progress: true
+    steps:
+      - name: Harden Runner
+        uses: step-security/harden-runner@9af89fc71515a100421586dfdb3dc9c984fbf411 # v2.19.4
+        with:
+          egress-policy: audit
+
+      - name: Checkout D++
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+        with:
+          submodules: recursive
+
+      - name: Set up MSVC developer environment
+        uses: ilammy/msvc-dev-cmd@0b201ec74fa43914dc39ae48a89fd1d8cb592756 # v1.13.0
+
+      - name: Set up CMake
+        uses: jwlawson/actions-setup-cmake@0d6a7d60b009d01c9e7523be22153ff8f19460d3 # v2.2.0
+        with:
+          cmake-version: '4.4.x'
+          github-api-token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Generate CMake
+        run: cmake -B build -G Ninja -DCMAKE_C_COMPILER=clang-cl -DCMAKE_CXX_COMPILER=clang-cl -DCMAKE_BUILD_TYPE=Release -DDPP_NO_VCPKG=ON -DDPP_MODULES=ON -DDPP_BUILD_TEST=ON -DAVX_TYPE=AVX0
+        env:
+          DONT_RUN_VCPKG: true
+
+      - name: Build module example
+        run: cmake --build build --target using_modules_example --parallel 2
         env:
-          CXX: g++-12
+          DONT_RUN_VCPKG: true

CMakeLists.txt

@@ -18,7 +18,7 @@
 
 cmake_minimum_required (VERSION 3.16)
 set(CMAKE_CXX_STANDARD 17)
- 
+
 option(BUILD_SHARED_LIBS "Build shared libraries" ON)
 option(BUILD_VOICE_SUPPORT "Build voice support" ON)
 option(RUN_LDCONFIG "Run ldconfig after installation" ON)
@@ -33,6 +33,7 @@ option(DPP_USE_EXTERNAL_JSON "Use an external installation of nlohmann::json" OF
 option(DPP_USE_PCH "Use precompiled headers to speed up compilation" OFF)
 option(AVX_TYPE "Force AVX type for speeding up audio mixing" OFF)
 option(DPP_TEST_VCPKG "Force VCPKG build without VCPKG installed (for development use only!)" OFF)
+option(DPP_MODULES "Support for C++20 modules (experimental)" OFF)
 
 include(CheckCXXSymbolExists)
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
@@ -159,3 +160,4 @@ endif()
 if (NOT WIN32)
 	target_link_libraries(dpp PRIVATE std::filesystem)
 endif()
+

README.md

@@ -33,6 +33,7 @@ D++ is a lightweight and efficient library for **Discord** written in **modern C
 * Stable [Windows support](https://dpp.dev/buildwindows.html)
 * Ready-made compiled packages for Windows, Raspberry Pi (ARM64/ARM7/ARMv6), Debian x86/x64, and RPM based distributions
 * Highly scalable for large amounts of guilds and users
+* Experimental support for [C++ modules](https://dpp.dev/using_modules.html)
 
 Want to help? Drop me a line or send a PR.
 

cmake/CPackSetup.cmake

@@ -11,20 +11,40 @@ set(DPP_INSTALL_LIBRARY_DIR ${CMAKE_INSTALL_LIBDIR}/${DPP_VERSIONED})
 
 ## Pack the binary output
 if (WIN32)
-	install(TARGETS dpp
-		EXPORT ${DPP_EXPORT_NAME}
-		LIBRARY DESTINATION  ${DPP_INSTALL_LIBRARY_DIR}
-		ARCHIVE DESTINATION  ${DPP_INSTALL_LIBRARY_DIR}
-		RUNTIME DESTINATION  ${CMAKE_INSTALL_BINDIR}
-		INCLUDES DESTINATION ${DPP_INSTALL_INCLUDE_DIR})
+	if (DPP_MODULES)
+		install(TARGETS dpp
+			EXPORT ${DPP_EXPORT_NAME}
+			LIBRARY DESTINATION  ${DPP_INSTALL_LIBRARY_DIR}
+			ARCHIVE DESTINATION  ${DPP_INSTALL_LIBRARY_DIR}
+			RUNTIME DESTINATION  ${CMAKE_INSTALL_BINDIR}
+			INCLUDES DESTINATION ${DPP_INSTALL_INCLUDE_DIR}
+			FILE_SET CXX_MODULES DESTINATION ${DPP_INSTALL_INCLUDE_DIR})
+	else()
+		install(TARGETS dpp
+			EXPORT ${DPP_EXPORT_NAME}
+			LIBRARY DESTINATION  ${DPP_INSTALL_LIBRARY_DIR}
+			ARCHIVE DESTINATION  ${DPP_INSTALL_LIBRARY_DIR}
+			RUNTIME DESTINATION  ${CMAKE_INSTALL_BINDIR}
+			INCLUDES DESTINATION ${DPP_INSTALL_INCLUDE_DIR})
+	endif()
 	install(DIRECTORY "${DPP_ROOT_PATH}/include/" DESTINATION "${DPP_INSTALL_INCLUDE_DIR}")
 else()
-	install(TARGETS dpp
-		EXPORT ${DPP_EXPORT_NAME}
-		LIBRARY DESTINATION  ${CMAKE_INSTALL_LIBDIR}
-		ARCHIVE DESTINATION  ${CMAKE_INSTALL_LIBDIR}
-		RUNTIME DESTINATION  ${CMAKE_INSTALL_BINDIR}
-		INCLUDES DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+	if (DPP_MODULES)
+		install(TARGETS dpp
+			EXPORT ${DPP_EXPORT_NAME}
+			LIBRARY DESTINATION  ${CMAKE_INSTALL_LIBDIR}
+			ARCHIVE DESTINATION  ${CMAKE_INSTALL_LIBDIR}
+			RUNTIME DESTINATION  ${CMAKE_INSTALL_BINDIR}
+			INCLUDES DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+			FILE_SET CXX_MODULES DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+	else()
+		install(TARGETS dpp
+			EXPORT ${DPP_EXPORT_NAME}
+			LIBRARY DESTINATION  ${CMAKE_INSTALL_LIBDIR}
+			ARCHIVE DESTINATION  ${CMAKE_INSTALL_LIBDIR}
+			RUNTIME DESTINATION  ${CMAKE_INSTALL_BINDIR}
+			INCLUDES DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+	endif()
 endif()
 
 ## Allow for a specific version to be chosen in the `find_package` command
@@ -34,7 +54,13 @@ write_basic_package_version_file(${DPP_VERSION_FILE}
 		COMPATIBILITY SameMajorVersion)
 
 ## Include the file which allows `find_package(dpp)` to function.
-install(FILES "${DPP_ROOT_PATH}/cmake/dpp-config.cmake" "${DPP_VERSION_FILE}" DESTINATION "${DPP_CMAKE_DIR}")
+## FindFilesystem.cmake is shipped alongside it because dpp-config.cmake calls
+## find_dependency(Filesystem) (the C++20 module links std::filesystem).
+install(FILES
+	"${DPP_ROOT_PATH}/cmake/dpp-config.cmake"
+	"${DPP_ROOT_PATH}/cmake/FindFilesystem.cmake"
+	"${DPP_VERSION_FILE}"
+	DESTINATION "${DPP_CMAKE_DIR}")
 
 ## Export the targets to allow other projects to easily include this project
 install(EXPORT "${DPP_EXPORT_NAME}" DESTINATION "${DPP_CMAKE_DIR}" NAMESPACE dpp::)

cmake/dpp-config.cmake

@@ -3,8 +3,10 @@
 ## Get current filesystem path (will a prefixed by where this package was installed)
 get_filename_component(SELF_DIR "${CMAKE_CURRENT_LIST_FILE}" PATH)
 
-## Use this directory to include dpp which has the rest of the project targets
-include(${SELF_DIR}/dpp.cmake)
+## Make bundled find-modules (e.g. FindFilesystem) discoverable by find_dependency below.
+list(APPEND CMAKE_MODULE_PATH "${SELF_DIR}")
+
+include(CMakeFindDependencyMacro)
 
 ## Set OpenSSl directory for macos. It is also in our main CMakeLists.txt, but this file is independent from that.
 if(APPLE)
@@ -13,9 +15,15 @@ if(APPLE)
 	else()
 		set(OPENSSL_ROOT_DIR "/usr/local/opt/openssl")
 	endif()
-	find_package(OpenSSL REQUIRED)
 endif()
 
-# Search for libdpp dependencies
-include(CMakeFindDependencyMacro)
+## Search for libdpp dependencies
 find_dependency(OpenSSL REQUIRED)
+
+## When D++ is built with C++20 module support the exported module links against the
+## std::filesystem imported target on toolchains that need a separate <filesystem>
+## library, so consumers must be able to resolve it too. Harmless otherwise.
+find_dependency(Filesystem REQUIRED)
+
+## Use this directory to include dpp which has the rest of the project targets
+include(${SELF_DIR}/dpp.cmake)

docpages/example_code/CMakeLists.txt

@@ -28,19 +28,31 @@
 # libmpg123-dev
 # dpp latest master with -DDPP_CORO=ON installed sytemwide
 
-cmake_minimum_required (VERSION 3.16)
+cmake_minimum_required (VERSION 3.28)
 project(documentation_tests)
 
 include("${CMAKE_CURRENT_SOURCE_DIR}/../../cmake/colour.cmake")
 
-set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DDPP_CORO -std=c++20 -pthread -O0 -fPIC -rdynamic -DFMT_HEADER_ONLY -Wall -Wextra -Wpedantic -Werror -Wno-unused-parameter -Wno-deprecated-declarations")
+option(DPP_MODULES "Build examples with C++20 modules support" ON)
+
+find_package(dpp REQUIRED)
+
+set(CMAKE_CXX_EXTENSIONS OFF)
+
+set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DDPP_CORO -std=c++20 -pthread -O0 -fPIC -DFMT_HEADER_ONLY -Wall -Wextra -Wpedantic -Werror -Wno-unused-parameter -Wno-deprecated-declarations -Wno-unused-command-line-argument")
 set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -O0")
 
+set (CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -rdynamic")
+
 file(GLOB example_list ./*.cpp)
 foreach (example ${example_list})
 	get_filename_component(examplename ${example} NAME)
 	message(STATUS "Found example '${BoldBlue}${examplename}${ColourReset}'")
 	add_executable(${examplename}_out ${example})
-	target_link_libraries(${examplename}_out dl dpp mpg123 oggz ogg opusfile opus)
+	target_link_libraries(${examplename}_out dl dpp::dpp mpg123 oggz ogg opusfile opus)
 	include_directories(/usr/include/opus)
+
+	if (DPP_MODULES)
+		set_target_properties(${examplename}_out PROPERTIES CXX_SCAN_FOR_MODULES ON)
+	endif()
 endforeach(example)

docpages/example_code/using_modules.cpp

@@ -0,0 +1,24 @@
+#include <string>
+
+import dpp;
+
+int main() {
+	dpp::cluster bot("YOUR_BOT_TOKEN_HERE");
+
+	bot.on_slashcommand([](const dpp::slashcommand_t& event) -> void {
+		if (event.command.get_command_name() == "ping") {
+			event.reply("Pong!");
+		}
+	});
+
+	bot.on_ready([&bot](const dpp::ready_t& event) -> void {
+		if (dpp::run_once<struct register_bot_commands>()) {
+			bot.global_command_create(
+				dpp::slashcommand("ping", "Ping pong!", bot.me.id)
+			);
+		}
+	});
+
+	bot.start(dpp::start_type::st_wait);
+	return 0;
+}

docpages/example_programs/misc.md

@@ -13,3 +13,4 @@ This section lists examples that do not fit neatly into any of the categories ab
 * \subpage setting_status
 * \subpage using-emojis
 * \subpage using_timers
+* \subpage using_modules

docpages/example_programs/misc/using_modules.md

@@ -0,0 +1,11 @@
+\page using_modules Using D++ with C++ modules
+
+\include{doc} modules_warn.dox
+
+D++ is offered as a C++ module, which offers improved compile times over a traditional header.
+
+In order to enable support, you must use C++20 (or later) with any module-supporting compiler. To activate the feature, pass the `DPP_MODULES` flag to CMake. Ensure that the generated build system supports modules (for CMake, this is usually Ninja; note CMake does not currently support modules with Makefile).
+
+Once this is done, simply `import dpp;` and we're good to go!
+
+\include{cpp} using_modules.cpp

docpages/include/modules_warn.dox

@@ -0,0 +1 @@
+\warning D++ modules are currently experimental and are only supported by D++ on g++ 15, clang/LLVM 17, and MSVC 17.6 or above. Additionally, your program has to support C++20.

include/dpp/cluster.h

@@ -58,7 +58,7 @@ namespace dpp {
  * requests to Discord. This is useful for bots that do not need to receive websocket events as it will save a lot of
  * resources.
  */
-constexpr uint32_t NO_SHARDS = ~0U;
+inline constexpr uint32_t NO_SHARDS = ~0U;
 
 /**
  * @brief Types of startup for cluster::start()

include/dpp/colors.h

@@ -31,7 +31,7 @@ namespace dpp {
  * @brief predefined color constants.
  */
 namespace colors {
-	static constexpr uint32_t
+	inline constexpr uint32_t
 		white = 0xFFFFFF,
 		discord_white = 0xFFFFFE,
 		light_gray = 0xC0C0C0,

include/dpp/discordclient.h

@@ -57,7 +57,7 @@ class cluster;
  * @brief How many seconds to wait between (re)connections. DO NOT change this.
  * It is mandated by the Discord API spec!
  */
-constexpr time_t RECONNECT_INTERVAL = 5;
+inline constexpr time_t RECONNECT_INTERVAL = 5;
 
 /**
  * @brief Represents different event opcodes sent and received on a shard websocket

include/dpp/dpp.cppm

@@ -0,0 +1,83 @@
+/************************************************************************************
+ *
+ * D++, A Lightweight C++ library for Discord
+ *
+ * Copyright 2021 Craig Edwards and D++ contributors
+ * (https://github.com/brainboxdotcc/DPP/graphs/contributors)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ ************************************************************************************/
+
+module;
+
+// Include the entire standard library so it doesn't cause issue in our headers
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <ctime>
+
+#include <algorithm>
+#include <charconv>
+#include <condition_variable>
+#include <cstddef>
+#include <ctime>
+#include <deque>
+#include <exception>
+#include <fstream>
+#include <functional>
+#include <iomanip>
+#include <iostream>
+#include <locale>
+#include <map>
+#include <memory>
+#include <mutex>
+#include <optional>
+#include <queue>
+#include <shared_mutex>
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <thread>
+#include <type_traits>
+#include <unordered_map>
+#include <variant>
+#include <vector>
+
+#include <dpp/export.h>
+#include <dpp/compat.h>
+
+#ifdef DPP_USE_EXTERNAL_JSON
+	#include <nlohmann/json.hpp>
+#else
+	#include <dpp/nlohmann/json.hpp>
+#endif
+
+export module dpp;
+
+export extern "C++" {
+    #if defined(__clang__)
+        #pragma clang diagnostic push
+        #pragma clang diagnostic ignored "-Wunknown-warning-option"
+        #pragma clang diagnostic ignored "-Winclude-angled-in-module-purview"
+    #endif
+
+    #include <dpp/dpp.h>
+    #include <dpp/dns.h>
+    #include <dpp/restrequest.h>
+    #include <dpp/unicode_emoji.h>
+
+    #if defined(__clang__)
+        #pragma clang diagnostic pop
+    #endif
+}