c++: first try to get a C++ modules build rolling

Author: jcelerier

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.22 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.22..4.2.0 FATAL_ERROR)
 project(libremidi
   VERSION 5.3.1
   DESCRIPTION "A cross-platform MIDI library"
@@ -17,6 +17,7 @@ include(FetchContent)
 include(GNUInstallDirs)
 
 ### Options ###
+option(LIBREMIDI_MODULE_BUILD "C++ module mode" OFF)
 option(LIBREMIDI_HEADER_ONLY "Header-only mode" OFF)
 
 cmake_dependent_option(LIBREMIDI_NO_COREMIDI "Disable CoreMidi back-end" OFF "APPLE" OFF)

cmake/libremidi.cppwinrt.cmake

@@ -93,7 +93,6 @@ if(CPPWINRT_TOOL)
     COMMAND "${CPPWINRT_TOOL}"
       "@${CMAKE_BINARY_DIR}/cppwinrt-src/cppwinrt.rsp"
       -output "${CMAKE_BINARY_DIR}/cppwinrt"
-      -verbose
   )
 endif()
 

cmake/libremidi.examples.cmake

@@ -110,8 +110,14 @@ if(Boost_cobalt_FOUND)
   target_link_libraries(coroutines PRIVATE Boost::cobalt)
 endif()
 
-add_executable(libremidi_c_api examples/c_api.c)
-target_link_libraries(libremidi_c_api PRIVATE libremidi)
-if(LIBREMIDI_HEADER_ONLY)
-  target_sources(libremidi_c_api PRIVATE "${CMAKE_CURRENT_SOURCE_DIR}/include/libremidi/libremidi-c.cpp")
+if(NOT LIBREMIDI_MODULES_BUILD)
+  add_executable(libremidi_c_api examples/c_api.c)
+  target_link_libraries(libremidi_c_api PRIVATE libremidi)
+  if(LIBREMIDI_HEADER_ONLY)
+    target_sources(libremidi_c_api PRIVATE "${CMAKE_CURRENT_SOURCE_DIR}/include/libremidi/libremidi-c.cpp")
+  endif()
 endif()
+
+
+add_executable(libremidi_modules examples/modules.cppm)
+target_link_libraries(libremidi_modules PRIVATE libremidi)

cmake/libremidi.install.cmake

@@ -1,17 +1,22 @@
-if(NOT LIBREMIDI_HEADER_ONLY)
+if(LIBREMIDI_MODULE_BUILD)
+  message("Install not supported yet as of CMake 4.2")
+  return()
+elseif(NOT LIBREMIDI_HEADER_ONLY)
   install(TARGETS libremidi
           EXPORT libremidi-targets
           ARCHIVE
           RUNTIME
           LIBRARY
   )
+  install(EXPORT libremidi-targets
+          DESTINATION lib/cmake/libremidi)
 else()
   install(TARGETS libremidi
           EXPORT libremidi-targets
   )
+  install(EXPORT libremidi-targets
+          DESTINATION lib/cmake/libremidi)
 endif()
-install(EXPORT libremidi-targets
-        DESTINATION lib/cmake/libremidi)
 install(DIRECTORY include
         DESTINATION .)
 

cmake/libremidi.library.cmake

@@ -1,5 +1,15 @@
 ### Create the library ###
-if(LIBREMIDI_HEADER_ONLY)
+if(LIBREMIDI_MODULE_BUILD)
+  add_library(libremidi STATIC)
+  set(_public PUBLIC)
+  set(_private PRIVATE)
+  target_sources(libremidi
+    PUBLIC
+      FILE_SET CXX_MODULES
+      FILES
+        "src/libremidi.ixx"
+  )
+elseif(LIBREMIDI_HEADER_ONLY)
   add_library(libremidi INTERFACE)
   set(_public INTERFACE)
   set(_private INTERFACE)

cmake/libremidi.winmidi.cmake

@@ -46,7 +46,6 @@ if(CPPWINRT_TOOL)
     COMMAND "${CPPWINRT_TOOL}"
       "@${CMAKE_BINARY_DIR}/cppwinrt-src/cppwinrt-winmidi.rsp"
       -output "${CMAKE_BINARY_DIR}/cppwinrt-winmidi"
-      -verbose
   )
 
   file(

examples/modules.cppm

@@ -0,0 +1,33 @@
+import libremidi;
+
+#include "utils.hpp"
+
+#include <cstdlib>
+#include <iostream>
+
+int main()
+{
+  libremidi::observer observer;
+  if (observer.get_input_ports().empty())
+    return 1;
+  if (observer.get_output_ports().empty())
+    return 1;
+
+  libremidi::midi_in midi_in{{.on_message = [](const libremidi::message& message) {
+    std::cout << message << std::endl;
+  }}};
+
+  if (auto err = midi_in.open_port(observer.get_input_ports()[0]); err != stdx::error{})
+    err.throw_exception();
+
+  libremidi::midi_out midi_out;
+  if (auto err = midi_out.open_port(observer.get_output_ports()[0]); err != stdx::error{})
+    err.throw_exception();
+
+  midi_out.send_message(176, 7, 100);
+
+  int c;
+  while ((c = getchar()) != '\n' && c != EOF)
+    ;
+  return 0;
+}

include/libremidi/api-c.h

@@ -1,13 +1,15 @@
 #pragma once
+#ifndef LIBREMIDI_API_C_H
+#define LIBREMIDI_API_C_H
 
-#if __cplusplus
+#if __cplusplus && !defined(LIBREMIDI_MODULE_BUILD)
 extern "C" {
 #endif
 
 //! MIDI API specifier arguments.
 //! To get information on which feature is supported by each back-end, check their backend file
 //! in e.g. backends/winmm.hpp, etc.
-typedef enum libremidi_api
+enum libremidi_api
 {
   UNSPECIFIED = 0x0, /*!< Search for a working compiled API. */
 
@@ -36,8 +38,11 @@ typedef enum libremidi_api
   PIPEWIRE_UMP,          /*!< MIDI2 over PipeWire. Requires v1.4+. */
 
   DUMMY = 0xFFFF /*!< A compilable but non-functional API. */
-} libremidi_api;
+};
 
-#if __cplusplus
+typedef enum libremidi_api libremidi_api;
+
+#if __cplusplus && !defined(LIBREMIDI_MODULE_BUILD)
 }
 #endif
+#endif

include/libremidi/api.hpp

@@ -5,7 +5,7 @@
 #include <string_view>
 #include <vector>
 
-namespace libremidi
+NAMESPACE_LIBREMIDI
 {
 //! MIDI API specifier arguments.
 //! To get information on which feature is supported by each back-end, check their backend file

include/libremidi/backends.hpp

@@ -81,7 +81,7 @@
   #include <libremidi/backends/android/android.hpp>
 #endif
 
-namespace libremidi
+NAMESPACE_LIBREMIDI
 {
 // The order here will control the order of the API search in
 // the constructor.
@@ -93,7 +93,7 @@ constexpr auto make_tl(unused, Args...)
 
 namespace midi1
 {
-static constexpr auto available_backends = make_tl(
+LIBREMIDI_STATIC constexpr auto available_backends = make_tl(
     0
 #if defined(LIBREMIDI_ALSA)
     ,
@@ -167,7 +167,7 @@ auto for_backend(libremidi::API api, F&& f)
 
 namespace midi2
 {
-static constexpr auto available_backends = make_tl(
+LIBREMIDI_STATIC constexpr auto available_backends = make_tl(
     0
 #if defined(LIBREMIDI_ALSA) && LIBREMIDI_ALSA_HAS_UMP
     ,