Prepare use of CMAKE_CXX_MODULE_STD

We need at least cmake v3.28!

We need to set CMAKE_CXX_SCAN_FOR_MODULES too!

cleanup after review

Author: ClausKlein

.github/workflows/ci_tests.yml

@@ -27,7 +27,7 @@ jobs:
       - name: Setup build environment
         uses: lukka/get-cmake@latest
         with:
-          cmakeVersion: "~3.25.0"
+          cmakeVersion: "~3.28.0"
           ninjaVersion: "^1.11.1"
       - name: Setup MSVC
         if: startsWith(matrix.presets.platform, 'windows')
@@ -80,7 +80,7 @@ jobs:
       - name: Install Ninja
         uses: lukka/get-cmake@latest
         with:
-          cmakeVersion: "~3.25.0"
+          cmakeVersion: "~4.0.0"
           ninjaVersion: "^1.11.1"
       - name: Setup MSVC
         if: startsWith(matrix.platform.os, 'windows')
@@ -139,7 +139,7 @@ jobs:
       - name: Setup build environment
         uses: lukka/get-cmake@latest
         with:
-          cmakeVersion: "~3.25.0"
+          cmakeVersion: "~3.28.0"
           ninjaVersion: "^1.11.1"
       - name: Print installed softwares
         run: |
@@ -166,10 +166,10 @@ jobs:
       matrix:
         compilers:
           - class: GNU
-            version: 14
+            version: 15
             toolchain: "cmake/gnu-toolchain.cmake"
           - class: GNU
-            version: 13
+            version: 14
             toolchain: "cmake/gnu-toolchain.cmake"
           - class: LLVM
             version: 20
@@ -183,7 +183,7 @@ jobs:
       - name: Setup build environment
         uses: lukka/get-cmake@latest
         with:
-          cmakeVersion: "~3.25.0"
+          cmakeVersion: "~4.0.0"
           ninjaVersion: "^1.11.1"
       - name: Install Compiler
         id: install-compiler

CMakeLists.txt

@@ -1,6 +1,17 @@
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-cmake_minimum_required(VERSION 3.28)
+if(CMAKE_CXX_STANDARD STREQUAL 26)
+    set(CMAKE_CXX_SCAN_FOR_MODULES 1)
+    set(CMAKE_CXX_MODULE_STD 1)
+    if(CMAKE_CXX_MODULE_STD)
+        set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
+            "d0edc3af-4c50-42ea-a356-e2862fe7a444"
+        )
+    endif()
+    set(CMAKE_CXX_STANDARD_REQUIRED OFF)
+endif()
+
+cmake_minimum_required(VERSION 3.28...4.0)
 
 project(
     beman.scope
@@ -31,7 +42,7 @@ option(
     ${PROJECT_IS_TOP_LEVEL}
 )
 
-add_library(beman.scope)
+add_library(beman.scope INTERFACE)
 add_library(beman::scope ALIAS beman.scope)
 
 # gersemi: off
@@ -43,17 +54,29 @@ set_target_properties(
         EXPORT_NAME scope
 )
 
-target_sources(
-    beman.scope
-    PUBLIC
-        FILE_SET HEADERS
-        BASE_DIRS include
-        FILES include/beman/scope/scope.hpp
-    PUBLIC
-        FILE_SET CXX_MODULES
-        BASE_DIRS include
-        FILES include/beman/scope/beman.scope.cppm
-)
+if(CMAKE_CXX_SCAN_FOR_MODULES)
+    target_compile_features(beman.scope PRIVATE cxx_std_23)
+    target_sources(
+        beman.scope
+        PUBLIC
+            FILE_SET HEADERS
+            BASE_DIRS include
+            FILES include/beman/scope/scope.hpp
+        PUBLIC
+            FILE_SET CXX_MODULES
+            BASE_DIRS include
+            FILES include/beman/scope/beman.scope.cppm
+    )
+else()
+    target_compile_features(beman.scope INTERFACE cxx_std_20)
+    target_sources(
+        beman.scope
+        INTERFACE
+            FILE_SET HEADERS
+            BASE_DIRS include
+            FILES include/beman/scope/scope.hpp
+    )
+endif()
 
 include(GNUInstallDirs)
 
@@ -63,7 +86,6 @@ install(
     EXPORT beman.scope-targets
 
     FILE_SET CXX_MODULES
-        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
     FILE_SET HEADERS
 )
 

tests/CMakeLists.txt

@@ -5,7 +5,9 @@ include(FetchContent)
 FetchContent_Declare(
     Catch2
     GIT_REPOSITORY https://github.com/catchorg/Catch2.git
-    GIT_TAG v3.8.0
+    GIT_TAG v3.8.1
+    SYSTEM
+    # FIXME: FIND_PACKAGE_ARGS 3.8.1
 )
 FetchContent_MakeAvailable(Catch2)
 
@@ -15,18 +17,21 @@ message("Tests to be built: ${ALL_TESTNAMES}")
 
 include(Catch)
 
-add_executable(test.module)
-target_sources(test.module PRIVATE module.test.cpp)
-target_link_libraries(test.module PRIVATE beman::scope)
-add_test(NAME test.module COMMAND test.module)
-
-# todo: gc++15 module and catch incompatiblity?
-# target_link_libraries(
-#     test.module
-#     PUBLIC FILE_SET TYPE CXX_MODULES include/beman/scope/beman.scope.cppm
-#     PRIVATE Catch2::Catch2WithMain beman::scope
-# )
-# catch_discover_tests(test.module)
+if(CMAKE_CXX_SCAN_FOR_MODULES)
+    add_executable(test.module)
+    target_sources(test.module PRIVATE module.test.cpp)
+    target_compile_features(test.module PRIVATE cxx_std_23)
+    target_link_libraries(test.module PRIVATE beman::scope)
+    add_test(NAME test.module COMMAND test.module)
+
+    # XXX NO! target_compile_options(test.module PRIVATE "-fmodules")
+    # target_link_libraries(
+    #     test.module
+    #     PUBLIC FILE_SET TYPE CXX_MODULES include/beman/scope/beman.scope.cppm
+    #     PRIVATE Catch2::Catch2WithMain beman::scope
+    # )
+    # catch_discover_tests(test.module)
+endif()
 
 foreach(testname ${ALL_TESTNAMES})
     add_executable(test.${testname})

tests/module.test.cpp

@@ -1,8 +1,11 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+// TODO(CK): import std;
+
 import beman.scope;
 // #include <stdexcept>
 // #include <string>
+// FIXME: #include <print>
 #include <cassert>
 
 // #define CATCH_CONFIG_MAIN
@@ -13,15 +16,16 @@ import beman.scope;
 //     noisy_resource()  { std::print( "construct noisy\n" ); }
 //     ~noisy_resource() { std::print( "destroy noisy\n"   ); }
 // };
+// clang-format on
 
-//TEST_CASE("module-test", "[scope_module_test]") {
-int main()
-{
+// TEST_CASE("module-test", "[scope_module_test]") {
+int main() {
     bool exit_ran, success_ran, fail_ran = false;
     {
-        beman::scope::scope_exit    _([&exit_ran]    { exit_ran = true;    });
+        beman::scope::scope_exit    _([&exit_ran] { exit_ran = true; });
         beman::scope::scope_success _([&success_ran] { success_ran = true; });
-        beman::scope::scope_fail    _([&fail_ran]    { fail_ran = true;    });
+        beman::scope::scope_fail    _([&fail_ran] { fail_ran = true; });
+        // FIXME:
         // auto                        resource_ptr = beman::scope::unique_resource(new noisy_resource(),
         //                                                   // Cleanup function
         //                                                   [](noisy_resource* ptr) { delete ptr; });
@@ -30,5 +34,4 @@ int main()
     assert(exit_ran == true);
     assert(success_ran == true);
     assert(fail_ran == false);
-
- }
+}