Use CXX_MODULE_STD

.TODO.txt

@@ -3,7 +3,7 @@ Executing workflow step 1 of 5: configure preset "dev"
 Preset CMake variables:
 
   CMAKE_BUILD_TYPE="Debug"
-  CMAKE_CXX_EXTENSIONS="OFF"
+  CMAKE_CXX_EXTENSIONS="ON"
   CMAKE_CXX_FLAGS="-fstack-protector-strong -Wall -Wextra -Wpedantic -Wno-conversion -Wno-sign-conversion -Wcast-qual -Wformat=2 -Wundef -Werror=float-equal -Wshadow -Wcast-align -Wunused -Wnull-dereference -Wdouble-promotion -Wno-implicit-fallthrough -Wextra-semi -Woverloaded-virtual -Wnon-virtual-dtor -Wno-old-style-cast"
   CMAKE_CXX_STANDARD="20"
   CMAKE_CXX_STANDARD_REQUIRED="ON"

CMakeLists.txt

@@ -5,7 +5,7 @@ include(cmake/prelude.cmake)
 
 # Set experimental flag to enable `import std` support from CMake.
 # This must be enabled before C++ language support.
-# TODO: set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD 0e5b6991-d74f-4b3d-a41c-cf096e0b2508)
+#XXX set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD 0e5b6991-d74f-4b3d-a41c-cf096e0b2508)
 
 project(fmt
         VERSION 11.1.1.1
@@ -16,21 +16,24 @@ project(fmt
 
 include(cmake/variables.cmake)
 
-set(CMAKE_CXX_STANDARD 23)
-set(CMAKE_CXX_EXTENSIONS ON)
-set(CMAKE_CXX_STANDARD_REQUIRED YES)
+if(NOT CMAKE_CXX_STANDARD)
+  set(CMAKE_CXX_STANDARD 23)
+  set(CMAKE_CXX_EXTENSIONS ON)
+  set(CMAKE_CXX_STANDARD_REQUIRED ON)
+endif()
 
 set(CMAKE_DEBUG_POSTFIX D)
 # to prevent -Winclude-angled-in-module-purview in fmt/os.h
 # see /Users/clausklein/.cache/CPM/fmt/297020319ba1d5d14e1599714def59a1788711c5/include/fmt/os.h:33
 set(CPPdefinitions FMT_USE_FCNTL=0)
 set(ADD_STDLIB_MODULES)
 
-option(FMT_SEPARATE_COMPILATION "build fmt lib too" ${PROJECT_IS_TOP_LEVEL})
-option(FMT_USE_MODULES "Export a CXX_MODULE fmt if possible" ${PROJECT_IS_TOP_LEVEL})
-option(FMT_IMPORT_STD "Import the module std" ${PROJECT_IS_TOP_LEVEL})
+option(FMT_SEPARATE_COMPILATION "build fmt lib too" ON)
+option(FMT_USE_MODULES "Export a CXX_MODULE fmt if possible" ON)
+option(FMT_IMPORT_STD "Import the module std" ON)
 
 if(FMT_USE_MODULES)
+  set(CMAKE_CXX_SCAN_FOR_MODULES ON)
   list(APPEND CPPdefinitions FMT_MODULE)
   # FIXME: NO! list(APPEND CPPdefinitions FMT_ATTACH_TO_GLOBAL_MODULE)
 
@@ -55,27 +58,29 @@ if(FMT_USE_MODULES)
       add_compile_options(-stdlib=libc++)
       add_link_options(-stdlib=libc++)
     endif()
+  endif()
 
-    # Tell CMake that we explicitly want `import std`.
-    # This will initialize the property on all targets declared after this to 1
-    if(CMAKE_CXX_COMPILER_IMPORT_STD)
-      set(CMAKE_CXX_MODULE_STD ON)
-    endif()
+  # Tell CMake that we explicitly want `import std`.
+  # This will initialize the property on all targets declared after this to 1
+  if(CMAKE_CXX_COMPILER_IMPORT_STD)
+    set(CMAKE_CXX_MODULE_STD ON)
+    #XXX unset(ADD_STDLIB_MODULES)
+  endif()
 
-    if(CMAKE_CXX_MODULE_STD AND ADD_STDLIB_MODULES)
-      # FIXME: NO! list(APPEND CPPdefinitions FMT_IMPORT_STD)
-      list(APPEND CPPdefinitions HAS_STDLIB_MODULES)
-    endif()
+  if(CMAKE_CXX_MODULE_STD OR ADD_STDLIB_MODULES)
+    # FIXME: NO! list(APPEND CPPdefinitions FMT_IMPORT_STD)
+    list(APPEND CPPdefinitions HAS_STDLIB_MODULES)
   endif()
 
   message(STATUS "CMAKE_CXX_COMPILER_IMPORT_STD=${CMAKE_CXX_COMPILER_IMPORT_STD}")
-
+  message(STATUS "CMAKE_CXX_SCAN_FOR_MODULES=${CMAKE_CXX_SCAN_FOR_MODULES}")
+  message(STATUS "CMAKE_CXX_MODULE_STD=${CMAKE_CXX_MODULE_STD}")
   message(STATUS "CPPdefinitions=${CPPdefinitions}")
 else()
   set(CMAKE_VERIFY_INTERFACE_HEADER_SETS ${PROJECT_IS_TOP_LEVEL})
 endif()
 
-if(ADD_STDLIB_MODULES AND CMAKE_BUILD_TYPE STREQUAL Release)
+if(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD AND CMAKE_BUILD_TYPE STREQUAL Release)
   include(cmake/example.cmake)
 endif()
 
@@ -89,7 +94,7 @@ cpmaddpackage(
   GITHUB_REPOSITORY fmtlib/fmt
   GIT_TAG 11.1.1
   VERSION 11.1.1
-  DOWNLOAD_ONLY YES
+  DOWNLOAD_ONLY ON
 )
 # cmake-format: on
 
@@ -130,15 +135,15 @@ if(FMT_SEPARATE_COMPILATION)
     fmt PUBLIC FILE_SET public_headers TYPE HEADERS BASE_DIRS ${fmt_SOURCE_DIR}/include FILES ${_fmt_public_header}
   )
 
+  target_compile_definitions(fmt PUBLIC ${CPPdefinitions})
+  target_compile_options(fmt PUBLIC $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CXX_COMPILER_ID:MSVC>>:/utf-8>)
   target_compile_features(
     fmt INTERFACE "$<$<COMPILE_FEATURES:cxx_std_23>:cxx_std_23>" "$<$<NOT:$<COMPILE_FEATURES:cxx_std_23>>:cxx_std_20>"
   )
 
-  target_compile_options(fmt PUBLIC $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CXX_COMPILER_ID:MSVC>>:/utf-8>)
-
   if(FMT_USE_MODULES)
-    add_library(fmt::fmt-module ALIAS fmt)
-    target_compile_definitions(fmt PUBLIC ${CPPdefinitions})
+    message(STATUS "FMT_USE_MODULES=${FMT_USE_MODULES}")
+    add_library(fmt::fmt_module ALIAS fmt)
     # cmake-format: off
     target_sources(fmt PUBLIC
         FILE_SET public_modules
@@ -152,8 +157,7 @@ if(FMT_SEPARATE_COMPILATION)
   else()
     add_library(fmt::fmt ALIAS fmt)
     set_target_properties(fmt PROPERTIES CXX_SCAN_FOR_MODULES OFF)
-    target_compile_definitions(fmt PUBLIC ${CPPdefinitions})
-    target_sources(fmt PUBLIC ${_fmt_all_sources})
+    target_sources(fmt PRIVATE ${_fmt_all_sources})
   endif()
 
   if(FMT_WARNINGS_AS_ERRORS AND FMT_DEVELOPER_MODE AND UNIX)

GNUmakefile

@@ -32,9 +32,9 @@ check: all
 	-ninja -C build/dev spell-check
 
 test:
-	cmake --preset ci-${hostSystemName}
-	cmake --build build
-	cmake --install build --prefix $(CURDIR)/stagedir
+	# cmake --preset ci-${hostSystemName} --fresh
+	# cmake --build build
+	# cmake --install build --prefix $(CURDIR)/stagedir
 	cmake -G Ninja -B build/tests -S tests -D CMAKE_PREFIX_PATH=$(CURDIR)/stagedir
 	cmake --build build/tests
 	ctest --test-dir build/tests

cmake/dev-mode.cmake

@@ -4,7 +4,7 @@ option(FMT_BUILD_TESTING "Use ctest" ON)
 if(FMT_BUILD_TESTING)
   enable_testing()
 
-  add_subdirectory(tests)
+  # XXX add_subdirectory(tests)
   add_subdirectory(module/tests)
 endif()
 

cmake/install-rules.cmake

@@ -21,10 +21,10 @@ if(FMT_USE_MODULES)
   install(TARGETS fmt EXPORT fmtTargets FILE_SET public_headers #
                                         FILE_SET public_modules DESTINATION ${FMT_INSTALL_CMAKEDIR}/module
   )
-  install(FILES module/fmt.cppm DESTINATION ${FMT_INSTALL_CMAKEDIR}/module)
 else()
   install(TARGETS fmt EXPORT fmtTargets FILE_SET public_headers)
 endif()
+install(FILES module/fmt.cppm DESTINATION ${FMT_INSTALL_CMAKEDIR}/module)
 install(FILES ${_fmt_all_sources} DESTINATION ${FMT_INSTALL_CMAKEDIR}/module)
 
 write_basic_package_version_file("${_package}ConfigVersion.cmake" COMPATIBILITY SameMajorVersion ARCH_INDEPENDENT)

module/tests/CMakeLists.txt

@@ -35,9 +35,11 @@ if(PROJECT_IS_TOP_LEVEL)
     if(NOT CMAKE_CXX_COMPILER_IMPORT_STD AND ADD_STDLIB_MODULES)
       message(WARNING "ADD_STDLIB_MODULES=${ADD_STDLIB_MODULES}")
       add_stdlib_module(${ADD_STDLIB_MODULES})
+    else()
+      unset(ADD_STDLIB_MODULES)
     endif()
     # Build the fmt module
-    add_fmt_module(fmt-module)
+    add_fmt_module(fmt_module)
   endif()
 endif()
 
@@ -48,8 +50,10 @@ message(STATUS "Module tests to be built: ${ALL_TESTS}")
 foreach(_file ${ALL_TESTS})
   add_executable(module_${_file})
   target_sources(module_${_file} PRIVATE ../../tests/${_file}.cc)
-  if(USE_MODULES)
-    target_link_libraries(module_${_file} fmt-module ${ADD_STDLIB_MODULES})
+  if(CMAKE_CXX_MODULE_STD)
+    target_link_libraries(module_${_file} PUBLIC fmt_module)
+  elseif(ADD_STDLIB_MODULES)
+    target_link_libraries(module_${_file} PUBLIC fmt_module ${ADD_STDLIB_MODULES})
   else()
     target_link_libraries(module_${_file} fmt::fmt-header-only)
   endif()

tests/CMakeLists.txt

@@ -1,5 +1,9 @@
 cmake_minimum_required(VERSION 3.30...3.31)
 
+# Set experimental flag to enable `import std` support from CMake.
+# This must be enabled before C++ language support.
+set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD 0e5b6991-d74f-4b3d-a41c-cf096e0b2508)
+
 project(fmt_test LANGUAGES CXX)
 
 include(../cmake/folders.cmake OPTIONAL)
@@ -10,8 +14,10 @@ include(../cmake/windows-set-path.cmake OPTIONAL)
 if(PROJECT_IS_TOP_LEVEL)
   enable_testing()
 
-  find_package(fmt 11.1.1.1 EXACT REQUIRED)
-  include(../cmake/CPM.cmake)
+  #XXX find_package(fmt 11.1.1.1 EXACT REQUIRED)
+
+  set(ADD_STDLIB_MODULES stdlib)
+  add_subdirectory(.. fmt_module)
 endif()
 
 # ---- Tests ----
@@ -45,8 +51,10 @@ if(FMT_USE_MODULES)
   if(NOT CMAKE_CXX_COMPILER_IMPORT_STD AND ADD_STDLIB_MODULES)
     message(WARNING "ADD_STDLIB_MODULES=${ADD_STDLIB_MODULES}")
     add_stdlib_module(${ADD_STDLIB_MODULES})
+  else()
+    unset(ADD_STDLIB_MODULES)
   endif()
-  target_link_libraries(header-only-test ${ADD_STDLIB_MODULES} fmt::fmt-module)
+  target_link_libraries(header-only-test PUBLIC fmt::fmt_module ${ADD_STDLIB_MODULES})
 else()
   target_link_libraries(header-only-test fmt::fmt-header-only)
 endif()
@@ -80,8 +88,8 @@ if(NOT PROJECT_IS_TOP_LEVEL)
           "-DADD_STDLIB_MODULES=${ADD_STDLIB_MODULES}"
           "-DLLVM_LIBC_SOURCE=${LLVM_LIBC_SOURCE}"
           "-DLLVM_ROOT=${LLVM_ROOT}"
-          # TODO: "-DCMAKE_CXX_MODULE_STD=ON"
-          # TODO: "-DCMAKE_EXPERIMENTAL_CXX_IMPORT_STD=0e5b6991-d74f-4b3d-a41c-cf096e0b2508"
+          "-DCMAKE_CXX_MODULE_STD=ON"
+          "-DCMAKE_EXPERIMENTAL_CXX_IMPORT_STD=0e5b6991-d74f-4b3d-a41c-cf096e0b2508"
     )
   endif()
   # cmake-format: on