[DRAFT][libc++][modules] Improves std.compat module.

libcxx/modules/CMakeLists.txt.in

@@ -3,12 +3,16 @@ cmake_minimum_required(VERSION 3.26)
 project(libc++-modules LANGUAGES CXX)
 
 # Enable CMake's module support
-if(CMAKE_VERSION VERSION_LESS "3.27.0")
-  set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "2182bf5c-ef0d-489a-91da-49dbc3090d2a")
+if(CMAKE_VERSION VERSION_LESS "3.28.0")
+  if(CMAKE_VERSION VERSION_LESS "3.27.0")
+    set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "2182bf5c-ef0d-489a-91da-49dbc3090d2a")
+  else()
+    set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "aa1f7df0-828a-4fcd-9afc-2dc80491aca7")
+  endif()
+  set(CMAKE_EXPERIMENTAL_CXX_MODULE_DYNDEP 1)
 else()
-  set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "aa1f7df0-828a-4fcd-9afc-2dc80491aca7")
+  cmake_policy(VERSION 3.28)
 endif()
-set(CMAKE_EXPERIMENTAL_CXX_MODULE_DYNDEP 1)
 
 # Default to C++ extensions being off. Libc++'s modules support have trouble
 # with extensions right now.
@@ -74,9 +78,12 @@ target_compile_options(std.compat
     -nostdinc++
     -Wno-reserved-module-identifier
     -Wno-reserved-user-defined-literal
+    -fprebuilt-module-path=${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/std.dir/
     @LIBCXX_COMPILE_FLAGS@
 )
 set_target_properties(std.compat
   PROPERTIES
     OUTPUT_NAME   "c++std.compat"
 )
+link_libraries(std.compat std)
+add_dependencies(std.compat std)

libcxx/modules/std.compat.cppm.in

@@ -17,38 +17,17 @@ module;
 
 // The headers of Table 24: C++ library headers [tab:headers.cpp]
 // and the headers of Table 25: C++ headers for C library facilities [tab:headers.cpp.c]
-#include <algorithm>
-#include <any>
-#include <array>
-#if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
-#  include <atomic>
-#endif
-#if !defined(_LIBCPP_HAS_NO_THREADS)
-#  include <barrier>
-#endif
-#include <bit>
-#include <bitset>
 #include <cassert>
 #include <cctype>
 #include <cerrno>
 #include <cfenv>
 #include <cfloat>
-#include <charconv>
-#include <chrono>
 #include <cinttypes>
 #include <climits>
 #if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
 #  include <clocale>
 #endif
 #include <cmath>
-#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
-#  include <codecvt>
-#endif
-#include <compare>
-#include <complex>
-#include <concepts>
-#include <condition_variable>
-#include <coroutine>
 #include <csetjmp>
 #include <csignal>
 #include <cstdarg>
@@ -65,107 +44,6 @@ module;
 #if !defined(_LIBCPP_HAS_NO_WIDE_CHARACTERS)
 #  include <cwctype>
 #endif
-#include <deque>
-#include <exception>
-#include <execution>
-#include <expected>
-#include <filesystem>
-#include <format>
-#include <forward_list>
-#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
-#  include <fstream>
-#endif
-#include <functional>
-#if !defined(_LIBCPP_HAS_NO_THREADS)
-#  include <future>
-#endif
-#include <initializer_list>
-#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
-#  include <iomanip>
-#endif
-#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
-#  include <ios>
-#endif
-#include <iosfwd>
-#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
-#  include <iostream>
-#endif
-#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
-#  include <istream>
-#endif
-#include <iterator>
-#if !defined(_LIBCPP_HAS_NO_THREADS)
-#  include <latch>
-#endif
-#include <limits>
-#include <list>
-#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
-#  include <locale>
-#endif
-#include <map>
-#include <mdspan>
-#include <memory>
-#include <memory_resource>
-#include <mutex>
-#include <new>
-#include <numbers>
-#include <numeric>
-#include <optional>
-#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
-#  include <ostream>
-#endif
-#include <print>
-#include <queue>
-#include <random>
-#include <ranges>
-#include <ratio>
-#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
-#  include <regex>
-#endif
-#include <scoped_allocator>
-#if !defined(_LIBCPP_HAS_NO_THREADS)
-#  include <semaphore>
-#endif
-#include <set>
-#if !defined(_LIBCPP_HAS_NO_THREADS)
-#  include <shared_mutex>
-#endif
-#include <source_location>
-#include <span>
-#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
-#  include <sstream>
-#endif
-#include <stack>
-#include <stdexcept>
-#if !defined(_LIBCPP_HAS_NO_THREADS)
-#  include <stop_token>
-#endif
-#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
-#  include <streambuf>
-#endif
-#include <string>
-#include <string_view>
-#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
-#  include <strstream>
-#endif
-#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
-#  include <syncstream>
-#endif
-#include <system_error>
-#if !defined(_LIBCPP_HAS_NO_THREADS)
-#  include <thread>
-#endif
-#include <tuple>
-#include <type_traits>
-#include <typeindex>
-#include <typeinfo>
-#include <unordered_map>
-#include <unordered_set>
-#include <utility>
-#include <valarray>
-#include <variant>
-#include <vector>
-#include <version>
 
 // *** Headers not yet available ***
 #if __has_include(<debugging>)
@@ -203,6 +81,7 @@ module;
 #endif // __has_include(<text_encoding>)
 
 export module std.compat;
+export import std;
+
 
-@LIBCXX_MODULE_STD_INCLUDE_SOURCES@
 @LIBCXX_MODULE_STD_COMPAT_INCLUDE_SOURCES@

libcxx/modules/std.cppm.in

@@ -204,4 +204,5 @@ module;
 
 export module std;
 
+
 @LIBCXX_MODULE_STD_INCLUDE_SOURCES@

libcxx/utils/generate_libcxx_cppm_in.py

@@ -15,6 +15,35 @@
 
 
 def write_file(module):
+
+    # TODO REMOVE THIS HACK, WE NEED A BETTER WAY TO DETECT C HEADERS
+    Module_headers = (
+        module_headers
+        if module == "std"
+        else [
+            "cassert",
+            "cctype",
+            "cerrno",
+            "cfenv",
+            "cfloat",
+            "cinttypes",
+            "climits",
+            "clocale",
+            "cmath",
+            "csetjmp",
+            "csignal",
+            "cstdarg",
+            "cstddef",
+            "cstdint",
+            "cstdio",
+            "cstdlib",
+            "cstring",
+            "ctime",
+            "cuchar",
+            "cwchar",
+            "cwctype",
+        ]
+    )
     libcxx_module_directory = os.path.join(
         os.path.dirname(os.path.dirname(os.path.realpath(__file__))), "modules"
     )
@@ -44,7 +73,7 @@ def write_file(module):
 // and the headers of Table 25: C++ headers for C library facilities [tab:headers.cpp.c]
 """
         )
-        for header in module_headers:
+        for header in Module_headers:
             if header in header_restrictions:
                 module_cpp_in.write(
                     f"""\
@@ -69,8 +98,9 @@ def write_file(module):
         module_cpp_in.write(
             f"""
 export module {module};
+{'export import std;' if module == 'std.compat' else ''}
 
-@LIBCXX_MODULE_STD_INCLUDE_SOURCES@
+{'@LIBCXX_MODULE_STD_INCLUDE_SOURCES@' if module == 'std' else ''}
 {'@LIBCXX_MODULE_STD_COMPAT_INCLUDE_SOURCES@' if module == 'std.compat' else ''}"""
         )