import std

Signed-off-by: Slendi <slendi@socopon.com>

CMakeLists.txt

@@ -1,9 +1,12 @@
-cmake_minimum_required(VERSION 3.30)
+cmake_minimum_required(VERSION 3.31)
 
-project(LunarWM C CXX)
+set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD "0e5b6991-d74f-4b3d-a41c-cf096e0b2508")
+
+project(LunarWM LANGUAGES C CXX)
 
 set(CMAKE_CXX_STANDARD 23)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_MODULE_STD 1)
 
 find_package(PkgConfig)
 

flake.nix

@@ -23,11 +23,17 @@
       in
       {
         devShells.default = pkgs.mkShell.override { stdenv = pkgs.llvmPackages_20.libcxxStdenv; } {
+          hardeningDisable = [ "fortify" ];
+
           packages = with pkgs; [
+            (pkgs.callPackage ./nix/cmake-importstd-patched/package.nix {
+              libcxx = pkgs.llvmPackages_20.libcxx;
+            })
+
             pkg-config
             cmake
             ninja
-            clang-tools
+            (pkgs.llvmPackages_20.clang-tools.override { enableLibcxx = true; })
             lldb
 
             # For wlroots

nix/cmake-importstd-patched/package.nix

@@ -0,0 +1,37 @@
+# Dummy cmake package for replacing the ImportStd module.
+# Symlink existing derivation to avoid rebuilding package from source.
+# I.e. rather than using overlay or override(Attr) to add patch.
+#
+# Note this is actually a clang/llvm issue (`-print-file-name` flag not working),
+# but it is much simpler to just patch the cmake module itself. Maybe fixed in llvm 19.1.7
+#
+# See relevant issues:
+# 1. https://github.com/NixOS/nixpkgs/issues/370217
+# 2. https://gitlab.kitware.com/cmake/cmake/-/issues/25965#note_1523575
+{
+  lib,
+  cmake,
+  libcxx,
+  symlinkJoin,
+}:
+let
+  cmake-ver = "${lib.versions.majorMinor cmake.version}";
+  module-path = "share/cmake-${cmake-ver}/Modules/Compiler/Clang-CXX-CXXImportStd.cmake";
+in
+symlinkJoin {
+  name = "${cmake.name}-importstd-module-patched";
+  paths = [ cmake ];
+  postBuild = ''
+    # copy binaries to avoid using original derivation
+    for link in $(find $out/bin/ -type l); do
+      cp --remove-destination $(readlink $link) $out/bin/
+    done;
+
+    # replace symlink to existing module with copy for editing
+    cp --remove-destination $(readlink $out/${module-path}) $out/${module-path}
+
+    # replace "libc++.modules.json" with full path
+    # to libc++ module json in new copied module file
+    sed -i 's#libc++.modules.json#${libcxx}/lib/libc++.modules.json#' $out/${module-path}
+  '';
+}

src/LunarWM.cppm

@@ -1,8 +1,6 @@
 module;
 
-#include <memory>
 #include <poll.h>
-#include <print>
 
 #include <EGL/egl.h>
 #include <EGL/eglext.h>
@@ -11,6 +9,8 @@ module;
 
 export module LunarWM.LunarWM;
 
+import std;
+
 import LunarWM.wl.Subcompositor;
 import LunarWM.wl.Shm;
 

src/Math.cppm

@@ -1,9 +1,6 @@
 module;
 
-#include <cmath>
-#include <stdexcept>
-#include <type_traits>
-#include <vector>
+import std;
 
 export module LunarWM.Math;
 

src/main.cpp

@@ -1,5 +1,6 @@
 #include <csignal>
-#include <memory>
+
+import std;
 
 import LunarWM.LunarWM;
 

src/wl/Region.cppm

@@ -1,14 +1,13 @@
 module;
 
-#include <stdexcept>
-#include <vector>
-
 #include <wayland-server.h>
 
 #include "util.h"
 
 export module LunarWM.wl.Region;
 
+import std;
+
 import LunarWM.Math;
 
 namespace LunarWM {

src/wl/Shm.cppm

@@ -2,18 +2,17 @@ module;
 
 #include <cerrno>
 #include <cstring>
-#include <stdexcept>
-
-#include <wayland-server.h>
-
-#include <GLES2/gl2.h>
-
 #include <fcntl.h>
 #include <sys/mman.h>
 #include <unistd.h>
 
+#include <GLES2/gl2.h>
+#include <wayland-server.h>
+
 export module LunarWM.wl.Shm;
 
+import std;
+
 namespace LunarWM {
 
 namespace wl {

src/wl/Subsurface.cppm

@@ -2,12 +2,12 @@ module;
 
 #include "util.h"
 
-#include <stdexcept>
-
 #include <wayland-server.h>
 
 export module LunarWM.wl.Subsurface;
 
+import std;
+
 namespace LunarWM {
 
 namespace wl {