From 7c4c4f1406f1b4a3d84248e87ce1786ee7a5d0f5 Mon Sep 17 00:00:00 2001
From: Andrew Gilewsky <andrew.gilewsky@gmail.com>
Date: Sun, 21 Mar 2021 18:10:57 +0300
Subject: Treat '.ixx' and '.cppm' files as C++ sources

These extensions are used by convention for C++ modules and interface
units with MSVC.
---
 Help/release/dev/cxx-module-extensions.rst | 4 ++++
 Modules/CMakeCXXCompiler.cmake.in          | 2 +-
 Source/cmMakefile.cxx                      | 2 +-
 Source/cmSourceFile.h                      | 2 +-
 Source/cmake.cxx                           | 6 +++---
 5 files changed, 10 insertions(+), 6 deletions(-)
 create mode 100644 Help/release/dev/cxx-module-extensions.rst

diff --git a/Help/release/dev/cxx-module-extensions.rst b/Help/release/dev/cxx-module-extensions.rst
new file mode 100644
index 0000000..b9d0a8a
--- /dev/null
+++ b/Help/release/dev/cxx-module-extensions.rst
@@ -0,0 +1,4 @@
+cxx-module-extensions
+---------------------
+
+* Source file extensions ``.ixx`` and ``.cppm`` are now treated as C++.
diff --git a/Modules/CMakeCXXCompiler.cmake.in b/Modules/CMakeCXXCompiler.cmake.in
index 45acfe7..d0ce77a 100644
--- a/Modules/CMakeCXXCompiler.cmake.in
+++ b/Modules/CMakeCXXCompiler.cmake.in
@@ -44,7 +44,7 @@ if(CMAKE_COMPILER_IS_MINGW)
   set(MINGW 1)
 endif()
 set(CMAKE_CXX_COMPILER_ID_RUN 1)
-set(CMAKE_CXX_SOURCE_FILE_EXTENSIONS C;M;c++;cc;cpp;cxx;m;mm;mpp;CPP)
+set(CMAKE_CXX_SOURCE_FILE_EXTENSIONS C;M;c++;cc;cpp;cxx;m;mm;mpp;CPP;ixx;cppm)
 set(CMAKE_CXX_IGNORE_EXTENSIONS inl;h;hpp;HPP;H;o;O;obj;OBJ;def;DEF;rc;RC)
 
 foreach (lang C OBJC OBJCXX)
diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index e156625..40a67a3 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -1222,7 +1222,7 @@ void cmMakefile::AddCustomCommandOldStyle(
 
   // Each output must get its own copy of this rule.
   cmsys::RegularExpression sourceFiles(
-    "\\.(C|M|c|c\\+\\+|cc|cpp|cxx|mpp|cu|m|mm|"
+    "\\.(C|M|c|c\\+\\+|cc|cpp|cxx|mpp|ixx|cppm|cu|m|mm|"
     "rc|def|r|odl|idl|hpj|bat|h|h\\+\\+|"
     "hm|hpp|hxx|in|txx|inl)$");
 
diff --git a/Source/cmSourceFile.h b/Source/cmSourceFile.h
index 76a5ded..32ed687 100644
--- a/Source/cmSourceFile.h
+++ b/Source/cmSourceFile.h
@@ -175,7 +175,7 @@ private:
 #define CM_HEADER_REGEX "\\.(h|hh|h\\+\\+|hm|hpp|hxx|in|txx|inl)$"
 
 #define CM_SOURCE_REGEX                                                       \
-  "\\.(C|F|M|c|c\\+\\+|cc|cpp|mpp|cxx|cu|f|f90|for|fpp|ftn|m|mm|"             \
+  "\\.(C|F|M|c|c\\+\\+|cc|cpp|mpp|cxx|ixx|cppm|cu|f|f90|for|fpp|ftn|m|mm|"    \
   "rc|def|r|odl|idl|hpj|bat)$"
 
 #define CM_PCH_REGEX "cmake_pch(_[^.]+)?\\.(h|hxx)$"
diff --git a/Source/cmake.cxx b/Source/cmake.cxx
index b12eeee..55a7feb 100644
--- a/Source/cmake.cxx
+++ b/Source/cmake.cxx
@@ -209,9 +209,9 @@ cmake::cmake(Role role, cmState::Mode mode)
     };
 
     // The "c" extension MUST precede the "C" extension.
-    setupExts(
-      this->CLikeSourceFileExtensions,
-      { "c", "C", "c++", "cc", "cpp", "cxx", "cu", "mpp", "m", "M", "mm" });
+    setupExts(this->CLikeSourceFileExtensions,
+              { "c", "C", "c++", "cc", "cpp", "cxx", "cu", "mpp", "m", "M",
+                "mm", "ixx", "cppm" });
     setupExts(this->HeaderFileExtensions,
               { "h", "hh", "h++", "hm", "hpp", "hxx", "in", "txx" });
     setupExts(this->CudaFileExtensions, { "cu" });
-- 
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