From 77c4d2f9a213f0c6bda0fb78238d621ecbb3676d Mon Sep 17 00:00:00 2001
From: Mikko Lehtonen <scoopr@iki.fi>
Date: Fri, 26 Jan 2024 14:01:07 +0200
Subject: Xcode: Fix PCH support with Swift & C++

Previously, when a mixed language target ends up with `Swift` as the
`LINKER_LANGUAGE`, the PCH file was not set for the target at all.

Fixes: #21224
---
 Source/cmGlobalXCodeGenerator.cxx |  3 ++-
 Tests/CMakeLists.txt              |  1 +
 Tests/SwiftMixPCH/CMain.c         |  9 +++++++++
 Tests/SwiftMixPCH/CMakeLists.txt  | 15 +++++++++++++++
 Tests/SwiftMixPCH/SwiftFunc.swift |  4 ++++
 Tests/SwiftMixPCH/pch.h           |  1 +
 6 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 Tests/SwiftMixPCH/CMain.c
 create mode 100644 Tests/SwiftMixPCH/CMakeLists.txt
 create mode 100644 Tests/SwiftMixPCH/SwiftFunc.swift
 create mode 100644 Tests/SwiftMixPCH/pch.h

diff --git a/Source/cmGlobalXCodeGenerator.cxx b/Source/cmGlobalXCodeGenerator.cxx
index c6bb3df..98d77c6 100644
--- a/Source/cmGlobalXCodeGenerator.cxx
+++ b/Source/cmGlobalXCodeGenerator.cxx
@@ -3067,7 +3067,8 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmGeneratorTarget* gtgt,
   }
 
   // Precompile Headers
-  std::string pchHeader = gtgt->GetPchHeader(configName, llang);
+  std::string pchHeader =
+    gtgt->GetPchHeader(configName, langForPreprocessorDefinitions);
   if (!pchHeader.empty()) {
     buildSettings->AddAttribute("GCC_PREFIX_HEADER",
                                 this->CreateString(pchHeader));
diff --git a/Tests/CMakeLists.txt b/Tests/CMakeLists.txt
index a1619ec..a7a456c 100644
--- a/Tests/CMakeLists.txt
+++ b/Tests/CMakeLists.txt
@@ -412,6 +412,7 @@ if(BUILD_TESTING)
     PASS_REGULAR_EXPRESSION "CMake Error at CMakeLists.txt:3 \\(add_executable\\):[ \r\n]*Cannot find source file:[ \r\n]*DoesNotExist/MissingSourceFile.c")
   if(CMake_TEST_Swift)
     ADD_TEST_MACRO(SwiftOnly SwiftOnly)
+    ADD_TEST_MACRO(SwiftMixPCH SwiftMixPCH)
     if(CMake_TEST_XCODE_SWIFT)
       ADD_TEST_MACRO(SwiftMix SwiftMix)
     endif()
diff --git a/Tests/SwiftMixPCH/CMain.c b/Tests/SwiftMixPCH/CMain.c
new file mode 100644
index 0000000..4cd78e6
--- /dev/null
+++ b/Tests/SwiftMixPCH/CMain.c
@@ -0,0 +1,9 @@
+#ifndef PCH_VALUE
+#  error "PCH_VALUE not defined"
+#endif
+
+int main(void)
+{
+  const int value = PCH_VALUE;
+  return value == 42 ? 0 : 1;
+}
diff --git a/Tests/SwiftMixPCH/CMakeLists.txt b/Tests/SwiftMixPCH/CMakeLists.txt
new file mode 100644
index 0000000..d5704f1
--- /dev/null
+++ b/Tests/SwiftMixPCH/CMakeLists.txt
@@ -0,0 +1,15 @@
+cmake_minimum_required(VERSION 3.15)
+if(POLICY CMP0157)
+  cmake_policy(SET CMP0157 NEW)
+endif()
+
+project(SwiftMixPCH C Swift)
+
+# Swift on Windows only provides a release runtime.
+set(CMAKE_MSVC_RUNTIME_LIBRARY MultiThreadedDLL)
+
+add_executable(SwiftMixPCH CMain.c SwiftFunc.swift)
+target_precompile_headers(SwiftMixPCH PRIVATE pch.h)
+
+# We don't want swift to emit main()
+target_compile_options(SwiftMixPCH PRIVATE "$<$<COMPILE_LANGUAGE:Swift>:-parse-as-library>")
diff --git a/Tests/SwiftMixPCH/SwiftFunc.swift b/Tests/SwiftMixPCH/SwiftFunc.swift
new file mode 100644
index 0000000..d49c36f
--- /dev/null
+++ b/Tests/SwiftMixPCH/SwiftFunc.swift
@@ -0,0 +1,4 @@
+
+func SwiftFunc() -> Int32 {
+    return 0;
+}
diff --git a/Tests/SwiftMixPCH/pch.h b/Tests/SwiftMixPCH/pch.h
new file mode 100644
index 0000000..6de0669
--- /dev/null
+++ b/Tests/SwiftMixPCH/pch.h
@@ -0,0 +1 @@
+#define PCH_VALUE 42
-- 
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