ObjC: Add OBJC/OBJCXX flags to Xcode projects

Fixes: #19936

Source/cmGlobalXCodeGenerator.cxx

@@ -2220,7 +2220,7 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmGeneratorTarget* gtgt,
 
   // extract C++ stdlib
   for (auto const& language : languages) {
-    if (language != "CXX") {
+    if (language != "CXX" && language != "OBJCXX") {
       continue;
     }
     std::string& flags = cflags[language];
@@ -2229,8 +2229,11 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmGeneratorTarget* gtgt,
       this->ExtractFlagRegex("(^| )(-stdlib=[^ ]+)( |$)", 2, flags);
     if (stdlib.size() > 8) {
       const auto cxxLibrary = stdlib.substr(8);
-      buildSettings->AddAttribute("CLANG_CXX_LIBRARY",
-                                  this->CreateString(cxxLibrary));
+      if (language == "CXX" ||
+          !buildSettings->GetObject("CLANG_CXX_LIBRARY")) {
+        buildSettings->AddAttribute("CLANG_CXX_LIBRARY",
+                                    this->CreateString(cxxLibrary));
+      }
     }
   }
 
@@ -2244,16 +2247,22 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmGeneratorTarget* gtgt,
                               this->CreateString("NO"));
   buildSettings->AddAttribute("GCC_INLINES_ARE_PRIVATE_EXTERN",
                               this->CreateString("NO"));
+
   for (auto const& language : languages) {
     std::string flags = cflags[language] + " " + defFlags;
-    if (language == "CXX") {
-      buildSettings->AddAttribute("OTHER_CPLUSPLUSFLAGS",
-                                  this->CreateString(flags));
+    if (language == "CXX" || language == "OBJCXX") {
+      if (language == "CXX" ||
+          !buildSettings->GetObject("OTHER_CPLUSPLUSFLAGS")) {
+        buildSettings->AddAttribute("OTHER_CPLUSPLUSFLAGS",
+                                    this->CreateString(flags));
+      }
     } else if (language == "Fortran") {
       buildSettings->AddAttribute("IFORT_OTHER_FLAGS",
                                   this->CreateString(flags));
-    } else if (language == "C") {
-      buildSettings->AddAttribute("OTHER_CFLAGS", this->CreateString(flags));
+    } else if (language == "C" || language == "OBJC") {
+      if (language == "C" || !buildSettings->GetObject("OTHER_CFLAGS")) {
+        buildSettings->AddAttribute("OTHER_CFLAGS", this->CreateString(flags));
+      }
     } else if (language == "Swift") {
       buildSettings->AddAttribute("OTHER_SWIFT_FLAGS",
                                   this->CreateString(flags));

Tests/RunCMake/XcodeProject/RunCMakeTest.cmake

@@ -54,6 +54,20 @@ endfunction()
 
 XcodeDependOnZeroCheck()
 
+function(XcodeObjcxxFlags testName)
+  set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/${testName}-build)
+  set(RunCMake_TEST_NO_CLEAN 1)
+
+  file(REMOVE_RECURSE "${RunCMake_TEST_BINARY_DIR}")
+  file(MAKE_DIRECTORY "${RunCMake_TEST_BINARY_DIR}")
+
+  run_cmake(${testName})
+  run_cmake_command(${testName}-build ${CMAKE_COMMAND} --build .)
+endfunction()
+
+XcodeObjcxxFlags(XcodeObjcFlags)
+XcodeObjcxxFlags(XcodeObjcxxFlags)
+
 # Isolate device tests from host architecture selection.
 unset(ENV{CMAKE_OSX_ARCHITECTURES})
 

Tests/RunCMake/XcodeProject/XcodeObjcFlags.cmake

+cmake_minimum_required(VERSION 3.15)
+project(objctest LANGUAGES C OBJC)
+
+include(CheckOBJCCompilerFlag)
+check_objc_compiler_flag(-fobjc-arc HAVE_OBJC_ARC)
+
+if(HAVE_OBJC_ARC)
+  add_compile_options(-fobjc-arc)
+  add_compile_definitions(HAVE_OBJC_ARC)
+endif()
+
+add_library(myfuncs STATIC myfuncs.m)

Tests/RunCMake/XcodeProject/XcodeObjcxxFlags.cmake

+cmake_minimum_required(VERSION 3.15)
+project(objcxxtest LANGUAGES CXX OBJCXX)
+
+include(CheckOBJCXXCompilerFlag)
+check_objcxx_compiler_flag(-fobjc-arc HAVE_OBJC_ARC)
+
+if(HAVE_OBJC_ARC)
+  add_compile_options(-fobjc-arc)
+  add_compile_definitions(HAVE_OBJC_ARC)
+endif()
+
+add_library(myfuncs STATIC myfuncs.mm)

Tests/RunCMake/XcodeProject/myfuncs.m

+#if defined(HAVE_OBJC_ARC) && ! __has_feature(objc_arc)
+#error THIS CODE MUST BE COMPILED WITH ARC ENABLED!
+#endif

Tests/RunCMake/XcodeProject/myfuncs.mm

+#if defined(HAVE_OBJC_ARC) && ! __has_feature(objc_arc)
+#error THIS CODE MUST BE COMPILED WITH ARC ENABLED!
+#endif