Xcode: Obey SYSTEM keyword for includes (#15687)

CMake used to put all header search paths into HEADER_SEARCH_PATHS
attribute. Unfortunately this attribute does not support to declare
a search path as a system include.

As a hack one could add a -isystem /path to the cflags but then include
ordering is not deterministic. A better approach was chosen with this
patch by not filling HEADER_SEARCH_PATHS at all and to populate
the C, C++, and Fortran flags directly. The include paths used by
Xcode should be now identical to the ones used by Unix Makefiles and
Ninja generator.

Modules/CMakeSwiftInformation.cmake

@@ -13,6 +13,7 @@
 #  License text for the above reference.)
 
 set(CMAKE_Swift_OUTPUT_EXTENSION .o)
+set(CMAKE_INCLUDE_FLAG_Swift "-I")
 
 # Load compiler-specific information.
 if(CMAKE_Swift_COMPILER_ID)

Source/cmGlobalXCodeGenerator.cxx

@@ -1907,23 +1907,40 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmGeneratorTarget* gtgt,
 
   BuildObjectListOrString dirs(this, this->XcodeVersion >= 30);
   BuildObjectListOrString fdirs(this, this->XcodeVersion >= 30);
-  std::vector<std::string> includes;
-  this->CurrentLocalGenerator->GetIncludeDirectories(includes, gtgt, "C",
-                                                     configName);
   std::set<std::string> emitted;
   emitted.insert("/System/Library/Frameworks");
-  for (std::vector<std::string>::iterator i = includes.begin();
-       i != includes.end(); ++i) {
-    if (this->NameResolvesToFramework(i->c_str())) {
-      std::string frameworkDir = *i;
-      frameworkDir += "/../";
-      frameworkDir = cmSystemTools::CollapseFullPath(frameworkDir);
-      if (emitted.insert(frameworkDir).second) {
-        fdirs.Add(this->XCodeEscapePath(frameworkDir));
+
+  if (this->XcodeVersion < 60) {
+    std::vector<std::string> includes;
+    this->CurrentLocalGenerator->GetIncludeDirectories(includes, gtgt, "C",
+                                                       configName);
+    for (std::vector<std::string>::iterator i = includes.begin();
+         i != includes.end(); ++i) {
+      if (this->NameResolvesToFramework(i->c_str())) {
+        std::string frameworkDir = *i;
+        frameworkDir += "/../";
+        frameworkDir = cmSystemTools::CollapseFullPath(frameworkDir);
+        if (emitted.insert(frameworkDir).second) {
+          fdirs.Add(this->XCodeEscapePath(frameworkDir));
+        }
+      } else {
+        std::string incpath = this->XCodeEscapePath(*i);
+        dirs.Add(incpath);
+      }
+    }
+  } else {
+    for (std::set<std::string>::iterator li = languages.begin();
+         li != languages.end(); ++li) {
+      std::vector<std::string> includes;
+      this->CurrentLocalGenerator->GetIncludeDirectories(includes, gtgt, *li,
+                                                         configName);
+      std::string includeFlags = this->CurrentLocalGenerator->GetIncludeFlags(
+        includes, gtgt, *li, true, false, configName);
+
+      std::string& flags = cflags[*li];
+      if (!includeFlags.empty()) {
+        flags += " " + includeFlags;
       }
-    } else {
-      std::string incpath = this->XCodeEscapePath(*i);
-      dirs.Add(incpath);
     }
   }
   // Add framework search paths needed for linking.
@@ -2008,6 +2025,9 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmGeneratorTarget* gtgt,
                                   this->CreateString(flags));
     } else if (*li == "C") {
       buildSettings->AddAttribute("OTHER_CFLAGS", this->CreateString(flags));
+    } else if (*li == "Swift") {
+      buildSettings->AddAttribute("OTHER_SWIFT_FLAGS",
+                                  this->CreateString(flags));
     }
   }
 

Tests/IncludeDirectories/CMakeLists.txt

@@ -3,7 +3,9 @@ project(IncludeDirectories)
 
 if (((CMAKE_C_COMPILER_ID STREQUAL GNU AND CMAKE_C_COMPILER_VERSION VERSION_GREATER 4.4)
     OR CMAKE_C_COMPILER_ID STREQUAL Clang OR CMAKE_C_COMPILER_ID STREQUAL AppleClang)
-    AND (CMAKE_GENERATOR STREQUAL "Unix Makefiles" OR CMAKE_GENERATOR STREQUAL "Ninja"))
+    AND (CMAKE_GENERATOR STREQUAL "Unix Makefiles"
+      OR CMAKE_GENERATOR STREQUAL "Ninja"
+      OR (CMAKE_GENERATOR STREQUAL "Xcode" AND NOT XCODE_VERSION VERSION_LESS 6.0)))
   include(CheckCXXCompilerFlag)
   check_cxx_compiler_flag(-Wunused-variable run_sys_includes_test)
   if(run_sys_includes_test)

Tests/IncludeDirectories/SystemIncludeDirectories/CMakeLists.txt

@@ -15,10 +15,17 @@ target_include_directories(upstream SYSTEM PUBLIC
 )
 
 add_library(config_specific INTERFACE)
-set(testConfig ${CMAKE_BUILD_TYPE})
-target_include_directories(config_specific SYSTEM INTERFACE
-  "$<$<CONFIG:${testConfig}>:${CMAKE_CURRENT_SOURCE_DIR}/config_specific>"
-)
+if(CMAKE_GENERATOR STREQUAL "Xcode")
+  # CMAKE_BUILD_TYPE does not work here for multi-config generators
+  target_include_directories(config_specific SYSTEM INTERFACE
+    "${CMAKE_CURRENT_SOURCE_DIR}/config_specific"
+  )
+else()
+  set(testConfig ${CMAKE_BUILD_TYPE})
+  target_include_directories(config_specific SYSTEM INTERFACE
+    "$<$<CONFIG:${testConfig}>:${CMAKE_CURRENT_SOURCE_DIR}/config_specific>"
+  )
+endif()
 
 add_library(consumer consumer.cpp)
 target_link_libraries(consumer upstream config_specific)