OS X: Always generate -isysroot if any SDK is in use

Drop the last use of CMAKE_OSX_SYSROOT_DEFAULT.  Replace internal
platform variable CMAKE_${lang}_HAS_ISYSROOT with a more general
CMAKE_${lang}_SYSROOT_FLAG variable.  If the -isysroot flag exists and
CMAKE_OSX_SYSROOT points to an SDK (not "/") then always add it to
compiler command lines.  This is already done in the Xcode IDE.

Modules/CMakeCCompiler.cmake.in

@@ -45,7 +45,7 @@ if(CMAKE_C_LIBRARY_ARCHITECTURE)
   set(CMAKE_LIBRARY_ARCHITECTURE "@CMAKE_C_LIBRARY_ARCHITECTURE@")
 endif()
 
-set(CMAKE_C_HAS_ISYSROOT "@CMAKE_C_HAS_ISYSROOT@")
+@CMAKE_C_SYSROOT_FLAG_CODE@
 @CMAKE_C_OSX_DEPLOYMENT_TARGET_FLAG_CODE@
 
 set(CMAKE_C_IMPLICIT_LINK_LIBRARIES "@CMAKE_C_IMPLICIT_LINK_LIBRARIES@")

Modules/CMakeCXXCompiler.cmake.in

@@ -46,7 +46,7 @@ if(CMAKE_CXX_LIBRARY_ARCHITECTURE)
   set(CMAKE_LIBRARY_ARCHITECTURE "@CMAKE_CXX_LIBRARY_ARCHITECTURE@")
 endif()
 
-set(CMAKE_CXX_HAS_ISYSROOT "@CMAKE_CXX_HAS_ISYSROOT@")
+@CMAKE_CXX_SYSROOT_FLAG_CODE@
 @CMAKE_CXX_OSX_DEPLOYMENT_TARGET_FLAG_CODE@
 
 set(CMAKE_CXX_IMPLICIT_LINK_LIBRARIES "@CMAKE_CXX_IMPLICIT_LINK_LIBRARIES@")

Modules/CMakeFindPackageMode.cmake

@@ -53,8 +53,8 @@ include(CMakeDetermineSystem)
 
 # short-cut some tests on Darwin, see Darwin-GNU.cmake:
 if("${CMAKE_SYSTEM_NAME}" MATCHES Darwin  AND  "${COMPILER_ID}" MATCHES GNU)
-  set(${CMAKE_${LANGUAGE}_HAS_ISYSROOT} 0 )
-  set(CMAKE_${lang}_OSX_DEPLOYMENT_TARGET_FLAG "")
+  set(CMAKE_${LANGUAGE}_SYSROOT_FLAG "")
+  set(CMAKE_${LANGUAGE}_OSX_DEPLOYMENT_TARGET_FLAG "")
 endif()
 
 # Also load the system specific file, which sets up e.g. the search paths.

Modules/Platform/Darwin-Clang.cmake

@@ -21,6 +21,6 @@ set(__DARWIN_COMPILER_CLANG 1)
 macro(__darwin_compiler_clang lang)
   set(CMAKE_SHARED_LIBRARY_CREATE_${lang}_FLAGS "-dynamiclib -Wl,-headerpad_max_install_names")
   set(CMAKE_SHARED_MODULE_CREATE_${lang}_FLAGS "-bundle -Wl,-headerpad_max_install_names")
+  set(CMAKE_${lang}_SYSROOT_FLAG "-isysroot")
   set(CMAKE_${lang}_OSX_DEPLOYMENT_TARGET_FLAG "-mmacosx-version-min=")
-  set(CMAKE_${lang}_HAS_ISYSROOT 1)
 endmacro()

Modules/Platform/Darwin-GNU-C.cmake

@@ -1,4 +1,4 @@
 include(Platform/Darwin-GNU)
 __darwin_compiler_gnu(C)
-cmake_gnu_has_isysroot(C)
+cmake_gnu_set_sysroot_flag(C)
 cmake_gnu_set_osx_deployment_target_flag(C)

Modules/Platform/Darwin-GNU-CXX.cmake

@@ -1,4 +1,4 @@
 include(Platform/Darwin-GNU)
 __darwin_compiler_gnu(CXX)
-cmake_gnu_has_isysroot(CXX)
+cmake_gnu_set_sysroot_flag(CXX)
 cmake_gnu_set_osx_deployment_target_flag(CXX)

Modules/Platform/Darwin-GNU.cmake

@@ -24,8 +24,8 @@ macro(__darwin_compiler_gnu lang)
   set(CMAKE_SHARED_MODULE_CREATE_${lang}_FLAGS "-bundle -Wl,-headerpad_max_install_names")
 endmacro()
 
-macro(cmake_gnu_has_isysroot lang)
-  if("x${CMAKE_${lang}_HAS_ISYSROOT}" STREQUAL "x")
+macro(cmake_gnu_set_sysroot_flag lang)
+  if(NOT DEFINED CMAKE_${lang}_SYSROOT_FLAG)
     set(_doc "${lang} compiler has -isysroot")
     message(STATUS "Checking whether ${_doc}")
     execute_process(
@@ -35,11 +35,12 @@ macro(cmake_gnu_has_isysroot lang)
       )
     if("${_gcc_help}" MATCHES "isysroot")
       message(STATUS "Checking whether ${_doc} - yes")
-      set(CMAKE_${lang}_HAS_ISYSROOT 1)
+      set(CMAKE_${lang}_SYSROOT_FLAG "-isysroot")
     else()
       message(STATUS "Checking whether ${_doc} - no")
-      set(CMAKE_${lang}_HAS_ISYSROOT 0)
+      set(CMAKE_${lang}_SYSROOT_FLAG "")
     endif()
+    set(CMAKE_${lang}_SYSROOT_FLAG_CODE "set(CMAKE_${lang}_SYSROOT_FLAG \"${CMAKE_${lang}_SYSROOT_FLAG}\")")
   endif()
 endmacro()
 

Source/cmLocalGenerator.cxx

@@ -1792,46 +1792,34 @@ void cmLocalGenerator::AddArchitectureFlags(std::string& flags,
     {
     std::vector<std::string> archs;
     target->GetAppleArchs(config, archs);
-    const char* sysroot =
-      this->Makefile->GetDefinition("CMAKE_OSX_SYSROOT");
-    const char* sysrootDefault =
-      this->Makefile->GetDefinition("CMAKE_OSX_SYSROOT_DEFAULT");
+    const char* sysroot = this->Makefile->GetDefinition("CMAKE_OSX_SYSROOT");
+    if(sysroot && sysroot[0] == '/' && !sysroot[1])
+      { sysroot = 0; }
+    std::string sysrootFlagVar =
+      std::string("CMAKE_") + lang + "_SYSROOT_FLAG";
+    const char* sysrootFlag =
+      this->Makefile->GetDefinition(sysrootFlagVar.c_str());
     const char* deploymentTarget =
       this->Makefile->GetDefinition("CMAKE_OSX_DEPLOYMENT_TARGET");
-    std::string isysrootVar = std::string("CMAKE_") + lang + "_HAS_ISYSROOT";
-    bool hasIsysroot = this->Makefile->IsOn(isysrootVar.c_str());
     std::string deploymentTargetFlagVar =
       std::string("CMAKE_") + lang + "_OSX_DEPLOYMENT_TARGET_FLAG";
     const char* deploymentTargetFlag =
       this->Makefile->GetDefinition(deploymentTargetFlagVar.c_str());
-    bool flagsUsed = false;
-    if(!archs.empty() && sysroot && lang && (lang[0] =='C' || lang[0] == 'F'))
-      {
-      // if there is more than one arch add the -arch and
-      // -isysroot flags, or if there is one arch flag, but
-      // it is not the default -arch flag for the system, then
-      // add it.  Otherwize do not add -arch and -isysroot
-      if(archs[0] != "")
+    if(!archs.empty() && lang && (lang[0] =='C' || lang[0] == 'F'))
+      {
+      for(std::vector<std::string>::iterator i = archs.begin();
+          i != archs.end(); ++i)
         {
-        for( std::vector<std::string>::iterator i = archs.begin();
-             i != archs.end(); ++i)
-          {
-          flags += " -arch ";
-          flags += *i;
-          }
-        if(hasIsysroot)
-          {
-          flags += " -isysroot ";
-          flags += sysroot;
-          }
-        flagsUsed = true;
+        flags += " -arch ";
+        flags += *i;
         }
       }
 
-    if(!flagsUsed && sysroot && sysrootDefault &&
-       strcmp(sysroot, sysrootDefault) != 0 && hasIsysroot)
+    if(sysrootFlag && *sysrootFlag && sysroot && *sysroot)
       {
-      flags += " -isysroot ";
+      flags += " ";
+      flags += sysrootFlag;
+      flags += " ";
       flags += sysroot;
       }