Build object library targets in Xcode

Treat OBJECT libraries as STATIC libraries. The Xcode project file
format provides no way to avoid running the libtool so hide the
resulting .a away next to the object files as it should never be
referenced.  The object files will be left behind for reference by other
targets later.

Source/cmGlobalXCodeGenerator.cxx

@@ -409,6 +409,8 @@ cmGlobalXCodeGenerator::AddExtraTargets(cmLocalGenerator* root,
       // this will make sure that when the next target is built
       // things are up-to-date
       if((target.GetType() == cmTarget::EXECUTABLE ||
+// Nope - no post-build for OBJECT_LIRBRARY
+//          target.GetType() == cmTarget::OBJECT_LIBRARY ||
           target.GetType() == cmTarget::STATIC_LIBRARY ||
           target.GetType() == cmTarget::SHARED_LIBRARY ||
           target.GetType() == cmTarget::MODULE_LIBRARY))
@@ -1548,7 +1550,8 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmTarget& target,
   std::string defFlags;
   bool shared = ((target.GetType() == cmTarget::SHARED_LIBRARY) ||
                  (target.GetType() == cmTarget::MODULE_LIBRARY));
-  bool binary = ((target.GetType() == cmTarget::STATIC_LIBRARY) ||
+  bool binary = ((target.GetType() == cmTarget::OBJECT_LIBRARY) ||
+                 (target.GetType() == cmTarget::STATIC_LIBRARY) ||
                  (target.GetType() == cmTarget::EXECUTABLE) ||
                  shared);
 
@@ -1635,7 +1638,8 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmTarget& target,
     }
 
   const char* linkFlagsProp = "LINK_FLAGS";
-  if(target.GetType() == cmTarget::STATIC_LIBRARY)
+  if(target.GetType() == cmTarget::OBJECT_LIBRARY ||
+     target.GetType() == cmTarget::STATIC_LIBRARY)
     {
     linkFlagsProp = "STATIC_LIBRARY_FLAGS";
     }
@@ -1689,11 +1693,8 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmTarget& target,
   std::string pnprefix;
   std::string pnbase;
   std::string pnsuffix;
-  target.GetFullNameComponents(pnprefix, pnbase, pnsuffix, configName);
 
-  // Store the product name for all target types.
+  target.GetFullNameComponents(pnprefix, pnbase, pnsuffix, configName);
-  buildSettings->AddAttribute("PRODUCT_NAME",
-                              this->CreateString(pnbase.c_str()));
 
   // Set attributes to specify the proper name for the target.
   std::string pndir = this->CurrentMakefile->GetCurrentOutputDirectory();
@@ -1717,17 +1718,44 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmTarget& target,
                                   this->CreateString(pndir.c_str()));
       pndir = target.GetDirectory(configName);
       }
+
     buildSettings->AddAttribute("EXECUTABLE_PREFIX",
                                 this->CreateString(pnprefix.c_str()));
     buildSettings->AddAttribute("EXECUTABLE_SUFFIX",
                                 this->CreateString(pnsuffix.c_str()));
     }
+  else if(target.GetType() == cmTarget::OBJECT_LIBRARY)
+    {
+    pnprefix = "lib";
+    pnbase = target.GetName();
+    pnsuffix = ".a";
+
+    if(this->XcodeVersion >= 21)
+      {
+      std::string pncdir = this->GetObjectsNormalDirectory(
+        this->CurrentProject, configName, &target);
+      buildSettings->AddAttribute("CONFIGURATION_BUILD_DIR",
+                                  this->CreateString(pncdir.c_str()));
+      }
+    else
+      {
+      buildSettings->AddAttribute("OBJROOT",
+                                  this->CreateString(pndir.c_str()));
+      pndir = this->GetObjectsNormalDirectory(
+        this->CurrentProject, configName, &target);
+      }
+    }
+
+  // Store the product name for all target types.
+  buildSettings->AddAttribute("PRODUCT_NAME",
+                              this->CreateString(pnbase.c_str()));
   buildSettings->AddAttribute("SYMROOT",
                               this->CreateString(pndir.c_str()));
 
   // Handle settings for each target type.
   switch(target.GetType())
     {
+    case cmTarget::OBJECT_LIBRARY:
     case cmTarget::STATIC_LIBRARY:
     {
     buildSettings->AddAttribute("LIBRARY_STYLE",
@@ -2231,6 +2259,7 @@ const char* cmGlobalXCodeGenerator::GetTargetFileType(cmTarget& cmtarget)
 {
   switch(cmtarget.GetType())
     {
+    case cmTarget::OBJECT_LIBRARY:
     case cmTarget::STATIC_LIBRARY:
       return "archive.ar";
     case cmTarget::MODULE_LIBRARY:
@@ -2254,6 +2283,7 @@ const char* cmGlobalXCodeGenerator::GetTargetProductType(cmTarget& cmtarget)
 {
   switch(cmtarget.GetType())
     {
+    case cmTarget::OBJECT_LIBRARY:
     case cmTarget::STATIC_LIBRARY:
       return "com.apple.product-type.library.static";
     case cmTarget::MODULE_LIBRARY:
@@ -2311,7 +2341,17 @@ cmGlobalXCodeGenerator::CreateXCodeTarget(cmTarget& cmtarget,
     {
     fileRef->AddAttribute("explicitFileType", this->CreateString(fileType));
     }
-  std::string fullName = cmtarget.GetFullName(defConfig.c_str());
+  std::string fullName;
+  if(cmtarget.GetType() == cmTarget::OBJECT_LIBRARY)
+    {
+    fullName = "lib";
+    fullName += cmtarget.GetName();
+    fullName += ".a";
+    }
+  else
+    {
+    fullName = cmtarget.GetFullName(defConfig.c_str());
+    }
   fileRef->AddAttribute("path", this->CreateString(fullName.c_str()));
   fileRef->AddAttribute("refType", this->CreateString("0"));
   fileRef->AddAttribute("sourceTree",
@@ -2516,7 +2556,8 @@ void cmGlobalXCodeGenerator
     }
 
   // Skip link information for static libraries.
-  if(cmtarget->GetType() == cmTarget::STATIC_LIBRARY)
+  if(cmtarget->GetType() == cmTarget::OBJECT_LIBRARY ||
+     cmtarget->GetType() == cmTarget::STATIC_LIBRARY)
     {
     return;
     }
@@ -2664,6 +2705,7 @@ void cmGlobalXCodeGenerator::CreateGroups(cmLocalGenerator* root,
 
       std::vector<cmSourceFile*>  classes = cmtarget.GetSourceFiles();
 
+      // Put cmSourceFile instances in proper groups:
       for(std::vector<cmSourceFile*>::const_iterator s = classes.begin();
           s != classes.end(); s++)
         {
@@ -3197,6 +3239,8 @@ cmGlobalXCodeGenerator::CreateXCodeDependHackTarget(
       cmTarget* t =target->GetTarget();
 
       if(t->GetType() == cmTarget::EXECUTABLE ||
+// Nope - no post-build for OBJECT_LIRBRARY
+//         t->GetType() == cmTarget::OBJECT_LIBRARY ||
          t->GetType() == cmTarget::STATIC_LIBRARY ||
          t->GetType() == cmTarget::SHARED_LIBRARY ||
          t->GetType() == cmTarget::MODULE_LIBRARY)