Xcode: Use "Link Binary With Libraries" build phase when possible

Try linking all target linked libraries through frameworks build phase
instead of linker flags, thus letting Xcode manage build product paths
correctly.  Prevent adding duplicate entries to "Link Binary With
Libraries" build phase.

Add check for configuration-dependent linking - in case the library is
not present in all configurations revert back to linker flags which are
per-configuration.

This does change the order of libraries linked, but that does not seem
to matter for Apple linkers invoked by Xcode, even for static libraries.
The linker will go back and re-consider a static library from earlier
on the link line when more symbols from its objects are needed.

Fixes: #14185

Source/cmGlobalXCodeGenerator.cxx

@@ -1354,22 +1354,20 @@ bool cmGlobalXCodeGenerator::CreateXCodeTarget(
     }
   }
 
-  // create framework build phase
+  // always create framework build phase
   cmXCodeObject* frameworkBuildPhase = nullptr;
-  if (!externalObjFiles.empty()) {
-    frameworkBuildPhase =
-      this->CreateObject(cmXCodeObject::PBXFrameworksBuildPhase);
-    frameworkBuildPhase->SetComment("Frameworks");
-    frameworkBuildPhase->AddAttribute("buildActionMask",
-                                      this->CreateString("2147483647"));
-    buildFiles = this->CreateObject(cmXCodeObject::OBJECT_LIST);
-    frameworkBuildPhase->AddAttribute("files", buildFiles);
-    for (auto& externalObjFile : externalObjFiles) {
-      buildFiles->AddObject(externalObjFile);
-    }
-    frameworkBuildPhase->AddAttribute("runOnlyForDeploymentPostprocessing",
-                                      this->CreateString("0"));
-  }
+  frameworkBuildPhase =
+    this->CreateObject(cmXCodeObject::PBXFrameworksBuildPhase);
+  frameworkBuildPhase->SetComment("Frameworks");
+  frameworkBuildPhase->AddAttribute("buildActionMask",
+                                    this->CreateString("2147483647"));
+  buildFiles = this->CreateObject(cmXCodeObject::OBJECT_LIST);
+  frameworkBuildPhase->AddAttribute("files", buildFiles);
+  for (auto& externalObjFile : externalObjFiles) {
+    buildFiles->AddObject(externalObjFile);
+  }
+  frameworkBuildPhase->AddAttribute("runOnlyForDeploymentPostprocessing",
+                                    this->CreateString("0"));
 
   // create list of build phases and create the Xcode target
   cmXCodeObject* buildPhases = this->CreateObject(cmXCodeObject::OBJECT_LIST);
@@ -2769,6 +2767,156 @@ void cmGlobalXCodeGenerator::AddDependAndLinkInformation(cmXCodeObject* target)
     }
   }
 
+  // Separate libraries into ones that can be linked using "Link Binary With
+  // Libraries" build phase and the ones that can't. Only targets that build
+  // Apple bundles (.app, .framework, .bundle) can use this feature and only
+  // targets that represent actual libraries (static or dynamic, local or
+  // imported) not objects and not executables will be used. These are
+  // limitations imposed by CMake use-cases - otherwise a lot of things break.
+  // The rest will be linked using linker flags (OTHER_LDFLAGS setting in Xcode
+  // project).
+  std::map<std::string, std::vector<cmComputeLinkInformation::Item const*>>
+    configItemMap;
+  auto addToLinkerArguments =
+    [&configItemMap](const std::string& configName,
+                     cmComputeLinkInformation::Item const* libItemPtr) {
+      auto& linkVector = configItemMap[configName];
+      if (std::find_if(linkVector.begin(), linkVector.end(),
+                       [libItemPtr](cmComputeLinkInformation::Item const* p) {
+                         return p == libItemPtr;
+                       }) == linkVector.end()) {
+        linkVector.push_back(libItemPtr);
+      }
+    };
+  std::vector<cmComputeLinkInformation::Item const*> linkPhaseTargetVector;
+  std::map<std::string, std::vector<std::string>> targetConfigMap;
+  using ConfigItemPair =
+    std::pair<std::string, cmComputeLinkInformation::Item const*>;
+  std::map<std::string, std::vector<ConfigItemPair>> targetItemMap;
+  std::map<std::string, std::vector<std::string>> targetProductNameMap;
+  for (auto const& configName : this->CurrentConfigurationTypes) {
+    cmComputeLinkInformation* cli = gt->GetLinkInformation(configName);
+    if (!cli) {
+      continue;
+    }
+    for (auto const& libItem : cli->GetItems()) {
+      // TODO: Drop this check once we have option to add outside libraries to
+      // Xcode project
+      auto* libTarget = FindXCodeTarget(libItem.Target);
+      if (gt->IsBundleOnApple() &&
+          (gt->GetType() == cmStateEnums::EXECUTABLE ||
+           gt->GetType() == cmStateEnums::SHARED_LIBRARY ||
+           gt->GetType() == cmStateEnums::MODULE_LIBRARY ||
+           gt->GetType() == cmStateEnums::UNKNOWN_LIBRARY) &&
+          (libTarget && libItem.Target &&
+           (libItem.Target->GetType() == cmStateEnums::STATIC_LIBRARY ||
+            libItem.Target->GetType() == cmStateEnums::SHARED_LIBRARY ||
+            libItem.Target->GetType() == cmStateEnums::MODULE_LIBRARY))) {
+        // Add unique configuration name to target-config map for later
+        // checks
+        std::string libName = libItem.Target->GetName();
+        auto& configVector = targetConfigMap[libName];
+        if (std::find(configVector.begin(), configVector.end(), configName) ==
+            configVector.end()) {
+          configVector.push_back(configName);
+        }
+        // Add a pair of config and item to target-item map
+        auto& itemVector = targetItemMap[libName];
+        itemVector.emplace_back(ConfigItemPair(configName, &libItem));
+        // Add product file-name to a lib-product map
+        auto productName = cmSystemTools::GetFilenameName(libItem.Value.Value);
+        auto& productVector = targetProductNameMap[libName];
+        if (std::find(productVector.begin(), productVector.end(),
+                      productName) == productVector.end()) {
+          productVector.push_back(productName);
+        }
+      } else {
+        // Add this library item to a regular linker flag list
+        addToLinkerArguments(configName, &libItem);
+      }
+    }
+  }
+
+  // Go through target library map and separate libraries that are linked
+  // in all configurations and produce only single product, from the rest.
+  // Only these will be linked through "Link Binary With Libraries" build
+  // phase.
+  for (auto const& targetLibConfigs : targetConfigMap) {
+    // Add this library to "Link Binary With Libraries" build phase if it's
+    // linked in all configurations and it has only one product name
+    auto& itemVector = targetItemMap[targetLibConfigs.first];
+    auto& productVector = targetProductNameMap[targetLibConfigs.first];
+    if (targetLibConfigs.second == this->CurrentConfigurationTypes &&
+        productVector.size() == 1) {
+      // Add this library to "Link Binary With Libraries" list
+      linkPhaseTargetVector.push_back(itemVector[0].second);
+    } else {
+      for (auto const& libItem : targetItemMap[targetLibConfigs.first]) {
+        // Add this library item to a regular linker flag list
+        addToLinkerArguments(libItem.first, libItem.second);
+      }
+    }
+  }
+
+  // Add libraries to "Link Binary With Libraries" build phase and collect
+  // their search paths. Xcode does not support per-configuration linking
+  // in this build phase so we don't have to do this for each configuration
+  // separately.
+  std::vector<std::string> linkSearchPaths;
+  for (auto const& libItem : linkPhaseTargetVector) {
+    // Add target output directory as a library search path
+    std::string linkDir = cmSystemTools::GetParentDirectory(
+      libItem->Target->GetLocationForBuild());
+    if (std::find(linkSearchPaths.begin(), linkSearchPaths.end(), linkDir) ==
+        linkSearchPaths.end()) {
+      linkSearchPaths.push_back(linkDir);
+    }
+    // Add target dependency
+    auto const& libName = *libItem;
+    if (!libName.Target->IsImported()) {
+      for (auto const& configName : this->CurrentConfigurationTypes) {
+        target->AddDependTarget(configName, libName.Target->GetName());
+      }
+    }
+    // Get the library target
+    auto* libTarget = FindXCodeTarget(libItem->Target);
+    if (!libTarget) {
+      continue;
+    }
+    // Add the target output file as a build reference for other targets
+    // to link against
+    auto* fileRefObject = libTarget->GetObject("productReference");
+    if (!fileRefObject) {
+      continue;
+    }
+    cmXCodeObject* buildFile;
+    auto it = FileRefToBuildFileMap.find(fileRefObject);
+    if (it == FileRefToBuildFileMap.end()) {
+      buildFile = this->CreateObject(cmXCodeObject::PBXBuildFile);
+      buildFile->AddAttribute("fileRef", fileRefObject);
+      FileRefToBuildFileMap[fileRefObject] = buildFile;
+    } else {
+      buildFile = it->second;
+    }
+    // Add this reference to current target
+    auto* buildPhases = target->GetObject("buildPhases");
+    if (!buildPhases) {
+      continue;
+    }
+    auto* frameworkBuildPhase =
+      buildPhases->GetObject(cmXCodeObject::PBXFrameworksBuildPhase);
+    if (!frameworkBuildPhase) {
+      continue;
+    }
+    auto* buildFiles = frameworkBuildPhase->GetObject("files");
+    if (!buildFiles) {
+      continue;
+    }
+    if (!buildFiles->HasObject(buildFile)) {
+      buildFiles->AddObject(buildFile);
+    }
+  }
+
   // Loop over configuration types and set per-configuration info.
   for (auto const& configName : this->CurrentConfigurationTypes) {
     {
@@ -2820,15 +2968,22 @@ void cmGlobalXCodeGenerator::AddDependAndLinkInformation(cmXCodeObject* target)
           linkDirs += this->XCodeEscapePath(libDir);
         }
       }
+      // Add previously collected paths where to look for libraries
+      // that were added to "Link Binary With Libraries"
+      for (auto& linkDir : linkSearchPaths) {
+        linkDirs += " ";
+        linkDirs += this->XCodeEscapePath(linkDir);
+      }
       this->AppendBuildSettingAttribute(target, "LIBRARY_SEARCH_PATHS",
                                         linkDirs.c_str(), configName);
     }
 
-    // now add the link libraries
+    // now add the left-over link libraries
     {
       std::string linkLibs;
       const char* sep = "";
-      for (auto const& libName : cli.GetItems()) {
+      for (auto const& libItem : configItemMap[configName]) {
+        auto const& libName = *libItem;
         linkLibs += sep;
         sep = " ";
         if (libName.IsPath) {

Source/cmGlobalXCodeGenerator.h

@@ -295,6 +295,7 @@ private:
   std::map<std::string, cmXCodeObject*> TargetGroup;
   std::map<std::string, cmXCodeObject*> FileRefs;
   std::map<cmGeneratorTarget const*, cmXCodeObject*> XCodeObjectMap;
+  std::map<cmXCodeObject*, cmXCodeObject*> FileRefToBuildFileMap;
   std::vector<std::string> Architectures;
   std::string ObjectDirArchDefault;
   std::string ObjectDirArch;