[lldb] Add a setting to specify the preferred dynamic class info extractor o

Add a setting to configure how LLDB parses dynamic Objective-C class
metadata. By default LLDB will choose the most appropriate method for
the target OS.

Differential revision: https://reviews.llvm.org/D128312

lldb/include/lldb/Target/Target.h

@@ -71,6 +71,13 @@ enum ImportStdModule {
   eImportStdModuleTrue,
 };
 
+enum DynamicClassInfoHelper {
+  eDynamicClassInfoHelperAuto,
+  eDynamicClassInfoHelperRealizedClassesStruct,
+  eDynamicClassInfoHelperCopyRealizedClassList,
+  eDynamicClassInfoHelperGetRealizedClassList,
+};
+
 class TargetExperimentalProperties : public Properties {
 public:
   TargetExperimentalProperties();
@@ -152,6 +159,8 @@ public:
 
   ImportStdModule GetImportStdModule() const;
 
+  DynamicClassInfoHelper GetDynamicClassInfoHelper() const;
+
   bool GetEnableAutoApplyFixIts() const;
 
   uint64_t GetNumberOfRetriesWithFixits() const;

lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntimeV2.cpp

@@ -1724,7 +1724,8 @@ AppleObjCRuntimeV2::DynamicClassInfoExtractor::GetClassInfoArgs(Helper helper) {
 }
 
 AppleObjCRuntimeV2::DynamicClassInfoExtractor::Helper
-AppleObjCRuntimeV2::DynamicClassInfoExtractor::ComputeHelper() const {
+AppleObjCRuntimeV2::DynamicClassInfoExtractor::ComputeHelper(
+    ExecutionContext &exe_ctx) const {
   if (!m_runtime.m_has_objc_copyRealizedClassList &&
       !m_runtime.m_has_objc_getRealizedClassList_trylock)
     return DynamicClassInfoExtractor::gdb_objc_realized_classes;
@@ -1732,10 +1733,20 @@ AppleObjCRuntimeV2::DynamicClassInfoExtractor::ComputeHelper() const {
   if (Process *process = m_runtime.GetProcess()) {
     if (DynamicLoader *loader = process->GetDynamicLoader()) {
       if (loader->IsFullyInitialized()) {
-        if (m_runtime.m_has_objc_getRealizedClassList_trylock)
-          return DynamicClassInfoExtractor::objc_getRealizedClassList_trylock;
-        if (m_runtime.m_has_objc_copyRealizedClassList)
-          return DynamicClassInfoExtractor::objc_copyRealizedClassList;
+        switch (exe_ctx.GetTargetRef().GetDynamicClassInfoHelper()) {
+        case eDynamicClassInfoHelperAuto:
+          [[clang::fallthrough]];
+        case eDynamicClassInfoHelperGetRealizedClassList:
+          if (m_runtime.m_has_objc_getRealizedClassList_trylock)
+            return DynamicClassInfoExtractor::objc_getRealizedClassList_trylock;
+          [[clang::fallthrough]];
+        case eDynamicClassInfoHelperCopyRealizedClassList:
+          if (m_runtime.m_has_objc_copyRealizedClassList)
+            return DynamicClassInfoExtractor::objc_copyRealizedClassList;
+          [[clang::fallthrough]];
+        case eDynamicClassInfoHelperRealizedClassesStruct:
+          return DynamicClassInfoExtractor::gdb_objc_realized_classes;
+        }
       }
     }
   }
@@ -1872,7 +1883,7 @@ AppleObjCRuntimeV2::DynamicClassInfoExtractor::UpdateISAToDescriptorMap(
   Status err;
 
   // Compute which helper we're going to use for this update.
-  const DynamicClassInfoExtractor::Helper helper = ComputeHelper();
+  const DynamicClassInfoExtractor::Helper helper = ComputeHelper(exe_ctx);
 
   // Read the total number of classes from the hash table
   const uint32_t num_classes =

lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntimeV2.h

@@ -341,7 +341,7 @@ private:
     /// must use gdb_objc_realized_classes. Otherwise, we prefer
     /// objc_getRealizedClassList_trylock and objc_copyRealizedClassList
     /// respectively, depending on availability.
-    Helper ComputeHelper() const;
+    Helper ComputeHelper(ExecutionContext &exe_ctx) const;
 
     UtilityFunction *GetClassInfoUtilityFunction(ExecutionContext &exe_ctx,
                                                  Helper helper);

lldb/source/Target/Target.cpp

@@ -3801,6 +3801,22 @@ static constexpr OptionEnumValueElement g_import_std_module_value_types[] = {
     },
 };
 
+static constexpr OptionEnumValueElement
+    g_dynamic_class_info_helper_value_types[] = {
+        {
+            eDynamicClassInfoHelperAuto,
+            "auto",
+            "Automatically determine the most appropriate method for the "
+            "target OS.",
+        },
+        {eDynamicClassInfoHelperRealizedClassesStruct, "RealizedClassesStruct",
+         "Prefer using the realized classes struct."},
+        {eDynamicClassInfoHelperCopyRealizedClassList, "CopyRealizedClassList",
+         "Prefer using the CopyRealizedClassList API."},
+        {eDynamicClassInfoHelperGetRealizedClassList, "GetRealizedClassList",
+         "Prefer using the GetRealizedClassList API."},
+};
+
 static constexpr OptionEnumValueElement g_hex_immediate_style_values[] = {
     {
         Disassembler::eHexStyleC,
@@ -4299,6 +4315,13 @@ ImportStdModule TargetProperties::GetImportStdModule() const {
       nullptr, idx, g_target_properties[idx].default_uint_value);
 }
 
+DynamicClassInfoHelper TargetProperties::GetDynamicClassInfoHelper() const {
+  const uint32_t idx = ePropertyDynamicClassInfoHelper;
+  return (DynamicClassInfoHelper)
+      m_collection_sp->GetPropertyAtIndexAsEnumeration(
+          nullptr, idx, g_target_properties[idx].default_uint_value);
+}
+
 bool TargetProperties::GetEnableAutoApplyFixIts() const {
   const uint32_t idx = ePropertyAutoApplyFixIts;
   return m_collection_sp->GetPropertyAtIndexAsBoolean(

lldb/source/Target/TargetProperties.td

@@ -54,6 +54,10 @@ let Definition = "target" in {
     EnumValues<"OptionEnumValues(g_import_std_module_value_types)">,
     Desc<"Import the 'std' C++ module to improve expression parsing involving "
          " C++ standard library types.">;
+  def DynamicClassInfoHelper: Property<"objc-dynamic-class-extractor", "Enum">,
+    DefaultEnumValue<"eDynamicClassInfoHelperAuto">,
+    EnumValues<"OptionEnumValues(g_dynamic_class_info_helper_value_types)">,
+    Desc<"Configure how LLDB parses dynamic Objective-C class metadata. By default LLDB will choose the most appropriate method for the target OS.">;
   def AutoApplyFixIts: Property<"auto-apply-fixits", "Boolean">,
     DefaultTrue,
     Desc<"Automatically apply fix-it hints to expressions.">;