[lldb] Make LanguageRuntime::GetTypeBitSize return an optional (NFC)

lldb/include/lldb/Target/LanguageRuntime.h

@@ -169,9 +169,9 @@ class LanguageRuntime : public Runtime, public PluginInterface {
     return m_process->GetTarget().GetSearchFilterForModule(nullptr);
   }
 
-  virtual bool GetTypeBitSize(const CompilerType &compiler_type,
-                              uint64_t &size) {
-    return false;
+  virtual std::optional<uint64_t>
+  GetTypeBitSize(const CompilerType &compiler_type) {
+    return {};
   }
 
   virtual void SymbolsDidLoad(const ModuleList &module_list) {}

lldb/source/Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.cpp

@@ -350,18 +350,17 @@ ObjCLanguageRuntime::EncodingToTypeSP ObjCLanguageRuntime::GetEncodingToType() {
   return nullptr;
 }
 
-bool ObjCLanguageRuntime::GetTypeBitSize(const CompilerType &compiler_type,
-                                         uint64_t &size) {
+std::optional<uint64_t>
+ObjCLanguageRuntime::GetTypeBitSize(const CompilerType &compiler_type) {
   void *opaque_ptr = compiler_type.GetOpaqueQualType();
-  size = m_type_size_cache.Lookup(opaque_ptr);
-  // an ObjC object will at least have an ISA, so 0 is definitely not OK
-  if (size > 0)
-    return true;
+  uint64_t cached_size = m_type_size_cache.Lookup(opaque_ptr);
+  if (cached_size > 0)
+    return cached_size;
 
   ClassDescriptorSP class_descriptor_sp =
       GetClassDescriptorFromClassName(compiler_type.GetTypeName());
   if (!class_descriptor_sp)
-    return false;
+    return {};
 
   int32_t max_offset = INT32_MIN;
   uint64_t sizeof_max = 0;
@@ -377,11 +376,13 @@ bool ObjCLanguageRuntime::GetTypeBitSize(const CompilerType &compiler_type,
     }
   }
 
-  size = 8 * (max_offset + sizeof_max);
-  if (found)
+  uint64_t size = 8 * (max_offset + sizeof_max);
+  if (found && size > 0) {
     m_type_size_cache.Insert(opaque_ptr, size);
+    return size;
+  }
 
-  return found;
+  return {};
 }
 
 lldb::BreakpointPreconditionSP

lldb/source/Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.h

@@ -107,7 +107,7 @@ class ObjCLanguageRuntime : public LanguageRuntime {
                                             int64_t *value_bits = nullptr,
                                             uint64_t *payload = nullptr) = 0;
     /// @}
- 
+
     virtual uint64_t GetInstanceSize() = 0;
 
     // use to implement version-specific additional constraints on pointers
@@ -321,8 +321,8 @@ class ObjCLanguageRuntime : public LanguageRuntime {
     m_negative_complete_class_cache.clear();
   }
 
-  bool GetTypeBitSize(const CompilerType &compiler_type,
-                      uint64_t &size) override;
+  std::optional<uint64_t>
+  GetTypeBitSize(const CompilerType &compiler_type) override;
 
   /// Check whether the name is "self" or "_cmd" and should show up in
   /// "frame variable".

lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp

@@ -4744,11 +4744,11 @@ TypeSystemClang::GetBitSize(lldb::opaque_compiler_type_t type,
       ExecutionContext exe_ctx(exe_scope);
       Process *process = exe_ctx.GetProcessPtr();
       if (process) {
-        ObjCLanguageRuntime *objc_runtime = ObjCLanguageRuntime::Get(*process);
-        if (objc_runtime) {
-          uint64_t bit_size = 0;
-          if (objc_runtime->GetTypeBitSize(GetType(qual_type), bit_size))
-            return bit_size;
+        if (ObjCLanguageRuntime *objc_runtime =
+                ObjCLanguageRuntime::Get(*process)) {
+          if (std::optional<uint64_t> bit_size =
+                  objc_runtime->GetTypeBitSize(GetType(qual_type)))
+            return *bit_size;
         }
       } else {
         static bool g_printed = false;