Refactor GetObjectDescription() to return llvm::Expected (NFC)

This is de facto an NFC change for Objective-C but will benefit the
Swift language plugin.

12 files changed, 143 insertions, 103 deletions

diff --git a/lldb/include/lldb/Core/ValueObject.h b/lldb/include/lldb/Core/ValueObject.h
index 205d9ad..93eb3e8 100644
--- a/lldb/include/lldb/Core/ValueObject.h
+++ b/lldb/include/lldb/Core/ValueObject.h
@@ -537,7 +537,7 @@ public:
                            std::string &destination,
                            const TypeSummaryOptions &options);
 
-  const char *GetObjectDescription();
+  llvm::Expected<std::string> GetObjectDescription();
 
   bool HasSpecialPrintableRepresentation(
       ValueObjectRepresentationStyle val_obj_display,
diff --git a/lldb/include/lldb/DataFormatters/ValueObjectPrinter.h b/lldb/include/lldb/DataFormatters/ValueObjectPrinter.h
index 7460370..f9deb6e 100644
--- a/lldb/include/lldb/DataFormatters/ValueObjectPrinter.h
+++ b/lldb/include/lldb/DataFormatters/ValueObjectPrinter.h
@@ -75,7 +75,7 @@ protected:
 
   void SetupMostSpecializedValue();
 
-  const char *GetDescriptionForDisplay();
+  llvm::Expected<std::string> GetDescriptionForDisplay();
 
   const char *GetRootNameForDisplay();
 
@@ -108,7 +108,8 @@ protected:
 
   bool PrintValueAndSummaryIfNeeded(bool &value_printed, bool &summary_printed);
 
-  bool PrintObjectDescriptionIfNeeded(bool value_printed, bool summary_printed);
+  llvm::Error PrintObjectDescriptionIfNeeded(bool value_printed,
+                                             bool summary_printed);
 
   bool
   ShouldPrintChildren(DumpValueObjectOptions::PointerDepth &curr_ptr_depth);
@@ -132,7 +133,7 @@ protected:
   PrintChildren(bool value_printed, bool summary_printed,
                 const DumpValueObjectOptions::PointerDepth &curr_ptr_depth);
 
-  void PrintChildrenIfNeeded(bool value_printed, bool summary_printed);
+  llvm::Error PrintChildrenIfNeeded(bool value_printed, bool summary_printed);
 
   bool PrintChildrenOneLiner(bool hide_names);
 
diff --git a/lldb/include/lldb/Target/LanguageRuntime.h b/lldb/include/lldb/Target/LanguageRuntime.h
index a2a9c016..d093dcc 100644
--- a/lldb/include/lldb/Target/LanguageRuntime.h
+++ b/lldb/include/lldb/Target/LanguageRuntime.h
@@ -73,11 +73,12 @@ public:
     return nullptr;
   }
 
-  virtual bool GetObjectDescription(Stream &str, ValueObject &object) = 0;
-
-  virtual bool GetObjectDescription(Stream &str, Value &value,
-                                    ExecutionContextScope *exe_scope) = 0;
+  virtual llvm::Error GetObjectDescription(Stream &str,
+                                           ValueObject &object) = 0;
 
+  virtual llvm::Error
+  GetObjectDescription(Stream &str, Value &value,
+                       ExecutionContextScope *exe_scope) = 0;
 
   struct VTableInfo {
     Address addr; /// Address of the vtable's virtual function table
diff --git a/lldb/source/API/SBValue.cpp b/lldb/source/API/SBValue.cpp
index 1b9cae6..10a691c 100644
--- a/lldb/source/API/SBValue.cpp
+++ b/lldb/source/API/SBValue.cpp
@@ -379,7 +379,10 @@ const char *SBValue::GetObjectDescription() {
   if (!value_sp)
     return nullptr;
 
-  return ConstString(value_sp->GetObjectDescription()).GetCString();
+  llvm::Expected<std::string> str = value_sp->GetObjectDescription();
+  if (!str)
+    return ConstString("error: " + toString(str.takeError())).AsCString();
+  return ConstString(*str).AsCString();
 }
 
 SBType SBValue::GetType() {
diff --git a/lldb/source/Core/ValueObject.cpp b/lldb/source/Core/ValueObject.cpp
index cf0f557..8f72efc 100644
--- a/lldb/source/Core/ValueObject.cpp
+++ b/lldb/source/Core/ValueObject.cpp
@@ -989,41 +989,46 @@ ValueObject::ReadPointedString(lldb::WritableDataBufferSP &buffer_sp,
   return {total_bytes_read, was_capped};
 }
 
-const char *ValueObject::GetObjectDescription() {
+llvm::Expected<std::string> ValueObject::GetObjectDescription() {
   if (!UpdateValueIfNeeded(true))
-    return nullptr;
+    return llvm::createStringError("could not update value");
 
   // Return cached value.
   if (!m_object_desc_str.empty())
-    return m_object_desc_str.c_str();
+    return m_object_desc_str;
 
   ExecutionContext exe_ctx(GetExecutionContextRef());
   Process *process = exe_ctx.GetProcessPtr();
   if (!process)
-    return nullptr;
+    return llvm::createStringError("no process");
 
   // Returns the object description produced by one language runtime.
-  auto get_object_description = [&](LanguageType language) -> const char * {
+  auto get_object_description =
+      [&](LanguageType language) -> llvm::Expected<std::string> {
     if (LanguageRuntime *runtime = process->GetLanguageRuntime(language)) {
       StreamString s;
-      if (runtime->GetObjectDescription(s, *this)) {
-        m_object_desc_str.append(std::string(s.GetString()));
-        return m_object_desc_str.c_str();
-      }
+      if (llvm::Error error = runtime->GetObjectDescription(s, *this))
+        return error;
+      m_object_desc_str = s.GetString();
+      return m_object_desc_str;
     }
-    return nullptr;
+    return llvm::createStringError("no native language runtime");
   };
 
   // Try the native language runtime first.
   LanguageType native_language = GetObjectRuntimeLanguage();
-  if (const char *desc = get_object_description(native_language))
+  llvm::Expected<std::string> desc = get_object_description(native_language);
+  if (desc)
     return desc;
 
   // Try the Objective-C language runtime. This fallback is necessary
   // for Objective-C++ and mixed Objective-C / C++ programs.
-  if (Language::LanguageIsCFamily(native_language))
+  if (Language::LanguageIsCFamily(native_language)) {
+    // We're going to try again, so let's drop the first error.
+    llvm::consumeError(desc.takeError());
     return get_object_description(eLanguageTypeObjC);
-  return nullptr;
+  }
+  return desc;
 }
 
 bool ValueObject::GetValueAsCString(const lldb_private::TypeFormatImpl &format,
@@ -1472,9 +1477,16 @@ bool ValueObject::DumpPrintableRepresentation(
       str = GetSummaryAsCString();
       break;
 
-    case eValueObjectRepresentationStyleLanguageSpecific:
-      str = GetObjectDescription();
-      break;
+    case eValueObjectRepresentationStyleLanguageSpecific: {
+      llvm::Expected<std::string> desc = GetObjectDescription();
+      if (!desc) {
+        strm << "error: " << toString(desc.takeError());
+        str = strm.GetString();
+      } else {
+        strm << *desc;
+        str = strm.GetString();
+      }
+    } break;
 
     case eValueObjectRepresentationStyleLocation:
       str = GetLocationAsCString();
diff --git a/lldb/source/DataFormatters/ValueObjectPrinter.cpp b/lldb/source/DataFormatters/ValueObjectPrinter.cpp
index a81a5172..ce24a78 100644
--- a/lldb/source/DataFormatters/ValueObjectPrinter.cpp
+++ b/lldb/source/DataFormatters/ValueObjectPrinter.cpp
@@ -91,9 +91,8 @@ llvm::Error ValueObjectPrinter::PrintValueObject() {
       PrintValueAndSummaryIfNeeded(value_printed, summary_printed);
 
   if (m_val_summary_ok)
-    PrintChildrenIfNeeded(value_printed, summary_printed);
-  else
-    m_stream->EOL();
+    return PrintChildrenIfNeeded(value_printed, summary_printed);
+  m_stream->EOL();
 
   return llvm::Error::success();
 }
@@ -145,13 +144,21 @@ void ValueObjectPrinter::SetupMostSpecializedValue() {
          "SetupMostSpecialized value must compute a valid ValueObject");
 }
 
-const char *ValueObjectPrinter::GetDescriptionForDisplay() {
+llvm::Expected<std::string> ValueObjectPrinter::GetDescriptionForDisplay() {
   ValueObject &valobj = GetMostSpecializedValue();
-  const char *str = valobj.GetObjectDescription();
+  llvm::Expected<std::string> maybe_str = valobj.GetObjectDescription();
+  if (maybe_str)
+    return maybe_str;
+
+  const char *str = nullptr;
   if (!str)
     str = valobj.GetSummaryAsCString();
   if (!str)
     str = valobj.GetValueAsCString();
+
+  if (!str)
+    return maybe_str;
+  llvm::consumeError(maybe_str.takeError());
   return str;
 }
 
@@ -461,34 +468,38 @@ bool ValueObjectPrinter::PrintValueAndSummaryIfNeeded(bool &value_printed,
   return !error_printed;
 }
 
-bool ValueObjectPrinter::PrintObjectDescriptionIfNeeded(bool value_printed,
-                                                        bool summary_printed) {
+llvm::Error
+ValueObjectPrinter::PrintObjectDescriptionIfNeeded(bool value_printed,
+                                                   bool summary_printed) {
   if (ShouldPrintValueObject()) {
     // let's avoid the overly verbose no description error for a nil thing
     if (m_options.m_use_objc && !IsNil() && !IsUninitialized() &&
         (!m_options.m_pointer_as_array)) {
       if (!m_options.m_hide_value || ShouldShowName())
-        m_stream->Printf(" ");
-      const char *object_desc = nullptr;
-      if (value_printed || summary_printed)
-        object_desc = GetMostSpecializedValue().GetObjectDescription();
-      else
-        object_desc = GetDescriptionForDisplay();
-      if (object_desc && *object_desc) {
+        *m_stream << ' ';
+      llvm::Expected<std::string> object_desc =
+          (value_printed || summary_printed)
+              ? GetMostSpecializedValue().GetObjectDescription()
+              : GetDescriptionForDisplay();
+      if (!object_desc) {
+        // If no value or summary was printed, surface the error.
+        if (!value_printed && !summary_printed)
+          return object_desc.takeError();
+        // Otherwise gently nudge the user that they should have used
+        // `p` instead of `po`. Unfortunately we cannot be more direct
+        // about this, because we don't actually know what the user did.
+        *m_stream << "warning: no object description available\n";
+        llvm::consumeError(object_desc.takeError());
+      } else {
+        *m_stream << *object_desc;
         // If the description already ends with a \n don't add another one.
-        size_t object_end = strlen(object_desc) - 1;
-        if (object_desc[object_end] == '\n')
-          m_stream->Printf("%s", object_desc);
-        else
-          m_stream->Printf("%s\n", object_desc);
-        return true;
-      } else if (!value_printed && !summary_printed)
-        return true;
-      else
-        return false;
+        if (object_desc->empty() || object_desc->back() != '\n')
+          *m_stream << '\n';
+      }
+      return llvm::Error::success();
     }
   }
-  return true;
+  return llvm::Error::success();
 }
 
 bool DumpValueObjectOptions::PointerDepth::CanAllowExpansion() const {
@@ -812,9 +823,12 @@ bool ValueObjectPrinter::PrintChildrenOneLiner(bool hide_names) {
   return true;
 }
 
-void ValueObjectPrinter::PrintChildrenIfNeeded(bool value_printed,
-                                               bool summary_printed) {
-  PrintObjectDescriptionIfNeeded(value_printed, summary_printed);
+llvm::Error ValueObjectPrinter::PrintChildrenIfNeeded(bool value_printed,
+                                                      bool summary_printed) {
+  auto error = PrintObjectDescriptionIfNeeded(value_printed, summary_printed);
+  if (error)
+    return error;
+
   ValueObject &valobj = GetMostSpecializedValue();
 
   DumpValueObjectOptions::PointerDepth curr_ptr_depth = m_ptr_depth;
@@ -830,7 +844,7 @@ void ValueObjectPrinter::PrintChildrenIfNeeded(bool value_printed,
     if (m_printed_instance_pointers->count(instance_ptr_value)) {
       // We already printed this instance-is-pointer thing, so don't expand it.
       m_stream->PutCString(" {...}\n");
-      return;
+      return llvm::Error::success();
     } else {
       // Remember this guy for future reference.
       m_printed_instance_pointers->emplace(instance_ptr_value);
@@ -858,6 +872,7 @@ void ValueObjectPrinter::PrintChildrenIfNeeded(bool value_printed,
           .SetReachedMaximumDepth();
   } else
     m_stream->EOL();
+  return llvm::Error::success();
 }
 
 bool ValueObjectPrinter::HasReachedMaximumDepth() {
diff --git a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp
index 300ecc8..c7202a4 100644
--- a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp
+++ b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp
@@ -47,16 +47,17 @@ bool CPPLanguageRuntime::IsAllowedRuntimeValue(ConstString name) {
   return name == g_this || name == g_promise || name == g_coro_frame;
 }
 
-bool CPPLanguageRuntime::GetObjectDescription(Stream &str,
-                                              ValueObject &object) {
+llvm::Error CPPLanguageRuntime::GetObjectDescription(Stream &str,
+                                                     ValueObject &object) {
   // C++ has no generic way to do this.
-  return false;
+  return llvm::createStringError("C++ does not support object descriptions");
 }
 
-bool CPPLanguageRuntime::GetObjectDescription(
-    Stream &str, Value &value, ExecutionContextScope *exe_scope) {
+llvm::Error
+CPPLanguageRuntime::GetObjectDescription(Stream &str, Value &value,
+                                         ExecutionContextScope *exe_scope) {
   // C++ has no generic way to do this.
-  return false;
+  return llvm::createStringError("C++ does not support object descriptions");
 }
 
 bool contains_lambda_identifier(llvm::StringRef &str_ref) {
diff --git a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h
index 1be58b7..57cfe282 100644
--- a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h
+++ b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h
@@ -59,10 +59,10 @@ public:
         process.GetLanguageRuntime(lldb::eLanguageTypeC_plus_plus));
   }
 
-  bool GetObjectDescription(Stream &str, ValueObject &object) override;
+  llvm::Error GetObjectDescription(Stream &str, ValueObject &object) override;
 
-  bool GetObjectDescription(Stream &str, Value &value,
-                            ExecutionContextScope *exe_scope) override;
+  llvm::Error GetObjectDescription(Stream &str, Value &value,
+                                   ExecutionContextScope *exe_scope) override;
 
   /// Obtain a ThreadPlan to get us into C++ constructs such as std::function.
   ///
diff --git a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.cpp b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.cpp
index 9434376..800eda9 100644
--- a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.cpp
+++ b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.cpp
@@ -67,20 +67,21 @@ void AppleObjCRuntime::Terminate() {
   AppleObjCRuntimeV1::Terminate();
 }
 
-bool AppleObjCRuntime::GetObjectDescription(Stream &str, ValueObject &valobj) {
+llvm::Error AppleObjCRuntime::GetObjectDescription(Stream &str,
+                                                   ValueObject &valobj) {
   CompilerType compiler_type(valobj.GetCompilerType());
   bool is_signed;
   // ObjC objects can only be pointers (or numbers that actually represents
   // pointers but haven't been typecast, because reasons..)
   if (!compiler_type.IsIntegerType(is_signed) && !compiler_type.IsPointerType())
-    return false;
+    return llvm::createStringError("not a pointer type");
 
   // Make the argument list: we pass one arg, the address of our pointer, to
   // the print function.
   Value val;
 
   if (!valobj.ResolveValue(val.GetScalar()))
-    return false;
+    return llvm::createStringError("pointer value could not be resolved");
 
   // Value Objects may not have a process in their ExecutionContextRef.  But we
   // need to have one in the ref we pass down to eventually call description.
@@ -91,20 +92,22 @@ bool AppleObjCRuntime::GetObjectDescription(Stream &str, ValueObject &valobj) {
   } else {
     exe_ctx.SetContext(valobj.GetTargetSP(), true);
     if (!exe_ctx.HasProcessScope())
-      return false;
+      return llvm::createStringError("no process");
   }
   return GetObjectDescription(str, val, exe_ctx.GetBestExecutionContextScope());
 }
-bool AppleObjCRuntime::GetObjectDescription(Stream &strm, Value &value,
-                                            ExecutionContextScope *exe_scope) {
+
+llvm::Error
+AppleObjCRuntime::GetObjectDescription(Stream &strm, Value &value,
+                                       ExecutionContextScope *exe_scope) {
   if (!m_read_objc_library)
-    return false;
+    return llvm::createStringError("Objective-C runtime not loaded");
 
   ExecutionContext exe_ctx;
   exe_scope->CalculateExecutionContext(exe_ctx);
   Process *process = exe_ctx.GetProcessPtr();
   if (!process)
-    return false;
+    return llvm::createStringError("no process");
 
   // We need other parts of the exe_ctx, but the processes have to match.
   assert(m_process == process);
@@ -112,25 +115,25 @@ bool AppleObjCRuntime::GetObjectDescription(Stream &strm, Value &value,
   // Get the function address for the print function.
   const Address *function_address = GetPrintForDebuggerAddr();
   if (!function_address)
-    return false;
+    return llvm::createStringError("no print function");
 
   Target *target = exe_ctx.GetTargetPtr();
   CompilerType compiler_type = value.GetCompilerType();
   if (compiler_type) {
-    if (!TypeSystemClang::IsObjCObjectPointerType(compiler_type)) {
-      strm.Printf("Value doesn't point to an ObjC object.\n");
-      return false;
-    }
+    if (!TypeSystemClang::IsObjCObjectPointerType(compiler_type))
+      return llvm::createStringError(
+          "Value doesn't point to an ObjC object.\n");
   } else {
     // If it is not a pointer, see if we can make it into a pointer.
     TypeSystemClangSP scratch_ts_sp =
         ScratchTypeSystemClang::GetForTarget(*target);
     if (!scratch_ts_sp)
-      return false;
+      return llvm::createStringError("no scratch type system");
 
     CompilerType opaque_type = scratch_ts_sp->GetBasicType(eBasicTypeObjCID);
     if (!opaque_type)
-      opaque_type = scratch_ts_sp->GetBasicType(eBasicTypeVoid).GetPointerType();
+      opaque_type =
+          scratch_ts_sp->GetBasicType(eBasicTypeVoid).GetPointerType();
     // value.SetContext(Value::eContextTypeClangType, opaque_type_ptr);
     value.SetCompilerType(opaque_type);
   }
@@ -142,14 +145,14 @@ bool AppleObjCRuntime::GetObjectDescription(Stream &strm, Value &value,
   TypeSystemClangSP scratch_ts_sp =
       ScratchTypeSystemClang::GetForTarget(*target);
   if (!scratch_ts_sp)
-    return false;
+    return llvm::createStringError("no scratch type system");
 
   CompilerType return_compiler_type = scratch_ts_sp->GetCStringType(true);
   Value ret;
   //    ret.SetContext(Value::eContextTypeClangType, return_compiler_type);
   ret.SetCompilerType(return_compiler_type);
 
-  if (exe_ctx.GetFramePtr() == nullptr) {
+  if (!exe_ctx.GetFramePtr()) {
     Thread *thread = exe_ctx.GetThreadPtr();
     if (thread == nullptr) {
       exe_ctx.SetThreadSP(process->GetThreadList().GetSelectedThread());
@@ -173,10 +176,11 @@ bool AppleObjCRuntime::GetObjectDescription(Stream &strm, Value &value,
             arg_value_list, "objc-object-description", error));
     if (error.Fail()) {
       m_print_object_caller_up.reset();
-      strm.Printf("Could not get function runner to call print for debugger "
-                  "function: %s.",
-                  error.AsCString());
-      return false;
+      return llvm::createStringError(
+          llvm::Twine(
+              "could not get function runner to call print for debugger "
+              "function: ") +
+          error.AsCString());
     }
     m_print_object_caller_up->InsertFunction(exe_ctx, wrapper_struct_addr,
                                              diagnostics);
@@ -195,10 +199,9 @@ bool AppleObjCRuntime::GetObjectDescription(Stream &strm, Value &value,
 
   ExpressionResults results = m_print_object_caller_up->ExecuteFunction(
       exe_ctx, &wrapper_struct_addr, options, diagnostics, ret);
-  if (results != eExpressionCompleted) {
-    strm.Printf("Error evaluating Print Object function: %d.\n", results);
-    return false;
-  }
+  if (results != eExpressionCompleted)
+    return llvm::createStringError(
+        "Error evaluating Print Object function: %d.\n", results);
 
   addr_t result_ptr = ret.GetScalar().ULongLong(LLDB_INVALID_ADDRESS);
 
@@ -213,7 +216,9 @@ bool AppleObjCRuntime::GetObjectDescription(Stream &strm, Value &value,
     strm.Write(buf, curr_len);
     cstr_len += curr_len;
   }
-  return cstr_len > 0;
+  if (cstr_len > 0)
+    return llvm::Error::success();
+  return llvm::createStringError("empty object description");
 }
 
 lldb::ModuleSP AppleObjCRuntime::GetObjCModule() {
diff --git a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.h b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.h
index cfeec3d6..da58d44 100644
--- a/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.h
+++ b/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.h
@@ -44,10 +44,10 @@ public:
   }
 
   // These are generic runtime functions:
-  bool GetObjectDescription(Stream &str, Value &value,
-                            ExecutionContextScope *exe_scope) override;
+  llvm::Error GetObjectDescription(Stream &str, Value &value,
+                                   ExecutionContextScope *exe_scope) override;
 
-  bool GetObjectDescription(Stream &str, ValueObject &object) override;
+  llvm::Error GetObjectDescription(Stream &str, ValueObject &object) override;
 
   bool CouldHaveDynamicValue(ValueObject &in_value) override;
 
diff --git a/lldb/source/Plugins/LanguageRuntime/ObjC/GNUstepObjCRuntime/GNUstepObjCRuntime.cpp b/lldb/source/Plugins/LanguageRuntime/ObjC/GNUstepObjCRuntime/GNUstepObjCRuntime.cpp
index 39b3e81..58b8387 100644
--- a/lldb/source/Plugins/LanguageRuntime/ObjC/GNUstepObjCRuntime/GNUstepObjCRuntime.cpp
+++ b/lldb/source/Plugins/LanguageRuntime/ObjC/GNUstepObjCRuntime/GNUstepObjCRuntime.cpp
@@ -104,15 +104,17 @@ GNUstepObjCRuntime::GNUstepObjCRuntime(Process *process)
   ReadObjCLibraryIfNeeded(process->GetTarget().GetImages());
 }
 
-bool GNUstepObjCRuntime::GetObjectDescription(Stream &str,
-                                              ValueObject &valobj) {
-  // TODO: ObjC has a generic way to do this
-  return false;
+llvm::Error GNUstepObjCRuntime::GetObjectDescription(Stream &str,
+                                                     ValueObject &valobj) {
+  return llvm::createStringError(
+      "LLDB's GNUStep runtime does not support object description");
 }
-bool GNUstepObjCRuntime::GetObjectDescription(
-    Stream &strm, Value &value, ExecutionContextScope *exe_scope) {
-  // TODO: ObjC has a generic way to do this
-  return false;
+
+llvm::Error
+GNUstepObjCRuntime::GetObjectDescription(Stream &strm, Value &value,
+                                         ExecutionContextScope *exe_scope) {
+  return llvm::createStringError(
+      "LLDB's GNUStep runtime does not support object description");
 }
 
 bool GNUstepObjCRuntime::CouldHaveDynamicValue(ValueObject &in_value) {
diff --git a/lldb/source/Plugins/LanguageRuntime/ObjC/GNUstepObjCRuntime/GNUstepObjCRuntime.h b/lldb/source/Plugins/LanguageRuntime/ObjC/GNUstepObjCRuntime/GNUstepObjCRuntime.h
index b220888..de24466 100644
--- a/lldb/source/Plugins/LanguageRuntime/ObjC/GNUstepObjCRuntime/GNUstepObjCRuntime.h
+++ b/lldb/source/Plugins/LanguageRuntime/ObjC/GNUstepObjCRuntime/GNUstepObjCRuntime.h
@@ -57,10 +57,10 @@ public:
   //
   // LanguageRuntime implementation
   //
-  bool GetObjectDescription(Stream &str, Value &value,
-                            ExecutionContextScope *exe_scope) override;
+  llvm::Error GetObjectDescription(Stream &str, Value &value,
+                                   ExecutionContextScope *exe_scope) override;
 
-  bool GetObjectDescription(Stream &str, ValueObject &object) override;
+  llvm::Error GetObjectDescription(Stream &str, ValueObject &object) override;
 
   bool CouldHaveDynamicValue(ValueObject &in_value) override;