[lldb] Add synthetic frontend for _NSCallStackArray

[kubamracek]

Summary

An Obj-C array type _NSCallStackArray is used in NSException backtraces. This patch adds a synthetic frontend for _NSCallStackArray, which now correctly returns frame PCs.

[kubamracek]

Ping.

[davide]

source/Plugins/Language/ObjC/NSArray.cpp

444–449

Can you add a comment here?
this also seems exactly the same as NSArrayCF, any chance we can avoid the duplication?

[kubamracek]

source/Plugins/Language/ObjC/NSArray.cpp

444–449

Added comment and de-duplicated the branch.

[davide]

Thanks for addressing my comments.

packages/Python/lldbsuite/test/lang/objc/exceptions/TestObjCExceptions.py

def test_objc_exceptions_1(self):
         target = self.dbg.CreateTarget(self.getBuildArtifact("a.out"))
         self.assertTrue(target, VALID_TARGET)
 
         lldbutil.run_to_source_breakpoint(self, "// Set break point at this line.", lldb.SBFileSpec("main.m"))
 
         self.expect("thread list", STOPPED_DUE_TO_BREAKPOINT,
                     substrs=['stopped', 'stop reason = breakpoint'])
 
-        thread = self.dbg.GetSelectedTarget().GetProcess().GetSelectedThread()
+        target = self.dbg.GetSelectedTarget()
+        thread = target.GetProcess().GetSelectedThread()
         frame = thread.GetSelectedFrame()
 
         self.expect(
             'frame variable e1',
             substrs=[
                 '(NSException *) e1 = ',
                 'name: @"ExceptionName" - reason: @"SomeReason"'
             ])
def test_objc_exceptions_1(self):
         self.assertEqual(e2.type.name, "NSException *")
         self.assertEqual(e2.GetSummary(), 'name: @"ThrownException" - reason: @"SomeReason"')
         self.assertEqual(e2.GetChildMemberWithName("name").description, "ThrownException")
         self.assertEqual(e2.GetChildMemberWithName("reason").description, "SomeReason")
         userInfo = e2.GetChildMemberWithName("userInfo").dynamic
         self.assertEqual(userInfo.summary, "1 key/value pair")
         self.assertEqual(userInfo.GetChildAtIndex(0).GetChildAtIndex(0).description, "some_key")
         self.assertEqual(userInfo.GetChildAtIndex(0).GetChildAtIndex(1).description, "some_value")
-        self.assertGreater(e2.GetChildMemberWithName("reserved").dynamic.num_children, 0)
+        reserved = e2.GetChildMemberWithName("reserved").dynamic
+        self.assertGreater(reserved.num_children, 0)
+        callStackReturnAddresses = [reserved.GetChildAtIndex(i).GetChildAtIndex(1) for i in range(0, reserved.GetNumChildren())
+                if reserved.GetChildAtIndex(i).GetChildAtIndex(0).description == "callStackReturnAddresses"][0].dynamic
+        children = [callStackReturnAddresses.GetChildAtIndex(i) for i in range(0, callStackReturnAddresses.num_children)]
+
+        pcs = [i.unsigned for i in children]
+        names = [target.ResolveSymbolContextForAddress(lldb.SBAddress(pc, target), lldb.eSymbolContextSymbol).GetSymbol().name for pc in pcs]
+        for n in ["objc_exception_throw", "foo", "main"]:
+            self.assertTrue(n in names, "%s is in the exception backtrace (%s)" % (n, names))

source/Plugins/Language/ObjC/NSArray.cpp

__NSArrayMSize(lldb_private::Process &process, lldb::addr_t valobj_addr,
     } else {
       return __NSArrayMSize_Impl<DataDescriptor<uint64_t>>(process, valobj_addr,
                                                            error);
     }
   }
 
 }
 
+namespace CallStackArray {
+struct DataDescriptor_32 {
+  uint32_t _data;
+  uint32_t _used;
+  uint32_t _offset;
+  const uint32_t _size = 0;
+};
+
+struct DataDescriptor_64 {
+  uint64_t _data;
+  uint64_t _used;
+  uint64_t _offset;
+  const uint64_t _size = 0;
+};
+
+using NSCallStackArraySyntheticFrontEnd =
+    GenericNSArrayMSyntheticFrontEnd<DataDescriptor_32, DataDescriptor_64>;
+} // namespace CallStackArray
+
 template <typename D32, typename D64, bool Inline>
 class GenericNSArrayISyntheticFrontEnd : public SyntheticChildrenFrontEnd {
 public:
   GenericNSArrayISyntheticFrontEnd(lldb::ValueObjectSP valobj_sp);
 
   ~GenericNSArrayISyntheticFrontEnd() override;
 
   size_t CalculateNumChildren() override;
bool lldb_private::formatters::NSArraySummaryProvider(
   static const ConstString g_NSArrayM("__NSArrayM");
   static const ConstString g_NSArrayI_Transfer("__NSArrayI_Transfer");
   static const ConstString g_NSFrozenArrayM("__NSFrozenArrayM");
   static const ConstString g_NSArray0("__NSArray0");
   static const ConstString g_NSArray1("__NSSingleObjectArrayI");
   static const ConstString g_NSArrayCF("__NSCFArray");
   static const ConstString g_NSArrayMLegacy("__NSArrayM_Legacy");
   static const ConstString g_NSArrayMImmutable("__NSArrayM_Immutable");
+  static const ConstString g_NSCallStackArray("_NSCallStackArray");
 
   if (class_name.IsEmpty())
     return false;
 
   if (class_name == g_NSArrayI) {
     Status error;
     value = process_sp->ReadUnsignedIntegerFromMemory(valobj_addr + ptr_size,
                                                       ptr_size, 0, error);
if (class_name == g_NSArrayI) {
     value = process_sp->ReadUnsignedIntegerFromMemory(valobj_addr + ptr_size,
                                                       ptr_size, 0, error);
     if (error.Fail())
       return false;
   } else if (class_name == g_NSArray0) {
     value = 0;
   } else if (class_name == g_NSArray1) {
     value = 1;
-  } else if (class_name == g_NSArrayCF) {
+  } else if (class_name == g_NSArrayCF || class_name == g_NSCallStackArray) {
+    // __NSCFArray and _NSCallStackArray store the number of elements as a
+    // pointer-sized value at offset `2 * ptr_size`.
     Status error;
     value = process_sp->ReadUnsignedIntegerFromMemory(
         valobj_addr + 2 * ptr_size, ptr_size, 0, error);
     if (error.Fail())
       return false;
   } else {
     auto &map(NSArray_Additionals::GetAdditionalSummaries());
     auto iter = map.find(class_name), end = map.end();
     if (iter != end)
       return iter->second(valobj, stream, options);
     else
       return false;
   }
 
   std::string prefix, suffix;
   if (Language *language = Language::FindPlugin(options.GetLanguage())) {
     if (!language->GetFormatterPrefixSuffix(valobj, g_TypeHint, prefix,
                                             suffix)) {
       prefix.clear();
lldb_private::formatters::NSArraySyntheticFrontEndCreator(
   static const ConstString g_NSArrayI("__NSArrayI");
   static const ConstString g_NSArrayI_Transfer("__NSArrayI_Transfer");
   static const ConstString g_NSFrozenArrayM("__NSFrozenArrayM");
   static const ConstString g_NSArrayM("__NSArrayM");
   static const ConstString g_NSArray0("__NSArray0");
   static const ConstString g_NSArray1("__NSSingleObjectArrayI");
   static const ConstString g_NSArrayMLegacy("__NSArrayM_Legacy");
   static const ConstString g_NSArrayMImmutable("__NSArrayM_Immutable");
+  static const ConstString g_NSCallStackArray("_NSCallStackArray");
 
   if (class_name.IsEmpty())
     return nullptr;
 
   if (class_name == g_NSArrayI) {
     if (runtime->GetFoundationVersion() >= 1436)
       return (new Foundation1436::NSArrayISyntheticFrontEnd(valobj_sp));
     if (runtime->GetFoundationVersion() >= 1430)
if (class_name == g_NSArrayI) {
     if (runtime->GetFoundationVersion() >= 1437)
       return (new Foundation1437::NSArrayMSyntheticFrontEnd(valobj_sp));
     if (runtime->GetFoundationVersion() >= 1428)
       return (new Foundation1428::NSArrayMSyntheticFrontEnd(valobj_sp));
     if (runtime->GetFoundationVersion() >= 1100)
       return (new Foundation1010::NSArrayMSyntheticFrontEnd(valobj_sp));
     else
       return (new Foundation109::NSArrayMSyntheticFrontEnd(valobj_sp));
+  } else if (class_name == g_NSCallStackArray) {
+    return (new CallStackArray::NSCallStackArraySyntheticFrontEnd(valobj_sp));
   } else {
     auto &map(NSArray_Additionals::GetAdditionalSynthetics());
     auto iter = map.find(class_name), end = map.end();
     if (iter != end)
       return iter->second(synth, valobj_sp);
   }
 
   return nullptr;
 }

source/Plugins/Language/ObjC/ObjCLanguage.cpp

#ifndef LLDB_DISABLE_PYTHON
   AddCXXSummary(
       objc_category_sp, lldb_private::formatters::NSArraySummaryProvider,
       "NSArray summary provider", ConstString("__NSArrayM"), appkit_flags);
   AddCXXSummary(
       objc_category_sp, lldb_private::formatters::NSArraySummaryProvider,
       "NSArray summary provider", ConstString("__NSCFArray"), appkit_flags);
   AddCXXSummary(
       objc_category_sp, lldb_private::formatters::NSArraySummaryProvider,
+      "NSArray summary provider", ConstString("_NSCallStackArray"), appkit_flags);
+  AddCXXSummary(
+      objc_category_sp, lldb_private::formatters::NSArraySummaryProvider,
       "NSArray summary provider", ConstString("CFArrayRef"), appkit_flags);
   AddCXXSummary(objc_category_sp,
                 lldb_private::formatters::NSArraySummaryProvider,
                 "NSArray summary provider", ConstString("CFMutableArrayRef"),
                 appkit_flags);
 
   AddCXXSummary(objc_category_sp,
                 lldb_private::formatters::NSDictionarySummaryProvider<false>,
AddCXXSynthetic(objc_category_sp,
                   "NSArray synthetic children", ConstString("NSMutableArray"),
                   ScriptedSyntheticChildren::Flags());
   AddCXXSynthetic(objc_category_sp,
                   lldb_private::formatters::NSArraySyntheticFrontEndCreator,
                   "NSArray synthetic children", ConstString("__NSCFArray"),
                   ScriptedSyntheticChildren::Flags());
   AddCXXSynthetic(objc_category_sp,
                   lldb_private::formatters::NSArraySyntheticFrontEndCreator,
+                  "NSArray synthetic children", ConstString("_NSCallStackArray"),
+                  ScriptedSyntheticChildren::Flags());
+  AddCXXSynthetic(objc_category_sp,
+                  lldb_private::formatters::NSArraySyntheticFrontEndCreator,
                   "NSArray synthetic children",
                   ConstString("CFMutableArrayRef"),
                   ScriptedSyntheticChildren::Flags());
   AddCXXSynthetic(objc_category_sp,
                   lldb_private::formatters::NSArraySyntheticFrontEndCreator,
                   "NSArray synthetic children", ConstString("CFArrayRef"),
                   ScriptedSyntheticChildren::Flags());