<rdar://problem/12523238> Commit 2 of 3

Adding the new has_children (or MightHaveChildren() in C++) for the existing synthetic children providers
In a few cases, the new call is going to be much more efficient than the previous num_children > 0 check
When the optimization was marginal (e.g. std::vector<>), the choice was to use num_children in order to keep
implementation details in one function instead of duplicating code

Next step is to provide test cases

llvm-svn: 166506

lldb/examples/synthetic/bitfield/example.py

@@ -13,6 +13,12 @@ class MaskedData_SyntheticChildrenProvider:
 		# answer questions about N children
 		return 4
 
+	def has_children(self):
+		# we simply say True here because we know we have 4 children
+		# in general, you want to make this calculation as simple as possible
+		# and return True if in doubt (you can always return num_children == 0 later)
+		return True
+
 	def get_child_index(self,name): 
 		# given a name, return its index
 		# you can return None if you don't know the answer for a given name

lldb/examples/synthetic/gnu_libstdcpp.py

@@ -132,6 +132,27 @@ class StdListSynthProvider:
 		except:
 			pass
 
+	def has_children(self):
+		logger = lldb.formatters.Logger.Logger()
+		if self.count == None:
+			self.update ()
+			try:
+				next_val = self.next.GetValueAsUnsigned(0)
+				prev_val = self.prev.GetValueAsUnsigned(0)
+				if next_val == 0 or prev_val == 0:
+					return False
+				if next_val == self.node_address:
+					return False
+				# skip all the advanced logic to detect the exact count of children
+				# in the interest of speed from this point on, we MIGHT have children
+				# our loop detection logic will still make nothing show up :)
+				return True
+			except:
+				return False
+		if self.count == 0:
+			return False
+		return True
+
 class StdVectorSynthProvider:
 
 	def __init__(self, valobj, dict):
@@ -225,6 +246,10 @@ class StdVectorSynthProvider:
 				self.count = 0
 		except:
 			pass
+			
+
+	def has_children(self):
+		return self.num_children() > 0
 
 
 class StdMapSynthProvider:
@@ -408,6 +433,8 @@ class StdMapSynthProvider:
 				x = y;
 			return x;
 
+	def has_children(self):
+		return self.num_children() > 0
 
 _map_capping_size = 255
 _list_capping_size = 255

lldb/examples/synthetic/libcxx.py

@@ -124,6 +124,10 @@ class stdvector_SynthProvider:
 		except:
 			pass
 
+	def has_children(self):
+		# retrieving the count is quick enough on a std::vector
+		return self.num_children() > 0
+
 # Just an example: the actual summary is produced by a summary string: size=${svar%#}
 def stdvector_SummaryProvider(valobj,dict):
 	prov = stdvector_SynthProvider(valobj,None)
@@ -317,6 +321,28 @@ class stdlist_SynthProvider:
 		except:
 			pass
 
+	def has_children(self):
+		logger = lldb.formatters.Logger.Logger()
+		if self.count == None:
+			self.update()
+			try:
+				next_val = self.head.GetValueAsUnsigned(0)
+				prev_val = self.tail.GetValueAsUnsigned(0)
+				if next_val == 0 or prev_val == 0:
+					return False
+				if next_val == self.node_address:
+					return False
+				# skip all the advanced logic to detect the exact count of children
+				# in the interest of speed from this point on, we MIGHT have children
+				# our loop detection logic will still make nothing show up :)
+				return True
+			except:
+				return 0;
+		if self.count == 0:
+			return False
+		return True
+
+
 # Just an example: the actual summary is produced by a summary string: size=${svar%#}
 def stdlist_SummaryProvider(valobj,dict):
 	prov = stdlist_SynthProvider(valobj,None)
@@ -477,6 +503,9 @@ class stdmap_SynthProvider:
 		except:
 			return 0;
 
+	def has_children(self):
+		return self.num_children_impl() > 0
+
 	def get_data_type(self):
 		logger = lldb.formatters.Logger.Logger()
 		if self.data_type == None or self.data_size == None:
@@ -599,6 +628,11 @@ class stddeque_SynthProvider:
             return 0
         return min(self.count, _deque_capping_size)
 
+    def has_children(self):
+        if self.cont is None:
+            self.update()
+        return self.count > 0
+
     def get_child_index(self,name):
         logger = lldb.formatters.Logger.Logger()
         try:
@@ -702,6 +736,9 @@ class stdsharedptr_SynthProvider:
     def num_children(self):
         return 1
 
+    def has_children(self):
+        return True
+
     def get_child_index(self,name):
         if name=="__ptr_":
             return 0

lldb/source/Core/CXXFormatterFunctions.cpp

@@ -776,7 +776,9 @@ lldb_private::formatters::NSArrayMSyntheticFrontEnd::Update()
 bool
 lldb_private::formatters::NSArrayMSyntheticFrontEnd::MightHaveChildren ()
 {
-    return CalculateNumChildren() > 0;
+    if (!m_data_32 && !m_data_64)
+        Update ();
+    return CalculateNumChildren();
 }
 
 static uint32_t
@@ -891,7 +893,9 @@ lldb_private::formatters::NSArrayISyntheticFrontEnd::Update()
 bool
 lldb_private::formatters::NSArrayISyntheticFrontEnd::MightHaveChildren ()
 {
-    return CalculateNumChildren() > 0;
+    if (!m_data_ptr)
+        Update ();
+    return CalculateNumChildren();
 }
 
 lldb::ValueObjectSP
@@ -1186,7 +1190,9 @@ lldb_private::formatters::NSDictionaryISyntheticFrontEnd::Update()
 bool
 lldb_private::formatters::NSDictionaryISyntheticFrontEnd::MightHaveChildren ()
 {
-    return CalculateNumChildren() > 0;
+    if (!m_data_32 && !m_data_64)
+        Update ();
+    return CalculateNumChildren();
 }
 
 lldb::ValueObjectSP
@@ -1333,7 +1339,9 @@ lldb_private::formatters::NSDictionaryMSyntheticFrontEnd::Update()
 bool
 lldb_private::formatters::NSDictionaryMSyntheticFrontEnd::MightHaveChildren ()
 {
-    return CalculateNumChildren() > 0;
+    if (!m_data_32 && !m_data_64)
+        Update ();
+    return CalculateNumChildren();
 }
 
 lldb::ValueObjectSP