llvm-project/lldb/examples/synthetic/gnu_libstdcpp.py

import re
import lldb.formatters.Logger

# C++ STL formatters for LLDB
# These formatters are based upon the version of the GNU libstdc++
# as it ships with Mac OS X 10.6.8 thru 10.8.0
# You are encouraged to look at the STL implementation for your platform
# before relying on these formatters to do the right thing for your setup

class StdListSynthProvider:

	def __init__(self, valobj, dict):
		logger = lldb.formatters.Logger.Logger()
		self.valobj = valobj
		self.count = None
		logger >> "Providing synthetic children for a list named " + str(valobj.GetName())

	def next_node(self,node):
		logger = lldb.formatters.Logger.Logger()
		return node.GetChildMemberWithName('_M_next')

	def is_valid(self,node):
		logger = lldb.formatters.Logger.Logger()
		valid = self.value(self.next_node(node)) != self.node_address
		if valid:
			logger >> "%s is valid" % str(self.valobj.GetName())
		else:
			logger >> "synthetic value is not valid"
		return valid

	def value(self,node):
		logger = lldb.formatters.Logger.Logger()
		value = node.GetValueAsUnsigned()
		logger >> "synthetic value for {}: {}".format(str(self.valobj.GetName()), value)
		return value

	# Floyd's cycle-finding algorithm
	# try to detect if this list has a loop
	def has_loop(self):
		global _list_uses_loop_detector
		logger = lldb.formatters.Logger.Logger()
		if _list_uses_loop_detector == False:
			logger >> "Asked not to use loop detection"
			return False
		slow = self.next
		fast1 = self.next
		fast2 = self.next
		while self.is_valid(slow):
			slow_value = self.value(slow)
			fast1 = self.next_node(fast2)
			fast2 = self.next_node(fast1)
			if self.value(fast1) == slow_value or self.value(fast2) == slow_value:
				return True
			slow = self.next_node(slow)
		return False

	def num_children(self):
		logger = lldb.formatters.Logger.Logger()
		if self.count is None:
			# libstdc++ 6.0.21 added dedicated count field.
			count_child = self.node.GetChildMemberWithName('_M_data')
			if count_child and count_child.IsValid():
				self.count = count_child.GetValueAsUnsigned(0)
			if self.count is None:
				self.count = self.num_children_impl()
		return self.count

	def num_children_impl(self):
		logger = lldb.formatters.Logger.Logger()
		try:
			next_val = self.next.GetValueAsUnsigned(0)
			prev_val = self.prev.GetValueAsUnsigned(0)
			# After a std::list has been initialized, both next and prev will be non-NULL
			if next_val == 0 or prev_val == 0:
				return 0
			if next_val == self.node_address:
				return 0
			if next_val == prev_val:
				return 1
			if self.has_loop():
				return 0
			size = 2
			current = self.next
			while current.GetChildMemberWithName('_M_next').GetValueAsUnsigned(0) != self.node_address:
				size = size + 1
				current = current.GetChildMemberWithName('_M_next')
			return (size - 1)
		except:
			return 0;

	def get_child_index(self,name):
		logger = lldb.formatters.Logger.Logger()
		try:
			return int(name.lstrip('[').rstrip(']'))
		except:
			return -1

	def get_child_at_index(self,index):
		logger = lldb.formatters.Logger.Logger()
		logger >> "Fetching child " + str(index)
		if index < 0:
			return None;
		if index >= self.num_children():
			return None;
		try:
			offset = index
			current = self.next
			while offset > 0:
				current = current.GetChildMemberWithName('_M_next')
				offset = offset - 1
			return current.CreateChildAtOffset('['+str(index)+']',2*current.GetType().GetByteSize(),self.data_type)
		except:
			return None

	def extract_type(self):
		logger = lldb.formatters.Logger.Logger()
		list_type = self.valobj.GetType().GetUnqualifiedType()
		if list_type.IsReferenceType():
			list_type = list_type.GetDereferencedType()
		if list_type.GetNumberOfTemplateArguments() > 0:
			data_type = list_type.GetTemplateArgumentType(0)
		else:
			data_type = None
		return data_type

	def update(self):
		logger = lldb.formatters.Logger.Logger()
		# preemptively setting this to None - we might end up changing our mind later
		self.count = None
		try:
			impl = self.valobj.GetChildMemberWithName('_M_impl')
			self.node = impl.GetChildMemberWithName('_M_node')
			self.node_address = self.valobj.AddressOf().GetValueAsUnsigned(0)
			self.next = self.node.GetChildMemberWithName('_M_next')
			self.prev = self.node.GetChildMemberWithName('_M_prev')
			self.data_type = self.extract_type()
			self.data_size = self.data_type.GetByteSize()
		except:
			pass

	def has_children(self):
		return True

class StdVectorSynthProvider:

	class StdVectorImplementation(object):
		def __init__(self, valobj):
			self.valobj = valobj
			self.count = None

		def num_children(self):
			if self.count == None:
				self.count = self.num_children_impl()
			return self.count

		def num_children_impl(self):
			try:
				start_val = self.start.GetValueAsUnsigned(0)
				finish_val = self.finish.GetValueAsUnsigned(0)
				end_val  = self.end.GetValueAsUnsigned(0)
				# Before a vector has been constructed, it will contain bad values
				# so we really need to be careful about the length we return since
				# uninitialized data can cause us to return a huge number. We need
				# to also check for any of the start, finish or end of storage values
				# being zero (NULL). If any are, then this vector has not been
				# initialized yet and we should return zero

				# Make sure nothing is NULL
				if start_val == 0 or finish_val == 0 or end_val == 0:
					return 0
				# Make sure start is less than finish
				if start_val >= finish_val:
					return 0
				# Make sure finish is less than or equal to end of storage
				if finish_val > end_val:
					return 0

				# if we have a struct (or other data type that the compiler pads to native word size)
				# this check might fail, unless the sizeof() we get is itself incremented to take the
				# padding bytes into account - on current clang it looks like this is the case
				num_children = (finish_val-start_val)
				if (num_children % self.data_size) != 0:
					return 0
				else:
					num_children = num_children/self.data_size
				return num_children
			except:
				return 0;

		def get_child_at_index(self, index):
			logger = lldb.formatters.Logger.Logger()
			logger >> "Retrieving child " + str(index)
			if index < 0:
				return None;
			if index >= self.num_children():
				return None;
			try:
				offset = index * self.data_size
				return self.start.CreateChildAtOffset('['+str(index)+']',offset,self.data_type)
			except:
				return None

		def update(self):
			# preemptively setting this to None - we might end up changing our mind later
			self.count = None
			try:
				impl = self.valobj.GetChildMemberWithName('_M_impl')
				self.start = impl.GetChildMemberWithName('_M_start')
				self.finish = impl.GetChildMemberWithName('_M_finish')
				self.end = impl.GetChildMemberWithName('_M_end_of_storage')
				self.data_type = self.start.GetType().GetPointeeType()
				self.data_size = self.data_type.GetByteSize()
				# if any of these objects is invalid, it means there is no point in trying to fetch anything
				if self.start.IsValid() and self.finish.IsValid() and self.end.IsValid() and self.data_type.IsValid():
					self.count = None
				else:
					self.count = 0
			except:
				pass
			return True

	class StdVBoolImplementation(object):
		def __init__(self, valobj, bool_type):
			self.valobj = valobj
			self.bool_type = bool_type
			self.valid = False

		def num_children(self):
			if self.valid:
				start = self.start_p.GetValueAsUnsigned(0)
				finish = self.finish_p.GetValueAsUnsigned(0)
				offset = self.offset.GetValueAsUnsigned(0)
				if finish >= start:
					return (finish - start) * 8 + offset
			return 0

		def get_child_at_index(self, index):
			if index >= self.num_children():
				return None
			element_type = self.start_p.GetType().GetPointeeType()
			element_bits = 8 * element_type.GetByteSize()
			element_offset = index / element_bits
			bit_offset = index % element_bits
			element = self.start_p.CreateChildAtOffset('['+str(index)+']',element_offset,element_type)
			bit = element.GetValueAsUnsigned(0) & (1 << bit_offset)
			if bit != 0:
				value_expr = "(bool)true"
			else:
				value_expr = "(bool)false"
			return self.valobj.CreateValueFromExpression("[%d]" % index, value_expr)

		def update(self):
			try:
				m_impl = self.valobj.GetChildMemberWithName('_M_impl')
				self.m_start = m_impl.GetChildMemberWithName('_M_start')
				self.m_finish = m_impl.GetChildMemberWithName('_M_finish')
				self.start_p = self.m_start.GetChildMemberWithName('_M_p')
				self.finish_p = self.m_finish.GetChildMemberWithName('_M_p')
				self.offset = self.m_finish.GetChildMemberWithName('_M_offset')
				self.valid = True
			except:
				self.valid = False
			return True

	def __init__(self, valobj, dict):
		logger = lldb.formatters.Logger.Logger()
		first_template_arg_type = valobj.GetType().GetTemplateArgumentType(0)
		if str(first_template_arg_type.GetName()) == "bool":
			self.impl = self.StdVBoolImplementation(valobj, first_template_arg_type)
		else:
			self.impl = self.StdVectorImplementation(valobj)
		logger >> "Providing synthetic children for a vector named " + str(valobj.GetName())

	def num_children(self):
		return self.impl.num_children()

	def get_child_index(self,name):
		try:
			return int(name.lstrip('[').rstrip(']'))
		except:
			return -1

	def get_child_at_index(self, index):
		return self.impl.get_child_at_index(index)

	def update(self):
		return self.impl.update()

	def has_children(self):
		return True


class StdMapSynthProvider:

	def __init__(self, valobj, dict):
		logger = lldb.formatters.Logger.Logger()
		self.valobj = valobj;
		self.count = None
		logger >> "Providing synthetic children for a map named " + str(valobj.GetName())
		
	# we need this function as a temporary workaround for rdar://problem/10801549
	# which prevents us from extracting the std::pair<K,V> SBType out of the template
	# arguments for _Rep_Type _M_t in the map itself - because we have to make up the
	# typename and then find it, we may hit the situation were std::string has multiple
	# names but only one is actually referenced in the debug information. hence, we need
	# to replace the longer versions of std::string with the shorter one in order to be able
	# to find the type name
	def fixup_class_name(self, class_name):
		logger = lldb.formatters.Logger.Logger()
		if class_name == 'std::basic_string<char, std::char_traits<char>, std::allocator<char> >':
			return 'std::basic_string<char>',True
		if class_name == 'basic_string<char, std::char_traits<char>, std::allocator<char> >':
			return 'std::basic_string<char>',True
		if class_name == 'std::basic_string<char, std::char_traits<char>, std::allocator<char> >':
			return 'std::basic_string<char>',True
		if class_name == 'basic_string<char, std::char_traits<char>, std::allocator<char> >':
			return 'std::basic_string<char>',True
		return class_name,False

	def update(self):
		logger = lldb.formatters.Logger.Logger()
		# preemptively setting this to None - we might end up changing our mind later
		self.count = None
		try:
			# we will set this to True if we find out that discovering a node in the map takes more steps than the overall size of the RB tree
			# if this gets set to True, then we will merrily return None for any child from that moment on
			self.garbage = False
			self.Mt = self.valobj.GetChildMemberWithName('_M_t')
			self.Mimpl = self.Mt.GetChildMemberWithName('_M_impl')
			self.Mheader = self.Mimpl.GetChildMemberWithName('_M_header')
			
			map_type = self.valobj.GetType()
			if map_type.IsReferenceType():
				logger >> "Dereferencing type"
				map_type = map_type.GetDereferencedType()

			# Get the type of std::pair<key, value>. It is the first template
			# argument type of the 4th template argument to std::map.
			allocator_type = map_type.GetTemplateArgumentType(3)
			self.data_type = allocator_type.GetTemplateArgumentType(0)
			if not self.data_type:
				# GCC does not emit DW_TAG_template_type_parameter for
				# std::allocator<...>. For such a case, get the type of
				# std::pair from a member of std::map.
				rep_type = self.valobj.GetChildMemberWithName('_M_t').GetType()
				self.data_type = rep_type.GetTypedefedType().GetTemplateArgumentType(1)
			
			# from libstdc++ implementation of _M_root for rbtree
			self.Mroot = self.Mheader.GetChildMemberWithName('_M_parent')
			self.data_size = self.data_type.GetByteSize()
			self.skip_size = self.Mheader.GetType().GetByteSize()
		except:
			pass

	def num_children(self):
		logger = lldb.formatters.Logger.Logger()
		if self.count == None:
			self.count = self.num_children_impl()
		return self.count

	def num_children_impl(self):
		logger = lldb.formatters.Logger.Logger()
		try:
			root_ptr_val = self.node_ptr_value(self.Mroot)
			if root_ptr_val == 0:
				return 0;
			count = self.Mimpl.GetChildMemberWithName('_M_node_count').GetValueAsUnsigned(0)
			logger >> "I have " + str(count) + " children available"
			return count
		except:
			return 0;

	def get_child_index(self,name):
		logger = lldb.formatters.Logger.Logger()
		try:
			return int(name.lstrip('[').rstrip(']'))
		except:
			return -1

	def get_child_at_index(self,index):
		logger = lldb.formatters.Logger.Logger()
		logger >> "Being asked to fetch child[" + str(index) + "]"
		if index < 0:
			return None
		if index >= self.num_children():
			return None;
		if self.garbage:
			logger >> "Returning None since we are a garbage tree"
			return None
		try:
			offset = index
			current = self.left(self.Mheader);
			while offset > 0:
				current = self.increment_node(current)
				offset = offset - 1;
			# skip all the base stuff and get at the data
			return current.CreateChildAtOffset('['+str(index)+']',self.skip_size,self.data_type)
		except:
			return None

	# utility functions
	def node_ptr_value(self,node):
		logger = lldb.formatters.Logger.Logger()
		return node.GetValueAsUnsigned(0)

	def right(self,node):
		logger = lldb.formatters.Logger.Logger()
		return node.GetChildMemberWithName("_M_right");

	def left(self,node):
		logger = lldb.formatters.Logger.Logger()
		return node.GetChildMemberWithName("_M_left");

	def parent(self,node):
		logger = lldb.formatters.Logger.Logger()
		return node.GetChildMemberWithName("_M_parent");

	# from libstdc++ implementation of iterator for rbtree
	def increment_node(self,node):
		logger = lldb.formatters.Logger.Logger()
		max_steps = self.num_children()
		if self.node_ptr_value(self.right(node)) != 0:
			x = self.right(node);
			max_steps -= 1
			while self.node_ptr_value(self.left(x)) != 0:
				x = self.left(x);
				max_steps -= 1
				logger >> str(max_steps) + " more to go before giving up"
				if max_steps <= 0:
					self.garbage = True
					return None
			return x;
		else:
			x = node;
			y = self.parent(x)
			max_steps -= 1
			while(self.node_ptr_value(x) == self.node_ptr_value(self.right(y))):
				x = y;
				y = self.parent(y);
				max_steps -= 1
				logger >> str(max_steps) + " more to go before giving up"
				if max_steps <= 0:
					self.garbage = True
					return None
			if self.node_ptr_value(self.right(x)) != self.node_ptr_value(y):
				x = y;
			return x;

	def has_children(self):
		return True

_list_uses_loop_detector = True