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 not _list_uses_loop_detector:
            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 is 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) * \
                element_type.GetByteSize()
            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 is 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