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Current Directory: /usr/share/gcc-8/python/libstdcxx/v6
Viewing File: /usr/share/gcc-8/python/libstdcxx/v6/xmethods.py
# Xmethods for libstdc++.

# Copyright (C) 2014-2025 Free Software Foundation, Inc.

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import gdb
import gdb.xmethod
import re

matcher_name_prefix = 'libstdc++::'


def get_bool_type():
    return gdb.lookup_type('bool')

def get_std_size_type():
    return gdb.lookup_type('std::size_t')

_versioned_namespace = '__8::'

def is_specialization_of(x, template_name):
    """
    Test whether a type is a specialization of the named class template.
    The type can be specified as a string or a gdb.Type object.
    The template should be the name of a class template as a string,
    without any 'std' qualification.
    """
    if isinstance(x, gdb.Type):
        x = x.tag
    template_name = '(%s)?%s' % (_versioned_namespace, template_name)
    return re.match(r'^std::(__\d::)?%s<.*>$' % template_name, x) is not None

class LibStdCxxXMethod(gdb.xmethod.XMethod):
    def __init__(self, name, worker_class):
        gdb.xmethod.XMethod.__init__(self, name)
        self.worker_class = worker_class

# Xmethods for std::array


class ArrayWorkerBase(gdb.xmethod.XMethodWorker):
    def __init__(self, val_type, size):
        self._val_type = val_type
        self._size = size

    def null_value(self):
        nullptr = gdb.parse_and_eval('(void *) 0')
        return nullptr.cast(self._val_type.pointer()).dereference()


class ArraySizeWorker(ArrayWorkerBase):
    def __init__(self, val_type, size):
        ArrayWorkerBase.__init__(self, val_type, size)

    def get_arg_types(self):
        return None

    def get_result_type(self, obj):
        return get_std_size_type()

    def __call__(self, obj):
        return self._size


class ArrayEmptyWorker(ArrayWorkerBase):
    def __init__(self, val_type, size):
        ArrayWorkerBase.__init__(self, val_type, size)

    def get_arg_types(self):
        return None

    def get_result_type(self, obj):
        return get_bool_type()

    def __call__(self, obj):
        return (int(self._size) == 0)


class ArrayFrontWorker(ArrayWorkerBase):
    def __init__(self, val_type, size):
        ArrayWorkerBase.__init__(self, val_type, size)

    def get_arg_types(self):
        return None

    def get_result_type(self, obj):
        return self._val_type

    def __call__(self, obj):
        if int(self._size) > 0:
            return obj['_M_elems'][0]
        else:
            return self.null_value()


class ArrayBackWorker(ArrayWorkerBase):
    def __init__(self, val_type, size):
        ArrayWorkerBase.__init__(self, val_type, size)

    def get_arg_types(self):
        return None

    def get_result_type(self, obj):
        return self._val_type

    def __call__(self, obj):
        if int(self._size) > 0:
            return obj['_M_elems'][self._size - 1]
        else:
            return self.null_value()


class ArrayAtWorker(ArrayWorkerBase):
    def __init__(self, val_type, size):
        ArrayWorkerBase.__init__(self, val_type, size)

    def get_arg_types(self):
        return get_std_size_type()

    def get_result_type(self, obj, index):
        return self._val_type

    def __call__(self, obj, index):
        if int(index) >= int(self._size):
            raise IndexError('Array index "%d" should not be >= %d.' %
                             ((int(index), self._size)))
        return obj['_M_elems'][index]


class ArraySubscriptWorker(ArrayWorkerBase):
    def __init__(self, val_type, size):
        ArrayWorkerBase.__init__(self, val_type, size)

    def get_arg_types(self):
        return get_std_size_type()

    def get_result_type(self, obj, index):
        return self._val_type

    def __call__(self, obj, index):
        if int(self._size) > 0:
            return obj['_M_elems'][index]
        else:
            return self.null_value()


class ArrayMethodsMatcher(gdb.xmethod.XMethodMatcher):
    def __init__(self):
        gdb.xmethod.XMethodMatcher.__init__(self,
                                            matcher_name_prefix + 'array')
        self._method_dict = {
            'size': LibStdCxxXMethod('size', ArraySizeWorker),
            'empty': LibStdCxxXMethod('empty', ArrayEmptyWorker),
            'front': LibStdCxxXMethod('front', ArrayFrontWorker),
            'back': LibStdCxxXMethod('back', ArrayBackWorker),
            'at': LibStdCxxXMethod('at', ArrayAtWorker),
            'operator[]': LibStdCxxXMethod('operator[]', ArraySubscriptWorker),
        }
        self.methods = [self._method_dict[m] for m in self._method_dict]

    def match(self, class_type, method_name):
        if not is_specialization_of(class_type, 'array'):
            return None
        method = self._method_dict.get(method_name)
        if method is None or not method.enabled:
            return None
        try:
            value_type = class_type.template_argument(0)
            size = class_type.template_argument(1)
        except:
            return None
        return method.worker_class(value_type, size)


# Xmethods for std::deque


class DequeWorkerBase(gdb.xmethod.XMethodWorker):
    def __init__(self, val_type):
        self._val_type = val_type
        self._bufsize = 512 // val_type.sizeof or 1

    def size(self, obj):
        start = obj['_M_impl']['_M_start']
        finish = obj['_M_impl']['_M_finish']
        if start['_M_cur'] == finish['_M_cur']:
            return 0
        return (self._bufsize
                * (finish['_M_node'] - start['_M_node'] - 1)
                + (finish['_M_cur'] - finish['_M_first'])
                + (start['_M_last'] - start['_M_cur']))

    def index(self, obj, idx):
        start = obj['_M_impl']['_M_start']
        first_node_size = start['_M_last'] - start['_M_cur']
        if idx < first_node_size:
            return start['_M_cur'][idx]
        idx = idx - first_node_size
        index_node = start['_M_node'][1 + int(idx) // self._bufsize]
        return index_node[idx % self._bufsize]


class DequeEmptyWorker(DequeWorkerBase):
    def get_arg_types(self):
        return None

    def get_result_type(self, obj):
        return get_bool_type()

    def __call__(self, obj):
        return (obj['_M_impl']['_M_start']['_M_cur'] ==
                obj['_M_impl']['_M_finish']['_M_cur'])


class DequeSizeWorker(DequeWorkerBase):
    def get_arg_types(self):
        return None

    def get_result_type(self, obj):
        return get_std_size_type()

    def __call__(self, obj):
        return self.size(obj)


class DequeFrontWorker(DequeWorkerBase):
    def get_arg_types(self):
        return None

    def get_result_type(self, obj):
        return self._val_type

    def __call__(self, obj):
        return obj['_M_impl']['_M_start']['_M_cur'][0]


class DequeBackWorker(DequeWorkerBase):
    def get_arg_types(self):
        return None

    def get_result_type(self, obj):
        return self._val_type

    def __call__(self, obj):
        if (obj['_M_impl']['_M_finish']['_M_cur'] ==
                obj['_M_impl']['_M_finish']['_M_first']):
            prev_node = obj['_M_impl']['_M_finish']['_M_node'] - 1
            return prev_node[0][self._bufsize - 1]
        else:
            return obj['_M_impl']['_M_finish']['_M_cur'][-1]


class DequeSubscriptWorker(DequeWorkerBase):
    def get_arg_types(self):
        return get_std_size_type()

    def get_result_type(self, obj, subscript):
        return self._val_type

    def __call__(self, obj, subscript):
        return self.index(obj, subscript)


class DequeAtWorker(DequeWorkerBase):
    def get_arg_types(self):
        return get_std_size_type()

    def get_result_type(self, obj, index):
        return self._val_type

    def __call__(self, obj, index):
        deque_size = int(self.size(obj))
        if int(index) >= deque_size:
            raise IndexError('Deque index "%d" should not be >= %d.' %
                             (int(index), deque_size))
        else:
            return self.index(obj, index)


class DequeMethodsMatcher(gdb.xmethod.XMethodMatcher):
    def __init__(self):
        gdb.xmethod.XMethodMatcher.__init__(self,
                                            matcher_name_prefix + 'deque')
        self._method_dict = {
            'empty': LibStdCxxXMethod('empty', DequeEmptyWorker),
            'size': LibStdCxxXMethod('size', DequeSizeWorker),
            'front': LibStdCxxXMethod('front', DequeFrontWorker),
            'back': LibStdCxxXMethod('back', DequeBackWorker),
            'operator[]': LibStdCxxXMethod('operator[]', DequeSubscriptWorker),
            'at': LibStdCxxXMethod('at', DequeAtWorker)
        }
        self.methods = [self._method_dict[m] for m in self._method_dict]

    def match(self, class_type, method_name):
        if not is_specialization_of(class_type, 'deque'):
            return None
        method = self._method_dict.get(method_name)
        if method is None or not method.enabled:
            return None
        return method.worker_class(class_type.template_argument(0))

# Xmethods for std::forward_list


class ForwardListWorkerBase(gdb.xmethod.XMethodMatcher):
    def __init__(self, val_type, node_type):
        self._val_type = val_type
        self._node_type = node_type

    def get_arg_types(self):
        return None


class ForwardListEmptyWorker(ForwardListWorkerBase):
    def get_result_type(self, obj):
        return get_bool_type()

    def __call__(self, obj):
        return obj['_M_impl']['_M_head']['_M_next'] == 0


class ForwardListFrontWorker(ForwardListWorkerBase):
    def get_result_type(self, obj):
        return self._val_type

    def __call__(self, obj):
        node = obj['_M_impl']['_M_head']['_M_next'].cast(self._node_type)
        val_address = node['_M_storage']['_M_storage'].address
        return val_address.cast(self._val_type.pointer()).dereference()


class ForwardListMethodsMatcher(gdb.xmethod.XMethodMatcher):
    def __init__(self):
        matcher_name = matcher_name_prefix + 'forward_list'
        gdb.xmethod.XMethodMatcher.__init__(self, matcher_name)
        self._method_dict = {
            'empty': LibStdCxxXMethod('empty', ForwardListEmptyWorker),
            'front': LibStdCxxXMethod('front', ForwardListFrontWorker)
        }
        self.methods = [self._method_dict[m] for m in self._method_dict]

    def match(self, class_type, method_name):
        if not is_specialization_of(class_type, 'forward_list'):
            return None
        method = self._method_dict.get(method_name)
        if method is None or not method.enabled:
            return None
        val_type = class_type.template_argument(0)
        node_type = gdb.lookup_type(str(class_type) + '::_Node').pointer()
        return method.worker_class(val_type, node_type)

# Xmethods for std::list


class ListWorkerBase(gdb.xmethod.XMethodWorker):
    def __init__(self, val_type, node_type):
        self._val_type = val_type
        self._node_type = node_type

    def get_arg_types(self):
        return None

    def get_value_from_node(self, node):
        node = node.dereference()
        if node.type.fields()[1].name == '_M_data':
            # C++03 implementation, node contains the value as a member
            return node['_M_data']
        # C++11 implementation, node stores value in __aligned_membuf
        addr = node['_M_storage'].address
        return addr.cast(self._val_type.pointer()).dereference()


class ListEmptyWorker(ListWorkerBase):
    def get_result_type(self, obj):
        return get_bool_type()

    def __call__(self, obj):
        base_node = obj['_M_impl']['_M_node']
        if base_node['_M_next'] == base_node.address:
            return True
        else:
            return False


class ListSizeWorker(ListWorkerBase):
    def get_result_type(self, obj):
        return get_std_size_type()

    def __call__(self, obj):
        begin_node = obj['_M_impl']['_M_node']['_M_next']
        end_node = obj['_M_impl']['_M_node'].address
        size = 0
        while begin_node != end_node:
            begin_node = begin_node['_M_next']
            size += 1
        return size


class ListFrontWorker(ListWorkerBase):
    def get_result_type(self, obj):
        return self._val_type

    def __call__(self, obj):
        node = obj['_M_impl']['_M_node']['_M_next'].cast(self._node_type)
        return self.get_value_from_node(node)


class ListBackWorker(ListWorkerBase):
    def get_result_type(self, obj):
        return self._val_type

    def __call__(self, obj):
        prev_node = obj['_M_impl']['_M_node']['_M_prev'].cast(self._node_type)
        return self.get_value_from_node(prev_node)


class ListMethodsMatcher(gdb.xmethod.XMethodMatcher):
    def __init__(self):
        gdb.xmethod.XMethodMatcher.__init__(self,
                                            matcher_name_prefix + 'list')
        self._method_dict = {
            'empty': LibStdCxxXMethod('empty', ListEmptyWorker),
            'size': LibStdCxxXMethod('size', ListSizeWorker),
            'front': LibStdCxxXMethod('front', ListFrontWorker),
            'back': LibStdCxxXMethod('back', ListBackWorker)
        }
        self.methods = [self._method_dict[m] for m in self._method_dict]

    def match(self, class_type, method_name):
        if not is_specialization_of(class_type, '(__cxx11::)?list'):
            return None
        method = self._method_dict.get(method_name)
        if method is None or not method.enabled:
            return None
        val_type = class_type.template_argument(0)
        node_type = gdb.lookup_type(str(class_type) + '::_Node').pointer()
        return method.worker_class(val_type, node_type)

# Xmethods for std::vector


class VectorWorkerBase(gdb.xmethod.XMethodWorker):
    def __init__(self, val_type):
        self._val_type = val_type

    def size(self, obj):
        if self._val_type.code == gdb.TYPE_CODE_BOOL:
            start = obj['_M_impl']['_M_start']['_M_p']
            finish = obj['_M_impl']['_M_finish']['_M_p']
            finish_offset = obj['_M_impl']['_M_finish']['_M_offset']
            bit_size = start.dereference().type.sizeof * 8
            return (finish - start) * bit_size + finish_offset
        else:
            return obj['_M_impl']['_M_finish'] - obj['_M_impl']['_M_start']

    def get(self, obj, index):
        if self._val_type.code == gdb.TYPE_CODE_BOOL:
            start = obj['_M_impl']['_M_start']['_M_p']
            bit_size = start.dereference().type.sizeof * 8
            valp = start + index // bit_size
            offset = index % bit_size
            return (valp.dereference() & (1 << offset)) > 0
        else:
            return obj['_M_impl']['_M_start'][index]


class VectorEmptyWorker(VectorWorkerBase):
    def get_arg_types(self):
        return None

    def get_result_type(self, obj):
        return get_bool_type()

    def __call__(self, obj):
        return int(self.size(obj)) == 0


class VectorSizeWorker(VectorWorkerBase):
    def get_arg_types(self):
        return None

    def get_result_type(self, obj):
        return get_std_size_type()

    def __call__(self, obj):
        return self.size(obj)


class VectorFrontWorker(VectorWorkerBase):
    def get_arg_types(self):
        return None

    def get_result_type(self, obj):
        return self._val_type

    def __call__(self, obj):
        return self.get(obj, 0)


class VectorBackWorker(VectorWorkerBase):
    def get_arg_types(self):
        return None

    def get_result_type(self, obj):
        return self._val_type

    def __call__(self, obj):
        return self.get(obj, int(self.size(obj)) - 1)


class VectorAtWorker(VectorWorkerBase):
    def get_arg_types(self):
        return get_std_size_type()

    def get_result_type(self, obj, index):
        return self._val_type

    def __call__(self, obj, index):
        size = int(self.size(obj))
        if int(index) >= size:
            raise IndexError('Vector index "%d" should not be >= %d.' %
                             ((int(index), size)))
        return self.get(obj, int(index))


class VectorSubscriptWorker(VectorWorkerBase):
    def get_arg_types(self):
        return get_std_size_type()

    def get_result_type(self, obj, subscript):
        return self._val_type

    def __call__(self, obj, subscript):
        return self.get(obj, int(subscript))


class VectorMethodsMatcher(gdb.xmethod.XMethodMatcher):
    def __init__(self):
        gdb.xmethod.XMethodMatcher.__init__(self,
                                            matcher_name_prefix + 'vector')
        self._method_dict = {
            'size': LibStdCxxXMethod('size', VectorSizeWorker),
            'empty': LibStdCxxXMethod('empty', VectorEmptyWorker),
            'front': LibStdCxxXMethod('front', VectorFrontWorker),
            'back': LibStdCxxXMethod('back', VectorBackWorker),
            'at': LibStdCxxXMethod('at', VectorAtWorker),
            'operator[]': LibStdCxxXMethod('operator[]',
                                           VectorSubscriptWorker),
        }
        self.methods = [self._method_dict[m] for m in self._method_dict]

    def match(self, class_type, method_name):
        if not is_specialization_of(class_type, 'vector'):
            return None
        method = self._method_dict.get(method_name)
        if method is None or not method.enabled:
            return None
        return method.worker_class(class_type.template_argument(0))

# Xmethods for associative containers


class AssociativeContainerWorkerBase(gdb.xmethod.XMethodWorker):
    def __init__(self, unordered):
        self._unordered = unordered

    def node_count(self, obj):
        if self._unordered:
            return obj['_M_h']['_M_element_count']
        else:
            return obj['_M_t']['_M_impl']['_M_node_count']

    def get_arg_types(self):
        return None


class AssociativeContainerEmptyWorker(AssociativeContainerWorkerBase):
    def get_result_type(self, obj):
        return get_bool_type()

    def __call__(self, obj):
        return int(self.node_count(obj)) == 0


class AssociativeContainerSizeWorker(AssociativeContainerWorkerBase):
    def get_result_type(self, obj):
        return get_std_size_type()

    def __call__(self, obj):
        return self.node_count(obj)


class AssociativeContainerMethodsMatcher(gdb.xmethod.XMethodMatcher):
    def __init__(self, name):
        gdb.xmethod.XMethodMatcher.__init__(self,
                                            matcher_name_prefix + name)
        self._name = name
        self._method_dict = {
            'size': LibStdCxxXMethod('size', AssociativeContainerSizeWorker),
            'empty': LibStdCxxXMethod('empty',
                                      AssociativeContainerEmptyWorker),
        }
        self.methods = [self._method_dict[m] for m in self._method_dict]

    def match(self, class_type, method_name):
        if not is_specialization_of(class_type, self._name):
            return None
        method = self._method_dict.get(method_name)
        if method is None or not method.enabled:
            return None
        unordered = 'unordered' in self._name
        return method.worker_class(unordered)

# Xmethods for std::unique_ptr


class UniquePtrGetWorker(gdb.xmethod.XMethodWorker):
    """
    Implement std::unique_ptr<T>::get() and std::unique_ptr<T>::operator->().
    """

    def __init__(self, elem_type):
        self._is_array = elem_type.code == gdb.TYPE_CODE_ARRAY
        if self._is_array:
            self._elem_type = elem_type.target()
        else:
            self._elem_type = elem_type

    def get_arg_types(self):
        return None

    def get_result_type(self, obj):
        return self._elem_type.pointer()

    def _supports(self, method_name):
        # operator-> is not supported for unique_ptr<T[]>
        return method_name == 'get' or not self._is_array

    def __call__(self, obj):
        impl_type = obj.dereference().type.fields()[0].type.tag
        # Check for new implementations first:
        if is_specialization_of(impl_type, '__uniq_ptr_(data|impl)'):
            tuple_member = obj['_M_t']['_M_t']
        elif is_specialization_of(impl_type, 'tuple'):
            tuple_member = obj['_M_t']
        else:
            return None
        tuple_impl_type = tuple_member.type.fields()[0].type  # _Tuple_impl
        tuple_head_type = tuple_impl_type.fields()[1].type   # _Head_base
        head_field = tuple_head_type.fields()[0]
        if head_field.name == '_M_head_impl':
            return tuple_member.cast(tuple_head_type)['_M_head_impl']
        elif head_field.is_base_class:
            return tuple_member.cast(head_field.type)
        else:
            return None


class UniquePtrDerefWorker(UniquePtrGetWorker):
    """Implement std::unique_ptr<T>::operator*()."""

    def __init__(self, elem_type):
        UniquePtrGetWorker.__init__(self, elem_type)

    def get_result_type(self, obj):
        return self._elem_type

    def _supports(self, method_name):
        # operator* is not supported for unique_ptr<T[]>
        return not self._is_array

    def __call__(self, obj):
        return UniquePtrGetWorker.__call__(self, obj).dereference()


class UniquePtrSubscriptWorker(UniquePtrGetWorker):
    """Implement std::unique_ptr<T>::operator[](size_t)."""

    def __init__(self, elem_type):
        UniquePtrGetWorker.__init__(self, elem_type)

    def get_arg_types(self):
        return get_std_size_type()

    def get_result_type(self, obj, index):
        return self._elem_type

    def _supports(self, method_name):
        # operator[] is only supported for unique_ptr<T[]>
        return self._is_array

    def __call__(self, obj, index):
        return UniquePtrGetWorker.__call__(self, obj)[index]


class UniquePtrMethodsMatcher(gdb.xmethod.XMethodMatcher):
    def __init__(self):
        gdb.xmethod.XMethodMatcher.__init__(self,
                                            matcher_name_prefix + 'unique_ptr')
        self._method_dict = {
            'get': LibStdCxxXMethod('get', UniquePtrGetWorker),
            'operator->': LibStdCxxXMethod('operator->', UniquePtrGetWorker),
            'operator*': LibStdCxxXMethod('operator*', UniquePtrDerefWorker),
            'operator[]': LibStdCxxXMethod('operator[]', UniquePtrSubscriptWorker),
        }
        self.methods = [self._method_dict[m] for m in self._method_dict]

    def match(self, class_type, method_name):
        if not is_specialization_of(class_type, 'unique_ptr'):
            return None
        method = self._method_dict.get(method_name)
        if method is None or not method.enabled:
            return None
        worker = method.worker_class(class_type.template_argument(0))
        if worker._supports(method_name):
            return worker
        return None

# Xmethods for std::shared_ptr


class SharedPtrGetWorker(gdb.xmethod.XMethodWorker):
    """
    Implements std::shared_ptr<T>::get() and std::shared_ptr<T>::operator->().
    """

    def __init__(self, elem_type):
        self._is_array = elem_type.code == gdb.TYPE_CODE_ARRAY
        if self._is_array:
            self._elem_type = elem_type.target()
        else:
            self._elem_type = elem_type

    def get_arg_types(self):
        return None

    def get_result_type(self, obj):
        return self._elem_type.pointer()

    def _supports(self, method_name):
        # operator-> is not supported for shared_ptr<T[]>
        return method_name == 'get' or not self._is_array

    def __call__(self, obj):
        return obj['_M_ptr']


class SharedPtrDerefWorker(SharedPtrGetWorker):
    """Implement std::shared_ptr<T>::operator*()."""

    def __init__(self, elem_type):
        SharedPtrGetWorker.__init__(self, elem_type)

    def get_result_type(self, obj):
        return self._elem_type

    def _supports(self, method_name):
        # operator* is not supported for shared_ptr<T[]>
        return not self._is_array

    def __call__(self, obj):
        return SharedPtrGetWorker.__call__(self, obj).dereference()


class SharedPtrSubscriptWorker(SharedPtrGetWorker):
    """Implement std::shared_ptr<T>::operator[](size_t)."""

    def __init__(self, elem_type):
        SharedPtrGetWorker.__init__(self, elem_type)

    def get_arg_types(self):
        return get_std_size_type()

    def get_result_type(self, obj, index):
        return self._elem_type

    def _supports(self, method_name):
        # operator[] is only supported for shared_ptr<T[]>
        return self._is_array

    def __call__(self, obj, index):
        # Check bounds if _elem_type is an array of known bound
        m = re.match(r'.*\[(\d+)]$', str(self._elem_type))
        if m and index >= int(m.group(1)):
            raise IndexError('shared_ptr<%s> index "%d" should not be >= %d.' %
                             (self._elem_type, int(index), int(m.group(1))))
        return SharedPtrGetWorker.__call__(self, obj)[index]


class SharedPtrUseCountWorker(gdb.xmethod.XMethodWorker):
    """Implement std::shared_ptr<T>::use_count()."""

    def __init__(self, elem_type):
        pass

    def get_arg_types(self):
        return None

    def get_result_type(self, obj):
        return gdb.lookup_type('long')

    def _supports(self, method_name):
        return True

    def __call__(self, obj):
        refcounts = obj['_M_refcount']['_M_pi']
        return refcounts['_M_use_count'] if refcounts else 0


class SharedPtrUniqueWorker(SharedPtrUseCountWorker):
    """Implement std::shared_ptr<T>::unique()."""

    def __init__(self, elem_type):
        SharedPtrUseCountWorker.__init__(self, elem_type)

    def get_result_type(self, obj):
        return gdb.lookup_type('bool')

    def __call__(self, obj):
        return SharedPtrUseCountWorker.__call__(self, obj) == 1


class SharedPtrMethodsMatcher(gdb.xmethod.XMethodMatcher):
    def __init__(self):
        gdb.xmethod.XMethodMatcher.__init__(self,
                                            matcher_name_prefix + 'shared_ptr')
        self._method_dict = {
            'get': LibStdCxxXMethod('get', SharedPtrGetWorker),
            'operator->': LibStdCxxXMethod('operator->', SharedPtrGetWorker),
            'operator*': LibStdCxxXMethod('operator*', SharedPtrDerefWorker),
            'operator[]': LibStdCxxXMethod('operator[]', SharedPtrSubscriptWorker),
            'use_count': LibStdCxxXMethod('use_count', SharedPtrUseCountWorker),
            'unique': LibStdCxxXMethod('unique', SharedPtrUniqueWorker),
        }
        self.methods = [self._method_dict[m] for m in self._method_dict]

    def match(self, class_type, method_name):
        if not is_specialization_of(class_type, 'shared_ptr'):
            return None
        method = self._method_dict.get(method_name)
        if method is None or not method.enabled:
            return None
        worker = method.worker_class(class_type.template_argument(0))
        if worker._supports(method_name):
            return worker
        return None


def register_libstdcxx_xmethods(locus):
    gdb.xmethod.register_xmethod_matcher(locus, ArrayMethodsMatcher())
    gdb.xmethod.register_xmethod_matcher(locus, ForwardListMethodsMatcher())
    gdb.xmethod.register_xmethod_matcher(locus, DequeMethodsMatcher())
    gdb.xmethod.register_xmethod_matcher(locus, ListMethodsMatcher())
    gdb.xmethod.register_xmethod_matcher(locus, VectorMethodsMatcher())
    gdb.xmethod.register_xmethod_matcher(
        locus, AssociativeContainerMethodsMatcher('set'))
    gdb.xmethod.register_xmethod_matcher(
        locus, AssociativeContainerMethodsMatcher('map'))
    gdb.xmethod.register_xmethod_matcher(
        locus, AssociativeContainerMethodsMatcher('multiset'))
    gdb.xmethod.register_xmethod_matcher(
        locus, AssociativeContainerMethodsMatcher('multimap'))
    gdb.xmethod.register_xmethod_matcher(
        locus, AssociativeContainerMethodsMatcher('unordered_set'))
    gdb.xmethod.register_xmethod_matcher(
        locus, AssociativeContainerMethodsMatcher('unordered_map'))
    gdb.xmethod.register_xmethod_matcher(
        locus, AssociativeContainerMethodsMatcher('unordered_multiset'))
    gdb.xmethod.register_xmethod_matcher(
        locus, AssociativeContainerMethodsMatcher('unordered_multimap'))
    gdb.xmethod.register_xmethod_matcher(locus, UniquePtrMethodsMatcher())
    gdb.xmethod.register_xmethod_matcher(locus, SharedPtrMethodsMatcher())
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