Tuesday 3 December 2013

Linux/Ubuntu Eclipse CDT pretty printer, better view of STL objects during debugging

Eclipse CDT pretty printer is very useful for viewing STL objects in debug mode, just add the following text into any file (usually ~/.gdbinit or /etc/gdb/gdbinit) and add that file into "Debug configuration->Debugger->Main->GDB command file" will do (add the following text starting from the 1st word 'python', inclusive):

python

# Pretty-printers for libstc++.

# Copyright (C) 2008-2013 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 itertools
import re

# Try to use the new-style pretty-printing if available.
_use_gdb_pp = True
try:
    import gdb.printing
except ImportError:
    _use_gdb_pp = False

# Try to install type-printers.
_use_type_printing = False
try:
    import gdb.types
    if hasattr(gdb.types, 'TypePrinter'):
        _use_type_printing = True
except ImportError:
    pass

# Starting with the type ORIG, search for the member type NAME.  This
# handles searching upward through superclasses.  This is needed to
# work around http://sourceware.org/bugzilla/show_bug.cgi?id=13615.
def find_type(orig, name):
    typ = orig.strip_typedefs()
    while True:
        search = str(typ) + '::' + name
        try:
            return gdb.lookup_type(search)
        except RuntimeError:
            pass
        # The type was not found, so try the superclass.  We only need
        # to check the first superclass, so we don't bother with
        # anything fancier here.
        field = typ.fields()[0]
        if not field.is_base_class:
            raise ValueError( "Cannot find type %s::%s" % (str(orig), name))
        typ = field.type

class SharedPointerPrinter:
    "Print a shared_ptr or weak_ptr"

    def __init__ (self, typename, val):
        self.typename = typename
        self.val = val

    def to_string (self):
        state = 'empty'
        refcounts = self.val['_M_refcount']['_M_pi']
        if refcounts != 0:
            usecount = refcounts['_M_use_count']
            weakcount = refcounts['_M_weak_count']
            if usecount == 0:
                state = 'expired, weak %d' % weakcount
            else:
                state = 'count %d, weak %d' % (usecount, weakcount - 1)
        return '%s (%s) %s' % (self.typename, state, self.val['_M_ptr'])

class UniquePointerPrinter:
    "Print a unique_ptr"

    def __init__ (self, typename, val):
        self.val = val

    def to_string (self):
        v = self.val['_M_t']['_M_head_impl']
        return ('std::unique_ptr<%s> containing %s' % (str(v.type.target()),
                                                       str(v)))

class StdListPrinter:
    "Print a std::list"

    class _iterator:
        def __init__(self, nodetype, head):
            self.nodetype = nodetype
            self.base = head['_M_next']
            self.head = head.address
            self.count = 0

        def __iter__(self):
            return self

        def next(self):
            if self.base == self.head:
                raise StopIteration
            elt = self.base.cast(self.nodetype).dereference()
            self.base = elt['_M_next']
            count = self.count
            self.count = self.count + 1
            return ('[%d]' % count, elt['_M_data'])

    def __init__(self, typename, val):
        self.typename = typename
        self.val = val

    def children(self):
        nodetype = find_type(self.val.type, '_Node')
        nodetype = nodetype.strip_typedefs().pointer()
        return self._iterator(nodetype, self.val['_M_impl']['_M_node'])

    def to_string(self):
        if self.val['_M_impl']['_M_node'].address == self.val['_M_impl']['_M_node']['_M_next']:
            return 'empty %s' % (self.typename)
        return '%s' % (self.typename)

class StdListIteratorPrinter:
    "Print std::list::iterator"

    def __init__(self, typename, val):
        self.val = val
        self.typename = typename

    def to_string(self):
        nodetype = find_type(self.val.type, '_Node')
        nodetype = nodetype.strip_typedefs().pointer()
        return self.val['_M_node'].cast(nodetype).dereference()['_M_data']

class StdSlistPrinter:
    "Print a __gnu_cxx::slist"

    class _iterator:
        def __init__(self, nodetype, head):
            self.nodetype = nodetype
            self.base = head['_M_head']['_M_next']
            self.count = 0

        def __iter__(self):
            return self

        def next(self):
            if self.base == 0:
                raise StopIteration
            elt = self.base.cast(self.nodetype).dereference()
            self.base = elt['_M_next']
            count = self.count
            self.count = self.count + 1
            return ('[%d]' % count, elt['_M_data'])

    def __init__(self, typename, val):
        self.val = val

    def children(self):
        nodetype = find_type(self.val.type, '_Node')
        nodetype = nodetype.strip_typedefs().pointer()
        return self._iterator(nodetype, self.val)

    def to_string(self):
        if self.val['_M_head']['_M_next'] == 0:
            return 'empty __gnu_cxx::slist'
        return '__gnu_cxx::slist'

class StdSlistIteratorPrinter:
    "Print __gnu_cxx::slist::iterator"

    def __init__(self, typename, val):
        self.val = val

    def to_string(self):
        nodetype = find_type(self.val.type, '_Node')
        nodetype = nodetype.strip_typedefs().pointer()
        return self.val['_M_node'].cast(nodetype).dereference()['_M_data']

class StdVectorPrinter:
    "Print a std::vector"

    class _iterator:
        def __init__ (self, start, finish, bitvec):
            self.bitvec = bitvec
            if bitvec:
                self.item   = start['_M_p']
                self.so     = start['_M_offset']
                self.finish = finish['_M_p']
                self.fo     = finish['_M_offset']
                itype = self.item.dereference().type
                self.isize = 8 * itype.sizeof
            else:
                self.item = start
                self.finish = finish
            self.count = 0

        def __iter__(self):
            return self

        def next(self):
            count = self.count
            self.count = self.count + 1
            if self.bitvec:
                if self.item == self.finish and self.so >= self.fo:
                    raise StopIteration
                elt = self.item.dereference()
                if elt & (1 << self.so):
                    obit = 1
                else:
                    obit = 0
                self.so = self.so + 1
                if self.so >= self.isize:
                    self.item = self.item + 1
                    self.so = 0
                return ('[%d]' % count, obit)
            else:
                if self.item == self.finish:
                    raise StopIteration
                elt = self.item.dereference()
                self.item = self.item + 1
                return ('[%d]' % count, elt)

    def __init__(self, typename, val):
        self.typename = typename
        self.val = val
        self.is_bool = val.type.template_argument(0).code  == gdb.TYPE_CODE_BOOL

    def children(self):
        return self._iterator(self.val['_M_impl']['_M_start'],
                              self.val['_M_impl']['_M_finish'],
                              self.is_bool)

    def to_string(self):
        start = self.val['_M_impl']['_M_start']
        finish = self.val['_M_impl']['_M_finish']
        end = self.val['_M_impl']['_M_end_of_storage']
        if self.is_bool:
            start = self.val['_M_impl']['_M_start']['_M_p']
            so    = self.val['_M_impl']['_M_start']['_M_offset']
            finish = self.val['_M_impl']['_M_finish']['_M_p']
            fo     = self.val['_M_impl']['_M_finish']['_M_offset']
            itype = start.dereference().type
            bl = 8 * itype.sizeof
            length   = (bl - so) + bl * ((finish - start) - 1) + fo
            capacity = bl * (end - start)
            return ('%s<bool> of length %d, capacity %d'
                    % (self.typename, int (length), int (capacity)))
        else:
            return ('%s of length %d, capacity %d'
                    % (self.typename, int (finish - start), int (end - start)))

    def display_hint(self):
        return 'array'

class StdVectorIteratorPrinter:
    "Print std::vector::iterator"

    def __init__(self, typename, val):
        self.val = val

    def to_string(self):
        return self.val['_M_current'].dereference()

class StdTuplePrinter:
    "Print a std::tuple"

    class _iterator:
        def __init__ (self, head):
            self.head = head

            # Set the base class as the initial head of the
            # tuple.
            nodes = self.head.type.fields ()
            if len (nodes) == 1:
                # Set the actual head to the first pair.
                self.head  = self.head.cast (nodes[0].type)
            elif len (nodes) != 0:
                raise ValueError( "Top of tuple tree does not consist of a single node.")
            self.count = 0

        def __iter__ (self):
            return self

        def next (self):
            nodes = self.head.type.fields ()
            # Check for further recursions in the inheritance tree.
            if len (nodes) == 0:
                raise StopIteration
            # Check that this iteration has an expected structure.
            if len (nodes) != 2:
                raise ValueError( "Cannot parse more than 2 nodes in a tuple tree.")

            # - Left node is the next recursion parent.
            # - Right node is the actual class contained in the tuple.

            # Process right node.
            impl = self.head.cast (nodes[1].type)

            # Process left node and set it as head.
            self.head  = self.head.cast (nodes[0].type)
            self.count = self.count + 1

            # Finally, check the implementation.  If it is
            # wrapped in _M_head_impl return that, otherwise return
            # the value "as is".
            fields = impl.type.fields ()
            if len (fields) < 1 or fields[0].name != "_M_head_impl":
                return ('[%d]' % self.count, impl)
            else:
                return ('[%d]' % self.count, impl['_M_head_impl'])

    def __init__ (self, typename, val):
        self.typename = typename
        self.val = val;

    def children (self):
        return self._iterator (self.val)

    def to_string (self):
        if len (self.val.type.fields ()) == 0:
            return 'empty %s' % (self.typename)
        return '%s containing' % (self.typename)

class StdStackOrQueuePrinter:
    "Print a std::stack or std::queue"

    def __init__ (self, typename, val):
        self.typename = typename
        self.visualizer = gdb.default_visualizer(val['c'])

    def children (self):
        return self.visualizer.children()

    def to_string (self):
        return '%s wrapping: %s' % (self.typename,
                                    self.visualizer.to_string())

    def display_hint (self):
        if hasattr (self.visualizer, 'display_hint'):
            return self.visualizer.display_hint ()
        return None

class RbtreeIterator:
    def __init__(self, rbtree):
        self.size = rbtree['_M_t']['_M_impl']['_M_node_count']
        self.node = rbtree['_M_t']['_M_impl']['_M_header']['_M_left']
        self.count = 0

    def __iter__(self):
        return self

    def __len__(self):
        return int (self.size)

    def next(self):
        if self.count == self.size:
            raise StopIteration
        result = self.node
        self.count = self.count + 1
        if self.count < self.size:
            # Compute the next node.
            node = self.node
            if node.dereference()['_M_right']:
                node = node.dereference()['_M_right']
                while node.dereference()['_M_left']:
                    node = node.dereference()['_M_left']
            else:
                parent = node.dereference()['_M_parent']
                while node == parent.dereference()['_M_right']:
                    node = parent
                    parent = parent.dereference()['_M_parent']
                if node.dereference()['_M_right'] != parent:
                    node = parent
            self.node = node
        return result

# This is a pretty printer for std::_Rb_tree_iterator (which is
# std::map::iterator), and has nothing to do with the RbtreeIterator
# class above.
class StdRbtreeIteratorPrinter:
    "Print std::map::iterator"

    def __init__ (self, typename, val):
        self.val = val

    def to_string (self):
        typename = str(self.val.type.strip_typedefs()) + '::_Link_type'
        nodetype = gdb.lookup_type(typename).strip_typedefs()
        return self.val.cast(nodetype).dereference()['_M_value_field']

class StdDebugIteratorPrinter:
    "Print a debug enabled version of an iterator"

    def __init__ (self, typename, val):
        self.val = val

    # Just strip away the encapsulating __gnu_debug::_Safe_iterator
    # and return the wrapped iterator value.
    def to_string (self):
        itype = self.val.type.template_argument(0)
        return self.val['_M_current'].cast(itype)

class StdMapPrinter:
    "Print a std::map or std::multimap"

    # Turn an RbtreeIterator into a pretty-print iterator.
    class _iter:
        def __init__(self, rbiter, type):
            self.rbiter = rbiter
            self.count = 0
            self.type = type

        def __iter__(self):
            return self

        def next(self):
            if self.count % 2 == 0:
                n = self.rbiter.next()
                n = n.cast(self.type).dereference()['_M_value_field']
                self.pair = n
                item = n['first']
            else:
                item = self.pair['second']
            result = ('[%d]' % self.count, item)
            self.count = self.count + 1
            return result

    def __init__ (self, typename, val):
        self.typename = typename
        self.val = val

    def to_string (self):
        return '%s with %d elements' % (self.typename,
                                        len (RbtreeIterator (self.val)))

    def children (self):
        rep_type = find_type(self.val.type, '_Rep_type')
        node = find_type(rep_type, '_Link_type')
        node = node.strip_typedefs()
        return self._iter (RbtreeIterator (self.val), node)

    def display_hint (self):
        return 'map'

class StdSetPrinter:
    "Print a std::set or std::multiset"

    # Turn an RbtreeIterator into a pretty-print iterator.
    class _iter:
        def __init__(self, rbiter, type):
            self.rbiter = rbiter
            self.count = 0
            self.type = type

        def __iter__(self):
            return self

        def next(self):
            item = self.rbiter.next()
            item = item.cast(self.type).dereference()['_M_value_field']
            # FIXME: this is weird ... what to do?
            # Maybe a 'set' display hint?
            result = ('[%d]' % self.count, item)
            self.count = self.count + 1
            return result

    def __init__ (self, typename, val):
        self.typename = typename
        self.val = val

    def to_string (self):
        return '%s with %d elements' % (self.typename,
                                        len (RbtreeIterator (self.val)))

    def children (self):
        rep_type = find_type(self.val.type, '_Rep_type')
        node = find_type(rep_type, '_Link_type')
        node = node.strip_typedefs()
        return self._iter (RbtreeIterator (self.val), node)

class StdBitsetPrinter:
    "Print a std::bitset"

    def __init__(self, typename, val):
        self.typename = typename
        self.val = val

    def to_string (self):
        # If template_argument handled values, we could print the
        # size.  Or we could use a regexp on the type.
        return '%s' % (self.typename)

    def children (self):
        words = self.val['_M_w']
        wtype = words.type

        # The _M_w member can be either an unsigned long, or an
        # array.  This depends on the template specialization used.
        # If it is a single long, convert to a single element list.
        if wtype.code == gdb.TYPE_CODE_ARRAY:
            tsize = wtype.target ().sizeof
        else:
            words = [words]
            tsize = wtype.sizeof

        nwords = wtype.sizeof / tsize
        result = []
        byte = 0
        while byte < nwords:
            w = words[byte]
            bit = 0
            while w != 0:
                if (w & 1) != 0:
                    # Another spot where we could use 'set'?
                    result.append(('[%d]' % (byte * tsize * 8 + bit), 1))
                bit = bit + 1
                w = w >> 1
            byte = byte + 1
        return result

class StdDequePrinter:
    "Print a std::deque"

    class _iter:
        def __init__(self, node, start, end, last, buffer_size):
            self.node = node
            self.p = start
            self.end = end
            self.last = last
            self.buffer_size = buffer_size
            self.count = 0

        def __iter__(self):
            return self

        def next(self):
            if self.p == self.last:
                raise StopIteration

            result = ('[%d]' % self.count, self.p.dereference())
            self.count = self.count + 1

            # Advance the 'cur' pointer.
            self.p = self.p + 1
            if self.p == self.end:
                # If we got to the end of this bucket, move to the
                # next bucket.
                self.node = self.node + 1
                self.p = self.node[0]
                self.end = self.p + self.buffer_size

            return result

    def __init__(self, typename, val):
        self.typename = typename
        self.val = val
        self.elttype = val.type.template_argument(0)
        size = self.elttype.sizeof
        if size < 512:
            self.buffer_size = int (512 / size)
        else:
            self.buffer_size = 1

    def to_string(self):
        start = self.val['_M_impl']['_M_start']
        end = self.val['_M_impl']['_M_finish']

        delta_n = end['_M_node'] - start['_M_node'] - 1
        delta_s = start['_M_last'] - start['_M_cur']
        delta_e = end['_M_cur'] - end['_M_first']

        size = self.buffer_size * delta_n + delta_s + delta_e

        return '%s with %d elements' % (self.typename, long (size))

    def children(self):
        start = self.val['_M_impl']['_M_start']
        end = self.val['_M_impl']['_M_finish']
        return self._iter(start['_M_node'], start['_M_cur'], start['_M_last'],
                          end['_M_cur'], self.buffer_size)

    def display_hint (self):
        return 'array'

class StdDequeIteratorPrinter:
    "Print std::deque::iterator"

    def __init__(self, typename, val):
        self.val = val

    def to_string(self):
        return self.val['_M_cur'].dereference()

class StdStringPrinter:
    "Print a std::basic_string of some kind"

    def __init__(self, typename, val):
        self.val = val

    def to_string(self):
        # Make sure &string works, too.
        type = self.val.type
        if type.code == gdb.TYPE_CODE_REF:
            type = type.target ()

        # Calculate the length of the string so that to_string returns
        # the string according to length, not according to first null
        # encountered.
        ptr = self.val ['_M_dataplus']['_M_p']
        realtype = type.unqualified ().strip_typedefs ()
        reptype = gdb.lookup_type (str (realtype) + '::_Rep').pointer ()
        header = ptr.cast(reptype) - 1
        len = header.dereference ()['_M_length']
        if hasattr(ptr, "lazy_string"):
            return ptr.lazy_string (length = len)
        return ptr.string (length = len)

    def display_hint (self):
        return 'string'

class Tr1HashtableIterator:
    def __init__ (self, hash):
        self.buckets = hash['_M_buckets']
        self.bucket = 0
        self.bucket_count = hash['_M_bucket_count']
        self.node_type = find_type(hash.type, '_Node').pointer()
        self.node = 0
        while self.bucket != self.bucket_count:
            self.node = self.buckets[self.bucket]
            if self.node:
                break
            self.bucket = self.bucket + 1       

    def __iter__ (self):
        return self

    def next (self):
        if self.node == 0:
            raise StopIteration
        node = self.node.cast(self.node_type)
        result = node.dereference()['_M_v']
        self.node = node.dereference()['_M_next'];
        if self.node == 0:
            self.bucket = self.bucket + 1
            while self.bucket != self.bucket_count:
                self.node = self.buckets[self.bucket]
                if self.node:
                    break
                self.bucket = self.bucket + 1
        return result

class StdHashtableIterator:
    def __init__(self, hash):
        self.node = hash['_M_before_begin']['_M_nxt']
        self.node_type = find_type(hash.type, '__node_type').pointer()

    def __iter__(self):
        return self

    def next(self):
        if self.node == 0:
            raise StopIteration
        elt = self.node.cast(self.node_type).dereference()
        self.node = elt['_M_nxt']
        valptr = elt['_M_storage'].address
        valptr = valptr.cast(elt.type.template_argument(0).pointer())
        return valptr.dereference()

class Tr1UnorderedSetPrinter:
    "Print a tr1::unordered_set"

    def __init__ (self, typename, val):
        self.typename = typename
        self.val = val

    def hashtable (self):
        if self.typename.startswith('std::tr1'):
            return self.val
        return self.val['_M_h']

    def to_string (self):
        return '%s with %d elements' % (self.typename, self.hashtable()['_M_element_count'])

    @staticmethod
    def format_count (i):
        return '[%d]' % i

    def children (self):
        counter = itertools.imap (self.format_count, itertools.count())
        if self.typename.startswith('std::tr1'):
            return itertools.izip (counter, Tr1HashtableIterator (self.hashtable()))
        return itertools.izip (counter, StdHashtableIterator (self.hashtable()))

class Tr1UnorderedMapPrinter:
    "Print a tr1::unordered_map"

    def __init__ (self, typename, val):
        self.typename = typename
        self.val = val

    def hashtable (self):
        if self.typename.startswith('std::tr1'):
            return self.val
        return self.val['_M_h']

    def to_string (self):
        return '%s with %d elements' % (self.typename, self.hashtable()['_M_element_count'])

    @staticmethod
    def flatten (list):
        for elt in list:
            for i in elt:
                yield i

    @staticmethod
    def format_one (elt):
        return (elt['first'], elt['second'])

    @staticmethod
    def format_count (i):
        return '[%d]' % i

    def children (self):
        counter = itertools.imap (self.format_count, itertools.count())
        # Map over the hash table and flatten the result.
        if self.typename.startswith('std::tr1'):
            data = self.flatten (itertools.imap (self.format_one, Tr1HashtableIterator (self.hashtable())))
            # Zip the two iterators together.
            return itertools.izip (counter, data)
        data = self.flatten (itertools.imap (self.format_one, StdHashtableIterator (self.hashtable())))
        # Zip the two iterators together.
        return itertools.izip (counter, data)
       

    def display_hint (self):
        return 'map'

class StdForwardListPrinter:
    "Print a std::forward_list"

    class _iterator:
        def __init__(self, nodetype, head):
            self.nodetype = nodetype
            self.base = head['_M_next']
            self.count = 0

        def __iter__(self):
            return self

        def next(self):
            if self.base == 0:
                raise StopIteration
            elt = self.base.cast(self.nodetype).dereference()
            self.base = elt['_M_next']
            count = self.count
            self.count = self.count + 1
            valptr = elt['_M_storage'].address
            valptr = valptr.cast(elt.type.template_argument(0).pointer())
            return ('[%d]' % count, valptr.dereference())

    def __init__(self, typename, val):
        self.val = val
        self.typename = typename

    def children(self):
        nodetype = find_type(self.val.type, '_Node')
        nodetype = nodetype.strip_typedefs().pointer()
        return self._iterator(nodetype, self.val['_M_impl']['_M_head'])

    def to_string(self):
        if self.val['_M_impl']['_M_head']['_M_next'] == 0:
            return 'empty %s' % (self.typename)
        return '%s' % (self.typename)


# A "regular expression" printer which conforms to the
# "SubPrettyPrinter" protocol from gdb.printing.
class RxPrinter(object):
    def __init__(self, name, function):
        super(RxPrinter, self).__init__()
        self.name = name
        self.function = function
        self.enabled = True

    def invoke(self, value):
        if not self.enabled:
            return None

        if value.type.code == gdb.TYPE_CODE_REF:
            if hasattr(gdb.Value,"referenced_value"):
                value = value.referenced_value()

        return self.function(self.name, value)

# A pretty-printer that conforms to the "PrettyPrinter" protocol from
# gdb.printing.  It can also be used directly as an old-style printer.
class Printer(object):
    def __init__(self, name):
        super(Printer, self).__init__()
        self.name = name
        self.subprinters = []
        self.lookup = {}
        self.enabled = True
        self.compiled_rx = re.compile('^([a-zA-Z0-9_:]+)<.*>$')

    def add(self, name, function):
        # A small sanity check.
        # FIXME
        if not self.compiled_rx.match(name + '<>'):
            raise ValueError( 'libstdc++ programming error: "%s" does not match' % name)
        printer = RxPrinter(name, function)
        self.subprinters.append(printer)
        self.lookup[name] = printer

    # Add a name using _GLIBCXX_BEGIN_NAMESPACE_VERSION.
    def add_version(self, base, name, function):
        self.add(base + name, function)
        self.add(base + '__7::' + name, function)

    # Add a name using _GLIBCXX_BEGIN_NAMESPACE_CONTAINER.
    def add_container(self, base, name, function):
        self.add_version(base, name, function)
        self.add_version(base + '__cxx1998::', name, function)

    @staticmethod
    def get_basic_type(type):
        # If it points to a reference, get the reference.
        if type.code == gdb.TYPE_CODE_REF:
            type = type.target ()

        # Get the unqualified type, stripped of typedefs.
        type = type.unqualified ().strip_typedefs ()

        return type.tag

    def __call__(self, val):
        typename = self.get_basic_type(val.type)
        if not typename:
            return None

        # All the types we match are template types, so we can use a
        # dictionary.
        match = self.compiled_rx.match(typename)
        if not match:
            return None

        basename = match.group(1)

        if val.type.code == gdb.TYPE_CODE_REF:
            if hasattr(gdb.Value,"referenced_value"):
                val = val.referenced_value()

        if basename in self.lookup:
            return self.lookup[basename].invoke(val)

        # Cannot find a pretty printer.  Return None.
        return None

libstdcxx_printer = None

class FilteringTypePrinter(object):
    def __init__(self, match, name):
        self.match = match
        self.name = name
        self.enabled = True

    class _recognizer(object):
        def __init__(self, match, name):
            self.match = match
            self.name = name
            self.type_obj = None

        def recognize(self, type_obj):
            if type_obj.tag is None:
                return None

            if self.type_obj is None:
                if not self.match in type_obj.tag:
                    # Filter didn't match.
                    return None
                try:
                    self.type_obj = gdb.lookup_type(self.name).strip_typedefs()
                except:
                    pass
            if self.type_obj == type_obj:
                return self.name
            return None

    def instantiate(self):
        return self._recognizer(self.match, self.name)

def add_one_type_printer(obj, match, name):
    printer = FilteringTypePrinter(match, 'std::' + name)
    gdb.types.register_type_printer(obj, printer)

def register_type_printers(obj):
    global _use_type_printing

    if not _use_type_printing:
        return

    for pfx in ('', 'w'):
        add_one_type_printer(obj, 'basic_string', pfx + 'string')
        add_one_type_printer(obj, 'basic_ios', pfx + 'ios')
        add_one_type_printer(obj, 'basic_streambuf', pfx + 'streambuf')
        add_one_type_printer(obj, 'basic_istream', pfx + 'istream')
        add_one_type_printer(obj, 'basic_ostream', pfx + 'ostream')
        add_one_type_printer(obj, 'basic_iostream', pfx + 'iostream')
        add_one_type_printer(obj, 'basic_stringbuf', pfx + 'stringbuf')
        add_one_type_printer(obj, 'basic_istringstream',
                                 pfx + 'istringstream')
        add_one_type_printer(obj, 'basic_ostringstream',
                                 pfx + 'ostringstream')
        add_one_type_printer(obj, 'basic_stringstream',
                                 pfx + 'stringstream')
        add_one_type_printer(obj, 'basic_filebuf', pfx + 'filebuf')
        add_one_type_printer(obj, 'basic_ifstream', pfx + 'ifstream')
        add_one_type_printer(obj, 'basic_ofstream', pfx + 'ofstream')
        add_one_type_printer(obj, 'basic_fstream', pfx + 'fstream')
        add_one_type_printer(obj, 'basic_regex', pfx + 'regex')
        add_one_type_printer(obj, 'sub_match', pfx + 'csub_match')
        add_one_type_printer(obj, 'sub_match', pfx + 'ssub_match')
        add_one_type_printer(obj, 'match_results', pfx + 'cmatch')
        add_one_type_printer(obj, 'match_results', pfx + 'smatch')
        add_one_type_printer(obj, 'regex_iterator', pfx + 'cregex_iterator')
        add_one_type_printer(obj, 'regex_iterator', pfx + 'sregex_iterator')
        add_one_type_printer(obj, 'regex_token_iterator',
                                 pfx + 'cregex_token_iterator')
        add_one_type_printer(obj, 'regex_token_iterator',
                                 pfx + 'sregex_token_iterator')

    # Note that we can't have a printer for std::wstreampos, because
    # it shares the same underlying type as std::streampos.
    add_one_type_printer(obj, 'fpos', 'streampos')
    add_one_type_printer(obj, 'basic_string', 'u16string')
    add_one_type_printer(obj, 'basic_string', 'u32string')

    for dur in ('nanoseconds', 'microseconds', 'milliseconds',
                'seconds', 'minutes', 'hours'):
        add_one_type_printer(obj, 'duration', dur)

    add_one_type_printer(obj, 'linear_congruential_engine', 'minstd_rand0')
    add_one_type_printer(obj, 'linear_congruential_engine', 'minstd_rand')
    add_one_type_printer(obj, 'mersenne_twister_engine', 'mt19937')
    add_one_type_printer(obj, 'mersenne_twister_engine', 'mt19937_64')
    add_one_type_printer(obj, 'subtract_with_carry_engine', 'ranlux24_base')
    add_one_type_printer(obj, 'subtract_with_carry_engine', 'ranlux48_base')
    add_one_type_printer(obj, 'discard_block_engine', 'ranlux24')
    add_one_type_printer(obj, 'discard_block_engine', 'ranlux48')
    add_one_type_printer(obj, 'shuffle_order_engine', 'knuth_b')

def register_libstdcxx_printers (obj):
    "Register libstdc++ pretty-printers with objfile Obj."

    global _use_gdb_pp
    global libstdcxx_printer

    if _use_gdb_pp:
        gdb.printing.register_pretty_printer(obj, libstdcxx_printer)
    else:
        if obj is None:
            obj = gdb
        obj.pretty_printers.append(libstdcxx_printer)

    register_type_printers(obj)

def build_libstdcxx_dictionary ():
    global libstdcxx_printer

    libstdcxx_printer = Printer("libstdc++-v6")

    # For _GLIBCXX_BEGIN_NAMESPACE_VERSION.
    vers = '(__7::)?'
    # For _GLIBCXX_BEGIN_NAMESPACE_CONTAINER.
    container = '(__cxx1998::' + vers + ')?'

    # libstdc++ objects requiring pretty-printing.
    # In order from:
    # http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/a01847.html
    libstdcxx_printer.add_version('std::', 'basic_string', StdStringPrinter)
    libstdcxx_printer.add_container('std::', 'bitset', StdBitsetPrinter)
    libstdcxx_printer.add_container('std::', 'deque', StdDequePrinter)
    libstdcxx_printer.add_container('std::', 'list', StdListPrinter)
    libstdcxx_printer.add_container('std::', 'map', StdMapPrinter)
    libstdcxx_printer.add_container('std::', 'multimap', StdMapPrinter)
    libstdcxx_printer.add_container('std::', 'multiset', StdSetPrinter)
    libstdcxx_printer.add_version('std::', 'priority_queue',
                                  StdStackOrQueuePrinter)
    libstdcxx_printer.add_version('std::', 'queue', StdStackOrQueuePrinter)
    libstdcxx_printer.add_version('std::', 'tuple', StdTuplePrinter)
    libstdcxx_printer.add_container('std::', 'set', StdSetPrinter)
    libstdcxx_printer.add_version('std::', 'stack', StdStackOrQueuePrinter)
    libstdcxx_printer.add_version('std::', 'unique_ptr', UniquePointerPrinter)
    libstdcxx_printer.add_container('std::', 'vector', StdVectorPrinter)
    # vector<bool>

    # Printer registrations for classes compiled with -D_GLIBCXX_DEBUG.
    libstdcxx_printer.add('std::__debug::bitset', StdBitsetPrinter)
    libstdcxx_printer.add('std::__debug::deque', StdDequePrinter)
    libstdcxx_printer.add('std::__debug::list', StdListPrinter)
    libstdcxx_printer.add('std::__debug::map', StdMapPrinter)
    libstdcxx_printer.add('std::__debug::multimap', StdMapPrinter)
    libstdcxx_printer.add('std::__debug::multiset', StdSetPrinter)
    libstdcxx_printer.add('std::__debug::priority_queue',
                          StdStackOrQueuePrinter)
    libstdcxx_printer.add('std::__debug::queue', StdStackOrQueuePrinter)
    libstdcxx_printer.add('std::__debug::set', StdSetPrinter)
    libstdcxx_printer.add('std::__debug::stack', StdStackOrQueuePrinter)
    libstdcxx_printer.add('std::__debug::unique_ptr', UniquePointerPrinter)
    libstdcxx_printer.add('std::__debug::vector', StdVectorPrinter)

    # These are the TR1 and C++0x printers.
    # For array - the default GDB pretty-printer seems reasonable.
    libstdcxx_printer.add_version('std::', 'shared_ptr', SharedPointerPrinter)
    libstdcxx_printer.add_version('std::', 'weak_ptr', SharedPointerPrinter)
    libstdcxx_printer.add_container('std::', 'unordered_map',
                                    Tr1UnorderedMapPrinter)
    libstdcxx_printer.add_container('std::', 'unordered_set',
                                    Tr1UnorderedSetPrinter)
    libstdcxx_printer.add_container('std::', 'unordered_multimap',
                                    Tr1UnorderedMapPrinter)
    libstdcxx_printer.add_container('std::', 'unordered_multiset',
                                    Tr1UnorderedSetPrinter)
    libstdcxx_printer.add_container('std::', 'forward_list',
                                    StdForwardListPrinter)

    libstdcxx_printer.add_version('std::tr1::', 'shared_ptr', SharedPointerPrinter)
    libstdcxx_printer.add_version('std::tr1::', 'weak_ptr', SharedPointerPrinter)
    libstdcxx_printer.add_version('std::tr1::', 'unordered_map',
                                  Tr1UnorderedMapPrinter)
    libstdcxx_printer.add_version('std::tr1::', 'unordered_set',
                                  Tr1UnorderedSetPrinter)
    libstdcxx_printer.add_version('std::tr1::', 'unordered_multimap',
                                  Tr1UnorderedMapPrinter)
    libstdcxx_printer.add_version('std::tr1::', 'unordered_multiset',
                                  Tr1UnorderedSetPrinter)

    # These are the C++0x printer registrations for -D_GLIBCXX_DEBUG cases.
    # The tr1 namespace printers do not seem to have any debug
    # equivalents, so do no register them.
    libstdcxx_printer.add('std::__debug::unordered_map',
                          Tr1UnorderedMapPrinter)
    libstdcxx_printer.add('std::__debug::unordered_set',
                          Tr1UnorderedSetPrinter)
    libstdcxx_printer.add('std::__debug::unordered_multimap',
                          Tr1UnorderedMapPrinter)
    libstdcxx_printer.add('std::__debug::unordered_multiset',
                          Tr1UnorderedSetPrinter)
    libstdcxx_printer.add('std::__debug::forward_list',
                          StdForwardListPrinter)


    # Extensions.
    libstdcxx_printer.add_version('__gnu_cxx::', 'slist', StdSlistPrinter)

    if True:
        # These shouldn't be necessary, if GDB "print *i" worked.
        # But it often doesn't, so here they are.
        libstdcxx_printer.add_container('std::', '_List_iterator',
                                        StdListIteratorPrinter)
        libstdcxx_printer.add_container('std::', '_List_const_iterator',
                                        StdListIteratorPrinter)
        libstdcxx_printer.add_version('std::', '_Rb_tree_iterator',
                                      StdRbtreeIteratorPrinter)
        libstdcxx_printer.add_version('std::', '_Rb_tree_const_iterator',
                                      StdRbtreeIteratorPrinter)
        libstdcxx_printer.add_container('std::', '_Deque_iterator',
                                        StdDequeIteratorPrinter)
        libstdcxx_printer.add_container('std::', '_Deque_const_iterator',
                                        StdDequeIteratorPrinter)
        libstdcxx_printer.add_version('__gnu_cxx::', '__normal_iterator',
                                      StdVectorIteratorPrinter)
        libstdcxx_printer.add_version('__gnu_cxx::', '_Slist_iterator',
                                      StdSlistIteratorPrinter)

        # Debug (compiled with -D_GLIBCXX_DEBUG) printer
        # registrations.  The Rb_tree debug iterator when unwrapped
        # from the encapsulating __gnu_debug::_Safe_iterator does not
        # have the __norm namespace. Just use the existing printer
        # registration for that.
        libstdcxx_printer.add('__gnu_debug::_Safe_iterator',
                              StdDebugIteratorPrinter)
        libstdcxx_printer.add('std::__norm::_List_iterator',
                              StdListIteratorPrinter)
        libstdcxx_printer.add('std::__norm::_List_const_iterator',
                              StdListIteratorPrinter)
        libstdcxx_printer.add('std::__norm::_Deque_const_iterator',
                              StdDequeIteratorPrinter)
        libstdcxx_printer.add('std::__norm::_Deque_iterator',
                              StdDequeIteratorPrinter)

build_libstdcxx_dictionary ()

register_libstdcxx_printers (None)