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# pahole command for gdb
# Copyright (C) 2008, 2009, 2012 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
class Pahole (gdb.Command):
"""Show the holes in a structure.
This command takes a single argument, a type name.
It prints the type and displays comments showing where holes are."""
def __init__ (self):
super (Pahole, self).__init__ ("pahole", gdb.COMMAND_NONE,
gdb.COMPLETE_SYMBOL)
def maybe_print_hole(self, bitpos, field_bitpos):
if bitpos != field_bitpos:
hole = field_bitpos - bitpos
print ' /* XXX %d bit hole, try to pack */' % hole
def pahole (self, type, level, name):
if name is None:
name = ''
tag = type.tag
if tag is None:
tag = ''
print '%sstruct %s {' % (' ' * (2 * level), tag)
bitpos = 0
for field in type.fields ():
# Skip static fields.
if not hasattr (field, ('bitpos')):
continue
ftype = field.type.strip_typedefs()
self.maybe_print_hole(bitpos, field.bitpos)
bitpos = field.bitpos
if field.bitsize > 0:
fieldsize = field.bitsize
else:
# TARGET_CHAR_BIT here...
fieldsize = 8 * ftype.sizeof
# TARGET_CHAR_BIT
print ' /* %3d %3d */' % (int (bitpos / 8), int (fieldsize / 8)),
bitpos = bitpos + fieldsize
if ftype.code == gdb.TYPE_CODE_STRUCT:
self.pahole (ftype, level + 1, field.name)
else:
print ' ' * (2 + 2 * level),
print '%s %s' % (str (ftype), field.name)
if level == 0:
self.maybe_print_hole(bitpos, 8 * type.sizeof)
print ' ' * (14 + 2 * level),
print '} %s' % name
def invoke (self, arg, from_tty):
type = gdb.lookup_type (arg)
type = type.strip_typedefs ()
if type.code != gdb.TYPE_CODE_STRUCT:
raise TypeError, '%s is not a struct type' % arg
print ' ' * 14,
self.pahole (type, 0, '')
Pahole()
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