libpython.py

#!/usr/bin/python
'''
From gdb 7 onwards, gdb's build can be configured --with-python, allowing gdb
to be extended with Python code e.g. for library-specific data visualizations,
such as for the C++ STL types. Documentation on this API can be seen at:
http://sourceware.org/gdb/current/onlinedocs/gdb/Python-API.html


This python module deals with the case when the process being debugged (the
"inferior process" in gdb parlance) is itself python, or more specifically,
linked against libpython. In this situation, almost every item of data is a
(PyObject*), and having the debugger merely print their addresses is not very
enlightening.

This module embeds knowledge about the implementation details of libpython so
that we can emit useful visualizations e.g. a string, a list, a dict, a frame
giving file/line information and the state of local variables

In particular, given a gdb.Value corresponding to a PyObject* in the inferior
process, we can generate a "proxy value" within the gdb process. For example,
given a PyObject* in the inferior process that is in fact a PyListObject*
holding three PyObject* that turn out to be PyBytesObject* instances, we can
generate a proxy value within the gdb process that is a list of bytes
instances:
 [b"foo", b"bar", b"baz"]

Doing so can be expensive for complicated graphs of objects, and could take
some time, so we also have a "write_repr" method that writes a representation
of the data to a file-like object. This allows us to stop the traversal by
having the file-like object raise an exception if it gets too much data.

With both "proxyval" and "write_repr" we keep track of the set of all addresses
visited so far in the traversal, to avoid infinite recursion due to cycles in
the graph of object references.

We try to defer gdb.lookup_type() invocations for python types until as late as
possible: for a dynamically linked python binary, when the process starts in
the debugger, the libpython.so hasn't been dynamically loaded yet, so none of
the type names are known to the debugger

The module also extends gdb with some python-specific commands.
'''

importgdb
importos
importlocale
importsys


# Look up the gdb.Type for some standard types:
# Those need to be refreshed as types (pointer sizes) may change when
# gdb loads different executables

def_type_char_ptr():
returngdb.lookup_type('char').pointer() # char*


def_type_unsigned_char_ptr():
returngdb.lookup_type('unsigned char').pointer() # unsigned char*


def_type_unsigned_short_ptr():
returngdb.lookup_type('unsigned short').pointer()


def_type_unsigned_int_ptr():
returngdb.lookup_type('unsigned int').pointer()

def_sizeof_void_p():
returngdb.lookup_type('void').pointer().sizeof

def_sizeof_pyobject():
returngdb.lookup_type('PyObject').sizeof

def_managed_dict_offset():
# See pycore_object.h
pyobj=gdb.lookup_type("PyObject")
ifany(field.name=="ob_ref_local"forfieldinpyobj.fields()):
return-1*_sizeof_void_p()
else:
return-3*_sizeof_void_p()


Py_TPFLAGS_INLINE_VALUES= (1<<2)
Py_TPFLAGS_MANAGED_DICT= (1<<4)
Py_TPFLAGS_HEAPTYPE= (1<<9)
Py_TPFLAGS_LONG_SUBCLASS= (1<<24)
Py_TPFLAGS_LIST_SUBCLASS= (1<<25)
Py_TPFLAGS_TUPLE_SUBCLASS= (1<<26)
Py_TPFLAGS_BYTES_SUBCLASS= (1<<27)
Py_TPFLAGS_UNICODE_SUBCLASS= (1<<28)
Py_TPFLAGS_DICT_SUBCLASS= (1<<29)
Py_TPFLAGS_BASE_EXC_SUBCLASS= (1<<30)
Py_TPFLAGS_TYPE_SUBCLASS= (1<<31)

#From pycore_frame.h
FRAME_OWNED_BY_CSTACK=3

MAX_OUTPUT_LEN=1024

hexdigits="0123456789abcdef"

ENCODING=locale.getpreferredencoding()

FRAME_INFO_OPTIMIZED_OUT='(frame information optimized out)'
UNABLE_READ_INFO_PYTHON_FRAME='Unable to read information on python frame'
EVALFRAME='_PyEval_EvalFrameDefault'

classNullPyObjectPtr(RuntimeError):
pass


defsafety_limit(val):
# Given an integer value from the process being debugged, limit it to some
# safety threshold so that arbitrary breakage within said process doesn't
# break the gdb process too much (e.g. sizes of iterations, sizes of lists)
returnmin(val, 1000)


defsafe_range(val):
# As per range, but don't trust the value too much: cap it to a safety
# threshold in case the data was corrupted
returnrange(safety_limit(int(val)))

classStringTruncated(RuntimeError):
pass

classTruncatedStringIO(object):
'''Similar to io.StringIO, but can truncate the output by raising a
 StringTruncated exception'''
def__init__(self, maxlen=None):
self._val=''
self.maxlen=maxlen

defwrite(self, data):
ifself.maxlen:
iflen(data) +len(self._val) >self.maxlen:
# Truncation:
self._val+=data[0:self.maxlen-len(self._val)]
raiseStringTruncated()

self._val+=data

defgetvalue(self):
returnself._val

classPyObjectPtr(object):
"""
 Class wrapping a gdb.Value that's either a (PyObject*) within the
 inferior process, or some subclass pointer e.g. (PyBytesObject*)

 There will be a subclass for every refined PyObject type that we care
 about.

 Note that at every stage the underlying pointer could be NULL, point
 to corrupt data, etc; this is the debugger, after all.
 """
_typename='PyObject'

def__init__(self, gdbval, cast_to=None):
ifcast_to:
self._gdbval=gdbval.cast(cast_to)
else:
self._gdbval=gdbval

deffield(self, name):
'''
 Get the gdb.Value for the given field within the PyObject.

 Various libpython types are defined using the "PyObject_HEAD" and
 "PyObject_VAR_HEAD" macros.

 In Python, this is defined as an embedded PyVarObject type thus:
 PyVarObject ob_base;
 so that the "ob_size" field is located insize the "ob_base" field, and
 the "ob_type" is most easily accessed by casting back to a (PyObject*).
 '''
ifself.is_null():
raiseNullPyObjectPtr(self)

ifname=='ob_type':
pyo_ptr=self._gdbval.cast(PyObjectPtr.get_gdb_type())
returnpyo_ptr.dereference()[name]

ifname=='ob_size':
pyo_ptr=self._gdbval.cast(PyVarObjectPtr.get_gdb_type())
returnpyo_ptr.dereference()[name]

# General case: look it up inside the object:
returnself._gdbval.dereference()[name]

defpyop_field(self, name):
'''
 Get a PyObjectPtr for the given PyObject* field within this PyObject.
 '''
returnPyObjectPtr.from_pyobject_ptr(self.field(name))

defwrite_field_repr(self, name, out, visited):
'''
 Extract the PyObject* field named "name", and write its representation
 to file-like object "out"
 '''
field_obj=self.pyop_field(name)
field_obj.write_repr(out, visited)

defget_truncated_repr(self, maxlen):
'''
 Get a repr-like string for the data, but truncate it at "maxlen" bytes
 (ending the object graph traversal as soon as you do)
 '''
out=TruncatedStringIO(maxlen)
try:
self.write_repr(out, set())
exceptStringTruncated:
# Truncation occurred:
returnout.getvalue() +'...(truncated)'

# No truncation occurred:
returnout.getvalue()

deftype(self):
returnPyTypeObjectPtr(self.field('ob_type'))

defis_null(self):
return0==int(self._gdbval)

defis_optimized_out(self):
'''
 Is the value of the underlying PyObject* visible to the debugger?

 This can vary with the precise version of the compiler used to build
 Python, and the precise version of gdb.

 See e.g. https://bugzilla.redhat.com/show_bug.cgi?id=556975 with
 PyEval_EvalFrameEx's "f"
 '''
returnself._gdbval.is_optimized_out

defsafe_tp_name(self):
try:
ob_type=self.type()
tp_name=ob_type.field('tp_name')
returntp_name.string()
# NullPyObjectPtr: NULL tp_name?
# RuntimeError: Can't even read the object at all?
# UnicodeDecodeError: Failed to decode tp_name bytestring
except (NullPyObjectPtr, RuntimeError, UnicodeDecodeError):
return'unknown'

defproxyval(self, visited):
'''
 Scrape a value from the inferior process, and try to represent it
 within the gdb process, whilst (hopefully) avoiding crashes when
 the remote data is corrupt.

 Derived classes will override this.

 For example, a PyLongObjectPtr* with long_value 42 in the inferior process
 should result in an int(42) in this process.

 visited: a set of all gdb.Value pyobject pointers already visited
 whilst generating this value (to guard against infinite recursion when
 visiting object graphs with loops). Analogous to Py_ReprEnter and
 Py_ReprLeave
 '''

classFakeRepr(object):
"""
 Class representing a non-descript PyObject* value in the inferior
 process for when we don't have a custom scraper, intended to have
 a sane repr().
 """

def__init__(self, tp_name, address):
self.tp_name=tp_name
self.address=address

def__repr__(self):
# For the NULL pointer, we have no way of knowing a type, so
# special-case it as per
# http://bugs.python.org/issue8032#msg100882
ifself.address==0:
return'0x0'
return'<%s at remote 0x%x>'% (self.tp_name, self.address)

returnFakeRepr(self.safe_tp_name(),
int(self._gdbval))

defwrite_repr(self, out, visited):
'''
 Write a string representation of the value scraped from the inferior
 process to "out", a file-like object.
 '''
# Default implementation: generate a proxy value and write its repr
# However, this could involve a lot of work for complicated objects,
# so for derived classes we specialize this
returnout.write(repr(self.proxyval(visited)))

@classmethod
defsubclass_from_type(cls, t):
'''
 Given a PyTypeObjectPtr instance wrapping a gdb.Value that's a
 (PyTypeObject*), determine the corresponding subclass of PyObjectPtr
 to use

 Ideally, we would look up the symbols for the global types, but that
 isn't working yet:
 (gdb) python print gdb.lookup_symbol('PyList_Type')[0].value
 Traceback (most recent call last):
 File "<string>", line 1, in <module>
 NotImplementedError: Symbol type not yet supported in Python scripts.
 Error while executing Python code.

 For now, we use tp_flags, after doing some string comparisons on the
 tp_name for some special-cases that don't seem to be visible through
 flags
 '''
try:
tp_name=t.field('tp_name').string()
tp_flags=int(t.field('tp_flags'))
# RuntimeError: NULL pointers
# UnicodeDecodeError: string() fails to decode the bytestring
except (RuntimeError, UnicodeDecodeError):
# Handle any kind of error e.g. NULL ptrs by simply using the base
# class
returncls

#print('tp_flags = 0x%08x' % tp_flags)
#print('tp_name = %r' % tp_name)

name_map= {'bool': PyBoolObjectPtr,
'classobj': PyClassObjectPtr,
'NoneType': PyNoneStructPtr,
'frame': PyFrameObjectPtr,
'set' : PySetObjectPtr,
'frozenset' : PySetObjectPtr,
'builtin_function_or_method' : PyCFunctionObjectPtr,
'method-wrapper': wrapperobject,
 }
iftp_nameinname_map:
returnname_map[tp_name]

iftp_flags&Py_TPFLAGS_HEAPTYPE:
returnHeapTypeObjectPtr

iftp_flags&Py_TPFLAGS_LONG_SUBCLASS:
returnPyLongObjectPtr
iftp_flags&Py_TPFLAGS_LIST_SUBCLASS:
returnPyListObjectPtr
iftp_flags&Py_TPFLAGS_TUPLE_SUBCLASS:
returnPyTupleObjectPtr
iftp_flags&Py_TPFLAGS_BYTES_SUBCLASS:
returnPyBytesObjectPtr
iftp_flags&Py_TPFLAGS_UNICODE_SUBCLASS:
returnPyUnicodeObjectPtr
iftp_flags&Py_TPFLAGS_DICT_SUBCLASS:
returnPyDictObjectPtr
iftp_flags&Py_TPFLAGS_BASE_EXC_SUBCLASS:
returnPyBaseExceptionObjectPtr
#if tp_flags & Py_TPFLAGS_TYPE_SUBCLASS:
# return PyTypeObjectPtr

# Use the base class:
returncls

@classmethod
deffrom_pyobject_ptr(cls, gdbval):
'''
 Try to locate the appropriate derived class dynamically, and cast
 the pointer accordingly.
 '''
try:
p=PyObjectPtr(gdbval)
cls=cls.subclass_from_type(p.type())
returncls(gdbval, cast_to=cls.get_gdb_type())
exceptRuntimeError:
# Handle any kind of error e.g. NULL ptrs by simply using the base
# class
pass
returncls(gdbval)

@classmethod
defget_gdb_type(cls):
returngdb.lookup_type(cls._typename).pointer()

defas_address(self):
returnint(self._gdbval)

classPyVarObjectPtr(PyObjectPtr):
_typename='PyVarObject'

classProxyAlreadyVisited(object):
'''
 Placeholder proxy to use when protecting against infinite recursion due to
 loops in the object graph.

 Analogous to the values emitted by the users of Py_ReprEnter and Py_ReprLeave
 '''
def__init__(self, rep):
self._rep=rep

def__repr__(self):
returnself._rep


def_write_instance_repr(out, visited, name, pyop_attrdict, address):
'''Shared code for use by all classes:
 write a representation to file-like object "out"'''
out.write('<')
out.write(name)

# Write dictionary of instance attributes:
ifisinstance(pyop_attrdict, (PyKeysValuesPair, PyDictObjectPtr)):
out.write('(')
first=True
items=pyop_attrdict.iteritems()
forpyop_arg, pyop_valinitems:
ifnotfirst:
out.write(', ')
first=False
out.write(pyop_arg.proxyval(visited))
out.write('=')
pyop_val.write_repr(out, visited)
out.write(')')
out.write(' at remote 0x%x>'%address)


classInstanceProxy(object):

def__init__(self, cl_name, attrdict, address):
self.cl_name=cl_name
self.attrdict=attrdict
self.address=address

def__repr__(self):
ifisinstance(self.attrdict, dict):
kwargs=', '.join(["%s=%r"% (arg, val)
forarg, valinself.attrdict.items()])
return'<%s(%s) at remote 0x%x>'% (self.cl_name,
kwargs, self.address)
else:
return'<%s at remote 0x%x>'% (self.cl_name,
self.address)

def_PyObject_VAR_SIZE(typeobj, nitems):
if_PyObject_VAR_SIZE._type_size_tisNone:
_PyObject_VAR_SIZE._type_size_t=gdb.lookup_type('size_t')

return ( ( typeobj.field('tp_basicsize') +
nitems*typeobj.field('tp_itemsize') +
 (_sizeof_void_p() -1)
 ) &~(_sizeof_void_p() -1)
 ).cast(_PyObject_VAR_SIZE._type_size_t)
_PyObject_VAR_SIZE._type_size_t=None

classHeapTypeObjectPtr(PyObjectPtr):
_typename='PyObject'

defget_attr_dict(self):
'''
 Get the PyDictObject ptr representing the attribute dictionary
 (or None if there's a problem)
 '''
try:
typeobj=self.type()
dictoffset=int_from_int(typeobj.field('tp_dictoffset'))
ifdictoffset!=0:
ifdictoffset<0:
ifint_from_int(typeobj.field('tp_flags')) &Py_TPFLAGS_MANAGED_DICT:
assertdictoffset==-1
dictoffset=_managed_dict_offset()
else:
type_PyVarObject_ptr=gdb.lookup_type('PyVarObject').pointer()
tsize=int_from_int(self._gdbval.cast(type_PyVarObject_ptr)['ob_size'])
iftsize<0:
tsize=-tsize
size=_PyObject_VAR_SIZE(typeobj, tsize)
dictoffset+=size
assertdictoffset%_sizeof_void_p() ==0

dictptr=self._gdbval.cast(_type_char_ptr()) +dictoffset
PyObjectPtrPtr=PyObjectPtr.get_gdb_type().pointer()
dictptr=dictptr.cast(PyObjectPtrPtr)
ifint(dictptr.dereference()) &1:
returnNone
returnPyObjectPtr.from_pyobject_ptr(dictptr.dereference())
exceptRuntimeError:
# Corrupt data somewhere; fail safe
pass

# Not found, or some kind of error:
returnNone

defget_keys_values(self):
typeobj=self.type()
has_values=int_from_int(typeobj.field('tp_flags')) &Py_TPFLAGS_MANAGED_DICT
ifnothas_values:
returnNone
obj_ptr=self._gdbval.cast(_type_char_ptr())
dict_ptr_ptr=obj_ptr+_managed_dict_offset()
dict_ptr=dict_ptr_ptr.cast(_type_char_ptr().pointer()).dereference()
ifint(dict_ptr):
returnNone
char_ptr=obj_ptr+_sizeof_pyobject()
values_ptr=char_ptr.cast(gdb.lookup_type("PyDictValues").pointer())
values=values_ptr['values']
returnPyKeysValuesPair(self.get_cached_keys(), values)

defget_cached_keys(self):
typeobj=self.type()
HeapTypePtr=gdb.lookup_type("PyHeapTypeObject").pointer()
returntypeobj._gdbval.cast(HeapTypePtr)['ht_cached_keys']

defproxyval(self, visited):
'''
 Support for classes.

 Currently we just locate the dictionary using a transliteration to
 python of _PyObject_GetDictPtr, ignoring descriptors
 '''
# Guard against infinite loops:
ifself.as_address() invisited:
returnProxyAlreadyVisited('<...>')
visited.add(self.as_address())

keys_values=self.get_keys_values()
ifkeys_values:
attr_dict=keys_values.proxyval(visited)
else:
pyop_attr_dict=self.get_attr_dict()
ifpyop_attr_dict:
attr_dict=pyop_attr_dict.proxyval(visited)
else:
attr_dict= {}
tp_name=self.safe_tp_name()

# Class:
returnInstanceProxy(tp_name, attr_dict, int(self._gdbval))

defwrite_repr(self, out, visited):
# Guard against infinite loops:
ifself.as_address() invisited:
out.write('<...>')
return
visited.add(self.as_address())

pyop_attrs=self.get_keys_values()
ifnotpyop_attrs:
pyop_attrs=self.get_attr_dict()
_write_instance_repr(out, visited,
self.safe_tp_name(), pyop_attrs, self.as_address())

classProxyException(Exception):
def__init__(self, tp_name, args):
self.tp_name=tp_name
self.args=args

def__repr__(self):
return'%s%r'% (self.tp_name, self.args)

classPyBaseExceptionObjectPtr(PyObjectPtr):
"""
 Class wrapping a gdb.Value that's a PyBaseExceptionObject* i.e. an exception
 within the process being debugged.
 """
_typename='PyBaseExceptionObject'

defproxyval(self, visited):
# Guard against infinite loops:
ifself.as_address() invisited:
returnProxyAlreadyVisited('(...)')
visited.add(self.as_address())
arg_proxy=self.pyop_field('args').proxyval(visited)
returnProxyException(self.safe_tp_name(),
arg_proxy)

defwrite_repr(self, out, visited):
# Guard against infinite loops:
ifself.as_address() invisited:
out.write('(...)')
return
visited.add(self.as_address())

out.write(self.safe_tp_name())
self.write_field_repr('args', out, visited)

classPyClassObjectPtr(PyObjectPtr):
"""
 Class wrapping a gdb.Value that's a PyClassObject* i.e. a <classobj>
 instance within the process being debugged.
 """
_typename='PyClassObject'


classBuiltInFunctionProxy(object):
def__init__(self, ml_name):
self.ml_name=ml_name

def__repr__(self):
return"<built-in function %s>"%self.ml_name

classBuiltInMethodProxy(object):
def__init__(self, ml_name, pyop_m_self):
self.ml_name=ml_name
self.pyop_m_self=pyop_m_self

def__repr__(self):
return ('<built-in method %s of %s object at remote 0x%x>'
% (self.ml_name,
self.pyop_m_self.safe_tp_name(),
self.pyop_m_self.as_address())
 )

classPyCFunctionObjectPtr(PyObjectPtr):
"""
 Class wrapping a gdb.Value that's a PyCFunctionObject*
 (see Include/methodobject.h and Objects/methodobject.c)
 """
_typename='PyCFunctionObject'

defproxyval(self, visited):
m_ml=self.field('m_ml') # m_ml is a (PyMethodDef*)
try:
ml_name=m_ml['ml_name'].string()
exceptUnicodeDecodeError:
ml_name='<ml_name:UnicodeDecodeError>'

pyop_m_self=self.pyop_field('m_self')
ifpyop_m_self.is_null():
returnBuiltInFunctionProxy(ml_name)
else:
returnBuiltInMethodProxy(ml_name, pyop_m_self)

# Python implementation of location table parsing algorithm
defread(it):
returnord(next(it))

defread_varint(it):
b=read(it)
val=b&63;
shift=0;
whileb&64:
b=read(it)
shift+=6
val|= (b&63) <<shift
returnval

defread_signed_varint(it):
uval=read_varint(it)
ifuval&1:
return-(uval>>1)
else:
returnuval>>1

defparse_location_table(firstlineno, linetable):
line=firstlineno
addr=0
it=iter(linetable)
whileTrue:
try:
first_byte=read(it)
exceptStopIteration:
return
code= (first_byte>>3) &15
length= (first_byte&7) +1
end_addr=addr+length
ifcode==15:
yieldaddr, end_addr, None
addr=end_addr
continue
elifcode==14: # Long form
line_delta=read_signed_varint(it)
line+=line_delta
end_line=line+read_varint(it)
col=read_varint(it)
end_col=read_varint(it)
elifcode==13: # No column
line_delta=read_signed_varint(it)
line+=line_delta
elifcodein (10, 11, 12): # new line
line_delta=code-10
line+=line_delta
column=read(it)
end_column=read(it)
else:
assert (0<=code<10)
second_byte=read(it)
column=code<<3| (second_byte>>4)
yieldaddr, end_addr, line
addr=end_addr

classPyCodeObjectPtr(PyObjectPtr):
"""
 Class wrapping a gdb.Value that's a PyCodeObject* i.e. a <code> instance
 within the process being debugged.
 """
_typename='PyCodeObject'

defaddr2line(self, addrq):
'''
 Get the line number for a given bytecode offset

 Analogous to PyCode_Addr2Line; translated from pseudocode in
 Objects/lnotab_notes.txt
 '''
co_linetable=self.pyop_field('co_linetable').proxyval(set())

# Initialize lineno to co_firstlineno as per PyCode_Addr2Line
# not 0, as lnotab_notes.txt has it:
lineno=int_from_int(self.field('co_firstlineno'))

ifaddrq<0:
returnlineno
addr=0
foraddr, end_addr, lineinparse_location_table(lineno, co_linetable):
ifaddr<=addrqandend_addr>addrq:
returnline
assertFalse, "Unreachable"


defitems_from_keys_and_values(keys, values):
entries, nentries=PyDictObjectPtr._get_entries(keys)
foriinsafe_range(nentries):
ep=entries[i]
pyop_value=PyObjectPtr.from_pyobject_ptr(values[i])
ifnotpyop_value.is_null():
pyop_key=PyObjectPtr.from_pyobject_ptr(ep['me_key'])
yield (pyop_key, pyop_value)

classPyKeysValuesPair:

def__init__(self, keys, values):
self.keys=keys
self.values=values

defiteritems(self):
returnitems_from_keys_and_values(self.keys, self.values)

defproxyval(self, visited):
result= {}
forpyop_key, pyop_valueinself.iteritems():
proxy_key=pyop_key.proxyval(visited)
proxy_value=pyop_value.proxyval(visited)
result[proxy_key] =proxy_value
returnresult

classPyDictObjectPtr(PyObjectPtr):
"""
 Class wrapping a gdb.Value that's a PyDictObject* i.e. a dict instance
 within the process being debugged.
 """
_typename='PyDictObject'

defiteritems(self):
'''
 Yields a sequence of (PyObjectPtr key, PyObjectPtr value) pairs,
 analogous to dict.iteritems()
 '''
keys=self.field('ma_keys')
values=self.field('ma_values')
has_values=int(values)
ifhas_values:
values=values['values']
ifhas_values:
foriteminitems_from_keys_and_values(keys, values):
yielditem
return
entries, nentries=self._get_entries(keys)
foriinsafe_range(nentries):
ep=entries[i]
pyop_value=PyObjectPtr.from_pyobject_ptr(ep['me_value'])
ifnotpyop_value.is_null():
pyop_key=PyObjectPtr.from_pyobject_ptr(ep['me_key'])
yield (pyop_key, pyop_value)

defproxyval(self, visited):
# Guard against infinite loops:
ifself.as_address() invisited:
returnProxyAlreadyVisited('{...}')
visited.add(self.as_address())

result= {}
forpyop_key, pyop_valueinself.iteritems():
proxy_key=pyop_key.proxyval(visited)
proxy_value=pyop_value.proxyval(visited)
result[proxy_key] =proxy_value
returnresult

defwrite_repr(self, out, visited):
# Guard against infinite loops:
ifself.as_address() invisited:
out.write('{...}')
return
visited.add(self.as_address())

out.write('{')
first=True
forpyop_key, pyop_valueinself.iteritems():
ifnotfirst:
out.write(', ')
first=False
pyop_key.write_repr(out, visited)
out.write(': ')
pyop_value.write_repr(out, visited)
out.write('}')

@staticmethod
def_get_entries(keys):
dk_nentries=int(keys['dk_nentries'])
dk_size=1<<int(keys['dk_log2_size'])

ifdk_size<=0xFF:
offset=dk_size
elifdk_size<=0xFFFF:
offset=2*dk_size
elifdk_size<=0xFFFFFFFF:
offset=4*dk_size
else:
offset=8*dk_size

ent_addr=keys['dk_indices'].address
ent_addr=ent_addr.cast(_type_unsigned_char_ptr()) +offset
ifint(keys['dk_kind']) ==0: # DICT_KEYS_GENERAL
ent_ptr_t=gdb.lookup_type('PyDictKeyEntry').pointer()
else:
ent_ptr_t=gdb.lookup_type('PyDictUnicodeEntry').pointer()
ent_addr=ent_addr.cast(ent_ptr_t)

returnent_addr, dk_nentries


classPyListObjectPtr(PyObjectPtr):
_typename='PyListObject'

def__getitem__(self, i):
# Get the gdb.Value for the (PyObject*) with the given index:
field_ob_item=self.field('ob_item')
returnfield_ob_item[i]

defproxyval(self, visited):
# Guard against infinite loops:
ifself.as_address() invisited:
returnProxyAlreadyVisited('[...]')
visited.add(self.as_address())

result= [PyObjectPtr.from_pyobject_ptr(self[i]).proxyval(visited)
foriinsafe_range(int_from_int(self.field('ob_size')))]
returnresult

defwrite_repr(self, out, visited):
# Guard against infinite loops:
ifself.as_address() invisited:
out.write('[...]')
return
visited.add(self.as_address())

out.write('[')
foriinsafe_range(int_from_int(self.field('ob_size'))):
ifi>0:
out.write(', ')
element=PyObjectPtr.from_pyobject_ptr(self[i])
element.write_repr(out, visited)
out.write(']')

classPyLongObjectPtr(PyObjectPtr):
_typename='PyLongObject'

defproxyval(self, visited):
'''
 Python's Include/longinterpr.h has this declaration:

 typedef struct _PyLongValue {
 uintptr_t lv_tag; /* Number of digits, sign and flags */
 digit ob_digit[1];
 } _PyLongValue;

 struct _longobject {
 PyObject_HEAD
 _PyLongValue long_value;
 };

 with this description:
 The absolute value of a number is equal to
 SUM(for i=0 through ndigits-1) ob_digit[i] * 2**(PyLong_SHIFT*i)
 The sign of the value is stored in the lower 2 bits of lv_tag.
 - 0: Positive
 - 1: Zero
 - 2: Negative
 The third lowest bit of lv_tag is reserved for an immortality flag, but is
 not currently used.

 where SHIFT can be either:
 #define PyLong_SHIFT 30
 #define PyLong_SHIFT 15
 '''
long_value=self.field('long_value')
lv_tag=int(long_value['lv_tag'])
size=lv_tag>>3
ifsize==0:
return0

ob_digit=long_value['ob_digit']

ifgdb.lookup_type('digit').sizeof==2:
SHIFT=15
else:
SHIFT=30

digits= [int(ob_digit[i]) *2**(SHIFT*i)
foriinsafe_range(size)]
result=sum(digits)
if (lv_tag&3) ==2:
result=-result
returnresult

defwrite_repr(self, out, visited):
# Write this out as a Python int literal
proxy=self.proxyval(visited)
out.write("%s"%proxy)


classPyBoolObjectPtr(PyLongObjectPtr):
"""
 Class wrapping a gdb.Value that's a PyBoolObject* i.e. one of the two
 <bool> instances (Py_True/Py_False) within the process being debugged.
 """
defproxyval(self, visited):
ifPyLongObjectPtr.proxyval(self, visited):
returnTrue
else:
returnFalse

classPyNoneStructPtr(PyObjectPtr):
"""
 Class wrapping a gdb.Value that's a PyObject* pointing to the
 singleton (we hope) _Py_NoneStruct with ob_type PyNone_Type
 """
_typename='PyObject'

defproxyval(self, visited):
returnNone

classPyFrameObjectPtr(PyObjectPtr):
_typename='PyFrameObject'

def__init__(self, gdbval, cast_to=None):
PyObjectPtr.__init__(self, gdbval, cast_to)

ifnotself.is_optimized_out():
self._frame=PyFramePtr(self.field('f_frame'))

defiter_locals(self):
'''
 Yield a sequence of (name,value) pairs of PyObjectPtr instances, for
 the local variables of this frame
 '''
ifself.is_optimized_out():
return
returnself._frame.iter_locals()

defiter_globals(self):
'''
 Yield a sequence of (name,value) pairs of PyObjectPtr instances, for
 the global variables of this frame
 '''
ifself.is_optimized_out():
return ()
returnself._frame.iter_globals()

defiter_builtins(self):
'''
 Yield a sequence of (name,value) pairs of PyObjectPtr instances, for
 the builtin variables
 '''
ifself.is_optimized_out():
return ()
returnself._frame.iter_builtins()

defget_var_by_name(self, name):

ifself.is_optimized_out():
returnNone, None
returnself._frame.get_var_by_name(name)

deffilename(self):
'''Get the path of the current Python source file, as a string'''
ifself.is_optimized_out():
returnFRAME_INFO_OPTIMIZED_OUT
returnself._frame.filename()

defcurrent_line_num(self):
'''Get current line number as an integer (1-based)

 Translated from PyFrame_GetLineNumber and PyCode_Addr2Line

 See Objects/lnotab_notes.txt
 '''
ifself.is_optimized_out():
returnNone
returnself._frame.current_line_num()