cprover
pointer_logic.cpp
Go to the documentation of this file.
1 /*******************************************************************\
2 
3 Module: Pointer Logic
4 
5 Author: Daniel Kroening, kroening@kroening.com
6 
7 \*******************************************************************/
8 
11 
12 #include "pointer_logic.h"
13 
14 #include <util/arith_tools.h>
15 #include <util/byte_operators.h>
16 #include <util/c_types.h>
17 #include <util/invariant.h>
20 #include <util/prefix.h>
21 #include <util/simplify_expr.h>
22 #include <util/std_expr.h>
23 
25 {
26  return expr.type().get_bool(ID_C_dynamic) ||
27  (expr.id() == ID_symbol &&
28  has_prefix(
29  id2string(to_symbol_expr(expr).get_identifier()),
31 }
32 
33 void pointer_logict::get_dynamic_objects(std::vector<std::size_t> &o) const
34 {
35  o.clear();
36  std::size_t nr=0;
37 
38  for(auto it = objects.cbegin(); it != objects.cend(); ++it, ++nr)
39  if(is_dynamic_object(*it))
40  o.push_back(nr);
41 }
42 
43 std::size_t pointer_logict::add_object(const exprt &expr)
44 {
45  // remove any index/member
46 
47  if(expr.id()==ID_index)
48  {
49  return add_object(to_index_expr(expr).array());
50  }
51  else if(expr.id()==ID_member)
52  {
53  return add_object(to_member_expr(expr).compound());
54  }
55 
56  return objects.number(expr);
57 }
58 
60  std::size_t object,
61  const pointer_typet &type) const
62 {
63  pointert pointer(object, 0);
64  return pointer_expr(pointer, type);
65 }
66 
68  const pointert &pointer,
69  const pointer_typet &type) const
70 {
71  if(pointer.object==null_object) // NULL?
72  {
73  if(pointer.offset==0)
74  {
75  return null_pointer_exprt(type);
76  }
77  else
78  {
79  null_pointer_exprt null(type);
80  return plus_exprt(null,
82  }
83  }
84  else if(pointer.object==invalid_object) // INVALID?
85  {
86  return constant_exprt("INVALID", type);
87  }
88 
89  if(pointer.object>=objects.size())
90  {
91  return constant_exprt("INVALID-" + std::to_string(pointer.object), type);
92  }
93 
94  const exprt &object_expr=objects[pointer.object];
95 
96  typet subtype = type.subtype();
97  // This is a gcc extension.
98  // https://gcc.gnu.org/onlinedocs/gcc-4.8.0/gcc/Pointer-Arith.html
99  if(subtype.id() == ID_empty)
100  subtype = char_type();
101  if(object_expr.id() == ID_string_constant)
102  {
103  subtype = object_expr.type();
104 
105  // a string constant must be array-typed with fixed size
106  const array_typet &array_type = to_array_type(object_expr.type());
107  mp_integer array_size =
108  numeric_cast_v<mp_integer>(to_constant_expr(array_type.size()));
109  if(array_size > pointer.offset)
110  {
111  to_array_type(subtype).size() =
112  from_integer(array_size - pointer.offset, array_type.size().type());
113  }
114  }
115  auto deep_object_opt =
116  get_subexpression_at_offset(object_expr, pointer.offset, subtype, ns);
117  CHECK_RETURN(deep_object_opt.has_value());
118  exprt deep_object = deep_object_opt.value();
119  simplify(deep_object, ns);
120  if(deep_object.id() != byte_extract_id())
122  address_of_exprt(deep_object), type);
123 
124  const byte_extract_exprt &be = to_byte_extract_expr(deep_object);
125  const address_of_exprt base(be.op());
126  if(be.offset().is_zero())
127  return typecast_exprt::conditional_cast(base, type);
128 
129  const auto object_size = pointer_offset_size(be.op().type(), ns);
130  if(object_size.has_value() && *object_size <= 1)
131  {
133  plus_exprt(base, from_integer(pointer.offset, pointer_diff_type())),
134  type);
135  }
136  else if(object_size.has_value() && pointer.offset % *object_size == 0)
137  {
139  plus_exprt(
140  base, from_integer(pointer.offset / *object_size, pointer_diff_type())),
141  type);
142  }
143  else
144  {
146  plus_exprt(
149  type);
150  }
151 }
152 
154 {
155  // add NULL
156  null_object=objects.number(exprt(ID_NULL));
158 
159  // add INVALID
160  invalid_object=objects.number(exprt("INVALID"));
161 }
162 
164 {
165 }
pointer_offset_size.h
Pointer Logic.
typecast_exprt::conditional_cast
static exprt conditional_cast(const exprt &expr, const typet &type)
Definition: std_expr.h:2021
pointer_logict::get_dynamic_objects
void get_dynamic_objects(std::vector< std::size_t > &objects) const
Definition: pointer_logic.cpp:33
typet::subtype
const typet & subtype() const
Definition: type.h:47
arith_tools.h
CHECK_RETURN
#define CHECK_RETURN(CONDITION)
Definition: invariant.h:496
typet
The type of an expression, extends irept.
Definition: type.h:29
to_byte_extract_expr
const byte_extract_exprt & to_byte_extract_expr(const exprt &expr)
Definition: byte_operators.h:57
to_index_expr
const index_exprt & to_index_expr(const exprt &expr)
Cast an exprt to an index_exprt.
Definition: std_expr.h:1347
mp_integer
BigInt mp_integer
Definition: mp_arith.h:19
pointer_predicates.h
Various predicates over pointers in programs.
pointer_logict::add_object
std::size_t add_object(const exprt &expr)
Definition: pointer_logic.cpp:43
prefix.h
invariant.h
plus_exprt
The plus expression Associativity is not specified.
Definition: std_expr.h:881
exprt
Base class for all expressions.
Definition: expr.h:53
pointer_logict::pointer_logict
pointer_logict(const namespacet &_ns)
Definition: pointer_logic.cpp:153
pointer_logict::ns
const namespacet & ns
Definition: pointer_logic.h:74
to_string
std::string to_string(const string_not_contains_constraintt &expr)
Used for debug printing.
Definition: string_constraint.cpp:55
pointer_logict::~pointer_logict
~pointer_logict()
Definition: pointer_logic.cpp:163
pointer_logict::pointert::object
std::size_t object
Definition: pointer_logic.h:30
array_typet::size
const exprt & size() const
Definition: std_types.h:973
namespacet
A namespacet is essentially one or two symbol tables bound together, to allow for symbol lookups in t...
Definition: namespace.h:92
byte_extract_id
irep_idt byte_extract_id()
Definition: byte_operators.cpp:13
exprt::type
typet & type()
Return the type of the expression.
Definition: expr.h:81
pointer_logict::objects
hash_numbering< exprt, irep_hash > objects
Definition: pointer_logic.h:26
irept::get_bool
bool get_bool(const irep_namet &name) const
Definition: irep.cpp:64
pointer_logic.h
Pointer Logic.
byte_operators.h
Expression classes for byte-level operators.
null_pointer_exprt
The null pointer constant.
Definition: std_expr.h:3989
id2string
const std::string & id2string(const irep_idt &d)
Definition: irep.h:44
byte_extract_exprt::op
exprt & op()
Definition: byte_operators.h:43
pointer_logict::null_object
std::size_t null_object
Definition: pointer_logic.h:75
SYMEX_DYNAMIC_PREFIX
#define SYMEX_DYNAMIC_PREFIX
Definition: pointer_predicates.h:17
pointer_logict::pointert::offset
mp_integer offset
Definition: pointer_logic.h:31
simplify
bool simplify(exprt &expr, const namespacet &ns)
Definition: simplify_expr.cpp:2693
pointer_type
pointer_typet pointer_type(const typet &subtype)
Definition: c_types.cpp:243
to_symbol_expr
const symbol_exprt & to_symbol_expr(const exprt &expr)
Cast an exprt to a symbol_exprt.
Definition: std_expr.h:177
object_size
exprt object_size(const exprt &pointer)
Definition: pointer_predicates.cpp:32
irept::id
const irep_idt & id() const
Definition: irep.h:418
char_type
bitvector_typet char_type()
Definition: c_types.cpp:114
simplify_expr.h
byte_extract_exprt::offset
exprt & offset()
Definition: byte_operators.h:44
exprt::is_zero
bool is_zero() const
Return whether the expression is a constant representing 0.
Definition: expr.cpp:132
pointer_offset_size
optionalt< mp_integer > pointer_offset_size(const typet &type, const namespacet &ns)
Compute the size of a type in bytes, rounding up to full bytes.
Definition: pointer_offset_size.cpp:89
array_typet
Arrays with given size.
Definition: std_types.h:965
pointer_logict::is_dynamic_object
bool is_dynamic_object(const exprt &expr) const
Definition: pointer_logic.cpp:24
from_integer
constant_exprt from_integer(const mp_integer &int_value, const typet &type)
Definition: arith_tools.cpp:99
get_subexpression_at_offset
optionalt< exprt > get_subexpression_at_offset(const exprt &expr, const mp_integer &offset_bytes, const typet &target_type_raw, const namespacet &ns)
Definition: pointer_offset_size.cpp:612
pointer_logict::invalid_object
std::size_t invalid_object
Definition: pointer_logic.h:75
byte_extract_exprt
Expression of type type extracted from some object op starting at position offset (given in number of...
Definition: byte_operators.h:29
to_array_type
const array_typet & to_array_type(const typet &type)
Cast a typet to an array_typet.
Definition: std_types.h:1011
to_member_expr
const member_exprt & to_member_expr(const exprt &expr)
Cast an exprt to a member_exprt.
Definition: std_expr.h:3489
has_prefix
bool has_prefix(const std::string &s, const std::string &prefix)
Definition: converter.cpp:13
address_of_exprt
Operator to return the address of an object.
Definition: std_expr.h:2786
typecast_exprt
Semantic type conversion.
Definition: std_expr.h:2013
pointer_diff_type
signedbv_typet pointer_diff_type()
Definition: c_types.cpp:228
pointer_typet
The pointer type These are both 'bitvector_typet' (they have a width) and 'type_with_subtypet' (they ...
Definition: std_types.h:1488
constant_exprt
A constant literal expression.
Definition: std_expr.h:3906
std_expr.h
API to expression classes.
c_types.h
pointer_logict::pointert
Definition: pointer_logic.h:29
pointer_logict::pointer_expr
exprt pointer_expr(const pointert &pointer, const pointer_typet &type) const
Convert an (object,offset) pair to an expression.
Definition: pointer_logic.cpp:67
to_constant_expr
const constant_exprt & to_constant_expr(const exprt &expr)
Cast an exprt to a constant_exprt.
Definition: std_expr.h:3939