pointer_predicates.cpp

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/*******************************************************************\
 
Module: Various predicates over pointers in programs
 
Author: Daniel Kroening, kroening@kroening.com
 
\*******************************************************************/
 
 
#include "pointer_predicates.h"
 
#include "arith_tools.h"
#include "c_types.h"
#include "cprover_prefix.h"
#include "namespace.h"
#include "pointer_expr.h"
#include "pointer_offset_size.h"
#include "std_expr.h"
#include "symbol.h"
 
exprt pointer_object(const exprt &p)
{
  return pointer_object_exprt(p, size_type());
}
 
exprt same_object(const exprt &p1, const exprt &p2)
{
  return equal_exprt(pointer_object(p1), pointer_object(p2));
}
 
exprt object_size(const exprt &pointer)
{
  return object_size_exprt(pointer, size_type());
}
 
exprt pointer_offset(const exprt &pointer)
{
  return pointer_offset_exprt(pointer, size_type());
}
 
exprt deallocated(const exprt &pointer, const namespacet &ns)
{
  // we check __CPROVER_deallocated!
  const symbolt &deallocated_symbol=ns.lookup(CPROVER_PREFIX "deallocated");
 
  return same_object(pointer, deallocated_symbol.symbol_expr());
}
 
exprt dead_object(const exprt &pointer, const namespacet &ns)
{
  // we check __CPROVER_dead_object!
  const symbolt &deallocated_symbol=ns.lookup(CPROVER_PREFIX "dead_object");
 
  return same_object(pointer, deallocated_symbol.symbol_expr());
}
 
exprt null_object(const exprt &pointer)
{
  null_pointer_exprt null_pointer(to_pointer_type(pointer.type()));
  return same_object(null_pointer, pointer);
}
 
exprt integer_address(const exprt &pointer)
{
  null_pointer_exprt null_pointer(to_pointer_type(pointer.type()));
  return and_exprt(same_object(null_pointer, pointer),
                   notequal_exprt(null_pointer, pointer));
}
 
exprt object_upper_bound(
  const exprt &pointer,
  const exprt &access_size)
{
  exprt object_offset = pointer_offset(pointer);
 
  exprt object_size_expr=object_size(pointer);
 
  std::size_t max_width = std::max(
    to_bitvector_type(object_offset.type()).get_width(),
    to_bitvector_type(object_size_expr.type()).get_width());
 
  // We add the size to the offset, if given.
  if(access_size.is_not_nil())
  {
    // This is
    // POINTER_OFFSET(p)+access_size>OBJECT_SIZE(pointer)
    // We enlarge all bit-vectors to avoid an overflow on the addition.
 
    max_width =
      std::max(max_width, to_bitvector_type(access_size.type()).get_width());
 
    auto type = unsignedbv_typet(max_width + 1);
 
    auto sum = plus_exprt(
      typecast_exprt::conditional_cast(object_offset, type),
      typecast_exprt::conditional_cast(access_size, type));
 
    return binary_relation_exprt(
      sum, ID_gt, typecast_exprt::conditional_cast(object_size_expr, type));
  }
  else
  {
    // This is
    // POINTER_OFFSET(p)>=OBJECT_SIZE(pointer)
 
    auto type = unsignedbv_typet(max_width);
 
    return binary_relation_exprt(
      typecast_exprt::conditional_cast(object_offset, type),
      ID_ge,
      typecast_exprt::conditional_cast(object_size_expr, type));
  }
}
 
exprt object_lower_bound(
  const exprt &pointer,
  const exprt &offset)
{
  exprt p_offset=pointer_offset(pointer);
 
  exprt zero=from_integer(0, p_offset.type());
 
  if(offset.is_not_nil())
  {
    p_offset = plus_exprt(
      p_offset, typecast_exprt::conditional_cast(offset, p_offset.type()));
  }
 
  return binary_relation_exprt(std::move(p_offset), ID_lt, std::move(zero));
}