void goto_symext::dereference_rec(
exprt &expr,
statet &state,
guardt &guard,
const bool write)
{
if(expr.id()==ID_dereference)
{
if(expr.operands().size()!=1)
throw "dereference takes one operand";
exprt tmp1;
tmp1.swap(expr.op0());
// first make sure there are no dereferences in there
dereference_rec(tmp1, state, guard, false);
// we need to set up some elaborate call-backs
symex_dereference_statet symex_dereference_state(*this, state);
value_set_dereferencet dereference(
ns,
new_symbol_table,
options,
symex_dereference_state,
language_mode);
// std::cout << "**** " << from_expr(ns, "", tmp1) << std::endl;
exprt tmp2=dereference.dereference(
tmp1, guard, write?value_set_dereferencet::WRITE:value_set_dereferencet::READ);
//std::cout << "**** " << from_expr(ns, "", tmp2) << std::endl;
expr.swap(tmp2);
// this may yield a new auto-object
trigger_auto_object(expr, state);
}
else if(expr.id()==ID_index &&
to_index_expr(expr).array().id()==ID_member &&
to_array_type(ns.follow(to_index_expr(expr).array().type())).
size().is_zero())
{
// This is an expression of the form x.a[i],
// where a is a zero-sized array. This gets
// re-written into *(&x.a+i)
index_exprt index_expr=to_index_expr(expr);
address_of_exprt address_of_expr(index_expr.array());
address_of_expr.type()=pointer_typet(expr.type());
dereference_exprt tmp;
tmp.pointer()=plus_exprt(address_of_expr, index_expr.index());
tmp.type()=expr.type();
tmp.add_source_location()=expr.source_location();
// recursive call
dereference_rec(tmp, state, guard, write);
expr.swap(tmp);
}
else if(expr.id()==ID_index &&
to_index_expr(expr).array().type().id()==ID_pointer)
{
// old stuff, will go away
assert(false);
}
else if(expr.id()==ID_address_of)
{
address_of_exprt &address_of_expr=to_address_of_expr(expr);
exprt &object=address_of_expr.object();
const typet &expr_type=ns.follow(expr.type());
expr=address_arithmetic(object, state, guard,
expr_type.subtype().id()==ID_array);
}
else if(expr.id()==ID_typecast)
{
exprt &tc_op=to_typecast_expr(expr).op();
// turn &array into &array[0] when casting to pointer-to-element-type
if(tc_op.id()==ID_address_of &&
to_address_of_expr(tc_op).object().type().id()==ID_array &&
base_type_eq(
expr.type(),
pointer_typet(to_address_of_expr(tc_op).object().type().subtype()),
ns))
{
expr=
address_of_exprt(
index_exprt(
to_address_of_expr(tc_op).object(),
from_integer(0, index_type())));
dereference_rec(expr, state, guard, write);
}
else
{
dereference_rec(tc_op, state, guard, write);
}
}
else
{
Forall_operands(it, expr)
dereference_rec(*it, state, guard, write);
}
}
void goto_program_dereferencet::dereference_rec(
exprt &expr,
guardt &guard,
const value_set_dereferencet::modet mode)
{
if(!dereference.has_dereference(expr))
return;
if(expr.id()==ID_and || expr.id()==ID_or)
{
if(!expr.is_boolean())
throw expr.id_string()+" must be Boolean, but got "+
expr.pretty();
guardt old_guard=guard;
for(unsigned i=0; i<expr.operands().size(); i++)
{
exprt &op=expr.operands()[i];
if(!op.is_boolean())
throw expr.id_string()+" takes Boolean operands only, but got "+
op.pretty();
if(dereference.has_dereference(op))
dereference_rec(op, guard, value_set_dereferencet::modet::READ);
if(expr.id()==ID_or)
{
exprt tmp(op);
tmp.make_not();
guard.add(tmp);
}
else
guard.add(op);
}
guard.swap(old_guard);
return;
}
else if(expr.id()==ID_if)
{
if(expr.operands().size()!=3)
throw "if takes three arguments";
if(!expr.op0().is_boolean())
{
std::string msg=
"first argument of if must be boolean, but got "
+expr.op0().pretty();
throw msg;
}
dereference_rec(expr.op0(), guard, value_set_dereferencet::modet::READ);
bool o1=dereference.has_dereference(expr.op1());
bool o2=dereference.has_dereference(expr.op2());
if(o1)
{
guardt old_guard=guard;
guard.add(expr.op0());
dereference_rec(expr.op1(), guard, mode);
guard.swap(old_guard);
}
if(o2)
{
guardt old_guard=guard;
exprt tmp(expr.op0());
tmp.make_not();
guard.add(tmp);
dereference_rec(expr.op2(), guard, mode);
guard.swap(old_guard);
}
return;
}
if(expr.id()==ID_address_of ||
expr.id()=="reference_to")
{
// turn &*p to p
// this has *no* side effect!
assert(expr.operands().size()==1);
if(expr.op0().id()==ID_dereference)
{
assert(expr.op0().operands().size()==1);
exprt tmp;
tmp.swap(expr.op0().op0());
if(tmp.type()!=expr.type())
tmp.make_typecast(expr.type());
expr.swap(tmp);
}
}
Forall_operands(it, expr)
dereference_rec(*it, guard, mode);
if(expr.id()==ID_dereference)
{
if(expr.operands().size()!=1)
throw "dereference expects one operand";
dereference_location=expr.find_source_location();
exprt tmp=dereference.dereference(
expr.op0(), guard, mode);
expr.swap(tmp);
}
else if(expr.id()==ID_index)
{
// this is old stuff and will go away
if(expr.operands().size()!=2)
throw "index expects two operands";
if(expr.op0().type().id()==ID_pointer)
{
dereference_location=expr.find_source_location();
exprt tmp1(ID_plus, expr.op0().type());
tmp1.operands().swap(expr.operands());
exprt tmp2=dereference.dereference(tmp1, guard, mode);
tmp2.swap(expr);
}
}
}
exprt goto_symext::address_arithmetic(
const exprt &expr,
statet &state,
guardt &guard,
bool keep_array)
{
exprt result;
if(expr.id()==ID_byte_extract_little_endian ||
expr.id()==ID_byte_extract_big_endian)
{
// address_of(byte_extract(op, offset, t)) is
// address_of(op) + offset with adjustments for arrays
const byte_extract_exprt &be=to_byte_extract_expr(expr);
// recursive call
result=address_arithmetic(be.op(), state, guard, keep_array);
if(ns.follow(be.op().type()).id()==ID_array &&
result.id()==ID_address_of)
{
address_of_exprt &a=to_address_of_expr(result);
// turn &a of type T[i][j] into &(a[0][0])
for(const typet *t=&(ns.follow(a.type().subtype()));
t->id()==ID_array && !base_type_eq(expr.type(), *t, ns);
t=&(ns.follow(*t).subtype()))
a.object()=index_exprt(a.object(), from_integer(0, index_type()));
}
// do (expr.type() *)(((char *)op)+offset)
result=typecast_exprt(result, pointer_typet(char_type()));
// there could be further dereferencing in the offset
exprt offset=be.offset();
dereference_rec(offset, state, guard, false);
result=plus_exprt(result, offset);
// treat &array as &array[0]
const typet &expr_type=ns.follow(expr.type());
pointer_typet dest_type;
if(expr_type.id()==ID_array && !keep_array)
dest_type.subtype()=expr_type.subtype();
else
dest_type.subtype()=expr_type;
result=typecast_exprt(result, dest_type);
}
else if(expr.id()==ID_index ||
expr.id()==ID_member)
{
object_descriptor_exprt ode;
ode.build(expr, ns);
byte_extract_exprt be(byte_extract_id());
be.type()=expr.type();
be.op()=ode.root_object();
be.offset()=ode.offset();
// recursive call
result=address_arithmetic(be, state, guard, keep_array);
do_simplify(result);
}
else if(expr.id()==ID_dereference)
{
// ANSI-C guarantees &*p == p no matter what p is,
// even if it's complete garbage
// just grab the pointer, but be wary of further dereferencing
// in the pointer itself
result=to_dereference_expr(expr).pointer();
dereference_rec(result, state, guard, false);
}
else if(expr.id()==ID_if)
{
if_exprt if_expr=to_if_expr(expr);
// the condition is not an address
dereference_rec(if_expr.cond(), state, guard, false);
// recursive call
if_expr.true_case()=
address_arithmetic(if_expr.true_case(), state, guard, keep_array);
if_expr.false_case()=
address_arithmetic(if_expr.false_case(), state, guard, keep_array);
result=if_expr;
}
else if(expr.id()==ID_symbol ||
expr.id()==ID_string_constant ||
expr.id()==ID_label ||
expr.id()==ID_array)
{
// give up, just dereference
result=expr;
dereference_rec(result, state, guard, false);
// turn &array into &array[0]
if(ns.follow(result.type()).id()==ID_array && !keep_array)
result=index_exprt(result, from_integer(0, index_type()));
// handle field-sensitive SSA symbol
mp_integer offset=0;
if(expr.id()==ID_symbol &&
expr.get_bool(ID_C_SSA_symbol))
{
offset=compute_pointer_offset(expr, ns);
assert(offset>=0);
}
if(offset>0)
{
byte_extract_exprt be(byte_extract_id());
be.type()=expr.type();
be.op()=to_ssa_expr(expr).get_l1_object();
be.offset()=from_integer(offset, index_type());
result=address_arithmetic(be, state, guard, keep_array);
do_simplify(result);
}
else
result=address_of_exprt(result);
}
else
throw "goto_symext::address_arithmetic does not handle "+expr.id_string();
const typet &expr_type=ns.follow(expr.type());
assert((expr_type.id()==ID_array && !keep_array) ||
base_type_eq(pointer_typet(expr_type), result.type(), ns));
return result;
}
