static bool is_skip(goto_programt::instructionst::iterator it)
{
if (it->is_skip())
return true;
if (it->is_goto())
{
if (is_constant_bool2t(it->guard) &&
!to_constant_bool2t(it->guard).constant_value)
return true;
if (it->targets.size()!=1)
return false;
goto_programt::instructionst::iterator next_it=it;
next_it++;
return it->targets.front()==next_it;
}
if(it->is_other())
{
return is_nil_expr(it->code);
}
return false;
}
void goto_inlinet::replace_return(
goto_programt &dest,
const exprt &lhs,
const exprt &constrain)
{
for(goto_programt::instructionst::iterator
it=dest.instructions.begin();
it!=dest.instructions.end();
it++)
{
if(it->is_return())
{
if(lhs.is_not_nil())
{
goto_programt tmp;
goto_programt::targett assignment=tmp.add_instruction(ASSIGN);
const code_return2t &ret = to_code_return2t(it->code);
code_assignt code_assign(lhs, migrate_expr_back(ret.operand));
// this may happen if the declared return type at the call site
// differs from the defined return type
if(code_assign.lhs().type()!=
code_assign.rhs().type())
code_assign.rhs().make_typecast(code_assign.lhs().type());
migrate_expr(code_assign, assignment->code);
assignment->location=it->location;
assignment->local_variables=it->local_variables;
assignment->function=it->location.get_function();
assert(constrain.is_nil()); // bp_constrain gumpf reomved
dest.insert_swap(it, *assignment);
it++;
}
else if(!is_nil_expr(it->code))
{
// Encode evaluation of return expr, so that returns with pointer
// derefs in them still get dereferenced, even when the result is
// discarded.
goto_programt tmp;
goto_programt::targett expression=tmp.add_instruction(OTHER);
expression->make_other();
expression->location=it->location;
expression->function=it->location.get_function();
expression->local_variables=it->local_variables;
const code_return2t &ret = to_code_return2t(it->code);
expression->code = code_expression2tc(ret.operand);
dest.insert_swap(it, *expression);
it++;
}
it->make_goto(--dest.instructions.end());
}
}
}
void goto_symext::track_new_pointer(
const expr2tc &ptr_obj,
const type2tc &new_type,
const expr2tc &size)
{
// Also update all the accounting data.
// Mark that object as being dynamic, in the __ESBMC_is_dynamic array
type2tc sym_type =
type2tc(new array_type2t(get_bool_type(), expr2tc(), true));
symbol2tc sym(sym_type, dyn_info_arr_name);
index2tc idx(get_bool_type(), sym, ptr_obj);
expr2tc truth = gen_true_expr();
symex_assign(code_assign2tc(idx, truth), true);
symbol2tc valid_sym(sym_type, valid_ptr_arr_name);
index2tc valid_index_expr(get_bool_type(), valid_sym, ptr_obj);
truth = gen_true_expr();
symex_assign(code_assign2tc(valid_index_expr, truth), true);
symbol2tc dealloc_sym(sym_type, deallocd_arr_name);
index2tc dealloc_index_expr(get_bool_type(), dealloc_sym, ptr_obj);
expr2tc falseity = gen_false_expr();
symex_assign(code_assign2tc(dealloc_index_expr, falseity), true);
type2tc sz_sym_type =
type2tc(new array_type2t(pointer_type2(), expr2tc(), true));
symbol2tc sz_sym(sz_sym_type, alloc_size_arr_name);
index2tc sz_index_expr(get_bool_type(), sz_sym, ptr_obj);
expr2tc object_size_exp;
if(is_nil_expr(size))
{
try
{
mp_integer object_size = type_byte_size(new_type);
object_size_exp =
constant_int2tc(pointer_type2(), object_size.to_ulong());
}
catch(array_type2t::dyn_sized_array_excp *e)
{
object_size_exp = typecast2tc(pointer_type2(), e->size);
}
}
else
{
object_size_exp = size;
}
symex_assign(code_assign2tc(sz_index_expr, object_size_exp), true);
}
smt_astt array_sym_smt_ast::update(
smt_convt *ctx,
smt_astt value,
unsigned int idx,
expr2tc idx_expr) const
{
const array_type2t array_type = to_array_type(sort->get_tuple_type());
const struct_union_data &data = ctx->get_type_def(array_type.subtype);
expr2tc index;
if(is_nil_expr(idx_expr))
{
index =
constant_int2tc(ctx->make_array_domain_type(array_type), BigInt(idx));
}
else
{
index = idx_expr;
}
std::string name = ctx->mk_fresh_name("tuple_array_update::") + ".";
tuple_sym_smt_astt result = new array_sym_smt_ast(ctx, sort, name);
// Iterate over all members. They are _all_ indexed and updated.
unsigned int i = 0;
for(auto const &it : data.members)
{
type2tc arrtype(
new array_type2t(it, array_type.array_size, array_type.size_is_infinite));
// Project and update a field in 'this'
smt_astt field = project(ctx, i);
smt_astt resval = value->project(ctx, i);
smt_astt updated = field->update(ctx, resval, 0, index);
// Now equality it into the result object
smt_astt res_field = result->project(ctx, i);
updated->assign(ctx, res_field);
i++;
}
return result;
}
bool goto_symex_statet::constant_propagation(const expr2tc &expr) const
{
static unsigned int with_counter=0;
// Don't permit const propagaion of infinite-size arrays. They're going to
// be special modelling arrays that require special handling either at SMT
// or some other level, so attempting to optimse them is a Bad Plan (TM).
if (is_array_type(expr) && to_array_type(expr->type).size_is_infinite)
return false;
if (is_nil_expr(expr)) {
return true; // It's fine to constant propagate something that's absent.
} else if (is_constant_expr(expr)) {
return true;
}
else if (is_symbol2t(expr) && to_symbol2t(expr).thename == "NULL")
{
// Null is also essentially a constant.
return true;
}
else if (is_address_of2t(expr))
{
return constant_propagation_reference(to_address_of2t(expr).ptr_obj);
}
else if (is_typecast2t(expr))
{
return constant_propagation(to_typecast2t(expr).from);
}
else if (is_add2t(expr))
{
forall_operands2(it, idx, expr)
if(!constant_propagation(*it))
return false;
return true;
}
else if (is_constant_array_of2t(expr))
expr2tc
goto_symext::symex_mem(
const bool is_malloc,
const expr2tc &lhs,
const sideeffect2t &code)
{
if (is_nil_expr(lhs))
return expr2tc(); // ignore
// size
type2tc type = code.alloctype;
expr2tc size = code.size;
bool size_is_one = false;
if (is_nil_expr(size))
size_is_one=true;
else
{
cur_state->rename(size);
mp_integer i;
if (is_constant_int2t(size) && to_constant_int2t(size).as_ulong() == 1)
size_is_one = true;
}
if (is_nil_type(type))
type = char_type2();
else if (is_union_type(type)) {
// Filter out creation of instantiated unions. They're now all byte arrays.
size_is_one = false;
type = char_type2();
}
unsigned int &dynamic_counter = get_dynamic_counter();
dynamic_counter++;
// value
symbolt symbol;
symbol.base_name = "dynamic_" + i2string(dynamic_counter) +
(size_is_one ? "_value" : "_array");
symbol.name = "symex_dynamic::" + id2string(symbol.base_name);
symbol.lvalue = true;
typet renamedtype = ns.follow(migrate_type_back(type));
if(size_is_one)
symbol.type=renamedtype;
else
{
symbol.type=typet(typet::t_array);
symbol.type.subtype()=renamedtype;
symbol.type.size(migrate_expr_back(size));
}
symbol.type.dynamic(true);
symbol.mode="C";
new_context.add(symbol);
type2tc new_type;
migrate_type(symbol.type, new_type);
address_of2tc rhs_addrof(get_empty_type(), expr2tc());
if(size_is_one)
{
rhs_addrof.get()->type = get_pointer_type(pointer_typet(symbol.type));
rhs_addrof.get()->ptr_obj = symbol2tc(new_type, symbol.name);
}
else
{
type2tc subtype;
migrate_type(symbol.type.subtype(), subtype);
expr2tc sym = symbol2tc(new_type, symbol.name);
expr2tc idx_val = zero_ulong;
expr2tc idx = index2tc(subtype, sym, idx_val);
rhs_addrof.get()->type =
get_pointer_type(pointer_typet(symbol.type.subtype()));
rhs_addrof.get()->ptr_obj = idx;
}
expr2tc rhs = rhs_addrof;
expr2tc ptr_rhs = rhs;
if (!options.get_bool_option("force-malloc-success")) {
symbol2tc null_sym(rhs->type, "NULL");
sideeffect2tc choice(get_bool_type(), expr2tc(), expr2tc(), std::vector<expr2tc>(), type2tc(), sideeffect2t::nondet);
rhs = if2tc(rhs->type, choice, rhs, null_sym);
replace_nondet(rhs);
ptr_rhs = rhs;
}
if (rhs->type != lhs->type)
rhs = typecast2tc(lhs->type, rhs);
cur_state->rename(rhs);
expr2tc rhs_copy(rhs);
guardt guard;
symex_assign_rec(lhs, rhs, guard);
pointer_object2tc ptr_obj(pointer_type2(), ptr_rhs);
track_new_pointer(ptr_obj, new_type);
dynamic_memory.push_back(allocated_obj(rhs_copy, cur_state->guard, !is_malloc));
return rhs_addrof->ptr_obj;
}
void goto_symext::symex_realloc(const expr2tc &lhs, const sideeffect2t &code)
{
expr2tc src_ptr = code.operand;
expr2tc realloc_size = code.size;
internal_deref_items.clear();
dereference2tc deref(get_empty_type(), src_ptr);
dereference(deref, dereferencet::INTERNAL);
// src_ptr is now invalidated.
// Free the given pointer. This just uses the pointer object from the pointer
// variable that's the argument to realloc. It also leads to pointer validity
// checking, and checks that the offset is zero.
code_free2tc fr(code.operand);
symex_free(fr);
// We now have a list of things to work on. Recurse into them, build a result,
// and then switch between those results afterwards.
// Result list is the address of the reallocated piece of data, and the guard.
std::list<std::pair<expr2tc, expr2tc>> result_list;
for(auto &item : internal_deref_items)
{
expr2tc guard = item.guard;
cur_state->rename_address(item.object);
cur_state->guard.guard_expr(guard);
target->renumber(guard, item.object, realloc_size, cur_state->source);
type2tc new_ptr = type2tc(new pointer_type2t(item.object->type));
address_of2tc addrof(new_ptr, item.object);
result_list.emplace_back(addrof, item.guard);
// Bump the realloc-numbering of the object. This ensures that, after
// renaming, the address_of we just generated compares differently to
// previous address_of's before the realloc.
unsigned int cur_num = 0;
if(cur_state->realloc_map.find(item.object) != cur_state->realloc_map.end())
{
cur_num = cur_state->realloc_map[item.object];
}
cur_num++;
std::map<expr2tc, unsigned>::value_type v(item.object, cur_num);
cur_state->realloc_map.insert(v);
}
// Rebuild a gigantic if-then-else chain from the result list.
expr2tc result;
if(result_list.size() == 0)
{
// Nothing happened; there was nothing, or only null, to point at.
// In this case, just return right now and leave the pointer free. The
// symex_free that occurred above should trigger a dereference failure.
return;
}
result = expr2tc();
for(auto const &it : result_list)
{
if(is_nil_expr(result))
result = it.first;
else
result = if2tc(result->type, it.second, it.first, result);
}
// Install pointer modelling data into the relevant arrays.
pointer_object2tc ptr_obj(pointer_type2(), result);
track_new_pointer(ptr_obj, type2tc(), realloc_size);
symex_assign(code_assign2tc(lhs, result), true);
}
void
goto_symext::symex_step(reachability_treet & art)
{
assert(!cur_state->call_stack.empty());
const goto_programt::instructiont &instruction = *cur_state->source.pc;
// depth exceeded?
{
if (depth_limit != 0 && cur_state->depth > depth_limit)
cur_state->guard.add(false_expr);
cur_state->depth++;
}
// actually do instruction
switch (instruction.type) {
case SKIP:
case LOCATION:
// really ignore
cur_state->source.pc++;
break;
case END_FUNCTION:
symex_end_of_function();
// Potentially skip to run another function ptr target; if not,
// continue
if (!run_next_function_ptr_target(false))
cur_state->source.pc++;
break;
case GOTO:
{
expr2tc tmp(instruction.guard);
replace_nondet(tmp);
dereference(tmp, false);
replace_dynamic_allocation(tmp);
symex_goto(tmp);
}
break;
case ASSUME:
if (!cur_state->guard.is_false()) {
expr2tc tmp = instruction.guard;
replace_nondet(tmp);
dereference(tmp, false);
replace_dynamic_allocation(tmp);
cur_state->rename(tmp);
do_simplify(tmp);
if (!is_true(tmp)) {
expr2tc tmp2 = tmp;
expr2tc tmp3 = tmp2;
cur_state->guard.guard_expr(tmp2);
assume(tmp2);
// we also add it to the state guard
cur_state->guard.add(tmp3);
}
}
cur_state->source.pc++;
break;
case ASSERT:
if (!cur_state->guard.is_false()) {
if (!no_assertions ||
!cur_state->source.pc->location.user_provided()
|| deadlock_check) {
std::string msg = cur_state->source.pc->location.comment().as_string();
if (msg == "") msg = "assertion";
expr2tc tmp = instruction.guard;
replace_nondet(tmp);
dereference(tmp, false);
replace_dynamic_allocation(tmp);
claim(tmp, msg);
}
}
cur_state->source.pc++;
break;
case RETURN:
if (!cur_state->guard.is_false()) {
expr2tc thecode = instruction.code, assign;
if (make_return_assignment(assign, thecode)) {
goto_symext::symex_assign(assign);
}
symex_return();
}
cur_state->source.pc++;
break;
case ASSIGN:
if (!cur_state->guard.is_false()) {
code_assign2tc deref_code = instruction.code;
// XXX jmorse -- this is not fully symbolic.
if (thrown_obj_map.find(cur_state->source.pc) != thrown_obj_map.end()) {
symbol2tc thrown_obj = thrown_obj_map[cur_state->source.pc];
if (is_pointer_type(deref_code.get()->target.get()->type)
&& !is_pointer_type(thrown_obj.get()->type))
{
expr2tc new_thrown_obj(new address_of2t(thrown_obj.get()->type, thrown_obj));
deref_code.get()->source = new_thrown_obj;
}
else
deref_code.get()->source = thrown_obj;
thrown_obj_map.erase(cur_state->source.pc);
}
replace_nondet(deref_code);
code_assign2t &assign = to_code_assign2t(deref_code);
dereference(assign.target, true);
dereference(assign.source, false);
replace_dynamic_allocation(deref_code);
symex_assign(deref_code);
}
cur_state->source.pc++;
break;
case FUNCTION_CALL:
{
expr2tc deref_code = instruction.code;
replace_nondet(deref_code);
code_function_call2t &call = to_code_function_call2t(deref_code);
if (!is_nil_expr(call.ret)) {
dereference(call.ret, true);
}
replace_dynamic_allocation(deref_code);
for (std::vector<expr2tc>::iterator it = call.operands.begin();
it != call.operands.end(); it++)
if (!is_nil_expr(*it))
dereference(*it, false);
// Always run intrinsics, whether guard is false or not. This is due to the
// unfortunate circumstance where a thread starts with false guard due to
// decision taken in another thread in this trace. In that case the
// terminate intrinsic _has_ to run, or we explode.
if (is_symbol2t(call.function)) {
const irep_idt &id = to_symbol2t(call.function).thename;
if (has_prefix(id.as_string(), "c::__ESBMC")) {
cur_state->source.pc++;
std::string name = id.as_string().substr(3);
run_intrinsic(call, art, name);
return;
} else if (has_prefix(id.as_string(), "cpp::__ESBMC")) {
cur_state->source.pc++;
std::string name = id.as_string().substr(5);
name = name.substr(0, name.find("("));
run_intrinsic(call, art, name);
return;
}
}
// Don't run a function call if the guard is false.
if (!cur_state->guard.is_false()) {
symex_function_call(deref_code);
} else {
cur_state->source.pc++;
}
}
break;
case OTHER:
if (!cur_state->guard.is_false()) {
symex_other();
}
cur_state->source.pc++;
break;
case CATCH:
symex_catch();
break;
case THROW:
if (!cur_state->guard.is_false()) {
if(symex_throw())
cur_state->source.pc++;
} else {
cur_state->source.pc++;
}
break;
case THROW_DECL:
symex_throw_decl();
cur_state->source.pc++;
break;
case THROW_DECL_END:
// When we reach THROW_DECL_END, we must clear any throw_decl
if(stack_catch.size())
{
// Get to the correct try (always the last one)
goto_symex_statet::exceptiont* except=&stack_catch.top();
except->has_throw_decl=false;
except->throw_list_set.clear();
}
cur_state->source.pc++;
break;
default:
std::cerr << "GOTO instruction type " << instruction.type;
std::cerr << " not handled in goto_symext::symex_step" << std::endl;
abort();
}
}
