void remove_return(goto_programt &body, const goto_programt::targett pos)
{
code_function_callt &call=to_code_function_call(pos->code);
const irep_idt &id=to_symbol_expr(call.function()).get_identifier();
const typet &type=call.lhs().type();
const source_locationt &loc=pos->source_location;
const irep_idt &func=pos->function;
const goto_programt::targett assign=body.insert_after(pos);
assign->make_assignment();
assign->source_location=loc;
assign->code=code_assignt(call.lhs(), get_ret_val_var(id, type));
assign->function=func;
call.lhs().make_nil();
}
void all_paths_enumeratort::extend_path(patht &path,
goto_programt::targett t,
int succ) {
goto_programt::targett next;
goto_programt::targetst succs;
exprt guard = true_exprt();
goto_program.get_successors(t, succs);
for (goto_programt::targetst::iterator it = succs.begin();
it != succs.end();
++it) {
if (succ == 0) {
next = *it;
break;
}
succ--;
}
if (t->is_goto()) {
guard = not_exprt(t->guard);
for (goto_programt::targetst::iterator it = t->targets.begin();
it != t->targets.end();
++it) {
if (next == *it) {
guard = t->guard;
break;
}
}
}
path.push_back(path_nodet(next, guard));
}
void string_instrumentationt::do_strtok(
goto_programt &dest,
goto_programt::targett target,
code_function_callt &call)
{
const code_function_callt::argumentst &arguments=call.arguments();
if(arguments.size()!=2)
{
err_location(target->location);
throw "strtok expected to have two arguments";
}
goto_programt tmp;
goto_programt::targett assertion0=tmp.add_instruction();
assertion0->make_assertion(is_zero_string(arguments[0]));
assertion0->location=target->location;
assertion0->location.set("property", "string");
assertion0->location.set("comment", "zero-termination of 1st string argument of strtok");
goto_programt::targett assertion1=tmp.add_instruction();
assertion1->make_assertion(is_zero_string(arguments[1]));
assertion1->location=target->location;
assertion1->location.set("property", "string");
assertion1->location.set("comment", "zero-termination of 2nd string argument of strtok");
target->make_skip();
dest.insert_before_swap(target, tmp);
}
void string_instrumentationt::do_fscanf(
goto_programt &dest,
goto_programt::targett target,
code_function_callt &call)
{
const code_function_callt::argumentst &arguments=call.arguments();
if(arguments.size()<2)
{
err_location(target->location);
throw "fscanf expected to have two or more arguments";
}
goto_programt tmp;
do_format_string_write(tmp, target, arguments, 1, 2, "fscanf");
if(call.lhs().is_not_nil())
{
goto_programt::targett return_assignment=tmp.add_instruction(ASSIGN);
return_assignment->location=target->location;
exprt rhs=side_effect_expr_nondett(call.lhs().type());
rhs.location()=target->location;
return_assignment->code=code_assignt(call.lhs(), rhs);
}
target->make_skip();
dest.insert_before_swap(target, tmp);
}
void string_instrumentationt::do_strstr(
goto_programt &dest,
goto_programt::targett target,
code_function_callt &call)
{
const code_function_callt::argumentst &arguments=call.arguments();
if(arguments.size()!=2)
{
error().source_location=target->source_location;
error() << "strstr expected to have two arguments" << eom;
throw 0;
}
goto_programt tmp;
goto_programt::targett assertion0=tmp.add_instruction();
assertion0->make_assertion(is_zero_string(arguments[0]));
assertion0->source_location=target->source_location;
assertion0->source_location.set_property_class("string");
assertion0->source_location.set_comment("zero-termination of 1st string argument of strstr");
goto_programt::targett assertion1=tmp.add_instruction();
assertion1->make_assertion(is_zero_string(arguments[1]));
assertion1->source_location=target->source_location;
assertion1->source_location.set_property_class("string");
assertion1->source_location.set_comment("zero-termination of 2nd string argument of strstr");
target->make_skip();
dest.insert_before_swap(target, tmp);
}
goto_programt::targett add_return_assignment(goto_programt &body,
goto_programt::targett pos, const irep_idt &func_id, const exprt &value)
{
const source_locationt &loc=pos->source_location;
pos=body.insert_after(pos);
pos->make_assignment();
pos->source_location=loc;
pos->code=code_assignt(get_ret_val_var(func_id, value.type()), value);
return pos;
}
void acceleratet::make_overflow_loc(
goto_programt::targett loop_header,
goto_programt::targett &loop_end,
goto_programt::targett &overflow_loc)
{
symbolt overflow_sym=utils.fresh_symbol("accelerate::overflow", bool_typet());
const exprt &overflow_var=overflow_sym.symbol_expr();
natural_loops_mutablet::natural_loopt &loop =
natural_loops.loop_map[loop_header];
overflow_instrumentert instrumenter(program, overflow_var, symbol_table);
for(natural_loops_mutablet::natural_loopt::iterator it=loop.begin();
it!=loop.end();
++it)
{
overflow_locs[*it]=goto_programt::targetst();
goto_programt::targetst &added=overflow_locs[*it];
instrumenter.add_overflow_checks(*it, added);
loop.insert(added.begin(), added.end());
}
goto_programt::targett t=program.insert_after(loop_header);
t->make_assignment();
t->code=code_assignt(overflow_var, false_exprt());
t->swap(*loop_header);
loop.insert(t);
overflow_locs[loop_header].push_back(t);
goto_programt::instructiont s(SKIP);
overflow_loc=program.insert_after(loop_end);
*overflow_loc=s;
overflow_loc->swap(*loop_end);
loop.insert(overflow_loc);
goto_programt::instructiont g(GOTO);
g.guard=not_exprt(overflow_var);
g.targets.push_back(overflow_loc);
goto_programt::targett t2=program.insert_after(loop_end);
*t2=g;
t2->swap(*loop_end);
overflow_locs[overflow_loc].push_back(t2);
loop.insert(t2);
goto_programt::targett tmp=overflow_loc;
overflow_loc=loop_end;
loop_end=tmp;
}
void string_instrumentationt::do_snprintf(
goto_programt &dest,
goto_programt::targett target,
code_function_callt &call)
{
const code_function_callt::argumentst &arguments=call.arguments();
if(arguments.size()<3)
{
error().source_location=target->source_location;
error() << "snprintf expected to have three or more arguments"
<< eom;
throw 0;
}
goto_programt tmp;
goto_programt::targett assertion=tmp.add_instruction();
assertion->source_location=target->source_location;
assertion->source_location.set_property_class("string");
assertion->source_location.set_comment("snprintf buffer overflow");
exprt bufsize=buffer_size(arguments[0]);
assertion->make_assertion(
binary_relation_exprt(bufsize, ID_ge, arguments[1]));
do_format_string_read(tmp, target, arguments, 2, 3, "snprintf");
if(call.lhs().is_not_nil())
{
goto_programt::targett return_assignment=tmp.add_instruction(ASSIGN);
return_assignment->source_location=target->source_location;
exprt rhs=side_effect_expr_nondett(call.lhs().type());
rhs.add_source_location()=target->source_location;
return_assignment->code=code_assignt(call.lhs(), rhs);
}
target->make_skip();
dest.insert_before_swap(target, tmp);
}
void string_instrumentationt::do_sprintf(
goto_programt &dest,
goto_programt::targett target,
code_function_callt &call)
{
const code_function_callt::argumentst &arguments=call.arguments();
if(arguments.size()<2)
{
error().source_location=target->source_location;
error() << "sprintf expected to have two or more arguments" << eom;
throw 0;
}
goto_programt tmp;
goto_programt::targett assertion=tmp.add_instruction();
assertion->source_location=target->source_location;
assertion->source_location.set_property_class("string");
assertion->source_location.set_comment("sprintf buffer overflow");
// in the abstract model, we have to report a
// (possibly false) positive here
assertion->make_assertion(false_exprt());
do_format_string_read(tmp, target, arguments, 1, 2, "sprintf");
if(call.lhs().is_not_nil())
{
goto_programt::targett return_assignment=tmp.add_instruction(ASSIGN);
return_assignment->source_location=target->source_location;
exprt rhs=side_effect_expr_nondett(call.lhs().type());
rhs.add_source_location()=target->source_location;
return_assignment->code=code_assignt(call.lhs(), rhs);
}
target->make_skip();
dest.insert_before_swap(target, tmp);
}
void remove_virtual_functionst::remove_virtual_function(
goto_programt &goto_program,
goto_programt::targett target)
{
const code_function_callt &code=
to_code_function_call(target->code);
const auto &vcall_source_loc=target->source_location;
const exprt &function=code.function();
assert(function.id()==ID_virtual_function);
assert(!code.arguments().empty());
functionst functions;
get_functions(function, functions);
if(functions.empty())
{
target->make_skip();
return; // give up
}
// only one option?
if(functions.size()==1)
{
assert(target->is_function_call());
if(functions.begin()->symbol_expr==symbol_exprt())
target->make_skip();
else
to_code_function_call(target->code).function()=
functions.begin()->symbol_expr;
return;
}
// the final target is a skip
goto_programt final_skip;
goto_programt::targett t_final=final_skip.add_instruction();
t_final->source_location=vcall_source_loc;
t_final->make_skip();
// build the calls and gotos
goto_programt new_code_calls;
goto_programt new_code_gotos;
exprt this_expr=code.arguments()[0];
// If necessary, cast to the last candidate function to
// get the object's clsid. By the structure of get_functions,
// this is the parent of all other classes under consideration.
const auto &base_classid=functions.back().class_id;
const auto &base_function_symbol=functions.back().symbol_expr;
symbol_typet suggested_type(base_classid);
exprt c_id2=get_class_identifier_field(this_expr, suggested_type, ns);
std::map<irep_idt, goto_programt::targett> calls;
// Note backwards iteration, to get the least-derived candidate first.
for(auto it=functions.crbegin(), itend=functions.crend(); it!=itend; ++it)
{
const auto &fun=*it;
auto insertit=calls.insert(
{fun.symbol_expr.get_identifier(), goto_programt::targett()});
// Only create one call sequence per possible target:
if(insertit.second)
{
goto_programt::targett t1=new_code_calls.add_instruction();
t1->source_location=vcall_source_loc;
if(!fun.symbol_expr.get_identifier().empty())
{
// call function
t1->make_function_call(code);
auto &newcall=to_code_function_call(t1->code);
newcall.function()=fun.symbol_expr;
pointer_typet need_type(symbol_typet(fun.symbol_expr.get(ID_C_class)));
if(!type_eq(newcall.arguments()[0].type(), need_type, ns))
newcall.arguments()[0].make_typecast(need_type);
}
else
{
// No definition for this type; shouldn't be possible...
t1->make_assertion(false_exprt());
}
insertit.first->second=t1;
// goto final
goto_programt::targett t3=new_code_calls.add_instruction();
t3->source_location=vcall_source_loc;
t3->make_goto(t_final, true_exprt());
}
// If this calls the base function we just fall through.
// Otherwise branch to the right call:
if(fun.symbol_expr!=base_function_symbol)
{
exprt c_id1=constant_exprt(fun.class_id, string_typet());
goto_programt::targett t4=new_code_gotos.add_instruction();
t4->source_location=vcall_source_loc;
t4->make_goto(insertit.first->second, equal_exprt(c_id1, c_id2));
}
}
goto_programt new_code;
// patch them all together
new_code.destructive_append(new_code_gotos);
new_code.destructive_append(new_code_calls);
new_code.destructive_append(final_skip);
// set locations
Forall_goto_program_instructions(it, new_code)
{
const irep_idt property_class=it->source_location.get_property_class();
const irep_idt comment=it->source_location.get_comment();
it->source_location=target->source_location;
it->function=target->function;
if(!property_class.empty())
it->source_location.set_property_class(property_class);
if(!comment.empty())
it->source_location.set_comment(comment);
}
goto_programt::targett next_target=target;
next_target++;
goto_program.destructive_insert(next_target, new_code);
// finally, kill original invocation
target->make_skip();
}
void remove_virtual_functionst::remove_virtual_function(
goto_programt &goto_program,
goto_programt::targett target)
{
const code_function_callt &code=
to_code_function_call(target->code);
const exprt &function=code.function();
assert(function.id()==ID_virtual_function);
assert(!code.arguments().empty());
functionst functions;
get_functions(function, functions);
if(functions.empty())
{
target->make_skip();
return; // give up
}
// the final target is a skip
goto_programt final_skip;
goto_programt::targett t_final=final_skip.add_instruction();
t_final->make_skip();
// build the calls and gotos
goto_programt new_code_calls;
goto_programt new_code_gotos;
for(functionst::const_iterator
it=functions.begin();
it!=functions.end();
it++)
{
// call function
goto_programt::targett t1=new_code_calls.add_instruction();
t1->make_function_call(code);
to_code_function_call(t1->code).function()=it->symbol_expr;
// goto final
goto_programt::targett t3=new_code_calls.add_instruction();
t3->make_goto(t_final, true_exprt());
exprt this_expr=code.arguments()[0];
if(this_expr.type().id()!=ID_pointer ||
this_expr.type().id()!=ID_struct)
{
symbol_typet symbol_type(it->class_id);
this_expr=typecast_exprt(this_expr, pointer_typet(symbol_type));
}
exprt deref=dereference_exprt(this_expr, this_expr.type().subtype());
exprt c_id1=constant_exprt(it->class_id, string_typet());
exprt c_id2=build_class_identifier(deref);
goto_programt::targett t4=new_code_gotos.add_instruction();
t4->make_goto(t1, equal_exprt(c_id1, c_id2));
}
goto_programt new_code;
// patch them all together
new_code.destructive_append(new_code_gotos);
new_code.destructive_append(new_code_calls);
new_code.destructive_append(final_skip);
// set locations
Forall_goto_program_instructions(it, new_code)
{
irep_idt property_class=it->source_location.get_property_class();
irep_idt comment=it->source_location.get_comment();
it->source_location=target->source_location;
it->function=target->function;
if(!property_class.empty()) it->source_location.set_property_class(property_class);
if(!comment.empty()) it->source_location.set_comment(comment);
}
void string_instrumentationt::do_strerror(
goto_programt &dest,
goto_programt::targett it,
code_function_callt &call)
{
if(call.lhs().is_nil())
{
it->make_skip();
return;
}
irep_idt identifier_buf="c::__strerror_buffer";
irep_idt identifier_size="c::__strerror_buffer_size";
if(context.symbols.find(identifier_buf)==context.symbols.end())
{
symbolt new_symbol_size;
new_symbol_size.base_name="__strerror_buffer_size";
new_symbol_size.pretty_name=new_symbol_size.base_name;
new_symbol_size.name=identifier_size;
new_symbol_size.mode="C";
new_symbol_size.type=uint_type();
new_symbol_size.is_statevar=true;
new_symbol_size.lvalue=true;
new_symbol_size.static_lifetime=true;
array_typet type;
type.subtype()=char_type();
type.size()=symbol_expr(new_symbol_size);
symbolt new_symbol_buf;
new_symbol_buf.mode="C";
new_symbol_buf.type=type;
new_symbol_buf.is_statevar=true;
new_symbol_buf.lvalue=true;
new_symbol_buf.static_lifetime=true;
new_symbol_buf.base_name="__strerror_buffer";
new_symbol_buf.pretty_name=new_symbol_buf.base_name;
new_symbol_buf.name="c::"+id2string(new_symbol_buf.base_name);
context.move(new_symbol_buf);
context.move(new_symbol_size);
}
const symbolt &symbol_size=ns.lookup(identifier_size);
const symbolt &symbol_buf=ns.lookup(identifier_buf);
goto_programt tmp;
{
goto_programt::targett assignment1=tmp.add_instruction(ASSIGN);
exprt nondet_size=side_effect_expr_nondett(uint_type());
assignment1->code=code_assignt(symbol_expr(symbol_size), nondet_size);
assignment1->location=it->location;
goto_programt::targett assumption1=tmp.add_instruction();
assumption1->make_assumption(binary_relation_exprt(
symbol_expr(symbol_size), "notequal",
gen_zero(symbol_size.type)));
assumption1->location=it->location;
}
// return a pointer to some magic buffer
exprt index=exprt("index", char_type());
index.copy_to_operands(symbol_expr(symbol_buf), gen_zero(uint_type()));
exprt ptr=exprt("address_of", pointer_typet());
ptr.type().subtype()=char_type();
ptr.copy_to_operands(index);
// make that zero-terminated
{
goto_programt::targett assignment2=tmp.add_instruction(ASSIGN);
assignment2->code=code_assignt(is_zero_string(ptr, true), true_exprt());
assignment2->location=it->location;
}
// assign address
{
goto_programt::targett assignment3=tmp.add_instruction(ASSIGN);
exprt rhs=ptr;
make_type(rhs, call.lhs().type());
assignment3->code=code_assignt(call.lhs(), rhs);
assignment3->location=it->location;
}
it->make_skip();
dest.insert_before_swap(it, tmp);
}
void goto_inlinet::expand_function_call(
goto_programt &dest,
goto_programt::targett &target,
const exprt &lhs,
const exprt &function,
const exprt::operandst &arguments,
const exprt &constrain,
bool full)
{
// look it up
if(function.id()!="symbol")
{
err_location(function);
throw "function_call expects symbol as function operand, "
"but got `"+function.id_string()+"'";
}
const irep_idt &identifier=function.identifier();
// see if we are already expanding it
if(recursion_set.find(identifier)!=recursion_set.end())
{
if(!full)
{
target++;
return; // simply ignore, we don't do full inlining, it's ok
}
// it's really recursive. Uh. Buh. Give up.
err_location(function);
warning("recursion is ignored");
target->make_skip();
target++;
return;
}
goto_functionst::function_mapt::iterator m_it=
goto_functions.function_map.find(identifier);
if(m_it==goto_functions.function_map.end())
{
err_location(function);
str << "failed to find function `" << identifier
<< "'";
throw 0;
}
goto_functiont &f=m_it->second;
// see if we need to inline this
if(!full)
{
if(!f.body_available ||
(!f.is_inlined() && f.body.instructions.size() > smallfunc_limit))
{
target++;
return;
}
}
if(f.body_available)
{
inlined_funcs.insert(identifier.as_string());
for (std::set<std::string>::const_iterator it2 = f.inlined_funcs.begin();
it2 != f.inlined_funcs.end(); it2++) {
inlined_funcs.insert(*it2);
}
recursion_sett::iterator recursion_it=
recursion_set.insert(identifier).first;
goto_programt tmp2;
tmp2.copy_from(f.body);
assert(tmp2.instructions.back().is_end_function());
tmp2.instructions.back().type=LOCATION;
replace_return(tmp2, lhs, constrain);
goto_programt tmp;
parameter_assignments(tmp2.instructions.front().location, f.type, arguments, tmp);
tmp.destructive_append(tmp2);
// set local variables
Forall_goto_program_instructions(it, tmp)
it->local_variables.insert(target->local_variables.begin(),
target->local_variables.end());
if(f.type.hide())
{
const locationt &new_location=function.find_location();
Forall_goto_program_instructions(it, tmp)
{
if(new_location.is_not_nil())
{
// can't just copy, e.g., due to comments field
it->location.id(""); // not NIL
it->location.set_file(new_location.get_file());
it->location.set_line(new_location.get_line());
it->location.set_column(new_location.get_column());
it->location.set_function(new_location.get_function());
}
}
}
// do this recursively
goto_inline_rec(tmp, full);
// set up location instruction for function call
target->type=LOCATION;
target->code = expr2tc();
goto_programt::targett next_target(target);
next_target++;
dest.instructions.splice(next_target, tmp.instructions);
target=next_target;
recursion_set.erase(recursion_it);
}
void goto_inlinet::expand_function_call(
goto_programt &dest,
goto_programt::targett &target,
const exprt &lhs,
const symbol_exprt &function,
const exprt::operandst &arguments,
const exprt &constrain,
bool full)
{
// look it up
const irep_idt identifier=function.get_identifier();
// we ignore certain calls
if(identifier=="__CPROVER_cleanup" ||
identifier=="__CPROVER_set_must" ||
identifier=="__CPROVER_set_may" ||
identifier=="__CPROVER_clear_must" ||
identifier=="__CPROVER_clear_may" ||
identifier=="__CPROVER_cover")
{
target++;
return; // ignore
}
// see if we are already expanding it
if(recursion_set.find(identifier)!=recursion_set.end())
{
if(!full)
{
target++;
return; // simply ignore, we don't do full inlining, it's ok
}
// it's really recursive, and we need full inlining.
// Uh. Buh. Give up.
warning().source_location=function.find_source_location();
warning() << "recursion is ignored" << eom;
target->make_skip();
target++;
return;
}
goto_functionst::function_mapt::iterator m_it=
goto_functions.function_map.find(identifier);
if(m_it==goto_functions.function_map.end())
{
if(!full)
{
target++;
return; // simply ignore, we don't do full inlining, it's ok
}
error().source_location=function.find_source_location();
error() << "failed to find function `" << identifier << "'" << eom;
throw 0;
}
const goto_functionst::goto_functiont &f=m_it->second;
// see if we need to inline this
if(!full)
{
if(!f.body_available() ||
(!f.is_inlined() && f.body.instructions.size() > smallfunc_limit))
{
target++;
return;
}
}
if(f.body_available())
{
recursion_set.insert(identifier);
// first make sure that this one is already inlined
goto_inline_rec(m_it, full);
goto_programt tmp2;
tmp2.copy_from(f.body);
assert(tmp2.instructions.back().is_end_function());
tmp2.instructions.back().type=LOCATION;
replace_return(tmp2, lhs, constrain);
goto_programt tmp;
parameter_assignments(target->source_location, identifier, f.type, arguments, tmp);
tmp.destructive_append(tmp2);
parameter_destruction(target->source_location, identifier, f.type, tmp);
if(f.is_hidden())
{
source_locationt new_source_location=
function.find_source_location();
if(new_source_location.is_not_nil())
{
new_source_location.set_hide();
Forall_goto_program_instructions(it, tmp)
{
if(it->function==identifier)
{
// don't hide assignment to lhs
if(it->is_assign() && to_code_assign(it->code).lhs()==lhs)
{
}
else
{
replace_location(it->source_location, new_source_location);
replace_location(it->guard, new_source_location);
replace_location(it->code, new_source_location);
}
it->function=target->function;
}
}
}
void string_instrumentationt::do_strerror(
goto_programt &dest,
goto_programt::targett it,
code_function_callt &call)
{
if(call.lhs().is_nil())
{
it->make_skip();
return;
}
irep_idt identifier_buf="__strerror_buffer";
irep_idt identifier_size="__strerror_buffer_size";
if(symbol_table.symbols.find(identifier_buf)==symbol_table.symbols.end())
{
symbolt new_symbol_size;
new_symbol_size.base_name="__strerror_buffer_size";
new_symbol_size.pretty_name=new_symbol_size.base_name;
new_symbol_size.name=identifier_size;
new_symbol_size.mode=ID_C;
new_symbol_size.type=size_type();
new_symbol_size.is_state_var=true;
new_symbol_size.is_lvalue=true;
new_symbol_size.is_static_lifetime=true;
array_typet type;
type.subtype()=char_type();
type.size()=new_symbol_size.symbol_expr();
symbolt new_symbol_buf;
new_symbol_buf.mode=ID_C;
new_symbol_buf.type=type;
new_symbol_buf.is_state_var=true;
new_symbol_buf.is_lvalue=true;
new_symbol_buf.is_static_lifetime=true;
new_symbol_buf.base_name="__strerror_buffer";
new_symbol_buf.pretty_name=new_symbol_buf.base_name;
new_symbol_buf.name=new_symbol_buf.base_name;
symbol_table.move(new_symbol_buf);
symbol_table.move(new_symbol_size);
}
const symbolt &symbol_size=ns.lookup(identifier_size);
const symbolt &symbol_buf=ns.lookup(identifier_buf);
goto_programt tmp;
{
goto_programt::targett assignment1=tmp.add_instruction(ASSIGN);
exprt nondet_size=side_effect_expr_nondett(size_type());
assignment1->code=code_assignt(symbol_size.symbol_expr(), nondet_size);
assignment1->source_location=it->source_location;
goto_programt::targett assumption1=tmp.add_instruction();
assumption1->make_assumption(
binary_relation_exprt(
symbol_size.symbol_expr(),
ID_notequal,
from_integer(0, symbol_size.type)));
assumption1->source_location=it->source_location;
}
// return a pointer to some magic buffer
index_exprt index(
symbol_buf.symbol_expr(),
from_integer(0, index_type()),
char_type());
address_of_exprt ptr(index);
// make that zero-terminated
{
goto_programt::targett assignment2=tmp.add_instruction(ASSIGN);
assignment2->code=code_assignt(is_zero_string(ptr, true), true_exprt());
assignment2->source_location=it->source_location;
}
// assign address
{
goto_programt::targett assignment3=tmp.add_instruction(ASSIGN);
exprt rhs=ptr;
make_type(rhs, call.lhs().type());
assignment3->code=code_assignt(call.lhs(), rhs);
assignment3->source_location=it->source_location;
}
it->make_skip();
dest.insert_before_swap(it, tmp);
}