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[SV-COMP'18 7/19] Ensure that local declarations do not introduce spurious dead warnings #1996

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[SV-COMP'18 7/19] Ensure that local declarations do not introduce spurious dead warnings #1996

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15 changes: 15 additions & 0 deletions regression/cbmc/Local_out_of_scope4/main.c
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Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
int main()
{
int *p = 0;

for(int i = 0; i < 3; ++i)
{
{
int x = 42;
p = &x;
*p = 1;
}
}

return 0;
}
8 changes: 8 additions & 0 deletions regression/cbmc/Local_out_of_scope4/test.desc
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@@ -0,0 +1,8 @@
CORE
main.c
--pointer-check
^EXIT=0$
^SIGNAL=0$
^VERIFICATION SUCCESSFUL$
--
^warning: ignoring
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Add an extra no-match line for the particular warning you were seeing?

28 changes: 28 additions & 0 deletions src/analyses/goto_check.cpp
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Expand Up @@ -1666,6 +1666,34 @@ void goto_checkt::goto_check(
}
}
}
else if(i.is_decl())
{
if(enable_pointer_check)
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I am unfamiliar with this code so non-blocking (I don't understand why dead statements need this instrumentation), but some documentation of why a deceleration statement needs to be instrumented when enable_pointer_check is on would be appreciated

{
assert(i.code.operands().size()==1);
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INVARIANT here?

const symbol_exprt &variable=to_symbol_expr(i.code.op0());

// is it dirty?
if(local_bitvector_analysis->dirty(variable))
{
// reset the dead marker
goto_programt::targett t=new_code.add_instruction(ASSIGN);
exprt address_of_expr=address_of_exprt(variable);
exprt lhs=ns.lookup(CPROVER_PREFIX "dead_object").symbol_expr();
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If "dead_object" is a magic string, is it already defined somewhere else? (A quick search of the code says no - it'd be nice to pull it out rather than introduce another duplication of it)

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Ignorant of this code, is this somehow the point where the variable that's declared goes out of scope? If you do pull out the "dead_object" string, it'd be great to document there what this variable is.

if(!base_type_eq(lhs.type(), address_of_expr.type(), ns))
address_of_expr.make_typecast(lhs.type());
exprt rhs=
if_exprt(
equal_exprt(lhs, address_of_expr),
null_pointer_exprt(to_pointer_type(address_of_expr.type())),
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might be clearer to use lhs.type() (since either equal or typecast and therefore equal?)

lhs,
lhs.type());
t->source_location=i.source_location;
t->code=code_assignt(lhs, rhs);
t->code.add_source_location()=i.source_location;
}
}
}
else if(i.is_end_function())
{
if(i.function==goto_functionst::entry_point() &&
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7 changes: 2 additions & 5 deletions src/goto-symex/symex_decl.cpp
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Expand Up @@ -72,11 +72,8 @@ void goto_symext::symex_decl(statet &state, const symbol_exprt &expr)
state.propagation.remove(l1_identifier);

// L2 renaming
// inlining may yield multiple declarations of the same identifier
// within the same L1 context
if(state.level2.current_names.find(l1_identifier)==
state.level2.current_names.end())
state.level2.current_names[l1_identifier]=std::make_pair(ssa, 0);
state.level2.current_names.insert(
std::make_pair(l1_identifier, std::make_pair(ssa, 0)));
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Nitpick: might as well emplace, rather than make pair then insert

state.level2.increase_counter(l1_identifier);
const bool record_events=state.record_events;
state.record_events=false;
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