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Stop asserting positive array size #4928

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Stop asserting positive array size #4928

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f585e60
Stop asserting positive array size
petr-bauch Jul 22, 2019
30923ab
Also skip flattening zero-sized arrays
petr-bauch Jul 30, 2019
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13 changes: 13 additions & 0 deletions regression/cbmc/Struct_Hack_Initialization/main.c
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Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
#include <assert.h>

typedef struct stritem
{
unsigned nkey;
unsigned cas[];
} item;

int foo(item *it)
{
assert(it->cas[0] == 0);
return 0;
}
13 changes: 13 additions & 0 deletions regression/cbmc/Struct_Hack_Initialization/test.desc
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Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
CORE
main.c
--function foo --bounds-check --pointer-check
^\[foo.assertion.1\] line \d+ assertion it->cas\[0\] == 0: FAILURE$
^\[foo.array_bounds.3\] line \d+ array.cas upper bound in it->cas\[\(.*\)0\]: FAILURE$
^\[foo.array_bounds.2\] line \d+ array.cas dynamic object upper bound in it->cas\[\(.*\)0\]: FAILURE$
^\[foo.pointer_dereference.2\] line \d+ dereference failure: pointer invalid in it->cas: SUCCESS$
^\[foo.pointer_dereference.6\] line \d+ dereference failure: pointer outside object bounds in it->cas: FAILURE$
^EXIT=10$
^SIGNAL=0$
^VERIFICATION FAILED$
--
^warning: ignoring
1 change: 0 additions & 1 deletion src/ansi-c/c_nondet_symbol_factory.cpp
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Expand Up @@ -163,7 +163,6 @@ void symbol_factoryt::gen_nondet_array_init(
const auto &size = array_type.size();
PRECONDITION(size.id() == ID_constant);
auto const array_size = numeric_cast_v<size_t>(to_constant_expr(size));
DATA_INVARIANT(array_size > 0, "Arrays should have positive size");
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I wasn't properly taking this situation into account when writing this.

for(size_t index = 0; index < array_size; ++index)
{
gen_nondet_init(
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15 changes: 13 additions & 2 deletions src/solvers/smt2/smt2_conv.cpp
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Expand Up @@ -2672,7 +2672,14 @@ void smt2_convt::convert_struct(const struct_exprt &expr)

// may need to flatten array-theory arrays in there
if(op.type().id() == ID_array)
flatten_array(op);
{
const array_typet &array_type = to_array_type(op.type());
const auto &size_expr = array_type.size();
CHECK_RETURN(size_expr.id() == ID_constant);

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This prevents using arrays with variable size.

if(numeric_cast_v<mp_integer>(to_constant_expr(size_expr)) != 0)
flatten_array(op);
}
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In principle, this check would now need to be done in front of every call to flatten array, to make that a precondition of that function.
I think this is the wrong approach. I would let flatten_array handle this case.

else
convert_expr(op);

Expand Down Expand Up @@ -4526,7 +4533,11 @@ void smt2_convt::convert_type(const typet &type)
{
if(use_datatypes)
{
out << datatype_map.at(type);
const typet &struct_type = type.id() == ID_struct_tag
? ns.follow_tag(to_struct_tag_type(type))
: type;
CHECK_RETURN(datatype_map.count(struct_type) > 0);
out << datatype_map.at(struct_type);
}
else
{
Expand Down