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add parameter for depth of recursive objects #567

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2 changes: 2 additions & 0 deletions src/cbmc/cbmc_parse_options.cpp
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Expand Up @@ -1156,6 +1156,8 @@ void cbmc_parse_optionst::help()
" --classpath dir/jar set the classpath\n"
" --main-class class-name set the name of the main class\n"
// NOLINTNEXTLINE(whitespace/line_length)
"--java-max-recursion-depth max recursion depth for nondet init of recursive objects\n"
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While I do accept that the initialisation code currently exists for Java only: I don't think this command-line option should remain as specific. Furthermore the option name suggests that functional recursion is limited, whereas this is all about object initialisation. How about: "recursive-object-bound"?

// NOLINTNEXTLINE(whitespace/line_length)
" --java-max-vla-length limit the length of user-code-created arrays\n"
// NOLINTNEXTLINE(whitespace/line_length)
" --java-cp-include-files regexp or JSON list of files to load (with '@' prefix)\n"
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1 change: 1 addition & 0 deletions src/cbmc/cbmc_parse_options.h
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Expand Up @@ -56,6 +56,7 @@ class optionst;
"(graphml-witness):" \
"(java-max-vla-length):(java-unwind-enum-static)" \
"(java-cp-include-files):" \
"(java-max-recursion-depth):" \
"(localize-faults)(localize-faults-method):" \
"(lazy-methods)" \
"(fixedbv)(floatbv)(all-claims)(all-properties)" // legacy, and will eventually disappear // NOLINT(whitespace/line_length)
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6 changes: 5 additions & 1 deletion src/java_bytecode/java_bytecode_language.cpp
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Expand Up @@ -48,6 +48,9 @@ void java_bytecode_languaget::get_language_options(const cmdlinet &cmd)
if(cmd.isset("java-max-input-array-length"))
max_nondet_array_length=
std::stoi(cmd.get_value("java-max-input-array-length"));
if(cmd.isset("java-max-recursion-depth"))
max_recursion_depth=
std::stoi(cmd.get_value("java-max-recursion-depth"));
if(cmd.isset("java-max-vla-length"))
max_user_array_length=std::stoi(cmd.get_value("java-max-vla-length"));
if(cmd.isset("lazy-methods-context-sensitive"))
Expand Down Expand Up @@ -791,7 +794,8 @@ bool java_bytecode_languaget::final(symbol_tablet &symbol_table)
main_class,
get_message_handler(),
assume_inputs_non_null,
max_nondet_array_length));
max_nondet_array_length,
max_recursion_depth));
}

/*******************************************************************\
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4 changes: 3 additions & 1 deletion src/java_bytecode/java_bytecode_language.h
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Expand Up @@ -56,7 +56,8 @@ class java_bytecode_languaget:public languaget
virtual ~java_bytecode_languaget();
java_bytecode_languaget():
max_nondet_array_length(MAX_NONDET_ARRAY_LENGTH_DEFAULT),
max_user_array_length(0)
max_user_array_length(0),
max_recursion_depth(0)
{}

bool from_expr(
Expand Down Expand Up @@ -106,6 +107,7 @@ class java_bytecode_languaget:public languaget
lazy_methods_modet lazy_methods_mode;
bool string_refinement_enabled;
std::string java_cp_include_files;
size_t max_recursion_depth; // maximal depth for recursive objects
};

languaget *new_java_bytecode_language();
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15 changes: 11 additions & 4 deletions src/java_bytecode/java_entry_point.cpp
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Expand Up @@ -102,7 +102,8 @@ bool java_static_lifetime_init(
const source_locationt &source_location,
message_handlert &message_handler,
bool assume_init_pointers_not_null,
unsigned max_nondet_array_length)
size_t max_nondet_array_length,
size_t max_recursive_depth)
{
symbolt &initialize_symbol=symbol_table.lookup(INITIALIZE);
code_blockt &code_block=to_code_block(to_code(initialize_symbol.value));
Expand Down Expand Up @@ -141,6 +142,7 @@ bool java_static_lifetime_init(
allow_null,
symbol_table,
max_nondet_array_length,
max_recursive_depth,
source_location,
message_handler);
code_assignt assignment(sym.symbol_expr(), newsym);
Expand Down Expand Up @@ -194,7 +196,8 @@ exprt::operandst java_build_arguments(
code_blockt &init_code,
symbol_tablet &symbol_table,
bool assume_init_pointers_not_null,
unsigned max_nondet_array_length,
size_t max_nondet_array_length,
size_t max_recursive_depth,
message_handlert &message_handler)
{
const code_typet::parameterst &parameters=
Expand Down Expand Up @@ -233,6 +236,7 @@ exprt::operandst java_build_arguments(
allow_null,
symbol_table,
max_nondet_array_length,
max_recursive_depth,
function.location,
message_handler);

Expand Down Expand Up @@ -517,7 +521,8 @@ bool java_entry_point(
const irep_idt &main_class,
message_handlert &message_handler,
bool assume_init_pointers_not_null,
size_t max_nondet_array_length)
size_t max_nondet_array_length,
size_t max_recursive_depth)
{
// check if the entry point is already there
if(symbol_table.symbols.find(goto_functionst::entry_point())!=
Expand All @@ -541,7 +546,8 @@ bool java_entry_point(
symbol.location,
message_handler,
assume_init_pointers_not_null,
max_nondet_array_length))
max_nondet_array_length,
max_recursive_depth))
return true;

code_blockt init_code;
Expand Down Expand Up @@ -598,6 +604,7 @@ bool java_entry_point(
symbol_table,
assume_init_pointers_not_null,
max_nondet_array_length,
max_recursive_depth,
message_handler);
call_main.arguments()=main_arguments;

Expand Down
3 changes: 2 additions & 1 deletion src/java_bytecode/java_entry_point.h
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Expand Up @@ -16,7 +16,8 @@ bool java_entry_point(
const irep_idt &main_class,
class message_handlert &message_handler,
bool assume_init_pointers_not_null,
size_t max_nondet_array_length);
size_t max_nondet_array_length,
size_t max_recursive_depth);

typedef struct
{
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38 changes: 25 additions & 13 deletions src/java_bytecode/java_object_factory.cpp
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Expand Up @@ -42,6 +42,8 @@ class java_object_factoryt:public messaget
std::set<irep_idt> recursion_set;
bool assume_non_null;
size_t max_nondet_array_length;
size_t recursion_depth;
size_t max_recursion_depth;
symbol_tablet &symbol_table;
message_handlert &message_handler;
namespacet ns;
Expand All @@ -51,11 +53,14 @@ class java_object_factoryt:public messaget
code_blockt &_init_code,
bool _assume_non_null,
size_t _max_nondet_array_length,
size_t _max_recursion_depth,
symbol_tablet &_symbol_table,
message_handlert &_message_handler):
init_code(_init_code),
assume_non_null(_assume_non_null),
max_nondet_array_length(_max_nondet_array_length),
recursion_depth(0),
max_recursion_depth(_max_recursion_depth),
symbol_table(_symbol_table),
message_handler(_message_handler),
ns(_symbol_table)
Expand Down Expand Up @@ -189,20 +194,23 @@ void java_object_factoryt::gen_nondet_init(
{
const struct_typet &struct_type=to_struct_type(subtype);
const irep_idt struct_tag=struct_type.get_tag();
// set to null if found in recursion set and not a sub-type
if(recursion_set.find(struct_tag)!=recursion_set.end() &&
struct_tag==class_identifier)
// set to null if found in recursion set and recursion depth allows it
if(recursion_set.find(struct_tag)!=recursion_set.end())
{
// make null
null_pointer_exprt null_pointer_expr(pointer_type);
code_assignt code(expr, null_pointer_expr);
code.add_source_location()=loc;
init_code.copy_to_operands(code);

return;
if(recursion_depth<max_recursion_depth)
recursion_depth++;
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Isn't this going to count the total number of recursive steps, across multiple "branches" of the data structures? For instance, for mutual recursion, the number of objects of a type X would actually just be max_recursion_depth/2.

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@mgudemann, what is the intended semantics of the parameter? I agree with @tautschnig that the current solution is rather unintuitive from the user's perspective.

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There is a problem with null initialization of objects. In the original implementation, a recursion set was used that would in an object hierarchy prevent instantiation of object types already seen. There were cases where this was problematic, if an object contained a recursive instantation, effectively this lead to a null value and due to various options (--assertions-as-assumptions etc.) created an ASSUME non null for that exact member, leading to inconsistent model.

The idea of this parameter was to create a solution between using exclusively the recursion set and not using it at all, i.e., having a bounded initialization of hierarchical objects.

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@tautschnig tautschnig Mar 21, 2017 •
edited
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Shouldn't the solution be passing the recursion_depth as a parameter? Decrement (or increment) it on each recursive call, and check for 0 (respectively a chosen maximum). Yes, you need the recursion set to detect the fact that you are doing a recursive step, but counters need to be branch-specific, not global across the structure.

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you are perfectly right with this

else
{
recursion_depth=0;
// make null
null_pointer_exprt null_pointer_expr(pointer_type);
code_assignt code(expr, null_pointer_expr);
code.add_source_location()=loc;
init_code.copy_to_operands(code);
return;
}
}
}

code_labelt set_null_label;
code_labelt init_done_label;

Expand Down Expand Up @@ -483,12 +491,14 @@ void gen_nondet_init(
bool create_dyn_objs,
bool assume_non_null,
message_handlert &message_handler,
size_t max_nondet_array_length)
size_t max_nondet_array_length,
size_t max_recursion_depth)
{
java_object_factoryt state(
init_code,
assume_non_null,
max_nondet_array_length,
max_recursion_depth,
symbol_table,
message_handler);
state.gen_nondet_init(
Expand Down Expand Up @@ -567,6 +577,7 @@ exprt object_factory(
bool allow_null,
symbol_tablet &symbol_table,
size_t max_nondet_array_length,
size_t max_recursion_depth,
const source_locationt &loc,
message_handlert &message_handler)
{
Expand All @@ -588,7 +599,8 @@ exprt object_factory(
false,
!allow_null,
message_handler,
max_nondet_array_length);
max_nondet_array_length,
max_recursion_depth);

return object;
}
Expand Down
4 changes: 3 additions & 1 deletion src/java_bytecode/java_object_factory.h
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Expand Up @@ -19,6 +19,7 @@ exprt object_factory(
bool allow_null,
symbol_tablet &symbol_table,
size_t max_nondet_array_length,
size_t max_recursion_depth,
const source_locationt &,
message_handlert &message_handler);

Expand All @@ -31,7 +32,8 @@ void gen_nondet_init(
bool create_dynamic_objects,
bool assume_non_null,
message_handlert &message_handler,
size_t max_nondet_array_length=5);
size_t max_nondet_array_length,
size_t max_recursion_depth);


exprt get_nondet_bool(const typet &);
Expand Down