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Jun 14, 2017
Merged

Code for Object.getClass in bytecode conversion #945

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e9e3989
Providing code for Object.getClass() in bytecode conversion
romainbrenguier May 13, 2017
db1cd5f
Cleaning the initialization of string expressions from constants
romainbrenguier May 13, 2017
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95 changes: 95 additions & 0 deletions src/java_bytecode/java_string_library_preprocess.cpp
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Expand Up @@ -1723,6 +1723,93 @@ codet java_string_library_preprocesst::make_string_to_char_array_code(

/*******************************************************************\

Function: java_string_library_preprocesst::make_object_get_class_code

Inputs:
type - type of the function called
loc - location in the source
symbol_table - the symbol table

Outputs: Code corresponding to
> Class class1;
> string_expr1 = substr(this->@class_identifier, 6)
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what does the constant 6 represent?

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This is to remove the "java::" prefix. (see the comment on line 1778 https://github.com/diffblue/cbmc/pull/945/files/556dc9a262b23686d07d9019f5d5f69bf8fee5ab#diff-333608a53b33706cdc28c1f3c1d0ca16R1778)
Maybe std::string("java::").length() would be more explicit...

> class1=Class.forName(string_expr1)
> return class1

Purpose: Used to provide our own implementation of the
java.lang.Object.getClass() function.

\*******************************************************************/

codet java_string_library_preprocesst::make_object_get_class_code(
const code_typet &type,
const source_locationt &loc,
symbol_tablet &symbol_table)
{
code_typet::parameterst params=type.parameters();
exprt this_obj=symbol_exprt(params[0].get_identifier(), params[0].type());
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does this work for static functions where no this parameter exists?

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No, this is really meant to be only used for implementing the Object.getClass() method which is not declared as static by Java.


// Code to be returned
code_blockt code;

// > Class class1;
pointer_typet class_type(symbol_table.lookup("java::java.lang.Class").type);
symbolt class1_sym=get_fresh_aux_symbol(
class_type, "class_symbol", "class_symbol", loc, ID_java, symbol_table);
symbol_exprt class1=class1_sym.symbol_expr();
code.add(code_declt(class1));

// class_identifier is this->@class_identifier
member_exprt class_identifier(
dereference_exprt(this_obj, this_obj.type().subtype()),
"@class_identifier",
string_typet());

// string_expr = cprover_string_literal(this->@class_identifier)
string_exprt string_expr=fresh_string_expr(loc, symbol_table, code);
code.add(
code_assign_function_to_string_expr(
string_expr,
ID_cprover_string_literal_func,
{class_identifier},
symbol_table));

// string_expr1 = substr(string_expr, 6)
// We do this to remove the "java::" prefix
string_exprt string_expr1=fresh_string_expr(loc, symbol_table, code);
code.add(
code_assign_function_to_string_expr(
string_expr1,
ID_cprover_string_substring_func,
{string_expr, from_integer(6, java_int_type())},
symbol_table));

// string1 = (String*) string_expr
pointer_typet string_ptr_type(
symbol_table.lookup("java::java.lang.String").type);
exprt string1=allocate_fresh_string(string_ptr_type, loc, symbol_table, code);
code.add(
code_assign_string_expr_to_new_java_string(
string1, string_expr1, loc, symbol_table));

// > class1 = Class.forName(string1)
code_function_callt fun_call;
fun_call.function()=symbol_exprt(
"java::java.lang.Class.forName:(Ljava/lang/String;)Ljava/lang/Class;");
fun_call.lhs()=class1;
fun_call.arguments().push_back(string1);
code_typet fun_type;
fun_type.return_type()=string1.type();
fun_call.function().type()=fun_type;
code.add(fun_call);

// > return class1;
code.add(code_returnt(class1));
return code;
}

/*******************************************************************\

Function: java_string_library_preprocesst::make_function_from_call

Inputs:
Expand Down Expand Up @@ -2545,4 +2632,12 @@ void java_string_library_preprocesst::initialize_conversion_table()
cprover_equivalent_to_java_string_returning_function
["java::java.lang.Integer.toString:(I)Ljava/lang/String;"]=
ID_cprover_string_of_int_func;
conversion_table
["java::java.lang.Object.getClass:()Ljava/lang/Class;"]=
std::bind(
&java_string_library_preprocesst::make_object_get_class_code,
this,
std::placeholders::_1,
std::placeholders::_2,
std::placeholders::_3);
}
5 changes: 5 additions & 0 deletions src/java_bytecode/java_string_library_preprocess.h
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Expand Up @@ -151,6 +151,11 @@ class java_string_library_preprocesst:public messaget
const source_locationt &loc,
symbol_tablet &symbol_table);

codet make_object_get_class_code(
const code_typet &type,
const source_locationt &loc,
symbol_tablet &symbol_table);

// Auxiliary functions
codet code_for_scientific_notation(
const exprt &arg,
Expand Down
50 changes: 4 additions & 46 deletions src/solvers/refinement/string_constraint_generator_constants.cpp
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Expand Up @@ -13,29 +13,6 @@ Author: Romain Brenguier, [email protected]

/*******************************************************************\

Function: string_constraint_generatort::extract_java_string

Inputs: a symbol expression representing a java literal

Outputs: a string constant

Purpose: extract java string from symbol expression when they are encoded
inside the symbol name

\*******************************************************************/

irep_idt string_constraint_generatort::extract_java_string(
const symbol_exprt &s)
{
std::string tmp=id2string(s.get_identifier());
std::string prefix("java::java.lang.String.Literal.");
assert(has_prefix(tmp, prefix));
std::string value=tmp.substr(prefix.length());
return irep_idt(value);
}

/*******************************************************************\

Function: string_constraint_generatort::add_axioms_for_constant

Inputs: a string constant
Expand Down Expand Up @@ -107,7 +84,9 @@ string_exprt string_constraint_generatort::add_axioms_for_empty_string(

Function: string_constraint_generatort::add_axioms_from_literal

Inputs: function application with an argument which is a string literal
Inputs:
f - function application with an argument which is a string literal
that is a constant with a string value.

Outputs: string expression

Expand All @@ -123,28 +102,7 @@ string_exprt string_constraint_generatort::add_axioms_from_literal(
assert(args.size()==1); // Bad args to string literal?

const exprt &arg=args[0];
irep_idt sval;

assert(arg.operands().size()==1);
if(arg.op0().operands().size()==2 &&
arg.op0().op0().id()==ID_string_constant)
{
// C string constant
const exprt &s=arg.op0().op0();
sval=to_string_constant(s).get_value();
}
else
{
// Java string constant
assert(false); // TODO: Check if used. On the contrary, discard else.
assert(arg.id()==ID_symbol);
const exprt &s=arg.op0();

// It seems the value of the string is lost,
// we need to recover it from the identifier
sval=extract_java_string(to_symbol_expr(s));
}

irep_idt sval=to_constant_expr(arg).get_value();
const refined_string_typet &ref_type=to_refined_string_type(f.type());
return add_axioms_for_constant(sval, ref_type);
}