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Zero-initialize object factory structs #2123

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May 8, 2018
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Zero-initialize object factory structs #2123

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52 changes: 34 additions & 18 deletions src/java_bytecode/java_object_factory.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -12,8 +12,11 @@ Author: Daniel Kroening, kroening@kroening.com
#include <util/nondet_bool.h>
#include <util/pointer_offset_size.h>

#include <goto-programs/class_identifier.h>
#include <goto-programs/goto_functions.h>

#include <linking/zero_initializer.h>

#include "generic_parameter_specialization_map_keys.h"
#include "java_root_class.h"

Expand Down Expand Up @@ -1027,8 +1030,35 @@ void java_object_factoryt::gen_nondet_struct_init(

const componentst &components=struct_type.components();

if(!is_sub)
class_identifier=struct_tag;
// Should we write the whole object?
// * Not if this is a sub-structure (a superclass object), as our caller will
// have done this already
// * Not if the object has already been initialised by our caller, in whic
// case they will set `skip_classid`
// * Not if we're re-initializing an existing object (i.e. update_in_place)

if(!is_sub &&
!skip_classid &&
update_in_place != update_in_placet::MUST_UPDATE_IN_PLACE)
{
class_identifier = struct_tag;

// Add an initial all-zero write. Most of the fields of this will be
// overwritten, but it helps to have a whole-structure write that analysis
// passes can easily recognise leaves no uninitialised state behind.

// This code mirrors the `remove_java_new` pass:
null_message_handlert nullout;
exprt zero_object=
zero_initializer(
struct_type, source_locationt(), ns, nullout);
irep_idt qualified_clsid = "java::" + id2string(class_identifier);
set_class_identifier(
to_struct_expr(zero_object), ns, symbol_typet(qualified_clsid));

assignments.copy_to_operands(
code_assignt(expr, zero_object));
}

for(const auto &component : components)
{
Expand All @@ -1039,25 +1069,11 @@ void java_object_factoryt::gen_nondet_struct_init(

if(name=="@class_identifier")
{
if(update_in_place==update_in_placet::MUST_UPDATE_IN_PLACE)
continue;

if(skip_classid)
continue;

irep_idt qualified_clsid = "java::" + id2string(class_identifier);
constant_exprt ci(qualified_clsid, string_typet());
code_assignt code(me, ci);
code.add_source_location()=loc;
assignments.copy_to_operands(code);
continue;
}
else if(name=="@lock")
{
if(update_in_place==update_in_placet::MUST_UPDATE_IN_PLACE)
continue;
code_assignt code(me, from_integer(0, me.type()));
code.add_source_location()=loc;
assignments.copy_to_operands(code);
continue;
}
else
{
Expand Down