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Add CoW base to value-set #3053

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Add CoW base to value-set #3053

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48e1e6c
Value set: indirect values.find operations via a helper function
smowton Sep 26, 2018
7b5d5e5
Remove unused value_sett::do_free
smowton Sep 26, 2018
ca2a7b3
Value-set: add support for a base value-set
smowton Sep 26, 2018
e8015b8
Add unit test to check value-set behaviour in the presence of constants
smowton Apr 18, 2018
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35 changes: 20 additions & 15 deletions src/pointer-analysis/value_set.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,13 @@ bool value_sett::field_sensitive(
return ns.follow(type).id()==ID_struct;
}

const value_sett::entryt *value_sett::find_entry(const value_sett::idt &id)
const
{
auto found = values.find(id);
return found == values.end() ? nullptr : &found->second;
}

value_sett::entryt &value_sett::get_entry(
const entryt &e,
const typet &type,
Expand Down Expand Up @@ -429,31 +436,29 @@ void value_sett::get_value_set_rec(
expr_type.id()==ID_array)
{
// look it up
valuest::const_iterator v_it=
values.find(id2string(identifier)+suffix);
const entryt *entry =
find_entry(id2string(identifier) + suffix);

// try first component name as suffix if not yet found
if(v_it==values.end() &&
(expr_type.id()==ID_struct ||
expr_type.id()==ID_union))
if(!entry && (expr_type.id() == ID_struct || expr_type.id() == ID_union))
{
const struct_union_typet &struct_union_type=
to_struct_union_type(expr_type);

const irep_idt &first_component_name =
struct_union_type.components().front().get_name();

v_it = values.find(
entry = find_entry(
id2string(identifier) + "." + id2string(first_component_name) +
suffix);
}

// not found? try without suffix
if(v_it==values.end())
v_it=values.find(identifier);
if(!entry)
entry = find_entry(identifier);

if(v_it!=values.end())
make_union(dest, v_it->second.object_map);
if(entry)
make_union(dest, entry->object_map);
else
insert(dest, exprt(ID_unknown, original_type));
}
Expand Down Expand Up @@ -857,16 +862,16 @@ void value_sett::get_value_set_rec(
const std::string full_name=prefix+suffix;

// look it up
valuest::const_iterator v_it=values.find(full_name);
const entryt *entry = find_entry(full_name);

// not found? try without suffix
if(v_it==values.end())
v_it=values.find(prefix);
if(!entry)
entry = find_entry(prefix);

if(v_it==values.end())
if(!entry)
insert(dest, exprt(ID_unknown, original_type));
else
make_union(dest, v_it->second.object_map);
make_union(dest, entry->object_map);
}
else if(expr.id()==ID_byte_extract_little_endian ||
expr.id()==ID_byte_extract_big_endian)
Expand Down
9 changes: 9 additions & 0 deletions src/pointer-analysis/value_set.h
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Original file line number Diff line number Diff line change
Expand Up @@ -317,6 +317,15 @@ class value_sett
values.clear();
}

/// Finds an entry in this value-set. The interface differs from get_entry
/// because get_value_set_rec wants to check for a struct's first component
/// before stripping the suffix as is done in get_entry.
/// \param id: identifier to find.
/// \return a constant pointer to an entry if found, or null otherwise.
/// Note the pointer may be invalidated by insert operations, including
/// get_entry.
const entryt *find_entry(const idt &id) const;
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Would optionalt be a possibility?

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Contributor Author

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Personal preference: T * not optionalt<reference_wrapper<T>>

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What about optionalt<T *>? It would more clearly express the intent and remove the role of nullptr as a sentinel value that can accidentally be dereferenced.


/// Gets or inserts an entry in this value-set.
/// \param e: entry to find. Its `id` and `suffix` fields will be used
/// to find a corresponding entry; if a fresh entry is created its
Expand Down