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Avoid infinite recursion in has_subtype #2079

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Apr 17, 2018
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Avoid infinite recursion in has_subtype #2079

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49 changes: 29 additions & 20 deletions src/util/expr_util.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ Author: Daniel Kroening, [email protected]

#include "expr_util.h"

#include <unordered_set>
#include "expr.h"
#include "expr_iterator.h"
#include "fixedbv.h"
Expand Down Expand Up @@ -140,28 +141,36 @@ bool has_subtype(
const std::function<bool(const typet &)> &pred,
const namespacet &ns)
{
if(pred(type))
return true;
else if(type.id() == ID_symbol)
return has_subtype(ns.follow(type), pred, ns);
else if(type.id() == ID_c_enum_tag)
return has_subtype(ns.follow_tag(to_c_enum_tag_type(type)), pred, ns);
else if(type.id() == ID_struct || type.id() == ID_union)
{
const struct_union_typet &struct_union_type = to_struct_union_type(type);
std::vector<std::reference_wrapper<const typet>> stack;
std::unordered_set<typet, irep_hash> visited;

for(const auto &comp : struct_union_type.components())
if(has_subtype(comp.type(), pred, ns))
return true;
}
// do not look into pointer subtypes as this could cause unbounded recursion
else if(type.id() == ID_array || type.id() == ID_vector)
return has_subtype(type.subtype(), pred, ns);
else if(type.has_subtypes())
const auto push_if_not_visited = [&](const typet &t) {
if(visited.insert(t).second)
stack.emplace_back(t);
};

push_if_not_visited(type);
while(!stack.empty())
{
for(const auto &subtype : type.subtypes())
if(has_subtype(subtype, pred, ns))
return true;
const typet &top = stack.back().get();
stack.pop_back();

if(pred(top))
return true;
else if(top.id() == ID_symbol)
push_if_not_visited(ns.follow(top));
else if(top.id() == ID_c_enum_tag)
push_if_not_visited(ns.follow_tag(to_c_enum_tag_type(top)));
else if(top.id() == ID_struct || top.id() == ID_union)
{
for(const auto &comp : to_struct_union_type(top).components())
push_if_not_visited(comp.type());
}
else
{
for(const auto &subtype : top.subtypes())
push_if_not_visited(subtype);
}
}

return false;
Expand Down