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[interop] Cache subclass checks #116

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[interop] Cache subclass checks #116

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15 changes: 14 additions & 1 deletion src/interop/interop_wrapper.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -1132,7 +1132,20 @@ interop::TCppScope_t interop::GetBaseScope(TCppScope_t klass,

bool interop::IsSubclass(TCppScope_t derived, TCppScope_t base) {
std::lock_guard<std::recursive_mutex> Lock(InterOpMutex);
return Cpp::IsSubclass(derived, base);
// Checked on every method call that receives 'self' as its first argument
// (e.g. from pythonizations and protocol slots), so memoize per class
// pair. A class that is still incomplete can gain bases once its
// definition is loaded, so a negative answer is only cached for complete
// classes.
static std::map<std::pair<const void*, const void*>, bool> s_subclass_cache;

@vgvassilev vgvassilev Sep 27, 2026

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The challenge with these cases is error recovery and code reloading/undo. I think this is fine but nominally we should have that in CppInterOp which also should know better when to invalidate these caches. Can we track this in an issue somewhere?

const auto cacheKey = std::make_pair(derived.data, base.data);
auto cached = s_subclass_cache.find(cacheKey);
if (cached != s_subclass_cache.end())
return cached->second;
bool result = Cpp::IsSubclass(derived, base);
if (result || (Cpp::IsComplete(derived) && Cpp::IsComplete(base)))

@vgvassilev vgvassilev Sep 27, 2026

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Here IsComplete is only expensive the first time for ROOT then should be cheap. Is that not the case?

s_subclass_cache.emplace(cacheKey, result);
return result;
}

static std::set<std::string> gSmartPtrTypes = {
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