Summary

In DebugInfoStore::Get(), ParseModuleDebugInfo(moduleId) inserts into the _modulesInfo unordered_map via _modulesInfo[moduleId], which may trigger a rehash that invalidates all iterators. The old code reused a stale iterator obtained before the insertion — undefined behavior per the C++ standard. Fix: re-acquire the iterator via find() after insertion, and simplify the now-unnecessary ternary.

Proof of UB

Per cppreference unordered_map::insert:

If rehashing occurs (due to the insertion), all iterators are invalidated. Otherwise iterators are not invalidated.

And unordered_map::operator[] performs an insert if the key doesn't exist, with the same invalidation rules.

In the original code:

auto it = _modulesInfo.find(moduleId);           // iterator obtained
if (it == _modulesInfo.cend())
{
    ParseModuleDebugInfo(moduleId);               // inserts via _modulesInfo[moduleId]
}
ModuleDebugInfo& info = (it == _modulesInfo.cend()) ? _modulesInfo[moduleId] : it->second;
                         // ^^^ stale iterator compared after insertion — UB if rehash occurred

Severity: Low. In practice this bug does not cause any observable problem. libstdc++ and libc++ use a node-based unordered_map implementation where rehash re-links nodes into new buckets but never frees or moves the nodes themselves. Stale iterators still point to valid memory and the end() sentinel comparison happens to produce correct results. The fix is still warranted to eliminate the UB — a different stdlib implementation or future change could break this.

Changes

• profiler/src/ProfilerEngine/Datadog.Profiler.Native/DebugInfoStore.cpp: After ParseModuleDebugInfo() inserts into the map, re-acquire the iterator with it = _modulesInfo.find(moduleId). Remove the ternary that compared the stale iterator.

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