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Common: Avoid std::function overhead in ScopeGuard
So far in all our uses of ScopeGuard, the type of the callable is usually just a lambda or a function pointer, so there is no need to rely on std::function's type erasure. While the cost of using std::function is probably negligible, it still causes some unnecessary overhead that can be avoided by making ScopeGuard a templated class. Thanks to class template argument deduction in C++17 most existing usages do not even need to be changed. See https://godbolt.org/z/KcoPni for a comparison between a ScopeGuard that uses std::function and one that doesn't
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@ -4,17 +4,15 @@
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#pragma once
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#include <functional>
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#include <optional>
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namespace Common
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{
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template <typename Callable>
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class ScopeGuard final
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{
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public:
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template <class Callable>
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ScopeGuard(Callable&& finalizer) : m_finalizer(std::forward<Callable>(finalizer))
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{
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}
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ScopeGuard(Callable&& finalizer) : m_finalizer(std::forward<Callable>(finalizer)) {}
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ScopeGuard(ScopeGuard&& other) : m_finalizer(std::move(other.m_finalizer))
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{
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@ -22,13 +20,13 @@ public:
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}
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~ScopeGuard() { Exit(); }
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void Dismiss() { m_finalizer = nullptr; }
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void Dismiss() { m_finalizer.reset(); }
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void Exit()
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{
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if (m_finalizer)
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{
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m_finalizer(); // must not throw
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m_finalizer = nullptr;
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(*m_finalizer)(); // must not throw
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m_finalizer.reset();
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}
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}
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@ -37,7 +35,7 @@ public:
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void operator=(const ScopeGuard&) = delete;
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private:
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std::function<void()> m_finalizer;
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std::optional<Callable> m_finalizer;
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};
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} // Namespace Common
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