masaori335 commented on a change in pull request #6996:
URL: https://github.com/apache/trafficserver/pull/6996#discussion_r453377616
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File path: iocore/eventsystem/I_Continuation.h
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@@ -63,6 +63,26 @@ extern EThread *this_event_thread();
typedef int (Continuation::*ContinuationHandler)(int event, void *data);
+// Convert event handler pointer fp to type ContinuationHandler, but with a
compiler error if class C is not
+// derived from the class Continuation.
Review comment:
Can we check this at compile time & avoid casting twice like this?
```
template <class C, typename T>
constexpr ContinuationHandler
continuation_handler_void_ptr(int (C::*fp)(int, T *))
{
static_assert(std::is_base_of<Continuation, C> && std::is_convertible<C,
Continuation>);
return reinterpret_cast<fp>;
}
```
BTW, we can check this clearly with the c++20 concept
```
template <class C, typename T>
requires std::derived_from(C, Continuation)
constexpr ContinuationHandler
continuation_handler_void_ptr(int (C::*fp)(int, T *))
{
```
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