adamdebreceni commented on a change in pull request #887:
URL: https://github.com/apache/nifi-minifi-cpp/pull/887#discussion_r481949364
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File path: libminifi/include/utils/GeneralUtils.h
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@@ -68,6 +68,21 @@ using void_t = void;
using std::void_t;
#endif /* < C++17 */
+namespace internal {
+
+struct safe_enable_shared_from_this_base :
std::enable_shared_from_this<safe_enable_shared_from_this_base> {
Review comment:
we have to have a single class template instance
`std::enable_shared_from_this<T>` for some type `T`, so that when we inherit
from it virtually multiple times, we get the same `std::weak_ptr` instance
for example in the following, if `U` depends on `T` we don't inherit from
the same `enable_shared_from_this` class instance, but `U` also must be a base
class of `T`, moreover it has to be polymorphic to `dynamic_cast` it to the
derived type (that is why it has a virtual destructor)
```
template<typename T>
struct safe_enable_shared_from_this : virtual
std::enable_shared_from_this<U> {...}
struct A : safe_enable_shared_from_this<A> {...}
struct B: A, safe_enable_shared_from_this<B>{...}
```
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